Mon, Aug 02, 2021:On Demand
Background/Question/Methods
Floodplain lakes are important aquatic resources for supporting ecosystem services, such as biodiversity and nutrients and sediment retention. Geomorphic alteration of river channels and land-cover change have led to degradation to floodplain lakes in the upper Mississippi River basin and is occurring at alarming rates as climate change causes increased flood intensity and seasonal redistribution of rainfall. A better understanding of the local drivers impacting oxbow lakes is needed for targeted floodplain restoration. To this end, we investigated: 1) how does hydrological river connectivity influence water quality and fish diversity in floodplain lakes of the Wabash-White watershed, and 2) how can use this understanding of the major drivers to guide floodplain conservation and restoration efforts? We examined the effects of slope and hydrologic connectivity on water quality and fish diversity and abundance in nine floodplain lakes in the watershed. We measured water-quality parameters; stable water isotopes; total phosphorus, total nitrogen, and chlorophyll-a; and fish community diversity and abundance.
Results/Conclusions An increase in total phosphorus, total nitrogen, and chlorophyll-a was observed in floodplain lakes with shallower watershed slopes and reduced hydrologic connectivity to the main river, as evidenced by stable water isotope ratios. Floodplain lakes that were more disconnected from the main channel showed greater biodiversity and abundance in fish assemblages. The results of this study suggest that slope in the local watershed and hydrologic connectivity to the main channel influence nutrient loading and fish communities in important ways. Knowing the influencing factors can help ecosystem managers better protect these valuable floodplain lake ecosystems and prioritize restoration efforts amidst increasing stressors due to climate and land-use changes.
Results/Conclusions An increase in total phosphorus, total nitrogen, and chlorophyll-a was observed in floodplain lakes with shallower watershed slopes and reduced hydrologic connectivity to the main river, as evidenced by stable water isotope ratios. Floodplain lakes that were more disconnected from the main channel showed greater biodiversity and abundance in fish assemblages. The results of this study suggest that slope in the local watershed and hydrologic connectivity to the main channel influence nutrient loading and fish communities in important ways. Knowing the influencing factors can help ecosystem managers better protect these valuable floodplain lake ecosystems and prioritize restoration efforts amidst increasing stressors due to climate and land-use changes.