Rapidly rising lake could damage SAV

Posted 8/25/19

FDEP report: Lake water samples have no toxins

LAKE OKEECHOBEE — Recent rainfall in the watersheds north and east of Lake Okeechobee have sent billions of gallons of water into the lake, causing …

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Rapidly rising lake could damage SAV


FDEP report: Lake water samples have no toxins

LAKE OKEECHOBEE — Recent rainfall in the watersheds north and east of Lake Okeechobee have sent billions of gallons of water into the lake, causing it to rise quickly … maybe a little too quickly for the lake’s recovering submerged aquatic vegetation (SAV).

Lake Okeechobee News/Richard Marion
A colorful summer sunset reflects on Lake Okeechobee. The big lake has been rising rapidly in recent weeks, due to heavy rainfall in the basin north of the lake. The basin that drains into Lake Okeechobee stretches all the way to Orlando.

Anglers on both ends of the lake are concerned the lake could rise too fast and drown out the new SAV before it is well established.

Nature intended water to sheet flow slowly into the big lake. According to the U.S. Geological Survey, before the canals were dug and the Kissimmee River channelized for flood control, it took about six months for rain that fell in the upper basin to slowly flow to Lake O. Now it takes just weeks.

This year, the U.S. Army Corps of Engineers released more water from the lake during the dry season in an effort to get the lake low enough to regrow some of the SAV lost due to Hurricane Irma in 2017. Most of that additional flow went into the Caloosahatchee River, which needs freshwater flow during the dry season to prevent saltwater intrusion.

Some progress has been made in regrowing SAV, but it could be lost if the water rises too quickly.

While the rising water is good news for boaters, “it is a concern for us,” said Ramon Iglesias at Roland Martin Marina in Clewiston. “If the water comes in too quick, the new vegetation will die off.”

“Water coming up as fast as it is, that’s the worst thing that could happen to the lake,” said Mike Krause at Okeechobee Fishing Headquarters in Okeechobee.

Dr. Paul Gray with Audubon Florida said the current water levels are not harmful to the SAV, but “it’s a big concern” if the water rises too quickly because it could prevent sufficient sunlight from reaching the SAV.

Very slowly rising water would be perfect, he explained. The SAV could grow along with the rising water.

“We’re at the mercy of Mother Nature at this point,” said Dr. Gray. He said the current conditions illustrate the need for more storage north of the lake so the flow into the lake could better mimic the natural sheet flow.

In addition to concerns about high water levels drowning out the SAV before it is sufficiently established, Mr. Krause is concerned about chemical herbicides in the water from the Kissimmee Chain of Lakes. Florida Fish and Wildlife Conservation Commission uses chemical herbicides to control non-native invasive aquatic plants. In some Florida lakes, stakeholders are more concerned about boating than they are about fishing, he explained.

“Lake Okeechobee is not a water-skiing lake,” he said. “Lake Okeechobee is a fishing lake.”

He said he is concerned about the residuals in the water that flows from the lakes and waterways in the northern Everglades into the Big O.

Lake rising rapidly
On Aug. 1, Lake Okeechobee was around 11.6 feet above sea level. Just three weeks later, the lake level was up to 13.27 feet. One inch of water on the big lake equals 12 billion gallons of water, which means in just three weeks, 240 billion gallons of water entered the lake, some from direct rainfall, but most from flow from the northern watershed, which spans all the way to Orlando.

In the past week, the lake rose about 7.2 inches or about 86.4 billion gallons of water. Average total structure inflows were 13,328 cubic feet per second. Most of that flow was from the north, but an average of 240 cubic feet per second backflowed into the lake from the St. Lucie Canal (C-44 canal). That’s about 129 million gallons per day of water backflowing into the lake from the St. Lucie canal at Port Mayaca.

No lake water has been released to the St. Lucie canal since March 30. The St. Lucie Canal has a target level of 14 to 14.5 feet above sea level. If the canal level is higher than the lake level, if the Port Mayaca Lock is open, water backflows into the lake. There are no pumps at Port Mayaca; it’s all gravity flow.

