Finding pollution sources in canal could help rivers and Indian River Lagoon
ST. LUCIE COUNTY — The search for sources of water pollution is getting downright dirty.
Scientists at Fort Pierce-based Ocean Research & Conservation Association are scooping up and studying muck at the bottom of the C-24 Canal in St. Lucie County to determine the source of contaminants that cause environmental devastation to Treasure Coast waterways.
Through the end of October, ORCA staffers will be getting water and muck samples from 75 sites along a 15.5-mile stretch of the canal, mostly in areas where ditches dump water into the canal. What they find here will be indicative of how canals, creeks and ditches that send stormwater through residential and agricultural areas end up polluting the Indian River Lagoon and rivers like the St. Lucie and St. Sebastian.
The C-24 Canal was chosen for the study because its upper half is lined with agricultural fields, mostly cattle pastures and citrus groves — both active and fallow; the lower canal cuts through the suburban sprawl of southern Port St. Lucie.
That obvious shift from agriculture to suburbs makes it easier to determine which land use contributes the most pollutants to the St. Lucie River. Results of the water and muck tests, expected in mid-November, also should show which particular farms and/or subdivisions are pollution "hot spots."
Those tests are looking for fertilizer nutrients, particularly nitrogen and phosphorus, that drain into the canal and then into the St. Lucie River and Indian River Lagoon. The nutrients feed algae blooms, some of them toxic, in the river and lagoon. This summer, algae bloomed into thick, foul-smelling mats that choked sections of the river and drew international attention.
The research is paid for by a $625,000 grant from Scotts Miracle-Gro, the world's largest dealer of lawn fertilizer. Scotts CEO Jim Hagedorn has a home on the St. Lucie River in Stuart.
Because a pollution study paid for by a fertilizer company could be seen as "the fox guarding the henhouse," ORCA lead scientist Edith "Edie" Widder acknowledged, an independent committee of local scientists, environmentalists and government representatives is overseeing the research every step of the way.
The committee is scheduled to to review and approve the final report Jan. 23. It will be released to the public Jan. 25 at a reception at Pelican Yacht Club in Fort Pierce.
"There it is," said Chloe Lloyd, an ORCA researcher. "There's the black mayonnaise you hear people call muck."
Using a hinged metal box attached to the end of a metal pole, a device affectionately known as "The Clam," ORCA researcher Retta Rohm had just pulled a scoop of muck from the bottom of the canal. Lloyd, wearing rubber gloves, dug the muck out of the scoop and jammed it into marked jars.
The pair had already taken water samples from the site and used a graduated pole to measure the muck depth. At this site just downstream of the Oak Hammock Park boat ramp, it's nearly 20 inches deep. That's pretty bad, but Lloyd said she's found muck more than 3 feet deep. Muck at the second site is a scant 4 inches deep.
ORCA's research will help determine how many nutrients hide in muck at the bottom of the water.
KNOW YOUR MUCK
Have you ever seen a powerboat cruising through the St. Lucie causing a chocolate-brown wake? That's the muck from the river bottom churned up by the boat's propeller.
Muck kills the sea grass in the river and lagoon by blocking out light, and literally chokes oysters to death by denying them oxygen. Studies in the river and lagoon by the Smithsonian Marine Station in Fort Pierce for the past 15 years have found only one type of clam and one species of worm that can tolerate the muck.
The plumes of discharged water going out through the St. Lucie Inlet is muck too, settling on and smothering coral reefs.
Muck in the St. Lucie River has two sources:
· It occurs naturally, beginning as eroded soil fine sediment, much finer than sand.
· The river has always had muck, but the amount exploded when the estuary's watershed expanded exponentially with the construction of canals to drain large areas of western Martin and St. Lucie counties and discharge excess water from Lake Okeechobee.
More than 1 million pounds of suspended sediments — muck in the making — has flowed from the C-24 Canal into the St. Lucie River so far this year, according to South Florida Water Management District data compiled by Gary Goforth, a Stuart environmental engineer and former water district engineer.
That's dwarfed by the nearly 50 million pounds of sediment dumped into the river along with 205 billion gallons of Lake Okeechobee water in discharges that started Jan. 30.
Muck also forms when floating plants die and sink to the river bottom.
That's what happened when the thick mats of blue-green algae that choked parts of the river this summer died. A lot of that algae was toxic, and the toxins were released when the algae died.
No one knows how much muck is in the estuary. Estimates run from around 15 million cubic yards to around 50 million cubic yards. It's up to 15 feet deep in several places, especially where the water is wide, deep and slow-moving, so that suspended sediment can drop to the river floor.