Effects of cupric and zinc ion activities on the survival and reproduction of marine copepods

The toxicity of copper and zinc to the estuarine copepod Acartia tonsa and to the two diatom food species Thalassiosira pseudonana and T. weissflogii was measured in nitrilotriacetate-trace metal ion buffer systems at 25 S. Overall, A. tonsa appeared to be more sensitive to cupric and zinc ion activity than either of the diatoms; however, its sensitivity varied among the different life stages examined. Adult survival was not affected within the zinc ion activity range 10^-11 to 10^-8 M and cupric ion activity range 10^-13 to 10^-11 M over a 96-h period, but a cupric ion activity of 10^-10 M caused total mortality of adults within 72 h. Egg-laying rate was most sensitive to zinc, and was reduced at zinc ion activities 10^-10 M. Naupliar survival after 96 h was reduced by zinc ion activities 10^-8 M and by cupric ion activities 10^-11 M, and was reduced to zero at a zinc ion activity of 10^-7 M and at a cupric ion activity of 10^-10.5 M. In an interspecies comparison of 96-h adult survival, Centropages typicus was more sensitive to copper and zinc than A. tonsa and the survival of Labidocera aestiva was dependent on the ratio of cupric to zinc ion activity. A comparison of our results with estimates of zinc and cupric ion activities in estuaries suggests that ionic activities of these metals are high enough in some polluted estuaries to affect the survival and reproduction of copepods.