Simultaneous assessment of environmental impact on condition and trace metal availability in zebra mussels Dreissena polymorpha transplanted into the Wiltz River, Luxembourg. Comparison with the aquatic moss

Caged freshwater zebra mussels (Dreissena polymorpha), placed for 3 months at 10 sites along the Wiltz river, were examined periodically for mortality, re-attachment success and dry weight. Tufts of the aquatic moss Fontinalis antipyretica were initially introduced at the sites and every were sampled to monitor separately the changes in trace metals in the river. The dried plants and soft mussel tissue were digested in nitric acid and analysed for heavy metals by atomic absorption spectrophotometry. The major anthropogenic impacts on the river were reflected in mussel condition and trace metal accumulation. Metal concentrations in soft tissue were affected by ambient metal concentration, exposure time and change in body weight. The last source of variation was eliminated by the calculation of metal body burdens. Moss and mussels accumulated metals to different degrees: chromium and tin were hardly detected by moss. An exposure time of 2 months was required for the mussels to reflect the condition of the river accurately. There are 40 references.