Seaweed washing up on Caribbean shores is nothing new, but it has been showing up in the record numbers this summer. Words like “smothering” and “choking” have been used to describe the heaping mounds of brownish seaweed covering beaches from Florida to Puerto Rico to Barbados. More than a nuisance, the invading plants have stymied tourists and local hospitality businesses as reports come in of dying fish and the smell of noxious gases. Enjoying a swim is out too, due to the long, crescent-shaped blankets of seaweed that choke fishing grounds before washing ashore.
According to the University of South Florida’s Optical Oceanography Lab, a staggering 24 million tons of the brown seaweed, called sargassum, covered the Atlantic in June, breaking the 2018 record by 20%. USF offers a sargassum monitoring report called the Sargassum Watch System (SaWS) via its website, using information provided by NASA and other sources.
Causes for the influx are not yet fully known, but according to the UN Environment Caribbean Programme (UNCEP), associated factors may include rising ocean temperatures, nitrogen fertilizer runoff, and sewage that feed algal growth.