Red tide, green algae along Florida’s coasts

Photo credits: Left, dead goliath grouper, Boca Grande Beach. Credit: Jess Zack Breznican, ShutterUp-TN photography. Right, great blue heron hunting over green algae bloom, St. Lucie canals. David Conway.

Looking ahead to the Fourth of July, do you think you’ll be able to fish? Or will pollution along your coast stop you? Seems it’s becoming increasingly common to lament the loss of summer sport and fun in Florida due to red tide and green algae blooms, both of which are going strong this week.

On the southwest coast, a red tide has killed countless fish along the beaches, and on the southeast coast, the discharges from Lake O are now polluting the St. Lucie and Indian River Lagoons with foul green algae.

(The Lake O discharges from the Caloosahatchee on the west coast are also harming the waters there, too.) You don’t want to be fishing in these waters, and if the green algae gets more toxic, as it last did in the summer of ’16, you don’t want to be in, or even near that stuff. Many people have been made ill—even on the beaches—by contact with these waters.

The Lake O discharges are a human-made disaster which continue to wreck the estuaries on both coasts.

It’s without doubt the number one ecological issue in Florida today.

And while the reservoir south of Lake O that is proposed to alleviate some of the damages is still in the planning stages, consider your vote in this November’s election an important chance to voice your opinion on the disaster.

Red tide also has a long history in Florida. This week, the FWC’s red tide status reports:

    “A patchy bloom of the Florida red tide organism, Karenia brevis, persists in Southwest Florida.
    In Southwest Florida over the past week, K. brevis was observed at background concentrations in one sample collected offshore of Pinellas County, background concentrations in one sample collected from Manatee County, background to medium concentrations in 15 samples collected from Sarasota County, medium to high concentrations in four samples collected from Charlotte County, background to high concentrations in 12 samples collected from or offshore of Lee County, and background to low concentrations in three samples collected from Collier County.”

The FWC has online resources, including maps and reports with additional details, on the FWRI Red Tide website. The website also provides links to additional information related to the topic of Florida red tide including satellite imagery, experimental red tide forecasts, shellfish harvesting areas, the FWC Fish Kill Hotline, the Florida Poison Information Center (to report human health effects related to exposure to red tide), and other wildlife related hotlines.

Here is some basic background information on red tide:

What are the basic causes of red tides and historically when were they first recorded in Florida?

FWC’s Spokesperson Michelle Kerr: Red tide is a naturally-occurring microscopic alga that has been documented along Florida’s Gulf Coast since the 1840s. Blooms, or higher-than-normal concentrations, of the Florida red tide alga, Karenia brevis, frequently occur in the Gulf of Mexico. Red tide begins in the Gulf of Mexico 10 to 40 miles offshore and can be transported inshore by winds and currents.

Red tides, also called harmful algal blooms (HABs), occur when microscopic algae multiply to higher-than-normal concentrations, often discoloring the water.

Although more than 50 HAB species occur in the Gulf of Mexico, one of the most well-known species is Karenia brevis, the Florida red tide organism. In Florida waters, K. brevis thrives in high-salinity (salt content) areas but can tolerate a wide range of salinities and temperatures. The species forms nearly monospecific (single species) blooms by outcompeting or excluding other phytoplankton species.

Historically how frequently do red tides as severe as the one in Southwest Florida happening now occur at this time of year?

In other words, is this red tide unusual or does it fit the normal historical pattern for red tides?

Kerr: Karenia brevis (red tide) blooms occur in the Gulf of Mexico almost every year, generally in late summer or early fall. They are most common off the central and southwestern coasts of Florida between Clearwater and Sanibel Island but may occur anywhere in the Gulf. Blooms are less common but do occur along the southeastern Atlantic coast as far north as North Carolina. Most blooms last three to five months and affect hundreds of square miles, but they can continue sporadically for as long as 18 months, affecting thousands of square miles.

FWC first documented the red tide bloom in southwest Florida in November 2017.

Red tides can last as little as a few weeks or longer than a year. They can even subside and then reoccur. The duration of a bloom in nearshore Florida waters depends on physical and biological conditions that influence its growth and persistence, including sunlight, nutrients and salinity, as well as the speed and direction of wind and water currents.

Have a happy Fourth of July!

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