Florida’s Red Tide Shows Algae Blooms Aren’t Just a Wisconsin Problem


While we were knee-deep in stories about algae problems in Wisconsin’s lakes this summer, a serious outbreak of blooms has been unfolding in Florida where a massive “red tide” is swirling in the waters off both its Atlantic and Gulf coasts. Here in Wisconsin, our potentially toxic bluegreen blooms are caused by cyanobacteria like Microcystis aeruginosa, anabeana and aphanizomenon – all of which can release toxins into the water.
The culprit in Florida’s red tide is a species of marine alga called Karenia brevis which gives the water a rusty hue and can produce toxins that cause both gastrointestinal and neurological problems when swallowed- leading to a lot of dead marine life like fish, sea turtles, dolphins and manatees. Red tide can be a human health threat as well, especially as cells of karenia brevis break open as waves crash ashore, sending their toxins into the air. 

Extent of recent bluegreen bloom on Lake Okechobee. Courtesy: NOAA

Just like our algal issues here in Wisconsin, Florida’s blooms are being fed by human alterations to the landscape. Nowhere is this more apparent than Lake Okeechobee which, earlier this summer, saw a massive bluegreen algae bloom cover 90 percent of its surface. Also similar is the culprit in these massive blooms – phosphorus.
In Lake Okeechobee’s case, heavy rains washed fertilizer from sugarcane fields and manure from dairy farms and waste from home septic systems into the lake. Algae began to take advantage of this influx of nutrients and started growing out of control. 
That bloom in Lake Okeechobee might have stayed a very regional story had humans not re-engineered the entire system. Instead of excess water overflowing south toward (and, more importantly, through) wetland complexes like the Everglades, when Lake Okeechobee’s water levels get too high, the water is now diverted by the Army Corps of Engineers via a series of canals and spillways. Some heads east, to the Atlantic Ocean and some heads west, to the Gulf of Mexico. This water is also elevated in nutrients and, when those nutrients end up in the ocean, they can feed other bacteria and algae – including the cause of red tides, karenia brevia.
While research is ongoing about how much any one part of this puzzle is responsible for causing red tides, it’s safe to say that phosphorus runoff and the discharge from Lake Okeechobee plays a big role and that tackling the problem will involve protecting water quality upstream before it ever makes it out to sea. 
In the meantime, Florida residents can do what a lot of us have done this summer – wait for algal blooms to pass and try to enjoy the water when it is swimmable. 
A red tide approaching the Texas coastline. Photo: P.Schmidt, Charlotte Sun

Of course, not everyone is a fan of waiting it out. And it should be noted that this summer is scheduled to go down as the 4th-hottest on record, so we’re likely to see more big algal blooms in the future as waters continue to warm.
The good news is that, if we can find a way to put a lot less phosphorus into our water, we can greatly reduce the frequency and severity of harmful algal and bacteria blooms. The bad news is, it isn’t going to be easy.
Climate change is rapidly warming our waters and increasing the extreme rain events that carry so much phosphorus and nitrogen into our waterways. Meanwhile, social change is slow. While science can help show us the results of our decisions and land-use practices, nothing changes until we act on that information. Maybe Florida’s red tide can serve as the call to action. 
To read more about the science of harmful algal blooms, check out this great page from USGS. 

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