Microzooplankton and tintinnid species-specific assemblage structures: patterns of distribution and year-to-year variations in the Weddell Sea (Antarctica) |
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Authors: | Boltovskoy, Demetrio Alder, Viviana A. |
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Affiliation: | 1Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires 1428 Buenos Aires, and CONICET 2Instituto Antártico Argentino Cerrito 1248, 1010 Buenos Aires, Argentina |
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Abstract: | Silicoflagellates, large heterotrophic dinoflagellates, radiolarians,tintinnids and micro-crustaceans were counted in 72 screened(15 µm) samples retrieved at 0150 m from the WeddellSea in January 1989. Tintinnid species were identified and biomassestimates were carried out for all groups on the basis of measurementsof cell dimensions. Dinoflagellates dominated the micro-heterotrophiccommunity at all stations and depths (65% of overall microzooplanktoniccarbon in the 0150 m interval), followed by the tintinnids(18%), microcrustaceans (16%) and radiolarians (1%). All groups,with the exception of silicoflagellates, peaked noticeably inthe vicinity of the southern end of the transect (7677°S).Relationships between concentrations of chlorophyll a and microzooplanktonicbiomass were present, yet not altogether consistent, but bothphyto- and microzooplankton seemed to generally respond to regionalenhancements associated with the ice edge. Comparison with similarWeddell and Weddell-Scotia data retrieved in February-March1987 and November 1988-December 1989, respectively, are highlycoherent in terms of microplanktonic abundances, their geographicand vertical distribution patterns, and the specific make-upand distribution of tintinnid assemblages. Analyses of the oraldiameters of tintinnid morphotypes suggest that the latitudinaland vertical distribution of their five dominant taxa (whichaccount for >90% of all individuals) is structured so asto maximize resource partitioning. |
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