Nutrients in runoff feeding algal blooms on lake

OKEECHOBEE — South Florida Water Management District officials, as well as the Department of Environmental Protection, continue to track algal blooms on Lake Okeechobee, according to the ecological conditions report given by Terrie Bates at the Aug 3, meeting of the SFWMD Governing Board in West Palm Beach.

She said the combination of a very dry “dry season” followed by heavy rains in June created a heavy nutrient flow into the lake. Phosphorus level spiked in June with flush of nutrients coming into the lake, she said.

“We are starting to get water in the restored portion of the Kissimmee River,” said Ms. Bates.

“We are starting to see water back in the floodplain.”

She added that they are controlling the flow into those areas to prevent damage to the construction work still underway on the Kissimmee River Restoration project, and to make sure they maintain sufficient oxygen levels in the water.

“Operations has tried to slowly ramp up the flows,” she said.

Heavy rainfall north of Lake Okeechobee caused the Big O to rise about a quarter of a foot the first week in August, she said.

She said the SFWMD regularly tests the phosphorus levels in the lake water.

“Because it had been dry for so long with that first rainfall you get a heavy flush of nutrients coming in,” she said.

The average phosphorus levels in the lake in July was 123 ppb.

FDEP has set the phosphorus target for the lake at 40 ppb.

Water backpumped from the Flow Equalization Basin (FEB) south of the Everglades Agricultural Area in late June and early July to reduce flooding in the wildlife areas was about 60 ppb, according to SFWMD data.

According to SFWMD data, all of the water flowing into the lake is significantly above the 40 ppb level set for the Big O.

From 2013-2016, water from the lower Kissimmee basins averaged 157 ppb phosphorus; Taylor Creek/Nubbin Slough averaged 446 pbb; Indian Prairie averaged 231 ppb; Fisheating Creek averaged 164 pbb. The 5-year average for the phosphorus load from the area east of the lake was 155 ppb, but testing done in July on the water backflowing into the lake at Port Mayaca showed levels around 300 pbb.

According to SFWMD, on average, the northern watershed contributes 92 percent of the water entering the lake and 90 percent of the total phosphorus load.

In addition to monitoring nutrient loading, SFWMD measures chlorophyll A levels at various stations around the lake as chlorophyll is an indicator for algal bloom conditions, she explained. They also do a standard microcystin level check each month. Microcystin is a toxin that can be released by some types of algae.

She said in July they had just one test that was above 0.2 in the lake.

Anything below 0.2 does not show up on the monitor, she said.

The areas with higher chlorophyll levels match up with the satellite images that indicate algal blooms, she said.

The blooms have been seen along the northern shores of the lake, where the water highest in nutrient levels enters the lake.

“This is not the type of algae bloom you might be thinking of from the pictures from last summer,” Ms. Bates said. It’s not the thick mats seen on the Treasure Coast, referred to as looking like “guacamole” on the surface of the water.

The algae in the lake is small particles suspended in the water.

“It’s challenging to monitor. It’s very hard to chase the bloom,” she explained. When an algae bloom is reported, FDEP responds to take water samples.

Researchers might have a report one day, and the next day go out to that area and not find any algae.

She said weekly samples are collected by SFWMD at designated points across the lake.

The St. Lucie and Caloosahatchee rivers have not received any lake water during the rainy season.

No lake water has flowed into the St. Lucie from the lake this year. The water from the C-44 basin is not even flowing into the estuaries.

“All the water from C-44 basin is instead backflowing by gravity into Lake Okeechobee,” said Ms. Bates.

That water normally goes into the estuaries, she said.

Allowing that water (which tested around 300 ppb phosphorus in July) into the lake instead of into the estuaries has reduced both the freshwater flow and the nutrient load going into the St. Lucie estuary.

Since the start of the rainy season, there have been no discharges going into the Caloosahatchee from Lake Okeechobee, Ms. Bates continued. (Before the rainy season started, lake water was sent to the Calooshatchee River to prevent salt water intrusion in that waterway.)

The Caloosahatchee River has received substantial flows from that watershed since the rainy season started, she explained.

“There are significant flows coming into river just downstream of the Franklin structure,” she added.

In the Everglades, direct rainfall has caused high water levels north of the Tamiami Trail, despite efforts to send more water to Florida Bay.

“We are trying to manage water any way we can to get the water levels down in the Everglades,” Ms. Bates said.

While north of Tamiami Trail the tree islands are under water, south of the trail Florida Bay is not getting enough freshwater.

Salinity levels are still high in Florida Bay, she said. “We are not meeting the target we would expect to see this time of year in the rainy season.”

SFWMD executive director Ernie Marks said projects are under construction which will allow SFWMD to increase the flow of freshwater to Florida Bay.

Avoid swimming when visible algal bloom is present

PAHOKEE — The Florida Department of Environmental Protection and the Florida Department of Health are reminding residents and visitors to be mindful during summertime recreational activities as the season’s high temperatures, abundant sunlight and frequent rainstorms annually increase the presence of algal blooms in certain Florida waterbodies.

Since a bloom was first identified on Lake Okeechobee, FDEP has coordinated with the South Florida Water Management District to perform frequent surveillance and sampling. While most of these results have been non-detect or very low levels of toxins, DEP received results of one sample with elevated levels of toxins (microcystin) near Canal Point Park in northwest Palm Beach County on the eastern shore of Lake Okeechobee. That sample was taken Aug. 1. It is recommended that the public avoid swimming and fishing in this area if algae is visible. FDEP will retest the water in that area this week.

On Aug. 7, researchers visited the Pahokee marina and no algae was found.

On that same day, researchers also checked for algae at two locations south of the Pahokee marina near Belle Glade and found no algae.

FDEP and Florida’s water management districts frequently monitor Florida’s water quality and routinely collect algal bloom samples as soon as they are observed to identify algal type and test toxin levels. In addition, staff are deployed to take additional samples in response to reported blooms – whether from a citizen, other response team agencies or other sources. To keep residents and visitors informed of the latest algal bloom monitoring results and activities, FDEP has a website where it posts the dates and locations of samples collected. Test results are added as they become available. Persistent blooms are routinely monitored and retested.

Individuals should avoid contact with algae and can report algal blooms using DEP’s toll-free hotline at 855-305-3903 and online at

You are encouraged to leave relevant comments but engaging in personal attacks, threats, online bullying or commercial spam will not be allowed. All comments should remain within the bounds of fair play and civility. (You can disagree with others courteously, without being disagreeable.) Feel free to express yourself but keep an open mind toward finding value in what others say. To report abuse or spam, click the X in the upper right corner of the comment box.

Facebook Comment