Emmanuel Jaulin Gautronneau, Abdelkader Azougui, Antoine Callu, Hervé Capra, Maxime Logez, Hervé Pella, Maria Alp
Hydropeaking, associated with flexible hydropower, produces frequent and dramatic water-level fluctuations causing repeated drying of shallow areas near river banks and gravel bars. These marginal habitats are crucial for the reproduction of many aquatic and semi-aquatic species including insects, whose complex life cycles involve transitions between aquatic and terrestrial environments. The sensitivity of stream insects to sub-daily variation in flow velocity and water levels induced by hydropeaking has mainly been assessed for larvae, whereas the sensitivity of adults and eggs remains largely unknown. For species that attach their egg masses to substrates in shallow waters, fluctuating water levels could expose eggs to air, causing desiccation and mortality. Such hydropeaking-driven constraints may determine population-level reproductive success and potentially lead to population bottlenecks. The aim of this study was to determine the sensitivity of stream insect eggs to dry phases.
An experiment was performed with Baetis spp. mayfly egg masses in flumes. Egg masses from a wild population were exposed to one of 10 treatments: a dry phase lasting between 1 and 18 h or a control treatment with no dry phase. The treatment was followed by an incubation period in controlled conditions allowing for development and hatching of viable eggs. The hatching proportion was calculated for each individual egg mass based on automated counting of the total number of eggs per mass and manual counting of the number of either hatched or unhatched eggs per mass.
A mean of 88%–98% of eggs hatched after 0–5 h dry phases. The proportion declined to 45% after 6 h then to near zero after 9 h dry phases. Dense hyphae developed on egg masses exposed to dry phases lasting 6–18 h.
Our study provides some of the first estimates of stream insect egg mass responses to dry phases under optimal and reproducible controlled conditions. Hatching failure at dry-phase durations ≥ 6 h was likely due to desiccation-induced egg mortality, which then allowed for the growth of aquatic oomycete hyphae, stream-dwelling decomposers of organic matter.
We highlight the need to consider impacts of flow regulation—and specifically, artificial dry phases associated with hydropeaking operations—on all life stages of aquatic organisms to inform sustainable management strategies that support biodiversity within regulated rivers.
{"title":"Exposure to Short Dry Phases Prevents Hatching of Mayfly Egg Masses","authors":"Emmanuel Jaulin Gautronneau, Abdelkader Azougui, Antoine Callu, Hervé Capra, Maxime Logez, Hervé Pella, Maria Alp","doi":"10.1111/fwb.70178","DOIUrl":"10.1111/fwb.70178","url":null,"abstract":"<div>\u0000 \u0000 <p>\u0000 \u0000 </p><ol>\u0000 \u0000 \u0000 <li>Hydropeaking, associated with flexible hydropower, produces frequent and dramatic water-level fluctuations causing repeated drying of shallow areas near river banks and gravel bars. These marginal habitats are crucial for the reproduction of many aquatic and semi-aquatic species including insects, whose complex life cycles involve transitions between aquatic and terrestrial environments. The sensitivity of stream insects to sub-daily variation in flow velocity and water levels induced by hydropeaking has mainly been assessed for larvae, whereas the sensitivity of adults and eggs remains largely unknown. For species that attach their egg masses to substrates in shallow waters, fluctuating water levels could expose eggs to air, causing desiccation and mortality. Such hydropeaking-driven constraints may determine population-level reproductive success and potentially lead to population bottlenecks. The aim of this study was to determine the sensitivity of stream insect eggs to dry phases.</li>\u0000 \u0000 \u0000 <li>An experiment was performed with <i>Baetis</i> spp. mayfly egg masses in flumes. Egg masses from a wild population were exposed to one of 10 treatments: a dry phase lasting between 1 and 18 h or a control treatment with no dry phase. The treatment was followed by an incubation period in controlled conditions allowing for development and hatching of viable eggs. The hatching proportion was calculated for each individual egg mass based on automated counting of the total number of eggs per mass and manual counting of the number of either hatched or unhatched eggs per mass.