Measurement the largest of all Suncoast estuaries mapped during recent study
Sarasota Bay saw a 19% increase in seagrass beds between 2022 and 2024, as documented by a mapping study that scientists with the Surface Water Improvement and Management (SWIM) program of the Southwest Florida Water Management District (SWFWMD) have released.
That was the largest increase recorded among all of the Suncoast estuaries mapped, the study shows. The other estuaries are Tampa Bay, Lemon Bay and Charlotte Harbor.
The seagrass beds in Sarasota Bay grew by 1,912 acres, the report points out. “All Bay segments (Palma Sola Bay, Sarasota Bay Proper, Roberts Bay, Little Sarasota Bay, and Blackburn Bay) reported positive gains in 2024,” compared with the data produced by the previous mapping cycle, which took place in 2022, a Sarasota Bay Estuary Program fact sheet adds.
SWFWMD’s “seagrass mapping efforts were conducted in the winter of 2024,” a Sarasota Bay Estuary Program news release explains. Since then, the release does note, “Sarasota Bay has endured a myriad of severe weather events, including Hurricanes Helene and Milton.”
Yet, on March 28, the release points out, staff with SWFWMD and the Sarasota Bay Estuary Program (SBEP) “visited Upper Sarasota Bay to view the area’s largest acreage increase. It appears that last year’s severe weather events did not significantly impact the recovered areas. The SBEP plans to further assess the health of the beds through annual site visits and programs like Eyes on Seagrass.”
“There is quite a bit of macroalgae [seaweed] out there, maybe a bit more than we’d like to see, but the seagrass underneath is doing well,” Dr. Chris Anastasiou, chief water quality scientist and seagrass mapping lead for SWFWMD, said in the release. “The gains we saw in Sarasota Bay proper are very encouraging,” Anastasiou added. “We still aren’t back to where we were in 2016, but hopefully, these trends will continue, and we will get there.”
In its news release, SBEP explains, “Seagrasses are a critical indicator of the ecological health of Sarasota Bay, as they require clean water to thrive and are highly sensitive to changes in water clarity and quality. Healthy seagrass beds provide essential habitats that support a diverse range of marine species.”
Then and now
In a March 28 report about the findings, published on the SBEP website, the organization’s executive director, David Tomasko, wrote, “While the majority of the [seagrass] increase occurred in the open waters of upper Sarasota Bay (from the Ringling Causeway up to Manatee Avenue) every part of the bay had increases. Palma Sola Bay added 39 acres, while the lower bay (Roberts, Little Sarasota, and Blackburn Bays) added a total of 40 acres.”
He also explained, “In the Lower Bay, the losses of seagrass started back in 2014, and the results from 2024 are the first evidence of an increase in a decade. The 19% increase across the bay is the second biggest increase seen in over 30 years, and while we are still 12% below the peak coverage we had in 2016, we now have 36% more seagrass than we had 36 years ago, in 1988.”
Tomasko then wrote, “So, what’s the benefit of having such an increase in seagrass coverage? Well, the Smithsonian [Institution], which has had a research lab along Florida’s Indian River Lagoon for at least 40 years, concluded that the average acre of seagrass can support approximately 40,000 fish — Seagrass and Seagrass Beds | Smithsonian Ocean. Multiply 1,912 acres of NEW seagrass by 40,000 fish per acre, and you can come up with a defensible conclusion that we’ve added enough seagrass habitat to support more than 75 million fish.”
Tomasko pointed to two figures that he said provide the best display of the “turnaround we’ve been able to bring about here in Sarasota Bay.
“The photo on the left shows (in red) the 22% decrease [his emphasis] in seagrass coverage that was documented between 2018 and 2020 in the Upper Bay. The areas of seagrass loss in the Upper Bay were widespread — mostly north and south of Longbar Point, but also in the area east of southern Longboat Key and offshore of the mainland shoreline between Bowlees Creek and Whitaker Bayou. The years of 2018 to 2019 had some of our worst water quality in the bay, including the impacts of a red tide event that exceeded a year in our region. Was this by chance alone — some event not connected to human activity? Hardly, 2018 was the worst year on record for wastewater overflows in our region, and before those overflow events occurred, we likely overloaded our reclaimed water systems with high-nutrient treated effluent, in an attempt to prevent those overflows from occurring.”
Tomasko next explained, “Now, compare that map to the one on the right, which shows (in green) the amount of new seagrass meadows that have been added in the last two years. In the same areas where much of the losses occurred between 2018 and 2020, we’ve seen big increases between 2022 and 2024. This wasn’t really a surprise to us, as we have been anticipating a substantial increase since last spring — Director’s Note: Reasons for optimism — with a few caveats.”
He further noted that the increase in the seagrass beds follows “multiple years of improving water quality, as we highlighted nearly two years ago — Director’s Note: FDEP determinations of water quality trends. But why did our water quality get better? Because, we believe our local government partners have invested about $300 million in projects that have upgraded our wastewater infrastructure, retrofitted over 6,000 acres of our watershed with regional stormwater treatment systems, and — importantly — we have spent considerable efforts to inform our public about the role that they can play in helping to reduce their own contributions to bay-wide pollution …”
Tomasko did acknowledge, “There might be some skepticism about the good news that we often bring to the public, which is understandable. However, the determination that our water quality had improved sufficiently to remove us from [the] Impaired Waters List for nutrients” — which the Florida Department of Environmental Protection (FDEP) releases — “was made independently by FDEP staff. And the seagrass maps were independently developed by the staff of the SWFWMD.”
He added, “And while our efforts have been good for Sarasota Bay, they can also help, perhaps, to serve as an example for other coastal communities in Florida and elsewhere. And to perhaps help that along, we have produced a webpage that summarizes what we’ve seen in Sarasota Bay, what happened, how it happened, and why it matters — Seagrass & Algae | Sarasota Bay Estuary Program.”
SWFWMD explains that the Sarasota Bay Estuary Program “works with local governments and researchers to assess and respond to the needs of Sarasota Bay.”