Roberts Bay suffers greatest loss
Sarasota Bay lost about 6% of its seagrass between 2020 and 2022, the Southwest Florida Water Management District (SWFWMD) has reported as part of the results of its latest mapping of bays within the District’s jurisdiction.
In 2020, the report said, Sarasota Bay had 10,540 acres of seagrass. In 2022, that dropped by 577 acres, to 9,962, the report pointed out.
The findings reflected the third straight loss of seagrass in mapping undertaken since 2016, the report noted, adding that the presence of seagrass had reached a 15-year low. In fact, the report pointed out, in “Sarasota Bay Proper” — the segment of the entire Sarasota Bay designated with that name — had lost 486 acres of seagrass, which left Sarasota Bay Proper with the lowest amount of seagrass since 2006.
In contrast, Lemon Bay, to the south, lost only 4% of its seagrass from 2020 to 2022, the report notes.
On the flip side, Tampa Bay’s seagrass loss was at the 12% mark.
The District’s graphics show that Sarasota Bay is divided into the following segments: Palma Sola Bay, Sarasota Bay, Roberts Bay, Little Sarasota Bay and Blackburn Bay. The section that had the biggest decline in seagrass was Roberts Bay, with a drop of 11% from 2020 to 2022. Sarasota Bay Proper was in second place, with a 6% decline, followed by Little Sarasota Bay with 5% and Blackburn Bay with 4%. Palma Sola Bay saw only a 1% decrease, the report said.
SWFWD used codes to describe the conditions that the mapping found: 9116, for continuous seagrass coverage; and 9113, for patchy seagrass.
The report characterized an area as having continuous seagrass coverage if the bottom had a range of more than 25%, up to 100%, “with less than 25% coverage of any area showing up as unvegetated bottom features.” The report added, “The seagrass beds may have variable density.
“Patchy seagrass areas,” it continued, are those that “appear as singular, rounded clumps, or elongated strands of isolated seagrass patches mixed with open bottom or sand.”
The graphic with details about Sarasota Bay showed only a 3% loss of seagrass from 2020 to 2022 in areas that had continuous coverage. Segments of that bay with patchy coverage in 2020 were found to have lost 18% of seagrass acreage over the two-year span.
Yet, between 1988 and 2022, the patchy areas had lost 64% more coverage, while the continuous seagrass sections saw an increase of 175% — from 2,223 acres of continuous coverage in 1988 to 6,106 in 2022.
In regard to Roberts Bay: The patchy areas saw an 18% drop in seagrass, while those segments with continuous seagrass coverage realized a decline of only 1%.
Little Sarasota Bay added 29% more seagrass in its patchy areas, but it lost 20% of its continuous coverage — 85 acres — between 2020 and 2022.
Further, Blackburn Bay gained 48% more seagrass in its patchy areas from 2020 to 2022, while it lost 24% of the seagrass in the areas that had continuous coverage.
District staff presented the report to the Seagrass Working Group on Feb. 13, Susanna Martinez Tarokh, the public information officer for SWFWMD, told The Sarasota News Leader.
The Sarasota Bay Estuary Program response
In a Feb. 17 report, responding to the SWFWMD information, David Tomasko, executive director of the Sarasota Bay Estuary Program (SBEP), acknowledged that the overall decline of seagrass in the entirety of Sarasota Bay was “not great — at all.” However, he added, “[T]he prior two-year period saw a loss of 18%, so at least those losses don’t appear to be accelerating. I do not believe that we will enter into the sort or self-reinforcing ecosystem collapse that appears to be occurring in the Indian River Lagoon – with its 90% loss of seagrass biomass and hundreds of starving manatees,” Tomasko added.
“But the cautionary status of the health of Tampa Bay and Sarasota Bay is starting to get people’s attention,” Tomasko pointed out.
“With this news [from SWFWMD],” he continued, “why am I optimistic that we can turn this around? In part because while much of what happened to our bay is attributable to human activities, our recent actions have reduced many of those impacts.
“For example,” he pointed out, between about 2012 and 2018 or so, there were overflows of treated, but high-nutrient wastewater that totaled over 750 million gallons. Those impacts seemed to have manifested themselves mostly in the lower bay, where we lost 30% of our seagrass between about 2014 and 2018.”
