Researchers gauge seaweed fouling beaches
Study measures time sargassum takes to dissolve
By Harvey Rice
July 18, 2014 | Updated: July 18, 2014 10:33pm
GALVESTON - Kirsten Stokes slogged through a mass of stinking seaweed piled up against the Galveston seawall in an effort to answer two questions: How much seaweed arrived in Galveston in the worst season in memory, and how much longer will it take the seaweed to dissolve?
Stokes, 23, wore waders as she plunged into the enormous accumulation of seaweed west of the 61st Street jetty where there is only a wedge of beach in the corner, making it difficult for city beach-cleaning equipment to operate.
She is one of four graduate students, assisted by four undergraduates, at Texas A&M University at Galveston who have been measuring the amount of seaweed landing on Galveston beaches in front of the seawall since the onslaught began in April. The final tally won't be made until the end of the year, but a preliminary estimate of how much piled up in front of the seawall on May 22, the day of the heaviest seaweed influx ever recorded for a 24-hour period in Galveston, is eye-opening. More than 8,400 tons of sargassum landed on beaches between 17th Street and 61st Street, a stretch of about 3.3 miles.
The work by the students will help the Galveston Park Board and other cities along the Gulf Coast cope with seaweed that could be an increasing problem, said Robert Webster, Texas A&M research assistant directing the students. Webster developed the Sargassum Early Advisory System that warns cities in Texas, Louisiana, Mississippi and Alabama when seaweed is approaching their shores.
"One of my fears is that what's happening now will become the norm instead of the exception," Webster said.
The information gathered by his students will allow Webster to predict not only when seaweed will arrive, but how much, as well.
"We are kind of in a historic period in that we were out there measuring something that there probably has not been this much of in the recorded history of Galveston," he said.
The seaweed invasion has threatened tourism, an economic mainstay for Galveston. The proliferation of seaweed was caused by a combination of unseasonably cold weather and currents that held the sargassum offshore for longer than normal, allowing it to thrive in nutrient-rich waters of the Gulf and expand into vast rafts of seaweed dozens of miles wide.
'Sargassum triangle'
Thomas B. Shea
Texas A&M Galveston student Mike Wurl uses a wheel to gauge seaweed newly swept in by the tide.
Mike Wurl, 29, a junior majoring in marine science, and Kyle Robertson, 27, a senior engineering major, joined Stokes early in the morning to take measurements on the beaches east of 61st Street before Park Board beach-cleaning machinery arrived. Wurl pushed an orange wheel along next to the heap of seaweed washed in overnight, known as a wrack, while Robertson plunged a pole into the deepest section, known as a crest, to measure its height. Stokes took GPS readings, or points marked by orbiting satellites, marking the high tide line.
Last week, the students began measuring the giant, smelly collection of seaweed west of 61st Street, which they have dubbed the "sargassum triangle." Stokes found that the sargassum accumulation extends 352 feet, more than the length of a football field, at its widest point at the 61st Street jetty and stretches 2,927 feet east along the seawall.
How long will it last?
Stokes carried three broomsticks with measuring points marked along their length and jabbed each one into the sargassum at intervals. The broomsticks showed that the seaweed is about 3 feet thick. She will keep checking the broomsticks to find out how fast the level of seaweed sinks, giving an idea of its decomposition rate. Combined with other measurements, the Texas A&M team will be able to calculate how fast seaweed decomposes and therefore how long a pile like the sargassum triangle will take to fade away.
"Everybody wants to know how long it will be there," Webster said. "This will give us information on how we can estimate that."
Kelly de Schaun, Park Board executive director, said information being gathered by the students will help the board manage such large influxes of seaweed. For instance, seaweed in previous years benefited the beach, and the Park Board recommended that private beaches leave it instead of raking it.
Decomposed seaweed helps bind the sand and keep it from blowing and washing away. But this year they learned that it can be too much of a good thing, de Schaun said.
Heeding the board's previous advice, a private beach allowed an immense amount of sargassum to sit.
"Now we are seeing that leaving it hasn't been the best because the beach is muddy rather than sandy," de Schaun said. The Texas A&M study will allow cities like Galveston to determine how much seaweed left on the beach is too much.
De Schaun said cities, counties and nongovernmental organizations all along the Gulf Coast are looking to Galveston to come up with answers to their seaweed problems, and the students at Texas A&M are a key part of finding those answers.
Michael Morris, Corpus Christi parks and recreation director, said the techniques being developed at A&M will be helpful in dealing with the problem.
"This has been a very difficult summer with seaweed," Morris said.
The Sargassum Early Warning System has helped with managing the seaweed, he said, and getting a close estimate about how much will be an improvement.
"It can't help but help you," Morris said.
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