Demetrio Boltovskoy (Editor). 1981. Atlas del Zooplancton del Atlántico Sudoccidental y métodos de trabajo con el zooplancton marino. Publicación Especial del Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina, pp. I-XXX + 1-938. 1981. Authors: A. Alvariño (USA), M.V. Angel (UK), T. Antezana (Chile), E. Balech (Argentina), J.R. Beers (USA), T.S.K. Björnberg (Brazil), D. Boltovskoy (Argentina), E. Boltovskoy (Argentina), E. Boschi (Argentina), E. Brinton (USA), F. Campaner (Brazil), L.R.A. Capurro (México), J.D. de Ciechomski (Argentina), G.B. Esnal (Argentina), S. Frontier (France), S.S. Jankilevich (Argentina), F.C. Ramírez (Argentina), H.F. Steedman (UK), S. Souto (USA), C. Stöp-Bowitz (Norway), S. Van der Spoel (Holland), M.O. Zamponi (Argentina).

Part I. Methods in marine zooplankton research.

Collection of in situ information. Collection of plankton samples (nets; automatic, continuous and highspeed samplers; pump sampling; bottle sampling). Related problems (shape of sampler, the gauze, dodging, estimation of volume of water filtered, estimation of depth of towing, towing speed, sampling design). Further treatement of the samples (narcotization, relaxation and dying; fixation and preservation, biomass determination; subsampling; fractioning, sorting and picking; counting and data analysis). Marine zooplankton cultivation. General handling of data, literature and material.

Part II. The Southwestern Atlantic.

Physical features of the SW Atlantic. Water masses of the SW Atlantic. Biological features of the SW Atlantic.

Part III. Zooplankton of the SW Atlantic. Radiolaria. Foraminifera. Tintinnina. Siphonophorae. Hydromedusae. Polychaeta Pteropoda. Cladocera. Ostracoda. Copepoda. Euphausiacea. Decapoda larvae. Chaetognatha. Thaliacea: Salpidae. Appendicularia. Ichtyoplankton.

Each one of the chapters of Part III includes a brief account on the biology, reproduction, general distribution, importance and applications, trophic relationships and methods of research of the particular group. Detailed information is given on the distribution of the species in the Southwestern Atlantic (0 to 60°S and 70 to 25°W), including crytical analysis of the previous records in the area under study. The last section of each chapter is devoted to the identification of the species known to occur in the Southwestern Atlantic, including descriptions, keys and illustrations of all the taxa.

D. Boltovskoy (Editor). 1999. South Atlantic Zooplankton. Backhuys Publishers, Leiden, pp. i-xvi + 1-1706. (ISBN 90-5782-035-8). Authors: Viviana Alder (Argentina), Martin Angel (UK), Renate Bernstein (USA), Demetrio Boltovskoy (Argentina), Jean Bouillon (Belgium), Jean-Paul Casanova (France), Paul Cornelius (UK), José Dadon (Argentina), Cristina Daponte (Argentina), Graciela Esnal (Argentina), María Ana Fernández Alamo (México), Mark Gibbons (South Africa), Ray Gibson (UK), Janet Grieve (New Zealand), Christoph Hemleben (Germany), Sylvia Kemmle-Mücke (Germany), Stanley A. Kling (USA), Elena Markhaseva (Russia), Yasunobu Matsuura (Brazil), Fernando L. Medina Mantelatto (Brazil), Hermes Mianzan (Argentina), Masaaki Murano (Japan), Kir Nesis (Russia), María Pilar Olivar (Spain), Takashi Onbé (Japan), Ray Peterson (USA), Wolfgang Petz (Austria), Gerhard Pohle (Canada), Gotthard Richter (Germany), Carlos da Rocha (Brazil), Russ Schiel (Australia), Roger Seapy (USA), Vassily Spiridonov (Russia), Geraint Tarling (UK), Eric Thuesen (USA), Siebrecht Van der Spoel (Holland), Georgy Vinogradov (Russia).

Foreword [pp. vii-viii]
Authors [pp. ix-xii]
General biological features of the South Atlantic (Demetrio Boltovskoy, Mark Gibbons, Lawrence Hutchings and Denis Binet) [pp. 1-42]
Foraminifera (Sylvia Kemle-von Mücke and Christoph Hemleben) [pp. 43-73]
Acantharia (Renate Bernstein, Stanley A. Kling and Demetrio Boltovskoy) [pp. 75-147]
Radiolaria Polycystina (Demetrio Boltovskoy) [pp. 149-212]
Radiolaria Phaeodaria (Stanley A. Kling and Demetrio Boltovskoy) [pp. 213-264]
Ciliophora (Wolfgang Petz) [pp. 265-319]
Tintinnoinea (Viviana A. Alder) [pp. 321-384]
Hydromedusae (Jean Bouillon) [pp. 385-465]
Siphonophorae (Phil Pugh) [pp. 467-511]
Cubozomedusae and Scyphomedusae (Hermes W. Mianzan and Paul Cornelius) [pp. 513-559]
Ctenophora (Hermes W. Mianzan) [pp. 561-573]
Nemertina (Ray Gibson) [pp. 575-593]
Polychaeta (Erik Thuesen and María Ana Fernández Álamo) [pp. 595-619]
Heteropoda (Gotthard Richter and Roger R. Seapy) [pp. 621-647]
Pteropoda (Siebrecht van der Spoel and José R. Dadon) [pp. 649-706]
Cephalopoda (Kir N. Nesis) [pp. 707-795]
Ctenopoda and Onychopoda (=Cladocera) (Takashi Onbé) [pp. 797-813]
Ostracoda (Martin V. Angel) [pp. 815-868]
Copepoda (Janet M. Bradford-Grieve, Elena L. Markhaseva, Carlos E. F. Rocha and Bernardo Abiahy) [pp. 869-1098]
Mysidacea (Masaaki Murano) [pp. 1099-1140]
Amphipoda (Georgyi Vinogradov) [pp. 1141-1240]
Euphausiacea (Mark J. Gibbons, Vassily A. Spiridonov and Geraint A. Tarling) [pp. 1241-1279]
Larval Decapoda (Brachyura) (Gerhard Pohle, Adilson Fransozo, María L. Negreiros-Fransozo and Fernando L. Medina Mantelatto) [pp. 1281-1351]
Chaetognatha (Jean-Paul Casanova) [pp. 1353-1374]
Appendicularia (Graciela B. Esnal) [pp. 1375-1399]
Pyrosomatida (Graciela B. Esnal) [pp. 1401-1408]
Doliolida (Graciela B. Esnal and María C. Daponte) [pp. 1409-1421]
Salpida (Graciela B. Esnal and María C. Daponte) [pp. 1423-1444]
Fish larvae (Yasunobu Matsuura and María Pilar Olivar) [pp. 1445-1496]
Bibliography [pp. 1497-1625]
Taxonomic index [pp. 1627-1705]


Boltovskoy, D. 1971. Pterópodos thesosomados del Atlántico Sudoccidental. Malacologia, 11(1):121-140.

The thecosomatous pteropods in fiftysix plankton samples (28 horizontal surface and 28 vertical, generally 2000 m, hauls) were studied from the systematical and distributional points of view. The zone of eolleetion is described as follows: North 36°9'S, South: 38°05'S, East: 42°58'W and West: 57°29'W. Nine speeies were found: Limacina helicina, L. retroversa, L. inflata, L. bulimoides, Clio pyramidata, Cl. cuspidata, Creseis sp., Diacria sp. and Cavolinia sp. This is one of the first thorough studies on the pteropods of this part of the South Atlantie Ocean. The hydrology of surface waters is discussed on the basis of the results obtained and the author arrives at the conclusion that the 4 water masses known for this area can be perfectly delimited and thus these mollusks are excellent hydrological indicators.

Boltovskoy, D. 1974. Study of surface shell structures in Thecosomata (Pteropoda: Mollusca), by means of scanning electron microscopy. Marine Biology, 27(2):165-172.

The shell ornamentation of 6 species of Limacinidae and 2 species of Peraclididae has been studied by means of scanning electron microscopy. The author analyzes the phylogenetic relationships between the species considered and the morphologic resemblance with protoconchs of other Gastropoda. The function of some of the features observed is considered, and the relationship between adult and larval environments and shell formation discussed. Pteropoda do not exhibit conspicuous differences between veliger and adult shells, but there is quite an important difference between the protoconch and the rest of the shell, the former being very similar in several Gastropoda. The division of the genus Limacina into 3 subgenera, as proposed by Van der Spoel (1967), is also partially confirmed by the present study.

Boltovskoy, D. 1975. Some biometrical, ecological, morphological and distributional aspects of chaetognatha. Hydrobiologia, 46(4):515-534.

The study of the Chaetognatha picked out from 21 plankton samples taken along the Argentinian, Uruguayan and Brazilian coasts, revealed the presence of the following species: Krohnitta pacifica, K. subtilis, Pterosagitta draco, Sagitta bipunctata, S. enflata, S.friderici, S. hexaptera, S. hispida, S. Iyra, S. maxima, S. minima, S. planctonis, S. serratodentata, S. tenuis and S. sp. A. All specimens were measured and a complete biometrical table is included. Based on the Chaetognatha and the Thecosomata fauna analyzed by means of the Sorensen's index of similarity between samples, the area is divided into four zones with different hydrological characteristics. There is a distinct relationship between the total length of fully mature specimens and latitude. Based on diagrams, an interspecific competition between 5. enflata and S. tenuis is suggested. The geographic distribution of K. subtilis and S. planctonis is enlarged.

Boltovskoy, D. 1975. Ecological aspects of zooplankton (Foraminifera, Pteropoda and Chaetognatha) of the Southwestern Atlantic Ocean. The Veliger, 18(2):203-216.

1. Some pteropod species (Limacina helicina) and Chaetognatha (Eukrohnia hamata, Sagitta serratodentata and S. tasmanica) of the southwestern Atlantic present differences and/or morphological variations with respect to the specimens described previously.
2. The Chaetognatha as well as the Pteropoda in the studied zone, have daily vertical migrations. Foraminifera lack them.
3. From the faunistic point of view the 050 m interval is very homogeneous in the studied area.
4. The Chaetognatha populations occupy both during the day and the night the subsurface layer and their daily vertical migrations affect the 050 m interval very little.
5. There exists a positive but low correlation among the specific distributions of the studied groups and the surface temperature of the water.
6. There exist in the southwestern Atlantic interspecific groups of associated species of Foraminifera, Pteropoda and Chaetognatha and numerous species associated with them. All these species can be ordered according to their affinity to warm or cold waters.
7. These groups of species are different from those found by other authors who worked with material from other zones.
8. There is a considerable coincidence between Foraminifera, Pteropoda and Chaetognatha as to the horizontal distribution of their indicator species. In general terms, to obtain a representative sample of the Chaetognatha of a certain area, it should be larger than that needed for Pteropoda and the one needed for the latter larger than that analogous for Foraminifera. Foraminifera are, in the sampled area, better hydrological indicators than the other two taxa.
9. Using the index of similarity between samples in the work area, 4 different faunistic zones can be determined: subtropical, subtropicalsubantarctic with subtropical dominance, subtropicalsubantarctic with subantarctic dominance and purely subantarctic.

Boltovskoy, D. 1979. Zooplankton of the south-western Atlantic. South African Journal of Science, 75(12):541-544.

Conclusions. The position and fluctuations of the Subtropical Convergence Zone have been studied in some detail in the western South Atlantic. However, very little is known about the Central Atlantic. Other problems that deserve attenion are the quantitative distribution of plankters, their occurrence as a function of depth, their mutual relations and those with physicochemical parameters, and the biological influence of the subAntarctic Divergence and the Tropical Convergence. The aim of this paper has been to stress our poor knowledge of a major oceanic area, pointing out some of the reasons for this situation and the aspects that are in need of research. At the same tme, I intended to give a very general review of its biological features, paying special attention to some of the problems that deserve further study. The Southwestern Atlantic lies between countries with increasing interest in oceanic problems; it is my feeling that joint research projects and an active exchange of information would greatly facilitate the task of investigating this vast region.

Boltovskoy, D., Riedel, W.R. 1980. Polycystine Radiolaria from the Southwestern Atlantic ocean plankton. Revista Española de Micropaleontología, 12(1):99-146.

Ninetyeight species of polycystine Radiolaria are recorded in 47 plankton samples collected in an area defined by 36°10.5' S, 39°45.9' S, 54°59.8' W and 49°27.4' W. New names for two actinommid species are proposed and a new species, Acanthosphaera pinchuda n. sp., is established. Most of the species were present in low densities and the spumellarians were dominant over the nassellarians.

Boltovskoy, D. 1982. Variación latitudinal de la diversidad zooplanctónica en el Atlántico Sudoccidental. Physis, Secc. A, 41(100):1-6.

On the basis of the analysis of the north-south distribution of several zooplanktonic taxa in the Southwestern Atlantic the author concludes that in the epipelagic waters of this area 1) Most warm-water zooplankters have subtropical rather than tropical dispersion centers. 2) There is a slight but conspicuous difference beween the tropical and the subtropical planktonic assemblages; the northern limit of the latter occurs close to the 20'S parallel. 3) The highest number of planktonic species is found between 30°S and 35°S, the later two parallels being the winter and summer (respectively) limits of the southernmost advance of purely subtropical waters. 4) The southernmost limit of the Transition Zone might lay somewhat to the north from the position defined by planktonic Foraminifera, namely around 40°S to 4S°S. In addition, it is suggested that the percentages of zooplanktonic species inhabiting the epipelagic waters of the World Ocean (with respect to the total of entirely or partly epipelagic recent zooplanktonic species) are distributed according to the following pattern: Polar 20%, Subpoolar 30%, Transitional 70%, Subtropical 80%, and Tropical 65-75%.

Dadón, J.R., Boltovskoy, D. 1982. Zooplanktonic recurrent groups (Pteropoda, Euphausiacea and Chaetognatha) in the Southwestern Atlantic ocean. Physis, Secc. A, 41(100):63-83.

