Inland and Coastal Bathing Water Quality in the Last Decade (2011–2020): Croatia vs. Region vs. EU

Europe is one of the leading tourist destinations where tourism is one of the key economic sectors. The quality of bathing waters is a very important factor when choosing a vacation destination. Croatia recognized this early and was one of the first Mediterranean countries to start systematic monitoring of bathing waters. On the other hand, monitoring of inland bathing waters is relatively new and includes a much smaller number of sites (41) compared to coastal waters (894). The aim of this paper was to summarize and analyze the water quality of inland and coastal bathing sites of Croatia, closer regions (non-EU Member States) and in the EU for the last decade. The share of excellent water quality in EU Member States increased by 10.1% and 6.6% for inland and coastal waters, respectively (2011–2020). Germany recorded the highest proportion of excellent water quality for inland waters (92.2%) and Cyprus for coastal waters (99.3%). Looking at the 10-year average of the proportion of bathing waters with excellent quality, the proportion of coastal bathing sites exceeds that of inland waters by 7.1%. It is clear that additional efforts should be made to improve the management and monitoring of inland waters.

Environmental and anthropogenic factors affecting coastal bathing water quality

Coastal bathing water, as a common good, is an economic resource of public health interest. Predictive models of coastal bathing water contamination are needed for timely prevention of pollution, warning of bathers, and activation of municipal services and utilities in case of contingencies, as well as institutional mechanism designs for common good management purposes. The goal of this research is to identify the variables that would improve predictive models of coastal bathing water bacterial contamination. The microbiological quality of coastal bathing water is affected by many variables. This research is an analysis of the following determinants: precipitation amount, seawater temperature and salinity, as well as few indicators of anthropogenic pressure on the environment such as registered population, registered tourist overnight stays and the amount of generated municipal waste, all possibly directly or indirectly affecting the bathing water quality in 17 coastal municipalities in the Primorje-Gorski Kotar County. The analysis showed that rainfall, as an instrumental confounder variable, influences salinity and seawater temperature by increasing groundwater discharge and bringing contamination i.e. increasing enterococci and Escherichia coli concentrations in coastal bathing water. Population as the conjectured independent variable, representing the anthropogenic cause of pollution, was once again falsified as a statistically significant determinant. For further research, longer-term sampling (preferably year-round) at micro-locations of comparable hydrogeological characteristics is recommended.

Staphylococcus aureus—An Additional Parameter of Bathing Water Quality for Crowded Urban Beaches

During the last years, the report of the occurrence of waterborne disease symptoms related to non-enteric pathogens has increased, without any record of higher levels of indicator bacteria (Escherichia coli and intestinal enterococci). Therefore, the use of current indicators is not always adequate when assessing the overall potential health risk and the inclusion of additional parameters needs to be examined. This paper reports on the incidence and levels of Staphylococcus aureus at 258 locations in Primorje-Gorski Kotar County (Croatia) recorded by official bathing water quality monitoring, as well as supplemental monitoring carried out at the two most frequented beaches in the City of Rijeka. The number of bathers was found to be the main factor affecting S. aureus levels (r = 0.321, p < 0.05). The share of S. aureus positive samples from the official monitoring was significantly lower, when compared to the share of samples from supplemental monitoring (2.2% and 36.3%, respectively; p < 0.01). Besides the number of bathers, one of the main reasons is likely the higher sampling frequency. No correlation was found between S. aureus levels and the indicator bacteria. The results indicate that the determination of S. aureus and increased sampling frequency is recommended for overcrowded beaches.

Remote sensing data driven bathing water quality assessment using sentinel-3

<span>In this paper we are investigating the possibility of usage of remote sensing satellite data, more precisely sentinel-3 OLCI and SLSTR data, for assessment of bathing water quality. In this research we used data driven approach and analysis of data in order to pinpoint aspects of remote sensing data that can be useful for bathing water quality assessment. For this purpose we collected satellite images for period from start of June till end of September of 2019 and results of in-situ measurement for the same period. Results of in-situ measurement were correlated with satellite images bands and analyzed. We propose a simple method for rapid assessment of possible deterioration of bathing water quality to be used by public health authorities for better planning of in situ measurements. Results of implementation of predictive models based on k-nearest neighbour (KNN) and decision tree (DT) are described.</span>

