In situ assays can allow more realistic pollutant exposure scenarios to be studied than laboratory simulations. In terms of sublethal responses, feeding inhibition is recognised as a sensitive indicator of exposure to pollutants. In situ assays based on feeding depression can be powerful ecotoxicological tools that can link physiological organism-level responses to population and/or community-level effects. Amphipods are traditional target species for toxicity tests due to their high sensitivity to contaminants, availability in the field and ease of handling. However, cost-effective in situ assays based on feeding depression are not yet available for amphipods that inhabit estuarine ecosystems. The aim of this work was to assess a short-term in situ assay based on postexposure feeding rates on easily quantifiable food items with an estuarine amphipod.
Experiments carried out under laboratory conditions determined that with juvenile Echinogammarus marinus as the target individual. When 60 Artemia nauplii (as prey) were provided per individual for a period of 30 minutes in dark conditions, feeding rates could be easily quantified (Fig. 1).
As an endpoint, postexposure feeding inhibition in E. marinus was more sensitive to cadmium (Cd) contamination than mortality (0.66 vs 0.93 mg Cd/L Cd; 48-h EC50 vs 48-h LC50, respectively). Assay calibration under field conditions demonstrated the relevance of sediment particle size in explaining individual feeding rates in uncontaminated water bodies. An evaluation of the 48-h in situ bioassay based on postexposure feeding rate indicated that it is able to discriminate between unpolluted and polluted estuarine sites (Fig. 2).
This in situ assay using the amphipod E. marinus based on postexposure feeding appears to have potential as a tool for environmental estuarine assessment. By using this target species, a new short-term, sublethal, in situ toxicity assay based on 48 h of exposure followed by a 30 min postexposure feeding period is suggested. This adds to other similar assays that are available for estuarine environments, which involve the use of the polychaetes Hediste diversicolor and Neanthes arenaceodentata, the isopod C. carinata , the gastropod Hydrobia ulvae and the crab C. maenas . A battery of such bioassays, able to cover a wide range of estuarine ecosystem functions and trophic levels, is therefore now available and ready to use in monitoring programmes (alongside more conventional community based approaches). Ecotoxicological tools such as this one are considered of benefit if we are to obtain more accurate and effective ecological quality assessments – something, which is considered essential within the EU’s Water Framework Directive.
Mónica Martinez-Haro, Pelayo Acevedo, Antonia Juliana Pais-Costa, Mark A. Taggart, Irene Martins, Rui Ribeiro, João Carlos Marques. 2016. Assessing estuarine quality: A cost-effective in situ assay with amphipods. Environmental Pollution 212, 382-391 DOI: 10.1016/j.envpol.2016.01.071 – http://authors.elsevier.com/a/1SX2azLNSGMsl