Climate-driven changes in energy and mass inputs systematically alter nutrient concentration and stoichiometry in deep and shallow regions of Lake Champlain

Abstract

Concentrations of nitrogen (N) and phosphorus (P) in lakes may be differentially impacted by climate-driven changes in nutrient loading and by direct impacts of temperature and wind speed on internal nutrient cycling. Such changes may result in systematic shifts in lake N:P under future climate warming. We used 21 years of monitoring data to compare long-term and intra-annual trends in total N (TN), total P (TP) and TN:TP at 15 sites in Lake Champlain to concurrent measurements of watershed nutrient inputs and meteorological drivers. TN:TP declined sharply lake-wide, particularly in the past decade, yet the drivers of this trend varied based on site depth. In deep sites, declines were driven by changes in watershed loading of dissolved P and N and (in some cases) by decreases in hypolimnetic dissolved oxygen. In shallow sites, declines in TN:TP were primarily driven by long-term increases in temperature and decreases in wind speed, and exhibited systematic seasonal variability in TN:TP due to the timing of sediment P loading, N removal processes, and external nutrient inputs. We developed a conceptual model to explain the observed trends, and suggest that while climate drivers have affected nutrient dynamics in shallow and deep sites differently, both deep and shallow sites are likely to experience further declines in N:P and increases in cyanobacteria dominance if recent climate trends continue.

Optimizing wetland restoration to improve water quality at a regional scale

“…The model output is provided as an NDR raster. The digital elevation model and land cover datasets (Homer et al 2015) were obtained at 30 m spatial resolution from the United States Geological Survey. The runoff proxy raster was acquired from the seasonal water yield module of InVEST developed for the state of Vermont by Watson et al (2019).…”

Impact of an Extreme Storm Event on River Corridor Bank Erosion and Phosphorus Mobilization in a Mountainous Watershed in the Northeastern United States

“…There are dams at select locations along the Mad River and Winooski River main stems with potential for transient storage of sediments in the resulting impoundments. Anoxic conditions can occur in shallow sediments of these impoundments or in the ultimate receiving waters of Lake Champlain where such conditions have been linked to algal blooms (Isles et al, 2015(Isles et al, , 2017.…”

The interaction of physical structure and nutrient loading drives ecosystem change in a large tropical lake over 40 years

“…In some regions, increased nitrogen supply has shifted the macronutrient that limits primary productivity from nitrogen (N) to phosphorus (P) (Elser et al 2009; Ackerman et al 2019). Global change is also responsible for declining fisheries productivity (O’Reilly et al 2003), changes in greenhouse gas emissions (Delsontro et al 2018) and changes in dissolved N:P stoichiometry (Isles et al 2017) in lake ecosystems. These impacts are often exacerbated by local anthropogenic stressors including over exploitation of resources, as well as enhanced loading of nutrients and organic pollutants from the surrounding watershed (Farrell et al 2020).…”