Algae monitored in Okeechobee Waterway

Posted 6/10/20

Special to the Lake Okeechobee News/NOAA Last week, cloud cover made it impossible for NOAA imagery to detect potential for algae blooms in Lake Okeechobee. This image from May 29 shows some low to …

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Algae monitored in Okeechobee Waterway

Posted
Special to the Lake Okeechobee News/NOAA
Last week, cloud cover made it impossible for NOAA imagery to detect potential for algae blooms in Lake Okeechobee. This image from May 29 shows some low to moderate potential for algae on the west side of the lake. Green and blue on the map would show there is some potential for algae in the water column. Bright orange and red spots on the map would indicate a surface bloom.

Once again summer heat has brought seasonal algae blooms in Lake Okeechobee. Fishermen report algae suspended in the water column, especially on the south end of the lake.

Algae and cyanobacteria (commonly called blue-green algae) are part of the lake’s natural ecosystem. The microscopic organisms are always present in all freshwater (unless it is sterile). Excess nutrient loading of phosphorus and nitrogen, little water movement and summer heat set the stage for algae and cyanobacteria to multiply rapidly into a visible “bloom.”

Some of the cyanobacteria common in Lake Okeechobee waterways are capable of producing toxins. According to the U.S. Geological Survey, about 25% of cyanobacteria can produce toxins; however, even cyanobacteria capable of producing toxins do not always do so.

Cloud cover blocked most of the National Oceanic and Atmospheric Administration satellite imagery for Lake Okeechobee last week.

Satellite imagery from May 29 showed light bloom potential on approximately 15% of Lake Okeechobee.

On June 1, South Florida Water Management District (SFWMD) staff sampled the C-43 Canal (Caloosahatchee River) upstream of the Moore Haven Lock and on Lake Okeechobee at the Port Mayaca Lock, a site in the lake in Glades County about 8 miles from the shoreline (FEBOUT) and a site in Glades County about 3 miles offshore (FEBIN). The C-43 sample was dominated by Microcystis aeruginosa and Cylindrospermopsis raciborski, the Port Mayaca and FEBIN samples had no dominant algal taxa, and the FEBOUT sample was dominated by Cylindrospermopsis raciborskii. No cyanotoxins were observed in any of the samples.

On June 2, SFWMD staff collected samples at 15 sites on Lake Okeechobee. SFWMD staff also collected a sample on the C-44 Canal. Microcystis aeruginosa was the most common dominant algal species in these samples, followed by Cylindrospermopsis raciborski. Cyanotoxins were not detected at eight locations. Trace levels of total microcystin were detected at two sites, (0.36 parts per billion and 0.34 ppb), and single-digit concentrations of 2.0 ppb, 3.0 ppb,1.4 ppb, 2.8 ppb, 4.4 ppb and 1.3 ppb at six sites.

On June 3, SFWMD staff collected samples at 10 sites on Lake Okeechobee. Microcystis aeruginosa was the most common dominant algal species in these samples, followed by Cylindrospermopsis raciborski. Total microcystins were non-detect at four sites. Trace levels (0.7 ppb and 0.67 ppb) were detected at two sites. Single-digit levels of total microcystins were detected (8.0 pbb.,1.8 ppb, 2.3 ppb) at three sites. A site about two miles off the eastern shore in Palm Beach County had toxin levels of 27 ppb — the highest observed total microcystin value of all the Lake Okeechobee stations visited last week.

The Centers for Disease Control and Prevention (CDC) considers toxin levels below 8 ppb (8 micrograms per liter) to be safe for human recreational contact.

According to FDEP, it is not possible to tell what species of algae and/or cyanobacteria are present without tests, so they advise people to stay out of water where algae is visibly present as specks, mats or water is discolored pea-green, blue-green or brownish-red. Additionally, pets or livestock should not come into contact with the algal bloom-impacted water, or the algal bloom material or fish on the shoreline.

On June 1, FDEP took a routine sample at Port Mayaca, where water from the C-44 Canal was backflowing into Lake Okeechobee. The researchers noted the gates were open and there was a visible flow of gray-brown water from the canal into the lake, with a light surface chop. Tests on the sample detected mixed algae in the water with no dominant species.

FDEP also tested water in the C-44 Canal at the S-153 structure on June 1. Water from this area has been backflowing into Lake Okeechobee whenever there was rainfall. (The normal level in the St. Lucie canal is 14 to 14.5 feet. When the canal level is higher than the lake level, if the water control structures at Port Mayaca are open, water can backflow into the lake.) In May, flow in that area had a visible algae bloom with Microcystis aeruginosa as the dominant species with a toxin level of 2.1 micrograms per liter. Test on a water sample taken June 1 found mixed algae with no dominant species.

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