PRE-COLONIZATION TO MODERN ANTHROPOGENIC IMPACTS ON LAKE BIOGEOCHEMICAL CYCLES: EXAMPLES FROM CHAIN O’ LAKES STATE PARK, INDIANA

Chain O’Lakes State Park (COLSP) is located in northern Indiana and is a popular destination for recreation in the area. COLSP has 9 interconnected lakes and 4 satellite lakes within its borders, and over the last decade has experienced cyanobacteria blooms likely due to increased nutrient fluxes into the lake system. In the fall of 2013, short (<1m) sediment cores were collected from the 9 interconnected lakes at COLSP, including Long Lake, which is one of the larger lakes located upstream from 7 of the other lakes. Fossil diatom analysis from Long Lake suggested recent septic system leaks at an on-site correction facility was likely contributing to the nutrient loads. A second 1.5m core was collected in 2014. Visual analysis of this core suggests that the core sediments represent pre-settlement through modern day depositional environments, which still needs to be confirmed through radiocarbon and ²¹⁰Pb dating.

To better understand the history of nutrient burial in COLSP resulting from land use change and cultural eutrophication, detailed phosphorus (P) geochemistry is being used on 60 samples from the Long Lake core to identify the temporal variability in sedimentary P associations on the sediments. Phosphorus is an important nutrient element to all organisms, and it likely limits productivity on geologic time scales. In combination with fossil diatom assemblages, P fluxes and associations will be used to determine the relationships between land use change related to initial colonization and introduction of settlements in the area to increased use of fertilizers associated with agriculture. The results of this research will help us to understand the history of anthropogenic impacts on this lake system and to identify what pristine conditions may have been like.