Effect of Clean and Polluted Groundwater on Daphnia Reproduction and Development

Background/Need:
There is a need for an efficient and effective whole-animal screen for ecological effects of pollutants (see Table 1). Previous work in our lab has focused on herbicides and vertebrate hormones. Several of these chemicals changed normal Daphnia development and sex determination, at concentrations found in groundwater. The current proposed research focuses on laboratory assays of low-level concentrations of common-use insecticides that have been reported to be contaminants of groundwater. Information on insecticide effects will contribute toward our evaluation of the Daphnia reproduction assay. This assay has been developed and used successfully in the lab for a number of chemical contaminants. Preliminary results suggest that it is crucial to survey insecticides. Our assays provide information on “contamination,” (whether due to parent compounds, breakdown products, and chemical mixtures) because we look at the whole-animal response. This is an important feature, because there are so few cost-effective assays that can detect sublethal effects on whole organisms. Our ultimate goal is to establish the Daphnia development and reproduction assays as a surrogate, cost-effective bioassay system for risk assessment. Our results suggest these assays do have value, because Daphnia are sensitive to ambient concentrations of contaminant herbicides, and because Daphnia respond in characteristic ways to some vertebrate hormones such as thyroxine and some steroid hormones.

Objectives:
The project objective was to characterize effects of common-use insecticides classified as endocrine disruptors on development and sex determination of Daphnia magna, using well-established short- (six day) and long-term (30 day) life-table type assays. The endpoints include: growth in length, molting frequency, and population growth rate fecundity and sex ratio deviations from normal morphology in neonates and adults.