Aquatic community structure and stream habitat in a karst agricultural landscape

Neal D Mundahl,Erik D Mundahl

doi:10.1186/s13717-022-00365-1

Abstract

BackgroundWatersheds dominated by agriculture often have significant, negative impacts on local stream habitats and fauna. Our study examined stream biota and habitats within an entire stream in a karst agricultural landscape to determine if several decades of watershed conservation and management had reversed the severe degradation caused by poor land use and catastrophic soil erosion during the 1920s and 1930s.ResultsFish communities and stream habitats were degraded at over half of the 22 stream sites examined, and benthic macroinvertebrate communities were mostly poor throughout the entire stream. Poor fish communities were associated with missing or narrow riparian buffers, high percent fine sediments, high embeddedness of coarse substrates, and homogeneous run habitat. Invertebrate communities were dominated by filter-feeding taxa and those adapted to life on or within fine sediments. Stream sites with wide buffers and influenced by groundwater springs had higher fish community integrity and good to excellent instream habitat.ConclusionsOur results suggest that wide riparian buffers and karstic springs may have allowed recovery of some stream reaches, but more extensive buffers and additional soil conservation practices in upland areas likely are necessary to protect most stream segments and their biota from on-going agricultural activities. New state stream buffer laws instituted after this study resulted in establishment of vegetated buffers at all study sites, which may lead to improved stream habitat and biotic communities in future years. Benthic invertebrate community improvement also may require translocation of sensitive taxa from nearby watersheds due to limited dispersal abilities of many species currently absent from the study stream. Increased frequency and intensity of storm events and flooding may hinder future recovery of stream habitats and biota.

Highlights

Streams draining agricultural landscapes can be impacted by eroded soils (Armour et al 1991; Waters 1995), excessive nutrients (Tesoriero et al 2009; Dubrovsky and Hamilton 2010), altered hydrology (Freeman et al 2007; Blann et al 2009), and numerous herbicides and pesticides (Battaglin and Fairchild 2002; Schäfer et al 2007)
Stream habitats and biota in many portions of the South Fork Whitewater River (SFWR) are impacted by on-going agricultural activities, even though watershed conservation and management activities have been conducted within the drainage basin since the 1940s
With 77% of the watershed dedicated to crop and livestock production, upland soil conservation practices and intact riparian buffers are needed along the SFWR to reduce sedimentation and absorb nutrients and agricultural chemicals

Summary

Introduction

Streams draining agricultural landscapes can be impacted by eroded soils (Armour et al 1991; Waters 1995), excessive nutrients (Tesoriero et al 2009; Dubrovsky and Hamilton 2010), altered hydrology (Freeman et al 2007; Blann et al 2009), and numerous herbicides and pesticides (Battaglin and Fairchild 2002; Schäfer et al 2007). These factors in turn can lead to degraded stream habitats (Davis et al 2003), changes in productivity (McTammany et al 2007), reductions or loss of sensitive aquatic taxa (Lenat 1984), and modified food webs (Moss 2008). Our study examined stream biota and habitats within an entire stream in a karst agricultural landscape to determine if several decades of watershed conservation and management had reversed the severe degradation caused by poor land use and catastrophic soil erosion during the 1920s and 1930s

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