Biomonitoring toxicity of natural sediments using juvenile Hyalella curvispina (Amphipoda) as test species: evaluation of early effect endpoints.

The utility of early effect endpoints as biomarkers of ecotoxicity of natural sediments in water-sediment static system was investigated. The particular goal was to evaluate the ecotoxicity of the sediment samples from La Choza stream, located in upper basin of the Reconquista river, the second most polluted river of Argentina. Native juveniles Hyalella curvispina were used as test organisms evaluating survival, growth, oxidative stress parameters (SOD; CAT, TBARS) and the electron transport system (ETS) activity as early toxic effect. This study used methodologies and techniques that allow the assessment of sediment pollution with a native species as test organism and provided data to discuss the viability of sublethal endpoints as tools for freshwater sediment assessment. In spring and in summer two ten-day series of whole-sediment assays were conducted simultaneously: (a) standard assays and (b) biomarkers assays. A control sediment was ran simultaneously in which no--effect on survival was measured. In summer there was a significant increase in length and biomass in both exposed and control groups. In spring an inhibitory effect on growth and an increase in oxidative damage with a concomitant rise in antioxidant defenses, was observed in animals exposed to La Choza sediment. ETS measurement indicated a significant depression of metabolic activity of amphipods exposed to contaminated sediments. The measured biomarkers represent the first record for juvenile H. curvispina exposed to polluted natural sediments under standardized laboratory conditions. The used bioanalytical tools demonstrated higher sensitivity and a more accurate assessment of the effects than those obtained by the standard tests of survival and growth. We propose their adoption in biomonitoring of freshwater sediment toxicity.