The following is a report on the state of Sarasota Seagrass from outgoing Executive Director of Sarasota Bay Estuary Program David Tomasko.
Hopefully, you’re aware of our recent good news on the health of the bay. If not, it’s pretty basic, and it involved a couple of steps:
Concerns over the obvious deterioration in the health of the bay manifested themselves in a series of public meetings, culminating in a packed auditorium at Riverview High School in 2019.
Building off that energy, the SBEP worked with our partners to develop a Pollutant Load Reduction Goal (PLRG) back in 2021
A Water Quality Restoration Workshop, also held in 2021, determined that wastewater upgrades and stormwater retrofit projects that were mostly underway at the time were expected to be of sufficient magnitude that they would meet the bay’s PLRG
By 2023, our water quality had improved enough that FDEP determined that none of the open waters of Sarasota Bay were out of compliance with their established numeric nutrient criteria
By 2025, SWFWMD informed us that seagrass coverage had increased by nearly 2,000 acres, a 19% increase.
This is all good news – and it is due to the focused work that local governments have undertaken to reduce wastewater overflows, decrease the nutrient content of treated effluent from wastewater treatment plants, and the completion of two large regional stormwater treatment projects that were constructed in areas that had developed without stormwater rules in place.
The seagrass gains we’ve seen across the bay do not represent a pristine system. Not at all. And concerns about the bay’s health continue. But…the bay did not tip over into the problems that were seen in the Indian River Lagoon over the past decade. That said, while the pattern of seagrass increase across the bay is positive, different parts of the bay are displaying different patterns.
For example, Upper Sarasota Bay (the area between Ringling and Manatee Avenue Causeways) has seen the greatest seagrass increase. But most of that increase is in areas that had previously lost coverage, and so we’ve really just re-gained what we had previously lost.
We’ve gained a lot there over the last two years, but we’re still lower than what we had between 2008 and 2018. However, those losses between 2016 and 2022 did not continue, but instead reversed.
In the rest of the bay, the pattern of change varies spatially. Palma Sola Bay continues to show signs of being a healthy bay – in terms of nutrients – as the amount of seagrass is higher than it was two decades ago. Over the past two years, we’ve added 40 acres of seagrass in Palma Sola Bay. We’ve also added 40 acres in the lower bay segments of Roberts, Little Sarasota and Blackburn Bays, but we are not back to where we want to be, especially in Little Sarasota Bay.
The losses of seagrass in the lower bay started earlier, in about 2014, likely reflecting increased wastewater overflows from the Bee Ridge WWTP, and the macroalgae blooms that started in the lower bay around 2013. But those losses leveled out by 2020, concurrent with gaining better control over the wastewater overflows. And we’ve even seen slight gains in coverage (40 acres) between 2022 and 2024. However, we are still down by about 200 acres in the lower bay, compared to where we were in 2014. There’s more still to do down there, but we’re moving in the right direction.
That is a challenge, going forward, but the changes in circulation that occurred in Little Sarasota Bay after Milton opened up Midnight Pass might make increased coverage more likely in that system over the next few years. The overall water quality in Little Sarasota Bay has improved, and that should allow, over time, a nice increase in coverage in that system.
Keep in mind, every part of Sarasota Bay showed increased coverage the past two years, even though the increases were more modest in the lower bay. In contrast, the trends in the Indian River Lagoon are not nearly as positive. Yes, there has been a recovery of sorts in seagrass coverage there, which is good news.
But if you dive into the details, almost all of that recent increase is in the Mosquito Lagoon, which is the least urbanized portion of the IRL, as indicated below.
Outside of Mosquito Lagoon, there’s not much good news in that system, and seagrass coverage has almost collapsed in the Northern and Central sections of the IRL, and in the Banana River.
So why should we care about this? Well, the State of Florida has concluded that the typical acre of seagrass contains about 40,000 fish. Gaining nearly 2,000 acres of seagrass in Sarasota Bay means gaining habitat capable of supporting more than 70 million fish.
Also, think about the namesake for our northern county – the Florida manatee. Over the past few years, we’ve lost over 3,000 manatees in our state. Out of how many, you ask? Well, our latest estimates are that the statewide population is likely less than 10,000. If you think that sounds like our recent losses are a big number, and a not insignificant percentage of the total population, you’re right. The basis for the big uptick in manatee deaths the past five or so years is from starvation, as manatees find it harder to find their preferred food source, seagrass meadows, particularly in the IRL.
Those impacts to manatees in the IRL are worse than just the number that have died over the past few years; it’s also the hit to our future populations. For example, Brevard County alone averaged about 20% of statewide manatee deaths between 2000 and 2021. But that single county (which straddles the areas with the largest seagrass losses in the IRL) also averaged 30% of the “perinatal” manatee deaths recorded across the state during those same years. The term perinatal refers to deaths of newborn calves and or stillbirths and is thought to be related to some degree to stresses to mother manatees, like not being healthy enough to feed their young, or to carry baby manatees to term.
In Sarasota Bay, we have a much better trajectory for manatee deaths recently. In our two counties, we’ve averaged fewer than 6 perinatal deaths per year, during the years 2010 to 2021, while Brevard County alone averaged over 30 perinatal deaths over the same period, according to FFWCC.
So, where would you rather be a manatee? Where would you rather be a manatee mom trying to nurse your offspring? I’m thinking it’s our system. But if we don’t keep our eye on the ball, if we backslide again – like we did about ten years ago, the possibility exists that we follow the trajectory that the folks in the IRL are trying to pull out of.
Seagrass nurseries and seagrass transplanting efforts, and increased funding for seagrass science, have their place. But if you want to restore manatee habitat on a truly ecosystem scale, you’ve got to get your pollutant loads under control. Thankfully, and although we have more to do, at least we’ve started down the pathway to a healthier and more resilient Sarasota Bay.
We will continue to have dead manatees in our local waters. They will die from natural causes, and they will be hit by boats, and they will continue to die after being tangled in fishing line. But hopefully, we won’t be seeing starving ones in our bay anytime soon.
David Tomasko
Executive Director
Sarasota Bay Estuary Program
