Macroinvertebrates have important functional roles in wetland ecosystems, but these roles are not always well understood. This study assessed which foods invertebrate consumers assimilate within a set of wetland habitats. During 2006 and 2007, non-Tanypodinae chironomid larvae and select crustaceans (Crangonyx amphipods, Caecidotea isopods, Simocephalus cladocerans) were sampled, along with their potential food sources, from forested and herbaceous areas in wetland habitats (depression, floodplain, swamp complex) across the southeastern U.S.A. Invertebrate and food source samples were processed for carbon and nitrogen isotope signatures. These data were analyzed with the U.S. Environmental Protection Agency's IsoSource mixing model, to estimate the potential relative contributions of different food items and to highlight both important and unlikely food sources. In the forested habitats, litter from trees (leaves, wood, fruit), epiphyton, detrital FPOM (fine particulate organic matter), sediment, and macrophyte litter were found to be major foods for midges and crustaceans, although considerable spatial and temporal variation existed in consumption. In the herbaceous habitats, algae (epiphyton, periphyton, metaphyton, phytoplankton), sediment, and macrophyte litter were important food resources. Comparisons between forested and herbaceous wetlands suggested that algal resources were widely consumed by midges and crustaceans, and that detrital sources were also important in forested wetlands.

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