Coastal Water Quality Research Articles

Water quality and climate variability of urban and tourism areas in Thailand and northern Vietnam: correlations and possible influences on nearby coastal shrimp farms.

This research explored the long-term relationships of climate parameters and coastal water quality nearby shrimp farms in two countries. In Thailand, two sampling points in canals located in Bangkok and Trang provinces were selected as the urban and tourism areas, respectively. In northern Vietnam, the canals located in Thai Binh and Quang Ninh provinces were used as the urban and tourism areas, respectively. The diurnal monitoring of water quality and weather was performed at each site to evaluate the relationships between climate and water quality, pollution load, and risk analysis. A questionnaire was also used to assess the climate and water exposure, vulnerability, and adaptability of each site. All data were ranked on a scale of 1 to 5 to integrate each factor. It was determined that the main water quality problem was fecal pollution. Notably, aquaculture farming in northern Vietnam is more vulnerable than in Thailand; however, Vietnam farmers were adaptable for climate variability.

Automation of Water Quality detection using Machine Learning

Coastal water quality management is a public health concern, as poor coastal water quality can potentially harbor pathogens that are dangerous to human health. Tourism-oriented countries need to actively monitor the condition of coastal water at tourist popular sites during the summer season. In this study, routine monitoring data of Escherichia Coli and enterococci across 15 public beaches in the city of Rijeka, Croatia, were used to build machine learning models for predicting their levels based on environmental parameters as well as to investigate their dynamics and relationships withenvironmental stressors. Gradient Boosting algorithms (Catboost, Xgboost), Random Forests, Support Vector Regression and Artificial Neural Networks were trained with routine monitoring measurements from all sampling sites and used to predict E: Coli and enterococci values based on environmental features. The evaluation of stability and generalizability with 10-fold cross validation analysis of the machine learning models, showed that the Catboost algorithm performed best with R2 values of 0.71 and 0.68 for predicting E: Coli and enterococci, respectively, compared to other evaluated ML algorithms including Xgboost, Random Forests, Support Vector Regression and Artificial Neural Networks.

Analysis of Organic Matter Content in Water and Sediment in The Coastal Waters of Bengkalis Island, Riau Province

Anthropogenic activities in the coastal waters of Bengkalis Island, Riau Province are thought to have increased due to human activities (settlements, ports, agriculture, households and industry). This caused an increase in organic matter in water and sediment in coastal waters. The content of organic matter in water and sediment can be used as an indicator of the quality of coastal waters. The research aimed to analyze the content of organic matter in water and sediment in the coastal waters of Bengkalis Island. The used purposive sampling. The research was carried out in April – July 2021, consisting of 4 research stations and each station consisted of 3 sampling points. Sampling was carried out in the intertidal zone in the north and south of Bengkalis Island, namely station I (Air Putih Village), Station II (Jangkang Village), station III (Selat Baru Village) and station IV (Liong Estuary). The results of the analysis of organic matter content in seawater ranged from 32.39-34.89 mg/l, the highest was at station I and the lowest was at station II. The results of the analysis of organic matter content in sediment of Bengkalis Island ranged from 0.01-0.31%, the highest was at station I and the lowest was at station II. A simple linear regression test showed that the relationship between the organic matter content of seawater and sediments in the coastal waters of Bengkalis Island was classified as a strong relationship with a correlation coefficient (r) 0.720 and a coefficient of determination (R2) 0.518. The results also show that the coastal waters of Bengkalis Island have a type of sediment fraction which is dominated by sandy mud.

