Assessment of local and regional strategies to control bacteria levels at beaches with consideration of impacts from climate change

Spatio-Temporal Variation in the Exceedance of Enterococci in Lake Burley Griffin: An Analysis of 16 Years' Recreational Water Quality Monitoring Data

Recreational waterbodies with high levels of faecal indicator bacteria (FIB) pose health risks and are an ongoing challenge for urban-lake managers. Lake Burley Griffin (LBG) in the Australian Capital city of Canberra is a popular site for water-based recreation, but analyses of seasonal and long-term patterns in enterococci that exceed alert levels (>200 CFU per 100 mL, leading to site closures) are lacking. This study analysed enterococci concentrations from seven recreational sites from 2001-2021 to examine spatial and temporal patterns in exceedances during the swimming season (October-April), when exposure is highest. The enterococci concentrations varied significantly across sites and in the summer months. The frequency of the exceedances was higher in the 2009-2015 period than in the 2001-2005 and 2015-2021 periods. The odds of alert-level concentrations were greater in November, December, and February compared to October. The odds of exceedance were higher at the Weston Park East site (swimming beach) and lower at the Ferry Terminal and Weston Park West site compared to the East Basin site. This preliminary examination highlights the need for site-specific assessments of environmental and management-related factors that may impact the public health risks of using the lake, such as inflows, turbidity, and climatic conditions. The insights from this study confirm the need for targeted monitoring efforts during high-risk months and at specific sites. The study also advocates for implementing measures to minimise faecal pollution at its sources.

Assessing quality and beneficial uses of Sargassum compost

Sargassum spp. (specifically Sargassum fluitans and S. natans), one of the dominant forms of marine macroalgae (seaweed) found on the beaches of Florida, is washing up on the shores throughout the Caribbean in record quantities. Currently, a common management option is to haul and dispose of beached Sargassum in local landfills, potentially wasting a valuable renewable resource. The objective of this study was to determine whether composting represents a feasible alternative to managing Sargassum inundations through measurements and comparisons to eleven guidelines. Specifically, we assessed the characteristics of the compost [physical-chemical parameters (temperature, moisture content, pH, and conductivity), nutrient ratios (C:N), elemental composition, bacteria levels, and ability to sustain plant growth] in both small- and large scale experiments. Results show that although nutrient concentration ratios were not within the standards outlined by the U.S. Composting Council (USCC), the Sargassum compost was able to sustain the growth of radishes (Raphanus sativus L., var. Champion). Trace metal concentrations in the compost product were within five regulatory guidelines evaluated, except for arsenic (As) (6.64-26.5 mg/kg), which exceeded one of the five (the Florida Soil Cleanup Target Level for residential use). Bacteria levels were consistent with regulatory guidelines for compost produced in large-scale outdoor experiments but not for the small-scale set conducted in enclosed tumblers. Overall results support that Sargassum compost can be beneficially used for fill and some farming applications.

Trends in regional enterococci levels at marine beaches and correlations with environmental, global oceanic changes, community populations, and wastewater infrastructure

An increase in the number of advisories issued for recreational beaches across south Florida (due to the fecal indicator bacteria, enterococci) has been observed in recent years. To evaluate the possible reasons for this increase, we reviewed weekly monitoring data for 18 beaches in Miami-Dade County, Florida, for the years 2000-2019. Our objective was to evaluate this dataset for trends in enterococci levels and correlations with various factors that might have influenced enterococci levels at these beaches. For statistical analyses, we divided the 20-year period of record into 5-year increments (2000-2004, 2005-2009, 2010-2014, and 2015-2019). The Wilcoxon rank sum test was used to identify statistically significant differences between the geometric mean of different periods. When all 18 beaches were collectively considered, a significant increase (p = 0.03) in enterococci was observed during 2015-2019, compared to the prior 15-year period of record. To better understand the potential causes for this increase, correlations were evaluated with environmental parameters (rainfall, air temperature, and water temperature), global oceanic changes (sea level and Sargassum), community populations (county population estimates and beach visitation numbers), and wastewater infrastructure (sewage effluent flow rates to ocean outfalls and deep well injection). In relation to the enterococci geometric mean, the correlation with Sargassum was statistically significant at a 95% confidence interval (p = 0.035). Population (p = 0.078), air temperature (p = 0.092), and sea level (p = 0.098) were statistically significant at 90% confidence intervals. Rainfall, water temperature, beach visitation numbers, and sewage effluent flow rates via deep well injection had positive correlations but were not significant factors. Sewage effluent flow rates to ocean outfalls had a negative correlation.

