Influence of riparian habitat on aquatic macroinvertebrate community colonization within riparian zones of agricultural headwater streams

Abstract

Little is known about aquatic macroinvertebrate colonization of aquatic habitats within riparian zones of headwater streams in the midwestern United States. Many headwater streams and their riparian habitats in this region have been modified for agricultural drainage. Riparian habitat modifications caused by agricultural drainage may influence aquatic macroinvertebrate colonization within the riparian zones of headwater streams. However, the effects of agricultural drainage-induced riparian modifications have not been evaluated because others have focused on the impact of agricultural drainage on aquatic macroinvertebrates within the streams. We placed water-filled mesocosms in the riparian zones of two channelized and two unchannelized streams in central Ohio and sampled them from June to August 2009 to determine if differences in physical habitat, water chemistry, and aquatic macroinvertebrate colonization occurred between riparian zone types and among sampling dates. Canopy cover was greater in unchannelized than channelized riparian zones. Dissolved oxygen was greater in channelized than unchannelized riparian zones only during the latter half of the study. Turbidity and nutrients progressively increased throughout the study. Taxa richness was greater in unchannelized than channelized riparian zones. Copepod relative abundance, zooplankton relative abundance, and Shannon diversity index was greater in unchannelized than channelized riparian zones only during the latter half of the study. Abundance, taxa richness, culicid relative abundance, and dipteran relative abundance increased from the beginning of the study to the end. Our results indicate aquatic community colonization in the riparian zones of headwater streams is influenced by riparian habitat type and nutrients.