English

Deborah Goodwin,Jeffrey Schell,Amy Siuda

doi:10.5670/oceanog.2015.70

Abstract

English

Highlights

During June 2011, pelagic Sargassum began washing ashore along Caribbean, Gulf of Mexico, West African, and Brazilian coastlines in unprecedented quantities
Did the invading pelagic Sargassum drift out of the Sargasso Sea, a vast region bounded by the currents of the North Atlantic gyre (Smetacek and Zingone, 2013)? Alternatively, is its source the North Equatorial Recirculation Region (NERR), as suggested by satellite-derived observations of Sargassum mats (Gower et al, 2013) and hindcast models of Sargassum landfalls (Johnson et al, 2013)? Our recent net sampling indicates that the invading Sargassum did not come from the Sargasso Sea
We noticed the seaweed looked different from the Sargassum fluitans or S. natans with which we were familiar from 20 years of sailing in the Sargasso Sea, the Caribbean, and Florida Straits (Figure 1a)

Summary

Shipboard Observations Reveal Dominance of a Previously Rare Form

During June 2011, pelagic Sargassum began washing ashore along Caribbean, Gulf of Mexico, West African, and Brazilian coastlines in unprecedented quantities. We noticed the seaweed looked different from the Sargassum fluitans or S. natans with which we were familiar from 20 years of sailing in the Sargasso Sea, the Caribbean, and Florida Straits (Figure 1a). Within the North Atlantic, Caribbean Sea, and Gulf of Mexico, Winge (1923), Parr (1939), and SEA’s shipboard sampling over the past several decades (unpublished) indicate that S. natans I Parr and S. fluitans III Parr were most common while other morphological forms were rare. S. natans VIII is mistaken for S. fluitans, the latter has significantly smaller blades (Figure 1d) These and other differences in physical structure may influence the ecological role of each form. On the Observed S. natans VIII proliferation basis of both Sargassum composition and throughout three of these regions is sig- abundance, the Sargasso Sea exhibited no nificant given its historic low abundance connection to the Caribbean events.

Eastern South Caribbean Sargasso

Findings

Contributed by the International Ocean Color Coordinating Group