Is the Caloosahatchee heading for an algae bloom?

Had they stared into a shaft of sunlight piercing the Caloosahatchee River on Thursday morning, boaters at the Alva dock might have seen spangles, as if the water were dusted with green micro-confetti.

Alas, nothing so festive is likely in store for the waterway, which is ripe for a cyanobacteria bloom, river-watchers worry.

A number of things point to a looming explosion of the one-celled organisms commonly called blue-green algae, many species of which occur naturally in Southwest Florida fresh water. Though they’re critical to natural systems, when they multiply, they can be trouble.

Some species produce toxins that cause health problems in people and animals ranging from itchy eyes and sneezing to liver failure ‒ even death, if ingested in sufficient amounts.

What can trigger blooms? High temperatures, still conditions and water polluted with nitrogen and phosphorus. Those fertilizing elements encourage the blooms, according to the Environmental Protection Agency: “Nutrient pollution from human activities makes the problem worse, leading to more severe blooms that occur more often.”

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Thanks to 19^th- and 20th-century human engineering, the Caloosahatchee is connected to a major source of nutrients: Lake Okeechobee, which happens to have its own full-blown algae bloom at the moment. The U.S. Army Corps of Engineers, which manages the lake, is currently releasing 1,891 cubic feet of lake water per second (about 850,000 gallons per minute) into the river.

That should come as no surprise, says Florida Gulf Coast University Professor Barry Rosen, a renowned algae scientist.

He lists what he calls “perfect conditions” for algal proliferation there: “The temperature’s right, there are the nutrients in the lake, it's been real calm … and (algae) like it that way."

This week, satellite photos from the National Oceanographic and Atmospheric Administration showed an intensifying bloom near the lake’s southwest shore that covered some 260 square miles – more than a third of the 730-square-mile lake’s surface.

From Ralph Arwood’s pilot seat, the lake looks really bad. Arwood, who flies watershed reconnaissance for the nonprofit Calusa Waterkeeper, was at the lake Monday, shooting photos and video over its south and west portions.

“There were cyanobacteria blooms all over the area we flew,” he reports.

The size and rapid intensification of the lake bloom over the past couple weeks of the lake is worrisome, says Jason Pim, a Waterkeeper volunteer. Summer weather might help, but for now, Pim says “It's too early to tell how the rainy season will play out. If its starts raining right away, that would not be good for potentially larger discharges from the lake to the Caloosahatchee.”

These late-spring/early summer surges are becoming a trend, he notes: “It's concerning to see the lake firing up a bloom each year as soon as it gets hot and sunny enough, despite the arrival of rainy season and big inputs (or rainwater) into the lake.

All of this underscores what the data show, he says: The lake itself already had all the nutrient pollution necessary to support a bloom, regardless of what water managers do with inputs into it. Plus, he says, “There's enough legacy phosphorous already in the lake to support blooms for decades, and in my view we must do something much more substantial to address the lake muck bottom.”

What does this bode for the Caloosahatchee? Nothing good, some worry.

Already Pim says they’ve gotten a report of a small bloom in an upper Caloosahatchee canal, though so far, the Sanibel-Captiva Conservation Foundation's real-time River, Estuary and Coastal Observing Network sensors haven’t caught any algae in the river.

Because the sensors are some 2 meters deep, they wouldn’t detect a surface bloom, wrote research scientist Rick Bartleson, who works at the foundation's marine lab, but he and his colleague will continue to keep a sharp eye on conditions.

The Florida Department of Health has posted two red alert algae warnings on the Caloosahatchee: one at the Moore Haven lock and the other in Hendry County. In Lee, there's a single cautionary alert in Fort Myers Shores.

As far as Rosen’s concerned, given what might be brewing, now’s the time to get out on the river.

“I wouldn’t wait – if you want to do it, do it, because it’s likely to get worse,” he said.