Evaluation of estrogenic effects of municipal effluents to the freshwater mussel Elliptio complanata

Municipal effluents are an important source of estrogens to the aquatic env ironment. The purpose of this study was to examine the estrogenicity of mun icipal effluents to the indigenous freshwater mussel, Elliptio complanata. First, estradiol-binding sites in gonad homogenates were characterized to d etermine the binding affinity and specificity of estrogens. Mussels were ex posed to increasing concentrations of a municipal effluent for 96 h at 15 d egreesC. In another experiment, mussels were placed in cages and submerged for 62 days at 1.5 km upstream and 5 km downstream of a municipal effluent plume in the St. Lawrence River. Mussels were harvested for assessment of v itellogenin-like proteins in the hemolymph and determination of total lipid , carbohydrate and protein in the gonad. The presence of specific estrogen- binding sites was found in both male and female gonads. Binding of estradio l to cytosol proteins reached saturation, yielding a dissociation constant of 0.4 nM. Vitellogenin (Vg) levels increased significantly in both the hem olymph and the gonad after exposure to the effluent. Moreover, females appe ared to be more sensitive than males to producing Vg. Mussels exposed in si tu to contaminated surface waters had higher levels of Vg at the downstream site, again, females had higher levels of Vg than did males. On the other hand, lipid and sugar levels in male gonads were significantly increased at the downstream site. Moreover, mussels at the downstream site had decrease d shell growth length and increased total and soft tissue weights. We concl ude that municipal effluents contain bio-available xenoestrogens at levels sufficient to elicit effects in freshwater mussels. (C) 2001 Elsevier Scien ce Inc. All rights reserved.