Abstract
Dam removal is an increasingly important method of stream restoration, but most removal efforts are under-studied in their effects. In order to better understand the effects of such removals on the stream ecosystem, we examined changes in stream macroinvertebrate communities from 2011–2016. Comparisons were focused above, below, and before and after the October 2012 removal of the Brown Bridge Dam on the Boardman River in Michigan (USA), as well as to new channel sites created in its former reservoir (2013–2015). Using linear mixed-effect models on the percent abundance of ecologically sensitive taxa (% Ephemeroptera, Plecoptera, Trichoptera (EPT)), total density of all macroinvertebrates, overall taxa richness, and Functional Feeding Groups, along with multivariate analyses on the community matrix, we examined differences in community composition among sites and years. EPT declined downstream of the dam immediately after dam removal, but recovered in the second year, becoming dominant within 2–4 years. Downstream sites before removal had different community composition than upstream sites and downstream sites after removal (p<0.001), while upstream and downstream sites after removal converged towards similarity. New channel (restored) %EPT, density, and taxa richness were not different from upstream sites in any year following removal, but new channel sites were the most distinct in community composition, possessing multiple indicator taxa characteristic of unique new conditions. The invasive New Zealand mud snail (Potamopyrgus antipodarum) was absent from all sites prior to dam removal, but appeared at low densities in upstream sites in 2013, had spread to all sites by 2015, and showed large increases at all sites by 2016. Managers employing dam removal for stream restoration should include post-removal monitoring for multiple years following removal and conduct risk analysis regarding potential effects on colonization of invasive invertebrate species.
Highlights
Watershed fragmentation is a global ecological problem and a pervasive concern in restoration because of its detrimental effects on native aquatic biodiversity [1]
The particular selection of the Boardman River was informed by the concern of Trout Unlimited for the quality of trout habitat in the Boardman River, the ongoing focus on habitat improvement and natural resource conservation on the Boardman River by the Conservation Resource Alliance, and the cultural value and heritage associated with the Boardman River by the Grand Traverse Band of Ottawa and Chippewa Indians as part of their ongoing effort to restore the Boardman River to more natural conditions as part of their ongoing restoration efforts of their historic homeland in northern Michigan
The fundamental research questions we addressed were: (1) what differences existed above and below the Brown Bridge Dam (BBD) prior to its removal; (2) how did removal of the BBD affect the composition of these communities in both short- and long-term responses, and (3) did macroinvertebrate communities above and below the BBD converge toward similarity after dam removal? Through our investigation, we determined how stream macroinvertebrate communities changed over time in response to the presence and removal of a dam
Summary
Watershed fragmentation is a global ecological problem and a pervasive concern in restoration because of its detrimental effects on native aquatic biodiversity [1]. The URL of the Grand Traverse Bay Band of Ottawa and Chippewa Indians is http://www.gtbindians. The initial design of the research was informed by the shared concern of the sponsors regarding their desire to gain a better understanding of the effects of dams on rivers in northwest Michigan. The particular selection of the Boardman River was informed by the concern of Trout Unlimited for the quality of trout habitat in the Boardman River, the ongoing focus on habitat improvement and natural resource conservation on the Boardman River by the Conservation Resource Alliance, and the cultural value and heritage associated with the Boardman River by the Grand Traverse Band of Ottawa and Chippewa Indians as part of their ongoing effort to restore the Boardman River to more natural conditions as part of their ongoing restoration efforts of their historic homeland in northern Michigan. Sponsors did not play a role in data analysis or in the decision to publish or prepare the work for publication, but did receive, as a condition of the contract, an annual report on the progress and findings of the research in each year of data collection from 2008 to 2016
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
