Chapter 5 Abundance, Distribution, and Grazing Impact of Zooplankton on the Washington Shelf

Abstract

This chapter presents a first-order estimate of the grazing capability of zooplankton populations on the Washington shelf during summer. It reviews information on the abundance, distribution, and biomass of important grazer populations in the Oregon and Washington coastal environment. It also derives the estimates of biomass-specific grazing potential for each taxonomic grouping based on the organism size and feeding and growth rates in laboratory and field studies. Grazing-rate estimates and population-biomass distributions are combined in the chapter to provide cross-shelf estimates of community grazing potential relative to the primary production during field experiments in August 1981 and June 1982. As a test of the grazing-rate calculations, predicted rates and relationships are compared to grazing and vertical-flux rate measurements on the Washington mid-shelf during a field experiment in August 1983.