Septic systems drive nutrient enrichment of groundwaters and eutrophication in the urbanized Indian River Lagoon, Florida

Effluent from septic systems can pollute groundwater and surface waters in coastal watersheds. These effects are unknown for the highly urbanized central Indian River Lagoon (CIRL), Florida, where septic systems represent > 50% of wastewater disposal. To better understand these impacts, water quality was assessed along both canals and a tributary that drain into the CIRL. Dissolved nutrient concentrations were higher near septic systems than in natural areas. δ¹⁵N values of groundwater (+7.2‰), surface water (+5.5‰), and macrophytes (+9.7‰) were within the range for wastewater (>+3‰), as were surface water concentrations of the artificial sweetener sucralose (100 to 1700 ng/L) and fecal indicator bacteria density. These results indicate that septic systems are promoting eutrophication in the CIRL by contributing nutrient pollution to surface water via groundwater. This study demonstrates the need to reduce reliance on septic systems in urbanized coastal communities to improve water quality and subsequently mitigate harmful algal blooms.

The emergency discharge of sewage to the Bay of Gdańsk as a source of bacterial enrichment in coastal air

The purpose of this research was to study the presence of potential pathogenic bacteria in the seawater and air in five coastal towns (Hel, Puck, Gdynia, Sopot, Gdańsk-Brzeźno) as well as the enrichment of bacteria from the seawater into the coastal air after an emergency discharge of sewage into the Bay of Gdańsk. A total of 594 samples of air and seawater were collected in the coastal zone between spring and summer (between 2014 and 2018). Air samples were collected using the impact method with a SAS Super ISO 100. The multivariate analysis, conducted using contingency tables, showed a statistically significant variation between the concentration of coliforms, psychrophilic and mesophilic bacteria in the seawater microlayer and air in 2018, after an emergency discharge of sewage into the Bay of Gdańsk, compared to 2014-2017. Moreover, we detected a marine aerosol enrichment in psychrophilic, mesophilic bacteria, coliforms and Escherichia coli. We also showed a statistically significant relationship between the total concentration of bacteria and humidity, air temperature, speed and wind direction. This increased concentration of bacteria in the seawater and coastal air, and the high factor of air enrichment with bacteria maybe associated with the emergency discharge of wastewater into the Bay of Gdańsk. Therefore, it is suggested that in the event of a malfunction of a sewage treatment plant, as well as after floods or sudden rainfall, the public should be informed about the sanitary and epidemiological status of the coastal waters and be recommended to limit their use of coastal leisure areas.

Occurrence and distribution of fecal indicators and pathogenic bacteria in seawater and Perna perna mussel in the Gulf of Annaba (Southern Mediterranean)

The identification of fecal contamination in coastal marine ecosystems is one of the main requirements for evaluation of potential risks to human health. The objective of this study was to investigate the occurrence and distribution of fecal indicators and pathogenic bacteria in seawaters and mussels collected monthly during a period of 1 year from four different sites in Northeastern Algeria (sites S1 to S4), through biochemical and molecular analyses. Our research is the first to use molecular analysis to unambiguously identify the potentially pathogenic bacteria present in Algerian Perna perna mussels. The obtained results revealed that the levels of fecal indicator bacteria (FIB) from both P. perna and seawater samples largely exceeded the permissible limits at S2 and S3. This is mainly related to their location close to industrial and coastal activity zones, which contain a mixture of urban, agricultural, and industrial pollutants. Besides, P. perna collected from all sites were severalfold more contaminated by FIB than seawater samples, primarily during the warm season of the study period. Biochemical and molecular analyses showed that isolated bacteria from both seawater and mussels were mainly potentially pathogenic species such as E. coli, Salmonella spp., Staphylococcus spp., Klebsiella spp., Pseudomonas spp., and Proteus spp.

