OKEECHOBEE — The summer heat continues to contribute to ideal conditions for the growth of algae and cyanobacteria (commonly known as blue-green algae). The Florida Department of Environmental Protection (FDEP) and the South Florida Water Management District monitor algae conditions in the lake with regular sampling and testing. These established test sites have been given designations.
Okeechobee, Glades, Hendry, Palm Beach and Martin counties each contain part of Lake Okeechobee. The county boundaries divide the big lake like an unevenly sliced pie with Palm Beach County claiming the largest slice and nearly one-third of the lake’s territory.
The point where the county lines meet is near the L008 test site.
The LZ40 test site is near the center of the lake, in Palm Beach County’s zone.
The L004 test site is about 6 miles west of Port Mayaca in Martin County’s part of the lake.
On June 30, SFWMD staff collected follow up samples at microcystin hot spots (L004 and LZ40) identified during last week’s Lake Okeechobee monitoring. The locations were sampled both near the surface and near the bottom of the water column. The L004 near surface sample was dominated by Microcystis aeruginosa and had 1.3 ppb total microcystin. The L004 near bottom sample was also dominated by Microcystis aeruginosa and had trace levels (0.53 ppb) of total microcystin. The LZ40 near surface sample was dominated by Microcystis aeruginosa and had 99.25 ppb total microcystin and the LZ40 near bottom sample had no dominant algal taxon and trace levels (0.28 ppb) of total microcystin. The Environmental Protection Agency considers toxin levels below 8 ppb to be safe for human recreational contact.
While the LZ40 sample had toxin levels more than 10 times than the level EPA considers safe, it was an improvement from the previous week. On June 24, the LZ40 site had 290 ppb. The tests also showed that toxin levels were highest in the surface bloom.
Cyanobacteria and algae can be on the surface or in the water column
Cyanobacteria can inflate and deflate gas vacuoles to rise and fall in the water column to take advantage of heat and nutrient conditions. A “bloom” on Lake Okeechobee may be spotted early in the morning and disappear a few hours later.
Algae, also found in the water column, may float to the surface buoyed up by oxygen gas bubbles produced during photosynthesis.
According to “Plant Management in Florida Waters” by the University of Florida Institute of Food and Agricultural Services (UF/IFAS): “Algae are in the plant kingdom, but technically they are not plants. A diverse group of organisms, algae survive in even the harshest habitats. From the dry desert, to the Arctic Circle, to boiling springs, these organisms have found a way to extract enough from their environment to live. Algae range in size from microscopic to meters long and from single-celled to complex organisms that rival large plants. These organisms may look like true plants, but unlike plants, algae do not have roots or true stems and leaves.
“In Florida’s freshwaters, algae are what make the water green. Green water is not necessarily undesirable, and neither are algae. In fact, algae are essential to the ecosystem and to life as we know it. Algae are a primary component of the food web, providing food for all types of animals, including fish, insects, mollusks, zooplankton (microscopic animals) and humans.
“There are microscopic algae, like phytoplankton; and there are macroalgae, visible to the naked eye. Algae occur naturally in all types of systems and can indicate the condition of an ecosystem. The mere presence of a species can indicate the amount and type of nutrients present.
“In Florida, chlorophyll (an indicator of algae presence) concentrations of more than 40 micrograms per liter are called an ‘algae bloom’ or ‘algal bloom.’ Algae blooms occur when algae grows quickly and densely, often in warm, nutrient-rich waters.”