title: An evaluation of mixed species in-situ and ex-situ feeding assays: the altered response of Asellus aquaticus and Gammarus pulex.
abstract: Mixed species feeding assays were undertaken with pollution sensitive (Gammarus pulex) and tolerant (Asellus aquaticus) macro-invertebrates during August 2003 and April 2004. The purpose of this study was to establish if a test animals' response is comparable during in-situ and ex-situ toxicity tests. Seven test sites were established along an undisclosed stream, which received leachate discharge from an unlined, disused UK landfill site. Sampling points A-B were upstream of the contamination, C was adjacent to the influx and D-G were downstream of the leachate discharge (at 100 m intervals). During the in-situ and ex-situ tests, 2-week-old male laboratory bred A. aquaticus and G. pulex were used as test animals. The animals were transplanted to the seven sampling points for the duration of the in-situ tests, whilst water samples from each site were returned to the laboratory for ex-situ testing. The results show that the animals' mortality and feeding rates followed similar trends during the in-situ and ex-situ tests, however, the animals' response was amplified during the in-situ tests. It was also observed that the effects were greater in April, compared to August that may be attributed to a higher frequency of rainfall during spring, which could have flushed a greater proportion of the contaminant load from the waste mass and as a consequence, higher levels of pollution may have leached into the stream from the landfill site. The study, therefore, concludes that in-situ toxicity tests are a more precise monitoring technique, in comparison to ex-situ assays.
authors.affiliation: School of Civil Engineering and the Environment, University of Southampton, Highfield, UK. M.C.Bloor@soton.ac.uk
authors.forename: M C
authors.initials: MC
authors.lastname: Bloor
authors.forename: C J
authors.initials: CJ
authors.lastname: Banks
mesh_terms: D033304:Amphipoda / Q000187:drug effects*; D000821:Animal Feed; D000818:Animals; D033321:Isopoda / Q000187:drug effects*; D008297:Male; D013997:Time Factors; D018675:Toxicity Tests; D014873:Water Pollutants / Q000633:toxicity*
chemical_list: D014873:Water Pollutants