Impact of wastewater infrastructure improvements on beach water fecal indicator bacteria levels in Monroe County, Florida

The effects of wastewater infrastructure construction on regional and local environments is unknown. This project evaluated the effects of such projects in Monroe County, Florida, an area that had undergone regional wastewater infrastructure improvements. We used fecal indicator bacteria (FIB) (fecal coliform and enterococci), as a proxy indicator of beach water quality for an 18-year period of record. At the highest level of aggregation, FIBs for all 17 beaches within the county were combined to evaluate trends on a yearly basis. At the lower level, yearly FIB trends were evaluated for each beach separately. FIB data on infrastructure project period (categorical variables: before, during, and after construction), and the influences of environmental conditions (quantitative variables of rainfall and temperature) were also evaluated. In the multiple regression models, enterococci and fecal coliform were significantly associated with rainfall (24 h, p < 0.0001) and water temperature (p < 0.0001) when only the quantitative variables were considered. When both categorical and quantitative variables were considered, project period was significant for enterococci (p < 0.0001) and fecal coliform (p < 0.0001), as was 24 h lagged rainfall. Overall, the most significant factors for both fecal coliform and enterococci were rainfall and project period. Considering all beaches, infrastructure projects seem to have the collective desired effects in the years following construction, as there were decreased FIBs measured at beach sites. Only through the aggregation of all projects and measurements at all beach sites could the decreases in FIB levels be observed. Local analysis is needed to explain anomalies from these general trends for specific beaches. This understanding of FIBs, their responses to environmental and project factors, and the need for aggregated and local site analysis can provide guidance to managers at other locations with similar issues of failing wastewater infrastructure and frequent FIB exceedances.

A novel method to evaluate chemical concentrations in muddy and sandy coastal regions before and after oil exposures

Oil spills can result in changes in chemical concentrations along coastlines. In prior work, these concentration changes were used to evaluate the date sediment was impacted by oil (i.e., oil exposure date). The objective of the current study was to build upon prior work by using the oil exposure date to compute oil spill chemical (OSC) concentrations in shoreline sediments before and after exposure. The new method was applied to OSC concentration measures collected during the Deepwater Horizon oil spill with an emphasis on evaluating before and after concentrations in muddy versus sandy regions. The procedure defined a grid that overlaid coastal areas with chemical concentration measurement locations. These grids were then aggregated into clusters to allow the assignment of chemical concentration measurements to a uniform coastal type. Performance of the method was illustrated for ten chemicals individually by cluster, and collectively for all chemicals and all clusters. Results show statistically significant differences between chemical concentrations before and after the calculated oil exposure dates (p < 0.04 for each of the 10 chemicals within the identified clusters). When aggregating all chemical measures collectively across all clusters, chemical concentrations were lower before oil exposure in comparison to after (p < 0.0001). Sandy coastlines exhibited lower chemical concentrations relative to muddy coastlines (p < 0.0001). Overall, the method developed is a useful first step for establishing baseline chemical concentrations and for assessing the impacts of disasters on sediment quality within different coastline types. Results may be also useful for assessing added ecological and human health risks associated with oil spills.

Untreated sewage contamination of beach sand from a leaking underground sewage system

Thirty people (mostly children) experienced an episode of skin rash days after a sand sifting beach operation at Porto Pim Beach in Faial, Azores during June 2019. An environmental and epidemiologic investigation was conducted to identify the cause of the outbreak of skin rash. The epidemiologic investigation found that some of the patients experiencing symptoms had never entered the beach water. During the pollution period and throughout the epidemiologic investigation, faecal indicator bacteria levels (94 CFU/100 ml for intestinal enterococci and 61 CFU/100 ml for Escherichia coli) in water remained under the limits used for the ninety-five percentile calculation of an Excellent coastal and transitional bathing water defined in the Portuguese Legislation (100 CFU/100 ml for intestinal enterococci and 250 CFU/100 ml for Escherichia coli). Thus sand contact was considered as a likely primary exposure route. Sand microbiological analysis for faecal indicator organisms and electron microscopy strongly suggested faecal contamination. Chemical analysis of the sand also revealed a concomitant substance compatible with sodium-hypochlorite as analysed using gas chromatography and subsequently confirmed by free chlorine analysis. Inspection of the toilet facilities and sewage disposal system revealed a leaking sewage distribution box. Collectively, results suggest that the cause of the outbreak was the leaking underground sewage distribution box that serviced the beach toilet facilities (40 m from beach), where sodium-hypochlorite was used for cleaning and disinfection. This sewage then contaminated the surficial sands to which beach goers were exposed. Chlorine being an irritant substance, was believed to have been the cause of the symptoms given the sudden presentation and dissipation of skin rashes. No gastro-intestinal illness was reported during this episode and during the following 30 days. Like water, beach sand should also be monitored for safety, especially for areas serviced by aged infrastructure.

