Patterns of nutrient dynamics in Adirondack lakes recovering from acid deposition

Abstract

With decreases in acid deposition, nitrogen : phosphorus (N:P) ratios in lakes are anticipated to decline, decreasing P limitation of phytoplankton and potentially changing current food web dynamics. This effect could be particularly pronounced in the Adirondack Mountains of New York State, a historic hotspot for effects of acid deposition. In this study, we evaluate spatial patterns of nutrient dynamics in Adirondack lakes and use these to infer potential future temporal trends. We calculated Mann–Kendall tau correlations among total phosphorus (TP), chlorophyll a, dissolved organic carbon (DOC), acid neutralizing capacity (ANC), and nitrate (NO3−) concentrations in 52 Adirondack Long Term Monitoring (ALTM) program lakes using samples collected monthly during 2008–2012. We evaluated the hypothesis that decreased atmospheric N and S deposition will decrease P limitation in freshwater ecosystems historically impacted by acidification. We also compared these patterns among lake watershed characteristics (i.e., seepage or lacking a surface outlet, chain drainage, headwater drainage, thin glacial till, medium glacial till). We found that correlations (P < 0.05) were highly dependent upon the different hydrologic flowpaths of seepage vs. drainage lakes. Differentiations among watershed till depth were also important in determining correlations due to water interaction with surficial geology. Additionally, we found low NO3−:TP (N:P mass) values in seepage lakes (2.0 in winter, 1.9 in summer) compared to chain drainage lakes (169.4 in winter, 49.5 in summer) and headwater drainage lakes (97.0 in winter, 10.9 in summer), implying a high likelihood of future shifts in limitation patterns for seepage lakes. With increasing DOC and decreasing NO3− concentrations coinciding with decreases in acid deposition, there is reason to expect changes in nutrient dynamics in Adirondack lakes. Seepage lakes may become N‐limited, while drainage lakes may become less P‐limited, both resulting in increased productivity. Long‐term measurements of TP and chlorophyll a from the Adirondacks are needed to inform how future decreases in atmospheric N and S deposition will influence the trophic status of lake ecosystems throughout the region.

Climate change accelerates recovery of the Tatra Mountain lakes from acidification and increases their nutrient and chlorophyll a concentrations

“…Some of these presently non-acidified lakes in scree-rich catchments were acidified in the 1980s and exhibited steep recovery trends (Stuchlík et al 2017). Changes in their chemistry are consistent with a conceptual model by Gerson et al (2016) that predicts a decrease in P limitation in freshwater ecosystems after decreased atmospheric N and S deposition due to increasing terrestrial P leaching associated with decreasing P adsorbing capacity of soils and elevated P co-export with DOC.…”

Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health

“…Some studies, however, have not clearly detected changing patterns in soil–plant C:N:P stoichiometry along natural gradients of N deposition (Stevens et al, ). The decrease in N deposition in some areas of North America and Europe in recent decades has substantially decreased N:P ratios in lakes (Gerson, Driscoll, & Roy, ; Isles, Creed, & Bergstrom, ). Atmospheric P deposition is also increasing due to the rising levels of anthropogenic emissions of P to the atmosphere (3.5 Tg P/year), which have led to current net continental and oceanic rates of P deposition of 2.7 and 0.8 Tg P/year, respectively (Wang, Balkanski, et al, ).…”

“…The cascades of effects due to anthropogenic shifts in N:P ratios are similar in aquatic systems (lakes, estuaries, streams) and terrestrial ecosystems, where water and planktonic N:P ratios tend to F I G U R E 5 Current N and P imbalances linked to human activity in river basins increase in response to atmospheric deposition, leading to lower "growth rates," complexity of community structure, and trophic diversity ( Figure 6; Table S1). Exceptions to these trends, however, have been recorded for aquatic systems, such as a decrease in N:P ratios in Japan due to the increasing deposition of P from dust dispersed from countries in southeastern Asia (Miyazako et al, 2015), and for European and North American lakes in areas with recent reductions in N deposition (Gerson et al, 2016;Isles et al, 2018). Although most studies of urban and crop wastes and leachate loads to rivers and estuaries (83.3%) have found increasing N:P ratios associated with increasing N:P ratios from human inputs, other studies (13.7%) tended to find decreasing ratios in areas with high livestock densities (Arbuckle & Downing, 2001;Johnson, Heck, & Fourqurean, 2006; Figure 6; Table S1).…”

Acidification and Climate Linkages to Increased Dissolved Organic Carbon in High‐Elevation Lakes

“…Due to climatic factors at high elevations, bedrock geology with little ANC, frequent immersion in acidic cloud, and dominant softwood forest cover, high-elevation lakes were more vulnerable to acidification and experienced higher levels of acidity than other New England lakes (Aleksic et al, 2009;Baumann, 2011;Gerson et al, 2016;Greaver et al, 2012;Weathers et al, 2000). Coupled with higher amounts of precipitation, HELM lakes were more influenced by acidic deposition than other lake subsets in Maine (Kahl, 1998).…”