Relating selenium concentrations in a planktivore to selenium speciation in lakewater.

We measured selenium (Se) speciation in the waters of 16 lakes located near two major metal smelters and compared it to Se concentrations in a potential biomonitor, the planktivorous insect Chaoborus. We used this sentinel because planktonic algae and crustaceans, which are lower in the trophic chain leading to Chaoborus, are more difficult to separate and identify to species, whereas many fish species are not obligate planktivores. Percentages of selenate and organo-Se were generally higher in acidic lakes, whereas those of selenite were usually greater in alkaline waters. Chaoborus Se concentrations varied widely among lakes and, with the exception of a single high-sulfate lake, were significantly and highly correlated with those of dissolved organo-Se plus selenate (Se(VI)). We suggest that Chaoborus larvae would be highly effective for monitoring the Se-exposure of planktonic food webs in lakes.