? 2003, by the American Society of Limnology and Oceanography, Inc. Greedy algae reduce arsenate

Algae reduce and methylate arsenate, producing arsenite (As(III)) when the growth rates are high and dimethy-larsinic acid (DMA) when the growth rates are low. In lakes, this leads to high As(III) concentrations in the early stages of spring and fall blooms and high DMA concentrations in the summer. We hypothesize that under phosphorus (P)-limited conditions, which usually exist in the summer, algae take up phosphate (PO,) and, because of similar chemical characteristics, As(V) as well. Inside the cell, As(V) is reduced to As(III), methylated to monomethylar-sonic acid (MMA) and DMA, and then excreted. However, under non-P-limited conditions, which exist in the early stages of blooms, algae up-regulate their PO, transport system to take up excess P, a phenomenon known as luxury uptake. Since As(V) is taken up by the PO4 transport system, As(V) uptake also increases at this time. Within th