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Guo F, Fry B, Yan K, Huang J, Zhao Q, O'Mara K, Li F, Gao W, Kainz MJ, Brett MT, Bunn SE, Zhang Y. Assessment of the impact of dams on aquatic food webs using stable isotopes: Current progress and future challenges. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 904:167097. [PMID: 37716688 DOI: 10.1016/j.scitotenv.2023.167097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 09/10/2023] [Accepted: 09/13/2023] [Indexed: 09/18/2023]
Abstract
Dams have disrupted natural river systems worldwide and although population and community level effects on aquatic biota have been well documented, food web responses remain poorly understood and difficult to characterize. The application of stable isotope analysis (SIA) provides a means to assess the effect of dams on food webs. Here we review the effect of dams on aquatic food webs using SIA, aiming to detect knowledge gaps in the field of dam impacts on aquatic food webs and propose a conceptual framework to help formulate hypotheses about dam impacts on food webs guided by food web theory. Dams can affect aquatic food webs via two pathways: a bottom-up pathway with altered basal food sources and their transfer to consumers through changes in flow, nutrients, temperature and sediment, and a top-down pathway with consumer species composition altered mainly through habitat fragmentation and related physiochemical changes. Taking these mechanisms into consideration, the impact of dams on food web attributes derived from SIA was evaluated. These studies generally apply mixing models to determine how dams alter the dominant carbon sources supporting food webs, use δ15N to examine how dams alter food-chain length, or use Layman metrics of isotope variability to assess niche changes for invertebrate and fish assemblages. Most studies compare the patterns of SIA metrics spatially (e.g. upstream vs reservoir vs downstream of dams; regulated vs unregulated rivers) and temporally (before vs after dam construction), without explicit hypotheses and/or links to theoretical concepts of food webs. We propose several steps to make SIA studies of dam impacts more rigorous and enhance their potential for producing novel insights. Future studies should quantify the shape and strength of the effect of dams on SIA-measured food web response, be conducted at larger temporal and spatial scales (particularly along the river longitudinal continuum and the lateral connected ecosystems (e.g., floodplains)), and consider effects of dams on food web resilience and tipping points.
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Affiliation(s)
- Fen Guo
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China.
| | - Brian Fry
- Australian Rivers Institute, Griffith University, Nathan, Qld 4109, Australia
| | - Keheng Yan
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Juan Huang
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Qian Zhao
- Institute of Environment and Ecology, Shandong Normal University, Jinan 250358, China
| | - Kaitlyn O'Mara
- Australian Rivers Institute, Griffith University, Nathan, Qld 4109, Australia
| | - Feilong Li
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Wei Gao
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Martin J Kainz
- WasserCluster Lunz - Inter-University Centre for Aquatic Ecosystem Research, Lunz am See, Austria
| | - Michael T Brett
- Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USA
| | - Stuart E Bunn
- Australian Rivers Institute, Griffith University, Nathan, Qld 4109, Australia
| | - Yuan Zhang
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
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Swalethorp R, Landry MR, Semmens BX, Ohman MD, Aluwihare L, Chargualaf D, Thompson AR. Anchovy boom and bust linked to trophic shifts in larval diet. Nat Commun 2023; 14:7412. [PMID: 38052790 DOI: 10.1038/s41467-023-42966-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 10/27/2023] [Indexed: 12/07/2023] Open
Abstract
Although massive biomass fluctuations of coastal-pelagic fishes are an iconic example of the impacts of climate variability on marine ecosystems, the mechanisms governing these dynamics are often elusive. We construct a 45-year record of nitrogen stable isotopes measured in larvae of Northern Anchovy (Engraulis mordax) in the California Current Ecosystem to assess patterns in food chain length. Larval trophic efficiency associated with a shortened food chain increased larval survival and produced boom periods of high adult biomass. In contrast, when larval food chain length increased, and energy transfer efficiency decreased, the population crashed. We propose the Trophic Efficiency in Early Life (TEEL) hypothesis, which states that larval fishes must consume prey that confer sufficient energy for survival, to help explain natural boom-bust dynamics of coastal pelagic fishes. Our findings illustrate a potential for trophic indicators to generally inform larval survival and adult population dynamics of coastal-pelagic fishes.
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Affiliation(s)
- Rasmus Swalethorp
- Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA.
- NOAA Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA.
- National Institute of Aquatic Resources (DTU Aqua), Technical University of Denmark, Kgs., Lyngby, Denmark.
| | - Michael R Landry
- Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA
| | - Brice X Semmens
- Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA
| | - Mark D Ohman
- Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA
| | - Lihini Aluwihare
- Scripps Institution of Oceanography, University of California - San Diego, La Jolla, CA, USA
| | - Dereka Chargualaf
- NOAA Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA
| | - Andrew R Thompson
- NOAA Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA
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