Research

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22 pages, 11317 KiB

Open AccessArticle

Numerical Study of the Riverine Microplastic Distribution in the Arctic Ocean

by Elena Golubeva and Marina Gradova

Water 2024, 16(3), 441; https://doi.org/10.3390/w16030441 - 29 Jan 2024

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Marine plastic pollution is currently one of the most serious environmental threats. In this study, based on scenario calculations for a five-year period, we analyzed the possible spread of microplastics carried by Siberian rivers to the Kara Sea shelf. The Lagrangian particle model [...] Read more.

Marine plastic pollution is currently one of the most serious environmental threats. In this study, based on scenario calculations for a five-year period, we analyzed the possible spread of microplastics carried by Siberian rivers to the Kara Sea shelf. The Lagrangian particle model used daily data from 3D numerical modeling to simulate microplastic transport by ocean currents and sea ice drift. The results of a series of scenario calculations show how the distribution of particles and their subsequent deposition depend on their type (density), size, processes of freezing into the ice, and biofouling (accumulation of microorganisms). The crucial influence of the effects of microplastic embedding in sea ice and particle biofouling on the trajectories of floating particles and their deposition on the seafloor is highlighted. The transport of light particles of microplastics from Siberian rivers by ice can contribute to the pollution of the Barents Sea, in addition to their more active outflow through the Fram Strait. Biofouling is a driver of microplastic deposition on the shelf bottom or transport along the continental slope in a cyclonic direction following the trajectory of the Atlantic waters. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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19 pages, 10760 KiB

Open AccessArticle

Variation of Local Wind Fields under the Background of Climate Change and Its Impact on Algal Blooms in Lake Taihu, China

by Yachun Li, Shihua Zhu, Xin Hang, Liangxiao Sun, Xinyi Li, Xiaochun Luo and Xiuzhen Han

Water 2023, 15(24), 4258; https://doi.org/10.3390/w15244258 - 12 Dec 2023

Viewed by 966

Abstract

Global climate change can greatly promote the continuing expansion of algal blooms in eutrophic inland lakes. Wind fields, an important climate factor, provide an external driving force for the movement of algal blooms. Based on algal bloom satellite imageries and wind observation data [...] Read more.

Global climate change can greatly promote the continuing expansion of algal blooms in eutrophic inland lakes. Wind fields, an important climate factor, provide an external driving force for the movement of algal blooms. Based on algal bloom satellite imageries and wind observation data from 2003 to 2022, this study explored a quantitative assessment of the variations in surface wind fields and their impacts on the algal blooms in Lake Taihu, China. The results indicate that the mean wind speed at different time scales in the Lake Taihu area presents a continuous descending tendency in recent decades, which is the probable cause for the increasing frequency and severity of algal blooms in the lake. Wind fields affect the formation, location, and severity of algal blooms in diverse and complex ways. The area and frequency of algal blooms in Lake Taihu increase with the decrease in wind speed. The 6 h mean wind speed before 12:00 LT (Local Time) on the day of the algal bloom occurrence generally follows a Gaussian distribution, with a wind speed range of (0.6 m/s, 3.4 m/s) at the 95.5% confidence level. Accordingly, the wind speeds of 0.6 m/s and 3.4 m/s are identified to be the lower and upper critical wind speed indicators suitable for the formation of algal blooms, respectively. Another meaningful finding is that the outbreak of large-scale algal blooms requires stricter wind speed conditions, with a significantly lower wind speed threshold of around 2 m/s. Our study also demonstrates that the dominant wind direction of southeast in the region may be an important cause of the continuous water-quality decline and the high frequency and severity of algal blooms in the northwest waters of the lake. These findings will contribute to further studies on the dynamic mechanism of algal blooms and provide support for water environment management and algal bloom prevention and control. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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16 pages, 3696 KiB

