Invertebrate assemblages and trace element bioaccumulation associated withconstructed wetlands

Invertebrate assemblages were studied in eight monoculture wetland mesocosm s constructed for wastewater treatment. Low concentrations of dissolved oxy gen (D.O.) were measured in bulrush mesocosms while higher concentrations o f D.O. were measured in open water mesocosms containing submerged pond-weed s. Invertebrate taxa richness was positively related to D.O. concentrations that were, in turn, related to vegetation communities. Reference wetland s ites contained a variety of plant species along with extensive open water a reas. Invertebrate taxa richness was greater at reference sites than in any wastewater mesocosm. Invertebrate samples from the wastewater mesocosms an d reference sites were analyzed for five trace elements. While the concentr ations of aluminum, arsenic, mercury, and silver were below values harmful to wildlife, the concentrations of selenium reached levels of moderate conc ern on one occasion. Data from this study suggest that selenium bioaccumula tion by invertebrates may be related to the type of vegetation community or detrital habitat type. Wetlands designed for invertebrate production for w aterfowl should take into account the potential for low D.O. concentrations and trace element bioaccumulation associated with vegetation community typ es.