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  new-press.com 18 Mar 07
Birds play key role in restoring seagrass
 Gulf's essential plants damaged
By Kevin Lollar klollar@news-press.com

KEY WEST — It doesn't seem like a big deal really: a couple dozen cormorants, pelicans and gulls sitting on stakes rising above the blue-green waters of the Florida Keys National Marine Sanctuary. Who would ever think these birds are doing their bit to help the environment? To be more precise, they're fertilizing seagrass beds that have been damaged by boats.

Boat damage

Like Lee County, the Florida Keys National Marine Sanctuary has a problem with boat damage in seagrass beds. Most boat damage in Lee County's seagrass beds is prop scarring — a recent state study for the Charlotte Harbor National Estuary Program documented 30,064 acres of prop scars in the greater Charlotte Harbor region.

In the Keys, the prop scarring is compounded by "blow-holes" — a blow hole is created when a boater runs aground in a seagrass bed and, instead of poling off or waiting for the tide to rise, uses the engines to power off. This action dredges a deep crater and blows away grass.

"Boat injuries add up," sanctuary environmental specialist Kerry Grimshaw said. "I've heard it called 'death by a thousand cuts.' They definitely impede the health of the ecosystem."

Restoration

Because seagrass beds are essential components of the Gulf of Mexico's coastal environment, sanctuary scientists have developed a seagrass restoration project.

When a boat makes a blow-hole, the first step is to develop a three-dimensional map of the damage using a Trimble — a GPS receiver and computer. "It's super-accurate, to 50 centimeters (about 20 inches)," sanctuary environmental specialist Alicia Farrer said. "It's great. You can do anything with it. You could check your e-mail out there if you wanted to." To make the map, a scientist walks the perimeter of the damage with the Trimble, which takes a reading every second. This gives the shape of the blow-hole. Then, scientists use a depth finder to measure the various depths of the blow-hole, thus creating a contour map.

Next, the blow-hole is filled — the 3-D map determines the blow-hole's volume, which tells scientists how much fill to use. Finally, sanctuary staff drive 10-foot-long 3Ú4-inch PVC pipes 5 feet into the bay bottom — on top of each pipe is a 4-inch-by-4-inch-by-2-inch block of wood — and plant shoal grass in the fill.

The birds

This is where the birds come in: Marine birds are always looking for a place to perch, and the blocks of wood on the PVC pipes are very attractive.

But what does this have to do with seagrass restoration? "A researcher noticed that around pilings there are often lush areas of seagrass," Farrer said. "It's from cormorants sitting on the pilings and doing their business. The droppings are a natural fertilizer."

Following that logic, birds sitting on the PVC pipes in a filled-in blow-hole fertilize the newly planted seagrasses. "It's a real high-tech operation," Grimshaw said.

Turtle grass is a more productive species of seagrass, but the scientists plant shoal grass because it grows better in the high-nutrient environment provided by the birds. After 18 months, the stakes are removed, turtle grass moves in and displaces the other species.

"The bird stakes work," Farrer said. "It's cheap. It's easy to do. "It's great, except when you pull them out: After 18 months, they're pretty well coated. Or, when you're swimming around the stakes monitoring seagrass growth, you hope nothing lands on your head or goes down your snorkel."

Although the sanctuary concentrates on blow-holes, bird stakes could easily be used to help restore prop scars. "It's an applicable restoration technique for your area," Grimshaw said. "It sure won't make things worse. If you go out the day after somebody makes a prop scar, plant some seagrass and put up bird stakes, you will definitely cut recovery time."

Seagrass awareness

During the last five decades, hundreds of thousands of acres of seagrass have been lost along the Gulf — losses in Gulf estuaries range from 20 to 100 percent. Much of the Gulf's seagrass loss is result of dredge-and-fill activities and declining water quality, but as the number of boats increase, so does boat damage.

In 2001, Gov. Jeb Bush proclaimed March Seagrass Awareness Month, the intent of which is, in part, to educate the public about importance of seagrass.

"Boat damage is definitely a problem," Farrer said. "We've had success with bird stakes. That's why we keep doing it, but education is what really has to happen.

"We can't just keep putting Band-Aids on — putting bird stakes all over the place. People would rather see seagrass than bird stakes."
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