Event Title
Out of Oxygen: Warming and Loading Shape Bottom Water Hypoxia Dynamics in a Great Lakes Estuary
Location
Hager-Lubbers Exhibition Hall
Description
PURPOSE: Bottom water (hypolimnetic) hypoxia occurs annually and is exacerbated by anthropogenic eutrophication and climate change in Muskegon Lake, a model Great Lakes estuary with ecological and economic significance as habitat for cool and warm water fish and as a tourism source. As the hypolimnion becomes hypoxic and ultimately anoxic, additional consequences include the release of sediment-bound legacy phosphorus and subsequent proliferation of surface harmful algal blooms. The purpose of this study was to understand the creation and subsequent consequences of bottom water hypoxia in Muskegon Lake. SUBJECTS: Water samples were collected biweekly for nutrient analyses to be conducted. METHODS AND MATERIALS: We tracked fluctuating hypoxia in Muskegon Lake - a model Great Lakes estuary, using a high-frequency time-series observatory buoy (https://www.gvsu.edu/wri/buoy/), biweekly nutrient analyses, and seasonal respiration experiments. ANALYSES: Linear regressions and an ANOVA were utilized to determine the difference in slopes between sites for the seasonal bottle experiments. RESULTS: Wind mixing events were found throughout the sampling period that reduced the hypoxic zone and temporarily broke up stratification. In spring experiments, riverine organic matter inputs caused hypoxia more readily, whereas in the summer and fall, surface primary production caused hypoxia more readily. Preliminary analyses detected soluble reactive phosphorus in the bottom water during anoxia – indicative of internal phosphorus loading. CONCLUSIONS: Surface productivity and riverine inputs drive hypoxia seasonally. Internal phosphorus loading was indicated in Muskegon lake. Findings have bearing to similarly afflicted ecosystems such as Lake Erie and other Great Lakes estuaries.
Out of Oxygen: Warming and Loading Shape Bottom Water Hypoxia Dynamics in a Great Lakes Estuary
Hager-Lubbers Exhibition Hall
PURPOSE: Bottom water (hypolimnetic) hypoxia occurs annually and is exacerbated by anthropogenic eutrophication and climate change in Muskegon Lake, a model Great Lakes estuary with ecological and economic significance as habitat for cool and warm water fish and as a tourism source. As the hypolimnion becomes hypoxic and ultimately anoxic, additional consequences include the release of sediment-bound legacy phosphorus and subsequent proliferation of surface harmful algal blooms. The purpose of this study was to understand the creation and subsequent consequences of bottom water hypoxia in Muskegon Lake. SUBJECTS: Water samples were collected biweekly for nutrient analyses to be conducted. METHODS AND MATERIALS: We tracked fluctuating hypoxia in Muskegon Lake - a model Great Lakes estuary, using a high-frequency time-series observatory buoy (https://www.gvsu.edu/wri/buoy/), biweekly nutrient analyses, and seasonal respiration experiments. ANALYSES: Linear regressions and an ANOVA were utilized to determine the difference in slopes between sites for the seasonal bottle experiments. RESULTS: Wind mixing events were found throughout the sampling period that reduced the hypoxic zone and temporarily broke up stratification. In spring experiments, riverine organic matter inputs caused hypoxia more readily, whereas in the summer and fall, surface primary production caused hypoxia more readily. Preliminary analyses detected soluble reactive phosphorus in the bottom water during anoxia – indicative of internal phosphorus loading. CONCLUSIONS: Surface productivity and riverine inputs drive hypoxia seasonally. Internal phosphorus loading was indicated in Muskegon lake. Findings have bearing to similarly afflicted ecosystems such as Lake Erie and other Great Lakes estuaries.