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Endangered Freshwater Ecosystems: Threats and Conservation Needs

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Biodiversity and Functionality of Aquatic Ecosystems".

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 29401

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Special Issue Editors

Dr. Futoshi Nakamura

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Guest Editor

Laboratory of Ecosystem Management, Graduate School of Agriculture, Hokkaido University, Japan
Interests: ecosystem management; stream ecology; fluvial geomorphology

Dr. Junjiro Negishi

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Guest Editor

Graduate School of Environmental Science, Hokkaido University, Japan
Interests: stream ecology; hydrology

Dr. Nobuo Ishiyama

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Guest Editor

Hokkaido research organization
Interests: restoration ecology; connectivity conservation

Special Issue Information

Dear Colleagues,

Freshwater ecosystems represented by river, lake, and wetland provide a variety of habitats for freshwater organisms and a diverse array of ecosystem services, such as flood control, water purification, and recreation. However, freshwater ecosystems are threatened and endangered by human activities, such as dam construction, channelization, pollution, habitat fragmentation, and climate change. Freshwater species numbers have also declined dramatically, with the Living Planet Index of freshwater ecosystems showing an 83% decline since 1970, the worst among terrestrial and marine ecosystems. The aim of the Special Issue is to 1) understand current situations of freshwater ecosystems with reference to natural (e.g., hydrology, geology, and geomorphology) and anthropogenic factors (e.g., land use in a catchment, human modification, and climate change), 2) to present future perspectives to mitigate current decline of species diversity of freshwater organisms, and 3) to develop conservation and restoration measures for recovery of freshwater biodiversity and ecosystem services. We call for articles that quantitatively report the distribution, community structure, and interactions of diverse freshwater taxa such as plants, invertebrates, and fish, as well as their ecological functions in a wide range of geographical regions. Reports on physicochemical properties of freshwater ecosystems such as water quality or hydrological processes are also considered as long as their conclusions are relevant to the purpose of the Special Issue.

Dr. Futoshi Nakamura
Dr. Junjiro Negishi
Dr. Nobuo Ishiyama
Guest Editors

Manuscript Submission Information

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Keywords

Freshwater biodiversity
Freshwater ecosystem service
Human modification
Conservation and restoration
Climate change
Land use change
Habitat fragmentation
Aquatic–terrestrial linkage

Published Papers (9 papers)

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Research

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20 pages, 7445 KiB

Open AccessArticle

Climate Change Impacts on Stream Water Temperatures in a Snowy Cold Region According to Geological Conditions

by Hiroaki Suzuki, Makoto Nakatsugawa and Nobuo Ishiyama

Water 2022, 14(14), 2166; https://doi.org/10.3390/w14142166 - 08 Jul 2022

Cited by 5 | Viewed by 2621

Abstract

This study clarifies how climate change affects stream temperatures in snowy cold regions, where groundwater impacts vary with geological conditions. We developed a physics-based water circulation model that incorporates an atmospheric and land surface process model considering snow processes, a runoff model, and a water temperature estimation model. Small watersheds in the mountainous area of Hokkaido formed the study area, and the runoff model was assigned different parameters depending on the geological characteristics. Using these parameters, changes in water temperature were calculated with respect to changes in the meteorological data in historical and future simulations. Current water temperatures were effectively reproduced by the model, and following the IPCC RCP 8.5 scenario, future water temperatures in the distribution area for new pyroclastic flows were predicted to remain lower in summer than in the distribution area of older formations. The findings of this study will be useful in informing conservation measures for river ecosystems, including the prioritization of streams where cold-water fish need to be conserved. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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14 pages, 3659 KiB

Open AccessArticle

Distribution, Drivers, and Threats of Aluminum in Groundwater in Nova Scotia, Canada

