Selenium bioaccumulation by the water boatman Trichocorixa reticulata (guerin-meneville)

The input of selenium from subsurface agricultural drainage into surface wa ter systems can result in the accumulation of toxic concentrations of selen ium in aquatic food chains. Elevated selenium concentrations in aquatic sys tems is a significant environmental problem in many areas of the United Sta tes. A laboratory investigation was conducted to determine the dominant rou te of selenium bioaccumulation by the corixid Trichocorixa reticulata, an i mportant food chain organism. The roles of waterborne and foodborne exposur e in selenium bioaccumulation were examined using 48-h bioassays. Waterborn e selenium concentrations ranged from 0 to 1,000 mu g Se/L as selenate. A m ixture of two species of blue-green algae cultured in media with selenium c oncentrations ranging from 0 to 1,000 mu g Se/L as selenate was used as a c orixid diet in the foodborne treatments. Corixids exposed to waterborne sel enate did not accumulate selenium above control concentrations. Corixids fe d algae exposed to greater than or equal to 100 mu g Se/L as selenate had s ignificantly higher selenium concentrations than control organisms. These d ata suggest that corixids may be effectively isolated from the water and se lenium accumulation is solely through dietary exposure.