Pelagic Sargassum is a macroalgae that drifts at the ocean surface in small clumps or extensive mats, creating a unique and ecologically-significant marine ecosystem. Two species are common in the North Atlantic, S. natans and S. fluitans. Serving as a food source, nursery for juveniles, spawning ground, and/or protective habitat, Sargassum mats support diversities of invertebrates, fish, turtles, and seabirds at various points of their life cycle.
For more than 40 years, SEA has been documenting Sargassum species, abundance, and distribution along repeated cruise tracks through the Sargasso Sea, Caribbean Sea, and Gulf of Mexico. More recent investigations include associated epibiont and mobile fauna communities, genetic diversity, seasonal and interannual variability, and unique Caribbean inundation events. SEA Semester students also contribute to marine spatial planning and policy initiatives working to conserve the Sargasso Sea ecosystem.
Community of organisms
A uniquely adapted pseudo-benthic community of organisms lives among the dense vegetation of each pelagic Sargassum clump, including common epifauna such as hydroids and mobile fauna such as shrimp, snails, and crabs. At SEA, we are interested in understanding the factors that affect the diversity and composition of the associated Sargassum community, such as host species, geographic location, clump size, and clump aggregation/dispersion pattern. Both visual/microscope-aided identification and genetic population analyses are utilized to characterize Sargassum communities.
Selected Community of organisms papers and publications
SEA’s 40-year plankton net tow data set indicates that distinct seasonal and interannual distribution patterns exist for each Sargassum species. S. natans is most commonly found in the central Sargasso Sea while S. fluitans is more abundant in the Gulf Stream, North Equatorial Current, and Caribbean Sea. Our field observations complement satellite detection methods by providing species identification and finer spatial resolution.
Selected Distribution patterns papers and publications
During 2011-2012 and 2014-2015, pelagic Sargassum washed ashore in unprecedented quantities throughout the tropical Atlantic, including on many Caribbean islands. Once-pristine tourist beaches were covered by meters of stranded seaweed. Researchers at SEA have discovered that the Sargassum inundating the Caribbean in 2014-2015 is a previously rare form of S. natans, potentially originating in the equatorial region. Inundation events have ecological consequences at multiple scales, such as impacts to Sargassum mobile fauna communities, dependent fisheries and iconic species, and coastal ecosystem function.
Selected Inundation events papers and publications
Sargassum natans and S. fluitans each exhibit a diversity of morphological forms that have distinct but overlapping ranges; correct identification in the field is critical for understanding species dynamics and resolving questions of Sargassum connectivity among geographic regions. Presence or absence of thorns on the stem distinguishes between species: S. natans has smooth stems while S. fluitans has thorns. Within a species, leaf and bladder attributes can differ widely among forms. SEA uses both dip nets and surface neuston tows to collect Sargassum, then makes careful visual observations to determine the species and form.
Selected Taxonomy papers and publications
SEA alumni present Sargassum findings at Gulf & Caribbean Fisheries Institute conference
November 28, 2016
Doug Karlson, email@example.com
Recent SEA graduates Maddie Taylor (C-264) and Corey Wrinn (C-257), and former SEA Associate Professor (and SEA alumna, C-142) Dr. Amy Siuda (now at Eckerd College) attended a meeting of the Gulf and Caribbean Fisheries Institute (GCFI) in Grand Cayman earlier this month to present the results of their research related to drifting Sargassum.
The GCFI is a forum that brings together scientific, government, and commercial stakeholders to share scientific findings to better understand and manage the marine ecosystem of the Caribbean and Gulf region.
SEA Semester Faculty Report on Sargassum Beaching Phenomenon
September 07, 2016
SEA Semester in the News
Sargassum Watch Warns of Incoming Seaweed
SEA Semester professors Deborah Goodwin, Jeffrey Schell and Amy Siuda contributed to this Eos article on efforts to track Sargassum - including by satellite and from the deck of the SSV Corwith Cramer - to better understand and mitigate the recent phenomenon of Sargassum beaching events.
Read the article
Big Science Push!!!!!!!
April 28, 2016
Alesia Hunter, A Watch, Beloit College
Hey Everyone!!! We have made it to the North Sargasso Sea. It has been science all day today for me. A-Watch (my watch team) started our day of with a presentation on the coral reefs that are present in Bermuda from our visiting professor, Dr. Robbie Smith. I also got to work in the lab this morning during my watch, we completed a 100 count of the midnight Neuston net tow, and I got to do my first morning deployment of our CTD and Neuston net.
The Great SSV Corwith Cramer Line Chase!
April 26, 2016
Shalagh Canning, B Watch, Boston College
Hello to all on land and greetings from the Southern Sargasso Sea! As we head into our second week here on the Cramer, we are all getting into our routines and keeping very busy with our work. We are working around the clock on our watches to take care of the Cramer as she carries us north while deploying our science gear and collecting samples for our research.
Mike Oscar November Delta Alpha Yankee
April 25, 2016
Natasha Willcox, A watch, University of Rhode Island
The Sargassum is back! Kind of. Today we found the most Sargassum on the whole trip thus far, but it still wasn’t a whole lot. We wanted to take advantage of the find, so we were hove to all the way until class time at 1400. We got plenty of samples, and they are now being processed. Since being hove to means not too much action of the watch crew on deck, we decided to practice some celestial navigation.