THE LETHAL AND SUBLETHAL RESPONSES OF GAMMARUS-PULEX TO STRESS - SENSITIVITY AND SOURCES OF VARIATION IN AN INSITU BIOASSAY

The feeding rate and mortality of the freshwater amphipod Gammarus pulex L., a common benthic detritivore, were measured during four trials of an in situ bioassay. The Gammarus pulex were deployed in a factorial experiment designed to assess the effects of water quality (three stations), test population (two sources), and test operator (two laboratories). Stations were selected above and below a domestic sewage treatment works, a sewage treatment works processing domestic and industrial waste, a quarry, and a pulp mill. Feeding rate appeared to have potential as an indicator of water quality, but the source of the test population and the laboratory performing the measurements both significantly influenced the results.