Smelly seaweed makes mess of South Florida beaches
A bounty of sargassum seaweed washed onto South Florida beaches this summer, creating a buffet for seabirds and a squishy, reeking obstacle for swimmers.
The cause of the seaweed surplus, which occurred in even greater volume in the Caribbean Sea, is a mystery to scientists, although one with several prominent suspects. Among these are global warming, the Deepwater Horizon oil blowout, clouds of dust blown across the ocean from the Sahara and fertilizers washed off farms and carried by rivers to the ocean. One expert says it’s possible we’ve entered a new normal, with abundant dumps of seaweed
onto our beaches every summer.
Along Fort Lauderdale’s 7 miles of beach, city crews typically rake up about10 cubic yards of seaweed. But July was a particularly heavy time, spokesman Matt Little said, with 48 cubic yards picked up in a single day.
“A lot of guests commented about it. Why isn’t this raked up? Why can’t you as a hotel rake it up,” said Robert Keesler, general manager of the Pelican Grand Beach Resort. “You come here to swim at a pristine beach, and you wade out into the water and see it floating in the water. It isn’t a pleasant swimming experience. I’ve been at the hotel for six years. It’s the most I’ve ever seen.”
“Too much seaweed,” was the comment on the website TripAdvisor from a July visitor to Miami Beach.
A bushy brown algae that can grow several yards long, sargassum can be found throughout the tropical and subtropical waters of the Atlantic Ocean. It gave its name to the Sargasso Sea, a section of the North Atlantic bounded by currents, where Portuguese sailors saw vast mats of the vegetation floating by the wooden hulls of their ships.
As sargassum drifts with the currents, it provides habitat and a feeding grounds for a vast range of fish, as well as sea turtles and sea birds. When it washes up on the beach, it attracts insects and small shore creatures, which provide food for seabirds, crabs and other wildlife. Known as beach wrack, the decaying seaweed on shore is an important part of the unique ecosystem where ocean meets land.
It also gives off the rottenegg stench of hydrogen sulfide gas. It’s slimy to walk on. It’s not part of many tourists’ fantasies. Great for the environment but toxic for tourists, sargassum presents authorities in charge of beaches with the difficult decision of what to do about it.
“People have to understand wrack is the basis for the food chain on the beach,” said Ken Banks, a biologist at the Broward County Beach and Marine Resources Section. “Yet we rake it up every day to keep the beach clean. You’re taking away the basis of the food chain. Shorebirds, crabs. Beachgoers may not like it, but if they understand, they may be more tolerant of it. Or not.”
Most cities rake it off the beach and haul it away.
Fort Lauderdale takes a non-wasteful approach, trucking the sargassum to the city’s composting site at Snyder Park. In three or four months, the seaweed decomposes into soil that the city uses for planting projects.
State parks along the beach, such as John D. MacArthur Beach State Park in northern Palm Beach County and John U. Lloyd Beach State Park in Broward County, leave the seaweed in place as wildlife habitat (an exception is Hugh Taylor Birch State Park, where Fort Lauderdale is allowed to rake it off ). Palm Beach County stopped raking it up from county parks a few years ago for budget reasons but also recognizes the environmental benefits of leaving it there, said Michael Stahl, environmental program supervisor.
Brian Lapointe, a scientist at Florida Atlantic University’s Harbor Branch Oceanographic Institute, said he suspects the increase in sargassum could be related to fertilizers washing from farms into the ocean. Plant nutrients, particularly nitrogen, which foster the growth of crops in the Midwest, wash into the Mississippi River, which carries them to the Gulf of Mexico, where they fertilize the growth of sargassum.
“There are clearly elevated nutrients there, and nutrients are going up year by year, with increasing use of fertilizers and population growth,” he said. “Sargassum appears to have faster growth rates in water with high concentration of nitrogen.”
Another possibility, he said, involves the 2010 Deepwater Horizon oil spill. The petroleum and the chemicals used to disperse it could have helped fertilize the growth of the seaweed.
James Franks, senior research scientist at the University of Southern Mississippi’s Gulf Coast Research Laboratory, said there’s speculation among scientists that the Caribbean and Gulf sargassum blooms could be related to climate change. Higher water temperatures near the Equator could reduce winds and current, allowing sargassum to accumulate before being carried by currents to the north.
Robbin Trindell, head of the marine turtle program of the Florida Fish and Wildlife Conservation Commission, said extreme amounts of seaweed can impede hatchlings heading to the ocean. But she said none of this outweighs the importance of seaweed on beaches in preventing erosion and capturing sand to build beaches.
“People say it will interfere with the hatchlings getting to the water, but that’s always been part of their habitat,” she said. “It builds up beaches. During storms, it’s pushed up the beach and accumulates sand. It starts to break down and forms a little dune. It helps accumulate wind-borne sand. It’s very counterproductive to take it away.”