</li>\u0000 \u0000 \u0000 <li>A mean of 88%–98% of eggs hatched after 0–5 h dry phases. The proportion declined to 45% after 6 h then to near zero after 9 h dry phases. Dense hyphae developed on egg masses exposed to dry phases lasting 6–18 h.</li>\u0000 \u0000 \u0000 <li>Our study provides some of the first estimates of stream insect egg mass responses to dry phases under optimal and reproducible controlled conditions. Hatching failure at dry-phase durations ≥ 6 h was likely due to desiccation-induced egg mortality, which then allowed for the growth of aquatic oomycete hyphae, stream-dwelling decomposers of organic matter.</li>\u0000 \u0000 \u0000 <li>We highlight the need to consider impacts of flow regulation—and specifically, artificial dry phases associated with hydropeaking operations—on all life stages of aquatic organisms to inform sustainable management strategies that support biodiversity within regulated rivers.</li>\u0000 </ol>\u0000 \u0000 </div>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146136913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Issue Information - Cover and Ed Board","authors":"","doi":"10.1111/fwb.70176","DOIUrl":"10.1111/fwb.70176","url":null,"abstract":"","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70176","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146130377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Effects of Lateral Hydrological Connectivity on the Taxonomic and Functional Structure of Fish Communities in Saône River Floodplains (France): Implications for Non-Native Species Distribution","authors":"Yann Lelièvre, Emilien Gaigné, Gaël Grenouillet, Guillaume Mortreux, Jérôme Moreau, Jean-Philippe Couasné, Julien Maupoux, Sébastien Motreuil, Rémi Wattier, Maria Teixeira, François-Xavier Dechaume-Moncharmont, Loïc Bollache","doi":"10.1111/fwb.70175","DOIUrl":"https://doi.org/10.1111/fwb.70175","url":null,"abstract":"<p>\u0000 \u0000 </p>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70175","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146130042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tauany Rodrigues, Vinicius F. Farjalla, Juliana S. Leal, Helena A. Prado, Aliny P. F. Pires
{"title":"Multiple Threats Have Overlapping Impacts Across Ecological Levels in Freshwater Ecosystems","authors":"Tauany Rodrigues, Vinicius F. Farjalla, Juliana S. Leal, Helena A. Prado, Aliny P. F. Pires","doi":"10.1111/fwb.70174","DOIUrl":"https://doi.org/10.1111/fwb.70174","url":null,"abstract":"<p>\u0000 \u0000 </p>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70174","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146130033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Diana Rojo, Alberto Alonso, Javier Pérez, Brais Hermosilla, Agustí Agut, Maite Orruño, Inés Arana, Luz Boyero
We evaluated whether riparian forest restoration could mitigate the impacts of agricultural land use on key stream ecosystem processes (total and microbial leaf litter decomposition and periphytic algal biomass accrual) and associated assemblages (invertebrates, aquatic hyphomycetes, and periphytic algae) in three streams located in northern Spain.
At each stream we studied three sites with different levels of impact: a control site (no impact), an altered site (surrounded by agricultural crops with no riparian vegetation), and a restored site (also located in agricultural land but having riparian vegetation because of restoration).
Compared to altered sites, restored sites showed lower nutrient levels and distinct biological assemblages, with taxa more typical of good environmental conditions. Despite large differences among streams in terms of local environmental conditions (e.g., stream intermittency), there was an overall trend for faster leaf litter decomposition at restored compared to altered sites, and the former showed the highest rates of aquatic hyphomycete sporulation and periphyton accrual.
Our results suggested an improvement of stream ecological condition due to riparian restoration, for several reasons: water quality was partly improved; leaf litter inputs allowed invertebrate and aquatic hyphomycete assemblages to be more similar to those of control sites, and greater rates of leaf litter decomposition; and algal assemblages were not negatively affected, which maintained the stream self-purification capacity.
Restoration of the riparian forest could be an effective management strategy for improving the ecological condition of streams impacted by agricultural activities, although effects are context-dependent and influenced by site-specific factors, which suggests that proper planning and monitoring are needed in each case.
