Effects of riparian zone rehabilitation and stream channel modification on the macroinvertebrate community assemblage of Big Spring Run in Lancaster County, PA

Big Spring Run (BSR), a tributary of the Conestoga River, is a heavily incised, agriculturally-impaired stream located in Lancaster County, PA. Specifically, BSR has been influenced by historic mill dams constructed in the 18th century, prompting the restoration effort to remove such legacy sediments that were immobilized within the bank. During the summer of 2011, a 300m section of BSR was restored to reflect conditions prior to human impairment. The purpose of this study was to determine the impact of stream channel redesign and riparian buffer rehabilitation on structure. A BACI (Before/After/Control/Impact) sampling design was implemented to sample macroinvertebrates from three control reaches and one impact (restored) reach. A habitat assessment using the EPA-rapid bioassessment protocols for use in wadeable streams and rivers was performed before and after the stream was restored to characterize changes to the riparian zone and the stream channel, consisting of 10 different scores.  Macroinvertebrates were collected using a Surber Sampler and returned to the laboratory for sorting and identification. Six months post restoration scores for the habitat assessment that were based on in-stream and riparian zone characterizations indicated that 5 scores improved and 4 declined, with bank stability being the most significantly improved score and vegetative zone width being the most reduced score.  All invertebrate samples to the generic (Genus) level and a Macroinvertebrate Aggregated Index for Streams (MAIS) were used to determine impact within all study reaches. After six months post-restoration, there was not a significant difference between the pre- and post-restoration MAIS scores.