[USA] Green shoots of recovery are sprouting up throughout the Indian River Lagoon.
A three-year, $110,000 experiment has offered hints of hope that the lagoon’s seagrass can recover from a freefall, triggered by a 100-mile-long algae bloom in 2011.
In still-barren spots where scientists transplanted seagrass from healthier areas of the lagoon, grass grew back, but often, not for long.
Some of the transplants couldn’t withstand the voracious appetites of manatees, sea turtles and other marine grazers. The small transplants, encircled within plastic fences or metal cages, became salad bars for long-famished grazers that have for years faced slim pickings for seagrass. Manatees often munched up what grew back once protective metal cages or plastic fences were removed, or pinfish swam through openings in the plastic fences for a meal. But the bottom line was what scientists had hoped to prove.
“If seagrass gets there, can it survive? The answer seems to be ‘yes,’ a pretty definitive ‘yes,’ in absence of grazing,” said Bob Virnstein, an environmental consultant with Seagrass Ecosystems Analysts in Palatka.
Officials think larger-scale transplants might overcome the grazing pressure. But they’re unsure whether such transplants would be worth the cost, which can run hundreds of thousands of dollars per acre, or if it makes more sense to let the grass recover on its own. Transplants may be an option to jump start seagrass in Melbourne, Palm Bay and other areas now barren of grass. A final report on the project is due in September.
Cloudy waters and hungry grazers were among the biggest challenges to growing back the grass, the scientists say.
On a trip Wednesday to a transplant site in Palm Bay, Lori Morris ducked underwater to run her fingers through lush strands of shoal grass inside the protective plastic cages.
The water is so cloudy that the thin blades of grass can’t be seen from the surface in water only a few feet deep.
“This was a gorgeous bed,” said Morris, a scientist with the St. Johns River Water Management District, in waist deep water.
They run into another Catch-22 when trying to grow back seagrass. The plant needs clear water so that sunlight it requires to grow reaches the bottom. But without seagrass, more sediment stirs up from the bottom, clouding up the water and blocking sunlight.
They call this transplant spot, just south of Ozzie’s Crabhouse in Palm Bay, the Exxon site, because it’s near a gas station.
Fewer crabs crawl around these parts in recent years, since massive algae blooms over several consecutive years took over.
But something’s getting through small openings in the fences that protect the seagrass transplants, maybe pinfish or some other small fish, the scientists suspect.
“No one’s seen it happen,” said Chuck Jacoby, a supervising environmental scientist with the water management district.
Nearby, a car engine block, covered in barnacles and algae barely breaks the water’s surface. Someone dumped it there, maybe as a mooring to anchor a boat. Fish seem to like it.
Marine critters like the seagrass transplants, too. They find them fast.
“The amount of grazing was a surprise,” said Bob Chamberlain, a scientist with the district, which is wrapping up its seagrass transplanting study. “The grazing was very important to the lack of recovery.”
Two transplant sites along the shoals of Sebastian Inlet faced similar grazing pressure, but fared better because of the clearer water near the inlet.
The scientists use shoal grass, because it’s among the fastest growers.
They temporarily placed metal “manatee cages” over many of the transplants to keep ravenous seacows from chomping their experiment bare. But after environmental consultants planted some early tufts of grass, they returned later the same day and found evidence a seacow had made a snack of their work.
The inlet’s effort was part of a larger project that transplanted grass at several sites in the lagoon, including sites in Wabasso, the Banana River, the Exxon site and three sites in Sebastian Inlet.
“Manatees, crabs and turtles is I think the combination. Everything kind of got to it,” said Martin Smithson, administrator for the Sebastian Inlet District.
“It doesn’t appear to be conducive to a widespread public effort at this time.”
Crabs and waves rooted up the transplant on the north side of the channel, but the other two sites at the interior of the inlet’s shoals withstood the grazing, said Don Deis, a senior scientist with Atkins North America, the inlet district’s consultant.
“We just have to wait. I keep predicting 10 to 20 years before we start seeing the mix of seagrasses that we saw before the die-off,” Deis said.
“We see grazed areas, but they’re not a major problem to the coming back of the species that were once significant in the shoals,” he added.
Seagrass provides prime habitat for fish, crabs and other marine life and is considered a key barometer of the estuary’s overall health. Each acre of seagrass supports about 10,000 fish and $5,000 to $10,000 in economic activity in the lagoon region, according to St. Johns River Water Management District and other studies.
Transplants are just one way biologists hope to restore some 74 square miles of seagrass lost since 2009, much of it clouded out by algae.
The scientists harvest the seagrass with hand tools only — no machinery — and manually install the grass at the recipient study sites.
Similar grass transplants in recent years have shown success along Sebastian Inlet’s interior, patching boat propeller scars and other barren spots. The inlet district saw grass thrive after it had to transplant grass to make up for seagrass impacted by an August 2007 dredging of the channel. But large influxes of algae-ridden water from the north wiped out most of the grass along the inlet shoals, scientists said.
The lagoon has undergone severe seagrass loss since 2011, when an unprecedented phytoplankton “superbloom” clouded out the sunlight seagrasses need to grow. Then a brown tide bloom hit the northern lagoon and southern Mosquito Lagoon. The same algae species bloomed almost eight years in a row in Laguna Madre, Texas, making it the longest harmful algae bloom ever recorded.
In the aftermath of the blooms here, more than 135 manatees, 75 bottlenose dolphins and 250 brown pelicans died.
One positive sign scientists find at Sebastian Inlet is the emergence of Johnson’s seagrass, listed federally as a “threatened” species.
It’s pioneering roots typically precede a seagrass rebirth, providing substrate for other species of seagrass to latch onto and grow.
Spots farther from any inlet face a much longer road to recovery.
At the Exxon site in Palm Bay, what appears to be a small crab scampers across the bottom of one of the fenced-in grass transplants.
A pair of much larger, fist-sized crabs cling to one of the other fences.
Meanwhile, the researchers cling to hopes that more green shoots will soon sprout, enough to fend off all the grazers.
“There is recruitment,” Morris said of the recent natural sprouting up of seagrass near the transplants. “It’s just going to take a lot longer.”
Photo: (Photo: Craig Bailey/FLORIDA TODAY)
View original article at: Seagrass hints at Indian River Lagoon rebound