Connecting India's coastal monitoring program with UN Sustainable Development Goal 14

The UN Sustainable Development Goal (SDG) 14 sets targets for nations to reduce marine pollution, ocean acidification, and sustainable use of coastal and ocean resources, which requires data on nutrient load, litter/plastics, pH, and biodiversity. Monitoring programs with large-scale and long-term data is an important source of environmental information and can play a crucial role in implementing the SDGs. This paper uses the Sea Water Quality Monitoring (SWQM), the coastal monitoring program of India, as a case study to examine the extent to which the monitoring program contributes to achieving the SDG 14 targets. The SWQM program is a multidisciplinary, long-term coastal monitoring program initiated by the Ministry of Earth Sciences (MoES), Government of India, in 1990 to assess the coastal water quality. The paper highlights the interrelationships between the SWQM and SDG 14 targets (14.1.1, 14.2, 14.3, and 14.5) and discusses the challenges and opportunities of linking the national program to SDGs. Strengthening the program by increasing monitoring locations, sampling additional environmental parameters and biodiversity components, and using advanced scientific tools can be an efficient and pragmatic approach to SDG 14 implementation through the SWQM program. Aligning the long-term monitoring program and other research programs of a nation to the SDGs could provide potential co-benefits and more efficient utilization of funds.

Identifying locations of sewage pollution within a Hawaiian watershed for coastal water quality management actions

Study regionPuakō, Hawai‘i Island. Study focusLocations of sewage pollution in the Puakō watershed were identified through measurements of sewage indicators at groundwater wells and within Puakō’s and adjacent resorts’ shoreline waters. Dye tracer tests, water quality, δ15N macroalgal, and δ15N- and δ18O-NO3- measurements, along with stable isotope mixing models, were combined to assess water quality impairment caused by different Onsite Sewage Disposal System (OSDS) types, and used to predict water quality improvements from future management actions. New hydrological insights for the regionSewage indicators were highest within Puakō’s shoreline waters, including: Enterococcus spp., Clostridium perfringens, human-associated Bacteroides, and δ15N-NO3-. Mixing model results using δ15N- and δ18O-NO3- suggest that sewage was a dominant NO3- source, comprising > 40% at 10 of the 16 shoreline stations. δ15N macroalgae measurements confirmed presence of sewage at most stations. In groundwater wells and at adjacent resorts’ shoreline waters, sewage indicators were low, and δ15NO3-was indicative of soils and fertilizers. Puakō dye tracer tests revealed that sewage reached the shoreline within 5 h to 10 d, and that OSDS type did not affect travel time. Water quality was similar in front of homes with different OSDS. In conclusion, sewage is entering the groundwater at Puakō, and the underlying geology, rather than OSDS type, primarily controls the speed at which sewage reaches the shoreline. Our findings highlight the need for improved sewage treatment and collection at Puakō.

Understanding the effects of periodic freshening and salinization on coastal water quality and aquifer sediments through laboratory-based column experiments

The coastal aquifers experience periodic freshening and salinization events due to frequent changes in hydrological conditions. Such frequent changes have vital effects on the coastal groundwater quality and aquifer properties. This forms the basis of the present study. Laboratory-based column experiments have been conducted to investigate the long-term impact of such periodic events on coastal groundwater quality and aquifer sediment characteristics. Conditions similar to the natural coastal aquifer systems were generated in sediment-filled columns by injecting freshwater and seawater periodically. Changes in pore water chemistry and sediment properties were monitored over a period of one year. It has been observed that periodic injections of freshwater (freshening) and seawater (salinization) caused significant changes in the pore water chemistry, mainly due to sediment-water interactions. In addition to seawater-freshwater mixing, geochemical processes such as ion-exchange, mineral precipitation/dissolution, and adsorption/desorption of elements have been identified to control the pore water chemistry. Trace elements, including barium, boron, bromide, lithium, and strontium, have been identified as effective tracers for monitoring the saltwater intrusion. Further, the changes in pore water chemistry are found to be interlinked with the changes in aquifer properties. It is observed that with the increase in the number of salinization cycles, the effectiveness of the freshening process to bring back the original aquifer pore water chemistry diminishes, and the impact of salinization lasts longer. At the end of the experiment, changes in the porosity and permeability of the sediments have been observed. Such changes in the aquifer properties may affect the specific yield and storativity of the aquifer.

