Effects of elevated nitrate concentration on mortality, growth, and egestion rates of Gammarus pseudolimnaeus amphipods.

There is relatively little known about nitrate toxicity in aquatic invertebrates, especially sublethal effects of elevated nitrate. We exposed the amphipod Gammarus pseudolimnaeus to elevated nitrate concentrations (up to 128 mg NO(3)-N/L) in a laboratory experiment and measured mortality, growth rates, egestion rates, molting, and C:N ratio. Nitrate concentration did not affect mortality, egestion rate, molting, and C:N ratio. Amphipod growth decreased slightly with increasing nitrate concentration based on the results of a linear regression, but a one-way ANOVA suggested that mean growth rates were not different among nitrate treatments. We suggest that additional research is needed on the sublethal effects of elevated nitrate concentration on aquatic invertebrates, particularly for those taxa that have demonstrated sensitivity to other chemical stressors.