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Cyanobacteria from 2016 Lake Okeechobee Harmful Algal Bloom Photo-Documented

Microscopic image of Dolichospermum circinale - bar is 10 micrometers in length
This microscope image shows Dolichospermum circinale, which was one of the 28 species of cyanobacteria USGS scientists discovered during the major harmful algal bloom that hit southern Florida last year. Many varieties of the cyanobacteria found in the bloom are capable of creating harmful toxins. Photo Credit: Barry H. Rosen, USGS.

New report provides photographic documentation and identification of the cyanobacteria present in Lake Okeechobee, the Caloosahatchee River, and St. Lucie Canal during an extensive algal bloom in 2016.

Harmful algal blooms (HABs) include numerous species of algae and bacteria including cyanobacteria, which are also known as blue-green algae. HABs produced by cyanobacteria (cyanoHABs) pose a range of health risks to humans, wildlife and companion animals.

Lake Okeechobee, the largest inland lake in Florida frequently experiences HABs. Starting May 2016, there was an extensive cyanoHAB in Lake Okeechobee, which didn't start to dissipate untill the end of July. High water levels during that time resulted in transport of algal-laden water from the lake to coastal areas through a series of canals and rivers, which resulted in beach closures in several Florida counties.

Aerial photograph of a 2016 cyanobacterial bloom on Lake Okeechobee, Florida
Cyanobacterial blooms, such as the one shown that occurred in 2016 on Lake Okeechobee, Florida, can release toxins. Photo Credit: Nicholas Aumen, USGS.

While the algal blooms have been observed in the lake, little is known about the types of algae present during the blooms. It is important to understand the composition of the algal community, as some cyanobacteria can produce a variety of cyanotoxins, including neurotoxins and hepatotoxins such as anatoxins, cylindrospermopsins, and saxitoxins, in addition to microcystins and other potentially harmful metabolites.

In this study, scientists collected samples prior to, during, and after the extensive 2016 cyanoHAB event in Lake Okeechobee. The study report provides digital photographic documentation and taxonomic assessment of the cyanobacteria present in study samples. The majority of the images were of live organisms, allowing capture of their natural pigmentation.

Scientists identified 28 different types of algae in Lake Okeechobee, the Caloosahatchee River and the St. Lucie Canal. In addition to the dominant organism, Microcystis aeruginosa, several other cyanobacteria known to produce toxins were present at lower numbers.

This study is part of a larger effort of the U.S. Geological Survey (USGS) Environmental Health Mission Area to provide information that will help land managers to understand how to effectively minimize potential risks to the health of humans and other organisms exposed to cyanotoxins and other biogenic toxins through recreational, drinking water, and other exposure routes.

This study was funded by the USGS Priority Ecosystem Study Program and the USGS Toxic Substances Hydrology Program.

Reference

Rosen, B.H., Davis, T.W., Gobler, C.J., Kramer, B.J., and Loftin, K.A., 2017, Cyanobacteria of the 2016 Lake Okeechobee and Okeechobee Waterway harmful algal bloom: Open-File Report 2017-1054.

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