Sublethal effects of cupric ion activity on the grazing behaviour of three calanoid copepods

This research (1) characterized the effects of sublethal cupric ion activities on the grazing behavior of two estuarine copepods (Acartia tonsa, Acartia hudsonica) and one nearshore, neritic copepod (Temora longicornis) and (2) compared the sensitivity of short-term sublethal behavioral assays with that of longer-term acute toxicity tests. A nitrilotriacetate-trace-metal-ion buffer system at 27‰. S was used to quantify and control the free cupric ion activity. Acute toxicity tests were used to determine the mortality of A. tonsa and T. longicornis over 72 h within the approximate cupric ion activity range of 10−13 to 10−9.5 M. 24 h survival was not affected within the approximate cupric ion activity range of 10−13 to 10−9.7 M, the range used for subsequent grazing activity experiments after 24 h exposure to Cu. Grazing activity was significantly diminished at cupric ion activities of ≈ 10−10 M for A. tonsa and T. longicornis, and at ≈ 10−11 M for A. hudsonica. A hormetic pattern of response in feeding activity was observed with A. tonsa and T. longicornis. Grazing activity was found to be a sensitive measure of sublethal Cu stress compared with the acute toxicity tests. Grazing activity was affected at environmentally relevant cupric ion activities.