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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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Park TH, Lee CI, Kim TH, Kim D, Park HJ. Trophic response of fishes to rainfall variability in a temperate estuarine system of Korea: A stable isotope approach. MARINE POLLUTION BULLETIN 2023; 193:115183. [PMID: 37369155 DOI: 10.1016/j.marpolbul.2023.115183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 06/12/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023]
Abstract
To assess the basal resources supporting food webs impacted by rainfalls, we compared stable isotope ratios (δ13C and δ15N) of fish consumers and organic matter sources between up- and down-sites in an estuary between seasons (June and September) and years (2018 and 2019) that showed different patterns of summer monsoon. Our study showed seasonal differences in the δ13C and δ15N values of basal resources and fish consumers in both years. At the up-site, significant differences of δ13C values of fish consumers were found between years, resulting from changing rainfall period, thereby causing a shift in food availability from terrigenous organic matter to periphyton. In contrast, at the down-site, the consistent isotopic values of fishes were observed in both years, suggesting that rainfall shift has a negligible impact on resources for fishes. Overall, the annual shift in resources for fishes in the estuary may be controlled by contrasting rainfall events.
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Affiliation(s)
- Tae Hee Park
- Department of Marine Ecology and Environment, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
| | - Chung Il Lee
- Department of Marine Ecology and Environment, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
| | - Tae-Hoon Kim
- Department of Oceanography, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Dongyoung Kim
- School of Earth Science & Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Hyun Je Park
- Department of Marine Ecology and Environment, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea.
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Ru H, Zhong L, Nian W, Li Y, Sheng Q, Ni Z. Variations of trophic structure and niche space in fish community along a highly regulated subtropical large river. Ecol Evol 2022; 12:e9424. [PMID: 36311401 PMCID: PMC9596329 DOI: 10.1002/ece3.9424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 09/22/2022] [Accepted: 09/27/2022] [Indexed: 11/22/2022] Open
Abstract
The trophic interactions between consumers and resources play a vital role in the stability of communities. In river systems, fragmentation of natural habitats and environmental changes alters the energy basis and community composition, consequently leading to variations in the community's trophic structure and niche space. However, our understanding of how the trophic structure responds to environmental changes is still very limited. Here, based on stable isotope data, we explored and compared trophic positions (TPs), community‐wide trophic metrics, and isotope niche space of fish communities in three reaches with different hydrogeomorphic conditions along a highly regulated subtropical river over three seasons. The community trophic structure and niche space showed notable spatiotemporal variations. Overall, the downstream reach had lower TPs, trophic diversity but higher trophic redundancy. The middle reach occupied a wider isotope niche space than other reaches, with the largest niche size during autumn. Furthermore, the niche overlap was relatively high in winter between reaches and in the downstream between seasons. The results implied a homogenization of feeding functional groups and energy flow pathways of species in the downstream community associated with the change of energy source and stability of hydrological conditions. The relationship between trophic structure and environmental factors suggested that the dam‐induced alteration in hydrological‐related aspects may drive the changes in the functional group composition, together with changes in energy basis, resulting in differences in the trophic structure of the community. The results of the present study deepen our understanding of how ecosystem functions respond to disturbance, thus contributing to improved ability to conserve river ecosystems.
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Affiliation(s)
- Huijun Ru
- Fishery Eco-Environment Monitoring Center in Middle and Upper Reaches of Yangtze River Ministry of Agriculture and Rural Affairs of China/Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Science Wuhan China
| | - Liqiao Zhong
- Fishery Eco-Environment Monitoring Center in Middle and Upper Reaches of Yangtze River Ministry of Agriculture and Rural Affairs of China/Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Science Wuhan China
| | - Wei Nian
- Fishery Eco-Environment Monitoring Center in Middle and Upper Reaches of Yangtze River Ministry of Agriculture and Rural Affairs of China/Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Science Wuhan China
| | - Yunfeng Li
- Fishery Eco-Environment Monitoring Center in Middle and Upper Reaches of Yangtze River Ministry of Agriculture and Rural Affairs of China/Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Science Wuhan China
| | - Qiang Sheng
- Zhejiang Province Key Laboratory of Aquatic Resources Conservation and Development, College of Life Sciences Huzhou University Huzhou China
| | - Zhaohui Ni
- Fishery Eco-Environment Monitoring Center in Middle and Upper Reaches of Yangtze River Ministry of Agriculture and Rural Affairs of China/Yangtze River Fisheries Research Institute, Chinese Academy of Fisheries Science Wuhan China
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Moyo S, Jacobs DS. Faecal analyses and alimentary tracers reveal the foraging ecology of two sympatric bats. PLoS One 2020; 15:e0227743. [PMID: 31945139 PMCID: PMC6964858 DOI: 10.1371/journal.pone.0227743] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 12/28/2019] [Indexed: 12/02/2022] Open
Abstract
We used three complementary methods to assess the diet of two insectivorous bat species: one an obligate aerial hunter, Miniopterus natalensis, and the other Myotis tricolor whose morphology and taxonomic affiliation to other trawling bats suggests it may be a trawler (capturing insects from the water surface with its feet and tail). We used visual inspection, stable isotope values and fatty acid profiles of insect fragments in bat faeces sampled across five sites to determine the contribution of aquatic and terrestrial arthropods to the diets of the two species. The niche widths of M. tricolor were generally wider than those of Miniopterus natalensis but with much overlap, both taking aquatic and terrestrial insects, albeit in different proportions. The diet of M. tricolor had high proportions of fatty acids (20:5ω3 and 22:6ω3) that are only obtainable from aquatic insects. Furthermore, the diet of M. tricolor had higher proportions of water striders (Gerridae) and whirligig beetles (Gyrinidae), insects obtainable via trawling, than Miniopterus natalensis. These results suggest both species are flexible in their consumption of prey but that M. tricolor may use both aerial hawking and trawling, or at least gleaning, to take insects from water surfaces. The resultant spatial segregation may sufficiently differentiate the niches of the two species, allowing them to co-exist. Furthermore, our results emphasize that using a combination of methods to analyse diets of cryptic animals yields greater insights into animal foraging ecology than any of them on their own.
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Affiliation(s)
- Sydney Moyo
- Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa
| | - David S. Jacobs
- Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa
- * E-mail:
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