Tyler Treadway

The (Stuart, Fla.) News

JUPITER ISLAND, Fla. — Rainfall runoff and Lake Okeechobee discharges since Hurricane Irma hit Florida last month have turned miles of Atlantic beaches and Indian River Lagoon waters the color of coffee.

Indian River, St. Lucie and Martin counties in Florida — given the moniker Treasure Coast because of tons of treasure left on the ocean floor when Spanish ships sunk during hurricanes — always has felt the brunt of strong storms and lots of rain in early fall, said Grant Gilmore, a marine biologist who has studied life in the lagoon for more than 40 years.

"What's worse than the color of the water is what's in the water," said Gilmore, lead scientist for Estuarine, Coastal & Ocean Science in Vero Beach, Fla. "The chemicals (from crops and lawns) kill the plankton in the (St. Lucie) river and lagoon that all the fish depend on for food."

The fish can flee and some see an influx of brown water each fall as a signal to head to the ocean to spawn, he said. Oysters and sea grass can't leave, and they're dying because the influx of fresh water lowers the salinity they need to survive.

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"There's been basically no salinity in most of the St. Lucie River since the hurricane four weeks ago," said Vincent Encomio, a researcher at Florida Oceanographic Society in Stuart, Fla. "We're at the threshold of high mortality."

As go the oysters, so go many other marine species in the river and lagoon.

"Oysters are a keystone species," Encomio said. "They provide habitat for a lot of other species, most of them other species that have the same need for salty water."

Encomio also works with the Smithsonian Marine Station in Fort Pierce, Fla., to study mussels in the river and lagoon.

"But when we went out to collect mussels for the study, they were all dead," he said.

Extra-high tides that threatened to flood low-lying areas along the St. Lucie River last week actually did the oysters a favor by pushing more salt water into the river.

"The so-called king tides helped a little in the lower part of the river," Encomio said. "But it's just not enough."

The brown water could spur blue-green algae growth in the river although probably not to the extent of massive toxic blooms that blanketed the St. Lucie River last year, he said.

"The big difference from last year is that there's not a big bloom out in Lake Okeechobee that's being brought to the river by the discharges," Encomio said.

But the conditions needed for a bloom — low salinity, warm water, sunny days and lots of nutrients in the water — are all in place.

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Good news: The dirty water shouldn't impede sea turtles crawling onto beaches to nest or their hatchlings heading into the water, said Niki Desjardin, senior scientist at Ecological Associates, a Jensen Beach, Fla., firm that monitors turtle nesting along the Treasure Coast.

"Water quality changes from time to time, so the turtles are used to it," she said.

Follow Tyler Treadway on Twitter: @tcpalmtreadway