'Distinct possibility' St. Lucie River could get algae blooms

Even without Lake Okeechobee discharges, blue-green algae blooms in the St. Lucie River are a "distinct possibility," a marine biologist said Monday.

Heavy rains in Martin County and southern St. Lucie County for more than a week are adding algae-feeding nutrients and reducing algae-thwarting salinity in the river's estuary, said Edie Widder, executive director and lead scientist at the Ocean Research and Conservation Association in Fort Pierce.

All that's needed, Widder said, are some hot, sunny days after the rain finally stops.

From May 13 through 8 a.m. Monday, from 13 to 13½ inches of rain had fallen in western Martin County, said Kevin Rodriguez, a meteorologist at the National Weather Service Station in Melbourne.

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And from May 15 through Sunday, more than 5 billion gallons of water has poured from the C-44 Canal, also in western Martin County, through the St. Lucie Lock and Dam into the St. Lucie River.

The water is not from Lake Okeechobee at the western end of the canal but rainfall runoff, mostly draining off farmland.

More: Are Lake Okeechobee discharges coming?

"The main concern is that we're seeing high levels of nutrients coming into the estuary, particularly from the C-44 Canal," Widder said. "There also are high nutrient levels coming from Ten Mile Creek, the North Fork (of the St. Lucie River) and the C-23 Canal. All that nitrogen and phosphorus could feed algae blooms."

Also startling, Widder said, is the "precipitous drop" in the river's saltiness.

Ideally, the river near Stuart should have a salinity between 15 and 25 parts per thousand.

Monday afternoon, salinity at a LOBO remote-controlled monitor in the river off Stuart was 1.95 parts per thousand. Upstream in the South Fork toward the St. Lucie Lock and Dam, salinity was about 0.15 parts per thousand.

"Microcystis, the type of algae we had during 2016, thrives in fresh water," Widder said. "So with the right set of circumstances, if we get some hot, sun-shiny days and calm winds after all this rain, we could start seeing some algae blooms."

More: Florida issues avoid-water advisories for high bacteria in North Fork of St. Lucie River

Blooms as large as those in 2016, when thick mats of toxic, guacamole-looking algae covered large sections of the St. Lucie, are unlikely, Widder said.

"The situation in 2016 was extremely unusual," Widder said, because the algae traveled from a massive bloom in Lake O, via the C-44 Canal, to the St. Lucie.

More: Are Lake Okeechobee discharges inevitable?

A "homegrown" bloom in the river would more likely be confined to backwaters and bays where the water is still and doesn't get much much flushing from tides.

Historically, the St. Lucie River has not had large-scale algae blooms without Lake O discharges.

More: Scientists agree Lake O discharges caused 2016 algae blooms