SELENIUM UPTAKE BY LARVAL CHIRONOMUS-DECORUS FROM A RUPPIA-MARITIMA-BASED BENTHIC DETRITAL SUBSTRATE/

Elevated levels of selenium have led to the contamination of several a quatic ecosystems. Much of the selenium contamination has resulted fro m agricultural irrigation and drainage of seleniferous soils. Disposal of selenium contaminated drainwater in evaporation ponds has led to s elenium bioaccumulation and toxicity in waterfowl and shorebirds using these ponds. Studies have demonstrated that it is a seleno-amino acid that causes the observed toxicity. However, selenate is the dominant form of selenium in agricultural drainwater, and the biotransformation of selenate into seleno-amino acids has been shown to be greatly limi ted relative to the more reduced selenium species. We hypothesize that it is in the benthic zone, where the reducing environment facilitates conversion of selenate to selenium forms more conducive to biotransfo rmation, that most biotransformation and subsequent bioaccumulation of seleno-amino acids takes place, and that movement of selenium into th e benthic-detrital food chain is a key pathway leading to selenium bio accumulation. This hypothesis was investigated by conducting laborator y benthic-detrital food chain experiments using the common evaporation pond macrophyte Ruppia maritima as the benthic-detrital substrate. La rval Chironomus decorus were reared on the contaminated Ruppia substra te, and the resulting bioaccumulation and toxicity in the larvae were determined.