17-02-2025
Lake Tarpon's water quality was a mess. A new report says it has gotten better.
Lake Tarpon, the largest freshwater lake in the Tampa Bay area and home to some of the best bass fishing in the state, has long been plagued by outbreaks of invasive species and poor water quality.
For decades, water managers have treated the lake with expensive herbicides and mechanical harvesting of hydrilla, an invasive aquatic plant that crowds out native species and clogs boat propellers. It was often a losing battle.
The aquatic weed even contributed to a fatal personal watercraft accident in 2000 when a man on a WaveRunner swerved to avoid a patch of hydrilla, throwing his passenger into the water where he drowned.
One year later, the district published an update to its surface water plan, citing an alarming decline in water quality.
When Southwest Florida Water Management District staff on Thursday unveiled the first surface water plan in more than two decades, water managers appeared much more optimistic.
About half a dozen residents joined project managers at the Brooker Creek Preserve Center in Tarpon Springs, where Lake Tarpon water managers announced a 'hold the line' strategy — a turning point in the lake's health.
Chris Anastasiou, the water management district's chief water quality scientist for the surface water program, said about 90% of the lake's submerged plants are healthy, which has created a thriving ecosystem and bass fishery.
It took years of hard work to get here, and water managers can't drop their guard now, he added.
'Holding the line does not mean do nothing. It actually takes a lot of work to hold the line,' Anastasiou said.
A draft lake management plan, published in August, credits Lake Tarpon's revival to the Florida Fish and Wildlife Conservation Commission's recent efforts to treat hydrilla outbreaks early.
Water managers keep invasive species at bay by spraying herbicide and collecting the aquatic weed with a marine tractor that scoops it from the surface. But in the 1990s, hydrilla growth had become out of control.
A low point occurred in 1992, when lake managers treated 500 acres of hydrilla. In 1993, one resident told the then-St. Petersburg Times she had never seen an outbreak as bad in her 20 years working at a marina on the lake.
Since 2010, fewer than 100 acres have been treated each year, according to the water management district.
Lake Tarpon managers track the presence of hydrilla by measuring chlorophyll-a, a pigment used in photosynthesis.
In 2001, they set a goal of 14 micrograms per liter, which managers based on data collected in Lake Tarpon between 1990 and 1992 — a very healthy period just before the lake's water quality nosedived.
Water managers acknowledged in the plan that chlorophyll-a levels have remained 'well above' that goal over the last 25 years, though the report states Lake Tarpon is 'a very healthy system.'
Anastasiou said he doesn't know why chlorophyll levels have remained so high despite the absence of hydrilla for many years. It's something that future research will need to address.
Residents in attendance Thursday evening asked scientists about the effects of native species, drawdowns and hurricanes on the lake. Human impact was a main concern.
Liz Lindsay, who has lived in Pinellas County for more than 30 years, said she was concerned with development encroaching on Lake Tarpon. She recently moved to north county after St. Petersburg became too crowded, she said.
'How are you able to keep up with the amount of development?' she asked. 'It seems like just everybody wants to move to Florida now. Are they really paying attention to the negative impacts of all this development?'
In 1999, developed areas made up 38% of the lake's watershed. By 2020, urban land had grown to about 45%, according to the draft plan.
Urban lakes often struggle with high nutrient loads that can feed algae blooms, but managers said that doesn't appear to be an issue for Lake Tarpon.
Since 2003, levels of nitrogen and phosphorus, which are common in lawn fertilizer, have remained within managers' goals.
Still, water managers asked homeowners to avoid excessive fertilizer use, especially in neighborhoods in the southwest and northeast portions of the lake where drastic elevation slopes quickly channel runoff into the lake.
Anastasiou said development doesn't always spell doom for Florida's water bodies. He pointed to Sarasota Bay, which the state removed from the impaired water bodies list last year after county officials prioritized stormwater improvements and habitat restoration.
'You can have both. It's hard. It takes a lot of money,' he said.
While celebratory in tone, the new lake plan echoed managers' caution.
'Careful attention is needed to ensure that the progress made over the past two decades is not lost due to land use change, sea level rise, climate change and other impacts,' the plan states.
The draft plan will presented to the water management district's governing board in March before being sent for final review.
