Utility of a Full Life-Cycle Copepod Bioassay Approach for Assessment of Sediment-Associated Contaminant Mixtures

We compared a 21 day full life-cycle bioassay with an existing 14 day partial life-cycle bioassay for two species of meiobenthic copepods, Microarthridion littorale and Amphiascus tenuiremis. We hypothesized that full life-cycle tests would better simulate chronic exposures to copepods and provide more sensitive and realistic information about contaminant effects on growth of copepod populations. Copepods were exposed to sediments from two sites, non-contaminated North Inlet Estuary (NIE), SC (USA), and highly contaminated Shipyard Creek (SYC), SC, and measured for lethal and sublethal test points. Fourteen and 21 day bioassays showed similar negative effects in SYC sediments for both species. Survival and reproductive success were higher in the 14 day than in the 21 day bioassay for both species, in both sediment types. The lower 21 day overall response was not indicative of enhanced bioassay sensitivity. The 14 day bioassay provides sufficient f1 generation information to detect negative population level responses to contaminant mixtures.