Climate change is expected to profoundly affect the Great Lakes region of North America. An increase in intensity and frequency of rain events is anticipated to deliver more runoff and to increase riverine inputs to Lake Superior's ecosystem. The effects of these changes on key biogeochemical parameters were analyzed by coupling satellite data, water column sensor profiles, and discrete surface-water sampling after two “500-year” flood events in the Lake Superior basin. This study provides both a spatial and a temporal sense of how plumes interacted within the ecosystem. We also determined the significant differences in water quality parameters for plume versus nonplume waters. These two plumes were important for delivery of nutrients, with variable transport of sediments and colored dissolved organic matter (CDOM). Data from the 2012 storm event showed a significant input of total nitrogen, total phosphorus, and CDOM to the system. In the 2016 storm event, carbon cycling parameters (acidity, total inorganic carbon, and dissolved organic carbon) and ammonia levels were elevated within the plume. In neither storm event was there a significant difference in chlorophyll a between plume and nonplume waters during our sampling cruises. These two plume events were similar in amount of precipitation, but their effect on the biogeochemistry of Lake Superior varied due to differences in the watersheds where the rain fell. The studied plume events were dynamic, changing with currents, winds, and the settling of suspended sediments.
Bibliographical noteFunding Information:
Thank you to the captain and crew of the R/V Blue Heron, Brandy Forsman, Sandy Brovold, Elizabeth James, and Sarah Grosshuesch, for their help in sample collection and processing. Thank you to the SeaDAS Development Group at NASA GSFC, NASA Goddard Space Flight Center, Ocean Ecology Laboratory, and Ocean Biology Processing Group. Thanks also to Esri, USGS, NGA, CGIAR, N Robinson, NCEAS, NLS, OS, NMA, GSA, Geoland, FEMA, Intermap, and the GIS user community for information to make the rain maps possible. This work was made possible by funding from the Minnesota Sea Grant College Program grant NA10OAR4170069, the EVCAA Office of the University of Minnesota Duluth, and the U.S. IOOS Office for the Development and Operation of the Great Lakes Observing System. Additional funding was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). Data supporting the analysis and conclusions are included in SI.
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- Lake Superior
- carbon cycling
- flood events
- storm plumes