Sargassum inundation events are increasing in frequency and intensity in the Caribbean, posing challenges for coastal communities, the blue economy, and ecosystem health. Aquatic plants are known to accumulate chemicals from the surrounding water, yet little is known about the presence of chemical contaminants in Sargassum. This project will assess contaminants in Sargassum to support coastal resilience and conservation efforts by informing coastal managers and communities of potential risks to aid monitoring and response strategies.
Why We Care
Large blooms of floating Sargassum seaweed are becoming more common in the Caribbean and off the Florida coast. Sargassum inundation events — when the seaweed accumulates along coastlines — have also increased in frequency and intensity, creating new challenges for coastal communities, ecosystems, and the blue economy.
These inundation events are known to impact tourism and local livelihoods, but they also have the potential to transport chemical contaminants to the shore, which can adversely affect human health and the coastal environment. The difficulty of removing Sargassum accumulated on beaches can also result in prolonged exposure to contaminants carried by the seaweed.
As communities and managers develop procedures for Sargassum removal (e.g., transport and disposal at landfills) and pilot alternative uses for Sargassum (e.g., repurposing for human or animal products), it is imperative to understand the impact that contaminants carried by Sargassum may have on human health and ecological sustainability.
What We Are Doing
Since 2021, NCCOS researchers have collected Sargassum from coastal and offshore locations along Florida’s southeastern coast, Puerto Rico’s southwest coast, St. Thomas, and St. Croix to evaluate potential chemical contamination associated with Sargassum inundation events. These efforts are generating foundational information to better understand how Sargassum interacts with coastal environments and whether it may serve as a vector for contaminant transport and a source of local contamination.
In collaboration with local partners, including the University of Puerto Rico, Jobos Bay NERR, Bioimpact, Inc. (USVI), Florida DEP, and Nova Southeastern University, we have collected Sargassum from approximately 30 sites. The samples are being analyzed for a suite of trace metals (silver, aluminum, arsenic, barium, beryllium, cadmium, cobalt, chromium, copper, iron, mercury, lithium, manganese, nickel, lead, antimony, selenium, tin, titanium, and zinc), and a suite of legacy organic contaminants (DDTs, PAHs, PBDEs, PCBs, and various pesticides). Ultimately, this project will complement other lines of research conducted by NOAA and its partners, and increase our understanding of these organisms and their impacts to local communities in support of response and restoration efforts.
What We Found
Our chemical analyses showed that a subset of persistent organic pollutants and trace metals were present in Sargassum samples, with polychlorinated biphenyls (PCB’s) detected most frequently among organic contaminants. Sites with the highest number of detected organic compounds also showed the highest concentrations of inorganic elements. Major elements such as aluminum and iron were most abundant, while mercury and several other trace metals were present at low concentrations.
Benefits of Our Work
Sargassum inundation events can have profound negative effects on regional economies, tourism, and human and ecosystem health. Contaminants, an important piece of the puzzle, are presently understudied. This study will provide data and information on the extent of exposure via inundation events and evaluate the importance of incorporating contaminants as a priority area of concern in ongoing assessments.
The team will continue evaluating contaminant patterns across the Caribbean’s coastal and offshore locations and integrate findings with complementary regional Sargassum research efforts. NCCOS’ Monitoring and Assessment and Ecotoxicology Branches plan to publish the research findings in 2026 and 2027.