No widespread signature of the COVID-19 quarantine period on water quality across a spectrum of coastal systems in the United States of America

During the recent COVID-19 related quarantine period, anecdotal evidence emerged pointing to a rapid, sharp improvement in water quality in some localities. Here we present results from an analysis of the impacts of the COVID-19 quarantine period using two long-term coastal water quality datasets. These datasets rely on sampling that operates at appropriate timescales to quantify the influence of reduced human activity on coastal water quality and span coastal ecosystems ranging from low human influence to highly urbanized systems. We tested two hypotheses: 1) reduced tourism during the COVID-19 quarantine period would lead to improved coastal water quality, and 2) water quality improvements would scale to the level of human influence, meaning that highly urbanized or tourist-centric watersheds would see greater improvement than more rural watersheds. A localized reduction in fecal indicator bacteria was observed in four highly impacted regions of the Texas (USA) coast, but this pattern was not widespread. In less impacted regions, the signature of natural, decadal environmental variability (e.g., dissolved oxygen and turbidity) overwhelmed any potential signature of reduced human activity. Results from this study add to the growing body of literature on the environmental impacts of the COVID-19 quarantine period, and when considered with existing literature, emphasize that coastal water quality improvements appear to be ephemeral and reserved for the most severely affected (by human activity) systems. Furthermore, results show the importance of assessing COVID-19 signatures against long-term, decadal datasets that adequately reveal a system's natural variation.

Sustainable Tourism Development in Sungai Apit District Riau Province: Mangrove Ecotourism Factors

One of the efforts to overcome the problem of environmental damage in the mangrove forest ecosystem is the management of mangrove ecotourism. The concept of mangrove ecotourism is a responsible trip to mangrove forest areas for mangrove forest conservation efforts and improving community welfare. This study aims to examine sustainable tourism development in Sungai Apit District Riau Province: mangrove ecotourism factors. The method used in this research is a survey method, which was determined at 4 (four) research locations, namely Mengkapan Village (Station I), Sungai Kayu Ara Village (Station II), Kayu Ara Permai Village (Station III) and Tanjung Kuras Village (Station IV). Each research station consists of three sampling points for measuring the quality of coastal waters. It is obtained an overview of environmental factors that support the growth of mangrove forests. Research activities have been carried out in April-November 2020. The results showed that the mangrove forest ecosystem in the Sungai Apit District Suitable (S2) to be developed as a mangrove ecotourism area with an average IKW value of Station I was 75.39%; Station II of 76.71%; Station III is 78.82% and Station IV is 76.32%. The potential and attractiveness of mangrove ecotourism in Sungai Apit District has been developed by the Siak Regency government. The strategy for developing mangrove ecotourism in Sungai Apit District based on SWOT analysis and interviews is to prioritize the W-O strategy which consists of: 1) Increasing the participation of stakeholders in the management of mangrove ecotourism; 2). Promote effective ecotourism promotion, information and market activities; 3) Improve coordination between stakeholders properly and 4) Improve the quality of human resources through training and education activities.

Preliminary assessment of marine debris pollution and coastal water quality on some beaches in Thanh Hoa province, Vietnam

Marine debris assessment gives information about their quantity, type, and composition, which provides data to help with their management and control. The authors conducted two surveys at three beaches at Sam Son, Hai Tien, Hai Hoa) in Thanh Hoa province in March 2020 and July 2020, respectively, during an inactive and active tourism period. A total of 3,803 waste units were collected for assessment, of which plastic waste accounts for more than 98%. The density of marine debris at the idle time of tourism ranged from 0.25–1.21 items/m2. But the active tourist season recorded from 0.52–1.4 items/m2. According to the Clean Coast Index (CCI), the cleanliness of beaches was grade from average clean (i.e., Hai Tien) to filthy (i.e., Hai Hoa). The plastic debris present at these beaches was mainly porous waste derived from fishing boats and food preservation foam boxes. The results also showed that the marine debris was composed of 77% polystyrene (PS), 17% polypropylene (PP) and 6% high-density polyethylene (HDPE). The water parameters were lower than the critical values during the study period according to the QCVN 10-MT:2015/BTNMT for both periods, which indicated the coastal water quality was still suitable for recreational activities.

