Sarasota Bay’s water quality continuing to improve, latest ‘report card’ shows

County commissioner describes situation as best in 15 years

The latest Sarasota Bay Estuary Program (SBEP) Report Card on the state of Sarasota Bay, released on Sept. 16, shows that the water quality has been improving since 2018.

Sarasota County Commissioner Michael Moran, who represents the county on the SBEP board, handed out copies of the nonprofit’s 2022 Report Card to his fellow commissioners during their regular meeting on Sept. 13. In some cases, he noted, “Our water quality is the best it’s been in 15 years.”

In 2021, the Report Card says, data collected from three of the five bays that the SBEP tracks indicated each of them scored an A. That meant that all signs indicated that they had healthy water. Those were Big Sarasota Bay, Roberts Bay and Palma Sola Bay.

The other two bays— Little Sarasota Bay and Blackburn Bay — received B scores, meaning that most signs indicated healthy water quality, but careful monitoring would be required.

In 2019 and 2020, the SBEP Report Card showed, both Little Sarasota Bay and Blackburn Bay received a score of C, meaning one or more signs indicated concern; therefore, stressors needed to be investigated, as well as compliance with wastewater and stormwater permits.

In 2018, Little Sarasota Bay earned a D, with all signs indicating water quality degradation.

In its updated, 2022 Comprehensive Conservation Management Plan for Sarasota Bay, the SBEP explains, “Little Sarasota Bay receives freshwater from five tidal tributaries” — Elligraw Bayou, Holiday Bayou, Clower Creek, Catfish Creek, and North Creek, as well as direct runoff from coastal areas. Midnight Pass, which once separated Siesta Key and Casey Key, historically connected Little Sarasota Bay to Gulf waters, but it closed in 1983.”

In spite of the good marks for Big Sarasota, Roberts and Palma Sola bays, the latest Report Card continued, “lingering impacts from severe red tides in 2016 and 2018 and Hurricane Irma in 2017” were found.

Further, it said, “Big Sarasota Bay lost a significant amount of seagrass acreage between 2018-2020, likely as an indirect result of the 2017 and 2018 red tides. However, other ecosystem health indicators suggest that conditions are improving. SBEP staff and partners will continue to monitor seagrass recovery in affected areas.”

Further, the Report Card noted that seagrass coverage bay-wide in 2020 “was at its lowest in over a decade.”

In explaining “the relatively good ecosystem health scores” shown for 2021, the Report Card said, “There is a delay between water quality improvement and seagrass recovery. If water quality continues to improve in coming years, we hope to see seagrass meadows recover.”

The Report Card pointed out that the improving health of Little Sarasota and Blackburn bays is likely a result of “management actions that have been taken to reduce wastewater discharges to these bays.” It noted the Sarasota County Commission’s commitment to upgrading its largest sewage treatment plant — the Bee Ridge Water Reclamation Facility on Lorraine Road in Sarasota — to Advanced Wastewater Treatment status. That project, which is underway, will lead to a dramatic reduction in the amount of nitrogen in the reclaimed water, as Public Utilities Department Director Mike Mylett has explained to the commissioners.

Nitrogen has been identified as the primary food for the red tide algae, Karenia brevis.

SBEP explains that its Report Card tracks the following measurements:

  • “Total Nitrogen or TN — Nitrogen is an essential nutrient for life, but when nitrogen concentrations in estuaries are too high, algae blooms can result.
  1. “Chlorophyll-a — Scientists measure chlorophyll-a to determine the amount of phytoplankton, or microscopic algae, in the water. Like nitrogen, some amount of phytoplankton is a good thing. Phytoplankton produce oxygen and provide food for filter-feeders like shellfish. However, too much phytoplankton can reduce the amount of light that reaches seagrass beds, thereby restricting their growth.
  2. “Seagrass — The extent of seagrass meadows in Sarasota Bay is a good biological indicator of water quality. How clear or cloudy the water determines how deep seagrass meadows can grow. As water becomes clearer, in other words as transparency increases, seagrass meadows can expand into deeper water.
  3. “Macroalgae — Also called seaweeds, macroalgae are important food and habitat for estuarine creatures. However, they can respond quickly to nutrient pollution by growing and shading out seagrass meadows. The bacteria that break down macroalgae blooms can also reduce oxygen levels in the water, which is dangerous for fish and other wildlife. Therefore, macroalgae blooms can be an indicator of poor water quality.”

Further, in its 2022 Comprehensive Plan for Sarasota Bay Update, the SBEP pointed out that, in 2021, it completed a peer review process “for a comprehensive pollutant loading model for Sarasota Bay.” That includes load estimates for dissolved inorganic nitrogen (DIN), which “represents nutrient forms that are immediately available for algal uptake, and thus the most problematic.”

Based on its pollutant loading model, that update says, the DIN loads appeared to be about 12 tons higher on an annual average basis from 2013 through 2019, compared to the period from 2006 to 2012. Therefore, that document continues, a reduction of 12 tons per year would be a logical but preliminary target that would be refined starting this year, during the development of the SBEP’s Reasonable Assurance Plan for Sarasota Bay

The SBEP explains that the Sarasota Bay Estuarine Nutrient Region “extends from the Manatee Avenue Bridge in Manatee County to the Siesta Key Bridge in Sarasota County.”

SBEP adds that it “relies on partners at Manatee County, Sarasota County, the Southwest Florida Water Management District and the Florida Department of Environmental Protection (FDEP) to collect data.”

Sarasota County’s Public Works Department monitors 30 sampling areas across six bay segments from Big Sarasota Bay to Blackburn Bay, the SBEP’s complete 2022 water quality report notes. “Each area has 12 sampling stations. One station is sampled in each area each month so that all 12 stations are sampled each year.”

Further, it points out, the Florida Department of Health in Sarasota County samples biweekly for bacteria and red tide at 12 beach locations on the Gulf of Mexico, plus the Palma Sola Bay Causeway and Bird Key Park.

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