As scientists keep trying to figure out why last red tide bloom was so severe, Sarasota County staff is at work on proposals for reducing nutrient loads, Water Quality Summit attendees learn

Panelists at county event discuss range of options — from those homeowners can take to expensive infrastructure fixes

Audience members in the Riverview High School Auditorium listen as panelists discuss measures being taken to improve water quality in Sarasota County. Rachel Hackney photo

Scientists still are working to determine why the red tide bloom that began in 2017 and lingered into 2019 was so bad, Cynthia Heil, director of the Red Tide Institute at Mote Marine Laboratory in Sarasota, told about 650 participants at the Sarasota County Water Quality Summit on June 5.

“We suspect climate change,” Heil added, but that theory “is open for investigation at this point.”

Scientists do know what feeds red tide, as Heil and a number of the other participants pointed out during the five-and-a-half-hour program conducted in the Riverview High School Auditorium.

Chief among red tide’s food is nitrogen, panelists said.

Over the past 10 years, two studies suggest that the red tide algae, Karenia brevis, prefers nitrogen in the form of ammonia when it is in full bloom mode, Heil added.

A graphic shows details about the Loop Current and the continental shelf off the west coast of Florida, both factors in red tide blooms. Image courtesy Sarasota County

And while some measures the public can take to reduce the amount of nitrogen that goes into waterways are relatively easy — cleaning up pet waste, for example — others are much more costly, as Sarasota County staff members pointed out.

Altogether, Chuck Walter, the county’s Stormwater Division manager, told the audience, staff estimates measures it has proposed to the County Commission would carry a price tag of about $310 million.

Even with staff planning to spread out the projects over 20 to 25 years, Walter continued, that would mean $30 million to $35 million would have to be budgeted on an annual basis to those initiatives.

Along with the potential shift to advanced wastewater treatment systems, he said, staff is evaluating more conversions of septic systems to sewer and measures to ensure cleaner stormwater enters county waterways.

Mike Mylett, interim director of the county’s Public Utilities Department, pointed out that the county already is spending “upwards of $15 million a year in fixing and tightening up our aging infrastructure.”

As part of the ongoing discussion, Walter explained, staff members are weighing the best ways to achieve the greatest reductions in nitrogen loads “for the lowest investment. … It is really a balancing act, going forward.”

Just upgrading the county’s largest wastewater treatment plant, the Bee Ridge facility, to an advanced wastewater system, could cost from $50 million to $100 million, Mylett told the audience.

This graphic, presented to the County Commission on May 8, shows details about the nitrogen loads from wastewater treatment plants in the county. Image courtesy Sarasota County

Yet, instead of the double-digit nitrogen levels in the reclaimed water that the Bee Ridge facility produces, the advanced treatment methods would result in a level of about 3 milligrams per liter, Mark Alderson, executive director of the Sarasota Bay Estuary Program, pointed out. “You’re reducing your nitrogen load by fivefold, tenfold. … You’re getting quite a reduction in your concentration” across the region, Alderson added.

By the time the reclaimed water from the Bee Ridge plant ends up irrigating a lawn, Mylett emphasized, the nitrogen load has been reduced “to the lower double digits.”

The Bee Ridge facility is permitted to handle 12 million gallons of wastewater a day, Mylett noted. Staff anticipates that as the county’s population continues to grow, the county will need to seek a permit allowing for an increase to 18 million gallons a day.

Further, he explained, the Bee ridge facility “has adequate space” to be converted to an advanced wastewater treatment plant. The two other county facilities that produce reclaimed water, he said, do not. The Central County and Venice Gardens plants, Mylett continued, “sit on much smaller parcels, and it’s a much larger challenge to convert those processes to advanced [wastewater] treatment.”

Still, he pointed out, “Nothing is off the table.”

County staff is preparing to appear before the County Commission again in September, Walter said, with proposals about the total costs of specific upgrades and sources of potential funding for them.

Walter told the audience that some assistance could come from the Southwest Florida Water Management District (SWFWMD). “The EPA is also a great source of funding.”

The County Commission could pursue grants from the Florida Legislature, too, and other federal funding avenues, Walter said. The best way to obtain outside financial assistance, he noted, is to make it clear that the county would be putting up money, too.

Yet another means of paying the improvements could be utility fees, Walter pointed out.

During a May 8 presentation to the County Commission, he suggested the potential implementation of a new utility assessment on county property owners, to help cover the cost of the improvements the board chooses to pursue.

To craft the best possible recommendation to the board late this summer, he pointed out, staff also plans to talk with members of county advisory boards focused on utilities and stormwater, as well as those on the Environmentally Sensitive Lands Oversight Committee and even the Library Advisory Board, who could offer a different perspective.

Delving into the science

A graphic shows nutrient sources for red tide blooms. Image courtesy Sarasota County

As the first among about two-dozen speakers on the program, Heil of Mote presented a number of slides to explain what researchers have learned about red tide and what they do not know.

Having documented 62 years of red tide occurrences, she said, scientists can show that “Southwest Florida is ‘Red Tide Central.’”

