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Centre for Resource Management and Environmental Studies

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Sargassum : Home

What’s the problem?
Since 2011, huge volumes of sargassum seaweed have been periodically transported by ocean currents to the Caribbean. These unprecedented and hard-to-predict influxes of sargassum, linked to ocean eutrophication and climate change, are having devastating impacts on Caribbean coastal socio-ecological systems.

Eastern Caribbean islands, on the frontline of these onslaughts, can receive up to 100 metric tonnes of sargassum per kilometre of beach per day during influx events. Tonnes of sargassum piled along shorelines and clogging waters up to 200 metres offshore are suffocating endangered marine mammals and turtles, and smothering coral reef, seagrass and mangrove communities. As sargassum decomposes it reduces oxygen and releases toxic gases causing fish-kills and high biodiversity losses. Furthermore, the aesthetic value of the Caribbean's iconic beaches and nearshore waters has been reduced. Livelihood and economic impacts on tourism, fisheries and public health, and hence on national economies are huge. 
Sargassum strandings, unless better managed, threaten the significant progress in the Eastern Caribbean towards conserving coastal biodiversity and critical ecosystems through marine protected areas (MPAs) and restoration efforts that sustain livelihoods. National and regional responses to date are largely unsustainable, with clean-ups and lost revenue costing Caribbean governments and the private sector hundreds of thousands of dollars. The need for increased capacity to cope, innovate and adapt is clear, and supported at the highest level. 

What has CERMES been up to?
UWI-CERMES has been at the forefront of communicating the latest sargassum science and innovations since the very first influx in 2011, giving invited presentations on sargassum at numerous regional and international events.  In partnership with GCFI and UNEP (through the CAR-SPAW-RAC), UWI-CERMES produced the first Sargassum Management Guide, that was subsequently used as the basis for a co-produced infographic poster. UWI has also hosted two Sargassum Symposia, in 2015 and 2018, and has established this website which provides a repository of initiatives taking place on Sargassum research and product development.  
Since 2017, CERMES has been working on Sargassum issues in the Eastern Caribbean under the CC4FISH project of the Food and Agriculture Organisation (FAO).  During stakeholder consultations, several Eastern Caribbean countries requested help with developing sargassum management plans, which prompted the development of a ‘sub-project’ under CC4FISH to address the emerging issue of sargassum.  Key outputs of this effort to date are:
  • Research into the factors underlying the sargassum influxes into the Caribbean and development of a numerical model to predict these.
  • The prototype development and release of the first four issues of the Eastern Caribbean Sub-regional Sargassum Outlook Bulletin to disseminate sargassum influx forecasts, implications for fisheries and tourism stakeholders, and information on new sargassum research and innovation.
  • Research into the effect of sargassum influxes on Eastern Caribbean  pelagic fisheries
  • Production of a best practice guide for fishers
  • Sargassum management plans for four participating Eastern Caribbean countries as extensions of existing fisheries management plans (on going)
  • A review and analysis of current and potential uses for sargassum as a commodity (on going)

What have we learned?
We know that floating pelagic sargassum seaweed, endemic to the North Atlantic, naturally accumulates in the Sargasso Sea supporting large, biodiverse marine communities. It is also well known from the Gulf of Mexico where it blooms in the spring and supplies the Sargasso Sea population via the Gulf Stream current.

Map of the western Atlantic showing the locations where floating sargassum is well known. GOM - Gulf of Mexico

However, since 2011, sargassum has also been accumulating in the complex system of recirculating ocean currents across the equatorial Atlantic, from Brazil to West Africa. It is this 'new source region' for floating pelagic sargassum that is now supplying large volumes of sargassum to the Caribbean and the coasts of West Africa via ocean currents that show considerable seasonal and inter-annual variation. This means that predicting when Caribbean sargassum influxes will occur, is very challenging.

Map of the tropical Atlantic showing the location of the 'new source region' for floating sargassum stretching across the equator from Brazil to Africa.​

Although there is still much debate on exactly how this new equatorial Atlantic sargassum population established, there is general agreement that its persistence is fuelled by a combination of climate change and general ocean eutrophication (land-based nutrient pollution), and that sargassum influxes into the Caribbean is the 'new normal'.

The impacts of sargassum on Eastern Caribbean fisheries have been varied, with some fishers reporting enhanced catches and availability of species and sizes not normally harvested, such as yellow and almaco jacks and small dolphinfish. Others however have suffered significant declines in their catches, which has had significant negative impacts on the post-harvest sector and fish availability for consumers. The flyingfish fishery, for example, has been badly affected, with flyingfish being almost impossible to find and catch in sargassum years. The Barbadian fishing industry in particular, where flyingfish would normally make up 60% of the annual landed catch and support a significant number of the island's fishers, small-scale processors and vendors, has been badly affected.

During sargassum years, flyingfish have essentially disappeared from the fish markets and restaurant menus. Dolphinfish, on the other hand, also a primary target species in the region's pelagic fisheries, has responded quite differently. Large numbers of very young dolphinfish travel with the sargassum and have started appearing much earlier in the year than the traditional pelagic fishing season. 

Graphs showing the impact of sargassum on the total landings of dolphinfish and flyingfish in Barbados. Since the first sargassum influx in 2011, landings of dolphinfish have dropped by 37% and for flyingfish by more than half (52%) prior to and after the first impact. Data from Oxenford et al (2019)​
Indiscriminate harvesting of these small individuals has seemed like a bounty, but is likely responsible for the virtual disappearance of larger dolphinfish later in the season, and a marked reduction in the total weight of dolphinfish landed overall.

Fishers are, however, all in agreement that sargassum presents a nuisance or even a hazard to navigation at sea, can damage boat engines and fishing gear, can negatively impact landing sites and prevent access to their vessels and fishing grounds. These impacts have resulted in lost fishing time and higher operational costs.

What’s next?
CERMES has continued to pursue sargassum-related  research and collaborations, developing new projects and seeking funding to build on the work completed so far. 

In this regard, we are pleased to announce the launch of our SargAdapt Project funded by the Caribbean Biodiversity Fund through their EbA Facility, that will be implemented over the next three years (2020-2022) with various Caribbean project partners.  Click here to learn more about SargAdapt.

We are also continuing to actively pursue opportunities for partnerships, collaborations and synergies with others working on sargassum adaptation in the region. We will keep you updated as things develop.
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