Evaluating the role of Allochthonous organic matter as a food resource for shredders in a prairie pothole lake in west central Minnesota

In Cottonwood Lake, a prairie pothole lake in west central Minnesota, shredders make up a significant part of the macroinvertebrate community in the littoral zone (67% abundance, 25% of all taxa). Trees occur along much of the shoreline suggesting that terrestrially derived organic matter could be an important source of CPOM for macroinvertebrates in prairie potholes, particularly in the littoral zone. Stable isotopes of carbon (13C) and nitrogen (15N) of the common shredders Glyptotendipes and Hyalella azteca were compared to those of the collector-gather, Chironomus and the predator, Cryptochironomus. Stable isotopes of potential sources of allochthonous (oak, American elm, cottonwood) and authochthonous (cattail) CPOM taken from the lake were also evaluated. Both ?13C and ?15N were significantly depleted in Chironomus compared to other macroinvertebrates. H. azteca, had significantly greater values of ?13C than all other macroinvertebrates. Sources of CPOM did not show distinctive profiles for either 13C or 15N, highlighting the challenge of characterizing detrital food resources. Further analyses will help discern the fate of terrestrial inputs in prairie pothole lakes.