Potential impact of watercress farm discharges on the freshwater amphipod, Gammarus pulex L

The magnitude of zinc contamination in water and sediment near a watercress farm discharge in the UK was monitored. Laboratory populations of the freshwater amphipod Gammarus pulex were also exposed to Zn-laden sediment or food to assess the effects of such exposure on survival and feeding rate. Zinc concentrations were highest in stream water immediately below the discharge and did not decline steadily with distance. Elevated Zn levels were also detected in downstream sediments, but these were not acutely toxic to G. pulex over either a four- or eight-week period. Fine sediments derived from watercress beds were marginal habitats for G. pulex, and Zn contamination of food material was sufficient to cause a reduction in feeding rate.