Seagrass cover in the Indian River Lagoon surrounding Sebastian Inlet increased by nearly eight acres from 2018 to 2019 – a hopeful sign of recovery for at least one portion of the beleaguered estuary following devastating seagrass losses wrought by the algal “superbloom” in 2011.
While seagrass patches range from small and spotty to completely absent in much of the 156-mile-long waterway, Sebastian Inlet’s 145-acre western flood tidal shoal boasts about 75 percent recovery, according to marine biologist Don Deis of Atkins North America, who has been surveying the area annually for the Sebastian Inlet District for the past 12 years.
Environmental scientists consider seagrass to be the foundation of the lagoon ecosystem. The submerged vegetation filters pollutants from the water, slows down erosion, and provides food and shelter for everything from tiny invertebrates to large fish.
Deis and Inlet District executive director James Gray credit the inlet’s twice-daily tidal flushing from the Atlantic for the steady improvement in local seagrass coverage.
“It’s a sign of how important keeping the inlet open is to maintaining the central part of the estuary,” Gray said.
“I’m happy with seeing the acreage go up,” said Deis. “The area around the inlet continues to recover slowly. It’s not leaps and bounds. You’re probably looking at decades [for complete recovery].”
Deis, who drew his data from aerial photography and from snorkeling and wading the flats, said seagrass species composition around the inlet has shifted radically since the superbloom. Manatee grass – a stable, slow-growing, bed-forming species that dominated the shallows before 2011 – has been overtaken by Johnson’s sea grass, a threatened species that occurs only here and in Miami’s Biscayne Bay, and shoal grass.
Deis said dredging done in the inlet by the Inlet District last year to keep the Inlet open did not harm seagrass.
“We were also encouraged to see areas of new growth after project completion along multiple transects,” Gray said.
On the downside, Deis documented 34 prop scars on the inlet flats that were inflicted by careless boaters taking shortcuts from the Intracoastal Waterway to the channel or from the channel to a shallow anchorage area. He said there’s really no excuse for damaging sea grass because caution signs are posted around the flats and a free inlet navigation guide is distributed at local marinas and elsewhere.
“We see idiots even though there are signs everywhere,” Deis said. “They drive all over the shoals.”
“People need to know where these sensitive seagrass beds are, understand why protecting them is so important, and know that if they run aground, they should stop the engine, tilt the motor and pole, drift or walk the boat to deeper water,” Gray said. “Continued outreach and education are key.”