Why scientists fear rapid spread of 'aggressive' invasive species found in Florida

An aggressive species of invasive seagrass that has been traversing the oceans for more than a century has been detected in the U.S. for the first time.

Halophila stipulacea, a small-body seagrass native to the Indian Ocean, began spreading in the 1800s following the opening of the Suez Canal in Egypt, a man-made waterway that connects the Red Sea to the Mediterranean Sea and serves as a key trade route between Europe and Asia, Justin Campbell, a professor at Florida International University specializing in marine ecosystems, told ABC News.

A second mass invasion that originated in the Mediterranean and traveled across the Atlantic Ocean has been found in Miami's Biscayne Bay after traveling north from the Caribbean, Campbell said.

Researchers believe Halophila stipulacea has spread primarily through the passage of ships.

"It's very easy to see how some of these vessels could actually grab up a piece of this seagrass and then transport it relatively long distances," Campbell said. "Whenever you first recognize this particular species in a new area, you often find it in marinas or boat anchorages."

The theory proved true in South Florida. The species was first noticed by someone who was diving or snorkeling near the Crandon Marina in early August, according to researchers. Once Campbell was alerted to its presence, testing proved that Halophila stipulacea was, in fact, in Biscayne Bay.

The patch within the marina has grown to the size of a basketball court, and several patches have extended outside the marina as well, Campbell said. Since the region is popular for boating, researchers are worried about the spread, Campbell said.

Based on the size of the patch, researchers believe the invasive seagrass has been in the marina for a few years, Campbell said, adding that it "easily" resembles some of the native vegetation, making it easy to miss. A variety of invertebrates have taken up residence within the invasive seagrass.

In addition, the species is a "clonal plant," meaning it produces asexual clones of itself, allowing the spread to occur even faster, Campbell said.

"Certain species have the capacity to break apart and then drift a certain distance," he said. "And then those fragments can resettle and start a new population."

In 2021, the species was determined to be a high risk for arrival, establishment and potential impacts in Florida, researchers found . In addition, invasive species tend to do well when there are disturbances, and the warming of temperatures in ocean waters could be assisting in the spread, Deah Lieurance, an assistant professor of invasive species and biology management, told ABC News.

With its arrival, scientists are concerned for Florida's 16,000 acres of native seagrasses, especially considering what has taken place in other regions, Campbell said. In places like the Caribbean and the Western Atlantic, Halophila stipulacea has been able to outcompete and displace the native aquatic marine plants, he said.

"It's predicted to out-compete native seagrasses in Florida and … around the island of Dominica," Lieurance said.

Invasive species have proven to be costly in the U.S.

From 1960 to 2020, reported costs of biological invasions in the U.S. were at least $1.22 trillion, according to a paper published in the journal Science of The Total Environment .

Annual invasion costs increased from $2 billion between 1960 and 1969 to $21 billion from 2010 to 2020, the paper found.

Invasive species have the potential to change entire ecosystems and wipe out species, Lieurance said.

"It would be things that are irreversible, so species extinctions, or you've changed the soil or some other aspect of the ecosystem that you cannot fix -- you can't go back and remediate," Lieurance said.

Researchers are currently looking into whether it would be a productive and cost-effective solution to remove as much of the Halophila stipulacea as possible, Campbell said.

"I think there are certainly going to be larger and broader discussions about how [effectively] we can manage this -- whether we should actively manage it," he said.

One idea would be to inform boats coming from the Caribbean to be aware of anything they are transporting on their vessel, which would be a first-of-its-kind mitigation, Campbell said.

Furthermore, experts on invasive species are monitoring to see if there are more to intercept, Lieurance said.

The Florida Fish and Wildlife Conservation Commission did not immediately respond to ABC News' request for comment.