LONG-TERM AND SHORT-TERM ARSENATE TOXICITY TO FRESH-WATER PHYTOPLANKTON AND PERIPHYTON IN LIMNOCORRALS

A short-term photosynthesis test employing phytoplankton or periphyton communities was a good predictor of the concentration of arsenate that affected these microalgal communities under long-term arsenate exposure in limnocorrals. Arsenate stress changed the structure of the communities to a more tolerant species composition which was consistent with the concept of pollution-induced community tolerance (PICT). The results involving phytoplankton and periphyton in a phosphorus-limited forest lake corroborated earlier findings from the marine environment. Microalgae from the lake were, however, about one order of magnitude more sensitive than the marine communities, probably because these algal communities primarily were limited by phosphorus instead of nitrogen. The observed arsenate toxicity indicated that the natural background of arsenic may already be a structuring factor for the microalgal communities in several freshwater environments.