9 research outputs found
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Assessment of Sargassum spp. management strategies in southeast Florida
This study evaluated the economic viability of Sargassum management strategies in southeast Florida. Semi-structured interviews were conducted with key informants, beach managers and potential users. To compare the strategies, a cost and market analysis was conducted to assess the value of Sargassum compost relative to other compost products available in the market. The findings indicate that composting Sargassum is an economically viable option and suggests the potential for recouping some of the costs associated with beach cleaning through the sale of compost. Furthermore, the utilization of Sargassum compost could offer a cost-effective alternative as a soil amendment, especially in the face of rising fertilizer costs. However, it is crucial to address concerns regarding compost quality due to contaminants such as plastics and arsenic before implementing a composting operation. This aspect necessitates thorough investigation and remediation to ensure that the resulting compost meets quality standards and is free from potentially harmful contaminants
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Cost Estimates for Producing Sargassum spp. Compost FE1128, 2/2023
This publication examines the costs that the city of Ft. Lauderdale incurred to establish a Sargassum compost facility. The objective of this analysis is to provide insights to other municipalities and small businesses around south Florida who are considering starting similar composting operations with the expectation that Sargassum composting will provide them with more space in their landfills while maintaining their beaches’ tourist appeal. The data for this analysis were collected through interviews in 2021 with several individuals in municipalities and small businesses, which use a wide range of Sargassum management strategies. We found that Ft. Lauderdale saves at least $326,000 annually by operating its own composting facility
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Cost Estimates for Producing Sargassum spp. Compost
This publication examines the costs that the city of Ft. Lauderdale incurred to establish a Sargassum compost facility. The objective of this analysis is to provide insights to other municipalities and small businesses around south Florida who are considering starting similar composting operations with the expectation that Sargassum composting will provide them with more space in their landfills while maintaining their beaches’ tourist appeal. The data for this analysis were collected through interviews in 2021 with several individuals in municipalities and small businesses, which use a wide range of Sargassum management strategies. We found that Ft. Lauderdale saves at least $326,000 annually by operating its own composting facility
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Fecal indicator bacteria levels at a marine beach before, during, and after the COVID-19 shutdown period and associations with decomposing seaweed and human presence
Studies are limited that evaluate seaweed as a source of bacteria to beach waters. The objective of the current study was to evaluate whether seaweed, along with humans and other animals, could be the cause of beach advisories due to elevated levels of enterococci. The monitoring period occurred a year prior to and through the COVID-19 beach shutdown period, which provided a unique opportunity to evaluate bacteria levels during prolonged periods without recreational activity. Samples of water, sediment, and seaweed were measured for enterococci by culture and qPCR, in addition to microbial source tracking by qPCR of fecal bacteria markers from humans, dogs, and birds. During periods of elevated enterococci levels in water, these analyses were supplemented by chemical source tracking of human-associated excretion markers (caffeine, sucralose, acetaminophen, ibuprofen, and naproxen). Results show that enterococci with elevated levels of human fecal markers persist in the seaweed and sediment and are the likely contributor to elevated levels of bacteria to the nearshore waters. During the shutdown period the elevated levels of enterococci in the sediment were isolated to the seaweed stranding areas. During periods when the beaches were open, enterococci were distributed more uniformly in sediment across the supratidal and intertidal zones. It is hypothesized from this study that human foot traffic may be responsible for the spread of enterococci throughout these areas. Overall, this study found high levels of enterococci in decomposing seaweed supporting the hypothesis that decomposing seaweed provides an additional substrate for enterococci to grow.
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•Elevated levels of enterococci were associated with decomposition of seaweed.•Human-specific Bacteroides marker (HF183) was higher in water, sediment and seaweed.•During the shutdown, high enterococci in sediment was confined to integration zone•When beach was open, enterococci was distributed throughout sediment zones.•Spread of sediment enterococci may be due to human foot traffic through seaweed zone
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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.
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•Enterococci bacteria were evaluated for trends over 20 years.•Levels were observed to increase systematically across 18 beaches.•The increase was observed during the last five years.•The highest correlation was with Sargassum volumes.•Significant correlations were observed with sea level, population, and air temperature
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Assessing Quality and Beneficial Uses of Sargassum Compost
•• Sargassum composts successfully, but should be used in low human-contact areas.•• Arsenic concentrations met U.S. EPA standards but not SCTLs for residential use.•• Compost met fecal coliform U.S. EPA standards for large-scale outdoor piles only.•• Radish plants will grow in Sargassum compost, but arsenic detected in vegetable.•• Beneficial uses recommended for fill, ornamental plants, and mangrove restoration.
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
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Microbial Communities in the Water Surface Microlayer and Associations with Microbes in Aerosols, Beach Sand, and Bulk Water
The water surface microlayer (SML) serves as a boundary through which microbes can be exchanged. To evaluate exchanges of microbes, this study compared microbial communities within different reservoirs, with an emphasis on the water SML and aerosols. Additionally, the microbial communities during a sewage spill and perigean tides were evaluated and the results were compared to times without these events. Results show that during perigean tides and during the sewage spill, levels of culturable bacteria were highest and showed an increase via sequencing in potential pathogenic bacteria (Corynebacterium and Vibrio, which increased from 3.5%-1800% depending on sample type). In the aerosol samples, Corynebacterium (average of 2.0%), Vibrio (1.6%), and Staphylococcus (10%), were the most abundant genera. Aerosolization factors, which were used to examine the transfer of the microbes, were high for these three genera. Measurements of general marine bacteria (GMB) by culture showed a weak but significant correlation between culturable GMB in aerosol samples versus in water and in SML. More research is needed to evaluate the exchange of pathogens between the SML and air, given the increase in potentially pathogenic microbes within the SML during rare events and evidence that suggests that microbes maintain viability during transfers across reservoirs
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Sea Level Rise Exacerbates Enterococci Pathways to Coastal Waters
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Enterococci pathways to coastal waters and implications of sea level rise
•Groundwater is influenced by sea level rise (SLR) at study site.•Higher levels of enterococci associated with fresher waters and rain events.•Enterococci source to fresh water includes urban sediments and runoff.•Primary pathway to study site via stormwater infrastructure.•Additional pathways include groundwater discharge with hydraulics influenced by SLR.
Highly urban coastal communities in low lying areas and with high water tables are vulnerable to sea-level rise and to corresponding increases in coastal groundwater levels. Stormwater conveyance systems are under increased risk. Rising groundwater levels affect the hydraulics of the stormwater system thereby increasing contaminant transport, for example the fecal indicator bacteria enterococci, to coastal waters. This study offers a unique opportunity to evaluate the impacts of increased contaminant transport on marine coastal environments. Here we assessed historic and recent coastal water quality, stormwater sampling data, groundwater monitoring and tidal elevations near the coastline, in the context of altered hydraulics within the system. Two pathways of enterococci to marine waters were identified. Direct discharge of contaminated stormwater runoff via the stormwater outfalls and tidally driven contaminated groundwater discharge. As sea level continues to rise, we hypothesize that a diminished unsaturated zone coupled with altered hydraulic conditions at the coastal groundwater zone will facilitate the transport of enterococci from urban sediments to the study site (Park View Waterway in Miami Beach, FL USA). We recommend improvements to the stormwater conveyance system, and maintenance of the sanitary sewer system to mitigate these impacts and minimize transport of enterococci, and other stormwater pollutants to coastal waters. The results of this study can be useful to interpret high enterococci levels in low lying coastal areas where groundwater is influenced by rising sea water levels.
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