Shortly after midnight on June 19, a team of about 30 scientists from Washington, D.C., and across the Southeast concluded a “bioblitz,” an intensive wildlife scavenger hunt, at the Smithsonian Marine Station in Fort Pierce. Over 10 days, the group collected and preserved more than 2,700 mud- and sand-dwelling animals from the Indian River Lagoon, considered by some scientists to be the most biodiverse estuary in the U.S
These animals, which included crustaceans, slugs, snails and worms, form a crucial layer of the food chain and are sentinels of environmental change. This makes them useful proxies for water quality and the ecological health of the Indian River Lagoon, which is still healing from a decade of pollutant-powered algal blooms that decimated seagrass meadows, triggered fish kills and starved manatees.
Led by the Smithsonian’s National Museum of Natural History (NMNH), the bioblitz is part of its first major effort to combine traditional natural-history collection techniques with an emerging technology known as environmental DNA to generate nearly real-time snapshots of a waterway’s wellbeing, said Holly Sweat, a benthic ecologist at the station and the bioblitz coordinator.
Environmental DNA, or eDNA, is genetic material shed passively by an animal, or “the dust of a species,” said Christopher Meyer, who leads the NMNH Ocean DNA Initiative. This material, which can be extracted from sediment, air or water, can act as a genetic fingerprint, helping scientists detect the recent presence of an animal, even if they don’t see or collect it.
Meyer, curator of mollusks at the NMNH, described the technology as a “better, faster, cheaper” way to capture diversity and ecological changes.
“It’s like a Swiss Army knife,” Meyer said.
If scientists can optimize the use of eDNA in the Indian River Lagoon, they can adapt the technology to monitor biodiversity and water quality in other critical Florida waterbodies, as well as coastal systems worldwide, Sweat said. She described the project as one of the first models globally for applying eDNA to conservation and restoration efforts.
“What we’re trying to do is on the forefront of that,” Sweat said. “What we’re doing here is not only intended to benefit our watershed, but it’s going to go way beyond our little corner of the world. There are estuaries all over the world that are facing similar problems.”
Smithsonian scientists in Fort Pierce have been tracking Indian River Lagoon species for decades as part of their quarterly Everglades restoration monitoring. But with current methods, they must physically capture and process animals, which can take months and limits their sampling to a small corner of a watershed.
EDNA offers a much more comprehensive, high-resolution picture of what’s in a body of water, Sweat said. She and other station scientists began extracting eDNA from lagoon sediment in 2024 — but many of these genetic fingerprints can’t yet be matched to species.
That’s where the bioblitz comes in: DNA from specimens collected and identified in the blitz will be sequenced to build a reference library of invertebrate species — a “who’s who” of the lagoon. EDNA samples can then be compared to the database.
To assemble the library, bioblitz participants boated out with sieves, scrapers, corers, nets and metal claws to gather clumps of algae, mud, sand and rocks sheltering aquatic invertebrates. The team sampled 32 sites between the Sebastian and St. Lucie inlets, as well as nearby reefs, sifting through the material to find and identify the animals within.
As species names rolled in, Sweat marked a list of the 1,200 “most wanted” species with neon stickers and wrote in finds previously unrecorded in the lagoon. While fully assessing the team’s results will take time, she estimated the haul included at least 100 known species that had not been documented in the lagoon before and dozens of species new to science.
“We’re always finding new stuff,” Sweat said. “We’ll never get to the end of the rainbow.”
Hidden world
The sheer amount of biodiversity in the Indian River Lagoon, a 156-mile waterway that spans temperate and subtropical zones, presents a formidable test to taxonomists, scientists who specialize in classifying a particular group of species.
When Yander Diez arrived at the station as a postdoctoral fellow in January, only two species of microturbellarian, a type of miniscule flatworm, were known from the lagoon. Since then, Diez, one of the world’s few flatworm experts, has identified more than 200 microturbellarian species in the waterway, 60-70% of which are new to science. (For comparison, there are 165 known microturbellarian species in the U.S.)
In a single day during the bioblitz, Diez processed 15 species of flatworms, 14 of which he recognized as undescribed by scientists.
“The number of species here is crazy,” Diez said.
Bob Virnstein, who has been studying the lagoon’s seagrass and mud-dwelling animals since 1976, said invertebrate diversity varied widely between the northern, central and southern portions of the estuary and even between sites that were yards apart. At one spot, his team collected 3,000 snails — at another nearby, they found one.
“It was like it was different worlds,” said Virnstein, who was not part of the bioblitz.
Sweat used invertebrate density calculations to estimate that hotspots on the lagoon floor contain nearly 9,000 organisms in an area the size of the average human footprint. Before massive algal blooms from 2011 to 2021, she remembers wading into the seagrass beds across the street from the station and finding young gamefish such as grouper and snapper and an abundance of seahorses and other invertebrates.
“You’d just get a whole smorgasbord,” she said. “We went … from what was a really diverse ecosystem down to something people didn’t even recognize. It was a little bit like a desert.”
For a decade, nutrient pollutants from runoff, wastewater, septic tanks and other sources, combined with hotter winters and wetter conditions, supercharged algae blooms that shaded out and killed the seagrass meadows that historically anchored the lagoon’s biodiversity. But the lagoon is showing signs of a rebound, with seagrass returning to parts of the northern and southern sections. With grass comes fish, invertebrates and other animals that rely on the plants for habitat and food.
On a bioblitz trip to a spoil island near Wabasso, Sweat shook a piece of drift algae, looking for signs of life. Crabs, shrimp and other crustaceans fell out in numbers she hadn’t seen since before 2010.
“That was a hopeful moment for me,” she said. “We’re all crossing our fingers and holding our breath that this trend will continue, so that the habitats will be recolonized because we’re still not anywhere near the diversity that we (had) before.”
Natalie van Hoose is a freelance environmental journalist who often writes about the Indian River Lagoon. Banner photo: Zachary Foltz, right, hands a bucket of rocks from a ledge four miles off Fort Pierce to Jay Houk of the Smithsonian Marine Station. Scientists returned the rocks to the water after rinsing off the invertebrates they sheltered. (Natalie van Hoose photo)
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This story was originally published by the Invading Sea and shared in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the Sun-Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.