Discrete Global Grid Systems as scalable geospatial frameworks for characterizing coastal environments

Data portals and services have increased coastal water quality data availability and accessibility. However, tools to process this data are limited – geospatial frameworks at the land-sea interface are either adapted from open-water frameworks or extended from watershed frameworks. This study explores use of a geospatial framework based on hexagons from a Discrete Global Grid System (DGGS) in a coastal area. Two DGGS implementations are explored, dggridR and H3. The geospatial frameworks are compared based on their ability to aggregate data to scales from existing frameworks, integrate data across frameworks, and connect flows across the land-sea interface. dggridR was simpler with more flexibility to match scales and use smaller units. H3 was more performant, identifying neighbors and moving between scales more efficiently. Point, line and grid data were aggregated to H3 units to test the implementation's ability to model and visualize coastal data. H3 performed these additional tasks well.

U.S. beach water quality monitoring

Coastal water quality is an important factor influencing public health and the quality of our nation’s beaches. In recent years, poor water quality has resulted in increased numbers of beach closures and corresponding negative impacts on tourism. This paper addresses some of the issues surrounding the management challenge of coastal water quality, in particular, beach water quality monitoring. For this effort, data on beach water quality monitoring activities conducted by states were assessed and synthesized. In total, 29 states were surveyed: 16 reported information for seawater; six reported for freshwater only; eight reported for both seawater and freshwater. Thresholds for advisories and closure vary nationally; however, all 29 states have established an online presence for their monitoring programs and display advisories and closures in real time, most often on spatial information (GIS) portals. Challenges in monitoring, prediction, and communication are assessed and discussed. Based on this assessment, the committee offers the following recommendations, as detailed in the text: • Standardization of water quality data and the distribution medium; • Enhanced public access to water quality monitoring data; • Consistent thresholds for swim advisories; • Water quality regulation reviews with stakeholder participation; • Enhanced predictive models incorporating rapid testing results; • Holistic water quality monitoring that includes indicators beyond fecal indicator bacteria; • Managing contaminants of emerging concern through identification, monitoring and control; and • Funding for water quality monitoring and reporting -- from federal, state, and local governments.

Mapping Kuwait bathymetry using passive multispectral remote sensing

Mapping bathymetry is essential for many fields, including science, engineering, and the military, among others. Bathymetry is extremely important in the scientific field because it is linked to many physical and environmental issues such as coastal erosion, sea-level rise, and water quality. Traditionally, conventional methods, such as pre-measured cable passage, were used to estimate depths. Lately, echo-sounder assessments were used on hydrograph ships. This method is effective, but it is very costly in both economic and time terms. Remote sensing technology provides modern methods for mapping bathymetry, such as the use of active and passive remote sensing. Many satellite sensors cover multispectral bands. Some are commercial, such as IKONOS and WorldView, while others are freely available, such as Landsat 8 and Sentinel-2. In this study, Landsat 8 (15 meters spatial resolution) was used to estimate the depths of the waters of Kuwait, an Arabian Gulf country located on the Northwestern side of the gulf. Ground truthing points (GTPs) were used to build a bathymetric model of Kuwaiti territorial water (KTW) using the ratio transform algorithm (RTA) applied on Landsat 8 data. The results showed a good ability of Landsat 8 and RTA to estimate the depths of Kuwait’s waters, where the relationship between the derived model from Landsat 8 and the GTPs was positive (r2 = 0.9634). Meanwhile, the accuracy of the derived bathymetric model was evaluated by computing the Root Mean Square Error (RMSE = ± 1.66 meters) and Mean Absolute Error (MAE ± = 1.29).

A quarter-century of nutrient load reduction leads to halving river nutrient fluxes and increasing nutrient limitation in coastal waters of central Japan.

