A critical question arises: how have lacustrine ecosystems in midcontinental North America responded to regional and North American mercury emissions versus global emissions? This question is particularly important because the Minamata Convention on Mercury [16], a legally-binding international treaty to reduce mercury use and releases to the environment, is being implemented by 128 signatory nations. Thus, assessing \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Year** & **1990** & **2000** & **2005** & **2008** & **2011** & **2014** & **2017** & **Percentage Change** \\ \hline \multicolumn{1}{c}{} & \multicolumn{6}{c}{Air emissions of mercury, total for all sectors, Mg yr\({}^{-1}\)} \\ United States & 223 & – & 95 & 55 & 51 & 47 & 30 & \(-\)86.6\% \\ Canada & 34.3 & 9.5 & 7.9 & 6.6 & 3.8 & 3.5 & 3.0 & \(-\)91.2\% \\ Total US and Canada & 257 & – & 103 & 62 & 55 & 51 & 33 & \(-\)87.2\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Trends in emissions of mercury in the U.S. [9] and in the Canadian provinces of Manitoba and Ontario [10], 1990–2017. [U.S. data were reported in short tons; Canadian data were reported in kilograms [kg]; all data have been converted to Mg yr\({}^{-1}\); percentage change is from 1990 to 2017.]. ecosystem responses to contemporary mercury reductions may be informative in assessing treaty implementation. A few other studies have attempted to answer this question. There is mixed evidence for ecosystems responses to changing emissions trajectories, including some literature showing declining fish-mercury levels in response to regional emission reductions [17] and other studies showing long-term (1970s-2000s) declines in fish-mercury concentrations followed by a leveling off or increase in concentrations in recent years [18; 19]. Mercury in the feathers of bald eagle (_Haliaetus leuccephalus_) nestlings have shown similar temporal trends within the region [20]. This paper addresses the question: how have aquatic ecosystems responded? Here, we report on one of the longest known paired data sets for mercury in atmospheric deposition; mercury, methylmercury, and key other chemical and physical parameters in several lacustrine systems; and total mercury in aquatic biota from the same lacustrine systems. This paper reports an updated analysis of trends in mercury deposition at two northern Minnesota NADP Mercury Deposition Network (MDN) sites, as well as trends in methylmercury and total mercury concentrations in epilimnetic lake water and in biota from four lakes in a minimally disturbed area within Voyageurs National Park, also in northern Minnesota. Through several earlier studies [21; 22; 23; 24], and an ongoing collaboration between the U.S. Geological Survey (USGS) and the National Park Service (NPS), these lakes have been sampled for mercury since 2000 or 2001 (depending on the lake), making these among the longest running data sets that pair total mercury and methylmercury in lake water with biotic mercury. Given the paucity of long-term data sets on aqueous mercury in undisturbed ecosystems, the sensitivity of circumneutral, low-ionic-strength aquatic ecosystems to the effects of mercury and sulfate deposition [7; 25], and widespread consumption advisories in this region, the Voyageurs National Park data set provides a useful case study to monitor ecosystem responses to changes in atmospheric inputs. Trends in regional wet deposition, epilimnetic mercury, and mercury in age-1 yellow perch (_Perca favescens_) were previously reported through 2012 [24]. This paper examines trends through 2018. In the current paper, the longer time period necessitated a change in trend analysis to account for nonlinearity in the data; also, given a change in organisms collected for biomonitoring, we applied a statistical relationship between mercury in dragonfly larvae and in age-1 yellow perch in order to extend the perch record.