Hypoxia vulnerability in the salmon watersheds of Southeast Alaska.

Autor: Sergeant CJ; College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Point Lena Loop Rd, Juneau, AK 99801, USA; Flathead Lake Biological Station, University of Montana, 32125 Bio Station Ln, Polson, MT 59860-6815, USA. Electronic address: christopher.sergeant@umontana.edu., Bellmore JR; U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, 11175 Auke Lake Way, Juneau, AK 99801, USA. Electronic address: james.r.bellmore@usda.gov., Bellmore RA; Southeast Alaska Watershed Coalition, 1107 W 8th St, Juneau, AK 99801, USA. Electronic address: rebecca@sawcak.org., Falke JA; U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, 2140 Koyukuk Drive, Fairbanks, AK 99775-7020, USA. Electronic address: jeffrey.falke@alaska.edu., Mueter FJ; College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Point Lena Loop Rd, Juneau, AK 99801, USA. Electronic address: fmueter@alaska.edu., Westley PAH; College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 2150 Koyukuk Drive, Fairbanks, AK 99775, USA. Electronic address: pwestley@alaska.edu.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2023 Oct 20; Vol. 896, pp. 165247. Date of Electronic Publication: 2023 Jul 02.
DOI: 10.1016/j.scitotenv.2023.165247
Abstrakt: The frequency of dissolved oxygen depletion events (hypoxia) in coastal aquatic ecosystems has risen dramatically since the late 20th century, yet the causes and consequences of hypoxia for some culturally and economically important species remain poorly understood. In rivers, oxygen depletion can be caused by high densities of spawning Pacific salmon (Oncorhynchus spp.) consuming oxygen faster than can be replaced by reaeration. This process may be exacerbated when salmon densities are artificially inflated, such as when hatchery-origin salmon stray into rivers instead of returning to hatcheries. In Southeast Alaska, hatchery salmon production has increased rapidly since the 1970s, with over 553 million chum salmon (O. keta) and 64 million pink salmon (O. gorbuscha) released in 2021 alone. Straying is pervasive in streams with outlets <25 km from nearshore marine hatchery release sites. Using a previously ground-truthed mechanistic model of dissolved oxygen dynamics, we examined how water temperature and low-flow channel hydraulics contribute to hypoxia vulnerability. We then applied the model to predict hypoxia vulnerability for watersheds within 25 km of hatchery salmon release points, where straying salmon spawner densities are expected to be higher and promote dissolved oxygen depletion. Our model predicted that low-gradient stream reaches, regardless of water temperature, are the most prone to hypoxia due to low reaeration rates. Our spatial analysis determined that nearly 17,000 km of anadromous-accessible stream reaches are vulnerable to high densities of hatchery-origin salmon based on 2021 release sites. To our knowledge, this study is the first to map the spatial variation of hypoxia vulnerability in anadromous watersheds, identify habitat conditions most likely to promote hypoxia, and provide a repeatable analytical approach to identify hypoxia-prone stream reaches that can be updated as empirical data sets improve.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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