## 3 Results
### Trends in Epilimnetic Methylmercury, Total Mercury, and Sulfate Concentrations  
Both methylmercury and total mercury concentrations declined in epilimnetic lake water over the 2001-18 period, although the declines at some lakes were small, relative to variability. For Brown Lake, a high methylmercury outlier previously identified [24] was omitted from trend analysis. The overall decline in MeHg\({}_{\text{aq}}\) for Brown Lake is modest (32%; Table 4), but noteworthy for two reasons. First, the previously reported trend for Brown Lake [24] was positive, but weak; and second, concentrations have declined sharply since peaking around 2010, about the end of the time frame for the previous trend analysis. Pears and Ryan Lakes had the largest declines in MeHg\({}_{\text{aq}}\) (Table 4), with much of the change occurring in the first few years of record. The comparatively large declines in these two lakes is consistent with earlier findings [24]. Shoepack Lake also exhibited a modest decline in MeHg\({}_{\text{aq}}\). The magnitude of the declines in MeHg\({}_{\text{aq}}\) for Brown and Shoepack Lakes is modest, in relation to the variability in concentrations at these two lakes; in addition, the 95-percent confidence intervals for the start and end of the period of study overlap for these two lakes suggesting that the decline is not significant (Figure 3). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**MeHg\({}_{\text{aq}}\)**} & \multicolumn{3}{c}{**THg\({}_{\text{aq}}\)**} & \multicolumn{3}{c}{**Sulfate**} \\ \hline  & **EV\({}_{\text{2001}}\)** & **EV\({}_{\text{2018}}\)** & **\% Change** & **EV\({}_{\text{2001}}\)** & **EV\({}_{\text{2018}}\)** & **\% Change** & **EV\({}_{\text{2001}}\)** & **EV\({}_{\text{2018}}\)** & **\% Change** \\ \hline Brown & 0.0854 & 0.0582 & \(-32\%\) & 1.94 & 1.53 & \(-21\%\) & 1.31 & 0.88 & \(-33\%\) \\  & [0.037, 0.134] & [0.011, 0.106] & & [1.57, 2.32] & [1.16, 1.90] & & [0.95, 1.66] & [0.58, 1.17] & \\ Peary & 0.1706 & 0.0468 & \(-73\%\) & 1.58 & 1.11 & \(-29\%\) & 1.24 & 0.71 & \(-43\%\) \\  & [0.140, 0.201] & [0.018, 0.076] & & [1.26, 1.89] & [0.81, 1.41] & & [0.33, ] & [\(-0.05,\) ] \\ Ryan & 0.2380 & 0.1243 & \(-48\%\) & 3.35 & 1.78 & \(-47\%\) & 2.79 & 1.66 & \(-41\%\) \\  & [0.194, 0.281] & [0.086, 0.162] & & [2.53, 4.17] & [1.08, 2.50] & & [2.31, 3.26] & [1.26, 2.05] & \\ Shoepack & 0.2592 & 0.1941 & \(-25\%\) & 2.73 & 2.44 & \(-11\%\) & 1.63 & 0.61 & \(-62\%\) \\  & [0.182, 0.337] & [0.108, 0.281] & & [2.28, 3.18] & [1.85, 3.02] & & [0.66, 2.59] & [\(-0.17, 1.39]\) & \\  & \multicolumn{3}{c}{mean \(=-44\%\)} & \multicolumn{3}{c}{mean \(=-27\%\)} & \multicolumn{3}{c}{mean \(=-45\%\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Epilimnetic lake water trends in methylmercury (MeHg\({}_{\text{aq}}\)), total mercury (THg\({}_{\text{aq}}\)), and sulfate, from locally weighted regression analysis, for the period 2001-2018. (EV\({}_{\text{2001}}\) and EV\({}_{\text{2018}}\) are expected values for concentrations of MeHg\({}_{\text{aq}}\) and THg\({}_{\text{aq}}\), in mg L\({}^{-1}\); and sulfate, in mg L\({}^{-1}\), from locally weighted regression analysis, for 1 July 2001, and 1 July 2018, respectively. % change, percentage change in expected values from 2001–2018. Lower and upper 95-percent confidence limits shown in brackets).