Sargassum natans, unlike the many benthic Sargassum species (i.e., those that live attached to the sea bottom), is a pelagic (free-floating) brown seaweed that occurs mainly far out in the North Central Atlantic Ocean, but washes ashore regularly. It is often associated with the Sargasso Sea, a very large region situated offshore from the southeastern United States, approximately south and east of Bermuda and seaward from the Gulf Stream. The Sargasso Sea, which accumulates large masses of Sargassum, results from a ring of prevailing ocean currents that enclose an enormous eddy (about 5.2 million square kilometers) which rotates clockwise as a result of the Earth's eastward rotation. Sargassum natans apparently reproduces only asexually, by fragmentation. (Gosner 1978; Kaplan 1988) Gower and King (2008) used satellite imagery to track the origin, distribution, and fate of  floating Sargassum. Using this approach, they analyzed data from 2002 to 2008 and were able to present the first mapping of the full distribution and movement of pelagic Sargassum in the Gulf of Mexico and western Atlantic. Their results revealed a seasonal pattern in which Sargassum typically shows strong growth in the northwest Gulf of Mexico in the spring of each year, is transported into the Atlantic in about July, appearing east of Cape Hatteras as a “Sargassum jet", and ends up northeast of the Bahamas in February of the following year. Gower and King note that the idea that pelagic Sargassum originates in the Gulf of Mexico, as they propose, was fairly common in the 19th century (based on ship observations), but became less widespread in the following century. Based on their findings, Gower and King conclude that that most pelagic Sargassum has a life span of one year or less, with the major “nursery area” being in the northwest Gulf of Mexico. Given their estimated average flow of about one million tons of Sargassum out of the Gulf of Mexico each year, the authors suggest the implied carbon flux should be accounted for in productivity and carbon models. 

Original publication: Gaillon, B. (1828). Résumé méthodique des classifications des Thalassiophytes. Dictionnaire des Sciences Naturelles [Levrault] 53: 350-406, Tables 1-3.

 Download PDF from Algaebase

Provide biological, medical and pharmacological activity - antibiotic

Provide biological, medical and pharmacological activity - treatment of goitre and renal disorders

Source of hydrocolloids - source of alginate

Source of organic chemicals - source of polyols; Contains: mannitol

Dawes, C.J. & Mathieson, A.C. (2008). The seaweeds of Florida. pp. [i]- viii, [1]-591, [592], pls I-LI. Gainesville, Florida: University Press of Florida.

Kim, C. S. (1972). The effects of dietary Sargassum natans and Ascophyllum nodosum on Salmonella gallinarum infection in chicks. Proceedings of the International Seaweed Symposium 7: 573-574.

Moreira, L. & Suárez, A.M. (2002). Estudio del género Sargassum C. Agardh, 1820 (Phaeophyta, Fucales, Sargassaceae) en aguas cubanas. 2. Variaciones morfológicas de Sargassum natans (Linnaeus) Meyer en dos localidades. Rev. Invest. Mar. 23(1): 55-58.

Moreira, L. & Suárez, A.M. (2002). Estudio del género Sargassum C. Agardh, 1820 (Phaeophyta, Fucales, Sargassaceae) en aguas cubanas. 4. Reproducción sexual en Sargassum natans (Linnaeus) Meyer y S. fluitans Børgesen. Rev. Invest. Mar. 23(1): 63-65.

Niermann, U. (1986). Distribution of Sargassum natans and some of its epibionts in the Sargasso Sea. Helgoländer Meeresuntersuchungen 40: 343-353.

Schofield, O., Evens, T.J. & Millie, D.F. (1998). Photosystem II quantum yields and xanthophyll-cycle pigments of the macroalgae, Sargassum natans (Phaeophyceae): responses under natural sunlight. Journal of Phycology 34: 104-112, 5 figs.

Sieburth, J.M. & Conover, J.T. (1966). Antifouling in Sargassum natans : Re-recognition of tannin activity. Proceedings of the International Seaweed Symposium 5: 207 only.

Lectotype locality: “Indica” (probably Jamaica) (Silva, Basson & Moe 1996: 687). Notes: Silva et al. (1996) recommend consulting Børgesen (1914a: 9) for more information on the lectotype locality of this species. 

Basionym: Fucus natans Linnaeus.

The type species (holotype) of the genus Sargassum is Sargassum bacciferum (Turner) C.Agardh.

Taxonomic notes: According to Silva et al. (1996) the following taxa apparently lie within the circumspection of this species but have not yet been formally transferred: Sargassum bacciferum forma capillifolium Kützing and Sargassum bacciferum var. spinuligerum Kützing.

Nomenclatural notes: Pelagic species (Guiry, pers. comm.). See Silva, Basson & Moe (1996) for details of the nomenclautral history of this entity.