{"title":"Restoration of Riparian Vegetation Can Mitigate Impacts of Agricultural Land Use on Stream Ecosystems","authors":"Diana Rojo, Alberto Alonso, Javier Pérez, Brais Hermosilla, Agustí Agut, Maite Orruño, Inés Arana, Luz Boyero","doi":"10.1111/fwb.70163","DOIUrl":"https://doi.org/10.1111/fwb.70163","url":null,"abstract":"<div>\u0000 \u0000 <p>\u0000 \u0000 </p><ol>\u0000 \u0000 \u0000 <li>We evaluated whether riparian forest restoration could mitigate the impacts of agricultural land use on key stream ecosystem processes (total and microbial leaf litter decomposition and periphytic algal biomass accrual) and associated assemblages (invertebrates, aquatic hyphomycetes, and periphytic algae) in three streams located in northern Spain.</li>\u0000 \u0000 \u0000 <li>At each stream we studied three sites with different levels of impact: a control site (no impact), an altered site (surrounded by agricultural crops with no riparian vegetation), and a restored site (also located in agricultural land but having riparian vegetation because of restoration).</li>\u0000 \u0000 \u0000 <li>Compared to altered sites, restored sites showed lower nutrient levels and distinct biological assemblages, with taxa more typical of good environmental conditions. Despite large differences among streams in terms of local environmental conditions (e.g., stream intermittency), there was an overall trend for faster leaf litter decomposition at restored compared to altered sites, and the former showed the highest rates of aquatic hyphomycete sporulation and periphyton accrual.</li>\u0000 \u0000 \u0000 <li>Our results suggested an improvement of stream ecological condition due to riparian restoration, for several reasons: water quality was partly improved; leaf litter inputs allowed invertebrate and aquatic hyphomycete assemblages to be more similar to those of control sites, and greater rates of leaf litter decomposition; and algal assemblages were not negatively affected, which maintained the stream self-purification capacity.</li>\u0000 \u0000 \u0000 <li>Restoration of the riparian forest could be an effective management strategy for improving the ecological condition of streams impacted by agricultural activities, although effects are context-dependent and influenced by site-specific factors, which suggests that proper planning and monitoring are needed in each case.</li>\u0000 </ol>\u0000 \u0000 </div>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Willem Goedkoop, Sebastian Höss, Fernando Chaguaceda, Kirsten S. Christoffersen, Walter Traunspurger
{"title":"Epilithic Algal and Meiofaunal Assemblages of Arctic/Alpine Lakes and Streams Along Latitudinal and Environmental Gradients in Scandinavia","authors":"Willem Goedkoop, Sebastian Höss, Fernando Chaguaceda, Kirsten S. Christoffersen, Walter Traunspurger","doi":"10.1111/fwb.70172","DOIUrl":"https://doi.org/10.1111/fwb.70172","url":null,"abstract":"<p>\u0000 \u0000 </p>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70172","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146091112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tereza Novotná Jaroměřská, Ljuba Poláková, Travis B. Meador, Karel Janko, Miloslav Devetter
{"title":"Exploring the Dietary Preferences of Limnic Supraglacial Consumers: 13C and 15N Isotopic Food Labelling in Tardigrades and Rotifers From Cryoconite Holes","authors":"Tereza Novotná Jaroměřská, Ljuba Poláková, Travis B. Meador, Karel Janko, Miloslav Devetter","doi":"10.1111/fwb.70170","DOIUrl":"https://doi.org/10.1111/fwb.70170","url":null,"abstract":"<p>\u0000 \u0000 </p>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70170","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ben R. J. Crichton, Michael J. H. Hickford, Angus R. McIntosh, David R. Schiel
{"title":"Fishing-Induced Regulation of Diadromous Fish Subsidies in Stream Communities","authors":"Ben R. J. Crichton, Michael J. H. Hickford, Angus R. McIntosh, David R. Schiel","doi":"10.1111/fwb.70166","DOIUrl":"https://doi.org/10.1111/fwb.70166","url":null,"abstract":"<p>\u0000 \u0000 </p>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/fwb.70166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By modifying the physical environment, ecosystem engineers influence a wide variety of ecological processes, affecting other species both directly (e.g., providing sites for reproduction, hibernation, and refuge) and indirectly (e.g., mediating availability of resources by altering food web dynamics). The beaver (Eurasian, Castor fiber, and North American, C. canadensis) provides a textbook example of an ecosystem engineer, restructuring the physical fluvial and riparian environment by constructing dams, bankside burrows, lodges, and canals.
