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Experts: Irma strained state’s ecosystems

November 29, 2017
By JESSICA SALMOND (jsalmond@breezenewspapers.com) , Lehigh Acres Citizen

Florida's Everglades and connected ecosystems are fighting battles on all sides.

Artificial re-routing of Lake Okeechobee overflow from south to east and west, and the extremes in weather patterns are straining the delicate and complicate systems in southern Florida.

The Sanibel-Captiva Conservation Foundation held a panel discussion on Nov. 14 to update the community on water conditions in the local estuary and watershed system, as well as talk about the in-the-works steps to address issues in the Everglades.

The issues are all connected: A dike had been built in the 1920s around Lake Okeechobee and more had been added in 1947, after a hurricane caused severe flooding in southwest Florida. Then state and federal government began the Central and South Florida Flood Control Project, working to protect development from the river of grass. The Caloosahatchee and St. Lucie Rivers became the recipients of excess water in the lake. The rivers were also altered to help form the Okeechobee Waterway, a federal commercial route through the center of the state. The Caloosahatchee was expanded, deepened and renamed the C-43 canal, and locks were installed to engineer the flow of the river.

"It's not even called a river," said Eric Milbrandt, director of the marine lab at SCCF.

Fast forward to this year, and the lake, rivers, and connected ecosystems have gone through cycles of suffering. And, with 2016's intense rains, followed by an intense drought, followed by more rains and then a hurricane, Florida's had a rough couple years.

"This was an extraordinary year," said Rae Ann Wessel, director of policy at SCCF.

The local systems have been trying to recover through the extreme variabilities in the season, extremes that could become frequent and less average in-betweens.

"The signature of climate change is having more frequent extremes, like drought and deluge," she said.

After Irma, Lake Okeechobee hit record levels of 17.2 feet, the highest it has been since 2005. The Army Corps of Engineers manages the lake; typically it's kept between 12.5 and 15.5 feet to protect the Herbert Hoover Dike.

That led to record releases of fresh water into the Caloosahatchee and out into the Gulf between Sanibel and Estero islands - and SCCF's research team is already seeing the effects. Before human engineering altered the ecosystem, the Caloosahatchee started mixing with tidal saltwater more than 40 miles upstream. Now, the Franklin Lock cuts off that natural ebb and flow and the mixing occurs closer to the mouth of the river. Wessel said this mixing area is important because it creates a nursery for a myriad of species. However, the flood of freshwaters this fall have pushed that mixing zone beyond the mouth.

It's part of why people have reported seeing "root beer" colored water, or dark water, on the beach. Wessel said it's typical to see darker colored water in the river around Iona, as the tannin-dyed hue is a signature of the Caloosahatchee. But the dark water now is different. It's not just tea-colored, it's opaque.

The dark water now is carrying colored, dissolved organic matter and sediments that are blocking sunlight, and the flush of freshwater from Lake Okeechobee is pushing that dark water out onto the sandy white shores. It's preventing photosynthesis from occurring in the aquatic plants below, as well as reducing the needed salinity levels.

"We're seeing sea grasses that are covered in barnacles. I've never seen that before," Milbrandt said. "They're not growing."

Milbrandt said the barnacles are an indication that the seagrass is stressed from too much freshwater and dark water, and is now growing too slowly to shed the barnacles.

The aquatic vegetation is dealing with lower oxygen levels in the water, and unlike fish, they can't just swim away to better waters. That's why in the weeks following the hurricane, beaches on Sanibel and Fort Myers Beach were seeing a lot of detritus washing onshore.

Florida Bay, the area at the southern tip of the state's peninsula, is also struggling. It used to be the mouth of the slow-moving river of the Everglades, but as the Everglades have been starved of water, so too has the bay become more and more saline instead of its needed brackish content.

The Everglades were so dry from April to June this year, the peat soil began to crack and burn, said Stephen Davis, a SCCF ecologist. The soil gets so dry, it can oxidize and disappear.

"During the wet years, Florida Bay ekes by," he said.

Florida Bay serves an important role in the life cycles of much marine life, as it is a nursery for fish and shrimp, which help feed larger predators.

In 2015, the lack of freshwater and a drought lead to fish kills and mangrove and seagrass die-off. The dead materials in the water further reduced the oxygen levels. Davis said the tumultuous rains in 2016 led to a short recovery period, but that rebound was squelched by the following drought. At one point, the salinity levels in Florida Bay measured higher than seawater. Now there are algal blooms visible from satellite imagery drifting from Florida Bay down past the Keys.

This algae material is not necessarily the same type of toxic cyanobacteria that occurred on the east coast in 2016; however, excessive algae in the water causes a multitude of issues for marine life.

 
 

 

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