With the exception of a few weeks in February and March, the lake flow to the Caloosahatchee at Moore Haven has been in the range beneficial to the estuaries, as requested by Lee County officials. If flow at the Franklin Lock was 1,000 cfs or higher from local basin runoff, no water was released from the lake. For most of the summer, no water has been released to the Caloosahatchee from the lake. Over the past week, no water was released at the lake at Moore Haven. Flow at the Franklin Lock averaged 6,387 cfs, all from local basin runoff. Flows above 2,800 cfs are potentially harmful to the Caloosahatchee estuaries.

Fishing is good
Both Mr. Iglesius and Mr. Krause said the bass fishing has been good this summer.

“The bass fishing has been relatively good,” said Mr. Krause. “They’re striking at whatever you throw at them.” He said anglers are enjoying fishing in the marshes on the north end of the lake.

“Fishing has been great,” said Mr. Iglesius. He said the winning catch at a fishing tournament earlier this month was 26 pounds. “In the heat of the summer, that’s phenomenal,” he said.

As the water level rises, the fish will move around, he added.

Mr. Iglesius said business at the marina has been slow due to the intense August heat. “It’s so hot, people don’t enjoy fishing as much,” he explained.
Test finds no toxins in lake

The National Oceanic and Atmospheric Administration satellite imagery for Lake Okeechobee continues to indicate “medium bloom potential,” according to the Florida Department of Environment Regulation report for the week of Aug. 16-22. The NOAA imagery uses a computer program to predict concentrations on cyanobacteria in the water column. It cannot predict what species of cyanobacteria may be present or whether the cyanobacteria likely present is capable of producing toxins. It cannot predict if there are any toxins in the water.

The South Florida Water Management District collected water samples on Aug. 19 at the Franklin Lock on the Caloosahatchee River, and at four locations on Lake Okeechobee in areas with the highest bloom potential.

Samples were also collected at the Port Mayaca Lock on Aug. 21 and the St. Lucie Lock on Aug. 22.

No algae was visible at the Franklin Lock, the Port Mayaca Lock and the four lake locations at the time of collection.

Water samples from Lake Okeechobee indicated mixed algae present with no dominant species. No toxins were detected in the water samples from Lake Okeechobee.
Streaks of algae on the water’s surface were visible upstream of the St. Lucie Lock structure on the C-44 canal (also called the St. Lucie Canal) on Aug. 22. Test results are pending. (Note: Since the water from the C-44 Canal was backflowing into Lake Okeechobee last week, this means algae from the St. Lucie canal may have been flowing into Lake Okeechobee.)

St. Johns Water Management District staff collected samples at seven locations along the St. Johns River on Aug. 19. Microcystins were not detected in any of the samples. Low levels of saxitoxin (0.14 ppb or less) and cylindrospermopsin (0.08 ppb or less) were detected in five samples, where only low levels of saxitoxin (0.10 ppb) were detected in samples from the Welaka Boat Ramp and near Buffalo Bridge. St. Johns Water Management District staff revisited and collected one sample at the center of Lake Washington in Brevard County on Aug. 19. No toxins were detected.

NOAA satellite imagery of the St. Johns River continues to show no bloom potential.

FDEP collected two samples near Fort Pierce on Aug. 21. These samples were dominated by the Microcystis aeruginosa, which is capable of producing toxins; however, toxins were not detected.

The Park Shore Marina area was revisited by FDEP staff on Aug. 20 and two samples were collected. Toxins were not detected in either of the two samples, although one sample was dominated by Dolichospermum planctonicum.

No toxins were detected in seven other samples collected in locations from Charlotte, Collier, Leon, Martin, Palm Beach and Pinellas counties. DEP staff collected two samples from Mosquito Lagoon area on Aug. 22 (analytical results pending).

Algae continues to be observed in Ft. Lauderdale canals and along the New River. FDEP collected samples collected at the New River Canal Boat Ramp and Canal at 16th Street Bridge on Aug. 12. These samples were dominated by Microcystis aeruginosa and had non-detect and 11.06 parts per billion microcystins, respectively. The 16th Street Bridge location was revisited by FDEP staff on Aug. 15, as well as sites East of Bill Keith Preserve Park and at Hendricks Bridge (analytical results pending).

FDEP report: Lake water samples have no toxins

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