by Kristin A. Hart, Gavin W. Kennedy and Shannon M. Sterling

Water 2021, 13(11), 1578; https://doi.org/10.3390/w13111578 - 02 Jun 2021

Cited by 5 | Viewed by 3629

Abstract

Increased rates of acid deposition derived from the burning of fossil fuels over the last century have resulted in the acidification and increase in aluminum (Al) levels in freshwaters and soils in sensitive areas. While the acidification of surface waters such as lakes and rivers has been extensively studied, the acidification status and resulting Al concentrations in groundwater are poorly understood. Here we aim to describe the distribution of Al in groundwater across the province of Nova Scotia, Canada. We investigate the hydrogeological conditions that influence Al concentrations in groundwater and compare Al concentrations to legislated threshold levels for human and aquatic health. We found groundwater Al concentrations to be highest in areas underlain by plutonic and metamorphic bedrock types as well as surficial aquifers, with pH and organic carbon concentrations having the strongest correlation with groundwater Al concentrations. Few samples exceed the maximum acceptable concentration of 2900 µg/L released by Health Canada (2021), but these exceedances are important to highlight given the challenges with respect to Al treatment in private domestic wells and our evolving understanding of Al impacts to human health. High concentrations of Al in groundwater may also be exported to surface waters such as rivers and lakes, where they can be harmful to aquatic populations such as Atlantic salmon (Salmo salar). We recommend that private well owners test their water supplies for Al, and that further studies on Al export from groundwater to surface water be carried out in the most high-risk areas coincident with important Atlantic salmon river watersheds. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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15 pages, 950 KiB

Open AccessFeature PaperArticle

Additive Effects of Sediment and Nutrient on Leaf Litter Decomposition and Macroinvertebrates in Hyporheic Zone

by Md. Khorshed Alam, Junjiro N. Negishi, Pongpet Pongsivapai, Shohei Yamashita and Tomohiro Nakagawa

Water 2021, 13(10), 1340; https://doi.org/10.3390/w13101340 - 12 May 2021

Cited by 6 | Viewed by 3455

Abstract

Despite the fact that leaf decomposition constitutes an important function in rivers, how multiple environmental stressors simultaneously affect it remains largely unknown. This study investigated the interactive effects of fine sediments (particle size: <2 mm; experimentally manipulated) and a specific nutrient (i.e., nitrate) on subsurface (hyporheic) leaf litter decomposition rate and macroinvertebrates in a gravel-bed river and its tributary in eastern Hokkaido, Japan. The experiment was conducted by measuring leaf litter decomposition of dried Alnus japonica leaves (3 ± 0.05 g) in benthic and hyporheic zones with and without sediment treatments at four sites that had a gradient of nitrate concentration. The decomposition rate was comparable between the two zones but was slowed down by sediment addition in the hyporheic zone. The functional responses were highly predictable for the individual stressors. Detritivore invertebrates were the main driving component of decomposition in the decreased leaf litter decomposition rate under a higher fine sediment condition, whereas higher nitrate accelerated the leaf litter decomposition rate by stimulated microbe-driven decomposition as well as detritivore feeding. Overall, the negative effect of fine sediment could be offset in the presence of nitrate while considering gross functional responses. We demonstrated the additive effects of fine sediment and nitrate on leaf litter decomposition in the hyporheic zone. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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11 pages, 1442 KiB

Open AccessArticle

The Relative Effects of Biotic and Abiotic Factors on the Recruitment of Freshwater Mussels (Margaritifera laevis)

by Keita Kawajiri, Nobuo Ishiyama, Kazuki Miura, Akira Terui, Masanao Sueyoshi and Futoshi Nakamura

Water 2021, 13(9), 1289; https://doi.org/10.3390/w13091289 - 03 May 2021

Cited by 3 | Viewed by 3293

Abstract

Freshwater mussels, Unionoida, are endangered across the globe due to recruitment failure. In the present study, with general linear mixed models, we investigated the relative effects of biotic (host fish density) and abiotic (water depth, fine sediment, water temperature, and water quality) factors on the recruitment of Margaritifera laevis in 10 streams of Hokkaido, northern Japan. We additionally examined the factors regulating the density of the host fish Oncorhynchus masou masou with general linear models. The proportion of juvenile mussels had a unimodal relationship with the host density, which was the most influential factor among the others examined. The positive relationship between mussel recruitment and host density can be attributed to an increased host fish infection rate. The negative correlation between mussel recruitment and host density at high fish densities may be due to reduced larval growth on host fish that are in poor physical condition. We also found that host fish density was negatively affected by nutrient enrichment. Our results suggest that mitigating water quality degradation to recover host fish density should be prioritized to improve mussel recruitment. Although stock enhancement is effective for increasing the salmon population density, excess stocking can further disturb mussel recruitment. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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11 pages, 1272 KiB

