Sargassum Information Hub
Information about Sargassum in the Tropical Atlantic.
The Hub provides information about:
• What sargassum is and why it is important
• Monitoring and forecasting of sargassum in the tropical Atlantic
• Management of sargassum
The Hub is jointly organized by the GEO Blue Planet, IOCARIBE of IOC-UNESCO, AtlantOS, and the Atlantic International Research (AIR) Center, in collaboration with several partners.
CERMES: Sargassum Outlook Bulletin
“Our Sub-regional Sargassum Outlook Bulletin provides medium-range (3-monthly) island-scale forecasts of sargassum influxes to the Eastern Caribbean, based on our validated sargassum transport model from the new source region in the equatorial Atlantic. It also provides comment on sector-specific implications for tourism and fisheries stakeholders, and provides summaries and links to the latest sargassum papers and innovations. By simplifying scientific jargon so that stakeholders can easily understand and benefit from the forecasts, we anticipate that the bulletin will facilitate wider access to specifically tailored early warning information, thus allowing better decision-making by key socio-economic sectors in the Eastern Caribbean islands.”
Assessing growth of pelagic sargassum in the Tropical Atlantic
M Corbin, HA Oxenford in Aquatic Botany 187, 103654 “Pelagic sargassum species, historically endemic to the North Atlantic, have now been identified in the Tropical Atlantic. For over a decade, massive blooms of pelagic sargassum have dispersed seasonally from this ‘new’ Tropical Atlantic source region, negatively impacting the coasts of Caribbean and West African countries. Significant strides have been made towards adaptation to this new ‘hazard’, yet many knowledge gaps remain that constrain improvements to these efforts. The key objective of this study was to add to the knowledge of pelagic sargassum growth rates in the Tropical Atlantic to better inform forecasting and innovative applications. Growth rates of the three commonly occurring morphotypes from the Tropical Atlantic source region, S. fluitans III, S. natans I and S. natans VIII, were studied in-situ using novel ‘growth mesocosms’ in neritic waters of Barbados under cool and warm ambient conditions. Overall, results reveal a significant difference in growth rates among all pelagic sargassum morphotypes, with S. fluitans III on average doubling its biomass in 13 days, S. natans I in 22 days and S. natans VIII in 31 days. Furthermore, growth rates of S. fluitans III decreased significantly with an increase in ambient temperature from the cool (mean 27.6 °C) to warm (mean 29.6 °C) water period. During both periods S. fluitans III grew significantly faster than the other two morphotypes. However, S. natans I only grew significantly faster than its conspecific morphotype, S. natans VIII, during the cool period. These findings highlight the different growth responses among sargassum morphotypes under varying conditions and add to the considerable variability in growth rates reported by recent similar studies conducted elsewhere in the Tropical Atlantic. As such, it is clear that further research will be needed…”
Climate-sargassum interactions across scales in the tropical Atlantic
R Marsh et al., 2023 in PLOS Climate 2 (7), e0000253 “The impacts of climate change on ecosystems are highly uncertain but potentially profound. One such impact may be the emergence of extensive mats of seaweed (macroalgae), due to the extraordinary proliferation of pelagic sargassum species, in the tropical Atlantic since 2011. Sargassum blooms are now an annual event and reached record levels across what is now known as the ‘Great Atlantic Sargassum Belt’ (GASB) in summer 2022. Monitoring across scales, from satellite surveillance to in-situ beach surveys, is bringing step changes in process-level understanding of sargassum. Physical and biogeochemical drivers of sargassum act at basin scale to shape the GASB, highly variable from year to year. In the local environment, sargassum is sensitive to ambient conditions, with new findings confirming that growth rates are temperature dependent. Multidecadal ocean warming may therefore be detrimental to sargassum, although projected changes in other drivers are uncertain. Emerging options for climate change action around sargassum include valorisation and carbon sequestration, although uncertainties are again considerable. In conclusion, the emergence of sargassum across the tropical Atlantic highlights interconnected systems that embrace physical, biogeochemical, and socioeconomic dimensions, with considerable scope for improved monitoring, process-level understanding and prediction.”
CERMES: Sargassum
“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.” Page discusses topic under What’s the problem?, What has CERMES been up to?,What have we learned? What’s next?
Applying Hazard Risk Assessment and Spatial Planning Tools to Sargassum Inundations in the Eastern Caribbean Small Island States as a Basis for Improving Response
Degia. A.K., M. Small, H.A. Oxenford, 2022. A . SargAdapt Project Report, FINAL DRAFT. Centre for Resource Management and Environmental Studies (CERMES), University of the West Indies, Cave Hill, Barbados, 72pp.Details for Barbados under ANNEX 1 Country-Specific Sargassum Hazard and Exposure Mapping and Description p. 18
Barbados, pages 18-27.
