CLIMATE IMPACTS ON NUTRIENT LOADING IN LAKE ERIE

The Maumee Watershed is located near the Western Basin of Lake Erie and is comprised of 70% agricultural land. Anthropogenic nutrients of phosphorous and nitrogen are distributed across these lands through fertilizer application. During rain events these nutrients may become runoff, making their way to Lake Erie. Climate change is expected to increase both average precipitation events and average temperature, potentially changing nutrient loading from runoff and impacting harmful algal blooms as a result. Harmful algal blooms (HABs) have been persistent and increasing in recent years as anthropogenic nutrients and water temperatures, both necessary for algal growth, have increased. HABs can contribute a toxin known as microcystin, which can be detrimental to human health if ingested. In addition, the algal blooms disrupt economic activities such as charter fishing, shipping, tourism, and recreational use.

To help reduce nutrient loading best management practices (BMPs) have been employed to surrounding agricultural fields. BMPs and other agricultural practices range from practice and timing of fertilizer application to tilling practices. Previous studies focused on the effects of climate change and BMPs on sediment loading in the Maumee Watershed. This focus on sediment loading also contributed to the growing concern of HABs, showing changes in sediment delivery under different climate scenarios.

We expand on this research, focusing on nutrient loading rather than sediment loading as phosphorous has been identified as a limiting nutrient to HABs, with the dissolved phase being particularly important. To investigate how climate change and BMPs interact four climate scenarios, selected from CMIP5, and three BMPs are run in Soil and Water Assessment Tool (SWAT). SWAT is used to model and explain the effects of climate change and land management practices on watershed yields. The climate models focus on RCP 4.5, RCP 8.5, and historical data. BMPs modeled include nutrient application methods, tillage methods and filter strip utilization. Understanding the relationship between climate change and BMPs will aid more effective regulation practices to be considered to help constrain algal growth in the future.