Sobre la base del inventario crítico de prácticamente todos los trabajos que mencionan hallazgos de Pteropoda, Euphausiacea y Chaetognatha en el área comprendida entre 0° y 60°S, y 25° y 70°W (en total, alrededor de 3500 muestras tomadas entre los años 1885 y 1981), se determinaron los grupos de taxones de mayor afinidad distributiva (= grupos recurrentes). De las 104 especies y categorías infraespecíficas registradas, 64 quedaron distribuidas en, o asociadas a, 19 grupos recurrentes, de los cuales 11 fueron utilizados para la tipificación de diferentes áreas biogeográficas en el Atlántico Sudoccidental. Los resultados de las agrupaciones obtenidas, complementados con información previa, permitieron definir 9 áreas caracterizadas por conjuntos de pterópodos, eufáusidos y quetognatos particulares, y que constituyen zonas biogeográficas naturales diferentes. Los límites entre áreas son mas precisos y conspicuos en la parte meridional del Atlántico Sudoccidental (zonas Antártica, Subantártica y de Transición sur), que en la septentrional (zonas de Transición norte, Subtropical y Tropical), donde existe una mayor superposición y mezcla de conjuntos faunísticos. (In English).

Boltovskoy, D, Bender Kotzian, S., Pedrozo, F.L. 1983. Some new techniques for the preparation and illustration of Polycystina (Radiolaria). Micropaleontology, 29(4):382-390.

Scanning esectron microscopy (SEM) and light microscopy photographs of the same radiolarian specimens are vital for thorough and complete descriptions of polycystine species. Several media for light photography have been tested, including stained and unstaiden aqueous solutions, oils of varying refractve index and Farrant's medium The latter proved to yield excellent results; it can be used for permanent preparations, and also allows for an easy and fast retrieval of the specimens for ulterior SEM photography. Paired SEM pictures of radiolarian tests for stereoscopic viewing can furnish much useful information unavailable by other means. A detailed scheme on the steps to be taken for the preparation of Polycystinacontaining samples is included.

Boltovskoy, D., Jankilevich, S.S. 1985. Radiolarian distribution in east equatorial Pacific plankton. Oceanologica Acta, 8(1):101-123.

On the basis of radiolarian data, four major areas can be recognized in the Eastern equatorial Pacific Ocean (transected from approximately 9°N, 80°W to 2°N,140°W to 17°N, 155°W): 1) Between 5°N, 80°W and 2°N, 95°W, with high overall productivity and low radiolarian abundance and diversity; Spongodiscus sp. A, and to a lesser extent D. tetrathalamus, are the dominating taxa in this assemblage. 2) Along the equator, between approximately 95°W and 140°W. The productivity and planktonic standing stock of this area decrease to the west, while its radiolarian diversity and abundance increase, as well as the diversity of some other zooplankters. This area can be further subdivided into two sections at 124°W, the western one being conspicuously richer both quanti and qualitatively than the eastern section. O. stenozona + T. octacantha are characteristic of this area. 3) From approximately 6°N, 138°W to 10°N, 142°W radiolarian abundance and diversity drop sharply, as well as overall planktonic productivity and standing stock. 4) From approximately 10°N, 142°W to 17°N, 153°W there is a further decrease in radiolarian abundance and diversity.

Boltovskoy, D. 1986. Biogeography of the Southwestern Atlantic: current problems and prospects. In: Pelagic biogeography, Proceedings of an International Conference, The Netherlands, 29 May - 5 June 1985. Edited by A.C. Pierrot-Bults, S. Van der Spoel, B.J. Zahuranec y R.K. Johnson, UNESCO Technical Papers in Marine Science, No. 49, UNESCO Press, pp. 14-24.

Review of the biogeographic schemes proposed for the Southwestern Atlantic beginning at the turn of the century. General considerations on the geographic distribution patterns of planktonic species, in particular with respect to transition zones, distribution centers and expatriation. Comparisons with patterns described elsewhere.

Boltovskoy, D., Riedel, W.R. 1987. Polycystine Radiolaria of the California Current region: seasonal and geographic patterns. Marine Micropaleontology, 12(1):65-104.

Analysis of the 155 radiolarian taxa recorded in 48 plankton samples collected by means of 0-100 m tows between January and November 1972 in the California Current region revealed 3 faunal zones. The northernmost of these was dominated by Subarctic-transitional species; the central, which was comprised of 3 closely related subgroups, by intermediate-transitional taxa; and the southernmost by warm-transitional radiolarians. Of the taxa present in >5 samples, 47 - distributed among 12 species groups -plus 7 isolated species, showed significantly (P<0.05) higher abundances in either one of the areas defined. Four additional groups and several species were considerably more abundant and frequent in some areas than in others, but the corresponding differences were statistically non-significant. Some species (i.e., Acrosphaera murrayana, Spongocore cylindrica, Pseudocubus obeliscus, Trisulcus triacanthus, Botryostrobus auritus/australis, Spirocyrtis scalaris/cornutella, and Botryopyle dictyocephalus) were found to be associated with the coldest of the areas defined, rather than with the waters with highest tropical-equatorial influence, as would have been expected on the basis of previous studies. Comparison of our results with similar studies based on sedimentary materials showed some conspicuous differences, suggesting that sediments yield radiolarian assemblages with higher proportions of cold-water forms, presumably advected via subsurface currents. The cold-transitional assemblage had the lowest specific diversity and the highest dominance of a few abundant species over the rest; the intermediate-transitional showed highest diversities; and the warm-transitional lowest dominance. Indirect evidences suggest that the assemblages recorded are representative of normal, non-El Niño conditions.

Boltovskoy, D. 1987. Sedimentary record of radiolarian biogeography in the equatorial to Antarctic western Pacific Ocean. Micropaleontology, 33(3):267-281.

Analysis of 18 surface sediment samples from between 1°S and 64°S, along approx. 180°E, yielded 195 Recent radiolarian taxa. Clustering of the species and the samples, and further examination of the distribution patterns of radiolarian abundances, allowed definition of 5 climatic zones (Tropical to Antarctic) and several species groups and isolated species with variable degrees of selective loading on the 5 areas. Specific diversities were highest in the Tropical zone, and a secondary peak occurred at the northern edge of the Transition; the latter area was barren of endemic and, probably, also of characteristic taxa. A zonation of the transect based on a family and suborder level radiolarian census was very similar to the one based on the species, suggesting that the distribution of these higher-level categories is meaningful in ecological terms.

Boltovskoy, D. 1988. The range through method and first-last appearance data in paleontological surveys. Journal of Paleontology, 62(1):157-159.

The quality of the information yielded by stratigraphic and paleoecologic studies based on microfossils is often poor due to the spotty recovery of the taxa. Thus, downcore sequences contain many null records between the first appearance (FA) and the last appearance (LA) of the species. Cheetham and Deboo (1963) suggested the use of the range-through method (i.e., a species is considered present in a sample if found both above and below it, even if it was not found within the sample) as a means of smoothing these spotty data sets and, when biostratigraphic conclusions are sought, to counteract the effect of environmental influences (Hazel, 1970). The technique was subsequently adopted in many reports and incorporated in numerical methods for biostratigraphic work (e.g., see review in Brower, 1985). This procedure, however, has a distorting effect on the data in such a way that faunal similarities between the samples compared are artificially increased toward the middle of the column. This is due to the fact that, while in the original species by samples array the probability of filling any cell is mainly a function of the species' abundance and of the number of specimens scanned in that particular sample, in the matrix resulting from the range-through principle it also depends upon the number of samples checked both above and below the level in question. Since the number of these samples is highest for the central part of the sequence, and decreases toward the top and bottom, the central section will have artificially enhanced specific cooccurrences and, hence, faunal similarities. This distortion is subsequently reflected in the results attained after processing the indices such as, for example, in cluster analysis. This bias influences primarily the relative magnitude of the level at which the elements and groups of elements compared are associated and the makeup of the groups themselves, which can invalidate analyses aimed at the assessment of parameters such as faunistic breaks, turnovers, etc. Some other applications of the method, like the correlation of dated and undated samples (e.g., Tway et al., 1985), may not be greatly affected by range-through modifications of the original data matrix. The numbers of FA's and LA's of taxa at different levels in the sedimentary column have sometimes been used for the analysis of paleoecological and biostratigraphic events (e.g., Thomas, 1985). Yet, unless the total interval sampled is considerably longer than the life-span of the taxa involved and null records are due to actual absences (rather than to undersampling), the long-ranging and scarce organisms will tend to have their FA's and LA's closer to the ends of the sequence, than to its center. An extreme situation of this type is illustrated in a figure, where the 100 "taxa" are distributed at random in the 100 "samples" (i.e., all span the entire interval "sampled"). In both cases the problems involved are most significant when dealing with long-ranging taxa in highly diversified assemblages, like deep-sea benthic Foraminifera, which yield samples x species arrays with high percentages of null records between the FA's and the LA's of many species. Eliminating these rare species mitigates the drawback, but the problem is not solved altogether. In addition, given the usually high correlation between abundance and occurrence, the most abundant taxa are often also the most long-ranging (e.g., in deep-sea benthic Foraminifera) and, therefore, have limited use for biostratigraphic applications.

Boltovskoy, D., Alder, V.A. 1988. Estimates of microplanktonic biomass in Antarctic near-surface waters: the effects of wind. Polar Biology (Internacional, Alemania), 8(4):397-399.

Note on the relationship between microplanktonic concentrations in the upper 15 m and wind stress, in the Weddell Sea. It is concluded that wind-induced turbulence mixes the uppermost plankton-rich layers with the underlying plankton-poorer ones, thus yielding lower concentrations in surface samples.

Boltovskoy, D. 1988. Equatorward sedimentary shadows of near-surface oceanographic patterns. Speculations in Science and Technology, 11(3):219-232.

For most shelled plankters distributional patterns in the sediments are indicative of colder near-surface waters that those overlying the corresponding areas. A complementary or, sometimes, alternative explanation is offered for these disagreements: submersion of live colder-water organisms under warmer waters and subsequent death and sedimentation in a lower latitude zone might better account for many of the mismatching patterns reported than selective dissolution, differential productivity, reworking of colder (older) sediments, and lateral advection by bottom currents. Unless they are destroyed in the grazing process, phytoplanktonic cells are also susceptible to considerable subsurface transport and subsequent sedimentation in a lower latitude area within the gut contents of their consumers. Integration of low densities over large depth intervals, differential mortality rates and lack of reproduction of the expatriates can enhance the influence of this mechanism on extrapolar sedimentary assemblages.

Boltovskoy, E., Boltovskoy, D. 1988. Cenozoic deep-sea benthic Foraminifera: turnovers and between-site correlations. Revue de Micropaléontologie, 31(2):67-84.

A study of the Cenozoic deep-sea benthic Foraminifera from Deep Sea Drilling Project Sites 208, 289, 305, 357, 360 and 369 shows that Oligocene and post-Oligocene faunas differ little from Recent assemblages, this entire interval being characterized by slow and gradual faunal replacements; the most important faunal turnover recorded in these cores took place below the Eocene-Oligocene boundary. Within the Oligocene-Pliocene interval, most of the overall foraminiferal changes defined are not correlated between sites: faunal similarities are significantly and consistently greater between the stratigraphic units of the same site, than between coeval stratigraphic units of different sites; the makeup and relative proportions of foraminiferal assemblages are much more influenced by geographic location and by ecological factors than by their evolutionary history. Enhanced similarities between Sites 208, 289 and 357 (as compared with Sites 305, 360 and 369) during this same period are most probably due to bathymetric differences between the locales involved. The usefulness of deep-sea benthic Foraminifera for biostratigraphic interpretations is strongly restricted by their spotty occurrence, their long time-ranges, and their markedly local qualitative and quantitative character and variations.

Boltovskoy, D., Vrba, A. 1988. Classification and geographic distribution of Stylodictya - type radiolarians. Micropaleontology, 34(4):362-370.

A collection of 485 radiolarian Stylodictya - type shells from 17 surface sediment samples from the equatorial to Antarctic western Pacific Ocean was studied. Comparison of conventional taxonomic criteria used for the identification of the closely related taxa Stylodictya multispina (=S. validispina), S. aculeata, Porodiscus spp. and Stylochlamydium asteriscus with the results of an objective numerical analysis of 11 two-state and quantitative characters suggest that S. multispina and Porodiscus spp. are members of the same taxonomic unit which decreases in abundance from the equator to the Antarctic. S. asteriscus (predominantly warm-water) and S. aculeata (predominantly cold-water) are the other two members of this species group. Morphologic differences between these morphotypes are investigated and defined.

Boltovskoy, D., Vrba, A. 1989. Latitute-related shell patterns in Radiolaria: Botryostrobus auritus/australis morphotypes in the equatorial to Antarctic Pacific. Marine Micropaleontology, 13(4):309-323.

Analyses of the size, porosity and shape of 366 specimens of Botryostrobus auritus/australis retrieved from 17 surface sediment samples distributed more or less evenly between the equator and 64°S in the western Pacific Ocean show that most shape-related features vary rather evenly from the tropics to the pole, suggesting a close relationship with surface temperature and/or salinity; the size and porosity of the shells, on the other hand, are more closely associated with primary productivity in the upper layers than with latitude. Most changes are smooth and stepwise, although for several characters there is an increase in the average rate of variation in the southernmost tropical to northern subantarctic areas, in coincidence with the zone of the species' maximum relative abundance. It is concluded that the morphologic differences studied are not consistent enough as to justify the division of B. auritus/australis into several distributionally more restricted taxa. On the other hand, the overlap for the ranges of most traits in the various climatic zones transected is of such magnitude that it restricts the potential usefulness of the shape, porosity and size patterns surveyed as ecologic or paleoecologic indicators.

Boltovskoy, D. 1989. Radiolarian record of the last 40,000 years in the western equatorial Pacific. Oceanologica Acta, 12(1):79-86.