Sargassum blooms are here for the foreseeable future 15Mar2023
Post on this website Mar 15, 2023.
A Brown Tide of Sargassum Is Causing Havoc in Barbados
Julián Reingold & Lautaro Isern. Aug 28, 2024 on pulitzercenter.org. “Sargassum inundates Barbados in the summer, covering beaches, docks and coral reefs. Emerging from the sea a light orange colour, the seaweed turns brown once it dries out. But the most distinctive thing is the smell. A smell of rotting eggs hangs in the air. The decomposing algae is producing toxic gases, including ammonia and hydrogen sulfide, both of which pose a threat to human health. Portuguese navigators gave the Sargasso Sea its name in the 15th century. Now a new “Sargassum Sea” has emerged between West Africa and north-eastern Brazil. Dubbed the “Great Atlantic Sargassum Belt”, in 2011 the expanding zone reached Barbados in the Eastern Caribbean and has inundated the region between May and September ever since. Scientists have suggested the root cause of the sargassum expansion is discharge of nutrients and pollutants from mighty rivers in the Amazon region and warmer seas driven by climate change. Researchers from the US National Oceanic and Atmospheric Administration (NOAA) hypothesise that it may be fuelled by an extremely strong and long-lasting shift in the North Atlantic Oscillation in 2010. This may have shifted and strengthened prevailing winds, so they now blow sargassum from its eponymous sea and towards the Caribbean. The sargassum blooms continue to cause problems for Barbadian fishing, tourism, and the government officials tasked with solving the vast seasonal piles of rotting weed…A big problem for a small island state Barbados is the first land encountered by the currents that drag sargassum from the Atlantic Ocean into the Caribbean. The island’s triangular shape exposes almost half of its shores — famed exemplars of paradise tourism, with white sands and turquoise waters — to sargassum inundation…The Caribbean has been dealing with this so-called “brown tide” for several years, but little research has been undertaken. Micaela Small is a Barbadian marine biologist doing a PhD at the University of Southampton in the UK. She is examining the effects of these smothering waves of sargassum on the south-eastern coral reefs of Barbados. “When you have large influxes of sargassum in the near-shore reefs, it decomposes, causing a sargassum brown tide, reducing the oxygen and increasing nutrients,” says Small. “The water turns brown, and the health of corals is affected, as it requires pristine water to thrive.” This, she explains, can bleach the native coral species of Barbados, such as Porites astreoides and Pseudodiploria strigose, as the coral expel their symbiotic algae and thereby lose their colour and become vulnerable to death. This has been happening at the tourist hotspot Brownes Beach.”
Sargassum Monitoring Protocol: monitoring sargassum abundance using drones. SargAdapt Good Practice Guide Series 1.
Baldwin, K., H.A. Oxenford, J. Weekes, M. Small, J. Irvine and A. Desai (2022). University of the West Indies, Centre for Resource Management and Environmental Studies (UWI- CERMES), Barbados, 40 pp.
Free-swimming fauna associated with influxes of pelagic sargassum: Implications for management and harvesting
Kristie S. T. Alleyne et al., 2023 in Frontiers in Marine Sciences
“Mass accumulations of pelagic sargassum (Sargassum natans and S. fluitans) in the Tropical Atlantic, across the Caribbean and off the coast of West Africa, are causing extensive ecological and socioeconomic harm. The extraordinary volumes of sargassum influxes could also provide a business opportunity if innovative ways are developed to utilise the raw material. In-water harvesting provides the best opportunity to collect substantial amounts of ‘fresh’ sargassum that can be used in a variety of applications. However, sargassum rafts are living and diverse ecosystems with a range of associated fauna including fish that are targeted by fishers. The consequences of in-water harvesting of sargassum on the biodiversity, including associated fishes, remain poorly understood. Characterisation of this biodiversity within nearshore and offshore environments is needed to help guide best harvest practices and assess possible impacts on fishing opportunities. We assessed the free-swimming fauna associated with sargassum rafts at various distances from shore with the use of underwater video recordings. Over a three-month period, a total of 35 underwater surveys were conducted off the eastern and southern coastline of Barbados. Thirteen species (12 fishes and one comb jelly) from 8 families were identified, with the family Carangidae representing the greatest number of species (n=6). Application of the MaxN metric (maximum number of individuals of a species seen during deployment) revealed significant correlations with raft characteristics notably raft volume, raft distance from shore and water depth. The three environmental variables accounted for 9% of the variation (adjusted R2) in the free-swimming community composition with raft volume being the major driver of species richness. This aligns with ecological theory and supports our hypothesis that larger rafts would host greater species richness. The results demonstrate a strong affiliation between pelagic sargassum rafts and species biodiversity and abundance that will need to be considered by managers when seeking a best compromise between protecting beaches from inundation by sargassum and protecting biodiversity and fishing opportunities”