Vertical migration of infaunal invertebrates in response to dosing with secondary treated sewage effluent: a microcosm experiment

Short-term experiments testing behaviouralresponses to a toxicant are liable to besensitive indicators of the potential effectsof a pollutant and allow predictions abouthabitat preferences of organisms in the field.We have undertaken short-term microcosmexperiments with intact assemblages ofintertidal invertebrate infauna andinvestigated the responses of these assemblagesto dosing with a secondary treated sewageeffluent. Infaunal assemblages were taken fromsites that differed in their proximity toeffluent discharges and in recent exposure todisturbances. We observed a range of responsesto different dose treatments during theseexperiments with differential migration intothe water column by the corophiid amphipodCorophium insidiosum and changes in depthdistribution within the sediment by severalannelid taxa. We discuss these results withrespect to potential field responses followingexposure to treated sewage effluents andbiological monitoring programs.