ELEMENTAL AND ISOTOPIC FLUXES IN THE SOUTHERN CALIFORNIA BIGHT - A TIME-SERIES SEDIMENT TRAP STUDY IN THE SAN-PEDRO BASIN

Temporal variability in the fluxes of various elements and radionuclid es in San Pedro Basin have been estimated using week-long sediment tra p samples collected continuously from January to July 1988. Deposition in this marginal basin is controlled by seasonal changes in both uppe r ocean hydrography (i.e., upwelling) and local climate (i.e., precipi tation, runoff). The fluxes of elements derived primarily from contine ntal sources (Al, Ti, Na, and V) were highest during the winter (late January to early February) in association with the highest rainfall re corded during the study period. The flux patterns for the biologically active elements (Br, Ca, and I) are highest during the spring upwelli ng period (April-May) and correlate well with organic carbon fluxes. D ue to significant input of continentally derived Ba, the flux of this element in San Pedro Basin is dominated by terrestrial input and not b iological processes. The ultimate removal of Th-234 and Pb-210 from th e water column appears to be controlled primarily by organic carbon fl ux. However, the sources of organic carbon vary seasonally, with signi ficant terrestrial organic carbon input during the winter and predomin antly marine organic carbon during the spring and summer. This suggest s that the removal of these two radionuclides is independent of the so urce of the organic carbon. In contrast, the flux of Th-228 is control led by seasonal changes in terrigenous input.