Recent headlines appeared to be at odds at first glance to some readers: “Satellite imagery shows bloom ‘potential’ on much of Lake O” and “Lake O among top ten bass fishing lakes.”
How can both stories be correct?
Most of the time, algae is not a problem for fish. Algae and cyanobacteria (commonly called blue-green algae) produce oxygen. They also form the base of the food chain in a lake.
Algal blooms can be a problem for fish in a canal or marina. If a cloudy day causes the algal bloom to die off quickly, this can suck the oxygen out of the water. If the fish can’t swim away quickly enough to escape the oxygen-depleted area, they can suffocate. This can result in a fish kill. Or, if a heavy rainfall pushes a slug of stagnant, oxygen-depleted water into a waterway, it can result in a fish kill.
Lake Okeechobee is a big lake, a very big lake. Algae in the lake are generally in the water column or wispy strands on the surface that are pushed around by the wind. If algae die in one area, fish can usually just swim away.
What about toxins? Some cyanobacteria can produce toxins, but even cyanobacteria capable of producing toxins don’t always do so. The higher toxin levels are most likely in areas such as marinas, canals or water control structures where there isn’t a lot of water movement. According to the Florida Department of Health, if cyanobacteria toxins are present and fish absorb some of the toxins, it accumulates in the liver and organs, not in the part most people eat. FDOH advises rinsing fillets with clean water before cooking the fish. Note that bass tournaments are “catch and release” events so they’re not going to eat those fish anyway.
Most of the algae and cyanobacteria species found in the Lake Okeechobee Waterway don’t produce toxins. According to the U.S. Geological Survey, about 25% of the 28 species of cyanobacteria found in the Lake O Waterway are capable of producing toxins.
We call cyanobacteria blue-green algae, but they aren’t technically algae. What’s the difference between algae and cyanobacteria? Both are microscopic organisms. Cyanobacteria lack a nucleus and mitochondria.
Cyanobacteria are the oldest known life form on the planet. Billions of years ago, they created the oxygen that made life as we know it possible on this planet. They are critical to the ecosystem.
The problems arise when cyanobacteria have too much food. This puts the ecosystem out of balance. Given hot weather, lots of nitrogen and phosphorus and little water movement, the cyanobacteria reproduce rapidly.
Algal blooms may be unsightly to some – I know some scientists who find them beautiful – but they don’t hurt the fishing.
Tournament results show the Lake O fishing has been good so far this year, as evidenced by the Bassmasters report. And while the anglers are happy with their catches, they are concerned about the future of the Big O fisheries. They’re not worried about the algae. They’re worried about the lack of submerged aquatic vegetation (SAV).
SAV is the lake’s natural filter. These plants also provide critical habitat for fish. Hurricane Ian churned the lake, destroying much of the SAV. According to Florida Fish and Wildlife Conservation Service (FWC), there’s only about 2,000 acres of SAV left. FWC and South Florida Water Management District would like to see 40,000 acres of SAV on the lake. Anglers would like to see around 100,000 acres of SAV.
SAV also filters the water, taking up some of the nutrients that would otherwise feed the algae and cyanobacteria.
While the existing SAV is apparently in good condition, there’s not enough of it, and for new SAV to grow, lower lake levels are needed. According to the scientists, lake levels of 12.5 feet above sea level or lower are needed for sunlight to reach the bottom and cause new SAV to germinate. For new SAV to grow, we need at lest 30 consecutive days of a lake level below 12.5 feet. That’s not going to happen this year.
So while the anglers celebrate the good fishing this summer, they’re worried about the future. For new generations of bass to survive and grow into the whoppers of the future, the lake needs more SAV. That means we need the lake to fall below 12.5 feet and give the vegetation a chance to grow.