Direct and Indirect Effects of Arsenic on the Survival and Fecundity of Estuarine Zooplankton

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Abstract
Estuarine zooplankton are resistant to relatively high concentrations of arsenate, up to 100 .mu.g .cntdot. L-1, and are not likely to be impacted directly in natural systems. Indirect impacts, however, can be much more severe. Natural phytoplankton communities are significantly inhibited by low levels of arsenate, altering species composition and succession of dominant species, affecting normal predator-prey relationships, and greatly reducing zooplankton grazing, survival, and reproductive success. Thus, an initial prediction of insignificant pollutant impact based upon direct effects would be erroneous. Both potential direct and indirect impacts and the significance of pollutant-induced changes at one trophic level to species at higher levels must be determined for aquatic systems if reliable predictions concerning pollutant impacts are to be generated.