Quality of Croatian Inland Bathing Areas: Reference to The Region and EU

Introduction: The Republic of Croatia (HR) has significantly invested in monitoring the quality of inland bathing areas during the past 10 years. The aim of this paper was to analyze the results obtained during the 2014-2019 period and to compare them with the Region (non-European Union [EU] countries neighboring Croatia) and EU. Moreover, bathing water quality data at two bathing areas of Zagreb (lakes Jarun and Bundek) were processed in more detail.Methods: The quality of inland bathing areas in the HR is monitored in five rivers and five lakes in nine Croatian counties; 19 of the 35 monitored sites are located in Zagreb County. Escherichia coli (EC) was determined by EN ISO 9308-3: 1998, while intestinal enterococci (ENT) were defined by EN ISO 7899-2: 2000. Statistical processing of the results was performed using the Microsoft Excel Statistical Package (Redmond, USA) and Statistica 13.5. (Stat.Sof.Inc., Tulsa, USA); the significance level was set to p < 0.05.Results: During the study period, the worst Croatian inland water quality was recorded in 2019 (excellent quality for only 25.9% of the bathing areas), while the best quality was recorded in 2015 (excellent quality in 57.1%). On average (2014-2019), the share of bathing areas with excellent quality in Croatia was 46.3% (i.e., under the EU average of 85.3%); with no poor locations (EU average was nearly 2%). A significant positive correlation was found between fecal indicators (EC&ENT) and the amount of precipitation, while a negative correlation with water and air temperature in lakes.Conclusions: The quality of Croatian inland bathing areas is significantly lower than the European average, while EU water quality is improving. Regarding the countries bordering Croatia, Italy, Slovenia, and Hungary have achieved better results, while Montenegro, Serbia, and Bosnia and Herzegovina are still in the process of developing the monitoring of the bathing water quality.

Development of a New Predictive index (Bathing Water Quality Index, BWQI) Based on Escherichia coli Physiological States for Bathing Waters Monitoring

Bacterial pathogens in coastal aquatic ecosystems pose a potential public health hazard for bathing water use. The European Bathing Water Directive (2006/7/EC) currently relies on the culturability of fecal pollution bacterial indicators such as Escherichia coli, without considering dormant or quiescent (Viable But Not Culturable, VBNC) cells, whose possible resuscitation after bathers ingestion cannot be excluded. Standard methods are also time-consuming and therefore hardly meet early warning needs of marine monitoring. To solve this issue, a new index, the Bathing Water Quality Index (BWQI), has here been developed, allowing to identify the most favorable coastal zones for recreational use. The index was calculated by combining numerical simulations of living and dormant E. coli abundances and their residence times. To specifically set up the model with the different physiological states of the whole E. coli population, an ad hoc experiment based on the fluorescent antibody method was performed. The BWQI application to Santa Marinella bathing area highlights a potential risk for human health in the zone most frequented by bathers. This study provides a predictive tool to support preventive decisions of the competent authorities and to properly protect bathers’ health, stressing the need for improved methods for environmental monitoring.

Determination of Microbiological Pollution Level of Lake Van and Lake Erçek Situated within the Borders of Van Province

Objective: Lake Van is one of the most important recreation areas of the region. Investigation of microbiological pollution of Lake Van is very important for public health. The aim of this study is to assess the microbiological pollution and determine water quality of the lakes Van and Erçek situated within Van Province, which are used for swimming and recreation to protect both human and environmental health. For this purpose, the presence of fecal coliform, total coliform and enterococci were investigated in samples taken from 29 different points of the lakes. Method: Between June and September 2015, 232 water samples were taken from predefined 29 points, every two weeks, and sent to the Public Health Laboratory of Van Province in 300-500 mL sterile plastic bottles in accordance with Bathing Water Quality Regulation (76/160 / EU: add-on clause 5. Membrane filtration method was used to analyze the samples for coliform bacilli and enterococci. Mandatory values according to bathing water quality regulation were taken as 2000 cfu/100 ml,10000 cfu/100 ml and 1000 cfu/100 ml for fecal coliform, total coliform and enterococcus, respectively. Results: In 196 (84%) of 232 water samples collected, no bacterial contamination was found, while 36 (16%) samples were found contaminated with fecal coliform, total coliform and Enterococcus species. At least one or more specimens of poor quality water were detected in 17 of 29 sampled beaches. Conclusion: It was envisaged to take precautions by restricting the use of the places where microbiological pollution was detected. In addition, regular analyzes are important for public health.

COVID-19 Pandemic Consequences on Coastal Water Quality Using WST Sentinel-3 Data: Case of Tangier, Morocco

The west coast of Tangier, in northern Morocco, has been affected by industrial wastewater discharge that reaches the ocean through the Boukhalef river. Therefore, the Jbila and Sidikacem beaches near to the Boukhalef river mouth have been classified as polluted for many years. With the aim of determining the COVID-19 pandemic consequences on the Tangier coastal environment, a linear model using Sentinel 3 water surface temperature (WST) has been tested in several locations. Data from April 2019 and April 2020, before and during the COVID-19 pandemic related emergency status in Morocco, were compared. The results from April 2019 showed high WST values and consequently, the poorest water quality in the sites closest to the Boukhalef river mouth. On the other hand, the results from April 2020 showed normal WST values and high water quality in the same study area. These results illustrate the usefulness of Sentinel 3 WST for the estimation of bathing water quality on the west coast of Tangier. The study shows the positive impact of the COVID-19 pandemic consequences on the coastal environment quality in the study area and indicates the importance of decreasing the industrial discharge on the west coast of Tangier. The same methodology could be used in decision-making processes and to reduce cost, time and human resources for coastal monitoring systems. We demonstrate the potential of using the Sentinel 3 data for coastal waters monitoring, as well as the need for stricter controls of pollutant discharges into the world’s rivers.