0 1984, by the American Society of Limnology Oceanography, Inc. Utilization of detritus by the copepod, Acartia tonsa1

Ingestion, survivorship, and growth experiments were conducted with the marine Calanoid co-pepod, Acartia tonsa, various concentrations of the diatom, Thalassiosira weissjlogii, and detritus derived from the macrophyte, Thalassia testudinum. Copepod ingestion rates of detritus increased with detritus concentration from ~50 to> 1,700 pg Celiter-I. Copepod survival in detritus suspensions was significantly greater than in filtered seawater controls. The instantaneous mortality coefficient, z, of A. tonsa was a linear (negative) function of the diatom concentration (r2 = 0.783 1). When T. weissfrogii suspensions were supplemented with detritus (I,000 pg C.liter-l), the copepod instantaneous mortality rate decreased (0.3002-O. 1362 in 50 pg Caliter- ’ T. weissj’logii; 0.1345-0.0406 in 200 pg C-liter-l T. weissflogii). The growth rate of A. tonsa was a linear function of diatom concentration (r2 = 0.8816). When the diatom sus-pensions were supplemented with T. testudinum detritus, the growth rate of the copepod increased. Thalassiosira weissfrogii contained 12 x the protein, 8 x the fatty acids, and a greater amount and diversity ofamino acids and polyunsaturated fatty acids per unit dry weight than T. testudinum detritus. Although A. tonsa could not grow from egg to adult on a detrital diet, T. testudinu