Improve Water Quality Research Articles

Enhancing Florida red tilapia aquaculture: biofloc optimization improves water quality, pathogen bacterial control, fish health, immune response, and organ histopathology across varied groundwater salinities.

Freshwater scarcity poses challenges to aquaculture worldwide, including countries like Egypt. In this study, we investigate the feasibility of integrating underground saline water (USW) with varying salinities into a Biofloc (BFT) system for desert mariculture of Florida red tilapia (FRT) and its impacts on water quality, fish performance and health. Four BFT treatments (C/N ratio = 15) were examined in triplicate using four salinity levels 0 ppt, 12 ppt, 24 ppt and 36 ppt, expressed as S0, S12, S24 and S36, respectively. For 75 days, a total of 12 fiberglass tanks (each 250L-1 water) were used to store FRT fry (average weight of 1.73 ± 0.01g/fish). The fish were fed an experimental diet (protein/fat = 30/5) and an additional carbon source of rice bran. The results revealed that group S12 showed better growth indicators, higher survival rate, lower FCR, and lower ammonia levels, while group S0 exhibited lower growth indicators (final weight, weight gain, and specific growth rate) than all groups. The serum kidney, liver, and antioxidant indices performed better in the S12 group. At 12 ppt, the immune-related parameter (IgM) increased by 22.5%, while the stress parameter (cortisol) decreased by 40.8% compared to the S0 group. The liver and intestinal histopathological results revealed that the S12 and S24 groups performed better. Pathogenic bacterial load counts favored the S24 group, which had the lowest number among the groups studied. The recommended salinity for FRT cultivation in USW and BFT is 19.94-20 ppt, determined by polynomial regression of FW and FCR.

Water-Energy-Food-Forest Nexus in The Amazon Conservation Unit

Objective: The general objective of this research is to analyze the integration of forests into the water-energy-food nexus in a Conservation Unit in the Brazilian Amazon, aiming to verify how traditional populations, in whose areas they inhabit, use two natural and non-wood resources for their survival. Theoretical Framework: The approach to the water-energy-food nexus emerged in the last decade around concerns such as global trends in population growth, economic growth and climate changes that place pressure on water, energy, food and forest resources. Method: The adopted methodology uses a qualitative approach, given the importance of understanding how the water, energy, food and forest resources in the Lago do Cuniã Extractive Reserve are explored. An exploratory-descriptive type of research, with a central concern in carrying out a preparatory analysis of a known context, meanwhile little explored in the Amazon. The collection of data was carried out by means of interviews with the application of questionnaire and application of non-participant observation techniques. Results and Discussion: The results demonstrate that studies with a nexus approach with four elements provide no understanding of the exploration of sustainable development in the environment of conservation units. Furthermore, the study reveals that maintaining forest resources improves water quality not only, but also controls erosion and resilience against droughts and floods; Contributing to the energy supply, in addition, contributes to the safety of feeding the residents of the conservation unit. Research Implications: For public policy makers, the results demonstrate the need for management practices for the conservation of forests, protection of the quantity and quality of existing rivers and lakes in the conservation unit and protection of aquatic and agricultural ecosystems. Originality/Value: The originality of the article is in the analysis of the role of addressing water, energy and food within an area of ​​environmental protection in the Amazon, and by including the element forest it was possible to find out its triangulation with the other elements and their implications for economic, social and economic factors. you set the mood.

Assessing the impact of rainfall on water quality in a coastal urban river utilizing the environmental fluid dynamics code

The Haihe River, flowing through Tianjin City, grapples with pollution challenges, notably high levels of nitrogen (N) and phosphorus (P) leading to eutrophication and unpleasant odors, particularly aggravated by rainfall. This study used Environmental Fluid Dynamics Code to comprehensively analyze the water environment under three scenarios: low flow year, normal flow year, and high flow year. The investigation delves into N and P concentrations, computes atmospheric deposition fluxes, and evaluates the loads and retention ratios of N and P in the urban river network of Tianjin City. Scenario analysis reveals distinct trends, with high flow years associated with elevated N and hydrodynamics levels, while low flow years exhibit contrasting patterns. Key findings include 1) wet deposition fluxes contributing 21% of NH4+-N and 9% of TP river loads, 2) continuous rainfall and runoff resulting in immediate or delayed increases in NH4+-N, TN, and TP concentrations in surface water, 3) an increase in average N:P mole ratios downstream along the Haihe River, and 4) N and P mean retention ratios were 48% and 63%, respectively. The study suggests that implementing sponge city construction and sustainable drainage systems may improve water quality by mitigating the direct discharge of rainfall runoff into the river.

