The Coastal Star

Along the Coast: Sargassum -- too much of a good thing?

Sargassum seaweed blankets the Ocean Ridge beach in July.

Jerry Lower/The Coastal Star

By Cheryl Blackerby

    
Sargassum, the brown free-floating algae that turns up on Palm Beach County’s beaches every summer, is essential for marine life. The thick masses of seaweed stretch for thousands of miles in the Atlantic Ocean, giving safe sanctuary and nutrients to fish and endangered sea turtle hatchlings.
    Onshore, the seaweed helps keep expensive replacement sand on beaches, offers crucial delicacies such as crabs and snails to seabirds, and provides nutrients to plants on dunes.
    But scientists, and certainly beach resorts, are wondering if there is too much of a good thing.
     “We have noticed a little more seaweed than usual in September, and in August it was pretty bad,” said Wally Majors, director of Boynton Beach Recreation and Parks Department. “We speculate it may have been caused by Tropical Storm Erika. It depends on wind direction.”
    The wet tangle of seaweed is brought onto the beaches every year from May through August, but since 2011 the increasing amount of sargassum has caught the attention of marine scientists who are researching causes of the excessive seaweed, which has piled onto beaches in the Caribbean and clogged coves in the Florida Keys.
    Palm Beach County has been lucky that the seaweed hasn’t come onshore in the amounts that it has in the Keys.
    “There has been more than average, but not to the extent of what is being reported to the south,” said Dan Bates, deputy director of the Palm Beach County Department of Environmental Resources Management.
    Scientists say there may be many reasons for the abundance of seaweed.
    “The problem began right after the Deepwater Horizon oil spill in the Gulf of Mexico in 2010, but we’re trying to piece it together,” said Dr. Brian Lapointe, research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute. “Unfortunately, very little of the BP money was spent to study sargassum.”
    The reasons for the excessive growth of the seaweed, says Lapointe, are numerous: fertilizers dumped into the gulf and ocean by rivers, warming oceans, and probably the gulf oil spill.
    Septic tanks were one of the surprise culprits in northwestern Florida and the Florida Keys, scientists discovered. And higher-than-  normal air temperatures and low winds, which influence ocean currents, were other probable causes.

Floating sargassum provides shelter for a sea turtle hatchling.

Photo by Steve Dougherty


    Sargassum travels on currents around the Caribbean, in the gulf, through the Florida Straits and in the Gulf Stream.
    “The Gulf Stream moves four miles per hour. This stuff can move pretty quickly,” said Lapointe. “In a matter of weeks, it can transit from the Keys to the Sargasso Sea, almost like a conveyor belt. It’s really cool. Sea turtle hatchlings rely on sargassum in their early years. They swim offshore until they encounter sargassum, then drift to the Azores.”
    The seaweed has been piling up on beaches in the Gulf of Mexico and in the Caribbean. The beaches of Galveston, Texas, were some of the first shores to attract national attention when beachgoers were faced with 50-foot-wide, 6-inch-thick brown mats of sargassum.
    In the Caribbean, 10-foot piles of seaweed are repelling tourists, and beach cleaners can’t stay ahead of the mess. Sea turtles are having trouble navigating the seaweed to lay eggs.
    “It’s very bad for turtle nesting in the Caribbean,” said Lapointe. “And the gas (emitted from dead seaweed) can kill turtles. Several nesting turtles were found dead in Barbados and they likely died from the gases.”
    The gases can be harmful to humans if there are large piles of decomposing seaweed, he said. “A lot of mangroves and coves in the Florida Keys are clogged with this stuff. It creates hydrogen-sulfide toxic fumes.”
    Prolonged exposure to large quantities of the gas can cause symptoms such as nausea, watery eyes and headaches. But the rotten egg smell will probably send most beachgoers running before they become ill.
    In Florida, a bigger threat to turtles, Lapointe said, are the cleanups of seaweed that damage nests and remove sand on renourished beaches.
    “Seaweed removal with heavy equipment such as Bobcats can really accelerate beach erosion and damage turtle nests,” he said. “In some areas, seaweed is buried in back dunes, which helps build beaches and supplies nutrients.”
    If the seaweed isn’t piled high enough to impede turtle nesting, he said, it should be left on the beaches, where it will help stabilize the sand. Seaweed is part of nature and should be appreciated for its contributions to a healthy ecosystem.
    Lapointe has been the chief scientist on numerous Caribbean and Atlantic Ocean research expeditions studying the health of tropical seagrasses and coral reefs.
    Sargassum is not a seagrass but a seaweed. The Sargasso Sea in the middle of the North Atlantic Ocean was named after sargassum, which floats there in vast amounts. Christopher Columbus was amazed by the seaweed when he crossed the sea in 1492.

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