The indirect secondary consequences of beaver activity for other species can be difficult to determine. Beaver ponds can benefit fish, such as through the provision of refuge from predators due to increased depth and instream woody structure. Conversely, the formation of deep pools may create habitat for large predatory fish and suitable foraging sites for piscivorous mammalian and avian predators. As a result, the relative costs and benefits for specific life-stages and species can be difficult to disentangle.
Focusing predominantly on Grey Heron (Ardea cinerea) and brown trout (Salmo trutta) as the predator–prey model, this study explored how predation pressure differed between four study reaches situated on two co-located streams connected to a common loch in Northern Scotland.
One of the two inflowing streams was (i) modified by Eurasian beaver activity. There were also three unmodified (control) reaches comprising: (ii) the second inflowing stream, (iii) a reach above the modified inflowing section, where the influence of dams was deemed to have ceased, and (iv) the stream flowing out of the loch. Trail cameras monitored how predator presence differed spatially (between the control and modified reaches) and temporally (between seasons). Heron abundance differed both spatially and temporally, being: (a) greater at the beaver modified than control sites; (b) positively correlated with 1+ age group trout (but not when all age groups were aggregated); (c) higher in deeper pool habitat; and (d) greater in the autumn and spring in the beaver modified and control sites, respectively.
Habitat modification by beaver can have complex secondary indirect consequences for predator–prey dynamics that should be accounted for in their conservation and management.
{"title":"Quantification of Piscivorous Predator Presence in a Beaver Castor fiber Modified Freshwater Ecosystem","authors":"Robert J. Needham, Paul S. Kemp","doi":"10.1111/fwb.70165","DOIUrl":"https://doi.org/10.1111/fwb.70165","url":null,"abstract":"<div>\u0000 \u0000 <p>\u0000 \u0000 </p><ol>\u0000 \u0000 \u0000 <li>By modifying the physical environment, ecosystem engineers influence a wide variety of ecological processes, affecting other species both directly (e.g., providing sites for reproduction, hibernation, and refuge) and indirectly (e.g., mediating availability of resources by altering food web dynamics). The beaver (Eurasian, <i>Castor fiber</i>, and North American, <i>C. canadensis)</i> provides a textbook example of an ecosystem engineer, restructuring the physical fluvial and riparian environment by constructing dams, bankside burrows, lodges, and canals.</li>\u0000 \u0000 \u0000 <li>The indirect secondary consequences of beaver activity for other species can be difficult to determine. Beaver ponds can benefit fish, such as through the provision of refuge from predators due to increased depth and instream woody structure. Conversely, the formation of deep pools may create habitat for large predatory fish and suitable foraging sites for piscivorous mammalian and avian predators. As a result, the relative costs and benefits for specific life-stages and species can be difficult to disentangle.</li>\u0000 \u0000 \u0000 <li>Focusing predominantly on Grey Heron (<i>Ardea cinerea</i>) and brown trout (<i>Salmo trutta</i>) as the predator–prey model, this study explored how predation pressure differed between four study reaches situated on two co-located streams connected to a common loch in Northern Scotland.</li>\u0000 \u0000 \u0000 <li>One of the two inflowing streams was (i) modified by Eurasian beaver activity. There were also three unmodified (control) reaches comprising: (ii) the second inflowing stream, (iii) a reach above the modified inflowing section, where the influence of dams was deemed to have ceased, and (iv) the stream flowing out of the loch. Trail cameras monitored how predator presence differed spatially (between the control and modified reaches) and temporally (between seasons). Heron abundance differed both spatially and temporally, being: (a) greater at the beaver modified than control sites; (b) positively correlated with 1+ age group trout (but not when all age groups were aggregated); (c) higher in deeper pool habitat; and (d) greater in the autumn and spring in the beaver modified and control sites, respectively.</li>\u0000 \u0000 \u0000 <li>Habitat modification by beaver can have complex secondary indirect consequences for predator–prey dynamics that should be accounted for in their conservation and management.</li>\u0000 </ol>\u0000 \u0000 </div>","PeriodicalId":12365,"journal":{"name":"Freshwater Biology","volume":"71 1","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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