Preliminary results of biomarker responses in zooplankton of brackish environments

Zooplankton is an essential component of the food chains of marine and brackish environments. Ecotoxicological risk to zooplankton, evaluated by the biomarker approach, can be used as an early warning signal of risk to the health of marine ecosystems. The aim of this project is to evaluate the application of certain biomarkers in zooplankton. In the present paper, laboratory and field studies were performed with the copepods Acartia margalefi, Acartia latisetosa and the mysid Siriella clausi. Acetylcholinesterase activity (AChE) was determined in homogenates of whole organisms. Mean AChE activity was 10.05 micromol min g(-1) for A. margalefi, 3.30 micromol min g(-1) for A. latisetosa and 79.70 micromol min g(-1) for S. clausi. A. margalefi and S. clausi also showed a linear increase in enzyme activity with increasing concentrations of samples. Preliminary laboratory work was also carried out with specimens of A. latisetosa, which were exposed to an organophosphorus insecticide (parathion). Moderate inhibition of AChE (19%) with respect to controls was observed. AChE activities were two orders of magnitude higher in the zooplankton than in hemolymph samples of the decapod Carcinus aestuarii (Fossi et al., 1996) indicating that these species have a high metabolic rate, which makes them suitable for biomarker studies.