Nutrient load reduction is widely used to improve coastal water quality, but it can lead to oligotrophication. This paper evaluates the current status of river water origin and the water recharge system based on isotope values and dissolved compositions recorded in 2018, and it also assesses the impact of nutrient load reduction efforts on river nutrient fluxes and coastal water quality using 25years of monitoring data. This study focuses on the coast of Toyama Bay as a model area because (1) up to 20% of terrestrially derived nutrient support the growth of coastal primary productivity, and (2) the adjacent land is a typical city in a population-dense area (~ 500 persons/km2), a demographic characteristic that exists in 88% of Japan's total land area and 96% of the total length of the country's coastline. Since the government adopted new wastewater treatment systems in 1993, river nutrient supplies in the study area have been halved, while the total river flow and annual precipitation have remained almost unchanged. The reduction in riverine nutrient supply has increased phosphorus deficiencies in the coastal waters. Most notably, the decline in nutrient concentrations in coastal surface waters and the enlarged nutrient-restricted areas are facing most parts of Japan, suggesting a resulting 25-50% decrease in CO2 uptake by primary production. This study is in agreement with previous studies from various countries in emphasizing the importance of setting appropriate nutrient-management goals for maintaining a sustainable marine environment. This paper recommends the need to accumulate various case studies of different areas and to share in a timely manner scientific evidence on a regional and global scale.

A baseline study of spatial variability of bacteria (total coliform, E. coli, and Enterococcus spp.) as biomarkers of pollution in ten tropical Atlantic beaches: concern for environmental and public health.

Coastal water quality in urban cities is increasingly impacted by human activities such as agricultural runoff, sewage discharges, and poor sanitation. However, environmental factors controlling bacteria abundance remain poorly understood. The study employed multiple indicators to assess ten beach water qualities in Ghana during minor wet seasons. Environmental parameters (e.g. temperature, electrical conductivity, total dissolved solids) were measured in situ using the Horiba multiple parameter probe. Surface water samples were collected to measure total suspended solids, nutrients, and chlorophyll-a via standard methods and bacteria determination through membrane filtration. Environmental parameters measured showed no significant variation for the sample period. However, bacteria loads differ significantly (p = 0.024) among the beaches and influenced significantly by nitrate (55.3%, p = 0.02) and total dissolved solids (17.1%, p = 0.017). The baseline study detected an increased amount of total coliforms and faecal indicator bacteria (Escherichia coli and Enterococcus spp.) in beach waters along the coast of Ghana, suggesting faecal contamination, which can pose health risks. The mean ± standard deviations of bacteria loads in beach water are total coliforms (4.06 × 103 ± 4.16 × 103 CFU/100 mL), E. coli (7.06 × 102 ± 1.72 × 103 CFU/100 mL), and Enterococcus spp. (6.15 × 102 ± 1.75 × 103 CFU/100 mL). Evidence of pollution calls for public awareness to prevent ecological and health-related risks and policy reforms to control coastal water pollution. Future research should focus on identifying the sources of contamination in the tropical Atlantic region.

Recreational users' perceptions of coastal water quality in Rhode Island (USA): Implications for policy development and management

Stakeholders' understanding of water quality influences how they approach water policy problems and their support for potential solutions. This study explores how resource policy in the United States accounts for different water quality meanings held by recreational users. In-person surveys were conducted along the shoreline in Rhode Island (USA) to examine how recreational users make sense of coastal water quality. Findings indicate that recreational users' understanding of water quality is constructed from an array of environmental conditions (e.g., chl a, phosphates) and attitudinal factors (e.g., perceived problems associated with sewage, algae, or trash), and the meanings ascribed to water quality extend beyond the biophysical indicators typically employed by water resource managers. Potential management strategies based on these findings include expanding current definitions of water quality and monitoring a broader suite of factors, conducting research that captures nuanced meanings of water quality held by different users, and developing outreach programs that clarify the potential impacts of water quality components on human health and well-being.