Polycystine radiolarians were studied in two box cores (ERDC 123Bx and ERDC 129Bx) from the equatorial western Pacific Ocean (approx. 1°S, 161°E), sampled at 3 cm intervals from the top (ca. 0 to 4,000-6,000 YBP) to the bottom (approx. 16,000 and 40,000 YBP, respectively). In total, 141 taxa were identified. Radiolarian assemblages were qualitatively and quantitatively (relative abundances) very similar both between cores and between samples; Octopyle stenozona/Tetrapyle octacantha was by far the most abundant form at all levels, followed in decreasing proportions by Tholospyris spp., Stylodictya multispina, Botryocyrtis scutum, and Didymocyrtis tetrathalamus. No significant changes in the specific makeup or the relative proportions of the taxa were found in association with the 18,000 YBP level. Slight evidence of an environmental change around 25,000 YBP was suggested by peaks of two radiolarians which presently characterize the more fertile eastern equatorial Pacific waters (O. stenozona/T. octacantha and Euchitonia/Dictyocoryne spp.), and by an increase in the relative contribution of two colder- and deeper-water species below this level.

Boltovskoy, D., Alder, V.A., Spinelli, F. 1989. Summer Weddell Sea microplankton: assemblage structure, distribution and abundance, with special emphasis on the Tintinnina. Polar Biology, 9:447-456.

Silicoflagellates, large thecate dinoflagellates and tintinnids were counted and measured in screened (26 um pore-size) pump-samples retrieved from a depth of ca. 9 m in February-March 1987 along a two-leg north-south transect in the Weddell Sea (approx. 62°S to 78°S). Fourteen tintinnid taxa were identified and their individual abundances and biomasses were estimated. Highest biomass, in terms of organic carbon, was recorded for the Tintinnina, which averaged 4.001 mg C m-3, with mean cell-numbers of 161 ind. l-1 (maximum: 859 ind. l-1); followed by the dinoflagellates (1.018 mg C m-3, mean: 192 ind. l-1; max.: 1176 ind. l-1); and the silicoflagellates (0.391 mg C m-3, mean: 467 ind. l-1, max.: 3123 ind. l-1). Conspicuous abundance and settling volume peaks were recorded at some distance off the edge of the ice-pack (at approx. 69°S to 72°S), and in the ice-covered area south of 74-75°S. This pattern was paralleled by changes in the specific makeup of tintinnid assemblages: in the ice-covered southern area Cymatocylis drygalskii and Laackmanniella prolongata were dominant, while in ice-free waters north of 73°S Codonellopsis gaussi, Cd. glacialis and Cymatocylis affinis/convallaria were the main components of the fauna. Overall tintinnid abundances were higher than those reported for many (but not all) extrapolar areas, and the average size of the species present was considerably larger than elsewhere; tintinnid carbon figures were therefore very high, oscillating around 2 mg C m-3 in the northern ice-free area, and 20 mg C m-3 in the southern ice-covered zone.

Boltovskoy, E., Boltovskoy, D. 1989. Paleocene-Pleistocene benthic foraminiferal evidence of major paleoceanographic events in the eastern south Atlantic (DSDP Site 525, Walvis Ridge). Marine Micropaleontology, 14:283-316.

Benthic foraminifers in the size-fraction greater than 0.073 mm were studied in 88 Paleocene to Pleistocene samples from Deep Sea Drilling Project Site 525 (Hole 525A, Walvis Ridge, eastern south Atlantic). Clustering of the samples on the basis on the 86 most abundant foraminifers (in total, 331 taxa were identified) allowed separating two major assemblage zones: the Paleocene to Eocene interval, and the Oligocene to Pleistocene interval. Each of these, in turn, were subdivided into three minor subzones as follows: lower upper Paleocene (approx. 62.4 to 57.8 Ma); upper upper Paleocene (56.6 to 56.2 Ma); lower and middle Eocene (55.3 to 46.8 Ma); upper Oligocene to middle Miocene (25.3 to 16 Ma); middle Miocene to Pliocene (15.7 to 4.2 Ma); and lower Pleistocene (0.4 to 0.02 Ma), with only minor differences with the previous zone. Some very abundant taxa span most of the column studied (Bolivina huneri, Cassidulina subglobosa, Eponides bradyi, E. weddellensis, Gavelinella micra, Oridorsalis umbonatus, etc.). Several of the faunal breaks recorded coincide with conspicuous minima in the specific diversity curve, thus suggesting that the corresponding turnovers signal the final stages of periods of faunal impoverishment. At least one major bottom-water temperature drop (as derived from d18O data) is synchronous with a decrease in the foraminiferal specific diversity. On the other hand, a specific diversity maximum in the middle Miocene might be associated with a d13C increase at approx. 16 to 12 Ma. Highest foraminiferal abundances (up to 600-800 individuals per g of dry sediment) occurred in the late Paleocene and in the early Pleistocene, in coincidence with the lowest diversity figures calculated. The magnitude of the most important faunal turnover recorded, between the middle Eocene and the late Oligocene, is magnified in our data set by the large hiatus which separates the middle Eocene from the upper Oligocene sediments. Considerably smaller overturns occurred within the late Paleocene (in coincidence with changes in the specific diversity, absolute abundance of foraminiferal tests, and d13C), and in the middle Miocene (in coincidence with a specific diversity maximum and a d13C excursion). New information on the morphology and the stratigraphic ranges of several species is furnished. For all the taxa recorded the number of occurrences, total number of individuals identified, and first and last appearances are listed.

Boltovskoy, D., Dinofrio, E., Alder, V.A. 1990. Environmental influence on intraspecific variability in Antarctic tintinnids: Cymatocylis affinis/convallaria in Weddell Sea waters. Journal of Plankton Research, 12(2):403-413.

Analyses of the morphometry of 630 loricae belonging to the described species Cymatocylis affinis and Cymatocylis convallaria retrieved from 21 samples collected in the Weddell Sea (60 to 73°S) strongly suggest that both taxa, including the four formae into which C. affinis was originally divided, are members of a single species. The only feature which varies significantly and consistently among the samples surveyed is the total length of the lorica, lowest average lengths being positively correlated with lowest absolute abundances of this tintinnid in the waters sampled. This relationship points at some unfavorable factor(s) which affect both tintinnid reproduction/survival and growth; the data analyzed suggest that drops in the availability of food might be responsible for the size (and abundance) variations observed.

Alder, V.A., Boltovskoy, D. 1991. Microplanktonic distributional patterns west of the Antarctic Peninsula, with special emphasis on the tintinnids. Polar Biology, 11(2):103-112.

Microplankton was sampled with a centrifugal suction pump in the surface layer (approx. 9 m) of the Bellingshausen Sea and the Bransfield Strait in March 1987, and concentrated with a 26 um-mesh net. Bulk microplanktonic settling volumes were assessed, silicoflagellates and large thecate dinoflagellates were counted, and tintinnids were counted and identified to species. Average (and maximum) values for the entire area surveyed were as follows, settling volume: 6.7 (43.3) ml/m3; silicoflagellates: 674 (7777) ind./l, 0.57 (6.54) mg C/m3; dinoflagellates: 109 (1321) ind./l, 1.40 (16.98) mg C/m3; tintinnids: 52 (589) ind./l, 1.15 (9.87) mg C/m3. The three geographic zones defined objectively on the basis of tintinnid specific assemblages also differed sharply in their surface salinity, overall microplanktonic abundance and bulk settling volume. The Bransfield Strait, with lowest settling volume values (2.1 ml/m3) and cell concentrations, was characterized by the dominance of Cymatocylis affinis/convallaria. In waters around the tip of the Antarctic Peninsula microplanktonic settling volumes averaged 4.6 ml/m3, cell concentrations were intermediate, and 79% of the tintinnids were represented by Codonellopsis balechi. The Bellingshausen Sea was characterized by the lowest salinities and the highest settling volumes (8.7 ml/m3) and cell counts; Laackmanniella spp. and Cymatocylis drygalskii, f. typica dominated this area. Almost all biological variables were significantly intercorrelated, and showed strong and mostly significant negative correlations with surface salinity, yet relationships between enhanced standing stock and ice meltwater were not obvious; rather, highest microplanktonic concentrations seemed to be due to ice-associated growth. Extremely high spatial correlations were found between the tintinnids and the dinoflagellates (r2: 0.941), suggesting the existence of close links between these two groups. Tintinnid species-specific assemblages show a coherent distributional pattern and well defined environment-related trends; most clearly differentiated preferences are exhibited by Laackmanniella prolongata (closely associated with ice-covered areas), Cymatocylis affinis/convallaria (oligotrophic open-ocean waters), and Codonellopsis balechi (coastal regions).

Boltovskoy, D. 1991. Holocene-upper Pleistocene radiolarian biogeography and paleoecology of the equatorial Pacific. Palaeogeography, Palaeoclimatology, Palaeoecology, 86:227-241.

Polycystine radiolarians were investigated in 66 samples from 5 box-cores spanning the last ca. 40,000 years from the western (approx. 160°E) and the central (136°W) equatorial Pacific. The assemblages investigated show clear differences associated with the geographic locations of the sites: the central Pacific is characterized by higher specific diversities, much higher absolute abundances of shells per gram of dry bulk sediment, and by conspicuously better radiolarian preservation. The differences involved also include significant changes in the relative proportions of several radiolarian species (these accounting for approx. 25% of total individuals), families and orders. These dissimilarities are chiefly attributed to differences in the primary production of the two zones and to enhanced advection of colder-water species characteristic of the California Current to the central equatorial Pacific. In both areas, downcore faunal changes, if present at all, are so weak that background noise from random sample-to-sample variations almost completely masks them. There do not seem to be any noticeable shifts associated with the 18 KyBP level. Inconclusive evidences of environmental changes at 30 to 20 KyBP are suggested in some of the cores by the increase in the proportions of several species characteristic of colder northeastern Pacific waters and by lower radiolarian accumulation rates; these changes seem to be paralleled by shifts in the isotopic composition of planktonic Foraminifera.

Boltovskoy, D., Vivequin, S.M., Swanberg, N.R. 1991. Vertical distribution of tintinnids and associated microplankton in the upper layer of the Barents Sea. Sarsia, 76:141-151.

In 61 samples collected in August 1988 in the upper 50 m of the Barents Sea the vertical distribution of chlorophyll a, dinoflagellates, tintinnids, microcrustaceans and fecal pellets did not show clear associations with the physical vertical structure of the waters involved. Tintinnid concentrations ranged between <1 and 314 ind./l, with an average of 46 ind./l for the 0-50 m layer. Mean organic carbon estimated per individual ranged from 1200 pg for the smallest tintinnid species, to 14,000 for the largest one, yielding an average of 0.33 µg C/l (max.: 2.1 µg C/l). At this time of the year tintinnids may consume 0.16 to 5% (mean: 1.4%) of total primary production. Tintinnid size was positively correlated with chlorophyll a concentrations, suggesting that food availability enhances lorica growth. In total, 9 tintinnid species were recorded; however, only 3 of these (Acanthostomella norvegica, Ptychocylis obtusa, and Parafavella denticulata) accounted for almost 90% of all the individuals.

Alder, V.A., Boltovskoy, D. 1991. The ecology and biogeography of tintinnid ciliates in the Atlantic Sector of the Southern Ocean. Marine Chemistry, 35(1-4):337-346.

Qualitative and quantitative analyses of the tintinnids retrieved in surface and vertical (down to 1150 m) samples in the Scotia, Weddell, Bransfield and Bellingshausen areas allow defining three distinct zones: (A) Scotia Sea, Bransfield Strait and oceanic waters of the northern-central Weddell Sea, dominated by Codonellopsis gaussi and Cymatocylis affinis/convallaria; (B) Shelf and mostly ice-covered areas of the southernmost Weddell Sea and the Bellingshausen Sea, characterized by Laackmanniella prolongata and Cymatocylis drygalskii; (C) Bransfield-Weddell waters around the tip of the Antarctic Peninsula, where Codonellopsis balechi accounts for 80% of the tintinnids. These areas have (often significantly) different ice regimes, water-column depths, surface salinities, bulk planktonic settling volumes and microplanktonic concentrations. On the other hand, the composition of tintinnid assemblages is very similar on both sides of the Antarctic Peninsula. Causal interpretations for these heterogeneous distribution patterns and probable specific adaptations to the dissimilar environmental settings involved are analyzed.

Boltovskoy, D., Alder, V.A. 1992. Microzooplankton and tintinnid species-specific assemblage structures: patterns of distribution and year-to-year variations in the Weddell Sea (Antarctica). Journal of Plankton Research, 14:1405-1423.

Silicoflagellates, large heterotrophic dinoflagellates, radiolarians, tintinnids and microcrustaceans were counted in 72 screened (15 µm) samples retrieved at 0 to 150 m from the Weddell Sea in January 1989. Tintinnid species were identified and for all groups biomass estimates were carried out on the basis of measurements of cell-dimensions. Dinoflagellates dominated the microheterotrophic community at all stations and depths (65% of overall microzooplanktonic carbon in the 0-150 m interval), followed by the tintinnids (18%), microcrustaceans (16%), and radiolarians (1%). All groups, with the exception of silicoflagellates, peaked noticeably in the vicinity of the southern end of the transect (76°-77°S). Relationships between concentrations of chlorophyll a and microzooplanktonic biomass were present yet not altogether consistent, but both phyto- and microzooplankton seemed to generally respond to regional enhancements associated with the ice-edge. Comparison with similar Weddell and Weddell-Scotia data retrieved in Feb.-Mar. 1987 and in Nov. 1988-Dec. 1989, respectively, are highly coherent in terms of microplanktonic abundances, their geographic and vertical distribution patterns, and the specific makeup and distribution of tintinnid assemblages. Analyses of the oral diameters of tintinnid morphotypes suggest that the latitudinal and vertical distribution of their 5 dominant taxa (which account for over 90% of all individuals) is structured so as to maximize resource partitioning.

Boltovskoy, D. 1992. Current and productivity patterns in the equatorial Pacific across the last glacial maximum based on radiolarian east-west and downcore faunal gradients. Micropaleontology, 38(4):1-18.

