MIAMI – Beneath the murky surface of the waters at Crandon Marina, a foreign invader has taken root. Halophila stipulacea is a species of seagrass native to the Indian Ocean that has now found a new home at the bottom of Biscayne Bay.
“I think everyone is holding their collective breath to try and understand whether this will pose a major threat to the ecosystems here in South Florida,” explained Justin Campbell, an assistant professor of biology at Florida International University. “And we’re standing at Crandon Marina, which is actually ground zero for the first occurrence of this species in the continental US waters.”
Campbell says the invasive grass was only discovered here last month by an environmental consultant doing bottom surveys of the marina.
“He came across this meadow here and noticed that something looked off, this was a species that he did not recognize,” Campbell said.
But the research team at FIU knew exactly what it was.
For years marine scientists have been tracking the migration of Halophila stipulacea after it first appeared and proliferated throughout the Caribbean in the early 2000s, no doubt carried there by ships that have now brought it to South Florida.
“We actually think it came to Crandon Marina by vessel, by either sailboat or motorboat or something like that that was traveling from other areas in the Caribbean,” Campbell said.
But is it friend, or foe?
“This invasive species could eventually displace and overtake some of our native seagrasses,” he explained. “There is some data in other areas of the Caribbean, which is driving and fueling the concern that that might happen here in South Florida.”
For decades, Biscayne Bay has been losing acres of native seagrasses due to excessive nutrient pollution, especially in the northern Tuttle basin. That’s where as much as 90% of coverage has disappeared.
The arrival of this new intruder could be a game-changer.
“Certainly it could potentially disrupt the marine ecosystems that we have here,” Campbell explained. He believes that given the size of the meadow, about the length of basketball court, it’s probably been growing here undetected for about two years.”
And it’s not isolated to just one section of Biscayne Bay.
“It is spreading,” he said. “If you look past this boat anchorage, you see all of those trees there, we’ve discovered another six or seven individual patches of Halophila stipulacea growing over there.”
It is a hearty seagrass. Sprigs can easily break off, float away, and survive.
“These fragments can actually float for quite a long time, 10 days, and remain viable,” Campbell said.
As a matter of fact, just 10 miles north of Crandon Marina at Government Cut, Coral Morphologic Co-Founder Colin Foord was cleaning the lens of the famed Coral City Camera, when something unusual caught his eye.
“I found this little sprig of seagrass that was just floating along at the water’s surface, and I had never seen it before, so I took it,” Foord explained.
The marine biologist brought it back to the lab, where he planted it in one of his tanks. He had heard of an invasive seagrass species taking over the Caribbean, a quick Google search confirmed his find.
“It wasn’t until I read the article that I said, ‘Wait a minute, this is unusual’ because they say it’s not in Florida yet, and clearly it’s here now,” Foord said.
According to Foord, the spring quickly took root and began to grow, even becoming the snack of choice for a native Emerald Green Crab living in the tank.
“Actually, I found that it’s quite tasty to crabs,” he said. “That suggests that it can provide a food source to some of our native species.”
That includes species like Florida’s manatee population, which has been under stress for years, with hundreds starving to death.
“Just because it’s non-native doesn’t necessarily mean that it is going to destroy our native ecosystem,” Foord said.
In fact, seagrasses help purify water, filtering sediments, that can then promote the growth of other seagrasses and can also capture carbon.
But Campbell cautions that it’s still too soon to know what the impact of this newcomer will be.
“So the question is, is this invasive species able to provide the same benefits that our native seagrasses do,” Campbell explained. “This is an open question, and something that we’re trying to understand better.”
Right now the plan is to monitor the Halophila stipulacea in and around Crandon Marina, and to check out other local anchorages to see if it’s made its way elsewhere here in South Florida.
At this point scientists say there are no plans to remove it, fearing that could potentially cause more harm than good.