Abstract
Agricultural land use leads to changes in physical and chemical characteristics of sediment that influence macroinvertebrate community diversity and abundance in streams. To the best of our knowledge the joint influence of sediment’s physical and chemical characteristics on stream macroinvertebrates has not been assessed. We measured sediment’s physical and chemical characteristics and sampled macroinvertebrates in eight agricultural headwater streams in Indiana, Michigan, and Ohio, United States, in 2017 and 2018 to determine the physical and chemical conditions of the sediment, to evaluate the relationships between physical and chemical characteristics of the sediment, and the relationship of macroinvertebrate communities with the sediment’s physical and chemical characteristics. Sediments within most sites were dominated by sand or silt. pH was suitable for macroinvertebrates and nitrate, herbicide, and trace metal concentrations were below concentration levels anticipated to affect macroinvertebrate survival. Linear mixed effect model analysis results indicated that a physical gradient of percent small gravel and percent silt was positively correlated (p < 0.05) with a chemical gradient of potassium concentrations, magnesium concentrations, and percent total nitrogen in the sediments. Our linear mixed effect model analysis results also indicated that Invertebrate Community Index scores were negatively correlated (p < 0.05) with a chemical gradient of simazine and calcium concentrations and were negatively correlated (p < 0.05) with physical gradient of grain size diversity and percent sand. Our results suggest that watershed management plans need to address physical and chemical degradation of sediment to improve macroinvertebrate biotic integrity within agricultural headwater streams in the Midwestern United States.
Highlights
Macroinvertebrates in streams are influenced by a wide range of abiotic and biotic factors operating at different spatial and temporal scales [1,2]
Most streams in SJR and Upper Big Walnut Creek watershed (UBWC) have been channelized for agricultural drainage and watershed management issues encompass nutrients, pathogens, and physical habitat degradation [28,29]
Sediments within most sites were dominated by sand or silt. pH levels were suitable for macroinvertebrates and nitrate, atrazine, metolachlor, simazine, copper, and zinc concentrations observed were below concentration levels anticipated to affect macroinvertebrate survival
Summary
Macroinvertebrates in streams are influenced by a wide range of abiotic and biotic factors operating at different spatial and temporal scales [1,2]. Benthic sediments represent a critical habitat resource for stream macroinvertebrates because many reside within the sediment or on its surface. Discovery of the importance of sediment particle size for stream macroinvertebrates dates back to the late 1920s [3]. Interest in sediment’s physical characteristics by early stream ecologists was likely influenced by a parallel interest by marine biologists with invertebrate-substrate relationships [3]. Sediment particle size and other physical characteristics of sediment have long been considered the foundation of the physical habitat template [4] for macroinvertebrates and a critical determinant of macroinvertebrate. Increases in macroinvertebrate diversity and abundance with increasing particle size and particle size diversity has been well documented [1,5]
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