A New Way to Look at Eelgrass

It’s easy for East Enders to think of the eelgrass that has provided habitat, most famously, to the Peconic Bay scallop, as a part of our lost heritage. But seagrasses, essentially rooted grasses that thrive when fully submerged, have become threatened throughout the world.

Right here on Long Island, we’re doing some groundbreaking research that could have positive implications for seagrasses around the world.

Dr. Bradley Peterson, a marine ecologist with Stony Brook University’s School of Marine and Atmospheric Sciences’ labs in Southampton, has been following the fate of Long Island’s eelgrass since he joined the faculty at the campus, formerly part of Long Island University, in 2003. He gave a presentation on his research at the college Oct. 20.

“Submerged aquatic vegetation is among the most productive of marine environments,” he told a crowd of students and interested community members. “It requires a lot of light and grows in shallow water, which is one of the reasons it is in such peril.”

You know all those algae blooms you’ve been hearing about on the news? The ones that are caused by excessive nutrients entering our bays? Well, sea grasses are one of the biggest victims of algae blooms.

“The first thing that seems to disappear with overnourishment is light,” said Dr. Peterson.

“Seagrasses require 10 to 30 percent surface light. After that, things start growing in the water, and there’s no light on the bottom.”

Dr. Peterson said the world has lost one-third of its seagrass since 1880. We’re currently losing a football field every 30 minutes, and the rate of decline in seagrass since 1990 has sped up to 7 percent per year.

On Long Island, he said, about 23 percent of the sea grass in our estuaries disappeared between 1967 and 1977, due to increasing nutrients, and another 40 percent disappeared during the brown tide explosion between 1985 and 1988.

There’s been a lot of research and restoration work attempts in the Peconic Bays and South Shore estuaries since the brown tide explosion, but Dr. Peterson said some of the early research has proven wrong.

Initially, seagrass experts who were brought in said Long Island’s seagrasses were suffering because of “poor connectivity and inbreeding.”

Zostera marina, a.k.a. eelgrass, can reproduced through clones, sending out shoots from existing plants, but it can also grow from seeds. Initially, researchers believed the genetic similarity of these clones were the reason eelgrass couldn’t adapt to algae blooms.

“We found that to be absolutely false,” said Dr. Peterson. “If you went more than eight steps away, you never found another clone. That tells you our population is driven by seeds.”

Much of the effort to replant eelgrass on Long Island has centered around replanting shoots of eelgrass in locations where they had historically been known to grow, often weaving the seedlings into a round burlap mat before placing it on the sea floor.

Dr. Peterson said there has been little success after years of attempting to replant eelgrass beds using this method, at a cost of nearly $1 million per acre. And areas that seagrass has liked in the past have changed, and may no longer be as conducive to the spread of sea grasses as they were before.

But collecting eelgrass seeds and dispersing them directly has proved a promising and cost-effective method, he said, when coupled with doing work to help improve the ecological health of our estuaries, by reducing nutrients into the bays and by seeding them with shellfish that can filter algae from the water. It’s about understanding the connectivity of an ecological system, not just about keeping your eye on seagrass.

“We can collect six million seeds with two weeks’ work,” and broadcast them onto sandy bottom lands, he said. “If we can actually change the system, the plant itself has a vast ability, from seeds, to change the space.”

He pointed out slides of an area of Shinnecock Bay that had been planted with seeds. The area had initially been covered only 3 percent by seagrass. When left alone for six years, however, that area jumped to 43 percent coverage.

“That’s a natural seed set that grew and coalesced in Shinnecock Bay,” he said. “We made no improvement. That’s just natural progression.”

“Everybody wants to do something. They see a problem and they want to do something,” he said. “But where it was is not the same as where it was before. A lot of people spend a lot of money putting it back where it was. We have only so much time and money. I’m not telling you seeds will work everywhere, but we have seen some success.”

This success is important for many reasons, not the least of which is helping to provide crucial habitat to restore the Peconic Bay scallop.

“Eelgrass is more productive than a tropical rainforest,” said Dr. Peterson. “A lot of things live in them and hide in them, and they play the role of a nursery for shellfish and fin fish.”

He added that seagrasses provide three times the habitat of coral reefs.

Globally, seagrasses also play a big role in locking up atmospheric carbon, making them a fighter in the race against climate change. During that process, they also increase the pH of their surroundings, fighting off the linked threat of ocean acidification.

“Seagrasses, tidal marshes and mangroves only exist on .2 percent of the marine footprint, yet they’re responsible for 50 percent of its carbon sequestration,” said Dr. Peterson. “We can use restoration of habitats to drive down carbon.”

The fall SOMaS lecture series continues on Friday, Nov. 3 at 7:30 p.m., with a talk by Dr. Joe Warren on “Dining with the Leviathans of the Oceans. On Dec. 8 at 7:30 p.m., Christopher Paparo will give a talk on “Exploring Long Island’s Underwater World.” Both lectures will be held in the Duke Lecture Hall in Chancellor’s Hall.

Beth Young

Beth Young built her first boat out of driftwood tied together with phragmites behind her family’s apartment above the old Mill Creek Inn in Southold. Nowadays, she spends most of her time kayaking, learning about shellfish, writing newspaper stories, trying to sail a Sunfish, and watching the way the bay changes from day to day. You can send her a message at beth@peconicbathtub.com

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