Radiolarians were studied in 11 box-cores (142 samples in total, obtained at 3 cm intervals) retrieved in the western (160°E), central (135°W), and eastern (90°W) equatorial Pacific. The western and central cores span the last ca. 40,000 years, while the eastern core is estimated to reach approx. 12,000-17,000 years. Time-averaged data show very sharp assemblage composition differences between the three locales. Species dominant at the westernmost sites are indicative of warm, oligotrophic conditions; thanatocoenoses from 135°W suggest strong input of California Current radiolarians; while the easternmost core hosts assemblages which point to a significant influence of the Peru Current. Downcore changes in the proportions of these three characteristic groups of species are inconclusive in the westernmost cores. In the central area the steady upcore increase in shells presumably advected from the northeastern Pacific, and the concomitant decrease of warmer-water radiolarians, indicate a growing influence of advection from the California Current. In the easternmost core colder-water indicators decrease from bottom to top, while those indicative of warmer waters increase, suggesting a gradual waning of advection from the Peru Current. It is concluded that, in the central and eastern parts of the equatorial Pacific belt, radiolarian distributional patterns in the sediments and their shifts during the last millennia respond chiefly to environmental conditions at depths in excess of 50 m (rather than to sea surface temperature), and to subsurface and deep lateral advection of shells from eastern boundary current areas.

Boltovskoy, D., Alder, V.A. 1992. Paleoecological implications of radiolarian distribution and standing stocks vs. accumulation rates in the Weddell Sea. The Antarctic Paleoenvironment: A Perspective on Global Change (J.P. Kennet & D.A. Warnke, eds.), Antarctic Research Series, 56:377-384, American Geophysical Union.

In the Scotia and Weddell Seas polycystine radiolarians dwell chiefly at depths between 200 and 300 m, their vertical patterns being strongly associated with the higher temperatures characteristic of the Warm Deep Water. At scales of approximately 400 to 2000 km and ca. 30 days, radiolarian horizontal quantitative distribution trends are not visibly affected by ice cover or primary production. On the other hand, comparison of polycystine standing stocks at 0-400 m vs. their accumulation rates at 400 to 900 m indicates that >90% of the shells are lost to sedimentation. It is suggested that mechanical fragmentation by grazing (rather than dissolution) is primarily responsible for this loss. Deep habitat and high destruction rates in the water-column are important factors which hinder the use of Antarctic polycystine thanatocoenoses for paleoecological reconstructions.

Alder, V.A., Boltovskoy, D. 1993. The ecology of microzooplankton in the Weddell-Scotia confluence area: horizontal and vertical distribution patterns. Journal of Marine Research, 51(2):323-344.

The distribution of microzooplankton (large dinoflagellates, foraminifers, radiolarians, tintinnids, microcrustaceans and various invertebrate larvae) was studied in samples retrieved from 10 to 400 m in two overlapping transects along 49°W, between 57°S and 61°30'S (27 Nov.-12 Dec. 1988, and 27 Dec. 1988-4 Jan. 1989). For each sample approx. 10 liters of water were concentrated with a 15 µm-mesh sieve and counted under an inverted microscope. Biomass estimates were based on measurements of cell dimensions. Dinoflagellates and tintinnids concentrated at 50-90 m (10-400 m weighted averages, dinoflagellates: 103 ind./l, 131 mg C/m¨; tintinnids: 9.7 ind./l, 53 mg C/m¨). Copepod nauplii had a more variable vertical pattern with maximum numbers at 100-200 m (10-400 m av.: 2.6 ind./l, 27 mg C/m¨). Foraminifers and radiolarians were most abundant in noticeably deeper waters peaking below 150 m (10-400 m av., foraminifers: 0.2 ind./l, 11 mg C/m¨; radiolarians: 2.7 ind./l, 12 mg C/m¨). Large dinoflagellates accounted, on the average, for 55% of the biomass of the heterotrophs considered in the 10-400 m layer, followed by the tintinnids (23%), copepod nauplii (11%), foraminifers (5%), and radiolarians (5%). The 100-400 m layer hosted up to 87% (mean: 49%) of total 10-400 m integrated microzooplanktonic biomass, and limited data for depths over 400 m indicate that these strata can contribute significantly (up to 50%) to total organic carbon, especially at the less fertile locales. The distribution of loricate ciliates was strongly correlated with those of chlorophyll a, and especially dinoflagellates (r=0.832, for log-transformed data), suggesting close trophic relationships between these two groups. The northern sites were generally richer in microzooplankton than the area closer to the ice-edge, and the southernmost ice-covered zone yielded the lowest microplanktonic values. This biological pattern, which was but loosely coupled with the Weddell-Scotia Confluence, with the vertical stability of the water column, and with near-surface concentrations of chlorophyll a, can at least partly be explained by differential grazing pressure by crustacean mesozooplankton. The time elapsed between the two transects did not affect the microzooplanktonic assemblages noticeably. Comparisons with previous abundance estimated carried out earlier and later in the growth season suggest that microzooplanktonic abundances increase toward the late summer-fall, probably in response to enhanced availability of nano- and pico-sized producers, characteristic of Antarctic post-bloom conditions.

Boltovskoy, D., Alder, V.A., Abelmann, A. 1993. Radiolarian sedimentary imprint in Atlantic equatorial sediments: comparison with the yearly flux at 853 m. Marine Micropaleontology, 23(1):1-12.

Radiolarian specific compositions in a series of 20 sediment trap samples covering an entire year (1.3.1989 to 16.3.1990, collected at 853 m) were compared with bottom (0-1 cm) materials from the same site (eastern equatorial Atlantic: 01°47.5'N, 11°07.6'W). Data on mean sediment accumulation rates at the site of the mooring (1.59 g/cm¨/ky), mean radiolarian flux at 883 m (28,446 shells/m¨/day), and abundance in the 0-1 cm bottom layer (48,258 shells/g) suggest that approx. 95% of the radiolarians produced are lost to the fossil record. Sediment trap sample-to-sample correlations (based on relative abundances of 40 radiolarian species present at levels ·1% in at least one sample, mean value, r=0.886) did not differ significantly from correlations between each water-column sample and surface sediments (mean r=0.878). Similarities between the flux and the sediments were not associated with time of year and with periods of enhanced radiolarian output. Two taxa had lower, and nine taxa had higher percentage contributions in the sediments than in any one sediment trap sample, and a few of the abundant species had averages up to 7 times higher in either the water-column or the sediments. These dissimilar percentage loadings are attributed to selective dissolution, lateral subsurface and deep advection of shells from higher-latitude areas, and identification biases. As opposed to species-level inventories, family-level databases (including shells identified to family only) differed significantly between the water-column and the sediments. Spumellaria (especially Spongodiscidae) were more abundant in the sediments (35%) than in the water-column (19%), while Nassellaria showed the opposite trend (64% and 80%, respectively). It is suggested that ease of identification of spongodiscid fragments and fragility of juvenile nassellarians are responsible for these differences.

Boltovskoy, D., Alder, V.A., Abelmann, A. 1993. Annual flux of Radiolaria and other shelled plankters in the eastern equatorial Atlantic at 853 m: seasonal variations and Polycystine species-specific responses. Deep-Sea Research, 40(9):1863-1895.

Polycystine radiolarians, phaeodarians, tintinnids, tintinnid cysts and molluscs (chiefly pteropod protoconchae) were counted in 20 time-series sediment trap samples retrieved in the eastern equatorial Atlantic (01°47.5'N, 11°07.6'W) at 853 m, between 1 March 1989 and 16 March 1990. In addition, polycystine species were identified. Mean annual fluxes, in ind./m¨/day, were: polycystines: 28,446, tintinnids: 27,275, foraminifers: 17,816, tintinnid (and probably other ciliates') cysts: 14,632, phaeodarians: 1370, and molluscs: 1192. These yields are noticeably higher than most previous data from various areas of the World Ocean, which in part is attributed to the inclusion of particles <10 µm. Only 3% of the polycystines and 30% of the phaeodarians were represented by "live" cells (i.e., with protoplasm). Indirect evidence suggests that foraminifer and radiolarian fluxes probably reflect fairly well their abundances in the plankton; for the tintinnids, however, only about 0.1% of the loricae reach 853 m intact. With the exception of tintinnid cysts and molluscs, fluxes for the groups counted were clearly correlated with total mass and organic carbon flux and, presumably, with primary production; in this area both peak in July-September and in January-April. It is concluded that tintinnid high reproduction rates are responsible for tightest associations between the output of their loricae and total flux. The fluxes of Foraminifera and Radiolaria, which have longer life spans (ca. 1 month), are more loosely correlated with total flux, and often show peaks approx. 20-40 days after those of the latter. Molluscs, with life spans of ca. 1 year, do not correlate with total flux. Juvenile Nassellaria comprised up to 44% of all polycystine shells (mean: 25%). In total, 187 polycystine taxa were recorded, yet only 6 accounted for over 50% of all the individuals identified. Although some species did vary in relative abundance in association with total and polycystine fluxes, these changes in assemblage composition were of very minor importance. Radiolarian equitability and the relative contribution of the Spumellaria were significantly higher at times of lower polycystine flux. These fluctuations, however, were also relatively small and their effect would not be expected to bias the sedimentary record toward restricted periods of higher radiolarian output. Comparison of the present data with detailed previous information for the Gulf of Alaska shows that both total radiolarian flux, and its rate of accumulation throughout the year, are very similar in the two areas.

Boltovskoy, D. 1994. The sedimentary record of pelagic biogeography. Progress in Oceanography, 34:135-160.

Sedimentary remains of fossilizable marine organisms, chiefly microplaktonic ones (coccolithophorids, silicoflagellates, diatoms, dinoflagellates, radiolarians, foraminifers) have long been used for biogeographic surveys, usually with the aim of unravelling paleoenvironmental settings. Utilization of bottom deposits (rather than plankton samples) has some advantages for this purpose: thanatocoenoses require smaller sample-sizes, materials are more readily available, and they eliminate the small time-scale variability which obscures long-term trends. On the other hand, the sedimentary imprint of planktonic distributional patterns is often severely distorted by fragmentation and dissolution of the biogenic remains, reworking of sediments, winnowing and lateral advection of shells, especially toward lower latitudes, seasonally and interanually variable output rates, and the integration of vertically heterogeneous assemblages. The biases derived from these processes are reviewed, and the need for more information on selective dissolution, vertical dustribution patterns and planktonic reproduction and output rates is stressed. Given the assumptions used in paleoenvironmental studies, distributional information drawn from sediment samples is less prone to yielding biased information when applied to these surveys, than to bio- or paleobiogeographic investigations; albeit the former can also be significantly affected due to changes in the traits that govern the formation of biogenic sediments.

Kling, S.A., Boltovskoy, D. 1995. Radiolarian vertical distribution patterns across the southern California Current. Deep-Sea Research, 42(2):191-231.

Polycystine radiolarians were identified in 36 plankton samples collected at depths ranging from 0 to 2000 m at 4 Stations extending west from about the U.S.Mexico border (approx. 32°N, 117°W to 124°W), in NovemberDecember 1977. In total, 136 radiolarian taxa were recorded, but 90% of all individuals were accounted for by only 40 of these. Highest abundances were found either at the surface, or at 25 to 50 m. Based on maxima in the vertical profiles of the most abundant radiolarians, three major depthintervals were defined in the upper 300 m: 050 m, 100 m, and 200300 m. Betweenstation similarities in the specific makeups of these layers, however, were low. Thirtynine taxa had peak abundances below 300 m at one or more stations; 11 of these are probably deepwater forms. Although in terms of individuals per liter of water filtered, upperlayer taxa are noticeably more abundant than deep species, the latter have much more extended depthranges, which might significantly enhance their sedimentary output. The inshore and oceanic stations shared very similar, warmerwater radiolarian assemblages in the uppermost 25 m, whereas the intermediate station was dominated by colderwater forms at those depths. Below 50 m, however, the inshore station had enhanced proportions of deeper and colderwater species, differing strongly from the oceanic site. We suggest that this pattern results from circulation of the Southern California Eddy, which transports Central Water from the oceanic station on the western edge of the California Current around the intermediate stations to the inshore station. The coldwater signal at subsurface layers of the inshore station could be reinforced by coastal upwelling and southward transport by the California Current thus further enhancing the abundances of deeperwater radiolarians at this site. Analyses of the affect of such vertical patterns on paleoceanographic interpretations stress the importance of the signal of "environmentally neutral" deepliving species, as well as that of shells produced in the nearsurface layers of distant areas and transported at depth to the region of the study.

Lange, C.B., Boltovskoy, D. 1995. Trampas de sedimento. "Manual de métodos ficológicos" (K. Alveal, M.E. Ferrario, E.C. Oliveira, E. Zar, eds.), Universidad de Concepción, Concepción, Chile, pp. 93-118.

General review of sediment trap methods and techniques, including trap design, hydrodynamic considerations, sampling protocols and preliminary treatment of samples, poisons and preservatives, swimmers, flux estimates, etc. (In Spanish).

Boltovskoy, D., Swanberg, N.R., Vivequin, S.M. 1995. Tintinnids and other microplankton from the Greenland Sea: abundance and distribution in the Marginal Ice Zone (May-June 1989). Marine Ecology (P.S.Z.N.), 16(2):1-15.

Microplankton (silicoflagellates, dinoflagellates, tintinnids, pteropods, crustaceans and fecal pellets) was analyzed in 71 0-95 m samples from the Greenland Sea collected in May-June 1989. Abundances were clearly associated with the ice edge, highest concentrations occurring in ice-free waters. The 15 to 30 m stratum was generally richer in microplankton than deeper waters, with the exception of microcrustaceans, which often peaked below 30 m. Six tintinnid species were identified. The mean size of the tintinnid P. denticulata from the Greenland Sea was consistently greater than that of Barents Sea specimens. It is suggested that colder waters and scarcer food are responsible for these morphometric differences.

Boltovskoy, D., Oberhaensli, H., Wefer, G. 1996. Radiolarian assemblages in the eastern tropical Atlantic: patterns in the plankton and in sediment trap samples. Journal of Marine Systems, 8(1/2):31-51.

