Water Level Fluctuations and Internal Eutrophication in Lakes and Wetlands

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Release of phosphorus (P) from aquatic sediments is critical in regulating the growth of algae and aquatic plants. Sediment release of P is referred to as internal eutrophication because of the pivotal role of P as a limiting nutrient. Recent research has suggested that internal eutrophication involves complex biogeochemical processes and is accelerated by moderate concentrations of sulfate, a pollutant on the increase in many areas. Yet interestingly, the effects of sulfate can be reversed if sediments are allowed to dry periodically. This research seeks to understand the biogeochemistry of sediment P release, with an emphasis on how it is affected by water level stabilization vs. fluctuation. New linkages between sediment P release, the forms of iron and sulfur in sediments, and the role of periodic desiccation will be explored, focusing on a lake system regulated by a weir.This research has broader impacts because internal eutrophication is fundamental to managing lakes and wetlands: it can cause eutrophication, stymie restoration efforts, and delay recovery after nutrient loading is reduced. Water level regimes are altered by a myriad of human actions including impoundments, augmentation wells, agricultural land drainage, water withdrawals, and climate change. It is important to understand how these changes in water level regimes impact eutrophication, and thus affect ecosystem services and values provided by lakes and wetlands.