Comparison of overwintering macroinvertebrate communities in near shore and profundal habitats in a prairie pothole lake in west-central Minnesota

Macroinvertebrate communities in temperate lakes are not often studied during the winter, even though ice cover provides relatively stable conditions that may persist for several months.  During the winter of 2008 we collected 15 Eckman grab samples from both the profundal and near shore habitats of Cottonwood Lake, a mesotrophic prairie pothole lake that has undergone watershed improvements to mitigate the effects of agriculture and introduced species.   Fourteen macroinvertebrate taxa were identified in profundal samples, while 23 taxa occurred in the near-shore samples.  No taxa were unique to the profundal samples.  Taxon richness ranged from 4-13 taxa/sample in profundal samples and 5-13 taxa/sample in near shore samples; mean taxon richness did not differ significantly between habitats.  Hyalella azteca and Glyptotendipes were the most abundant taxa in near shore samples while Chironomus was most abundant in profundal samples.  The prevalence of shredder taxa such as H. azteca and Glyptotendipes close to shore suggests that CPOM from decaying macrophytes or surrounding vegetation is a readily available food resource that supports macroinvertebrates in this lake throughout the year.  Ensuring the availability of CPOM may be an important aspect of restoring prairie pothole lakes in agricultural landscapes.