Assessment of Natural Bentonite Efficacy for Dye Removal in Textile Wastewater Treatment : Implication for Mitigating River Citarum Pollution

Textile industries contribute significantly to the economy but release harmful pollutants into the environment, especially rivers. The effluent from the textile industry contained toxic dyes that can harm the river ecosystem. Several studies have been conducted to reduce toxic dyes in a river system using bentonite as an adsorbent to reduce river pollution effectively. However, the effectiveness of bentonite still needs to be tested again using textile liquid waste that has not gone through any waste processing at all. Citarum is one of the main rivers on Java Island, which suffers from textile effluent, especially azo dyes which are toxic, mutagenic and carcinogenic which can harm the aquatic ecosystem. Therefore, this study aims to implement natural bentonite as an adsorbent to remove dyes from textile wastewater. We performed a laboratory test to adsorption on bentonite and textile wastewater considering the variation of adsorbent weight of 10 g and 20 g in 100 mL of textile wastewater stirred in an Erlenmeyer flask at room temperature for 0-300 minutes. The initial concentration of textile wastewater used was 10%, 30%, and 50%. We found that the maximum dye removal efficiency was 91.25% with 10% initial concentration treatment, 20 g adsorbent weight, and 60 minutes contact time. Longer contact time will increase the removal efficiency and adsorption capacity, while higher adsorbent dosage will decrease the concentration of dyes in wastewater. Efficient textile wastewater treatment has improved water quality, effectively meeting river water quality standards and environmental regulations.

Food web collapse and regime shift following goldfish introduction in permanent ponds.

In a global context of invasive alien species (IAS), native predators are often eradicated by functionally different IAS, which may induce complex cascading consequences on ecosystem functioning because of the key role predators play in structuring communities and stabilizing food webs. In permanent ponds, the most abundant freshwater systems on Earth, global human-mediated introductions of alien omnivores such as the pet trade goldfish are driving broad-scale patterns of native predators' exclusion, but cascading consequences on food web structure and functioning are critically understudied. We compared food webs of naturally fishless ponds versus ponds where dominant native predators (newts) had been extirpated by invasive goldfish within the last decade. Integrating community-wide isotopic, taxonomic and functional traits approaches, our study reveals that pond food webs collapsed in both vertical and horizontal dimensions following goldfish introduction and the associated exclusion of native predators. Consumer taxonomic diversity was drastically reduced, essentially deprived of amphibians as well as predatory and mobile macroinvertebrates to the profit of burrowing, lower trophic level consumers (detritivores). Changes in community structure and function underlined a regime shift from a macrophyte-dominated system mainly characterized by benthic primary production (periphyton), to a macrophyte-depleted state of ponds hosting communities mainly associated with phytoplankton primary production and detritus accumulation, with higher tolerance to eutrophication and low dissolved oxygen concentration. Results underline major impacts of widely introduced omnivores such as the goldfish on the functioning of pond ecosystems with potentially dramatic consequences on the key ecosystem services they deliver, such as global biodiversity support or water quality improvement. They also shed light on the key role of submerged aquatic vegetation in supporting diverse communities and complex food webs in shallow lentic systems and call for urgent consideration of threats posed by IAS on ponds' ecosystems by managers and policymakers.

