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Drone captures crimson tide of nutrient-laden stormwater flowing from Caloosahatchee post-Ian

Sanibel-Captiva Conservation Foundation

Drone images taken after Hurricane Ian show a crimson tide of nutrient-polluted water flowing from the Caloosahatchee River on its way to the Gulf of Mexico.

The Sanibel-Captiva Conservation Foundation uses the drone to take images of the water coming from the Caloosahatchee River, which moves along the eastern edge of Sanibel Island and winds around Lighthouse Point as it moves into the open Gulf of Mexico.

SCCF has had a special focus on the amount of water that the Army Corps of Engineers releases into the Caloosahatchee River from Lake Okeechobee for years, due to the high levels of nitrogen and phosphorus and other pollutants from residential developments in the Kissimmee and Fort Myers areas, and corporate-sized agricultural fields in the lake’s watershed.

Many believe the Army Corps’ heavy releases of tons of lake water in 2018 into the Caloosahatchee River and through the W.P. Franklin Lock and Dam led to a massive red tide that hung around until 2019, wreaking havoc with the environment, discouraging tourism, and killing fish and manatees.

The drone’s pictures taken on Oct. 10, after the storm made landfall nearby on Sept. 28, show the maroon river water turning the crystal white-blue bay waters dark. Nobody is sure exactly which pollutants in what amounts were in the runoff, but darker water certainly blocks out sunlight, which in turn can kill the all-important seagrass meadows that provide a nursery for juvenile fishes and food for manatees.

SCCF, Calusa Waterkeeper and many other environmental groups in Southwest Florida have been working with the Army Corps to monitor the amount of water, or flow, that comes down the river.

However, these dark waters did not come from Lake Okeechobee.

Environmentalists want the flow to be just enough during the dry season, and not a deluge in the rainy season, to keep the Caloosahatchee estuary system healthy and free of red tide and at the ocean end and blue-green algae in the freshwater parts upriver.

The Army Corps wants to lower Lake O’s water level when necessary to protect the people who live around the lake from flooding caused by a potential failure of the Herbert Hoover Dike surrounding it, and to manage other aspects of the lake’s ecology, while being sensitive to the desires of the environmentalists.

Before-and-after images of Lighthouse Point on Sanibel Island, designed to highlight the huge maroon plumes of nutrient-polluted water pouring from the mouth of Caloosahatchee River into San Carlos Bay, also show a breath-taking scene of destruction the Category 4 storm left on the eastern tip of the island. Trees are stripped bare. A boardwalk is askew. The two historic lighthouse keepers’ cottages are gone, as is a newer white building. The 98-foot-tall Sanibel Lighthouse, first lit with kerosene oil on Aug. 20, 1884, is still standing.
Sanibel-Captiva Conservation Foundation

The day after Hurricane Ian made landfall the flow from the W.P. Franklin Lock and Dam exceeded 24,000 cubic feet per second — more than 11 times the amount considered healthy for the Caloosahatchee estuary.

But no water was released from Lake Okeechobee. All that water, and the nutrient pollution it contained, came from Hurricane Ian’s rains and the subsequent runoff into the Caloosahatchee watershed.

“The flow from the Franklin Lock and Dam sharply decreased following the peak flow but continues to be at damaging levels for our estuary, said Leah Reidenbach, a research and policy advocate at SCCF. “It is unknown how long it will take our system to recover from such a damaging event.”

Calusa Waterkeeper, Inc. a non-profit working to protect water resources throughout greater Lee County has spent years documenting what the group calls “harmful discharges” of water from nutrient-rich Lake Okeechobee into the Caloosahatchee River and out onto the Gulf of Mexico.

"Lake Okeechobee is often referred to as the ‘liquid heart’ of Florida. Unfortunately, over the years, the lake has become heavily polluted by run-off from agriculture and development in Central and South Florida. As it was designed in 1947 to avoid flooding south of the lake, the Caloosahatchee and St. Lucie rivers are the two ‘safety valves’ of the system during high water events. Water from Lake Okeechobee is now routinely discharged to these rivers and sent to tide in the Gulf of Mexico and Atlantic Ocean. This practice is also starving Florida Bay of the freshwater it naturally received through the historic Everglades."
Calusa Waterkeeper

The group also believes releases of “massive amounts of nutrient polluted” water down the Caloosahatchee River exacerbates harmful algal blooms such as red tide, increasing a bloom’s strength and longevity.

Mike Parsons, a Florida Gulf Coast University professor of marine ecology, said the correlations between hurricanes and red tides is nebulous.

“We have no evidence that the hurricanes cause red tide, but hurricanes may make them worse,” he said. “Red tides are a natural phenomenon. We don't start them. We don't influence their start, as far as we know. Between hurricanes and runoff, human activities could be making them worse.”

Parsons said Southwest Florida’s red tides tends to initiate at the end of September or early October, usually around Venice. From there, the blooms often move onshore and can grow larger, and then may drift north or south.

“But when you put a hurricane in there, then things start to get, I guess, interesting would be one way to say it,” Parsons said. “If we have this natural process that happens 90% of the time and then you put a hurricane in there is it coincidental? When the blooms happen right after a hurricane? Or did the hurricane speed up the process or change the process somehow? We don't really know.”

A University of Florida-led study published in Journal of the Total Environment earlier this year backed up Calusa Waterkeepers’ long-anecdotal contention: humans provide fuel for red tides that makes the smelly fish-killing events stronger and last longer.

Environmental researchers led by the University of Florida’s Center for Coastal Solutions documented the link after studying a decade of red tide data from the Caloosahatchee River, Charlotte Harbor, and the surrounding watersheds including the coasts of Charlotte and Lee counties.

“While red tide blooms develop naturally, we took a long view and found evidence that human activity has helped fuel coastal blooms in this estuary to varying extents between 2012 and 2021,” said Miles Medina, lead author of the study and a research scientist at UF’s Center for Coastal Solutions.

Parsons, from FGCU, said finding the links between human activity and red tide blooms has been challenging for researchers because of the complexity of the blooms and the many factors that contribute to them. The UF researchers agree, and pointed out their study is not a straight-forward conclusion because myriad factors go into red tide development and duration.

Environmental reporting for WGCU is funded in part by VoLo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health. 

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