PM19 Field-Based Effects Measures
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(PM292) An estuarine sediment in situ toxicity assay with polychaetes (Hediste diversicolor) based on postexposure feeding.

Moreira, S1, 2, Moreira-Santos, M3, Guilhermino, L1, 2, Ribeiro, R3, 1 CIIMAR - Centro Interdisciplinar de Investigação Marinha e Ambiental, Porto, Portugal2 ICBAS - Instituto de Ciências Biomédicas de Abel Salazar, Porto, Portugal3 IAV - Instituto do Ambiente e Vida, Coimbra, Portugal

ABSTRACT- This study aimed at developing and evaluating the suitability of a short-term sublethal in situ toxicity assay for estuarine sediments, with the Polychaeta Hediste diversicolor, based on postexposure feeding. Four specific objectives were delineated: (1) to develop a methodology for quantifying postexposure feeding rates of H. diversicolor, (2) to investigate the sensitivity of the postexposure feeding response, by comparing postexposure feeding rates with sublethal (growth) and lethal endpoints, after copper exposure, (3) to determine the influence of several environmental conditions (salinity, temperature, substrate, food availability, light) during exposure on postexposure feeding, and (4) to evaluate the in situ assay by deploying it at reference and contaminated Portuguese estuaries. Nauplii of Artemia fransciscana were found to be a suitable food for a rapid and precise quantification of H. diversicolor postexposure feeding rates. The 48-h LC50 of copper was 240 g/L, whereas the 48-h feeding IC50 and the 20-d growth IC50 where much lower and differed by a factor of 2, 51.9 and 25.38 g/L of copper, respectively. Thus, postexposure feeding was confirmed to be a sensitive response, valuable to be used as an assay endpoint. From all exposure conditions investigated, only temperature and salinity were found to significantly influence postexposure feeding, which required the use of mathematical models to allow the comparison of feeding rates across field sites. High organism recovery (88.9-100%) was obtained in the in situ assay and postexposure feeding was significantly depressed (16.7-89.9%) at all contaminated sites relatively to reference sites. Therefore, the in situ assay with H. diversicolor was shown to be a toxicity tool with potential to be routinely employed in estuarine sediment toxicity assessments.

Key words: sediment toxicity, in situ assay, postexposure feeding, Hediste diversicolor

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