‘Red menace’: Research looks at causes and possible mitigation for red tide outbreaks
Locally, there has been no issue of greater concern than the red tide bloom that bedeviled the area’s coastlines last year. Primarily affecting waters north of Marco Island, the microscopic organisms reproduced by the billions, spreading toxins and robbing oxygen from the water, leading to carpets of dead fish choking canals, respiratory problems for humans, and bottle-nosed dolphins and seabirds washing up dead on the beach.
Red tide, typically a seasonal phenomenon, has dissipated and is largely absent from Southwest Florida coastal waters in the new year. But the persistent bloom, coupled with devastating levels of blue-green algae washing down the Caloosahatchee River from Lake Okeechobee, have kept water quality issues from and center.
This red tide bloom (caused by the organism Karenia brevis) was first documented by the National Oceanic and Atmospheric Administration in October 2017 and is the longest outbreak in more than a decade. Millions of pounds of dead fish and marine wildlife were collected on Lee County Beaches in a few weeks this past summer, when the red tide outbreak was at its worst.
Hundreds of sea turtles, dozens of dolphins and even a whale shark are thought to have been killed by red tide since July. Approximately 40 dolphins washed up on Collier and Lee beaches in November.
With the area’s economy, particularly during the winter months of “the season” highly dependent on tourism, and quality of life and the health of our natural environment of great concern to residents, Dr. Bill Mitsch drew a more than standing-room-only crowd to his lecture Jan. 10 at the Naples Botanical Garden’s Kapnick Center. In addition to a capacity audience in the main hall, additional attendees filled two adjacent classrooms, where they were patched into a video link.
Mitsch, director of the Everglades-Wetland Research Park at FGCU, as well as Professor Emeritus of Environmental Science at The Ohio State University and courtesy professor in the School of GeoScience at the University of South Florida, said that media outlets including CNN had been pressing him for a “smoking gun” to explain the severity of the red tide outbreak. Ever the cautious scientist, he skated right up to the term without initially embracing it.
“We don’t have a ‘smoking gun.’ We do have data that is compelling.” That data, said Mitsch, pointed to nitrate-based fertilizer, from agricultural sources and residential lawns, as the culprit pushing Gulf waters past the tipping point where conditions become ideal for red tide.
“Red tide is and has been a ‘natural’ phenomenon but it is clear that human activities, principally high-fertilizer agriculture, bears responsibility for giving natural red tide a ‘booster shot,’” Mitsch summed up in the “Conclusions” slide in his presentation. “Our preliminary isotope study suggested nitrate fertilizer is the ‘smoking gun.’ Additional potential sources of nitrogen to the Gulf that we plan to investigate include rainfall nitrate caused by automobiles, septic tanks, and the Mississippi River brought to our coastline by north to south sea currents.”
Mitsch told his audience that, while nitrates – compounds of nitrogen and oxygen – are implicated in red tide, studying the correlation between nitrate levels in a given location in the Gulf and red tide is difficult, as the Karenia brevis organisms devour the nitrates, destroying the evidence.
In addition to working to pin down the culprit or culprits for red tide, additional studies and fieldwork performed by Mitsch’s Everglade-Wetland Research group has found what he told his audience could be a solution to the problem.
“Restored or created wetlands can remove significant amounts of nitrogen and phosphorus from agricultural and storm water runoff and are also significant sinks of atmospheric carbon as well to mitigate climate changes,” noted his report. The method alternates using swampy wetlands as catch basins and crop-producing farms, “flipping” them from one use to the other over a period of years in a process Mitsch called “wetlaculture.”
It’s a long-term solution. To have a significant impact, the process would have to be carried out over vast swathes of land, such as the sugar cane fields that now take up thousands of acres south of Lake Okeechobee. Tom Maish, a member of the Everglades Wetland Research Park Advisory Board, said his group is trying to acquire 500 acres for a major demonstration project. For now, the plan is being tested on a small scale in 27 tubs located at Freedom Park in Naples.
For more information on red tide, to warn of possible outbreaks, and plan your trips on the water or to the beach, you can visit the Collier tourism website, www.paradisecoast.com, highlighting current beach conditions, or call Collier County’s Red Tide Hotline at 239-252-2591 24 hours a day. Signs are posted on public beaches when red tide blooms occur.
Additional reporting by Chad Gillis.