Sargassum preventing turtles from nesting

[Barbados] While Sargassum, the brown seaweed that has covered many beaches in several Caribbean islands, has hindered the nesting of the leatherback turtles at various nesting beaches in Trinidad and Tobago, thankfully it has not caused the death of any of the animals, as it has in Barbados.

Reports are that, as of two weeks ago, 42 full grown and juvenile hawksbill, leatherback and green turtles died as they struggled to make it to and out of Barbados nesting sites, which lay under two to three feet of Sargassum seaweed.

Nature Seekers Tour Coordinator, Candice Superville, told Sunday Newsday their personnel had not found any dead turtles, but the seaweed has obstructed the turtles from coming up onto the sand to nest. She said the turtles had tried to reach the nesting ground, but with seaweed as high as four to six feet, many turned back into the sea.

An influx of Sargassum has covered east coast beaches from Cumana to Guayaguayare since April.

The National Oceanic and Atmospheric Administration noted that, “this floating habitat provides food, refuge, and breeding grounds for an array of critters such as fishes, sea turtles, marine birds, crabs, shrimp, and more… Sargassum serves as a primary nursery area for a variety of commercially important fishes such as mahi mahi, jacks, and amberjacks.”

Sargassum usually comes from the Sargasso Sea in the Atlantic Ocean around Bermuda, which was named for the Sargassum seaweed which floats there. However, many scientists believe this Sargassum invasion of the Caribbean, similar to the one in 2011, has no connection with the Sargasso Sea. Instead, it is believed the seaweed influx is due to changing weather and ocean current patterns.

Using ocean current data, scientists at the Center for Fisheries Research and Development at the University of Southern Mississippi (USM) back-traced the 2011 Sargassum sightings to the North Equatorial Recirculation Region (NERR), which is warm and nutrient-rich and could therefore support the growth of Sargassum.

Superville said Nature Seekers, based in Matura, recently started a project in which the people of the community assist in the removal of seaweed on a daily basis. “Matura is not like Manzanilla where we can use an excavator to clear the seaweed. Because of the land formation and the loose sand, it has to be removed manually, and Matura Beach is about 7.5 km so that’s a lot of ground to cover,” she said.

She said because of the location of the beach, there were high waves and rough seas, so it was a risk having people remove seaweed without supervision and lifeguards – an expense they could not afford.

She said because of the limited clear spaces or less dense seaweed in certain areas, some turtles gravitate to the same spots. This has caused a lot of “nest loss” this year, as turtles dig up other nests to lay eggs.

Superville said she hoped the turtles that turned back went to a beach that had not been affected by the seaweed, like Grande Riviere, to nest. She noted there had been more reports of “spontaneous nesting” – turtles nesting at beaches they do not usually visit – this year in areas such as Erin in Icacos, Maracas, and Tyrico.

However, Len Peters, Chairman of the Grande Riviere Nature Tour Guide Association said, from observation of the number of turtles that nested at the Grande Riviere Beach, he did not believe the turtles migrated.

Peters noted that the Grande Riviere Beach has one of the highest density nesting sites for Leatherback turtles in the world. He said during March to April, the one kilometre beach usually sees 200 to 300 turtles per night, in May numbers could reach up to 500, while in July numbers drop drastically to about 20.

“Last year the number of turtles in one night peaked at 498 and this year it peaked at 418 so right now they are running true to trend. You would think that if turtles that usually nest at other beaches were coming here, the numbers would increase to 700 or so per night. I’m not saying that none have come. There might be one or two but, based on the numbers, there is no large-scale fallout. Therefore the big question is, where are they going?” he asked.

Giancarlo Lalsingh, Programme Manager of Save Our Sea Turtles (SOS) Tobago answered that question saying, “Sea turtles return to nest at beaches where they were born some 20-30 years previously. After several unsuccessful attempts to nest, turtles prevented from nesting at the beach of their birth because of the influx of seaweed, will eventually dump their eggs at sea.”

Unfortunately, this would mean a loss of hundreds, and probably thousands of hatchlings.

Lalsingh explained that SOS primarily monitors turtle nesting beaches at Lambeau Beach, Turtle Beach, Grafton Beach, and Mt Itvine Back Bay in Tobago. However, he said Lambeau Beach was the only one affected by the seaweed. He said the volume of seaweed deposited at the front of the beach caused a decrease in nesting activity as turtles were unable to access the beach to nest.

“The only action that can be taken is to carefully clear the seaweed, where possible, to increase the beach access to nesting turtles. Heavy Machinery should not be used at turtle nesting beaches affected as their use can damage the beach, increase beach erosion, crush incubating nests already on the beach, and injure or kill turtles and other wildlife that may be trapped in the seaweed,” he said.

Thankfully, he said SOS had not recorded any incidences of stranded or dead turtles at their sites but pointed out that Sargassum posed challenges to biodiversity in the region, therefore it was important to monitor and gather data on local impacts.

Photo: A dead sea turtle in Sargassum found by the Barbados Sea Turtle Project. Author: www.loopnewsbarbados.com

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