Restoring the natural habitat of American rivers and streams is a crucial multi-billion dollar effort. A large portion of that revenue is directed toward Washington State’s Columbia River Basin to aid in the recovery of vulnerable salmon and steelhead populations. Less understood is how well those projects actually improve the environment for a variety of aquatic species.
Alex Fremier, Washington State University ecologist, is leading a study to examine how restoration projects—such as installing logjams in stream channels—can enrich the nutrient levels of complex aquatic food webs. Poor nutrient levels have been shown to decrease survival rates of salmon migrating to the ocean.
Logjams improve habitat by slowing both surface and subsurface waters and creating recirculating eddies as the water travels downstream. This leads to changes in organic matter and fine sediment deposition, which, in turn, affect nutrient storage in the stream. Healthy nutrient levels translate to healthy fish populations.
Working with the U.S Bureau of Reclamation, Fremier’s team is investigating the impacts from logjams placed in Washington’s Tucannon River in the southeast and the Methow River in the north—both areas experiencing low returns of spawning Chinook salmon. From these data, Fremier is developing an in depth understanding of nutrient retention and fish reproduction in relation to stream restoration practices.