Sea water quality monitoring using remote sensing techniques: a case study in Tangier-Ksar Sghir coastline.

Water quality is an extremely important factor as it affects the ecological balance of ecosystems and the development of the social and economic wellbeing of the countries bordering it. Remote sensing multiconcept helps to understand the natural environment, managing water resources and assessing water pollution on local and regional levels. Landsat 8 data were used to monitor coastal water quality in the region of Tangier-Ksar Sghir. The main purpose of the current study is to establish a mathematical relationship between the amount of light emitted from the water bodies and the measured water parameters. The results permit to create a spatial distribution maps for the water quality parameters. The present work study three water parameters: total suspended solids (TSS), dissolved oxygen (DO), and total dissolved sediments (TDS). Thirty-four sampling points were used to represent water parameters measurements along the coastline. The 75% of the in situ measurements were used to build the statistical models by using the spectral characteristics obtained from the sensors, while the remaining 25% were used for testing the accuracy of the developed equations. For the correlation analysis and the regression development, the Statistical Package of the Social Sciences (SPSS) software was used. The final results of the statistical analysis showed a high correlation between the calculated data and the observed ones with R2 ˃ 0.713 and p value ˂ 0.001. The obtained values showed a high accuracy as well (RMSE ranging between 0.23 and 0.69 and SEE ranging between 0.01 and 0.47). SNAP software and Qgis were used to do the image processing and to create the spatial distribution maps for the water parameters in the coastline of Tangier-Ksar Sghir region.

Biodiversity of Upwelling Coastal Systems of the Southern Caribbean Sea Adjacent to Guajira Peninsula

This paper describes the unique natural communities and biodiversity of the upwelling coastal system along the Guajira peninsula in the southern Caribbean Sea. The Guajira peninsula has a small human population with limited infrastructure and limited opportunities for coastal research, yet its coastal upwelling system is unique in the Tropical Western Atlantic region. This report includes both field observations along with a review of literature on the biodiversity of coastal eastern Guajira. In addition, it identifies missing information on the coastal system that is key to its management and conservation. Mangrove wetlands along with submerged aquatic vegetation (SAV) communities in a combination of consolidated and unconsolidated shorelines (e.g., rocky shores, cliffs, and beaches) form unique habitats in eastern Guajira. The diversity of these habitats is illustrated with the Bahia Hondita marine lagoon, where critical nursery habitat for several commercial valuable and endangered fisheries species, including sharks and sea turtles, is observed. Less information is available on more cryptic fauna, invertebrates, and coastal plankton species. Several anthropogenic factors are threatening species diversity in coastal Guajira, including overgrazing, mining, and target-species overfishing. Additional threats, such as extreme weather events (e.g., storms and droughts) as well as changes in coastal water quality, are also impacting species. The protection of the Guajira’s biodiversity would depend on local communities’ governance and empowerment as well as law enforcement for mining and agriculture operations. Management plans can include reducing land-based sources of pollution and building coastal resilience for climate change.

The role of soils in regulation of freshwater and coastal water quality.

Water quality regulation is an important ecosystem service function of soil. In this study, the mechanism by which soil regulates water quality was reviewed, and the effects of soil management on water quality were explored. A scientometrics analysis was also conducted to explore the research fields and hotspots of water quality regulation of soil in the past 5 years. This review found that the pollutants entering the soil can be mitigated by precipitation, adsorption and desorption, ion exchange, redox and metabolic decomposition. As an optimal substrate, soil in constructed wetlands has perfect performance in the adsorption and passivation of pollutants such as nitrogen, phosphorus and heavy metals in water, and degradation of pesticides and emerging contaminants. Mangrove wetlands play an important role in coastal zone protection and coastal water quality restoration. However, the excessive application of agricultural chemicals causes soil overload, which leads to the occurrence of agricultural non-point source pollution. Under the dual pressures of climate change and food insecurity in the future, developing environmentally friendly and economically feasible sustainable soil management measures is crucial for maintaining the water purification function of soil by relying on the accurate quantification of soil function based on big data and modelling. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Integrated analyses of fecal indicator bacteria, microbial source tracking markers, and pathogens for Southeast Asian beach water quality assessment

