CONTRIBUTIONS OF THE PLANKTON COMMUNITY TO ECOSYSTEM RESPIRATION, TOMALES BAY, CALIFORNIA

This paper presents direct measurements of plankton community respirat ion for Tomales Bay, California, U.S.A., and compares these measuremen ts with water column variables. These data were used to develop a regr ession model that predicts planktonic respiration and nutrient reminer alization. Respiration was measured as change in dissolved O-2 in seal ed, dark, 300 ml bottles. There was a consistent and linear decrease i n O-2 concentrations over 35-48 h incubations. Chlorophyll a concentra tion ranged from 1 to 10 mu g chl al(-1). Bacterial counts were 2-11 x 10(6) cells ml(-1) and leucine incorporation rates ranged from 200 to 1300 pmol l(-1) h(-1) over the period May 1992-July 1993. Respiration rates were 0.16-1.91 mu mol O-2 l(-1) h(-1), with an annualized avera ge of 0.67 mu mol O-2 l(-1) h(-1). A multiple linear regression of O-2 consumption rate against the independent variables (chlorophyll conce ntration, temperature and particulate N concentration) explained 79% o f the variation in the respiration rates. Modelled plankton community respiration rates for the period January 1988 to July 1993 ranged from <0.4 to >2.0 mu mol O-2 l(-1) h(-1). Over the same period, the averag e remineralization over the period of January 1988 to July 1993 were 9 .8 and 0.6 mmol m(-2) day(-1), respectively. Even in an embayment as s hallow as Tomales Bay (mean z=3.1 m), planktonic respiration and remin eralization are greater than benthic respiration and remineralization. (C) 1997 Academic Press Limited.