Hur påverkas kvicksilvermetylering i sjöar av det mikrobiella samhällets artsammansättning
Tidsperiod: 2012-03-01 till 2014-02-28
Projektledare: Andrea Garcia Bravo
Budget: 1 716 000 SEK
Elevated levels of mercury (Hg) in the environment is of concern for humans because of high toxicity even at low concentrations. Hg emitted to the environment is mainly inorganic whereas methyl mercury (MeHg) accumulate in aquatic organisms. Previous studies have shown that some sediment bacteria are able to methylate Hg and there is also evidence of bacterial Hg methylation in hypolimnetic waters. Still MeHg levels vary extensively among lakes, even when the overall Hg levels are similar. As only a subset of the bacterial community perform mercury methylation, we hypothesize that bacterial community composition controls Hg methylation and accordingly that much of the variance in Hg methylation can be predicted from the bacterial community assemblages in sediment and hypoliminion as analysed by 454 pyrosequencing. The following broader questions will be addressed: Can bacterial community composition explain variation in MeHg levels and mercury methylation rates in anoxic hypolimnetic waters in stratified freshwater lakes? Does microbial use of alternative electron acceptors in anoxic hypolimnia or anoxic sediments enhance mercury methylation and is this coupled to bacterial community shifts? Both of these questions will be studied in stratified lake ecosystems and in experimental microcosms subjected to experimental manipulations of electron acceptor availability, contrasting microbial inocula and variation in substrate availability.