Vertical patterns of polycystine species richness

BOLTOVSKOY DEMETRIO

Blairsden, California, USA

Congreso; INTERRAD 2000; 2000

Interrad

VERTICAL PATTERNS OF POLYCYSTINE SPECIES RICHNESS   BOLTOVSKOY, D., Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina (and CONICET, MACN)   Information on the vertical distribution of the numbers of polycystine species in the water column down to depths of over 5000 m was analyzed in order to estimate the proportions of the entire taxocoenosis inhabiting the various depth intervals. Main sources of data were extensive plankton net and sediment trap collections from the tropical and temperate Pacific and Atlantic oceans (published and unpublished information). The results of this assessment indicate that percentages of the total species inventory down to 200 m are the following: 0-40 m: 70% 0-60 m: 80% 0-100 m: 95% A similar calculation for the 0-5500 m water column yields the following values: 0-200 m: 70% 0-500 m: 75% 0-1000 m: 85% 0-3000 m: 97%  Although the fact that in extrapolar areas below 100-150 m the number of living polycystine species decreases with depth is beyond doubt, in most cases investigated there is a significant positive correlation between the numbers of species recorded (as well as specific diversity) and trap or net-tow depth. This effect is presumably the result of the accumulation of radiolarian species (represented by living and dead cells) with depth, a bias which is restricted to shelled plankters. Staining the protists’ cytoplasm (with Bengal rose, Sudan black B, eosin) does not seem to solve the problem because the time it takes the cytoplasm to decay is usually longer than the time it takes a radiolarian shell to reach the sea‑floor. Alternative approaches to assess the vertical distribution patterns of radiolarian species include comparison of specific makeups at different depths, interpretation of density maxima in species-specific quantitative vertical profiles, and evaluation of live vs. dead cells by means of ATP assays. ATP assays are too costly and time-consuming for routine plankton work. The other two methods yield indirect evidences, but cautious interpretation of the latter can furnish reliable information on the depth-preferences of radiolarian species.