Polycystine Radiolaria were studied in 40 Multinet (63 µm) plankton samples collected in February-March 1988 in the eastern tropical Atlantic (10°N to 17°S), from depths ranging between 0 and 300 m. A total of 148 taxa were recorded, most of them accounting for very low proportions of the individuals identified. The geographic distribution of polycystine assemblages throughout the area was relatively homogeneous and quite unpatterned; no clear associations with latitude, surface temperature, salinity or chlorophyll a were found. On the other hand, several radiolarians showed fairly distinct vertical profiles, allowing identification of forms preferring the uppermost 25-50 meters, forms peaking at 50 to 150 m, and forms with highest percentage contributions below 150 m. Comparison of this planktonic collection with a similar survey carried out in 1983 in the same area indicates good overall agreement. In contrast, radiolarian compositions in sediment trap samples deployed at 853 and 2195 m in close vicinity with some of the plankton stations surveyed are totally different from the present specific makeups and species proportions. Several mechanisms that can account for the remarkable contrasts observed are discussed, concluding that subsurface advection of shells produced at higher latitudes, and integration of low radiolarian abundances over large depth-intervals are most likely to cause the inconsistencies described.

Boltovskoy, E., Boltovskoy, D., Correa, N. Brandini, F. 1996. Planktonic foraminifers from the Southwestern Atlantic (30 to 60°S): species-specific patterns in the upper 50 m. Marine Micropaleontology, 28:53-72.

Planktonic foraminifers were studied in 96 samples collected in the southwestern Atlantic (30 to 60°S, along 53°W) in November 1993, mainly from depths between 0 and 50 m. Very high proportions of juveniles (unidentified) were present throughout the area, especially north of 37°S, where they accounted for up to 70-80% of all shells recorded. For most species no clear vertical specific stratification was detected in the 0-50 m layer. Zoogeographic grouping of the 18 species identified allowed defining 5 distinct zones along the transect: Subtropical (north of 31°S, 80% warm water individuals); Warm-Transitional (34-37°S, 35% warm water); Transitional (37-49°S, 99% cold water); Subantarctic (49-55°S, 100% cold water); and Antarctic (south of 56°S, 100% cold water). Boundaries between foraminiferal assemblage zones are in good agreement with hydrological fronts described for the area. Comparison of the present data with planktonic collections from the North Atlantic show large differences in the proportions of various taxa. In the 14-24°C range, G. bulloides is much more abundant in the northern hemisphere than in the southern one, whereas G. quinqueloba, G. inflata and G. rubescens show the opposite trend. On the other hand, temperature-related percentage contributions within the 14-24°C range indicate that the preferred thermic régimes of the 9 species considered are remarkably similar in the North and South Atlantic collections compared. The southernmost planktonic distributional ranges of selected warm water taxa are roughly coincident with those established previously on the basis of surface sediments, disagreements being chiefly attributable to selective dissolution on the bottom. In contrast, on the bottom percentages of cold water foraminifers (G. bulloides, G. pachyderma) are significantly enhanced with respect to their planktonic populations, and their sedimentary northward limits extend well beyond their maximum ranges in the upper-layer plankton. It is suggested that submergence of these cold water species and northward displacement at subsurface depths is chiefly responsible for the mismatching patterns observed. Dissimilar species proportions in both hemispheres and plankton-sediments uncouplings can conceivably engender erroneous conclusions when distributional data are used for paleoecologic reconstructions with the aid of numerical analyses such as the Imbrie-Kipp transfer-function technique.

Anderson, R.O., Nigrini, N., Boltovskoy, D., Takahashi, K. 1995 (in press). Radiolaria. In: "An Illustrated Guide to the Protozoa" (Second Edition), J. Lee, editor.

General overview of polycystine morphology, skeletal morphology, reproduction, distribution and ecology, and taxonomy. Diagnoses of extant families and orders. Identification keys for the most common polycystine spumellarian and nassellarian species.

Boltovskoy, D., Uliana, E., Wefer, G. 1996. Seasonal variations in the flux of microplankton and radiolarian assemblage compositions in the northeastern tropical Atlantic at 2195 m. Limnology & Oceangraphy, 41(4):615-635.

Fluxes of silicoflagellates, the dinoflagellate Actiniscus sp. , polycystine and phaeodarian radiolarians, tintinnids, ciliate (?) cysts, and pelagic molluscs were estimated in 13 sediment trap samples retrieved in the northeastern tropical Atlantic (20°55.3'N, 19°44.5'W), at 2195 m, between 22 March 1988 and 8 March 1989 (CB1 site). Each sample integrated the flux over 27 days. In addition, polycystines were identified to species in all samples. Highest fluxes were recorded for the polycystines, followed by the tintinnids, silicoflagellates, cysts, phaeodarians, Actiniscus, and molluscs. While for the phytoplankters our estimates are lower than most previously reported data, for polycystines (up to 162,133 ind. m2 day1) and tintinnids (up to 201,064 ind. m2 day1) the values found are among the highest ever recorded in the World Ocean. Temporal variations in the fluxes of the heterotrophic organisms counted were generally in good agreement with total mass flux, suggesting fairly tight couplings with primary production at the surface. Fluxes of tintinnids, whose fast reproduction rates allow them to react swiftly to changes in the availability of food, were more variable through time and were better associated with variations in total mass flux than those of the slower-reproducing radiolarians. In total, 145 polycystine taxa were identified. Species compositions changed very little throughout the year and did not vary with changes in total mass flux. Close comparison of the present data set with a similar survey based on a yearly series of sediment trap samples retrieved between 1 March 1989 and 16 March 1990 from 853 m at a nearby location (1°47'N, 11°07'W, eastern equatorial Atlantic, GBN3 site), showed significant differences, both in the fluxes of the groups surveyed, and in the percentages of many polycystine species. All groups (except silicoflagellates) had noticeably higher output rates at CB1, and proportions of several polycystines associated with colder and/or more productive environments were higher at CB1 than at GBN3. Conversely, GBN3 yielded higher proportions of various radiolarians characteristic of warmer and more oligotrophic waters. Because temperatures below ca. 70 m are higher at CB1 than at GBN3, it is suggested that different productivity levels (approximately 0.6 and 0.2 g C m2 day1, respectively), rather than different surface temperatures (CB1: 19-24°C, GBN3: 22-28°C) are important in structuring the specific differences recorded. The potential effects of several other contrasting traits are explored as complementary or alternative explanations. These include dissimilar near-surface thermic regimes, yearly ranges in primary production, different trapping depths and associated effects of lateral advection and input of deep-living forms, and multi-year climatic changes. Inferred lack of coupling between near-surface populations and their record in the 2195 m traps, and absence of species-specific responses to changes in total mass flux (and, presumably, in primary production), pose interesting questions in connection with the use of the microfossil record for paleoceanographic surveys. Some members of the polycystine family Plagoniidae account for very large proportions of total radiolarians in eastern boundary current upwelling systems, which suggests their potential usefulness as paleoindicators of upwelling conditions.

Boltovskoy, D. 1998. Classification and Distribution of South Atlantic Recent Polycystine Radiolaria. Palaeontologia Electronica, 1(2): 116 pp., 2.5 MB. http://www-odp.tamu.edu/paleo/1998_2/boltovskoy/issue2.htm.

This paper presents a review of the current knowledge on the identification and distribution of Recent polycystine Radiolaria so far recorded or presumed to occur in the South Atlantic Ocean (0 to 60°S, from the South American coasts to the coasts of Africa). However, because the area concerned covers from equatorial to Antarctic waters, and since polycystine radiolarians are geographically (but not environmentally) cosmopolitan, the review covers most common species worldwide. Illustrations, short diagnoses, bibliographic references and distributional data (both geographic and vertical) are included for 164 polycystine morphotypes (species-groups, species, and subsspecific categories). Introductory remarks offer general data on radiolarian anatomy, biology, ecology, and reproduction. Methodological aspects are dealt wth in some detail, with special emphasis being placed on comparative aspects of the environmental and paleoenvironmental information conveyed by planktonic materials, sediment trap samples, and sedimentary deposits. Known or assumed geographic and vertical species-specific distribution ranges are summarized, as well as available information on absolute abundances in the water-column (plankton and sediment trap samples) and in the surface sediments. A profusely illustrated glossary aimed at the less experienced student defines the terms and morphological details useful for diagnostic purposes.

Boltovskoy, D. 1998. Pelagic biogeography: background, gaps and trends. "Pelagic Biogeography ICoPB II" (IOC Wks. Rep. 142), (A.C. Pierrot-Bults, S. van del Spoel, eds.), pp. 53-64.

Because pelagic biogeography is intimately associated with many widely different fields of marine research, its boundaries as a science are vague and imprecise. The "classical" approach to biogeography, which involves the study of the geographic distribution of taxonomic entities, however, is somewhat better defined, and is chiefly based on identifications and counts. The major oceanic provinces of the World Ocean were more or less adequately defined by about the middle of this century, mostly on the basis of qualitative (presence-absence) distributional data. During the 60's and 70's, counts - in addition to identifications - became widespread. This quantitative information strongly modified some earlier concepts of the structure and dynamics of several marine systems, but changes to the basic biogeographic schemes established by 1950-1960 were generally minor. Although various regional and global studies showed that floral and faunal patterns allow recognition of a larger number of distinct areas than the 9 defined in the earlier studies (4 paired ones in the two hemispheres: Polar, Subpolar, Transitional, and Subtropical; and the Tropical or Equatorial), this basic scheme is still the most widely accepted, which suggests that, for the time being, this is as much biogeographic detail as we can produce at ocean-wide scales without raising significant disagreements. The fact that biogeographic boundaries in the pelagic realm have not experienced major changes in the last 30-40 years is partly due to the soundness of the early divisions established, partly to methodological artifacts, partly to the increasing state of disarray of the systematics of many groups, and partly to the decline in taxonomic and distributional studies (between 1985 and 1993 the share of publications on the geographic distribution of marine organisms dropped about 4-fold). Some of the issues that ought to be addressed in order to further our understanding of pelagic biogeography include: (1) More intensive coverage of some poorly known areas, such as the south Atlantic and south Pacific oceans; (2) Investigation of seasonal and multiannual changes by means of sediment traps and varved sediments. For this purpose a better understanding of the processes which govern coupling between specific makeups in the epipelagic (plankton samples), mid-depths (sediment traps), and the surface sediments (cores) is necessary; (3) Efforts at a more efficient utilization of the information available, which in turn requires the generation of widely accessible and acceptable, standardized, taxonomic and geographic databases.

Thompson, G.A., Alder, V.A., Boltovskoy, D., Brandini, F. 1999. Abundance and biogeography of tintinnids (Ciliophora) and associated microzooplankton in the Southwestern Atlantic Ocean. Journal of Plankton Research, 21(7):1265-1298.

Absolute abundances of foraminifers, polycystine and phaeodarian radiolarians, tintinnids, pteropods, and early crustacean larvae and moults were assessed in a collection of 57 vertically stratified (0-100 m) net microplankton samples from 22 stations located between 34 and 58°S (along 51-56°W), covered in November 9-16, 1994. Tintinnids were identified to species and measured in order to estimate their biomass from biovolume to carbon conversions. Distribution of the microzooplanktonic groups assessed was irregular and patchy, both geographically and vertically, and their abundances are characteristic of oceanic low to medium productivity environments. Tintinnid biomass was also generally low (0.05 to 0.40 µg C l-1). With the exception of the tintinnids, associations between microzooplanktonic numbers and chlorophyll a were generally loose. Eighty-eight tintinnid taxa were recorded, yet only 5 accounted for 53% of the specimens identified. Multivariate (cluster) analysis of tintinnid specific distribution patterns clearly showed several distinct zones, from north to south these are: Transition Zone (TZ), with 3 subzones, TZ north (34°S-38°S), TZ central (39°44íS-44°S), and TZ south (46°S); Subantarctic Zone (SZ, 48-55íS); Polar Front Zone (55°30íS); and Antarctic Zone (AZ, 58-59°36íS). Each of these was characterized by distinct tintinnid composition, abundance and biomass. With few exceptions, tintinnid cells were fairly evenly distributed throughout the upper 50 m. Specific composition usually changed little with depth. Mean population depths were calculated for a subset of 35 tintinnids; 29 of these dwell preferably above 40 m. Spatial distribution of tintinnid species richness showed a more or less gradual decrease from north to south. Specific diversity and equitability generally increased with depth, and were higher in antarctic waters than the southern transitional and subantarctic ones; this trend is tentatively attributed to higher water-column vertical stability south of the Polar Front.

Boltovskoy, D., Gibbons, Mark J., Hutchings, L., Binet, D. 1999. General biological features of the South Atlantic. "South Atlantic Zooplankton" (D. Boltovskoy, ed.), Backhuys Publishers, Leiden, pp. 1-42. 5.

Because pelagic biogeography is intimately associated with many widely different fields of marine research, its boundaries as a science are vague and imprecise. The "classical" approach to biogeography, which involves the study of the geographic distribution of taxonomic entities, however, is somewhat better defined, and is chiefly based on identifications and counts. The major oceanic provinces of the World Ocean were more or less adequately defined by about the middle of this century, mostly on the basis of qualitative (presence-absence) distributional data. During the 60's and 70's, counts - in addition to identifications - became widespread. This quantitative information strongly modified some earlier concepts of the structure and dynamics of several marine systems, but changes to the basic biogeographic schemes established by 1950-1960 were generally minor. Although various regional and global studies showed that floral and faúnal patterns allow recognition of a larger number of distinct areas than the 9 defined in the earlier studies (4 paired ones in the two hemispheres: Polar, Subpolar, Transitional, and Subtropical; and the Tropical or Equatorial), this basic scheme is still the most widely accepted, which suggests that, for the time being, this is as much biogeographic detail as we can produce at ocean-wide scales without raising significant disagreements. The fact that biogeographic boundaries in the pelagic realm have not experienced major changes in the last 30-40 years is partly due to the soundness of the early divisions established, partly to methodological artifacts, partly to the increasing state of disarray of the systematics of many groups, and partly to the decline in taxonomic and distributional studies (between 1985 and 1993 the share of publications on the geographic distribution of marine organisms dropped about 4-fold). Some of the issues that ought to be addressed in order to further our understanding of pelagic biogeography include: (1) More intensive coverage of some poorly known areas, such as the south Atlantic and south Pacific oceans; (2) Investigation of seasonal and multiannual changes by means of sediment traps and varved sediments. For this purpose a better understanding of the processes which govern coupling between specific makeups in the epipelagic (plankton samples), mid-depths (sediment traps), and the surface sediments (cores) is necessary; (3) Efforts at a more efficient utilization of the information available, which in turn requires the generation of widely accessible and acceptable, standardized, taxonomic and geographic databases.

