Biodiversity and Conservation of Freshwater Ecosystems

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 (28 February 2023) | Viewed by 10376

Special Issue Editor


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Guest Editor
Faculty of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an, China
Interests: freshwater biodiversity; biogeography; macroecology; macroinvertebrates; fishes; invasion biology

Special Issue Information

Dear Colleagues,

Fresh waters are among the most diverse and dynamic ecosystems on the Earth, supporting a considerably higher proportion (almost 6%) of global biodiversity than  its area (< 1%) might suggest. However, due to increasing amounts of human-mediated disturbances, freshwater ecosystems have been and are experiencing more serious degradation than terrestrial and marine ecosystems.  This underscores the importance of maintaining and conserving freshwater biodiversity, which must be based on comprehensive understanding (e.g., from the perspectives of multifaceted biodiversity) of the root causes of biodiversity loss and underlying ecological dynamics. Simultaneously examining the effects of anthropogenic disturbances on taxonomic, functional, and phylogenetic diversity can significantly enhance the understanding of causes of ecosystem degradation and provide useful implications for biodiversity conservation and management.

Dr. Xiaoming Jiang
Guest Editor

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Keywords

  • human impacts
  • freshwater organisms
  • traits
  • ecosystem functioning
  • biodiversity assessment

Published Papers (5 papers)

