Open waters of Sarasota Bay from Siesta Drive to Venice Inlet unsafe for water recreation, based on latest samples for fecal bacteria, executive director of Sarasota Bay Estuary Program warns

Mote Marine Lab reports ‘significant spike in Sarasota Bay concentrations of nitrate and ammonia’

On Sept. 3, writing about the latest results of water sampling that a team has been conducting in the aftermath of Tropical Storm Debby’s passage along the Gulf Coast of Florida, David Tomasko, executive director of the Sarasota Bay Estuary Program, wrote, “As of now, the open waters of Sarasota Bay from Siesta Drive down to Venice Inlet are out of compliance for fecal indicator bacteria, and should not be considered to be safe for recreational activities such as swimming, jet skiing, wakeboarding, or any activity that could involve the participant accidentally ingesting water through their mouth or nose or entry of water via a cut or scrape. These aren’t samples taken by stormwater pipes or in quiescent dead-end canals — these are out in the open waters of the bay.”

In related news, on Sept. 5, Mote Marine Laboratory scientists reported in a news release that they had recorded “a significant spike in Sarasota Bay concentrations of nitrate and ammonia, which may serve as an increased source of nutrients for aquatic bacteria and algae,” the nonprofit announced in a report it released on Sept. 5.

The most recent red tide update for the state — issued by the Florida Fish and Wildlife Conservation Commission (FWC) on Aug. 30 — reported that the red tide algae, Karenia brevis, “was not observed in samples collected statewide over the past week.” The next red tide update is due Sept. 6.

“Tropical Storm Debby’s recent passage through the Gulf of Mexico had a significant ecological impact on Sarasota Bay and the associated coastal environment,” Mote noted in its Sept. 5 report. “However, the question remains as to whether the immediate impacts over days to weeks will have longer-term ramifications for these ecosystems over months to years,” the report added.

In his Sept. 3 update, Tomasko said that he had just received the latest water sample results that day. A team representing not only his program but also the Southwest Florida Water Management District (SWFWMD) and Sarasota County Government had collected nine samples in the lower segments of Sarasota Bay, and only two were below the Florida Department of Environmental Protection (FDEP) threshold for enterocci bacteria, he pointed out. That threshold is 130 colony forming units (cfus) per 100 milliliters (ml).

Those samples were collected in south Roberts Bay on Aug. 8 and the southern part of Little Sarasota Bay on Aug. 29, he wrote.

Tom Higginbotham of the Florida Department of Health-Sarasota (DOH-Sarasota) has explained, “When [enterococcus] bacteria are found at high levels in recreational waters, there is a risk that some people may become ill.” He also has noted, “People, especially those who are very young, elderly or who have a weak immune system that swallow water while swimming can get stomach or intestinal illnesses. If water contacts a cut or sore, people can get infections or rashes.”

Tomasko also emphasized that the samples came from the middle of the bay, “not along the mainland shoreline. This means that bacteria levels would be expected to be higher still along the mainland shoreline.”

He acknowledged, “This begs the question — where did these bacteria come from? Unfortunately, we don’t know — but that is an important question. This ‘fecal indicator bacteria’ (FIB) is not restricted to humans, or mammals or even animals. It can arise from human sewage, but also bird poop on pilings, dog poop in people’s backyards, but also potentially from grass clippings and oak pollen (shown to be the case with other FIBs in Florida), or even decomposing seaweed. This is important, because FIBs like enterococci are not, by themselves pathogenic, or ‘disease causing.’ Most of the human health risk from sewage contamination is from viruses, and as the National Institutes of Health (NIH) has pointed out, “When the source of enterococci to surface waters is not fecal, their presence may not indicate a health risk [Tomasko’s emphasis].”

He stressed, “This last point does NOT mean that the water is safe to go in, because if the bacteria are not from sewage, but from all the worms and clams and starfish and stingrays that have died in the lower bay due to the low levels of oxygen we reported in a prior Director’s Note, then it could still be a problem. You obviously wouldn’t want your kids or grandkids to swim in sewage-contaminated waters, but you wouldn’t want them to swim in waters where the bacteria were due to thousands if not tens of thousands of dead fish either, right?”