Boltovskoy, D. 1999. Radiolaria Polycystina. "South Atlantic Zooplankton" (D. Boltovskoy, ed.), Backhuys Publishers, Leiden, pp. 149-212.

The chapter offers data on the identification and geographic distribution in the South Atlantic Ocean (0º to 60ºS, coast to coast) of the 160 species of Radiolaria Polycystina known or presumed to occur in this area. It includes (a) A brief introduction with general remarks on biological traits of the group (reproduction and life-histories, salient cytological and anatomical features, trophic relationships, etc.); (b) Specific methodological recommendations on collection, preservation, preparation and observation of the specimens; (c) Horizontal and vertical distribution patterns in the South Atlantic, with remarks on world-wide distribution. Distributional data for each of the species treated are provided in a table (where the information available is adequate, overall geographic ranges are given; otherwise no extrapolations are attempted but the isolated confirmed records are provided); (d) Taxonomy and identification, including profusely illustrated and detailed reviews of diagnostic characters and an illustrated glossary of specific terms. Discussions of the current status of classification systems, a general outline classification of the group, and diagnoses and/or keys for species and suprageneric categories. For all the species included, diagnoses and/or keys for identification are provided. All species are illustrated with line-drawings and/or photographs (macro, light microscope and scanning electron microscope).

Kling, S.A., Boltovskoy, D. Radiolaria Phaeodaria. 1999."South Atlantic Zooplankton" (D. Boltovskoy, ed.), Backhuys Publishers, Leiden, pp. 213-264.

The chapter offers data on the identification and geographic distribution in the South Atlantic Ocean (0º to 60ºS, coast to coast) of the 158 species of Radiolaria Phaeodaria known or presumed to occur in this area. It includes (a) A brief introduction with general remarks on biological traits of the group (reproduction and life-histories, salient cytological and anatomical features, trophic relationships, etc.); (b) Specific methodological recommendations on collection, preservation, preparation and observation of the specimens; (c) Horizontal and vertical distribution patterns in the South Atlantic, with remarks on world-wide distribution. Distributional data for each of the species treated are provided in a table (where the information available is adequate, overall geographic ranges are given; otherwise no extrapolations are attempted but the isolated confirmed records are provided); (d) Taxonomy and identification, including profusely illustrated and detailed reviews of diagnostic characters and an illustrated glossary of specific terms. Discussions of the current status of classification systems, a general outline classification of the group, and diagnoses and/or keys for species and suprageneric categories. For all the species included, diagnoses and/or keys for identification are provided. All species are illustrated with line-drawings and/or photographs (macro, light microscope and scanning electron microscope).

Bernstein, R., Kling, S.A., Boltovskoy, D. Acantharia. 1999."South Atlantic Zooplankton" (D. Boltovskoy, ed.), Backhuys Publishers, Leiden, pp. 75-147.

The chapter offers data on the identification and geographic distribution in the South Atlantic Ocean (0º to 60ºS, coast to coast) of the 150 described species of Acantharia. It includes (a) A brief introduction with general remarks on biological traits of the group (reproduction and life-histories, salient cytological and anatomical features, trophic relationships, etc.); (b) Specific methodological recommendations on collection, preservation, preparation and observation of the specimens; (c) Horizontal and vertical distribution patterns in the South Atlantic, with remarks on world-wide distribution. Distributional data for each of the species treated are provided in a table (where the information available is adequate, overall geographic ranges are given; otherwise no extrapolations are attempted but the isolated confirmed records are provided); (d) Taxonomy and identification, including profusely illustrated and detailed reviews of diagnostic characters and an illustrated glossary of specific terms. Discussions of the current status of classification systems, a general outline classification of the group, and diagnoses and/or keys for species and suprageneric categories. For all the species included, diagnoses and/or keys for identification are provided. All species are illustrated with line-drawings and/or photographs (macro, light microscope and scanning electron microscope).

Boltovskoy, E., Boltovskoy, D., Brandini, F. In press. Planktonic Foraminifera from Southwestern Atlantic epipelagic waters: abundance, distribution and year-to-year variations. Journal of the Marine Biological Association of the United Kingdom.

The abundance and the latitudinal and vertical (0-100 m) distribution of planktonic Foraminifera was investigated on the basis of 38 samples collected in November 1994 in the southwestern Atlantic Ocean (34-60°S, along 51-56°W). Mean foraminiferal densities were 1.5 ind. l-1 (range: 0.1-5.9 ind. l-1), with highest concentrations in subsurface waters (20-50 m). Couplings between the distribution of chlorophyll a and foraminiferal abundances were very loose. Distribution patterns of the 15 species recorded allowed 6 distinct areas to be defined along the transect surveyed; from north to south these are: Subtropical (dominated by Globigerinoides ruber and G. trilobus), Cold intrusion (Globigerinita uvula), Transitional-Subtropical and Transitional (Globigerina bulloides, Globigerina quinqueloba), Subantarctic (G. quinqueloba), and Antarctic (Neogloboquadrina pachyderma, left coiling). Close comparisons with the yields of a similar data set collected in November 1993 show very good agreement. Foraminiferal thermic régimes were also similar in 1993 and in 1994, but for some species significant differences with previous data are noticed. While the southwards extensions of the ranges of warm water species are fairly well circumscribed by the Brazil Current-influenced waters, several foraminifers widely used as indicators and paleoindicators of cool waters (in particular Globigerina bulloides, Globigerina quinqueloba and Globigerinita uvula) were recorded in very significant numbers at temperatures as high as 20-24°C. The implication of these findings for hydrological, ecological, and paleoecological interpretations is discussed.

Brandini, F., Boltovskoy, D., Piola, A., Kocmur, S., Röttgerns, R., Abreu, P.C. In press (June 2000). The effects of fronts on the distribution of nutrients and chlorophyll in the Southwestern Atlantic between 30 and 62°S. Deep Sea Research, 47(6):1015-1033.

This paper presents the first data on the vertical distribution of chlorophyll and nutrients in the upper layers of the southern Southwestern Atlantic, in relation to frontal systems and the general hydrographic features. The survey covered quasisimultaneously the area between 30 and 62°S, at the beginning of the austral summer of 3 consecutive years (1993 through 1995). Our results show a rather stable oceanographic structure, with similar patterns of latitudinal chlorophyll and nutrient distributions. An outstanding feature present throughout the three seasons covered are two zones of high phytoplankton production, where bloom chlorophyll concentrations of >1 µg/l seem to occur frequently. The first area is the upper euphotic zone of the Brazil-Malvinas Confluence zone between approximately 36 and 50°S. The second chlorophyll-rich zone is centered on subsurface layers of the Antarctic Surface Water south of the Polar Front as far as 62°S. The rest of the area covered shows low chlorophyll concentrations, either due to nutrient limitation (subtropical waters of the Brazil Current), or to excessive turbulence and upper-layer instability (Malvinas Current). The occurrence of a permanent meander around 38°S was noticed in coincidence with the cyclonic retroflexion of the Malvinas Current, causing upwelling of deep water. The ecologic implications of this eddy-induced upwelling are discussed.

Boltovskoy, D. In press. Diversidad y biogeografía del zooplancton del Atlántico Sur. Anales de la Academia Nacional de Ciencias Exactas, Físicas y Naturales, Buenos Aires, Argentina.

Hasta la actualidad se han descripto cerca de 7000 zoopláncteres marinos, incluyendo especies y categorías subespecíficas. Esta cifra casi duplica a la cantidad de especies fitoplanctónicas conocidas (ca. 4000), pero es varias veces inferior a la de animales bentónicos marinos (más de 180,000). En el zooplancton no existe asociación entre la filiación taxonómica superior (phylum, clase) y la diversidad: la mayoría de los phyla y clases incluyen tanto grupos planctónicos específicamente ricos, como grupos pobres en especies. Los copépodos, el grupo ecológicamente más importante, tienen casi 3 veces más especies que cualquier otro taxón, pero esta relación entre diversidad e importancia ecológica no es una regla general. El Atlántico Sur alberga al menos un 60% de las especies de zooplancton existentes en el mundo, pero solamente un 35-40% de éstas fue confirmado hasta la fecha. Los regionalismos más pronunciados se dan en los grupos más íntimamente ligados con el fondo y con las costas. El Indo-Pacífico es más rico en especies marinas bentónicas y costeras, pero no en animales plamctónicos pelagiales. El análisis de la evolución hictórica de la descripcion de especies nuevas sugiere que en la actualidad conocemos la mitad o menos de los animales zooplanctónicos existentes. La fracción desconocida, sin embargo, está principalmente entre los organismos más crípticos, más raros, más delicados y menos accesibles. El área Tropical del Atlántico Sur alberga el 72% de todas las especies presentes en este hemi-océano, 78% en la Subtropical, 57% en la Transición, 39% en la Subantártica, y 20% en la Antártica. Los mismos valores para las especies restringidas a estas zonas son: 8, 2, 3, 2, y 5%, respectivamente. Las formas cosmopolitas, presentes desde el ecuador hasta la Antártida, solamente representan el 10% del total. Son muy pocos los zoopláncteres que están confinados a una sola de las áreas biogeográficas (entre 2 y 8%); la mayoría se encuentran en al menos 2 zonas contiguas y algo menos en 3 zonas sucesivas. La riqueza específica de la banda Tropical-Subtropical es 3-4 veces superior a aquélla de las aguas Subpolares y Polares; sin embargo, la cantidad de especies restringidas (y no meramente presentes) a las aguas cálidas es casi 10 veces superior a la de las frías. El comportamiento de los grupos individuales es variable y puede diferir sensiblemente de esta tendencia general. Las especies de Appendicularia son las que exhiben rangos latitudinales de dispersión más amplios, con un grado de cosmopolitismo casi dos veces mayor que el grupo menos cosmopolita - los tintínidos. Los zoopláncteres considerados también difieren sustancialmente en su afinidad por las latitudes altas o bajas: para los grupos más termófilos los habitantes Antárticos y Subantárticos representan solamente el 10-20% del total, mientras que para los más criófilos más del 50% de las formas conocidas se hallan en aguas Antárticas. Los grupos con más especies de amplia distribución tienen, en líneas generales, mayores proporciones de representantes criófilos. Progresando de norte a sur, en la Transición es donde la diversidad zooplanctónica disminuye más bruscamente. Los márgenes de la Transición tienen cerca de dos veces más cortes distributivos que el límite Tropical-Subtropical o el Subantártico-Antártico. La barrera Transicional no solamente afecta una gran cantidad de especies, sino que es mucho más extendida geográficamente, abarcando unos 12-14° de latitud. Las formas de mayor profundidad ocupan áreas más amplias: en el epiplancton los organismos de distribución amplia solamente representan un 11-12% de todas las formas computadas, mientras que por debajo de los 500-1000 m su proporción crece hasta el 38-42%. Si bien las cantidades de especies de prácticamente todos los grupos de animales y plantas terrestres, de agua dulce y marinos disminuyen con la distancia al ecuador, en el zooplancton marino pelagial las máximas cantidades de especies se encuentran en las latitudes medias.

Boltovskoy, D. 1996. Calentamiento global, el océano y el plancton. Ciencia e Investigación (Buenos Aires), 47:4-15. Republished in 1997 in Interscientia, 2(1) [http://aix1.uottawa.ca/publications/interscientia/inter.3/clima/clima.html] (Popular article)

La preocupación creciente de que las actividades del hombre estén modificando el clima de nuestro planeta ha desbordado el ámbito académico y es tema frecuente de notas periodísticas en todo el mundo. Aunque las opiniones de los expertos acerca de este proceso son dispares, la magnitud de sus implicancias potenciales es tal que justifica sobradamente las inversiones que se realizan en su estudio. Si bien el análisis de las anomalías climáticas pronosticadas es principalmente tema de trabajo de los meteorólogos, climatólogos y oceanógrafos físicos y químicos, la vastedad del problema y de sus consecuencias probables requiere un enfoque interdisplinario de amplio espectro. El presente artículo presenta un panorama general de las fluctuaciones del clima en diferentes escalas temporales, y pormenoriza la contribución de los estudios biológicos y paleontológicos sobre micropláncteres oceánicos a definir si la actual tendencia al calentamiento global es parte de un ciclo normal, independiente de las influencias antrópicas, o si escapa a las fluctuaciones "normales" y, por ende, podría presagiar desviaciones "anómalas" de origen humano.

Alder, V.A., Thompson, G.A. Spatial and temporal distribution of tintinnids (Protozoa, Ciliata) in relation to frontal systems and the general hydrologic dynamics of the Southern Ocean (SW Atlantic Sector; 50°-64°S, 65°-49°W). In press VII SCAR Symposium Proceeding.

Distribution patterns of tintinnid species were assessed from the analysis of 77 microplankton samples collected during four different summer surveys in the southwestern Atlantic sector of the Southern Ocean. Further analysis of the results in relation to major local hydrological constraints and temporal fluctuations allowed recognizing five biogeographic zones within the area of the study: Subantarctic Neritic (SNZ), Subantarctic Oceanic (SOZ), Antarctic Oceanic (AOZ), Antarctic Peninsular (APZ) and Polar Frontal (PFZ) zones. Total number of tintinnid species recorded in the whole study site was 35. As compared to the SOZ, the PFZ and the AOZ yielded noticeably higher biomass values (124 and 303 vs. 20 µgC m-3). The SOZ hosted 13 species characterized by low and uniform overall abundances This trend was quite stable interannually (1993, 1994). The AOZ hosted 10 species, only one of which was surely common also in the SOZ. In this zone, within Drake Passage waters, rich patches were observed appearing in a seemingly random manner, within much poorer areas. Total tintinnid abundance increased at the Polar Front or immediately south of it, although maximum values were detected in the partially ice-covered waters of the Weddell-Scotia Confluence (WSC), probably as a response to the combined action of this front and the Marginal Ice Zone. Low tintinnid densities registered also in the WSC and on 55°W are tentatively explained by a deficient supply or type of food, and to macrozooplanktonic grazing pressure. Some tintinnid species proved to be useful as hydrological indicators of summer frontal locations (Codonellopsis pusilla, Cymatocylis convallaria), extent of the Antarctic Circumpolar Current (Cymatocylis antarctica) and transport by warm or cold eddies. Confrontation of biogeographic (this work) and hydrological zonations (historical data) show an agreement with respect to the summer location of the Polar Front. Opposedly, the location and the extension of the Polar Frontal Zone and the Subantarctic Front as reported in literature do not match tintinnid findings, thus suggesting that the latter constraints are more variable and capable of modifying the basic distribution patterns of planktonic organisms. Immigration of foreign species was 3 to 4 times higher in SOZ than in the AOZ. If foreign species are not taken into consideration, biodiversity estimates for antarctic and subantarctic waters proved very similar.

