… The sargassum invasion gets serious

It seems that annual dumps of yellow-brown sargassum seaweed have become part of the “new normal” in the Caribbean. A couple of months ago when we first wrote about it, drifts of sargassum were causing headaches for both tourism and marine life in the Turks & Caicos, Barbados, Bonaire, Grenada, Dominica, Cayman and Belize. The mats of floating weed have been getting bigger and thicker. They are washing up everywhere in the Gulf of Mexico and the Caribbean, including Jamaica’s north coast beaches.

Until recently most of the weed that reached us came from the Sargasso Sea, a sort of roundabout where four currents come together in the mid-Atlantic. It’s a variety of the weed that lives its whole life without attaching to the sea floor, and there’s a floating mat of it about the size of the continental United States right in the middle of the ocean. Storms break off chunks that end up in the Caribbean. Now there is a second source.

In the last few years, satellite observations have spotted massive rafts of floating sargassum coming from the north equatorial recirculation region – an area near the equator where a couple of warm currents come together. Conditions including pollution, agricultural runoff from the Congo and Amazon rivers, and rising sea temperatures occasionally trigger a bloom of sargassum, and under favourable conditions it can double its mass in just 11 days. Floating weed from this region is coming ashore in both the Caribbean and West Africa.

                                                              Illustration by Mark Garrison