Lives on the Sea: Vanishing marsh

  • Posted: Monday, June 25, 2012 12:22 a.m.
A mysterious die-off of marsh grass appears to be under way on this section of Wappoo Creek in West Ashley. Experts say the die-off, here and elsewhere, appears to be tied to a number of factors. Buy this photo

The spartina patches were bared, down to just mud.

This story is part of an occasional series looking at how the coast and the ocean off the Lowcountry are changing, and what it means for a region where people have made a life and a living for generations in tune with the sea.

At first Dale Aren thought the barren gaps were just an illusion in the marsh grass behind her Coburg Creek home. But for two years now the unsightly mud flats have widened. Her marsh appears to be dying.

Her neighbor, Pinckney Harper, has lived on the marsh nearly 30 years and never seen anything like this happen before.

More disturbing are the snails — hordes of them — clinging to the remaining stems along the high marsh bank.

The West Ashley woman isn’t alone in her concerns. Bare patches are turning up in the marsh off the Folly Road causeway and on Seabrook Island.

Along Hobcaw Creek in Mount Pleasant, Mark Hamner watched the marsh die this spring behind three homes, including his.

He’s lived there two decades and “it’s always been lush, beautiful,” he said.

In fact, marsh is dying all along the Southeast coast, said Christine Angelini, a University of Florida salt marsh researcher, who came last week to study the die-off at the Arens’ West Ashley home.

Periodic die-offs of patches of spartina — salt marsh cord grass — aren’t unusual, but “We’re seeing an increase in the size and the regularity of the die-offs,” Angelini said. “These may become more persistent features than we’ve seen in the past.”

Incredible habitat
Marshes might be the defining feature of the Lowcountry coast, with an estimated 400,000 acres of sweeping grasses.

They are the heart of the estuary, a nursery for countless marine creatures, including shrimp,

“Spartina provides this incredible habitat for any number of species,” Angelini said.

That nursery is disappearing.
A recent study in Cape Romain showed salt marsh there was being lost to overwash faster than it could replenish, and the bare spots were filling in with creek.

Research by Baruch Institute director Jim Morris suggested that as much as half the salt marsh of today might be gone in the next 20 or 30 years, just from sea rise.

If you factor in the potential depletion of the estuary marsh, the equation gets scary.

Ribbons of teeth
It would be easy to blame the snails. They are shredding the spartina.

The mollusks have radulae, ribbons of teeth that scrape like tongues, to eat algae from spartina. If a plant is stressed and weakened, the teeth can cut grooves. Fungus infests those grooves, and that kills the cord grass.

The snails don’t do it alone, though. A combination of exacerbating stresses usually kills the spartina, Angelini said.

Wrack — seaweed, other vegetation or debris — floats in on tides and can pile up against the high marsh, weakening and killing spartina. Angelini commonly sees that, she said.

Spartina also can get overloaded with “lethal levels” of salt accumulating in puddles from retreating tide. Particularly during droughts, salt water evaporates in place and not enough rain falls to clean out the salt, which concentrates the salt levels and doesn’t give the plants enough fresh water.

Recurring drought has plagued the Lowcountry since the severe 1998-2002 drought.

“There’s so much development going on … that’s always going on. This may actually be the work of nature, which is much better than humans, who can do a lot worse,” Hamner said.

But there’s a bigger issue, Angelini said. With climate changes under way, the region might well face more drought. That could mean a gaping loss of today’s marshes.

Hope
Spartina has tended to come back from die-offs, Angelini said. As more rain falls, stronger strains of the cord grass develop the ability to handle the stresses.

“The grass is resilient,” she said.

But not always. On Sapelo Island, Ga., pickleweed has moved into high marsh flats after a spartina die-off.

Pickleweed, a succulent that stores water and tolerates salt, doesn’t provide the species habitat that spartina grass does.

Re-seeding spartina doesn’t work well enough. Researchers are experimenting with transplants of whole colonies of mature spartina to restore lost marsh.

For now, though, whether these bare Lowcountry mud flats regrow “depends a lot on the weather,” Angelini said.

That’s hope, at least.
“I was worried it was something we were doing in our yard,” Aren said. “We’re going to be doing our rain dance.”

Reach Bo Petersen at 937-5744, @bopete on Twitter or Bo Petersen Reporting on Facebook.

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