SUBLETHAL EFFECTS OF CUPRIC ION ACTIVITY ON THE PHOTOTAXIS OF 3 CALANOID COPEPODS

Using wavelengths near maximal photosensitivity, phototactic responses of two estuarine calanoid copepods (Acartia tonsa, Acartia hudsonica) and one nearshore, neritic copepod (Temora longicornis) were measured after 24 h exposures to sublethal concentrations of free cupric ions. A nitrilotriacetate-trace metal ion buffer system was used to control the free cupric ion activity (pCu = negative log of the free cupric i on activity), which determines organismic response. All three species exhibited positive phototaxis at pCu almost-equal-to 13.0 reported for unpolluted surface sea waters and estuarine waters. As cupric ion act ivity increased, percent positive phototactic response decreased, indi cating a strong sublethal effect of free cupric ions on photobehavior. Changes in photobehavior occurred at cupric ion activities that have been reported for many estuaries and coastal waters near urban and ind ustrialized areas. Temora longicornis was much less phototactically se nsitive than the two estuarine species. It also exhibited phototactic sign switching as pCu changed.