Source: Orlando Sentinel
Lakes Apopka and Minneola get new help in battles against algae plagues
The suffering Lake Apopka and the swimmable Lake Minneola bear little resemblance to each other, but they have been provided a fresh course of help recently to fight off their common scourge, harmful algae thriving on water pollution.
Less than 5 miles apart, Lake Minneola next to Clermont and Lake Apopka on the border of Lake and Orange counties are at different stages in their algae battles. The treatments they received in mid-December are promising but unproven.
“We’ve put ourselves on a bit of a new learning curve,” said Dean Dobberfuh, a state water manager, referring particularly to a project at Lake Apopka.
“With these new infrastructure projects, we do a lot of modeling up front about where to put them, how to operate them and what we think will happen,” Dobberfuh said. “But the real world often doesn’t work like models.”
Reducing Lake Apopka pollution
At 50 square miles and the state’s fourth largest lake, Lake Apopka’s pollution and algae troubles are among the worst in Florida. They stem largely from decades of discharges from nearly 28 square miles of farms at the lake’s north side.
That farmland, which originally was part of the lake as open water and wetlands, is no longer cultivated and is owned by the state as a natural area in recovery.
While much of that property is celebrated as a marshy, bird-watching paradise, it continues to be a source of polluted water for the lake. The key pollutant is phosphorus fertilizer – basic nourishment for crops, aquatic plants and the algae that has plagued the lake for decades.
By the 1960s, Lake Apopka had become infamous as Florida’s most polluted large lake and many restoration measures since then have been implemented.
In December, the St. Johns River Water Management District, a state agency responsible for water resources in Central Florida, undertook another measure by replumbing a portion of the levees, ditches, culverts and dam gates built originally by farmers.
The goal of the $2.2 million project is to provide more ability to move around water, coming primarily from rain, within the vast tract of former farms and to lessen the amount discharged to Lake Apopka. That would reduce the amount of phosphorus pollution going into the lake by an estimated several hundred pounds annually.
Having more ability to manage depths and flows of water on the former farmland would also provide more ability to enhance the emerging mosaic of natural wetlands. But trying to assist nature with artificial structures can have unpredictable results, said Dobberfuh, a water management district bureau chief for water resources.
“It’s not turnkey,” said Dobberfuh of the project to be completed next summer. “We don’t get to the end of the rainbow instantly.”
Also at issue is the lingering presence of now-banned pesticides in former farmland soil. The toxicity and extent of those pesticides were unknown in 1998, when a large die-off of birds occurred that was linked to the pesticides.
Some pesticide hot spots were dug up and hauled away and others were buried deeply under cleaner soils. The low levels of toxicity remaining on the former farmland have been deemed safe for ecological functions but not for human ingestion.
The 30,000-acre lake remains separated from the 18,000 acres of former farmland by a levee built by farmers.
The presence of pesticides is another reason the water district wants to limit as much as possible the amount of water discharged from the former farmland to the lake.
“We are trying to recover the bass fishery in the lake,” said Erich Marzolf, division director for water and land resources at the water management district. “Right now, people can fish on the lake and eat what they catch. We absolutely do not want people fishing on the north shore because we are not convinced the fish are clean enough for human consumption.”
Stopping Lake Minneola’s algae
At Lake Minneola, the challenge of water pollution and algae is just as vexing as at Lake Apopka, although circumstances are vastly unalike.
At nearly 2,000 acres, Lake Minneola is only about 5 percent as large as Lake Apopka but has been hugely popular for swimming, boating, skiing and competitive events, such as triathlons.
It is also naturally dark and slightly acidic, conditions that usually discourage the growth of algae. But early this year, the lake erupted with a thick layer of green algae in the worst known such outbreak for Lake Minneola.
The outbreak, or bloom, lasted through much of March and consisted of blue-green algae, also known as cyanobacteria, which can produce toxins harmful to people.
The water management district contracted this summer with an Israeli company, BlueGreen Water Technologies, for a $1.7 million pilot project to last at least a half-year in demonstrating an ability to control blue-green algae.
On Nov. 16 and Dec. 16, BlueGreen Water Technologies applied an algicide consisting of tiny beads of encapsulated hydrogen peroxide that drift and dissolve slowly, killing blue-green algae.
“We identified a build-up of cyanobacteria cells,” said Eyal Harel, co-founder and chief executive officer of BlueGreen Water Technologies. “When I say build-up, this is not a bloom. Our mission is to prevent blooms in Minneola altogether. So we treat the water locally and surgically to reduce the cell density.”
The treatments were performed by a Clermont environmental consultant, Modica & Associates.
Using a small boat equipped with an applicator, nearly 5,000 pounds of dry, granular algicide was applied along the lake’s north shore in November. Nearly 14,000 pounds was applied in December to three areas of the lake along the north and south shore, and a section across the middle.
Signs were posted at Clermont’s boat ramp, stating “Algal Remediation Treatment in Progress.” There are no restrictions on swimming or other recreation during treatments.
“The amount of hydrogen peroxide in the water is very low,” Harel said. “The time-release mechanism makes sure that at any given time only a fraction of the active ingredient is available in the water.”
What’s possibly feeding the growth of algae, including fertilizers, storm water or septic tanks, is under investigation, with findings expected by late 2021.
Ron Hart, executive director of the Lake County Water Authority, unraveling the cause is important for long-term strategies for preventing algae growth.
“The treatments may do something to address what’s happening today,” Hart said. “But we need to eliminate the causes otherwise we will need to treat algal blooms for perpetuity.”