Radiolarian vertical distribution patterns across the southern California Current.

KLING, STANLEY; BOLTOVSKOY DEMETRIO

DEEP-SEA RESEARCH. PART 1. OCEANOGRAPHIC RESEARCH PAPERS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: New York; Año: 1995 vol. 42 p. 191 - 231

0967-0637

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 November‑December 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 depth‑intervals were defined in the upper 300 m: 0‑50 m, 100 m, and 200‑300 m. Between‑station similarities in the specific makeups of these layers, however, were low. Thirty‑nine taxa had peak abundances below 300 m at one or more stations; 11 of these are probably deep‑water forms. Although in terms of individuals per liter of water filtered, upper‑layer taxa are noticeably more abundant than deep species, the latter have much more extended depth‑ranges, which might significantly enhance their sedimentary output. The inshore and oceanic stations shared very similar, warmer‑water radiolarian assemblages in the uppermost 25 m, whereas the intermediate station was dominated by colder‑water forms at those depths. Below 50 m, however, the inshore station had enhanced proportions of deeper‑ and colder‑water 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 cold‑water 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 deeper‑water radiolarians at this site. Analyses of the affect of such vertical patterns on paleoceanographic interpretations stress the importance of the signal of "environmentally neutral" deep‑living species, as well as that of shells produced in the near‑surface layers of distant areas and transported at depth to the region of the study.