Assessing sublethal levels of sediment contamination using the estuarine amphipod Leptocheirus plumulosus

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Abstract
Recent emphasis on the incorporation of sublethal end points into sediment toxicity test methods follows the realization that acute lethality tests may not provide sufficient sensitivity for predicting subtle ecological effects of sediment contamination. To this end, a partial life‐cycle test with the amphipod Leptocheirus plumulosus Shoemaker was evaluated for solid‐phase testing of contaminated estuarine sediments. Initially, juvenile and adultLeptocheirus plumulosus and the amphipod Hyalella azteca were exposed to gradients of chemical contamination prepared by diluting field‐collected contaminated sediment with texturally similar reference sediment. Ten‐day exposure results indicate juvenile Leptocheirus plumulosus is more sensitive than adult Leptocheirus plumulosus and Hyalella azteca, with significant mortality of juvenile Leptocheirus plumulosus occurring in sediment diluted to 12.5% of the adult lowest‐observed‐effect concentration (LOEC). Long‐term exposure (30 d) of juveniles to dilutions of the acute juvenile LOEC shows significant effects on growth in sediment concentrations below the lethal threshold. Effects on reproductive end points (proportion of gravid females, number of young) parallel growth effects. Evaluation of nontoxicant experimental variables indicates significant effects of temperature and feeding regime on sensitivity of juvenile Leptocheirus plumulosus to contaminated sediment.