He added that those overflows are not happening — or not happening “much at all” — because the Sarasota County Commission has committed to upgrading its three primary wastewater treatment plants to Advanced Wastewater Treatment status, (AWT,) with no surface discharges in the future.
In January, Mike Mylett, the director of the county’s Public Utilities Department, noted during an update to the commissioners that the first upgrade — involving the largest county operation, the Bee Ridge Water Reclamation Facility, located at 5550 Lorraine Road in Sarasota — is proceeding on the timeline staff had anticipated. That project is expected to be finished before the end of 2025.
In August 2019, the commissioners unanimously agreed to a Consent Order with the Florida Department of Environmental Protection (FDEP) over spills of wastewater from the Bee Ridge plant. FDEP called for the conversion of the facility to AWT status.
“That will put Sarasota County’s wastewater program on par with the City of Sarasota’s,” Tomasko added in his report. The city facility, he noted, “is one of the best in the country, in terms of the quality of [its] produced effluent.”
Moreover, Tomasko wrote, “Regional stormwater retrofit projects have been planned or completed in a number of our priority creeks, and we are working to do even more — and even bigger — projects in places” such as the city’s Bobby Jones Golf Course.
The 18% decrease in seagrass in Sarasota Bay between 2018 and 2022 is largely a result of what Tomasko called “the very strong red tide that we had in 2018.”
He continued, “Keep in mind that 2018 was the worst year for wastewater overflows in our pollutant loading model — likely making the 2018 red tide worse than it would have been without those additional nutrient supplies.”
Researchers have identified nitrogen — a chemical found in wastewater and stormwater — as one of the primary foods for the red tide algae, Karenia brevis. Converting the county’s wastewater treatment plants to AWT status will sharply reduce the amount of nitrogen remaining in the reclaimed water those facilities produce, Mylett of Public Utilities has pointed out.
A May 2019 graphic shown to the county commissioners said that, in 2018, the total nitrogen load from county wastewater facilities that went into Sarasota Bay was 624,000 pounds; of that amount, 238,000 pounds came from the Bee Ridge Water Reclamation Facility (WRF). In comparison, the county’s Central County Water Reclamation Facility — which is located on Palmer Ranch — produced a total nitrogen load of 94,000 pounds in 2018.
The commissioners also have approved converting the Central County WRF and the Venice Gardens WRF to Advanced Wastewater Treatment status.
Tomasko did note in his Feb. 17 article that the discharge in the spring of 2021 of contaminated liquid that had been stored at the Piney Point plant not only went into Tampa Bay but also into Sarasota Bay.
He then explained, “[I]f if you mixed a gallon of what was released from Piney Point into 999 gallons of our ambient water in upper Sarasota Bay, the resulting nitrogen content in the 1,000 gallons would be increased by more than 50%. That’s an illustration of just how bad (high in nutrients) those released volumes were (in excess of 200 million gallons).”
The latter reference was to the April 2021, state-approved release of about 215 million gallons of contaminated water from the former site of a fertilizer plant in Manatee County. A leak was discovered in the plastic liner of one of the stacks holding millions of gallons of wastewater left from the production of the fertilizer, which took place between 1966 and 2001, the Tampa Bay Estuary Program explains.
The leak prompted state leaders’ worry that the collapse of that stack would lead to the destruction of hundreds of nearby homes and businesses. That was why they authorized the discharge into Tampa Bay.
Tomasko added in his Feb. 17 report, “Basically, every part of our coast touched by [the Piney Point] plume had the potential to be adversely impacted by those releases. Tampa Bay is about 350 square miles in size, and so it is easy to see [from a graphic] that the plume affected well more than 200 square miles of coastal waters — from upper Sarasota Bay up to north of Clearwater.
“About 80% of the seagrass loss in Sarasota Bay recorded between 2020 and 2022 occurred in the upper bay,” he noted, “in areas where we know, or at least suspect, that these plumes were transported.”
“Throw in 2022’s Hurricane Ian,” Tomasko continued, “and you can see that there were quite a few impacts we’ve had to endure these past few years. We are also a deeper bay — by about 6 inches — than we were 20 years ago, and our air (and potentially water) is getting warmer. These might make it harder to restore the bay over the next 30 years than it was the past 30 years. So, there are more
challenges ahead of us, but if any part of Florida can pull it off — to effectively respond to the issues we’re now facing — it’s our stretch of Southwest Florida.”