ZOOPLANKTON COMMUNITY METABOLISM IN THE UPPER 200-M OF THE CENTRAL RED-SEA AND THE GULF OF ADEN

A comparative study was conducted between the central Red Sea and the Gulf of Aden during spring in February/March 1987. Zooplankton (> 100-mu-m) standing stock, determined as carbon and nitrogen content, and community respiration were measured in 2 layers: in the euphotic zone and in the underlying layer, the so-called lower epipelagic zone, down to 200 m. The euphotic zone exhibited a significantly higher biomass and respiration rate than the layer below. Standing stock and respiration in the Gulf of Aden exceeded those in the Red Sea by factors of 3 and 2 respectively (station means for the euphotic zone: 10.3 +/- 1.3 mg C m-3 and 3.4 +/- 0.6 mg O2 m-3 d-1 in the Gulf of Aden; 3.4 +/- 1.4 mg C m-3 and 2.6 +/- 0.9 mg O2 m-3 d-1 in the Red Sea). However, weight-specific respiration was highest in the Red Sea euphotic zone, amounting to an average of 0.57 +/-0.13 mg O2 mg C-1 d-1. This corresponds to a daily carbon turnover rate of 17.2 % body carbon per day whereas in the Gulf of Aden turnover averaged only 11.4 % C d-1.