Open AccessArticle

Impact of Phytoplankton Community Structure Changes in the South Sea of Korea on Marine Ecosystems Due to Climate Change

by Kyung-Woo Park, Mi-Hee Chung, Man-Ho Yoo, Kwang-Seok O, Kyoung-Yeon Kim, Tae-Gyu Park and Seok-Hyun Youn

Water 2023, 15(23), 4043; https://doi.org/10.3390/w15234043 - 22 Nov 2023

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Abstract

Herein, we conducted surveys during the 2018–2022 summers to investigate the impact of climate change-related changes in the phytoplankton community structure on the marine ecosystem in the South Sea of Korea. The average surface water temperature increased by ~1.07 °C at 0.0195 °C·yr [...] Read more.

Herein, we conducted surveys during the 2018–2022 summers to investigate the impact of climate change-related changes in the phytoplankton community structure on the marine ecosystem in the South Sea of Korea. The average surface water temperature increased by ~1.07 °C at 0.0195 °C·yr⁻¹ between 1968 and 2022. During the summers, the rate was 0.0211 °C·yr⁻¹, with a total increase of ~1.16 °C, indicating a stronger increase in summer surface water temperature. Over the last 30 years, nutrient levels in the South Sea have decreased, particularly at the surface. Moreover, 29.3–90.0% of the phytoplankton community structure was dominated by nanoflagellates (≤20 μm). Based on the size of the phytoplankton chl-a, the average contribution rate of picophytoplankton was the highest (60.1%). Redundancy analysis revealed negative correlations between nutrients and water depth, excluding NH₄. Increased stratification due to climate change is causing reduced nutrient availability at the surface mixed layer, and the size of the phytoplankton structure is progressively reducing. These changes are expected to manifest in a complex microbial food web centered on smaller phytoplankton with low primary productivity. This can reduce the efficiency of carbon transfer to higher consumer levels, suggesting a potential decrease in marine productivity. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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16 pages, 3471 KiB

Open AccessArticle

Untangling Humpback Whale-Watching Management Networks: Collaboration and Conflict in the Northeast Pacific

by Alfonso Langle-Flores, Zinthia López-Vázquez, Rosa María Chávez Dagostino and Adriana Aguilar-Rodríguez

Water 2023, 15(22), 3975; https://doi.org/10.3390/w15223975 - 16 Nov 2023

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Abstract

Humpback whales face emerging anthropogenic challenges such as entanglement in abandoned fishing gear and stranding during their winter migration. Such challenges require collective action solutions involving diverse stakeholders across jurisdictions, social sectors, and geographies. Collaborative governance systems involve conflictual and collaborative interactions. We [...] Read more.

Humpback whales face emerging anthropogenic challenges such as entanglement in abandoned fishing gear and stranding during their winter migration. Such challenges require collective action solutions involving diverse stakeholders across jurisdictions, social sectors, and geographies. Collaborative governance systems involve conflictual and collaborative interactions. We used a quantitative approach (social network analysis) to map the structure of three social networks: Collaboration in disentanglement, collaboration in stranding, and conflict. We administered a face-to-face survey to 38 stakeholders from four social sectors across seven coastal localities from April to November 2021. We also obtained perspectives from the same stakeholders about pressing conflicts, rule compliance, and law enforcement regarding whale-watching management in the region using a semi-structured questionnaire. We found hints of different dimensions of collaboration occurring simultaneously: Coordination, cooperation, and conflict. Networks played distinct roles in promoting collaboration across sectors, and while the disentanglement network coordinated civil society and the public sector, the stranding network facilitated cooperation within the public sector. The most pressing social conflicts detected by stakeholders were pleasure boats, abandoned fishing gear, and poor rule compliance regarding the distance between boats and whales. Our results suggest that in the context of institutional weakness, collaborative social networks play a crucial role in the management and conservation of coastal and marine common-pool resources. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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0 pages, 1517 KiB