Microbial Indicators of Fecal Pollution: Recent Progress and Challenges in Assessing Water Quality

PURPOSE OF REVIEW

Fecal contamination of water is a major public health concern. This review summarizes recent developments and advancements in water quality indicators of fecal contamination.

RECENT FINDINGS

This review highlights a number of trends. First, fecal indicators continue to be a valuable tool to assess water quality and have expanded to include indicators able to detect sources of fecal contamination in water. Second, molecular methods, particularly PCR-based methods, have advanced considerably in their selected targets and rigor, but have added complexity that may prohibit adoption for routine monitoring activities at this time. Third, risk modeling is beginning to better connect indicators and human health risks, with the accuracy of assessments currently tied to the timing and conditions where risk is measured. Research has advanced although challenges remain for the effective use of both traditional and alternative fecal indicators for risk characterization, source attribution and apportionment, and impact evaluation.

Proliferation of microalgae and enterococci in the Lake Okeechobee, St. Lucie, and Loxahatchee watersheds

This study is an analysis of relationships between microalgae (measured as chlorophyll a) and the fecal indicator bacteria enterococci. Microalgae blooms and enterococci exceedances have been occurring in Florida's recreational waterways for years. More recently, this has become a management concern as microalgae blooms have been attributed to potentially toxic cyanobacteria, and enterococci exceedances link to human infection/illness. Since both the microalgal blooms and bacterial exceedances occur in regions that receive managed freshwater releases from Lake Okeechobee, we hypothesized that both the blooms and exceedances are related to excess nutrients from the lake. Two experimental sites, on Lake Okeechobee and the St. Lucie River (downstream of the lake), plus a control site on the Loxahatchee River (which does not receive lake flow) were evaluated. The hypothesis was evaluated through three study components: 1) analysis of available long-term data from local environmental databases, 2) a year-long monthly sampling and analysis of chlorophyll a, enterococci, nutrients, and physical-chemical data, and 3) microcosm experiments with altered water/sediment conditions. Results support the hypothesis that excess nutrients play a role in both chlorophyll a and enterococci levels. For the St. Lucie River, analyses indicate that chlorophyll a correlated significantly with total Kjeldahl nitrogen (TKN) (R² = 0.30, p = 0.008) and the strongest model for enterococci included nitrate-nitrite, TKN, total phosphorus, orthophosphorus, and turbidity in our long-term analysis (n = 39, R² = 0.83, p ≤ 0.001). The microcosm results indicated that chlorophyll a and enterococci only persisted for 36 h in water from all sources, and that sediments from Lake Okeechobee may have allowed for sustained levels of chlorophyll a and enterococci levels. Overall similarities were observed in chlorophyll a and enterococci relationships with nutrient concentrations regardless of a Lake Okeechobee connection, as underscored by a study of flow out of the lake and downstream areas. This suggests that both nutrient-rich lake water and untreated surface water runoff contribute to microalgae blooms and enterococci exceedances in southeast Florida.

Impacts of a changing earth on microbial dynamics and human health risks in the continuum between beach water and sand

Although infectious disease risk from recreational exposure to waterborne pathogens has been an active area of research for decades, beach sand is a relatively unexplored habitat for the persistence of pathogens and fecal indicator bacteria (FIB). Beach sand, biofilms, and water all present unique advantages and challenges to pathogen introduction, growth, and persistence. These dynamics are further complicated by continuous exchange between sand and water habitats. Models of FIB and pathogen fate and transport at beaches can help predict the risk of infectious disease from beach use, but knowledge gaps with respect to decay and growth rates of pathogens in beach habitats impede robust modeling. Climatic variability adds further complexity to predictive modeling because extreme weather events, warming water, and sea level change may increase human exposure to waterborne pathogens and alter relationships between FIB and pathogens. In addition, population growth and urbanization will exacerbate contamination events and increase the potential for human exposure. The cumulative effects of anthropogenic changes will alter microbial population dynamics in beach habitats and the assumptions and relationships used in quantitative microbial risk assessment (QMRA) and process-based models. Here, we review our current understanding of microbial populations and transport dynamics across the sand-water continuum at beaches, how these dynamics can be modeled, and how global change factors (e.g., climate and land use) should be integrated into more accurate beachscape-based models.