Long-term impact of basin-wide wastewater management on faecal pollution levels along the entire Danube River

The Danube River is, at 2857 km, the second longest river in Europe and the most international river in the world with 19 countries in its catchment. Along the entire river, faecal pollution levels are mainly influenced by point-source emissions from treated and untreated sewage of municipal origin under base-flow conditions. In the past 2 decades, large investments in wastewater collection and treatment infrastructure were made in the European Union (EU) Member States located in the Danube River Basin (DRB). Overall, the share of population equivalents with appropriately biologically treated wastewater (without disinfection) has increased from 69% to more than 85%. The proportion of tertiary treatment has risen from 46 to 73%. In contrast, no comparable improvements of wastewater infrastructure took place in non-EU Member States in the middle and lower DRB, where a substantial amount of untreated wastewater is still directly discharged into the Danube River. Faecal pollution levels along the whole Danube River and the confluence sites of the most important tributaries were monitored during four Danube River expeditions, the Joint Danube Surveys (JDS). During all four surveys, the longitudinal patterns of faecal pollution were highly consistent, with generally lower levels in the upper section and elevated levels and major hotspots in the middle and lower sections of the Danube River. From 2001 to 2019, a significant decrease in faecal pollution levels could be observed in all three sections with average reduction rates between 72 and 86%. Despite this general improvement in microbiological water quality, no such decreases were observed for the highly polluted stretch in Central Serbia. Further improvements in microbiological water quality can be expected for the next decades on the basis of further investments in wastewater infrastructure in the EU Member States, in the middle and lower DRB. In the upper DRB, and due to the high compliance level as regards collection and treatment, improvements can further be achieved by upgrading sewage treatment plants with quaternary treatment steps as well as by preventing combined sewer overflows. The accession of the Western Balkan countries to the EU would also significantly boost investments in wastewater infrastructure and water quality improvements in the middle section of the Danube. Continuing whole-river expeditions such as the Joint Danube Surveys is highly recommended to monitor the developments in water quality in the future.

Assessing Chlorophyll-a Variations in Caspian Sea during the COVID-19 Pandemic.

The COVID-19 pandemic's disruptions to human activities prompted serious environmental changes. Here, we assessed the variations in coastal water quality along the Caspian Sea, with a focus on the Iranian coastline, during the lockdown. Utilizing Chlorophyll-a data from MODIS-AQUA satellite from 2015 to 2023 and Singular Spectrum Analysis for temporal trends, we found a 22% Chlorophyll-a concentration decrease along the coast, from 3.2 to 2.5mg/m³. Additionally, using a deep learning algorithm known as Long Short-Term Memory Networks, we found that, in the absence of lockdown, the Chlorophyll-a concentration would have been 20% higher during the 2020-2023 period. Furthermore, our spatial analysis revealed that 98% of areas experienced about 18% Chlorophyll-a decline. The identified improvement in coastal water quality presents significant opportunities for policymakers to enact regulations and make local administrative decisions aimed at curbing coastal water pollution, particularly in areas experiencing considerable anthropogenic stress.

Assessing the Response Mechanisms of Elevated CO2 Concentration on Various Forms of Nitrogen Losses in the Golden Corn Belt

AbstractNitrogen (N) loss is a significant source of water quality pollution in alluvial watersheds. However, the mechanisms linking N loss and elevated CO2 concentration (eCO2) are not well recognized. In this study, we comprehensively calibrated the SWAT model equipped with a dynamic CO2 input and response module to investigate the response mechanisms between multiform N losses and eCO2 in a representative large‐scale watershed. Results revealed nitrate loss under eCO2 exceeding 100% in some upstream zones under the SSP5‐8.5 scenario (P < 0.05) compared to the constant CO2 concentration. This was directly related to the great increase in hydrological variables, which were the carriers of N losses, and the intensive inputs of N fertilizer. Results also found that nitrate leaching was greater than the other two processes for future periods, peaking at 309.3%, as compared to the baseline period. The findings suggested reducing fertilizer inputs by 10%–20% was promising, especially for reducing nitrate loss through runoff and leaching by up to 17.7% and 12.2%. This study explored the mechanisms of increased N loss in response to eCO2 and provided scientific evidence for early warning and making decisions to improve water quality at a large watershed scale.