Open AccessArticle

Distribution Characteristics of Carbon, Nitrogen, and Phosphorus and Pollution Load Estimation of Sediments in Danjiangkou Reservoir, China

by Xiong Pan, Junqi Cao, Li Lin, Ziwei Yang, Lei Dong, Jingxiang Tao, Quanhong Li, Yuqiang Liu, Chengyu Zhang and Xuanmin Huang

Water 2023, 15(16), 2885; https://doi.org/10.3390/w15162885 - 10 Aug 2023

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Abstract

Danjiangkou Reservoir is a world-famous large artificial freshwater lake that offers water resources for the middle route of the South-to-North Water Diversion Project in China. In this study, the distribution of carbon, nitrogen, and phosphorus in reservoir sediments and their pollution assessments were [...] Read more.

Danjiangkou Reservoir is a world-famous large artificial freshwater lake that offers water resources for the middle route of the South-to-North Water Diversion Project in China. In this study, the distribution of carbon, nitrogen, and phosphorus in reservoir sediments and their pollution assessments were elucidated at different water periods. The average TN (total nitrogen), TP (total phosphorus), and TOM (total organic matter) contents were 794.8 mg/kg, 807.2 mg/kg, and 8.7% in the nonflood season, respectively. When the time comes to flood season, with the large amount of nitrogen pollution inputted from peripheral nonpoint sources and phosphorus released by the accelerated exchange of water bodies, the average TN concentration increased to 1061.2 mg/kg. In addition, the average TP and TOM contents were reduced to 559.5 mg/kg and 6.3%. Nutrient pollution fluctuated between the safe and lowest level. Reservoir eutrophication risk was low. There was a certain nitrogen enrichment in the Danjiangkou Reservoir, and the flood season was the main period of nitrogen pollution input. Water exchange during flood season might accelerate organic matter degradation. Near the dam, sediment organic matter content increased significantly, reaching severe pollution levels. The results of the simulated sediment nutrient release test showed that the nitrogen and phosphorus in the reservoir would release slowly. Moreover, their annual release flux was calculated as 470.4 t and 87.9 t, respectively. It illustrated that the internal pollution of Danjiangkou Reservoir was light, and the release amount was small, so it was not the main pollution source of the reservoir at present. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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13 pages, 2448 KiB

Open AccessArticle

Numerical Modelling of a Dam-Regulated River Network for Balancing Water Supply and Ecological Flow Downstream

by Yuxuan Gao, Wei Xiong and Chenhao Wang

Water 2023, 15(10), 1962; https://doi.org/10.3390/w15101962 - 22 May 2023

Cited by 2 | Viewed by 1103

Abstract

Dam operation is regarded as an effective way to increase water, food, and energy security for society. However, with the increasing water demand and frequent extreme droughts, numerous rivers worldwide go through periods of water scarcity and water ecosystem deterioration to varying degrees. [...] Read more.

Dam operation is regarded as an effective way to increase water, food, and energy security for society. However, with the increasing water demand and frequent extreme droughts, numerous rivers worldwide go through periods of water scarcity and water ecosystem deterioration to varying degrees. Balancing the water supply and ecological flow of the dam-regulated river network is essential in the context of river restoration. In this study, we proposed a hydrodynamic and water quality model of a dam-regulated river network balancing water supply and ecological flow using the Environmental Fluid Dynamics Code (EFDC). A section of Jinjiang watershed located in the southwestern of China was chosen as the study area. Firstly, the model was calibrated and validated. By comparing the simulated values with the measured values, the statistical analysis results showed that the relative root mean-squared error (RRMSE) values of water level, COD and NH₃-N were 5.5–8.1%, 23.6% and 28.4%, respectively, indicating an adequate degree of agreement between simulation and observation. Based on the established model, dam operation schemes under a dry hydrologic scenario and emergency contamination scenario were formulated to ensure the requirement of ecological water flow and water quality simultaneously. For the dry hydrologic scenario, the ecological water requirement could be satisfied through the dam operation. However, in an emergency contamination scenario, regional water quality requirements cannot be met through dam operation. The dam operation only plays a role in controlling the scope of pollution. This study is expected to provide scientific support for dam-regulated river network management and downstream river ecosystem protection. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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17 pages, 2680 KiB