Bordino P., Thompson G., Iniguez M. 1999. Ecology and behaviour of the franciscana (Pontoporia blainvillei) in Bahia Anegada, Argentina. Journal of Cetacean Research and Management, 1(2), 213-222.

From January 1993 to July 1997, franciscana sightings were recorded from shore-based stations and vessels at Bahia Anegada, Argentina. In total, 321 hours were spent in direct observation of dolphins following the Ad libitum and Focal sampling methods. The present study provides information on the ecology and behaviour of the franciscana in the study area. A total of 251sightings were made and the number of sightings per unit effort (SPUE) was significantly greater during spring (p=0.001). Dolphins were recorded at a mean distance from shore of 3.2km (0.4km-10.7km), although they were found at a significantly greater mean distance from shore during winter (p=0.005). More sightings were recorded during flood tide than during ebb tide (p=0.016). A higher SPUE was also recorded from a sailboat than from a motor boat (p=0.005). Group size was small, ranging from 1 to 6 individuals. Calves were recorded during spring and summer and only one calf was observed per group. The behaviour showed a seasonal pattern with co-operative feeding and travelling activities increasing during winter. Tide and depth also influenced behaviour. Co-operative feeding increased during flood tide, while travelling decreased. The behavioural ecology of the franciscana appears similar to that of other coastal and river dolphins. This study represents the first attempts to understand the behaviour of the franciscana in its natural habitat.

Volpedo, A.V., G. Thompson. (1998) 1996. Diferencias en el crecimiento de las sagittae de Prionotus nudigula Ginsburg, 1950 (Pisces: Triglidae) en relacion al sexo. Bol. Inst. Esp. Oceanogr., 12(1):3-16

Sex-related growth differences in the sagiltae of Prionotus nudigula Ginsburg, 1950 (Pisces: Triglidae). The objective of the present paper is to study the morphology of the sagitta and calculate the morphometric parameters of the otolith in relationship to growth in length and weight of the fish. These parameters are necessary in age and growth studies of Prionotus nudigula Ginsburg, 1950. For each one of the 354 Prionotus nudigula specimens sex, total weight (P) and height (LT) were recorded, as well as maximum length (LO) and maximum width (A0) of the sagittae. The following relationships were analysed: P vs LT, LO vs LT AO vs LT; LO vs P and AO vs LO for female and males, as well as without discrimination between sexes. For the study of these relationships, the regression model with potential adjustment was used. The right and left sagittae of the same individual did not present meaningful differences; therefore, they are morphometrically and morphologically equal. The otoliths of males and female did not present differences in the topography of the internal and external sides, though is was observed that the sagittae of females are, longer than those of males. The analysis of relationships P vs LT and LO vs LT and P show that al the same length, females are heavier than males. The relationships LO vs LT and P and AO vs LO indicated a differential growth between sexes.


Boltovskoy, D., Vélez, G. 1983/1984. A simple and inexpensive device for rigging light-and-dark bottle castings. Acta Hydrobiologica, 25/26(1):117-119.

A small, transparent, perforated acrylic plate furnished with a rubber band is designed for rigging series of light-and-dark bottle sets for studies of planktonic primary production.

Boltovskoy, D., Pedrozo, F.L., Battistoni, P.A. 1984. The effects of wind and diel vertical migrations on the distribution of freshwater zooplankton. Studies on Neotropical Fauna and Environment, 19(3):137-154.

A 24 hr survey of the behaviour of the zooplankton in a shallow (approximately 1 m), eutrophic pond showed that both vertical distribution and abundancechanges at the sampling site reflect several interacting factors, i. e., windforce and direction, local depth, diel vertical migrations, swimming capabilities of the animals, illumination, and, probably, "avoidance of shore" reactions. Small zooplankters, lacking strong powers of locomotion (i.e., Rotifera, Copepoda nauplii) exhibit similar features: their distribution is rather homogeneous through time and space, and is chiefly conditioned by wind. Larger plankters, such as adult copepods and cladocerans, tend to concentrate at different depths during a 24 hr cycle; as a consequence differential horizontal currents displace varying proportions of their populations at different times, thus either concentrating the organisms at a given area, or carrying them away from it. This variability suggests that the influence of the factors mentioned on the estimates of zooplanktonic abundance and biomass, based on samples collected under different conditions, must be thoroughly evaluated when carrying out ecological investigations.

Boltovskoy, D., Pedrozo, F.L., Mazzoni, H.E., Díaz, M. 1985. Effects of net, pump and bottle sampling on the abundance estimates of planktonic Rotifera. Journal of Plankton Research, 7(2):295-302.

Eightyseven freshwater plankton samples collected by means of two different nets, a submersible centrifugal pump and a 5.8 l water bottle were compared with respect to their ability to catch the rotifer Keratella cochlearis. Sample size, illumination (day/night), the presence of bridles ahead of the net mouths (versus unbridled nets), and different mouth diameters (0.2 and 0.5 m) did not affect abundance estimates. Slight differences were found between the yields of pushed nets versus towed nets; these are probably due to uneven distribution of the animals in the 0-3 m layer. Both pump and bottle volumes strongly affected abundance estimates. Net sample results were always considerably higher (4.6-12.3 times) than pump and bottle estimates; these differences are most probably due to evading reactions of the rotifer.

Boltovskoy, D., Mazzoni, H.E. 1988. The effects of sampling gear and environmental conditions on the abundance estimates of zooplankton. Revue d'Hydrobiologie Tropicale, 21(1):21-34.

Freshwater zooplankters (Rotifera, Cladocera and Copepoda) were counted in 96 plankton samples collected mainly from a small eutrophic reservoir in Córdoba, Argentina. Sampling gear used were two different nets (pushed ahead of the boat and towed behind it, with and without bridles), a submersible centrifugal pump, and a water bottle. The results suggest that neither net size nor bridles have measurable effects on the net yields. Disturbance of the upper layer during the daytime prior to collection engenders avoiding reactions which are responsible for conspicuously lower net, pump and bottle catches, while at night disturbance-related biases were not present. The zooplankters surveyed are more efficiently collected by nets in overcast weather and at night than under full sun; this is tentatively attributed to optomotor dodging reactions. As compared with net samples, both the stationary pump and the bottle underestimate densities; disturbance-related dispersion of the animals is partly responsible for this bias. In addition, all three groups studied have very strong positive rheotactic reactions and actively avoid the intake of the pump. The efficiency differences observed span, in some cases, several orders of magnitude.

Boltovskoy, D., Izaguirre, I., Correa, N. 1995. Feeding selectivity of Corbicula fluminea (Bivalvia) on natural phytoplankton. Hydrobiologia, 312:171-182.

Phytoplankton in water samples from the lower delta of the Paraná river (Argentina) and in the gut contents of a local population of the Asiatic clam Corbicula fluminea was identified and counted monthly between April 1992 and March 1993. Relative abundances of algal species were generally similar in the medium and in the stomachs of clams, suggesting the absence of feeding selectivity on the basis of taxonomic group or size-class. Diatoms made up a slightly but consistently larger (yet not significantly different) proportion of the diet of C. fluminea than of the plankton; this pattern is attributed to enhanced preservation of algal siliceous frustules, rather than to feeding selectivity. It is suggested that non-selective feeding by the bivalve is a response to the overall scarcity of food and, probably, to food collection by a combination of deposit and filter feeding.

Boltovskoy, D., Correa, N., Cataldo, D., Stripeikis, J., Tudino, M. 1997. Environmental stress on Corbicula fluminea (Bivalvia) in the Paraná river delta (Argentina): complex pollution-related disruption of population structures. Archiv für Hydrobiologie, 138(4):483-507.

Corbicula fluminea was collected at monthly intervals in November 1991-June 1993, and in March, April 1995 at a site located in the vicinity of strong sources of industrial and sewage effluents (confluence of the rivers San Antonio and Vinculación, SaV); and in November 1994 and March, April 1995 at a presumably less polluted one (Paraná de las Palmas river, PP), in the lower delta of the Paraná river (Argentina). Abundances at SaV ranged between 430 and 10,300 ind. m-2, being noticeably higher than those at PP, as well as those at 19 stations between and around these two locales. Shell lengths at SaV were monotonous throughout the 19-months period, over 90% of the clams varying between 16 and 22.5 mm in length; no discernible cohorts were recorded. At PP, on the other hand, juveniles below 5 mm were largely dominant, and shells above 25-30 mm in length were very common. Larvae retrieved from the gills of gravid clams showed much greater mortality rates in waters from SaV (up to 75% after 120 hr), than in those from PP and in the control (approximately 10% after 192 hr). The first internal growth-related mark in clams from SaV was closer to the umbo (mean: 14.2 mm), than that in clams from PP (mean: 24 mm). It is concluded that inadequate water quality at SaV is responsible for 100% mortalities of newborns, for dwarfed adult clams, and for the lack of discernible cohorts. High densities at this site are presumably maintained by downstream dispersal of small adults.

Cataldo, D., Boltovskoy, D. 1998. Population dynamics of Corbicula fluminea (Bivalvia) in the Paraná river delta (Argentina). Hydrobiologia, 380(1/2):153-163.

Benthic individuals and drifting planktonic juveniles of Corbicula fluminea were sampled in the Lower Delta of the Paraná River (Argentina) at monthly intervals between October 1995 and October 1996. Densities of settled clams above 1 mm, around 300-1000 ind. m-2, varied little throughout the year. Below 1 mm benthic juveniles, on the other hand, showed a single conspicuous abundance peak in October-November (up to 1722 ind. m-2), and were practically absent during the rest of the year (overall annual mean: 1070±797 ind. m-2). Drifting juveniles showed one major peak in December 1995 (160 ind. m-3), and a minor one at the end of March (24 ind. m-3). Length-frequency analyses of the monthly field data clearly indicate a highly structured population with a single well defined reproduction period centered on October-November. Population parameters derived from the seasonally oscillating version of von Bertalanffy's growth formula were as follows: maximum shell length: 32 mm (maximum observed shell length: 33 mm); growth constant: 0.65; growth seasonality (i.e., span of summer-to-winter growth-rate difference): 0.7; winter point (i.e., time of the year when growth is minimum): 0.5 (June-July); estimated size range for one year-old individuals: 15.3 to 22.4 mm; for two years: 23.5-27 mm, and three years: 27.5-29.3 mm. Comparison with previous data confirm the influence of water temperature on the clam's reproduction and growth and furnish additional evidence suggesting that food availability may be as important for recruitment as thermic regimes. Contrasts between traits of the population analyzed herein with those described previously from a nearby (ca. 10 km) site more influenced by industrial pollution point at the influence of water quality on Corbicula's recruitment and growth.

Boltovskoy, D., Cataldo, D. 1999. Population dynamics of Limnoperna fortunei, an invasive fouling mollusc, in the lower Paraná river (Argentina). Biofouling, 14(3):255-263.

Settling and growth of the Asian freshwater invasive pest bivalve Limnoperna fortunei (Dunker) on experimental PVC frameworks deployed in the Paraná de las Palmas river, ca. 130 km north of Buenos Aires (33°57.5íS, 59°12.5íW), was monitored in 1998 at monthly intervals. Surface water temperatures at the work site varied between 12.9°C (June) and 26.5°C (December). Frameworks were deployed in January. In February and March colonization reached 38000-44000 mussels m-2, with early juveniles (<2 mm) accounting for over 98% of the animals. In April through August total densities decreased to 9000-2000 ind. m-2, populations being dominated by older (>2 mm) mussels. In September through December densities grew steadily again, with early juveniles (<2 mm) accounting for over 95% of the mussels recorded. During their first month of life, animals born in January grew to ca. 3-4 mm in length; in March they reached 7-8 mm, and 11-12 mm by mid April. In late April through July growth rate decreased to <2 mm per month, and in August it stopped almost completely, resuming again in late September. During the first year of life animals born in January reach 20 mm in length; by the end of the second year estimated length is 30 mm, with a maximum theoretical length of 35 mm being reached after 3 years. Our data agree with the reported population dynamics of L. fortunei in Hong Kong in that both populations are characterized by extended reproduction periods lasting ca. 9 months, and that the spring onset of breeding is triggered by a rise in temperature above approx. 16-17°C. On the other hand, in the Paraná river reproduction is continuous between September and March, and the period of lowest yearly temperatures is characterized by a very strong breeding decline, whereas for the Chinese populations 2-3 yearly spatfalls and breeding pulses roughly in coincidence with lowest and highest water temperatures were described.

Cataldo, D., Boltovskoy, D. In press. Yearly reproductive activity of Limnoperna fortunei (Bivalvia) as inferred from the occurrence of its larvae in the plankton of the lower Paraná river and the Río de la Plata estuary (Argentina). Aquatic Ecology.

