Spawning habitat characteristics and egg mortality in relation to river geomorphology and run-times of chum salmon (Oncorhynchus keta) in a metropolitan river system, northern Japan

Aruga, Nozomi; Morita, Kentaro; Aruga, Makoto; Ueda, Kazutoshi; Fujii, Kanji; Orito, K.; Watanabe, Keizo; Nakamura, Futoshi

doi:10.1007/s10641-023-01415-z

Cited by 3 publications

References 56 publications

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Macroinvertebrate response to run‐of‐river hydropower tailrace inflow: Spatial assessment of community and traits

Mihara,

Negishi,

2024

River Research & Apps

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Run‐of‐river (R‐O‐R) hydropower dams introduce two discontinuities in the river: the dam and the tailrace. Discontinuities can lead to changes in the water quality that may affect the survival of aquatic macroinvertebrates, depending on their traits. We investigated the invertebrate assemblage and community‐level traits in an urban river influenced by a small hydropower tailrace in Hokkaido, Japan. As a result of the tailrace inflow to the main channel, the bypassed reach was warmer, and the areas below the confluence were colder. Temperature was a consistent factor affecting the distribution of indicator taxa and of the five major taxa that contributed the most to dissimilarity, but other environmental factors also showed significant effects. At the community level, the weighted mean of taxa with warm preference showed a significant positive relationship with temperature, but taxa with cold preference did not appear to be filtered by the cold water delivered by the tailrace. However, sensitive taxa such as Ephemerella have already started showing negative responses to temperature. The observed distribution of cold‐preferring scrapers could negatively affect the energy transfer from primary producers to higher consumers in the bypassed reach. Appropriate mitigation of climate change effects in hydropower systems can be achieved by increasing the flow in the bypassed reach, especially during the summer months, to maintain a temperature regime that is adequate for the survival of macroinvertebrate populations and maintenance of ecosystem functions.

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Macroinvertebrate response to run‐of‐river hydropower tailrace inflow: Spatial assessment of community and traits

Mihara,

Negishi,

2024

River Research & Apps

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An urbanized phantom tributary subsidizes river-riparian communities of mainstem gravel-bed river

Negishi,

Song,

Matsubara

et al. 2023

Preprint

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Urbanization transforms natural river channels, and some rivers become invisible over time. How and whether the subsurface domains of the original waterways and aquifers connecting them (a phantom of historical landscape) are functional is not known. This study examined the effects of tributary groundwater (GW) inflow on the response of river-riparian organisms in an alluvial mainstem river in northern Japan, where the tributary disappeared over the course of urban landscape transformation.A 2.8-km long lowland segment of the mainstem gravel-bed river was examined for water properties and the river-riparian food web. In addition, watershed-wide water sampling was conducted to isotopically distinguish several types of groundwater that contributed to the hyporheic water in the study segment. There was a clear effect of altitude on the hydrogen/oxygen stable isotope ratios in the river water collected across the watershed.Groundwater unique both in chemical sand isotopic signatures in several spots occurred within the study segment, and its properties resembled to and its upwelling locations matched groundwater from a tributary river whose surface channel has disappeared 60 years ago. Positive numerical increases in abundance and/or a sign of nitrogen transfer in river riparian communities (algae, invertebrates, and riparian trees) originating from groundwater high in nitrate with elevated nitrogen stable isotope ratios were found.This study demonstrated that tributary groundwater with unique chemical properties manifested by an urban watershed river network continued to have cascading effects on biota across the river-riparian boundary in the mainstem river, even after urbanization transformed the tributary into a historically lost phantom river. We highlighted the legacy effects of landscape transformation in the subsurface domain and the significance of scrutinizing the past landscape and hydrological connectivity at the watershed scale in urban environments.

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An urbanized phantom tributary subsidizes river–riparian communities of a mainstem gravel‐bed river

Negishi,

Song,

Matsubara

et al. 2024

Freshwater Biology

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Urbanization transforms natural river channels, and surface water of some rivers disappeared over time. How and whether the subsurface domains of the original waterways and aquifers connecting them (a phantom of historical landscape) are functional is not known. This study examined the effects of tributary groundwater inflow on the response of river–riparian organisms in an alluvial mainstem river in northern Japan, where the tributary disappeared over the course of urban landscape transformation. A 2.8‐km lowland segment of the mainstem gravel‐bed river was examined for water properties and the river–riparian food web. In addition, watershed‐wide water sampling was conducted to isotopically distinguish several types of groundwater that contributed to the hyporheic water in the study segment. Altitude had a clear effect on the hydrogen/oxygen stable isotope ratios in the river water collected across the watershed. Groundwater unique both in chemical and isotopic signatures occurred in several spots within the study segment, and its properties resembled and its upwelling locations matched groundwater from a tributary river whose surface channel disappeared 60 years ago. Positive numerical increases in abundance and/or a sign of nitrogen transfer in river–riparian communities (algae, invertebrates and riparian trees) originating from groundwater high in nitrate with elevated nitrogen stable isotope ratios were found. We demonstrated that tributary groundwater with unique chemical properties manifested by an urban watershed river network continued to have trophic effects on biota across the river–riparian boundary in the mainstem river, even after urbanization transformed the tributary into a phantom river. We highlighted the legacy effects of landscape transformation in the subsurface domain and the significance of scrutinizing the past landscape and hydrological connectivity at the watershed scale in urban environments.

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Spawning habitat characteristics and egg mortality in relation to river geomorphology and run-times of chum salmon (Oncorhynchus keta) in a metropolitan river system, northern Japan

Cited by 3 publications

References 56 publications

Macroinvertebrate response to run‐of‐river hydropower tailrace inflow: Spatial assessment of community and traits

Macroinvertebrate response to run‐of‐river hydropower tailrace inflow: Spatial assessment of community and traits

An urbanized phantom tributary subsidizes river-riparian communities of mainstem gravel-bed river

An urbanized phantom tributary subsidizes river–riparian communities of a mainstem gravel‐bed river

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