Mills R Brad, Bodek Tamar, Paterson Andrew M, Blais Jules M, Lean David R S
Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, 30 Marie Curie Street, Ottawa, Ontario, Canada K1N 6N5.
Sci Total Environ. 2009 Aug 1;407(16):4696-702. doi: 10.1016/j.scitotenv.2009.03.034. Epub 2009 May 17.
The concentration of methylmercury (MeHg) in aquatic ecosystems is the net result of the highly dynamic abiotic and biotic processes of mercury methylation and demethylation. In this study, we conduct an examination of the net fluvial loading of methylmercury (MeHg(Net)=MeHg(Watershed)-MeHg(Lake outflow)) across a 3 year time frame in both a dystrophic lake and an oligotrophic lake. A significant portion of MeHg(Net) variance in both lakes could be attributed to a seasonal pattern (11.4%, p=0.009; oligotrophic, and 27.0%, p<0.0001; dystrophic) which in both cases, was most correlated with air temperature. The dystrophic lake appeared to be a net source of methylmercury (MeHg(Net)=-1.9+/-0.3 mg MeHg d(-1)) while the oligotrophic lake appeared to be a net sink (MeHg(Net)=0.4+/-0.2 mg MeHg d(-1)), indicating that there was net methylation in the dystrophic lake and net demethylation in the oligotrophic lake. Higher MeHg loading to the lakes occurred during the summer and between seasons there was a difference in MeHg(Net) of 1.1+/-0.3 mg MeHg d(-1) and 3.1+/-0.6 mg MeHg d(-1). Seasonal patterns of MeHg(Net) in the oligotrophic lake lagged behind the dystrophic lake by 39 days. The short term variation in MeHg(Net) was dominated by precipitation (t=2.73, p=0.008; dystrophic, t=2.53, p=0.017; oligotrophic).
水生生态系统中甲基汞（MeHg）的浓度是汞甲基化和去甲基化这两个高度动态的非生物和生物过程的净结果。在本研究中，我们在一个贫营养湖和一个富营养湖的3年时间范围内，对甲基汞的净河流负荷（MeHg(Net)=MeHg(流域)-MeHg(湖泊流出)）进行了考察。两个湖泊中MeHg(Net)差异的很大一部分可归因于季节性模式（贫营养湖为11.4%，p = 0.009；富营养湖为27.0%，p < 0.0001），在这两种情况下，季节性模式与气温的相关性最强。富营养湖似乎是甲基汞的净源（MeHg(Net)= -1.9±0.3 mg MeHg d(-1)），而贫营养湖似乎是净汇（MeHg(Net)= 0.4±0.2 mg MeHg d(-1)），这表明富营养湖存在净甲基化，贫营养湖存在净去甲基化。夏季湖泊的甲基汞负荷较高，季节之间MeHg(Net)的差异为1.1±0.3 mg MeHg d(-1)和3.1±0.6 mg MeHg d(-1)。贫营养湖MeHg(Net)的季节性模式比富营养湖滞后39天。MeHg(Net)的短期变化主要受降水量影响（富营养湖：t = 2.73，p = 0.008；贫营养湖：t = 2.53，p = 0.017）。