Artificial Intelligence for Application in Water Engineering: The Use of ANN to Determine Water Quality Index in Rivers

To improve water quality, total daily loads must be established, and this requires determining the quality of the water in rivers, storage tanks, ponds, and coastal areas. Current methods to evaluate water quality involve the collection of water samples for subsequent laboratory analysis. Although these technologies offer precise measurements for a specific location and time, they are expensive, time-consuming, and do not provide the continuous, temporal, or spatial conditions of water quality that are required for managing, assessing, and monitoring water quality. In order to calculate the water quality, the water quality index is modeled using artificial neural network models that incorporate feedforward neural network backpropagation neural networks and radial neural networks. The water quality index of Malaysia’s Klang River was determined by training the artificial network using six major sub-quality parameters. Compared to the current method, the artificial neural network simplifies and expedites the computation of the water quality index. The artificial neural network method could provide a significant saving in terms of money and time while offering a robust assessment of water quality. The proposed method could also be used as an early warning system for pollution of water bodies. The best artificial neural network was the feedforward neural network with one hidden layer containing 5 neurons. Furthermore, conventional approaches for calculating the water quality index rely on empirical equations, often introducing a high degree of approximation and uncertainty into the results. Moreover, these equations cannot be applied when some parameters are not measured. In contrast, the artificial neural network methods and technique offer an efficient and straightforward process for estimating and creating prediction models for water quality index. Doi: 10.28991/CEJ-2024-010-07-012 Full Text: PDF

Assessing drinking water quality based on water quality indices, human health risk, and burden of disease attributable to heavy metals in rural communities of Yazd County, Iran, 2015–2021

The water quality indices, health risk, and burden of disease attributable to heavy metals in rural communities of Yazd County, Iran during 2015–2021 were studied. The drinking water quality index (DWQI) based on 27 parameters (including heavy metals) and heavy metal pollution index (HPI) were used for assessing drinking water quality. The health risk and burden of disease from heavy metals in drinking water were estimated in terms of hazard quotient (HQ), hazard index (HI), incremental lifetime cancer risk (ILCR), and disability-adjusted life year (DALY). Based on the DWQI scores by community, the drinking water quality in rural communities of Yazd County was characterized as good for 61 %, fair for 25 %, marginal for 2 %, and poor for 12 %. The distribution of the rural communities into the HPI categories was as follows: 43 % for excellent, 36 % for good, 14 % for poor, and 7 % for unsuitable. In about 20 % of the rural communities, the average HI level of heavy metals was higher than the boundary limit of one. The highest average HQ level at the county level was related to arsenic (As) to be 0.44. In all the communities, the total ILCR values of the heavy metals were in the category of significant increased cancer risk (10−6 to 10−4). At the county level, As and cadmium (Cd) exhibited the two highest cancer risk levels to be 1.96 × 10−4 and 1.87 × 10−4 for ILCR, respectively. The DALY rate (per 100,000 people) induced by exposure to the heavy metals via drinking water was 13.9, which was considered relatively high as compared to that of other drinking water pollutants obtained in the previous studies. The drinking water quality improvement through decreasing Cd and As levels below the standard values can drastically reduce the attributable burden of disease and promote the public health in the rural communities.

Assessment of the Applicability of Compact Aerating Reactors for the Improvement of Water Quality in a Small Water Body Functioning in an Agricultural Catchment

The study investigates water quality in a small water body in an agricultural catchment in a zone of temperate climate (East Poland). The pond is affected by annual mass cyanobacterial blooms, limiting its use. The improvement of the state of water quality involved the application of underwater aerating reactors. The economic analysis of their application was also an important issue. The analysis of the effectiveness of the proposed solution was conducted from February to October 2021. The results from the analysis of water from the pond showed that the nutrient content and phytoplankton structure conformed to the trophic status of eutrophy–hypertrophy. The primary factors causing excessive eutrophication of the pond included nutrient supply from the river, sediments, and fallen tree leaves. No development of cyanobacterial scum was observed in the water body, a phenomenon which was interpreted as the effect of the operation of the aerators ensuring additional water circulation in the pond and promoting its aeration. It was found that permanent improvement of the water quality in the studied water body is largely dependent on limiting the nitrogen and phosphorus supply to the pond. This should involve the application of systems combining traditional hydrotechnical infrastructure with Nature-Based Solutions (NBS). The economic analysis of the use of underwater aeration reactors confirmed the validity of searching for alternative solutions to power them, e.g., a photovoltaic installation. When designing a reactor system with a photovoltaic installation, it is necessary to choose the correct dimensions to reduce construction costs and, thus, increase the profitability of the potential investment.