Part of the reason the team focused on the lower bay segments in its latest sampling, Tomasko explained, is that the lower bay “is more susceptible to impacts from large rain events. Why more susceptible? Because there is much more land draining into much smaller areas of water in the lower bay, compared to the upper bay. The ratio between the amount of watershed and the amount of open water is close to ten times higher in the lower bay than in the upper bay. In the upper bay — except for Palma Sola Bay — there is a water exchange of about 80% after 10 days. In contrast, it takes about a month for the same amount of water exchange in Little Sarasota Bay.”

The latest sampling marked the third set done in the aftermath of Tropical Storm Debby, he wrote. The samples were collected approximately one week, two weeks and four weeks after the storm moved away from Sarasota County, he added.

Mote’s other storm assessments

In its Sept. 5 report, Mote Marine noted that it “is committed to utilizing advanced technology and science, coupled with community engagement via volunteer citizen scientists, to serve at the forefront of assessing the storm’s effects.”

In regard specifically to Tropical Storm Debby’s effects on water quality, the report explained that “Mote has, for decades, conducted comprehensive water sampling throughout Sarasota Bay through the National Environmental Laboratory Accreditation Program. As a result, it was able “to implement rapid response water quality sampling to assess Tropical Storm (TS) Debby’s impact on the bay’s delicate ecosystem. Initial analyses have revealed the following key findings of immediate water quality impact,” the report pointed out:

• “Turbidity and Water Color — Measurements of turbidity and true color of Bay waters were elevated. Elevated true color indicates an increase in substances such as dissolved organic matter in water, while elevated turbidity indicates increased particulate matter in the water —both of which were likely caused by massive amounts of stormwater resulting from the intense rainfall of TS Debby in the Sarasota Bay watershed. Elevated turbidity and true color led directly to reduced penetration of sunlight (light attenuation) into Bay waters.”
• “Dissolved Oxygen Concentrations — Mote water samples immediately following the storm also indicated a drop in dissolved oxygen levels at certain sites in Sarasota Bay. Dissolved oxygen fell below 3 mg/L [milligrams per liter], which is dangerously low, in North Sarasota Bay and near Stickney Point Bridge.”

“Storm events like Debby can have profound effects on our coastal environments,” said Dr. Emily Hall, manager of Mote’s Ocean Acidification and Chemical and Physical Ecology Research Programs, in the report. “These preliminary findings suggest that the storm has had a significant impact on water quality in Sarasota Bay. We are particularly concerned about the high nutrient and low dissolved oxygen concentrations, which could have serious implications for marine life in the affected areas.”

Then, under the heading “What This Impact Means,” the report explained, “Higher than normal nitrate and ammonia concentrations may lead to increased bacteria and algal blooms that can make the water murky and potentially lead to low oxygen concentrations in specific locations. If any potential bacteria and/or algae blooms are composed of toxin-producing species, such toxins may harm marine life and potentially pose health risks to humans and pets who come into contact with the water.”

Further, it said, “Reduced light attenuation can be problematic for benthic organisms like seagrass, which require sunlight for growth. When bacteria levels are also high, the breakdown of organic matter uses up oxygen, releases carbon dioxide (reducing pH), and releases nutrients into the water. The combination of low pH, elevated nutrients, and low oxygen concentrations can disrupt the balance of the ecosystem and further stress marine life. Dissolved oxygen is vital for fish and other aquatic life to survive. When oxygen levels are as low as some Mote water samples indicate, it can stress or even kill marine life, which could lead to fish die-offs and other ecological impacts.”

The report also noted, “Mote’s Beach Conditions Reporting System (BCRS) engages community members in scientific observation and is a valuable tool for communicating the presence of dead fish, respiratory irritation, water color, and wind direction at over 100 coastal sites in Florida, as well as in each state from South Carolina to Texas, plus California. BCRS (visitbeaches.org) is a free downloadable application that allows the public to view coastal conditions reports submitted by trained volunteers, and users can also contribute their own observations through the Community Science Portal on the BCRS.”

During the week after Tropical Storm Debby dropped more than 18 inches of rain in some parts of Sarasota County, the Mote report continued, “BCRS observations for individual sites in the Sarasota Bay area reported an increase from 0-2 dead fish observed at a site to over 2 dead fish per site. However, reports of dead fish declined back to 0-2 observations per site after that time. Overall, prior to TS Debby, only 6 BCRS sites in Sarasota County reported dead fish, while 31 BCRS sites in Sarasota County reported dead fish following TS Debby.”