Open AccessFeature PaperArticle

Combined Effects of Summer Water Temperature and Current Velocity on the Distribution of a Cold-Water-Adapted Sculpin (Cottus nozawae)

by Kaiji Suzuki, Nobuo Ishiyama, Itsuro Koizumi and Futoshi Nakamura

Water 2021, 13(7), 975; https://doi.org/10.3390/w13070975 - 01 Apr 2021

Cited by 4 | Viewed by 2519

Abstract

Clarifying the combined effects of water temperature and other environmental factors on the species distributions of cold-water fishes is the first step toward obtaining a better understanding of the complex impacts of climate warming on these species. In the present study, we examined the abundance and occurrence of the fluvial sculpin, Cottus nozawae, in response to water temperature along environmental gradients in northern Japan. The abundance survey was conducted in the Sorachi River catchment with two-pass electrofishing with a backpack electrofisher. For the occurrence survey, we carried out one-pass electrofishing in the Sorachi, Chitose, and Tokachi River catchments. Fish sampling was conducted once from July to August 2018 in the Sorachi River catchment, from May to June 2011 in the Chitose River catchment, and from July to September 2012 in the Tokachi River catchment. Generalized linear mixed models (GLMMs) and generalized linear models (GLMs) were used for the abundance and occurrence analyses, respectively. We found that the mean summer water temperature was the most influential factor on the distribution of C. nozawae; the abundance and occurrence were both negatively affected by increased water temperatures. In the occurrence model, occurrence probabilities of 0.9 and 0.5 for C. nozawae corresponded to mean summer temperatures of 12.0 and 16.1 °C, respectively. Furthermore, we identified a combined effect of water temperature and current velocity on the abundance of C. nozawae. The increased mean summer water temperature had a stronger negative effect on C. nozawae abundance under gentle flow conditions. While the precise mechanisms of this combined effect could not be determined in this study, stressors associated with low current velocities may increase their vulnerability to higher water temperatures. Our findings indicate that flow disturbances caused by human activities such as excessive water abstraction may exacerbate the negative impacts of climate warming on populations of C. nozawae in the future. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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21 pages, 3294 KiB

Open AccessFeature PaperArticle

Morphometry-Driven Divergence in Decadal Changes of Sediment Property in Floodplain Water Bodies

by Pongpet Pongsivapai, Junjiro N. Negishi, Hokuto Izumi, Paolo A. Garrido and Kanta Kuramochi

Water 2021, 13(4), 469; https://doi.org/10.3390/w13040469 - 11 Feb 2021

Cited by 3 | Viewed by 2369

Abstract

Sediments are potentially the internal source that supply nutrients to water in lentic to semi-lentic ecosystems. The understanding of factors that cause temporal changes in sediment properties is critical for the internal source management. This study investigated the spatial variations and temporal changes in sediment properties in relation to their controlling factors in water bodies of the Ishikari River, Northern Japan. Sediment data in 29 water bodies were measured twice (around 2005 and 2019) to study the temporal changes in sediment properties, and were compared using Generalized Linear Mixed Models (GLMMs). The controlling factors of sediment properties including catchment and morphometry were examined by partial least square (PLS) regression. Our results showed that the temporal change in sediment properties over decades was largely driven by morphometry, while land use in the catchment played a relatively minor role in those changes. The rate of change in organic matter (OM) differed among water bodies depending on their morphometry. The small and shallow water bodies provided suitable habitat for macrophytes that led to OM deposits, resulting to an increase in OM and OM to total nitrogen (TN) ratio over time. The consequences of these changes are important for internal source management and biodiversity conservation. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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20 pages, 5152 KiB

Open AccessEditor’s ChoiceArticle

Time Series Changes in Fish Assemblages and Habitat Structures Caused by Partial Check Dam Removal

by Shigeya Nagayama, Nobuo Ishiyama, Taro Seno, Hideyuki Kawai, Yoichi Kawaguchi, Daisuke Nakano and Futoshi Nakamura