Study on Mechanical Properties of Sandy Soil Solidified by Enzyme-Induced Calcium Carbonate Precipitation (EICP)

Earth–rock dams are widely distributed in China and play an important role in flood control, water storage, water-level regulation, and water quality improvement. As an emerging seepage control and reinforcement technology in the past few years, enzyme (urease)-induced calcium carbonate precipitation (EICP) has the qualities of durability, environmental friendliness, and great economic efficiency. For EICP-solidified standard sand, this study analyzes the effect of dry density, amount of cementation, standing time, perfusion method, and other factors on the permeability and strength characteristics of solidified sandy soil by conducting a permeability test and an unconfined compression test and then working out the optimal solidification conditions of EICP. Furthermore, a quantitative relationship is established between the permeability coefficient (PC), unconfined compressive strength (UCS), and CaCO3 generation (CG). The test findings indicate that the PC of the solidified sandy soil decreases and the UCS rises as the starting dry density, amount of cementation, and standing time rise. With the increase of CG, the PC of the solidified sandy soil decreases while the UCS increases, indicating a good correlation among PC, UCS, and CG. The optimal condition of solidification by EICP is achieved by the two-stage grouting method with an initial dry density of 1.65 g/cm3, cementation time of 6 d, and standing time of 5 d. Under such conditions, the permeability of the solidified sandy soil is 6.25 × 10−4 cm/s, and the UCS is 1646.94 kPa. The findings of this study are of great theoretical value and scientific significance for guiding the reinforcement of earth–rock dams.

Quantifying pollution contributions across a reticular river network: Insights from water quantity composition analysis

Calculating pollution load contribution rate is an effective way to identify pollution sources, which is important in improving water quality management. Reticular river networks pose unique challenges in pollution load contribution rates calculation, as current methods are not applicable to river networks with uncertain flow direction or exhibit low computational efficiency. This study addresses this challenge by offering a new method that transforms the calculation of water quantity constituents in assessment sections into a conserved substance concentration problem. Applied to a typical reticular river network, Suzhou River Network in the Tai Lake Basin, China, total phosphorus pollution load contribution rates demonstrate significant spatial and temporal variations, and are closely associated with factors such as pollution load, rainfall, and water diversion. The developed method stands out for its simplicity and improved computational efficiency, making it particularly suitable for regions with indeterminate flow directions. Quantifying the contribution of pollution sources in reticular river networks to identify sources of pollution helps to improve the precision and pertinence of water pollution management programs.

Farm dam enhancement significantly improves water quality

Artificial water bodies in agricultural landscapes (hereafter ‘farm dams’) are established primarily to support livestock and crop production but also provide habitats for a wide range of native species. Managing water quality in farm dams is essential to animal production and biodiversity. Farm dam enhancement, which includes restricting direct access of stock to dams, can improve water quality in farm dams, by reducing soil erosion and direct faecal contamination, as well as reducing the trampling, grazing, and browsing of vegetation in the immediate catchment. We tested farm dam enhancement as a tool to improve and maintain water quality in 109 farm dams across 34 farms over three years in the sheep-wheat belt of southeast Australia. Using Bayesian Linear Mixed Models, we found that farm dam enhancement significantly reduced levels of phosphorus, nitrogen, turbidity, thermotolerant coliforms, Escherichia coli, and pH. Furthermore, our study revealed links between dam enhancement, increases in vegetation cover, and improved water quality. Our results show that restoration efforts in the surrounds of dams can have positive results on water quality. They highlight the importance of restoration in agricultural landscapes to both agricultural production and biodiversity.

