Poster Presentation Society for Freshwater Science 2025 Annual Meeting

Assessing Ecological Integrity Following Stream Restoration (118266)

Nancy Roth 1 , Jeff White 1 , Jil Swearingen 1 , David Neely 1 , James Stribling 1 , John McCoy 2
  1. Tetra Tech, Owings Mills, Maryland, United States
  2. Columbia Association, Columbia, Maryland, United States

Restoring degraded streams can reduce stressors and restore functions, which may ultimately improve ecological condition. Pre-construction conditions at a tributary to Little Patuxent River in Columbia, Maryland, USA included high rates of active erosion, with unstable channels producing excessive sediment loads. Two years post-restoration, we conducted riparian, fish, and instream habitat assessments to evaluate conditions in restored and comparison reaches. Modified belt transects were established to characterize riparian vegetation, where we identified 76 native and 24 invasive species. The most common non-native species in both restored and unrestored areas were Japanese stiltgrass (Microstegium vimineum) and wavyleaf basketgrass (Oplismenus undulatifolius). Along with native plants installed during restoration, many native species have established through natural recruitment (20 woody and many herbaceous species). We recommend controlling invasive species from further spread, including hand weeding. Also, long-term establishment of a canopy with sufficient shade would help minimize invasive herbaceous species. Fish and physical habitat assessments followed guidelines of the Maryland Department of Natural Resources’ Maryland Biological Stream Survey (MBSS). We observed 658 individuals of nine species of fishes, all common inhabitants of headwaters in the Maryland Piedmont. We compared Fish Index of Biotic Integrity values against 57 regional sites sampled by MBSS between 1997-2023. Scores fell into Very Poor or Poor ranges, below the MBSS mean score. The restored reach scored higher than unrestored sites. Narrative habitat ratings of "partially degraded" were recorded, with scores falling within the range of MBSS scores. The overall low fish species diversity is likely due to sites’ position within the watershed, historical degradation, and the presence of impoundments just downstream that serve as a barrier to fishes that might otherwise recolonize the restored habitat. While habitat restoration may have indeed improved habitat conditions, lacking source populations to support recolonization, little further recovery of the fish community is likely.