Task force wants more lake testing

Posted 7/3/19

FORT MYERS — Comprehensive testing of the lake water and sediment is needed in order to find the most efficient ways to reduce the blue green algal blooms in Lake Okeechobee, according to …

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Task force wants more lake testing


FORT MYERS — Comprehensive testing of the lake water and sediment is needed in order to find the most efficient ways to reduce the blue green algal blooms in Lake Okeechobee, according to discussion at the Blue Green Algae Task Force’s second meeting, held July 1 in Fort Myers.

“The challenges with regard to water quality and algal blooms are pretty big. We’re doing our best to address them,” said Florida State Science Officer Dr. Tom Frazer.

He said the Florida Department of Environmental Protection has set a maximum target load for phosphorus entering Lake Okeechobee, but controlling the phosphorus may not be enough to stop the algal blooms. Things are changing in the watershed. “A thousand people move to Florida a day,” he said.

“Other nutrients in the watershed are possibly, very likely, linked to the algal blooms we see in Lake Okeechobee today,” said Dr. Frazer.

The Blue Green Algae Task Force includes Dr. Evelyn Gaiser, Florida International University (who participated in the meeting via phone); Dr. Wendy Graham, University of Florida; Dr. Michael Parsons, Florida Gulf Coast University; Dr. Valerie Paul, Smithsonian Marine Station, Fort Pierce; and, Dr. James Sullivan, Florida Atlantic University Harbor Branch.

The panelists were provided with a lengthy list of projects already identified for the Lake Okeechobee Basin Management Action Plan (BMAP). Some projects are already completed. Others are under way. Dr. Frazer said about nine or 10 are in the planning phase. He asked the panel to prioritize projects on the list and to suggest other projects.

The current Lake Okeechobee BMAP is expected to reduce an estimated 40 percent of the excess phosphorus load entering the lake, he said.

He said in his executive order, “the governor has requested that we update the Lake Okeechobee BMAP by mid-January 2020.”

“We know that we have gaps to fill. We will have public hearings with stakeholders to get new ideas,” he said.

“BMAP will need projects and programs that will reasonably show we can meet the TMDL in 20 years.”

Thomas Frick, director of the Division of Environmental Assessment & Restoration, Florida Department of Environmental Protection, said they know that despite the fact that some projects in the Lake Okeechobee BMAP have been completed, the phosphorus isn’t trending downward.

Dr. Graham noted the most recent average phosphorus load into Lake Okeechobee is 640 metric tons per water year, when the target is 140 metric tons — including 35 metric tons of atmospheric phosphorus (from direct rainfall into the lake).

Mr. Frick said they want to prioritize projects to get the “biggest bang for the buck” but added that “in some of these sub-watersheds, you are going to need a lot of little projects that collectively reduce the nutrients or help with the delivery of the water coming off that sub-watershed.”

He said they pay special attention to the areas that have the highest concentrations of nutrient load and the areas closest to the lake.

He said most of the nutrient load comes from the north, but there are contributions coming from the south, and also from the east and west. He said all projects that clean water before it goes into Lake Okeechobee could be considered part of the plan.

“We know that phosphorus and chlorophyll are connected,” said Mr. Frick. “In regard to phosphorus loading into the lake, it’s certainly not going down.

“In Water Year 2018 (May 1, 2017 - April 20, 2018), we had a very wet year. The increased load in nitrogen was essentially doubled,” he said. “We need to know why that nitrogen load doubled, the sources for that.”

Dr. Paul said the nutrient load issues and blue green algal blooms are happening around the world. She said they need to know more about the data gathered for Lake Okeechobee.

“The target of sampling that is done is at a very course level and it just looks at chlorophyll,” said Mr. Frick.

“The taxonomy is spotty,” he said. “We’re actually going in and looking at the blue-greens during the blooms. We don’t have what is happening up to the blooms. During the blooms we’ve switched to trying to figure out what is there.

“The big thing there is we don’t have a large range of the data to get to that question,” said Mr. Frick.

He said SFWMD and FDEP do water sampling, but it’s just not enough. Water sampling should be done not just during the blooms, but up to it, and even when we aren’t seeing blooms. He said they should look at species compositions and chemical compositions.

Dr. Sullivan said they should also look not only at the level of nitrogen present but the species of nitrogen.

“We need the before data,” he said. “We need the environmental trigger.”

Once a bloom occurs, the trigger has already happened, he said, Environmental data, such as water temperature, should also be documented.

“We might want to pay more attention to the sediments too,” he said. “Microsystis goes down into the sediments during the winter and is there to come back up.

“When Microscystis blooms get large, it changes the pH in the water,” Dr. Sullivan said. A change in pH causes the nutrients in the sediment to be released into the water column.

“The bloom starts feeding itself,” he said.

He said all of this data is needed desperately for Lake Okeechobee for the scientists to understand what is going on and what is environmentally driving the algal blooms.

“With warmer winters, these blooms could be longer,” said Dr. Paul.

“We need to think pretty hard what an in-lake monitoring network would look like,” said Dr, Frazer. It should include spatial and temporal monitoring of species, taxonomic composition of the phytoplankton, key environmental factors, temperature, pH, oxygen level and an index of Microcystis abundance in the sediments.

Dr. Graham said some existing monitoring could be adapted. “There is a lot of good monitoring going on,” she said.

Dr. Frazer said at the next task force meeting they will bring back information on existing monitoring so they can come up with a plan for the level of monitoring they agree they need.
“We can nail down the monitoring, I think,” said Dr. Frazer.

Dr. Sullivan said that while every lake is not the same, “there is a lot of existing experimental and environmental data out there.
“It’s not just a problem in Lake Okeechobee.

“Perhaps working with those scientists and looking at that data would be relevant to do.”

“Sediment is something that has not been tested,” said Dr. Frazer. There is a theory that sediments in the lake have changed profoundly in the last decade or so.

“The focus today is largely on nutrients that are entering the lake by surface waters. We have legacy loads in the watershed north of the lake and we also have legacy loads in the lake itself,” he said.