Характеристика сучасного стану іхтіофауни озера Котлован як малої штучної водойми м. Дніпро

Purpose. To investigate the current state of nearshore and pelagic communities of ichthyofauna of an artificial water body: Lake Kotlovan in the city of Dnipro. To develop a set of recommendations and bioreclamation measures to improve and maintain a balanced ecological state of the water body, to increase its recreational value. Methodology.The study of ichthyofauna was carried out in the lake Kotlovan (total area 13.4 hectares), which was artificially created in the late 1960s and 1970s, located in the Industrial District of Dnipro in the area of industrial development. The study was carried out in September 2021 - October 2022 in three main nearshore biotopes of the water body. Ichthyological samples were collected in the nearshore shallow water zone with a small-mesh (fry) seine of 15 meters long with a mesh size of 7 mm in the wings and 3 mm in the codend. Fish selected for further analysis were preserved in a 4.5% formalin solution. Processing and analysis of the collected samples were carried out at the research center “Aquatic Bioresources and Aquaculture” of the Dnipro State Agrarian and Economic University (DSAEU). Generally accepted methods of mathematical analysis were used to process the results. The study was carried out in accordance with the Program for conducting scientific fisheries research of the Scientific Research Center “Aquatic Bioresources and Aquaculture” of the DSAEU for 2022–2026. Findings. The peculiarities of the species composition and distribution of the spontaneously formed ichthyofauna of an artificial water body under the impact of negative factors - discharges of enterprises, communal and household effluents and active recreation - have been established. Ichthyofauna of the lake Kotlovan is impoverished and represented by only 10 species (4 families). The composition of the ichthyofauna lacks bottom-dwelling fish and some littoral species (representatives of the familiesCobitidae, Siluridae, Syngnathidae, Gasterosteidae, Gobiidae), a certain deformation of the taxonomic structure was observed. The absence of individual families of ichthyofauna is an atypical situation for most water bodies in this region. This is due to the artificial development of ichthyofauna and the complex negative effect of the anthropogenic factor and internal trophic relationships. Recommendations on bioreclamation measures for the development of a stable ichthyocenosis with the improvement of the trophic structure and ecological condition of the artificial water body have been developed. Originality. The species composition of the ichthyofauna of an artificially created completely isolated water body in the city of Dnipro, which has existed for about 50 years, was determined for the first time. The current structure of fish groups according to species composition, conservation status, relative abundance, type of feeding and origin were investigated. A high level of the infestation of bleak Alburnus alburnus and silver bream Blicca bjoerkna with ligulosis and perch Perca fluviatilis with eustrongylidosis was observed. Measures and recommendations for improving the state of the ichthyofauna of Lake Kotlovan and increasing the recreational value of the water body were proposed. Practical value. Based on the conducted study, it is possible to evaluate and forecast the future state of the ichthyofauna of small, artificially created and isolated water bodies under anthropogenic pressure. The proposed bioreclamation measures will allow increasing the stability of ichthyocenosis and improving water quality as well as the conditions for recreation of residents, recreational fishing within the boundaries of a large city (a complex of ecosystem services). Keywords: city of Dnipro, artificial water body, ichthyofauna, bioreclamation, biotope, recreation, ecosystem services.

Large shallow lake response to anthropogenic stressors and climate change: Missing macroinvertebrate recovery after oligotrophication (Lake Balaton, East-Central Europe)

