Scientists still uncertain about Indian River woes
More than 350 scientists share lagoon theories
FORT PIERCE, Fla. – Polluting septic tanks, noxious muck and invasive lionfish topped an agenda of ills Thursday at the Fourth Annual Indian River Lagoon Symposium.
They were among a litany of environmental threats scientists discussed at the symposium, which continues Friday at the FAU Harbor Branch Oceanographic Institute in Fort Pierce.
Local 6 News partner Florida Today report more than 350 scientists, government officials and concerned citizens packed Harbor Branch's auditorium to share theories about what's killing the lagoon and how to stop it.
Scientists point with increasing confidence to excess nitrogen and phosphorus as the main killers. But they still scratch their heads — or sometimes butt heads — on where the two nutrients originate from and how best to keep them in check.
Some researchers point to our toilet flushes as a main culprit, while others point to muck at the bottom of the lagoon.
"Septic system effluent is a contributing factor to the elevated nitrogen levels in the Indian River Lagoon," said Marie Tarnowski, a researcher at Harbor Branch.
That's because Florida's sandy soils are inadequate for removing the two nutrients from septic tank drainfields, she said.
She and other Harbor Branch researchers say the 26,660 septic tanks in Indian River County add excess nitrogen and phosphorus to the surface and groundwater along three urbanized canals and the St. Sebastian River. They found levels of sucralose, an artificial sweetener common in wastewater, were correlated with elevated nitrogen in surface waters and in aquatic plants.
"Our study also showed that the canals are a conduit for these nutrients," Tarnowski said. "This is evidence for the septic system removal from the Indian River Lagoon drainage basins."
Another source of excess nitrogen and phosphorus is muck along the lagoon bottom. Muck comes from soil erosion, runoff and rotting plants.
Florida Institute of Technology researchers estimate that muck delivers as much or more nutrients into the lagoon north of Melbourne Causeway as does runoff.
Lurking among the muck and the mangroves is a venomous invader with voracious appetite for lagoon shrimp and crab: the lionfish, an invasive species originally from the Pacific and Indian oceans.
The popular, prickly aquarium fish first got loose into the Atlantic Ocean in the mid-1980s, and more of them may have been released during Hurricane Andrew in 1992. Now, the fish spans waters from the Caribbean to Rhode Island.
Emily Dark, a researcher at Antioch University New England in New Hampshire, found lionfish at or near all six lagoon inlets she studied, including Port Canaveral. She's documented more than 600 lionfish in the lagoon since 2008 but says many more are out there. They tend to stick to the same spots, she said, and they're here to stay.
"We suggest that the Indian River Lagoon is not just a nursery for lionfish but also supports them at all life stages," Dark said.
She recommended lionfish removal efforts in or near the inlets.
However, Thursday's presentations weren't all doom and gloom. Successful oyster-restoration projects provided one bright spot.
Linda Walters, a biologist at University of Central Florida, described significant improvements on oyster reefs she and volunteers create in Mosquito Lagoon, using oyster shells tied to plastic mats.
Brevard Zoo staff also reported oysters that volunteers grow at their docks are surviving.
The symposium comes in the wake of increasing pressures on the lagoon, as seagrass and the marine life that depend on it have been dying en masse in recent years.
The lagoon symposium offers an opportunity for citizens to learn what they can do to help.
"There are a lot of people that are actively engaged," said Dennis Hanisak, a research professor at Harbor Branch and one of the symposium's organizers. "A lot can be done ... Some of it is just getting started."
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