Seaweed siege unusual during tourism season

Drifting meadows of seaweed have made their way to Palm Beach County's shoreline, a poorly-timed siege with seasonal visitors still in town but one that was forecast by researchers studying an exponential growth in the floating fauna.

In late January, University of South Florida oceanographers watched tangled mats of sargassum move through the Florida Straits and into the Gulf Stream, warning that a bout of easterly winds could push them toward the coast.

While seaweed has sporadically hit beaches all year, last week's gusty onshore breezes were enough for a noticeable increase, triggering calls from beachgoers to clean up the macroalgae that scratches like steel wool when dry.

"No one wants to walk through that," said 10-year Boynton Beach resident Michele Abderhalden, who wants the city to increase its sargassum clean-up efforts at Oceanfront Park. "Sometimes it smells and there are flies and bugs around it and you can't even sit on the beach at that point."

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Sargassum benefits the environment by providing shelter in the ocean for hatchling sea turtles, who feed on the tiny crabs and other organisms that live in it. Birds also pick through it to find food.

In large quantities, however, it can tangle in boat propellers, and, if left piled up on the beach, can prevent turtles from laying eggs and new hatchlings from reaching the water.

It's unusual to get so much seaweed this time of year — it's typically a summertime nuisance — but USF scientists think the mats are leftovers from 2018's record-setting sargassum crop.

Palm Beach County's seaweed policy for its beaches is to let nature take its course with wave action either mixing it into the sand or taking it back out to sea.

"Seaweed is part of the natural cycle," said Andy Studt, Palm Beach County's environmental program supervisor. "We tell people it's normal, and to try to leave it if they can, but there are concerns out there with people trying to attract tourists and wanting to keep the beaches nice."

That was the dilemma for Roger Amidon, general manager of the Palm Beach Marriott, Singer Island, whose guests, some of whom pay $800 per night, want a pristine beach. Tourism season is extended this year with Easter arriving April 21. Last year, Easter fell on April 1.

Amidon hired contractors to hand rake the seaweed toward the dune line and bury it — a tedious task that can keep workers busy all day as more sargassum washes ashore.

"We went and bought pitchforks and rakes and cleaned it up. The next morning it came back," Amidon said. "We really took an aggressive approach and we've gotten a lot of compliments from our guests."

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Amidon said the current sargassum assault is the worst he's seen. It follows 2018's record-setting sargassum year as measured by USF researchers studying satellite images back to 2000 and news accounts before that.

USF's Optical Oceanography Lab began publishing a monthly sargassum bulletin in February 2018 that tracks the seaweed through the west Atlantic Ocean and Caribbean Sea.

Last Month, the lab noted sargassum covered 200 square miles of the region. That's compared to the average of 11 square miles as measured between 2011 and 2017.

USF post-doctorate researcher Mengqiu Wang, who wrote a 2017 paper about predicting blooms in the Caribbean, said there may be a decrease of sargassum in the Caribbean in April.

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But South Florida wouldn't benefit from that lapse for weeks or months.

"Currently, there is still so much sargassum leaving the Caribbean Sea, there will be a time lag," she said. "Maybe next month we'll have a better prediction for summer."

Ideas about why sargassum has increased in recent years include Saharan dust raining down phosphorus as it crosses the Atlantic, fertilizer in sewage runoff entering rivers along the sargassum's path such as the Mississippi in the Gulf of Mexico and the Amazon to the Atlantic.

Beach managers are constrained during turtle nesting season, which began March 1, as to how they can clean the beach. Most cities have specially-licensed contractors who use tractors to clear the sargassum at least twice a week, but they are confined to areas below where turtles may nest.

For the Town of Palm Beach, the abundance of seaweed on Midtown Beach has been of particular concern following a budget cut that slashed the allotment for cleaning public beaches at Midtown and Phipps Ocean Part to $17,000, down from about $72,000.

Wally Majors, Boynton Beach's recreation and park director, said the city beach is cleaned twice a week, but sometimes it's hard to tell.

"I've literally watched our vendor rake the beach and the next day it looks as bad or worse," Majors said. "I know the seaweed doesn't look pretty and may smell a little bit, but it's just part of our environment."

 Kmiller@pbpost.com

@KmillerWeather