Densities of planktonic larvae of the Asian freshwater invasive pest bivalve Limnoperna fortunei (Dunker) were monitored weekly between 19 September 1997 and 22 January 1999 at two sites: the Paraná de las Palmas river, ca. 130 km north of Buenos Aires (33°57.5'S, 59°12.5'W), and a coastal station on the Río de la Plata estuary, in Buenos Aires (34°33.5'S, 58°24.5'W). Very variable but generally high (up to 25,000-35,000 ind. m-3) concentrations were recorded at both sites in September 1997-April 1998, and again in August 1998-January 1999, suggesting continuous reproduction during these months. In May through July 1998 larval densities were generally below 100-200 ind. m-3. The threshold temperature level associated with the onset and termination of reproduction was ca. 16-17°C. With the exception of August-September 1998, when Río de la Plata temperatures were below 16.7°C and larval concentrations less than 1000 ind. m-3, whereas those of the Paraná were above 16.7°C, with 1300-13,000 larvae m-3, coupling between the two sites investigated was generally good. Since its invasion in Argentina around 1990, L. fortunei has rapidly become a major nuisance for industrial and power plants located along the lower Paraná and Río de la Plata. The fact that the mollusc produces larvae during 9 months per year greatly hinders its control.

Cataldo, D., Colombo, J.C., Boltovskoy, D., Bilos, C., Landoni, P. In press. Environmental toxicity assessment in the Paraná river delta (Argentina): simultaneous evaluation of selected pollutants and mortality rates of Corbicula fluminea (Bivalvia) juveniles. Environmental Pollution.

Water and sediment samples were collected in the lower Paraná delta at four sites with different levels of exposure to pollution to evaluate the anthropogenic impact through chemical analyses and mortality bioassays. Individual polychlorinated biphenyls (PCBs), chlorinated pesticides (CHLPs), aliphatic hydrocarbons (ALIHCs), polycyclic aromatic hydrocarbons (PAH), and heavy metals (HM) were measured in waters, porewaters and sediments. The same three phases were also subjected to toxicity assays with straight-hinged juveniles of Corbicula fluminea. Concentrations of several pollutants were above levels recommended for the protection of aquatic life: in waters, Zn, Cu and Cr were 1.6-4.9 times higher, whereas in the sediments Cr was 1.8-3.6, and benzo(a)pyrene was 2.8-5.6 times higher. Pollutant concentrations followed a clear geographic pattern with highest values in the densely populated area of the Reconquista and Luján rivers, lower levels in the San Antonio, and lowest loadings in the remote Paraná de las Palmas. This gradient was adequately matched by the pattern of mortality rates of Corbicula fluminea early juveniles, which were highest in the Reconquista-Luján (40-93%) and lowest (and not significantly different from the control) in the Paraná (3.3-23%). Mortality rates also increased from surface waters (3.3-53%), to porewaters (12-73%), to sediments (23-93%). Although toxicity was probably mainly due to dissolved contaminants, agreement between chemical and biological evidences of pollution was best for the sediment compartment, whereas porewater and surface water showed a higher degree of variability.

Correa, N., Boltovskoy, D. 1998. Las invasiones biológicas. Componente ignorado del cambio global. Ciencia e Investigación, 51(1/2):4-14. (Popular article)

El desplazamiento de especies animales y vegetales de un lugar a otro, ya sea por sus propios medios o gracias a la actividad de otros animales o el hombre, es un proceso contínuo. Sin embargo, en los últimos años estos desplazamientos se han intensificado muy sensiblemente, debido a la creciente actividad comercial y turística del mundo. Este proceso da lugar a la invasión de áreas por parte de especies nuevas, fenómeno que en la gran mayoría de los casos repercute desvaforablemente sobre el lugar invadido. El trabajo reseña los mecanismos de este proceso, las tendencias actuales en su desarrollo, y analiza varios casos puntuales de especial interés en la Argentina.

de Cabo, L., S. Arreghini, A. Puig y H. F. Olguín. 1998. Caracterización fisicoquímica y del plancton del Bajo Delta del Río Paraná. Rev. Mus. Arg. Cs. Nats., Ser. Hidrobiol., VIII (1): 1 - 14

La información édita sobre fisicoquímica y plancton de la franja externa del delta paranaense es escasa, a pesar de su ubicación aguas abajo de importantes polos industriales y próxima a las ciudades más pobladas del país. Durante 1995 se realizaron cuatro muestreos en diferentes condiciones hidrológicas en cinco sitios. El fitoplancton estuvo dominado por las Bacillariophyceae, y el zooplancton, por los rotíferos y las larvas nauplii, como es común en ambientes fluviales. Los parámetros físicoquímicos reflejaron el pico de creciente en el Paraná Medio, el cual al inundar la zona baja y suboxigenada de la llanura aluvial, produce disminución de oxígeno disuelto, nitratos, sulfatos y aumentos en fósforo reactivo soluble, conductividad, bicarbonatos y calcio. La densidad del fitoplancton y del zooplancton aumentó cuando el nivel hidrométrico fue bajo. El frente de avance (estación Bajos del Temor) reflejó la acción del Río de la Plata, evidenciando aumentos de conductividad. En esta zona, la muerte y descomposición de los juncales, que crecen intensamente, aumenta la concentración de bicarbonatos y disminuye el pH, la concentración de oxígeno, nitratos y sulfatos. En los pajonales disminuyó marcadamente la concentración de nutrientes, los que serían captados por la vegetación. En Bajos del Temor durante el estiaje tendió a mantenerse baja la densidad del fitoplancton y a aumentar la de crustáceos y rotíferos.

Physicochemical and planktonic information about the more external Paraná Delta area has been poorly reported in spite of it location downstream from important industries and near Argentinaís more populous cities. During 1995 water samples were taken in four different hydrologic conditions at five sites. Phytoplankton was dominated by Bacillariophyceae, while zooplankton was dominated by rotifers and nauplii, groups that are nearly always dominant in lotic environments. The physicochemical parameters measured reflect the Middle Paraná at its highest water level. When the water floods the low and suboxigenated alluvial valley, produces a decrease of: oxygen, nitrates and sulphates and an increase in: soluble reactive phosphorus, conductivity, bicarbonates and calcium. The phytoplankton and zooplankton density increased when the hidrometric level was low. Conductivity is higher in the newer parts of the Delta (Bajos del Temor station), due to the influence of the Río de la Plata estuary. The death and decomposition of an important macrophyte biomass in this area produces an increase of bicarbonates and a decrease of: pH, oxygen, nitrates and sulphates. Nutrient concentration decreases in marshy areas, because of uptake by aquatic vegetation. During the low water period, in Bajos del Temor station, phytoplankton density decreases and crustaceans and rotifers density increases.

Olguín, H., Salibián, A. and Puig, A. 2000 Comparative sensitivity of Scenedesmus acutus and Chlorella pyrenoidosa as sentinel organisms for aquatic ecotoxicity assessment: studies on a highly polluted urban river. Enviromental Toxicology 15 (1): 14-22.

The effects of spatial and temporal differences on the water quality of the urban contaminated Reconquista River (Argentina) were evaluated by means of bioassays on the growth of two algal populations (Chlorella pyrenoidosa and Scenedesmus acutus). The effects produced by the addition of cadmium and/or nutrient salts to the samples were also assayed. Noticeable differences in algal biomass were detected among samples from different sites, the highest values corresponding to the most polluted zones. The toxic effect of cadmium was more pronounced in S. acutus than in C. pyrenoidosa, particularly in the least polluted waters. The addition of nutrient salts to the culture medium attenuated heavy metal toxicity, mainly to C. pyrenoidosa, and also revealed nutrient limitation to algal growth in certain sites and dates. Site classifications based both on algal bioassays and on physical and chemical variables showed good agreement.

Castañé, P. M., C. R. Loez, H. Olguín, A. Puig, M. G. Rovedatti, M. L. Topalián y A. Salibián. 1998. Caracterización y variación espacial de parámetros fisicoquímicos y del plancton en un río urbano contaminado. Rev. Int. Contam. Ambient. 14 (2): 69 - 77.

Durante 1994 se muestreó mensualmente el agua superficial (hasta 50 cm) en cinco sitios (a 5, 10, 20, 38 y 46 km de las nacientes) del Río Reconquista (Buenos Aires, Argentina), receptor de efluentes domésticos, agrícolas e industriales. Con el fin de profundizar la caracterización de este río y determinar sus tendencias espaciales, se determinaron 22 parámetros físicos y químicos, así como la composición y densidad del fito y zooplancton. Se notó un mayor deterioro de la calidad del agua río abajo, manifestando gradientes o un cambio brusco después de la desembocadura del Arroyo Morón, altamente contaminado. Amonio, ortofosfatos, dureza, temperatura, alcalinidad, DBO, DQO, fenoles, cloruros y conductividad aumentaron aguas abajo, mientras oxígeno disuelto y pH disminuyeron. El oxígeno disuelto (19 veces entre valores extremos de las medias anuales de los cinco sitios) el amonio (16 veces) y la DBO (6 veces) mostraron la mayor variación espacial. Las concentraciones de los metales pesados generalmente excedieron los niveles de protección para la vida acuática. La densidad del fitoplancton (media: 6.400 ind/mL) estuvo dominada por Chlorophyceae, Bacillariophyceae y Cyanophyceae; y la del zooplancton (media: 67 ind/L), por rotíferos y nauplii. La densidad media del fitoplancton total aumentó hasta el sitio distante 38 km de las nacientes, lo que pudo interpretarse como una consecuencia del progresivo enriquecimiento en nutrientes, y disminuyó en el último, donde habrían prevalecido los efectos tóxicos de los contaminantes. El deterioro espacial creciente de la calidad del agua se asoció negativamente con la abundancia de los grupos de crustáceos planctónicos.

Characterization and spatial variation of limnological parameters of a polluted urban river. During 1994 monthly surface water (up to 50 cm) samples were taken from five sites (5, 10, 20, 38 and 46 km away from the origin) along the Reconquista river (Buenos Aires), which receives domestic, agricultural and industrial effluents. In order to thoroughly characterize this river and to evaluate its spatial trends, 22 physical and chemical parameters, as well as the phyto- and zooplankton composition and abundance were determined. Most of the physical and chemical parameters evidenced an increased water quality deterioration downstream, displaying gradients or a sudden change after the discharge of the highly polluted Morón stream. Ammonium, orthophosphates, hardness, temperature, alkalinity, BOD, COD, phenols, chlorides and conductivity increased along the river, whereas dissolved oxygen and pH decreased. The parameters that showed highest spatial variation where dissolved oxygen (19 times, when comparing the higher and lower annual means of the five sampling sites), ammonium (16 times) and BOD (6 times). Heavy metals concentration generally exceeded the aquatic life protection levels. Phytoplankton density (mean: 6 400 ind/mL) was mainly made up by Chlorophyceae, Bacillariophyceae and Cyanophyceae, while zooplankton (mean: 67 ind/L) was mainly made up by rotifers and nauplii. The mean density of total phytoplankton increased up to 38 km away from the origin, wich could by interpreted as a consequence of the progressive nutrient enrichment downstream, and decreased in the last site, where toxic effects of pollutants were probably prevalent. The increasing deterioration of water quality was negatively associated with the abundance of planktonic crustaceans.

Olguín, H. F. y P. E. Domínguez. 1995. Corrientes, turbulencia y distribución de las algas dominantes en el Sector Poniente del Embalse Peñuelas (Valparaíso, Chile). An. Mus. Hist. Nat. Valpso. 23: 5-20.

Currents, turbulence and dominant algae distribution at west side of Peñuelas Reservoir (Valparaíso, Chile). The working hypothesis was that spatial distribution of phytoplankton was defined by interaction of advection and/or turbulence processes with the floating or settling tendency of the algae. Algae would be randomly distributed if vertical and horizontal component were simultaneously suppressed. The objective were estimate the pattern of superficial currents and turbulence induced by wind stress and establish the effect of currents and turbulence on the spatial distribution of most abundant algae. The experimental approach considered the following subject: the area studied was the west side of the reservoir Peñuelas. Drifters were used to detect wind-induced currents and temperature profile to estimate turbulence. Phytoplankton was collected at eight litoral and three limnetic stations each two meter. The sampling was performed twice a day, before and after wind actions. The results were: The water dynamic was characterized by horizontal circulation. Temperature gradients between surface and bottom of the reservoir did not permit completely mix of water column. In a scale below a day, leeward patches of floating and mobile algae (Microcystis aeruginosa, Anabaena circinalis and Peridinium sp.) are detected only in small bays. Vertical stratification of Melosira granulata could be related to temperature gradients. Microcystis incerta presented a random distribution.

Olguín, H., C. Lange y F. Brandini. 1997. Distribución de las Diatomeas en el Atlántico Sudoccidental: Resultados Preliminares. Resúmenes expandidos VII Congreso Latinoamericano sobre Ciencias del Mar (COLACMAR). Santos, San Pablo, Brasil: 231-232.

Planktonic diatoms were studied in samples collected in the southwestern Atlantic (30º to 60º S, along 53º W) in November 1993, from depths between 0 and 50 m (quantitative samples) and 0-100 m (qualitative ones). Highest total diatom density was found in the Antarctic Convergence zone, where diversity was lowest with a few species dominating the assemblages. The mixture of cold and warm water species observed north of the Antarctic Convergence represents the transition between between subtropical (Brazil current) and subantarctic waters (Malvinas current).

de Cabo, L., A. Puig, S. Arreghini, H. F. Olguín, R. Seoane & I. Obertello. 1999. Physicochemical parameters and plankton in the Lower Delta of the Paraná River in relation with flow. Manaus í99. Hydrological and Geochemical Processes in Large Scale River Basins: 1 - 7.

This study evaluated temporal variations of physicochemical parameters, phytoplankton and zooplankton, under different flow conditions, in the Lower Delta of the Parana River. This first approach was developed during 1995 and included a high flow of considerable magnitude. Four samplings without influence of meteorological phenomenon "sudestada" were carried out in four sites, including different monthly flows. Temporal variations of most of physicochemical and biological parameters overcame the spatial ones and were associated mostly to hydrological regime. The diluter-concentrator action of flow was reflected in chloride variation (conservative ion). Water exchange originated by flood of marshy environments caused decrease of dissolved oxygen, nitrates, sulphates and increase of phosphates, conductivity, bicarbonates, calcium and magnesium in the main course. Increase of nitrates, sulphates and phytoplankton and zooplankton densities were observed during low flow. This variation in density of some organisms exceeded the simple concentration effect for flow decrease.

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