Water quality improvements in shallow eutrophic lakes are commonly delayed due to loading from legacy phosphorus (P)-enriched sediments, even with reduced external nutrient loads. It is critical to understand the drivers of internal P loading to suppress or remove this source of P and meet water quality goals. We contrast the drivers of internal P loading in two shallow eutrophic systems (Lake Carmi and Missisquoi Bay). Legacy P dynamics in the unmanipulated systems were compared to Lake Carmi during aeration. In-situ high frequency water column monitoring along with water and sediment sampling was used to study P dynamics in response to changing lake conditions and aeration. Despite both systems exhibiting P mobility controlled by iron redox cycling, we observed distinct differences in the spatial extent and drivers of internal P loading. Legacy P loading was controlled by seasonal drivers in Lake Carmi, but by spatially variable and highly transient wind driven forcing of hydrodynamics in Missisquoi Bay. Aeration altered the mixing regime of Lake Carmi and shifted loading dynamics to frequent wind-driven pulses of legacy P to surface waters akin to those of Missisquoi Bay. Mean hypolimnetic dissolved oxygen increased with aeration, but greater oxygen demand rates and periods of anoxia under transient stratification still resulted in internal P loading. Surface P concentrations were higher in summer months with aeration compared to previous years. This research illustrates the dynamic nature of legacy P behavior within and between shallow eutrophic lakes and the challenges in addressing this common water resources threat.

A zip folder of data and stormwater runoff model

De-icing salt is an important regional pollutant identified as a contaminant of concern in the Lake Champlain Basin Program’s (LCBP) Opportunities for Action. It is of particular concern in areas of dense urban development where runoff from roads, parking lots, sidewalks, and driveways can contain high concentrations of salt. This is true for Mirror Lake and the Chubb River, located in the headwaters of the West Branch Ausable River subwatershed. In the case of Mirror Lake, direct stormwater discharge to the lake has resulted in a reduction in spring mixing due to salt-induced density differences within the water column. The primary objectives of this three-year LCBP-funded project were to 1) establish a continuous water quality monitoring program capable of quantifying de-icing salt pollutant load to Mirror Lake and the Chubb River, 2) estimate the de-icing salt pollutant load to Mirror Lake from direct stormwater runoff, 3) estimate the total amount of de-icing salt applied within the Chubb River watershed, and 4) educate the public about the effects of de-icing salt on the environment and BMPs for de-icing salt reduction.

This project aimed to develop assessment tools that support wetland and riparian management and stewardship to improve flood resiliency, water quality, and habitat for native species in the New York State (NYS) portion of the Lake Champlain Basin. The primary objective was to produce a comprehensive wetland and stream assessment dataset available through an interactive online mapping tool to increase the effectiveness of conservation decision-making in the basin. Our strategy included synthesizing scientific information about streams and wetlands and validating this information with field surveys in both systems. This project spanned from January 2021 to January 2023 and was funded by an agreement awarded by the United States Environmental Protection Agency to NEIWPCC in partnership with the Lake Champlain Basin Program.