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Tuesday, January 29 • 6:00pm - 9:00pm
(P12) Energetic Carrying Capacity of Submersed Aquatic Vegetation in Semi-Permanent Marshes in the Upper Midwest

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AUTHORS. Margaret Gross, Western Illinois University/Illinois Natural History Survey-Forbes Biological Station; Heath Hagy, U.S. Fish & Wildlife Service; Christopher Jacques, Western Illinois University; John Simpson, Winous Point Marsh Conservancy; Sean Jenkins, Western Illinois University; J. Brian Davis, Mississippi State University; Joseph Lancaster, Illinois Natural History Survey-Forbes Biological Station; Aaron Yetter, Illinois Natural History Survey-Forbes Biological Station

ABSTRACT. Wetland management efforts often target seasonal wetlands because these habitats are considered the most valuable for waterfowl.  Understanding the distribution and availability of waterfowl food resources has become especially important amid the loss and degradation of wetland habitats.  Waterfowl managers typically estimate the energetic carrying capacity of a wetland by using bioenergetics models to compare energy demand to energy supply.  An efficient method for estimating food density utilizes visual indices and predictive equations, though previous attempts to develop predictive equations to estimate aquatic plant biomass are lacking.  Furthermore, aquatic vegetation density estimates are lacking for many of the semi-permanent marshes found throughout the Joint Venture, which could cause slight inaccuracies in bioenergetic model parameters.  We estimated the energetic carrying capacity of submersed aquatic vegetation for 20 wetland sites within the JV, which was expressed as energetic use days (EUD).  Six of the 20 wetland sites were sampled multiple years and the remaining 14 sites were sampled only once during summer 2015–2017.  Additionally, we evaluated a rapid assessment technique to estimate submersed aquatic vegetation biomass using percent horizontal coverage of each vegetation species, secchi depth, water depth, and vegetation species specific TMEN estimates.  The average energetic carrying capacity among wetland sites and years was 403,521 ± 139, 356 EUD and ranged from 4,114 EUD to 3,761,747 EUD.  The submersed aquatic vegetation rapid assessment technique facilitated the development of a predictive index, which was correlated with estimates of submersed aquatic vegetation biomass (kg/ha; R<sup>2</sup><sub>adj</sub> = 0.58, P < 0.0001) and EUD (R<sup>2</sup><sub>adj</sub> = 0.64, P < 0.0001).  Our results will be useful to conservation planners for estimating energetic carrying capacities of semi-permanently-flooded marsh habitats, which will aid in projecting impacts of wetland management alternatives (i.e., semi-permanently-flooded marsh versus moist-soil management).

Tuesday January 29, 2019 6:00pm - 9:00pm

Attendees (2)