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Research

16 pages, 1903 KiB  
Article
Analysis of Water Quality and Habitat Suitability for Benthic Macro-Invertebrates in the Majiagou Urban River, China
by Yongxin Zhang, Hongxian Yu, Manhong Liu, Jiamin Liu, Wentao Dong, Tiantian Xu, Yunrui Wang and Yao Guo
Water 2023, 15(12), 2269; https://doi.org/10.3390/w15122269 - 17 Jun 2023
Cited by 3 | Viewed by 2083
Abstract
The macro-invertebrate is an important part of the aquatic food web of urban rivers, and it is of great significance in understanding its ecological suitability for the stability of river ecosystems. Previous studies, such as those that have conducted suitability index and canonical [...] Read more.
The macro-invertebrate is an important part of the aquatic food web of urban rivers, and it is of great significance in understanding its ecological suitability for the stability of river ecosystems. Previous studies, such as those that have conducted suitability index and canonical correspondence analyses (CCAs), have widely used a macro-invertebrate suitability analysis; however, these studies can only confirm a few coupling relationships between the environment and macro-invertebrates. In our study, one-way ANOVA, HCA, PCA and GAM models were used to explain the differences in the spatial and temporal distribution of environmental factors, as well as to reduce data redundancy. A response curve of the critical environmental factors and macro-invertebrates was constructed, and the nonlinear relationship between these factors and benthic animals was quantified to analyze the ecological threshold of the macro-invertebrates. The study area was the Majiagou River, Harbin, China. The results show that COD had significant seasonal differences due to complex hydrological conditions, and most of the water quality factors had spatial differences. The GAM model explained 60% of the Margalef diversity index (MDI) variance. The relationship between chlorophyll-a and MDI was unimodal, and MDI and NH4+-N essentially showed a negative correlation; when the total nitrogen (TN) value reached 5.8 mg/L, MDI reached its peak. When MDI was higher than the mean value, the chlorophyll-a range was 18.1 μg/L~83 μg/L. The NH4+-N was less than 1.8 mg/L, and TN was 1.8~6.8 mg/L. This study provides a reference for the comprehensive management of urban river ecosystems. Full article
(This article belongs to the Special Issue Biodiversity and Conservation of Freshwater Ecosystems)
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11 pages, 2169 KiB  
Article
Is It Feasible to Preserve a Self-Sustaining Population of Yangtze Finless Porpoise in the Highest Density Section of Yangtze River?
by Weiping Wang, Chongrui Wang, Jinxiang Yu and Bin Wu
Water 2023, 15(6), 1215; https://doi.org/10.3390/w15061215 - 20 Mar 2023
Viewed by 1724
Abstract
Using the VORTEX v. 10. 5.0.0, population viability analysis (PVA) was performed for Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis) in the highest density section between Hukou and Meilong section (HMS) of the Yangtze River. Baseline model showed that this population was in [...] Read more.
Using the VORTEX v. 10. 5.0.0, population viability analysis (PVA) was performed for Yangtze finless porpoise (YFP, Neophocaena asiaeorientalis) in the highest density section between Hukou and Meilong section (HMS) of the Yangtze River. Baseline model showed that this population was in a relatively vulnerability state; the deterministic growth rate (Det-r) was −0.0230; the stochastic growth rate (Stoch-r) was −0.0385; the probability of extinction (PE) was 0.5690; the mean population size of extant populations (N-extant) was 22; the genetic diversity (GD) was 0.7698. Under the general protection model, the Det-r was 0.0015, and the Stoch-r was −0.0092; Under the medium protection model, the Det-r was 0.0219, and the Stoch-r was 0.0144; Under the optimal protection model, the Det-r was 0.0383, and the Stoch-r was 0.0357. Sensitivity analysis found that adult females breeding rate, sex ratio at birth, and mortality rate of juvenile YFP were sensitive to maintaining population stability. The PVA showed that the conservation of YFP population in HMS depends on: neutralization of all threats affecting YFP population in the HMS; maintenance and, whenever possible, enhancement of the functional connectivity of the waterbody, increasing the food resources of YFP and reducing the risk of injury to YFP caused by human. Full article
(This article belongs to the Special Issue Biodiversity and Conservation of Freshwater Ecosystems)
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16 pages, 4162 KiB  
Article
Evaluation of a Nature-like Bypass for Non-Salmonids in the Sesan River
by Junjian Sun, Fuqiang Yu, Qi Zhang, Shujing Luo, Wu Zhou, Hui Zhang, Junjun Tan, Xiaotao Shi, Yinting Shen and Jiayue Shi
Water 2023, 15(3), 421; https://doi.org/10.3390/w15030421 - 19 Jan 2023
Cited by 1 | Viewed by 1878
Abstract
In recent years, the hydropower development of the lower Mekong River has accelerated, accompanied by habitat loss and fragmentation. We conducted two experiments using video recordings and traps to evaluate the effectiveness of a nature-like rock ramp bypass in the Sesan River in [...] Read more.
In recent years, the hydropower development of the lower Mekong River has accelerated, accompanied by habitat loss and fragmentation. We conducted two experiments using video recordings and traps to evaluate the effectiveness of a nature-like rock ramp bypass in the Sesan River in 2019 and 2021. The results show that the fishway provides both upstream and downstream passage for at least 24 non-salmonid species of fish. The vast majority of fish choose to ascend from July to September, especially in August, and hardly between October and November. The fish inside the fishway prefer to move during the daytime (6:00–18:00), especially during August and September. An excessive water depth at the entrance can lower the number of ascending fish, whereas a higher water depth at the exit can cause the opposite result. Nevertheless, the size of fish monitored exhibits a decreasing trend, suggesting the nature-like bypass cannot completely mitigate the impact caused by this impassable Sesan Ⅱ dam. Therefore, a quantitative assessment of the bypass is highly encouraged, whereas the selection of the tracked fish species and experimental period requires considerable deliberation. This study alleviates the dilemma of insufficient fishway evaluation in tropical countries, which can provide researchers with data support on future non-salmonid fishway designs. Full article
