Red Tide and Blue-Green Algae Explained

FGCU Associate Professor James Douglass Gets to the Bottom of the Issue

Water quality is a big deal every summer in southwest Florida, but this year, the blue-green algae and red tide plaguing our local waters have risen to the headlines of the national news cycle and brought a lot of emotions to the boiling point around town. But what exactly is going on? To learn more, I spoke to James Douglass, an associate professor at the Department of Marine and Ecological Sciences at Florida Gulf Coast University.

“Red tide is one type of what they call a ‘harmful algae bloom,’” James says. It’s a microscopic, single-celled algae called “Karenia brevis” that’s part of a group of organisms we call “dinoflagellates.” These cells have two small tails that allow them to move around, even though they’re plants. “When they’re present in abundance, they stain the water red, and that’s what we call red tide,” James says.

But what causes these algae, which are always present in the water in small quantities, to multiply and cause problems? “When they have the right conditions of light, temperature, and most importantly, nutrients, then they start to grow and divide and divide and divide,” James says. Plants like dinoflagellates get their nutrients — namely phosphorus and nitrogen — from dissolved chemicals in the environment, taking them directly out of the water.

This year’s massive red tide has been fueled mostly by “nutrients that have come from man-made sources coming off into the ocean and fueling the red tide,” James says. Fertilizer, such as the kind that enters the ocean as runoff from lawns, as well as human and animal waste, like the kind that comes from seepage from sewage and septic sources, are both major causes. “It’s not necessarily that there’s 100 times more nutrients this year than there was last year,” James says. “They’ve been ramping up year by year, building and building, increasing the odds of a really bad red tide occurrence.” Hurricane Irma resulted in a particularly large dose of nutrients from the land running into the ocean, along with many other factors, resulting in the red tide that’s been killing ocean wildlife.

Of course, as serious as this issue of red tide has become in Florida, the local southwest Florida community is even more worried about the blue-green algae that’s been turning our waters to sludge around town.

As many locals know, the blue-green algae blooms are starting in Lake Okeechobee. Then they move through the Caloosahatchee and St. Lucie estuaries and flow right along with the water. But again, why has it gotten so bad this year?

James didn’t have an easy answer for me, but as with the red tide, he suspects that “the levels of pollution (nutrient based) have continued to increase,” along with weather conditions and other more difficult-to-pinpoint factors. This polluted water usually flows from the Kissimmee River into Lake Okeechobee and then down to the Caloosahatchee and St. Lucie, further spreading the reach of blue-green algae and nutrient-rich water.

So then, what’s the solution? It’s complicated, of course, but James has an idea. “What I would like to see is a return to a more natural situation, more natural flow,” James says. “Because there used to be little or no connection to Lake Okeechobee in the Caloosahatchee River … until about 100 years ago, people dug a canal from the lake into the river.” The same thing happened with the St. Lucie Estuary. “At the same time, they built a dam at the southern end of Lake Okeechobee,” he says, forcing the water that used to flow south to the east or west, making its way to places like Fort Myers. “That central message that people have been repeating — ‘send the water south’ — from a scientific perspective, is a central part of the solution, in my opinion.”

As you can tell, blue-green algae and red tide are incredibly complex issues. If you’d like to learn more, check out the rest of my interview with James Douglass on my YouTube channel Link Below!