Water 2020, 12(12), 3357; https://doi.org/10.3390/w12123357 - 30 Nov 2020

Cited by 5 | Viewed by 2357

Abstract

Despite a steep increase in dam removal projects, there are few studies on the biophysical responses to dam removal. In this study, we evaluated the short-term (1.5 years) and long-term (5.5 years) effects of partial check dam removal on fish assemblages and their habitats. First, the habitat preferences of fish were examined at a channel unit scale: pools, rapids, and side channels satisfied the seasonal habitat requirements of the fish assemblages. Partial check dam removal increased the abundance of these habitats and diversified the habitat structures owing to the sediment release from the dam; in contrast, the bedrock distinctly decreased 1.5 years after dam removal. However, 5.5 years after dam removal, the bedrock proportion increased, and the habitat structures were simplified again owing to the re-transportation of sediments. Similar temporal changes were also determined through a reach-scale analysis with a change in the bed materials. Anadromous Oncorhynchus masou began to spawn and recolonize in the upstream section of the dam after the dam removal, causing similar assemblage compositions between the downstream and upstream sections. The abundance of Salvelinus malma and Noemacheilus barbatulus toni in the upstream reaches decreased over time after the dam removal. The temporal changes in the biophysical responses suggest that long-term monitoring is indispensable for the reliable evaluation of dam removal effects. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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12 pages, 1819 KiB

Open AccessEditor’s ChoiceCommunication

Genetic Structure and Population Demography of White-Spotted Charr in the Upstream Watershed of a Large Dam

by Souta Nakajima, Shun K. Hirota, Ayumi Matsuo, Yoshihisa Suyama and Futoshi Nakamura

Water 2020, 12(9), 2406; https://doi.org/10.3390/w12092406 - 27 Aug 2020

Cited by 4 | Viewed by 3643

Abstract

White-spotted charr (Salvelinus leucomaenis leucomaenis) is an anadromous fish that has been severely harmed by human land-use development, particularly through habitat fragmentation. However, the anthropogenic impacts on populations of this species have not been evaluated, except those on small dammed-off populations. Using multiplexed ISSR genotyping by sequencing, we investigated the genetic structure of white-spotted charr in four tributaries in the upper section of the Kanayama Dam in the Sorachi River, Hokkaido Island, Japan. There were no distinct genetic structures (F_ST = 0.014), probably because some active individuals migrate frequently among tributaries. By model-flexible demographic simulation, historical changes in the effective population size were inferred. The result indicates that the population size has decreased since the end of the last glacial period, with three major population decline events, including recent declines that were probably associated with recent human activities. Nevertheless, populations in the watershed upstream of the Kanayama Dam are still expected to be at low risk of immediate extinction, owing to the large watershed size and the limited number of small check dams. An effective conservation measure for sustaining the white-spotted charr population is to maintain high connectivity between tributaries, such as by providing fishways in check dams during construction. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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Review

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21 pages, 2683 KiB

Open AccessReview

Not All Rivers Are Created Equal: The Importance of Spring-Fed Rivers under a Changing Climate

by Robert A. Lusardi, Andrew L. Nichols, Ann D. Willis, Carson A. Jeffres, A. Haven Kiers, Erwin E. Van Nieuwenhuyse and Randy A. Dahlgren

Water 2021, 13(12), 1652; https://doi.org/10.3390/w13121652 - 12 Jun 2021

Cited by 11 | Viewed by 3955

Abstract

In the Western United States, volcanic spring-fed rivers are anticipated to become increasingly more important for salmonids and other native fishes, as these rivers will retain coldwater habitats as the climate warms. Despite this, little is known about the hydro-biogeochemical interactions within these ecosystems. A review of existing literature on spring-fed rivers, coupled with a decade of research on volcanic spring-fed rivers of northern California, finds that these systems are exceptionally productive and exhibit stable environmental conditions. These unique conditions stem from hydrogeologic processes typical of young volcanic terrains. Aquatic macrophytes, common to some nutrient-rich spring-fed systems, play a disproportionate role in hydrologic and geomorphic processes by facilitating ecological interactions and velocity conditions that improve juvenile salmonid growth. We find that volcanic spring-fed rivers are also resilient to climate change, due not only to their ability to dampen water temperature changes through deep groundwater flow but also because of their nutrient-driven high ecosystem productivity, which may enable coldwater species to metabolically compensate for marginal increases in water temperature. Understanding the fundamental geomorphic and ecological differences between these rare ecosystems and their numerically dominant runoff rivers is essential for developing long-term conservation strategies for coldwater species under a rapidly changing climate. Full article

(This article belongs to the Special Issue Endangered Freshwater Ecosystems: Threats and Conservation Needs)

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