Mercury concentrations in fish and invertebrates of the Finger Lakes in central New York, USA.

Deleterious health effects in humans and wildlife are associated with the consumption of fish contaminated by mercury (Hg). This study was conducted to assess Hg concentrations in biota of the Finger Lakes (New York, USA), a region where fisheries are important for the economy but where no assessment of the drivers of food web Hg dynamics exists to date. Additionally, this region is of interest for the study of Hg bioaccumulation because of the importance of agricultural land cover, which can affect lake trophic status and thus the bioavailability of methyl Hg (MeHg). The study objectives were to (1) assess if fish Hg concentrations were of concern to humans and wildlife, (2) determine if differences in biota Hg concentrations exist among lakes, and (3) assess models developed for New York State as predictors of present day Finger Lakes fish Hg concentrations. Exploratory analyses were also conducted to assess predictors of fish Hg concentrations using lower trophic level MeHg concentrations, water quality, and lake and land cover characteristics. Fish concentrations were above the EPA criterion (300 ng/g wet weight, ww) in 24% of fish, but only Walleye (Sander vitreus) from Owasco Lake exceeded New York State Department of Health consumption guidelines (1000 ng/g ww). The threshold indicating biological changes within fish (500 ng/g ww) was exceeded in 11% of the individuals sampled. Significant differences were found among lakes for all fish species except Largemouth Bass (Micropterus salmoides). Notably, Lake Trout (Salvelinus namaycush) had significantly lower Hg concentrations in Cayuga Lake compared to other Finger Lakes. This trend was not mirrored in the lower food web, as benthic invertebrates had higher MeHg concentrations in Cayuga Lake. Using models developed for New York State in 2003-2005, observed concentrations in 90% of fish were different (±200 ng/g ww) than expected. Findings from this study suggest Hg dynamics in the Finger Lakes require consideration of fish age, growth rates, and food web structure to accurately predict fish Hg concentrations among lakes.

Mercury bioaccumulation in stream food webs of the Finger Lakes in central New York State, USA.

Studies of mercury (Hg) bioaccumulation in streams draining both forested and agricultural watersheds are not common. Sixteen streams were sampled in the Finger Lakes region in central New York State with a mean agricultural land cover of 48%. Stream fish (Blacknose Dace, Rhinichthys atratulus, an invertivore; and Creek Chub, Semotilus atromaculatus, an omnivore) were collected and analyzed for total Hg (THg), and macroinvertebrates and periphyton were collected and analyzed for methylmercury (MeHg) determination. The effect of water chemistry, land cover, and macroinvertebrate MeHg was assessed as predictors of fish Hg concentrations. Blacknose Dace had significantly higher THg concentrations compared to Creek Chub (229 ng/g vs. 195 ng/g dry weight, respectively), and predatory and omnivorous macroinvertebrates (i.e., Perlidae and Cambaridae) were found to have significantly higher MeHg concentrations compared to other functional feeding groups. Mixed effects models identified macroinvertebrate MeHg concentrations as predictors of stream fish THg concentrations. Partition modeling found fish total length and total suspended solids predicted Blacknose Dace with 'High' vs 'Low' Hg (≥ or < 90 ng/g wet weight, respectively). Overall, stream fish THg concentrations observed were not of concern, unlike other regions in New York State such as the Adirondack Mountains, but a significant proportion of Blacknose Dace (22 - 73%) and Creek Chub (5 - 69%) would be considered a risk to a range of sensitive consumers.