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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. |
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