The site of our long-term research is Acton Lake, a eutrophic reservoir, and its watershed, which is dominated by row crop agriculture. Reservoirs are among the most heavily subsidized ecosystems on earth, owing to large watershed:lake area ratios. Reservoirs in agricultural areas, which are common in many areas (such as the Midwest US) are subject to high rates of soil erosion. Reservoirs thus receive large subsidies of water, sediment and nutrients, often in a very episodic manner depending on the timing and intensity of storms.
Acton Lake is a highly eutrophic reservoir located in Hueston Woods State Park in southwestern Ohio. Its watershed is large compared to lake surface area (~110X) and is ~80% agriculture (Renwick et al. 2008, 2018). Forest (~12% of watershed) is mostly confined to Hueston Woods State Park and some riparian areas, and developed areas comprise only ~5% of the watershed. Since 1994, we have used a high-resolution sampling program to quantify sediment and nutrient inputs to the lake via its 3 largest inflow streams, which drain 86% of the watershed (Vanni et al. 2001, 2006a , 2011; Knoll et al. 2013; Renwick et al. 2008, 2018; Williamson et al. 2018). As expected, Acton Lake receives large nutrient and sediment subsidies, and exhibits elevated nutrients and phytoplankton. Gizzard shad are extremely abundant (Schaus et al. 1997; Vanni et al. 2005, 2006b ; Hale et al. 2008; Williamson et al. 2018) and the zooplankton assemblage is usually dominated by small species, primarily rotifers (Pollard et al. 1997; Bunnell et al. 2003). Phytoplankton biomass is dominated by cyanobacteria during summer (Schaus and Vanni 2000; Dickman et al. 2006; Vanni et al. 2011; Hayes et al. 2015). Phytoplankton are often light-limited, especially after storms that deliver large amounts of sediments (Vanni et al. 2006a; Kelly et al. 2018). When nutrients are limiting, phosphorus (P) was historically the limiting nutrient (Vanni et al. 2006a,b) and nitrogen (N) was limiting only during drought years (Hayes et al. 2015). However, N limitation has become more prevalent in recent years (see Results page for more details).