Nicholas S. Fisher Brian A. Bergamaschi Allison C. Luengen 2012 Dissolved organic matter (DOM) significantly decreased accumulation of methylmercury (MeHg) by the diatom <i>Cyclotella meneghiniana</i> in laboratory experiments. Live diatom cells accumulated two to four times more MeHg than dead cells, indicating that accumulation may be partially an energy-requiring process. Methylmercury enrichment in diatoms relative to ambient water was measured by a volume concentration factor (VCF). Without added DOM, the maximum VCF was 32 x 10⁴, and the average VCF (from 10 to 72 h) over all experiments was 12.6 x 10⁴. At very low (1.5 mg/L) added DOM, VCFs dropped by approximately half. At very high (20 mg/L) added DOM, VCFs dropped 10-fold. Presumably, MeHg was bound to a variety of reduced sulfur sites on the DOM, making it unavailable for uptake. Diatoms accumulated significantly more MeHg when exposed to transphilic DOM extracts than hydrophobic ones. However, algal lysate, a labile type of DOM created by resuspending a marine diatom in freshwater, behaved similarly to a refractory DOM isolate from San Francisco Bay. Addition of 67 &mu;M L-cysteine resulted in the largest drop in VCFs, to 0.28 x 10⁴. Although the DOM composition influenced the availability of MeHg to some extent, total DOM concentration was the most important factor in determining algal bioaccumulation of MeHg. application/pdf 10.1002/etc.1885 en Wiley Dissolved organic matter reduces algal accumulation of methylmercury article