VoteWater Deep Dive: Seagrass is returning to the Indian River Lagoon! … Or is it?

In southern lagoon new seagrass is sprouting; in northern lagoon progress is slower. But Lake O discharges and impacts from development could ruin it all.

Lorae Simpson is seeing an unusual sight in the Indian River Lagoon this summer.

“When I stick my face in the water, I see seagrass,” said Simpson, director of scientific research and conservation at the Florida Oceanographic Society in Stuart. “We’re seeing this year that seagrass is coming back in the lagoon like gang-busters. It’s by no means like it was back in the good old days when the lagoon was full of it; but I’d be shocked if by the end of 2023 we don’t see an overall increase in the amount of seagrass in the lagoon, at least by a bit.”

Simpson’s anecdotal evidence comes on the heels of a Marine Resources Council (MRC) report in March showing that although water quality is improving, seagrass in the lagoon is declining.

The MRC’s Indian River Lagoon Coastal Community of East Central Florida Progress Report noted levels of nitrogen and phosphorus pollution are being reduced, which helps curtail the growth of toxic algal blooms.

“We’re making historic progress,” Jim Moir, interim executive director of MRC, said in a March 20, 2023, news release about the report.

Given the improved water quality, you’d think seagrass would be thriving as well.

Water quality improves while seagrass struggles

A graphic in the report shows both water quality and seagrass growth in the lagoon slowly but surely improving from the mid-1990s until 2007, then declines of both until 2011.

At that point water quality, with some ups and downs, starts showing overall improvement. But seagrass begins a period of significant decline until the end of the report’s data period in 2020.

The Palm Bay-based MRC is calling for broader quality testing in the lagoon by state agencies, which currently take samples to determine levels of phosphorus, nitrogen and chlorophyll-a — which can indicate excess algae — as well as turbidity, or water clarity.

The information is important because seagrass provides habitat and food for nearly 70% of all sea life in the lagoon, including manatees, sea turtles, dolphins and recreationally and commercially important fish and shellfish such as redfish, sea trout, snapper, pink shrimp and crabs.

It also stabilizes sediments and improves water quality by filtering pollutants from water bodies.

In other words, healthy seagrass makes for a healthy lagoon. And a healthy lagoon makes for a healthy economy for the areas along it as tourists are attracted to fish-filled, crystal-clear water.

Signs of new seagrass growth returns near the Stuart Sandbar in this 2022 photo. We need more than hope to make sure they survive.

Half the seagrass is gone

Over the long term, though, the lagoon’s seagrass beds have been disappearing at an alarming rate.

In 1943, researchers calculated the 156-mile-long lagoon contained about 71,000 acres of seagrass. As of 2019, the seagrass beds had shrunk to about 34,500 acres.

A single acre of seagrass can produce over 10 tons of leaves per year and may support as many as 40,000 individual fish and 50 million small invertebrates, according to the Indian River Lagoon Species Inventory, a joint effort of the Smithsonian Marine Station at Fort Pierce and the Indian River Lagoon National Estuary Program.

What’s killing it?

Most of these losses were caused directly or indirectly by development along the lagoon:

  • Seagrass needs saltwater and lots of light, but it loses both whenever canals and drainage ditches dump freshwater into the lagoon. All that freshwater can drop salinity levels in the lagoon below the 10 parts per thousand that seagrass needs to survive. The freshwater carries sediment, which can smother seagrass and prevent light from reaching the bottom.
  • Drainage water from fertilized farmland and yards can contain high levels of nitrogen and phosphorus, which feed algae blooms that shield seagrass from the light it needs.
  • Seagrass beds often show telltale scars from boat and propeller scrapes.

“Sure, natural events such as hurricanes add sediment-laden water to the lagoon and threaten seagrass,” Simpson said, “but the seagrass can just as naturally survive those events.”

It’s when unnatural amounts of water with unnatural amounts of sediment and other pollutants running off developed land pour into the lagoon that seagrass succumbs to the onslaught.

With each year of unnatural runoff, the seagrass gets more “weakened” and takes longer to rebound.

Improvements but no guarantee

“The lagoon’s seagrass is just now starting to rebound from the dire conditions the MRC reported through 2020,” Simpson said.

“It turns out 2022 was really dry until September, so the water quality is now better everywhere in the lagoon, and the seagrass is starting to respond.”

But don’t go popping the champagne corks yet. Just because seagrass may “pop back one year” doesn’t mean it will continue to thrive.

In fall 2019, seagrass in the lagoon, especially along the southern section in Martin County, seemed to be mounting a return. But by April 2020, the bottom of the lagoon looked “like a moonscape,” said then-Indian Riverkeeper Mike Conner.

“I’m optimistic that, if Mother Nature is given time to rebound, the seagrass in the Indian River Lagoon can come back,” Simpson said. “But every time I drive down (state Road) A1A and see all the ‘for sale’ signs on the so-far undeveloped land along the lagoon, I’m not so optimistic. … We’ve got to get a handle on development, to make sure any development from now on is done in an environmentally conscious way.”

Development with less impact?

Some advocate for “Low Impact Development,” which according to the federal Environmental Protection Agency incorporates “systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat.”

One example of low impact development already proving to help seagrass growth is the use of “living shorelines” — breakwater structures that include native plants to help keep silt-laden stormwater out of the lagoon.

With help from volunteers, Vero Beach-based Ocean Research & Conservation Association has created nine living shorelines on Indian River Land Trust properties along the Indian River Lagoon.

In six out of the nine sites we are monitoring, we saw increased seagrass coverage from March 2022 to March 2023,” said Edith Widder, ORCA’s CEO and senior scientist. “We believe this may be a consequence of the protection afforded by the breakwaters we installed.”

No discharges = more seagrass

Also of utmost importance in the southern lagoon is keeping harmful discharges from Lake Okeechobee at bay. The brief rebound of seagrass in the lagoon in Martin County in the fall of 2019 was the direct result of no discharges in the summer of that year.

Indeed, discharges have been minimal now for several years — which likely explains the welcome seagrass rebound being noticed in the Stuart area.

That, of course, is subject to change if high volumes of water and toxic algae from Lake Okeechobee get flushed to the coast this summer.

But the implications here are clear: If we want to save seagrass in the lagoon — and the manatees and all other creatures that depend on it — Lake O discharges must become a thing of the past, and we have to change the way development takes place along the lagoon.

For only if we have cleaner water over the long haul can we stop counting the acres of seagrass lost, and begin counting the acres gained.