Aquatic Sciences Meeting, Albuquerque 2001

CS37 Zooplankton

Date: Wednesday, February 14, 2001, Time: 2:00:00 PM

Location: Aztec

Gewant, D, S, San Francisco State University, San Francisco, USA, dgewant@sfsu.edu

Bollens, S, M, Moss Landing Marine Laboratories, Moss Landing, USA, sbollens@mlml.calstate.edu

MACROZOOPLANKTON AND MICRONEKTON OF THE SAN FRANCISCO BAY: EFFECTS OF EL NINO/LA NINA ON ABUNDANCE AND COMMUNITY COMPOSITION

The objective of this study is to address possible changes in the abundance and community composition of macrozooplankton and micronekton in San Francisco Bay during the 1997-1999 El Nino/La Nina. Nighttime Methot trawls (4.0m2/3mm mesh) were deployed monthly at six stations spanning South, Central and North San Francisco Bays from April, 1997 to December, 2000. A total of 18 invertebrate and 35 fish species were caught. Crangon franciscorum and Engraulis mordax were the most abundant species collected, with large catches of Pleurobrachia bachei and Synidotea laticauda. Significant differences in community composition of invertebrates and fishes were exhibited, with 1998 showing the greatest taxa richness during spring months. Significant seasonal and interannual variations in abundances were also recorded, with marked increases in invertebrates during 1998 and subsequent decreases in 1999. Bollens (2000) provided evidence that the greater freshwater-runoff during 1998 associated with El Nino led to greater water column stability and thus higher phytoplankton and zooplankton biomass. We hypothesize that this fueled production of the pelagic food web, and led to higher abundances of macrozooplankton and micronekton during El Nino.

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Aquatic Sciences Meeting, Albuquerque 2001

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