Seagrass meadows still thrive on Florida's Nature Coast

Seagrass meadows are a hidden treasure of Florida’s coastal beauty, often overlooked in favor of beaches and mangroves. Yet beneath the surface, these underwater fields quietly support marine life, stabilize shores, and protect coastal communities.

Along Florida’s Nature Coast, seagrass meadows are not just surviving – they’re thriving. A recent study reveals that seagrass ecosystems in this region have remained remarkably healthy and undisturbed for thousands of years – and this resilience is rare.

Globally, seagrass meadows are in trouble. Since 1879, nearly 30% have vanished. Between 1990 and 2009 alone, seagrass beds declined by an estimated 7% each year. Unlike many regions where seagrass meadow loss is the norm, Florida’s Nature Coast has become a rare refuge for these vital ecosystems.

Lessons from past seagrass meadows

Researchers from the Florida Museum of Natural History at the University of Florida set out to understand how these meadows have endured. The common problem they faced is that we don’t really know what an untouched ecosystem looks like anymore.

“Nothing is really pristine today, because humans have altered all of Earth’s environments, but this is about as good as it gets,” said Michal Kowalewski, senior author of the study.

One major hurdle is the lack of long-term environmental data. “Most of the contemporary biological data we have postdates the Industrial Revolution,” Kowalewski explained.

“If you think about any type of real-time instrumentation that collects physical and chemical information about an environment, or if you think about the rigorous bio-inventory surveys, all of those things are from the last 50 to 100 years at most.”

Fossil clues beneath seagrass meadows

In other words, humanity has been altering nature far longer than we’ve been systematically observing it. Luckily, Earth itself keeps a record – in the form of fossils.

This is where conservation paleobiology steps in. Scientists use the recent fossil record to reconstruct past ecosystems.

Seagrasses, unfortunately, don’t leave fossils. Their soft tissues decompose quickly. But the animals living in seagrass meadows – especially shell-bearing mollusks – do leave lasting traces.

Kowalewski and his team have shown that mollusk fossils are reliable indicators of ecosystem health. When mollusks thrive, it’s a good sign that the surrounding environment is in good shape, too.

Studying Florida’s Nature Coast

For their study, the team sampled 21 sites across six estuaries along the Nature Coast. Using PVC hoses, they collected sediment from the seafloor, sifting through centuries of accumulated material.

“We collect sediment samples while scuba diving, and then we sieve those samples and extract all that we find in it,” Kowalewski said. “The samples are dominated by dead material, because it has accumulated there over many centuries. Typically, for every live bivalve or snail, we find thousands of dead specimens.”

Identifying and cataloging these specimens took years. But when the data was analyzed, the results were clear: mollusk diversity had barely changed in millennia. This suggests that the seagrass meadows they inhabit have remained stable, too.

“Only rarely do we find historical evidence that can make us optimistic about the current state of a local ecosystem,” Kowalewski said.

“Most conservation paleobiology studies tell depressing stories about shrinking habitats, declining biodiversity and diminishing ecosystem services. For once, at least, this is not the case. What’s thrilling to me is we can show this system is still in very good condition, which makes it even more important to protect it.”

A model for seagrass restoration

This discovery is more than just a pleasant surprise. It provides a valuable reference point for restoration efforts elsewhere. Healthy seagrass meadows are disappearing, but Florida’s Nature Coast shows us what these ecosystems should look like.

Elsewhere in Florida, seagrass has not been so fortunate. In Tampa Bay, nearly half of the seagrass was lost between 1950 and 1980 due to urban growth and pollution.

Although restoration efforts brought some recovery by 2018, recent declines have been noted again. On the state’s east coast, surveys show that up to 60% of seagrass has vanished in parts of the Indian River Lagoon.

Hidden nutrient pollution

Most of these losses stem from nutrient pollution. Runoff from farms and cities feeds algae and bacteria, creating dense blooms that cloud the water. This “marine cloud” blocks sunlight from reaching the seagrass below, starving them of the light they need to survive.

The Nature Coast has so far escaped this fate. In 2020, it was designated an aquatic preserve, helping protect its relatively undeveloped watersheds.

Study co-author Thomas Frazer is a dean at the University of South Florida College of Marine Science.

“There’s not a lot of development in those watersheds, particularly from the area around Weeki Wachee all the way up into the Panhandle, so the effects of excess nutrient delivery are not as pronounced as is in other places that have suffered as a consequence,” said Frazer.

However, this does not mean the threat has passed. Algal blooms are now an annual event in many parts of Florida. Even Nature Coast seagrasses may be affected if water quality declines.

Climate change and moving species

Climate change adds another layer of complexity. Rising temperatures are pushing temperate and subtropical species northward. Florida’s Gulf Coast, backed against the Panhandle, offers little room for further migration.

“There’s nowhere for them to go,” Frazer said. As marine life shifts, seagrass ecosystems may face new challenges.

A single blade of seagrass is home to countless organisms – hydroids, bryozoans, sea squirts, bacteria, and algae.

Normally, grazing fish and invertebrates keep these communities balanced. But if these grazers disappear or new species disrupt the balance, the health of the meadow could suffer.

“We’re already seeing range extensions of mobile fauna,” Frazer added. “A number of fishes, for example, are moving up north along the Gulf Coast, and they may either eat seagrass or consume grazers that help keep seagrasses clean of organisms that live on them.”

Why seagrasses matter so much

Seagrasses are ancient. They’ve been around longer than the dinosaurs and their benefits to both marine and human life are immense. Rachel Carson captured their importance in her 1955 book The Edge of the Sea.

“Thrusting their roots into the sand and shifting coral debris, the seagrasses achieve a firmer attachment than the rootless algae do; where they grow thickly, they help to secure the offshore sands against the currents, as on the land the dune grasses hold the dry sands against the winds,” she wrote.

Seagrasses stabilize the seabed, prevent erosion, and are vital for marine biodiversity. Despite covering just 0.2% of the ocean floor, they are responsible for 50% of marine carbon burial. They provide food for sea turtles, manatees, and fish. For countless species, seagrass meadows are essential nurseries.

“They provide very important nursery habitat,” Frazer said. “In Florida alone, more than 80% of the fish caught by commercial fisherman and recreational anglers spend some part of their life history in those seagrass beds.”

Protecting seagrass meadows

Frazer noted that seagrasses serve as a front line for storm protection. Their dense underwater meadows reduce wave energy by up to 40% in shallow waters, acting as natural storm barriers.

Florida’s Nature Coast now holds the largest seagrass meadows bed in the Gulf of Mexico. With careful management and ongoing conservation, it has the potential to stay that way.

While much of the world races to restore what’s been lost, the Nature Coast reminds us of a simple truth: sometimes, the best thing we can do is protect what we already have.

The full study was published in the journal Marine Ecology Progress Series.

Image Credit: Ben Jones / Ocean Image Bank

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