The degradation of coastal water quality from fecal pollution poses a health risk to visitors at recreational beaches. Fecal indicator bacteria (FIB) are a proxy for fecal pollution; however the accuracy of their representation of fecal pollution health risks at recreational beaches impacted by non-point sources is disputed due to non-human derivation. This study aimed to investigate the relationship between FIB and a range of culturable and molecular-based microbial source tracking (MST) markers and pathogenic bacteria, and physicochemical parameters and rainfall. Forty-two marine water samples were collected from seven sampling stations during six events at two tourist beaches in Thailand. Both beaches were contaminated with fecal pollution as evident from the GenBac3 marker at 88%–100% detection and up to 8.71 log10 copies/100 mL. The human-specific MST marker human polyomaviruses JC and BK (HPyVs) at up to 4.33 log10 copies/100 mL with 92%–94% positive detection indicated that human sewage was likely the main contamination source. CrAssphage showed lower frequencies and concentrations; its correlations with the FIB group (i.e., total coliforms, fecal coliforms, and enterococci) and GenBac3 diminished its use as a human-specific MST marker for coastal water. Human-specific culturable AIM06 and SR14 bacteriophages and general fecal indicator coliphages also showed less sensitivity than the human-specific molecular assays. The applicability of the GenBac3 endpoint PCR assay as a lower-cost prescreening step prior to the GenBac3 qPCR assay was supported by its 100% positive predictive value, but its limited negative predictive values required subsequent qPCR confirmation. Human enteric adenovirus and Vibrio cholerae were not found in any of the samples. The HPyVs related to Vibrio parahaemolyticus, Vibrio vulnificus, and 5-d rainfall records, all of which were more prevalent and concentrated during the wet season. More monitoring is therefore recommended during wet periods. Temporal differences but no spatial differences were observed, suggesting the need for a sentinel site at each beach for routine monitoring. The exceedance of FIB water quality standards did not indicate increased prevalence or concentrations of the HPyVs or Vibrio spp. pathogen group, so the utility of FIB as an indicator of health risks at tropical beaches maybe challenged. Accurate assessment of fecal pollution by incorporating MST markers could lead to developing a more effective water quality monitoring plan to better protect human health risks in tropical recreational beaches.

Impact of lockdown on the environmental quality along the Indian coast and a tropical estuary

The COVID-19 lockdown significantly improved the global environmental quality by restricted anthropogenic activities. We aimed to understand the response of Indian coastal environmental quality and an estuarine (Zuari estuary, central west coast of India) water quality to the lockdown using satellite-derived data sets and in-situ measurements, respectively. The in-situ study was carried out for two weeks (during August and September 2020) to measure chlorophyll-a and macro-nutrients. Recent 5-years (2015–2019; March–August) data sets of aerosol optical depth (AOD), rainfall, air temperature, sea surface temperature (SST), chlorophyll-a, particulate inorganic carbon (PIC) and particulate organic carbon (POC) were compared with lockdown period (2020). The AOD was decreased during the lockdown period (23 ± 11%) as compared with recent 5-years shows the significant impact of lockdown on industrial, transport and urbanization activities. The water quality parameters and chlorophyll-a biomass have remained similar to the past data sets, indicating the insignificant effect of lockdown on these parameters. The results of the case study were compared with the previous reports, which showed a decrease in the concentration of nitrate, phosphate and silicate and comparable concentration of chlorophyll-a. Recent studies show significant impacts of lockdown on the atmospheric parameters and water quality parameters, however the present study did not observe any significant variations in the in-situ and satellite derived data sets of water quality and chlorophyll-a. We have discussed the possible reasons underlying in the less/undetectable response of the chlorophyll-a and water quality of the Indian coastal waters and estuaries during the lockdown.