Effects of agricultural land use on chironomid communities: Comparisons among natural wetlands and farm ponds

Abstract

Constructed farm ponds represent a major wetland habitat type in southeastern Minnesota. Farm ponds are subject to a variety of disturbances associated with agricultural land use, especially sedimentation and eutrophication. Chironomid community structure often reflects environmental changes in aquatic ecosystems. However, chironomid communities in farm ponds are poorly understood and their response to short-term increases in sedimentation and eutrophication remains undetermined. We studied relationships between pond-land cover condition and chironomid community structure. Of the 40 ponds selected for the study, 10 were natural, permanent palustrine wetlands. The remaining ponds were constructed habitats (i.e., farm ponds) with 10 in each of the following categories: non-grazed grassland, grazed grassland, and row crop agriculture. Larval chironomids and water quality parameters were collected during early, mid-, and late summer 2001. Total nitrogen concentrations were significantly greater and turbidity was generally greater in grazed grassland ponds as compared to all other pond types. Chironomid communities of grazed grassland ponds were characterized by lower taxonomic richness and abundant chironomids tolerant of increased sedimentation and nutrient enrichment (i.e., Chironomus and Glyptotendipes). This study determined that agricultural land use, particularly cattle grazing, can markedly affect pond water quality, thereby influencing the chironomid community structure in farm ponds.