East-Central Europe's largest shallow lake, Balaton, experienced strong eutrophication in the 1970–80s, followed by water quality improvement and oligotrophication by 2010 CE. Recently however, repeated cyanobacterial blooms occurred and warned that internal P-recycling can act similarly to external P load, therefore we need a better understanding of past water level (WL) and trophic changes in the lake. In this study we discuss the last 500-yr trophic, WL and habitat changes of the lake using paleoecological (chironomids, pollen) and geochemical (sediment chlorophyll, TOC, TS, TN, C/H ratio, major and trace element) methods. We demonstrate that the most intensive and irreversible change in the macroinvertebrate fauna occurred during the period of economic boom between the First and Second World War (∼1925–1940 CE), when large-scale built-in and leisure use of the lake has intensified. At that time, the Procladius-Microchironomus-Stempellina dominated community transformed to Procladius-Chironomus plumosus-type-Microchironomus community that coincided with land use changes, intensified erosion and water-level regulation in the lake with the maintenance of year-round high WL. This was followed by the impoverishment and population size decrease of the chironomid fauna and Procladius dominance since 1940 CE, without any recovery after 1994 CE despite the ongoing oligotrophication. Accelerated rate of change and turnover of the fauna was connected to an increase in the benthivorous fish biomass and eutrophication. The basin lost almost completely its once characteristic Stempellina species between 1927 and 1940 CE due to trophic level increase and seasonal anoxia in the Szemes Basin. Reference conditions for ecosystem improvement were assigned to 1740–1900 CE. We conclude that in spite of the ongoing oligotrophication, the re-establishment of the Procladius-Microchironomus-Stempellina assemblage is hampered, and requires fish population regulation.

Hydrodynamics of artificial and oyster-populated breakwaters: A laboratory study with scaled-down oyster castles under unidirectional flow

Oyster populations within the Chesapeake Bay have been drastically reduced over the last century mainly due to unregulated human activities and diseases. Regulations and restoration efforts have focused on restoring oyster populations while also considering their ability to provide ecosystem services, such as coastal protection and water quality improvement, among others. To promote oyster growth and the settlement of new populations, a recent technique adopted along the east coast of the US is the use of oyster castles (OCs). OCs have proven effective in recruiting and retaining oysters and in promoting both vertical growth and horizontal expansion of oyster habitats. OCs are widely used in coastal protection as greener alternative to common engineering solutions. We quantified hydrodynamic differences that occur around these OCs during their early stage (i.e. castles without oysters), and with fully developed oysters covering the surface of the castles through a series of laboratory experiments. The experiments were conducted in a recirculating Odell-Kovasznay type channel at the Ecohydraulics and Ecomorphodynamics Laboratory (EEL) at the University of Illinois. OCs (both with and without oysters) were 3D printed at 1:7 scale to fit the canal, and Particle Image Velocimetry (PIV) was used for 2D flow characterization. Data showed noticeable differences in flow acceleration atop the castles when covered with oysters, as well as an increase in the generation and distribution of turbulent kinetic energy atop and around the oyster-covered castles. Magnitudes and spatial distribution of Reynolds stresses were also affected by the presence of oysters in both submerged and near-emergent conditions. Challenges associated with the estimation of the drag coefficient for both gray and oyster-covered OCs highlighted the need for more data besides the centerline 2D PIV output. Further research involving the whole three-dimensional structure of the flow, in both unidirectional and oscillatory conditions, will allow us to provide relevant guidelines on the design and use of oyster-populated breakwaters as a viable nature-based solution for coastal protection within low-energy environments.

Does stricter sewage treatment targets policy exacerbate the contradiction between effluent water quality improvement and carbon emissions mitigation? An evidence from China

Rapid expansion and upgrading of wastewater treatment facilities globally, driven by stricter wastewater policies, significantly contribute to carbon emissions. China has contributed 30 % of carbon emissions in the world, 1 % of which comes from wastewater treatment, necessitating more understanding of the impact of policies, especially the stringent “10-Point Water Plan” policy. From a micro perspective, this study uses the difference-in-differences method to analyze the impact of wastewater treatment policies on water and carbon issues in China’s 2894 wastewater treatment plants (WWTPs), and delves into the heterogeneity, and mechanisms across various dimensions. The results show that stricter sewage treatment policy decrease effluent concentration of the chemical oxygen demand (COD) by 2.35 %, and also cause a 1.74 % rise in carbon emissions per 10,000 m3 of wastewater treated, intensifying the short-term contradiction, while the contradictions may fall in the long term. It is more significant in southern regions and the cities with lower environmental regulation intensity. Also, there are significant differences in different wastewater treatment technology and scale. Significant improvements in effluent water quality are observed in WWTPs with 100,000 to 200,000 m3/day capacity and those using biofilm treatment technology. Through mechanism analysis, reasonable expansion of urban pipelines and WWTPs, promotion of biofilm treatment technology, reduction of energy consumption, and improvement of pollutant reduction efficiency are feasible paths to improve water quality and reduce carbon emissions. This research provides a perspective on solving water-carbon contradictions in WWTPs, holding critical significance for urban wastewater treatment and carbon emission management.

