Shifting food web structure during dam removal-Disturbance and recovery during a major restoration action.

Autor: Morley SA; Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America., Foley MM; United States Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California, United States of America., Duda JJ; United States Geological Survey, Western Fisheries Research Center, Seattle, Washington, United States of America., Beirne MM; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Paradis RL; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Johnson RC; United States Geological Survey, Western Fisheries Research Center, Seattle, Washington, United States of America., McHenry ML; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Elofson M; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Sampson EM; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., McCoy RE; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Stapleton J; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, Washington, United States of America., Pess GR; Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington, United States of America.
Jazyk: angličtina
Zdroj: PloS one [PLoS One] 2020 Sep 29; Vol. 15 (9), pp. e0239198. Date of Electronic Publication: 2020 Sep 29 (Print Publication: 2020).
DOI: 10.1371/journal.pone.0239198
Abstrakt: We measured food availability and diet composition of juvenile salmonids over multiple years and seasons before and during the world's largest dam removal on the Elwha River, Washington State. We conducted these measurements over three sediment-impacted sections (the estuary and two sections of the river downstream of each dam) and compared these to data collected from mainstem tributaries not directly affected by the massive amount of sediment released from the reservoirs. We found that sediment impacts from dam removal significantly reduced invertebrate prey availability, but juvenile salmon adjusted their foraging so that the amount of energy in diets was similar before and during dam removal. This general pattern was seen in both river and estuary habitats, although the mechanisms driving the change and the response differed between habitats. In the estuary, the dietary shifts were related to changes in invertebrate assemblages following a hydrological transition from brackish to freshwater caused by sediment deposition at the river's mouth. The loss of brackish invertebrate species caused fish to increase piscivory and rely on new prey sources such as plankton. In the river, energy provided to fish by Ephemeroptera, Plecoptera, and Trichoptera taxa before dam removal was replaced first by terrestrial invertebrates, and then by sediment-tolerant taxa such as Chironomidae. The results of our study are consistent with many others that have shown sharp declines in invertebrate density during dam removal. Our study further shows how those changes can move through the food web and affect fish diet composition, selectivity, and energy availability. As we move further along the dam removal response trajectory, we hypothesize that food web complexity will continue to increase as annual sediment load now approaches natural background levels, anadromous fish have recolonized the majority of the watershed between and above the former dams, and revegetation and microhabitats continue to develop in the estuary.
Competing Interests: The authors have declared that no competing interests exist.
Databáze: MEDLINE
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