Karenia brevis, the red tide algae, “hangs out” on the edge of the continental shelf that extends west off Florida’s coast; that shelf is very wide and very shallow, she pointed out.

The Loop Current in the Gulf of Mexico occasionally adjusts its circulation, she continued, which “moves the slow-growing bloom” to shore. People are not aware of the process as it is taking place, she added, because “it’s happening at depth.”

Altogether, Heil said, 13 nutrient sources have been identified for red tide blooms in Southwest Florida. Scientists have quantified them, as well, she noted. The nutrients range from sediments to atmospheric particles to dead fish.

One oft-asked question in connection with the last bloom, Heil continued, was whether it was exacerbated by the freshwater blue-green algae — cyanobacteria — linked to the discharges from Lake Okeechobee that flowed into the Caloosahatchee River. Southwest Florida has seen periods when no red tide in spite of high-volume Lake Okeechobee releases, Heil explained. “So it’s very difficult for scientists to point a finger at [the Caloosahatchee].”

However, she said, about 30% of a small red tide bloom last summer appeared to have been supported by the cyanobacteria from Lake Okeechobee and the Caloosahatchee.

A graphic shows details about research into potential connections between the Lake Okeechobee discharges and red tide in Southwest Florida. Image courtesy Sarasota County

Mote has been putting its focus on controlling red tide blooms, Heil told the audience. For example, it has been working with “living docks,” which contain organisms that filter out nutrients in the water.

Mote researchers, she added, also have been experimenting with clay and ozone, testing about 50 different compounds.

The problem, she pointed out, is that, so far, Mote has had limited success killing the toxins released by Karenia breviswhen it dies. Only about 10% of the initiatives Mote has tried have proven effective in that respect, Heil noted.

Tackling the nutrient loads

Another panelist, Steve Suau, the principal of Progressive Water Resources. told the audience that, as development has increased in Florida, the number of nutrient-impaired waterways also has risen, especially over the past decade. “Now we expect all [Sarasota] Bay segments will be designated impaired in 2020.”

“Stormwater is the conduit that transports these nutrients to our bays,” he emphasized. “Maintaining the natural biology is the real matrix for success.”

A graphic explains natural processes involving nitrogen in the environment. Image courtesy Sarasota County

Suau talked of research involving the use of wood chips, biochar and other sources of carbon to prevent nitrogen loading in the waterways. Biochar, he explained, is organic matter produced by a burn without oxygen. Palms and palmettos will have patches of charred areas, he noted, after a controlled burn. “That’s nature’s way of putting carbon back in the soil.”

He cited one example of a nursery in Florida that was producing high levels of nitrate, which was flowing into a waterway. The owners constructed a trench that was 5 feet wide and 7 feet deep and then mixed sandy soil with sawdust in the trench. It has been proving very effective in dealing with the nitrate, Suau added. Studies he had seen, he pointed out, showed that the process could work from 15 years up to perhaps 50 years.

A graphic explains the use of biochar to reduce nutrients in waterways. Image courtesy Sarasota County

Several speakers referenced the local government ordinances that ban the use of fertilizers with nitrogen and phosphorous during the rainy season — from June 1 through Sept. 30, including the Sarasota County regulations enacted in 2007.

In response to a question about the potential implementation of stricter measures, Alderson of the Sarasota Bay Estuary Program said the Florida Legislature “is not in favor of moving forward with additional regulation of fertilizer at this point.”

Kathleen Weeden, engineer for the City of Venice, pointed out that Venice also adopted such an ordinance before the state pre-empted such local government efforts, noting how fortunate residents are as a result.

Nonetheless, she pointed to the fact that the local government restrictions on fertilizer use are voluntary. “But we do a lot of outreach,” she added, trying to educate the public about the problems related to fertilizer use.

This graphic provides information about some of Sarasota County’s water quality policies. Image courtesy Sarasota County

Another panelist, Mary Lusk, an assistant professor at the University of Florida, talked about steps homeowners and other members of the public can take to reduce the nutrient load in stormwater.

For example, she said, leaf litter — especially from the oaks abundant in Florida — and grass clippings often pile up on storm drains. Then, when the rainy season begins, she continued, what is referred to as the “first flush” sends all that nutrient-laden matter into the stormwater system. “Clean those basins out.”

A graphic shows details about a study involving nutrient loading produced by a ‘first flush’ of seasonal rainfall. Image courtesy Sarasota County

Lusk further emphasized the need for more pervious surfaces, which naturally filter out nutrients, and she encouraged audience members to use rain barrels to recycle water.

She also offered an anecdote about another significant factor in nutrient loading.

She and her graduate students were working on a study in the area of the Indian River Lagoon last summer, Lusk said, looking for sources of nutrients in stormwater.

One couple with whom they spoke were so proud of the fact that they use no fertilizer on their lawn, Lusk said. “But they have a beautiful black [Labrador retriever] in the back yard that they don’t clean up after.”

“So clean up after your pets.”

Leave a Comment