Influence of physical and chemical charicteristics of sediment on macroinvertebrate communities in agricultural headwater streams

Authors: SHUMAN, TYLER - Indiana University-Purdue University; Smiley, Peter - Rocky; GILLESPIE, ROBERT - Indiana University-Purdue University; Gonzalez, Javier

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2020
Publication Date: 10/23/2020
Citation: Shuman, T.C., Smiley, P.C., Gillespie, R.B., Gonzalez, J.M. 2020. Influence of physical and chemical charicteristics of sediment on macroinvertebrate communities in agricultural headwater streams. Water. 12(11). Article 2976. https://doi.org/10.3390/w12112976.
DOI: https://doi.org/10.3390/w12112976

Interpretive Summary: Agricultural land use alters the physical and chemical characteristics of stream sediments, which results in reductions of macroinvertebrate biodiversity and abundance in agricultural streams. The combined influence of physical and chemical sediment conditions on stream macroinvertebrates has not been assessed because previous research focused on the influence of physical sediment variables or chemical sediment variables. We measured sediment physical and chemical variables and sampled macroinvertebrates in eight agricultural headwater streams in Indiana, Michigan, and Ohio over a two year period to document the physical and chemical conditions of the stream sediments and the influence of sediment physical and chemical variables on stream macroinvertebrates. We documented that most sites were dominated by sand or silt and overall chemical conditions suggested suitable conditions for macroinvertebrates. We also observed that increasing amounts of silt corresponded with increases in selected plant nutrients within the stream sediments. Macroinvertebrate biotic integrity declined with increasing simazine concentrations, decreasing calcium concentrations, increasing substrate heterogeneity, and decreasing amounts of sand. Our results represent the first documentation of the joint influence of sediment physical and chemical variables on macroinvertebrates in agricultural headwater streams in the Midwestern United States. Our results suggest that watershed management plans need to address physical and chemical degradation within the stream sediments to improve macroinvertebrate biotic integrity within agricultural headwater streams in the Midwestern United States. Our results will be of interest to state agencies, federal agencies, private consulting companies, and non-profits involved with the management of agricultural watersheds in the United States because they provide information that can assist with developing watershed conservation plans capable of improving physical habitat quality and biotic integrity in agricultural headwater streams.

Technical Abstract: Agricultural land use leads to changes in physical and chemical sediment variables that influence macroinvertebrate community diversity and abundance in streams. The joint influence of physical and chemical sediment variables on stream macroinvertebrates has not been assessed because previous research has focused on physical sediment variables or chemical sediment variables. We measured sediment physical and chemical variables and sampled macroinvertebrates in eight agricultural headwater streams in Indiana, Michigan, and Ohio, United States over a two year period to determine the physical and chemical conditions of the sediment, to evaluate the relationships between sediment physical and chemical variables, and the relationship between macroinvertebrate communities with sediment physical and chemical variables. The sediments within most sites were dominated by sand or silt. pH, nitrate, herbicide concentrations, and trace metal concentrations indicated suitable conditions for macroinvertebrates. Increases in percent small gravel and decreases in percent silt corresponded (p < 0.05) with decreases in potassium concentrations, magnesium concentrations, and percent total nitrogen. Invertebrate Community Index scores were negatively correlated (p < 0.05) with increasing sediment simazine concentrations and decreasing calcium concentrations and were negatively correlated (p < 0.05) with increasing grain size diversity and decreasing percent sand. Macroinvertebrate abundance, Shannon Diversity Index, the Reciprocal Berger-Parker Dominance Index, percent collector-filterers, percent scrapers, percent Chironomidae, and Hilsenhoff Biotic Index scores were not correlated (p > 0.05) with the measured physical and chemical sediment variables. Our results suggest that watershed management plans need to address physical and chemical degradation to improve macroinvertebrate biotic integrity within agricultural headwater streams in the Midwestern United States.