Chronic effect of No. 2 fuel oil on population dynamics of harpacticoid copepods in experimental marine mesocosms

Abstract

Harpacticoid copepods in free-standing mesocosms were exposed to No. 2 fuel oil at a concentration of 190 pg 1-' for 168 d, and then allowed to recover for 64 d. The harpacticoid community was composed of 9 species. Tisbe sp., Rhynchothalestris mfocincta, Dactylopodia vulgaris and Alteutha rara were seldom present in the mesocosms, whereas Longipedia americana, Microarthridon littorale, Ameiropsis brevicornis, Thompsonula hyaenae and Enhydrosorna baruchi were present throughout the sampling period. Chronic effects of oil additions on the population dynamics of 2 of the 5 regularly occurring species, A. brevicornis and T. hyaenae, were not statistically discernible. L. arnericana and M. littorale were adversely affected by the oil additions and their populations did not recover. E. baruchi abundances remained fairly constant in the control and experimental tanks throughout the oil additions, but bloomed in the experimental tanks during the recovery period.