Dams on headwater streams in the Fayetteville Shale region of Arkansas are often built to enable water withdrawal for hydraulic fracturing. Dams have been shown to change the hydrology, chemistry, and habitat connectivity of streams, but these effects have not been well-researched in these first order streams. Alterations in physicochemical conditions can affect macroinvertebrate communities and their associated ecosystem functions. We measured physicochemical and biological variables in three dammed headwater streams and compared these metrics to three undammed reference streams. Since aquatic organisms are often adapted to flow regimes typical for their area, we hypothesized that dams would change the physicochemical qualities of these streams so that species diversity and evenness would decline.
Results/Conclusions
We found that dammed streams demonstrated trends for lower discharge and soluble reactive phosphorous. Conversely, damned streams had trends of higher mean temperature, specific conductivity, and percent dissolved oxygen. The mean Shannon diversity index for benthic macroinvertebrates was greater and rank abundance curves revealed greater taxa evenness in dammed compared to undammed streams. Overall macroinvertebrate total abundance did not differ between treatments; however, streams with dams tended to have greater collector-gatherer abundance than undammed streams (mean abundance of 20 versus 3) that may be from a combination of altered physicochemical conditions. Therefore, our study suggests that damming small headwater streams can affect the physicochemical and biological conditions that influence stream ecosystem function and structure. Considering the large number of dams constructed in the Fayetteville Shale region, it is likely that a large proportion of headwater streams have been altered.