CONICET | Buscador de Institutos y Recursos Humanos

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 Nin~o conditions.

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