Aquatic Sciences Meeting, Albuquerque 2001

PC12 Trophic Dynamic Studies

Date: Thursday, February 15, 2001

Location: Southwest Hall

Cowlishaw, R, J, University of Oregon, Oregon Institute of Marine Biology, Charleston, USA, rcowlish@oimb.uoregon.edu

MICROZOOPLANKTON GRAZING IN THE SOUTH SLOUGH ARM OF COOS BAY, OREGON

The grazing impact of microzooplankton on phytoplankton production was studied in the South Slough, an arm of Coos Bay, located on the south central Oregon coast. Routine sampling over a year's time showed that ciliate abundance was better correlated with the less than 5 um fraction of extracted chlorophyll than the greater than 5 um fraction (r=.78 vs. r=.05, respectively). Dilution method experiments were conducted in March and August, 1999, and March, 2000, to estimate the microzooplankton grazing impact on the production of total chlorophyll (all experiments) and of size fractions of chlorophyll (total, less and greater than 5 um; all experiments except MAR99). Significant grazing rates on total chlorophyll were measured in the MAR99 and MAR00 experiments (.24 and .32 d^-1; 21% and 27% of the initial chlorophyll standing stocks; 56% and 84% of the potential chlorophyll production d^-1, respectively). Significant grazing occurred only on the less than 5 um size fraction for the AUG99 experiment (1.4 d^-1; 76% of this fraction's initial chlorophyll standing stock; 97% of the potential chlorophyll production d^-1).

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Aquatic Sciences Meeting, Albuquerque 2001

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