(This article belongs to the Special Issue Biodiversity and Conservation of Freshwater Ecosystems)
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15 pages, 8556 KiB  
Article
Application of Tesla Valve’s Obstruction Characteristics to Reverse Fluid in Fish Migration
by Guorui Zeng, Maosen Xu, Jiegang Mou, Chenchen Hua and Chuanhao Fan
Water 2023, 15(1), 40; https://doi.org/10.3390/w15010040 - 22 Dec 2022
Cited by 3 | Viewed by 2274
Abstract
More and more activities have caused significant damage to the river environment, among which a typical problem of blocked fish migration is constantly attracting people’s attention. Nowadays, fishways are essential hydraulic facilities to solve such problems. Although a different fishway has a particular [...] Read more.
More and more activities have caused significant damage to the river environment, among which a typical problem of blocked fish migration is constantly attracting people’s attention. Nowadays, fishways are essential hydraulic facilities to solve such problems. Although a different fishway has a particular blocking effect on the water flow, the flow velocity of the vital positions of fish migration in the fishway could still be relatively high locally, which may pose a certain challenge to the fish migration (the higher flow velocity could lead to the increase in migratory energy consumption of fish). Therefore, further exploration of fish passing facilities may be required. As a check valve without movable parts, the Tesla valve is expected to be used in fish passing facilities because of its substantial obstruction to the reverse flow of internal fluid. This paper conducted numerical simulation experiments on the fish passage pipeline designed based on Tesla valves using the RNG (renormalization group) k-ε model. Grass carp were selected as the primary analysis object, and the simulation results were analyzed from the perspective of turbulence characteristics. The results showed that the fish passage pipeline based on the T45-R Tesla valve was better than that on the GMF (Gamboa, Morris and Forster) Tesla valve in velocity control. The velocity at the vital position of T45-R internal fluid was about 20% lower than that of GMF. The results of the velocity cloud diagram showed apparent high-velocity and low-velocity areas in the fish passage pipeline designed based on the T45-R Tesla valve. The high-velocity area was the vital position for fish upstream, and the maximum velocity variation range in this area was 0.904~1.478 m/s. At the same time, the flow in the low-velocity area is almost static water. The analysis illustrated that the resulting velocity environment could provide conditions for grass carp to move upstream successfully. The results of turbulent kinetic energy inside the fish passage pipeline showed that the maximum value of turbulent kinetic energy was only about 0.043 m2/s2, which could be friendly for fish upstream. In addition, the results show that pressure-related problems could not seem to have an excessive impact on fish migration, such as causing damage. Overall, the results further studied the feasibility of using the Tesla valve as a fish passage pipeline. Full article
(This article belongs to the Special Issue Biodiversity and Conservation of Freshwater Ecosystems)
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13 pages, 4641 KiB  
Article
COVID-19 Lockdowns Promoted Recovery of the Yangtze River’s Aquatic Ecosystem
by Dongdong Fang, Haile Yang, Hui Zhang, Hao Du, Junlin Yang and Qiwei Wei
Water 2022, 14(22), 3622; https://doi.org/10.3390/w14223622 - 10 Nov 2022
Cited by 2 | Viewed by 1777
Abstract
The impacts of COVID-19 lockdowns on human life, air quality, and river water quality around the world have received significant attention. In comparison, assessments of the implications for freshwater ecosystems are relatively rare. This study explored the impact of COVID-19 lockdowns on aquatic [...] Read more.
The impacts of COVID-19 lockdowns on human life, air quality, and river water quality around the world have received significant attention. In comparison, assessments of the implications for freshwater ecosystems are relatively rare. This study explored the impact of COVID-19 lockdowns on aquatic ecosystems in the Yangtze River by comparing river water quality, phytoplankton, zooplankton, and fish data collected at the site in the middle reach of the Yangtze River in 2018 and 2020. The results show that during COVID-19 lockdowns, the reduction in industrial and domestic effluent discharge led to a reduction in organic pollution and industrial plant nutrient pollution in rivers. Among them, PO43−−P, CODMn, and TP were significantly decreased (p < 0.05). During lockdowns, nutrient supplies such as TN and TP were reduced, which led to inhibition of algae growth and decreased phytoplankton abundance. Phytoplankton affects the abundance of zooplankton through a bottom-up effect, and a decrease in phytoplankton density leads to a decrease in zooplankton density. The decrease in plankton density led to lower primary productivity in rivers, reduced fish feed supplies, intensified competition among fish populations, with increases in population dominated by high trophic level carnivorous fish. In addition, the decrease in fishing intensity has contributed to an increase in the number of rivers–sea migratory fish; the fish community was earlier mainly dominated by small-sized species with a short life cycle, and the number of supplementary populations has now increased. As a consequence, the fish community structure shows a tendency toward high complexity and high fish diversity. Overall, these observations demonstrate that the rapid revival of the retrogressive Yangtze River ecosystem is possible through limitation of anthropic interferences. Full article
(This article belongs to the Special Issue Biodiversity and Conservation of Freshwater Ecosystems)
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