Open AccessArticle

Risk Assessment of Dissolved Trace Elements and Heavy Metals in the Upper Reaches of the Yangtze River, China

by Yuanyuan Chen, Fei Xiong, Dongdong Zhai, Hongyan Liu, Xinbin Duan, Daqing Chen, Wei Jiang and Bo Li

Water 2023, 15(7), 1330; https://doi.org/10.3390/w15071330 - 28 Mar 2023

Cited by 1 | Viewed by 1442

Abstract

The Yangtze River Basin, one of China’s five major watersheds and a primary source of drinking water for the country, is experiencing serious environmental pollution as heavy metals are discharged into its rivers. To evaluate the water quality of the river, determined water [...] Read more.

The Yangtze River Basin, one of China’s five major watersheds and a primary source of drinking water for the country, is experiencing serious environmental pollution as heavy metals are discharged into its rivers. To evaluate the water quality of the river, determined water quality parameters were compared with the maximum permissible limit values recommended by the World Health Organization and Chinese drinking water standards. Physical and chemical analyses were conducted on water samples taken from 19 locations along the river’s path. The study quantified the contents of sodium (Na), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), scandium (Sc) and mercury (Hg). The results show that the average values of Mg, Sr, Co, Cu, Fe, Mn and Sc are higher than the historical background values. Moreover, through a correlation analysis it was concluded that these nutrients and trace metals have high values due to anthropogenic pollution in the study area. The computed WQI values range between 9.59 and 20.26, indicating excellent water quality in the river basin. Finally, hazard quotient (HQ) values show that exposure to the detected pollutants will have no adverse effects on human health and does not pose a potential non-carcinogenic risk. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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Review

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21 pages, 680 KiB

Open AccessReview

Marine Copepods as a Microbiome Hotspot: Revealing Their Interactions and Biotechnological Applications

by Jiantong Feng, Maurizio Mazzei, Simona Di Gregorio, Luca Niccolini, Valentina Vitiello, Yingying Ye, Baoying Guo, Xiaojun Yan and Isabella Buttino

Water 2023, 15(24), 4203; https://doi.org/10.3390/w15244203 - 05 Dec 2023

Viewed by 1765

Abstract

Copepods are the most abundant organisms in marine zooplankton and the primary components of the food chain. They are hotspots for highly adaptable microorganisms, which are pivotal in biogeochemical cycles. The microbiome, encompassing microorganisms within and surrounding marine planktonic organisms, holds considerable potential [...] Read more.

Copepods are the most abundant organisms in marine zooplankton and the primary components of the food chain. They are hotspots for highly adaptable microorganisms, which are pivotal in biogeochemical cycles. The microbiome, encompassing microorganisms within and surrounding marine planktonic organisms, holds considerable potential for biotechnological advancements. Despite marine microbiome research interests expanding, our understanding of the ecological interactions between microbiome and copepods remains limited. This review intends to give an overview of the recent studies regarding the microbiome associated with marine copepods, with particular focus on the diversity of bacteria and fungi. The significance of copepod-associated microbiomes in different contexts, such as aquaculture and biodegradation processes, was evaluated. The ability of the microbiome to mitigate harmful bacterial growth in cultured organisms was also explored. The microbiome associated with copepods has demonstrated efficacy in reducing the proliferation of detrimental bacteria in aquaculture, paving the way for the commercial utilization of natural zooplankton in fish rearing. Additionally, copepod-associated microbiomes may play a role in addressing marine environmental challenges, such as the bioremediation of polluted marine matrices. Overall, this review represents a basis for investigating intricate copepod-associated microbiomes and their diverse applications, enhancing our comprehension of the ecological and evolutionary significance of marine microbiomes. Full article

(This article belongs to the Special Issue Environment and Ecosystems Research for Natural Waters)

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