Application of the Ocean Health Index to assess ocean and coastal conditions of the Tokyo Metropolitan area

Ocean ecosystem services are fundamental to coastal economic development and climate regulation. The Tokyo Metropolitan Area (TMA) is one of the world’s most significant bay areas, with its economic development and residents relying on a healthy ocean and diverse marine ecosystem services. Post-World War II, the coastal zones of TMA have suffered from various human-induced stresses and impacts, jeopardizing the capacity of ocean ecosystem services and sustainable development. Although recent years have seen improvements in basic marine water quality, other ecosystem health issue, such as biodiversity, carbon storage, coastal protection are remain limited and require comprehensive enhancement. To better understand the current state of ocean health, promote more comprehensive ocean management decisions and plans, and support sustainable development in the region, it is essential to evaluate the ocean’s condition in the TMA and to assess future trends and risks. The Ocean Health Index (OHI) offers a comprehensive framework to evaluate global and regional ocean health conditions and their ecosystem services. This study applies the OHI to assess the ocean and coastal health of TMA, with indicators and reference points adjusted based on local conditions. From 2014 to 2019, the OHI assessment results indicate that TMA obtained an overall OHI score of 49 (out of 100), with goals ranging from 13 to 87. The environmental and social goals, such as Tourism and Recreation (87), Clean Water (67), Coastal Livelihoods and Economies (62), Sense of Place (62), and Artisanal Fishery Opportunity (51), are relatively high. In contrast, the ecological goals, such as Biodiversity (14), Carbon Storage (13), Coastal Protection (38), and Food Provision (24), are relatively low. This case study highlights strategies for improving ocean health conditions in TMA from both OHI goals and management structure perspectives. The methods and results provide a quantitative tool for regional marine and coastal management in TMA, aiding regional management organizations to establish quantifiable objectives for actions that were previously difficult to quantify. These results can indirectly promote the establishment of more comprehensive and holistic regional management organizations in TMA, which is currently fragmented, thereby effectively enhancing ocean health in TMA.

Eco-Engineering Improves Water Quality and Mediates Plankton–Nutrient Interactions in a Restored Wetland

Eco-engineering is an important tool for wetland restoration, but there are still large theoretical and application gaps in the knowledge of the effects of eco-engineering implementation on the interactions between environmental conditions and organisms during wetland restoration processes. In this study, we investigated water quality parameters and plankton communities in a national wetland park to clarify the mechanism of changes in plankton community structure and their ecological networks before and after the eco-engineering project. Undoubtedly, we found water quality was significantly improved with increased metazooplankton diversity after the implementation of eco-engineering. Ecological engineering reduced the effect of farmland drainage on the restored wetland and changed the phytoplankton community structure, which significantly reduced the relative abundance of Cyanobacteria and increased the relative abundance of Bacillariophyta. The structural equation modeling revealed that the total effect of metazooplankton on phytoplankton was significantly enhanced and associated with weakened relationships between phytoplankton and environmental variables after eco-engineering. In addition, the ecological network analysis also showed that the network connection between phytoplankton and metazooplankton was stronger after the eco-engineering implementation, leading to an enhanced biotic interactions in different trophic levels. These results indicate that the main approach to regulating primary producers in wetland ecosystems changed from “bottom-up” control to a combination of “bottom-up” and “top-down” control under the intervention of artificial recovery measures. Our findings shed new light on the effects of eco-engineering on the interactions between water quality and organisms and provide a scientific basis for the sustainable management of wetland ecosystems.