Energetic Carrying Capacity of Submersed Aquatic Vegetation in Semi-Permanent Wetlands Important to Waterfowl in the Upper Midwest

Intensification of land use practices and climate change have resulted in extensive wetland loss and declines of native submersed aquatic vegetation (SAV) species across North America. Limited by a lack of biomass and energy estimates for wetlands containing SAV, conservation planners currently are unable to accurately account for its energetic contribution in bioenergetics models for waterfowl and other waterbirds. Therefore, we estimated energetic carrying capacity of 21 semi-permanent wetlands containing SAV and identified as important stopover locations for migrating waterfowl and other waterbirds in the Midwest, USA during 2015-2017. Energy density of SAV ((x) over bar = 813 +/- 257 EUD/ha) was generally less than managed emergent wetlands, varied by National Wetland Inventory class, and had large annual (98-4873 Delta EUD/ha) and spatial variation (8-7971 EUD/ha). We developed a visual rapid assessment index (R-m(2) = 0.43) that may be useful to wetland managers or researchers to quickly index energy density from SAV in semi-permanent wetlands. Energetic carrying capacity of wetlands containing SAV will allow conservation planners to more precisely estimate energy supply on the landscape for waterfowl and evaluate trade-offs among alternative management strategies. Our results demonstrate negative effects of hydrologic connectivity on SAV communities in highly modified landscapes.