Wrack, not ruin: Marsh grass, seaweed on Beaufort County beaches annoys tourists, boosts wildlife

tbarton@islandpacket.comJune 22, 2012 

A deluge of dead marsh grass and seaweed on Beaufort County beaches has prompted complaints from visitors and residents and led ecologists to caution against its removal.

Local officials say there isn't much they can do about clearing the debris. The stuff, collectively known as wrack, plays several key roles in beach ecology. Clearing it would remove a crucial habitat and food source for wildlife and nutrients for dune-protecting plants, they say.

The Georgia Department of Natural Resources told Tybee Island officials earlier this week to stop clearing beaches of wrack for that reason.

On Hilton Head Island, town officials are urging beachgoers to be patient while the tides eventually wash it back out to sea. Beachgoers can push the debris to the side to clear established footpaths to the beach, but may not remove it. Crews have cleared some seaweed, called sargassum, from town beach matting to maintain public handicapped accesses to the beach.

Wrack provides habitat for small invertebrates, such as crabs, shrimp and insects, that island shorebirds feed on. The birds also roost in the dead grass and sargassum at night and use it for cover from predators and for shade, Hilton Head sustainable-practices coordinator Sally Krebs said.

"Shorebird populations are not doing well up and down the East Coast because of loss of habitat," Krebs said. "If we continually scrape this up, these birds don't have as good a chance of survival."

Wrack also acts as a natural sand fence, preventing erosion. Decomposing wrack serves as a natural fertilizer, releasing nutrients dune plants need, Krebs said.

"It's a pretty critical part of the beach environment," she said. "This stuff comes and goes."

The wrack invasion has been heavier this year, town public projects and facilities director Scott Liggett said. Officials speculate higher-than-usual tides from last month's "supermoon," followed by tropical storms that washed out estuarine systems where dead marsh grass accumulated during prolonged drought, are the cause for the dead grass on the beach. A supermoon happens when a full moon occurs at the same time the moon is at its closest approach to Earth.

"Tides pushed higher into the marsh, grabbed a buildup of material that had died and brought it out to where it could be deposited on the shoreline," Liggett said. "And shortly thereafter, you had different wind and wave patterns from storms that drove debris onto the island's beaches."

Liggett speculates the storms caused the globs of sargassum to wash up on Hilton Head beaches. The seaweed grows far out at sea and is occasionally blown to shore on strong easterly winds.

At Hunting Island, wrack has deterred sea turtles from nesting on the beach. State park officials have recorded about 120 "false crawls," where the turtles come onto the beach but choose not to nest. That's compared to about 110 false crawls documented for all of last year. Sea turtles nest from May to August.

Wrack "spooks them," said Amanda Wood, a naturalist at the Hunting Island State Park Nature Center. "They can't get around it and decide not to nest."

Liggett said town officials are conferring with representatives of the Coastal Discovery Museum, which monitors turtle nesting on Hilton Head, to assess whether wrack might impede hatchlings from reaching the ocean.

"The good thing is that this algae decomposes quickly and dries up and disappears in a few days," according to a news release about sargassum from the Coastal Discovery Museum. "While the bad thing is that while it decomposes it releases a pungent and fishy smell."

Related content

  1. Sea Turtle Protection Project
  2. South Carolina Department of Natural Resources

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