So far, no signs that red tide will be major problem this year, executive director of Sarasota Bay Estuary Program reports to local government leaders

David Tomasko provides local government leaders overview of current conditions

David Tomasko. Image courtesy Sarasota Bay Estuary Program

The executive director of the Sarasota Bay Estuary Program (SBEP) has offered what he calls a “good news/bad news” outlook on the likelihood that red tide will prove to be a problem for the area in coming months.

In a June 16 report on the SBEP website, which he emailed to local government leaders in Sarasota and Manatee counties, David Tomasko pointed to positive signs as of that period but cautioned that people need to do more to reduce the amount of nitrogen that flows into Sarasota Bay. Researchers have found that nitrogen is the primary food for the red tide algae, Karenia brevis.

Tomasko referenced wastewater treatment plant improvements that the Sarasota County Commission has authorized and that county staff has taken to lower the amount of nitrogen discharged into Sarasota Bay. However, he also offered details regarding other factors that can facilitate red tide, including the weather.

Thus far, recent weekly updates from the Florida Fish and Wildlife Conservation Commission (FWC) have indicated no more than background or very low levels of Karenia brevis offshore of Southwest and South Florida counties.

The last FWC update issued prior to the publication of this issue of The Sarasota News Leader — on June 17 — said that the algae “was observed at background and very low concentrations offshore of Collier County.”

This is the red tide forecast map for the west coast of Florida, produced through collaboration between the University of South Florida and the Florida Fish and Wildlife Conservation Service. Image courtesy USF and FWS

The previous FWC report, released on June 10, noted “very low concentrations [of the algae] offshore of Lee County, background concentrations in Collier County, and background concentrations offshore of Monroe County.”

On June 3, the update pointed again to “background concentrations” in Lee County and offshore of Collier County.

A week earlier, on May 27 — just before the start of Memorial Day weekend — FWC reported no observations of Karenia brevis in samples collected statewide over the previous week. Yet, on May 20, background concentrations once more were noted — this time offshore of both Manatee and Collier counties.

‘Red sky at night’

A red sky at night is a sailor’s delight. Image courtesy Sarasota Bay Estuary Program

“First, let’s do the ‘bad’ news,” Tomasko wrote in his report. “If you’ve been watching the news about weather out west, it is incredibly hot and dry out there lately. Also, if you’ve been watching sunsets over the past few weeks (like I do) you’ve seen some beautiful red and orange ones off to the west. The old guidance of ‘red sky at night, sailors delight’ reflects the fact that red skies indicate more particles in the air, which preferentially scatter blue light. These atmospheric particles are typically associated with descending air masses, which are also high-pressure systems. These high-pressure systems to the west indicate low pressure systems to the east, since high and low pressure systems typically pair. Since our weather mostly moves west to east and since high pressure systems are less scary to sailors then low-pressure systems, that’s why a sailor loves seeing red sunsets. Same reason for ‘red sky at morning, sailor takes warning’ — since that indicates a high to the east, and a paired low-pressure system to the west (where our weather comes from). And sailors hate low pressure systems, because they are associated with tropical events, for one thing. This long-standing guidance is also noted in the Bible — Matthew 16:2-3.

“Unfortunately,” Tomasko continued, “our current atmospheric high is also loaded with dust from the Saharan Desert, according to NASA — A Burst of Saharan Dust (nasa.gov). Check any websites on Texas weather and you’ll see they are quite concerned about that dust fallout — not good if you have asthma or COPD [chronic obstructive pulmonary disease]. But also, Saharan dust contains lots of iron. … As these events bring Saharan Dust across to Texas and the southwest, they not only make it hot and dusty weather for folks out west, but these events also add a lot of iron to the Gulf of Mexico.”

On the Sarasota Bay Estuary Program website, Executive Director David Tomasko includes with his red tide outlook this photo he took five years ago on a flight from Jeddah to Riyadh, in Saudi Arabia. ‘It’s the Arabian Desert, not Saharan, but similar and at the same latitude,’ he wrote. ‘All that pink to red tint in that photo is from the high iron content of the sand and dust.’ Image courtesy of Tomasko and the Sarasota Bay Estuary Program

Tomasko then explained, “The reason why this matters is that iron added offshore in the Gulf can stimulate the growth of an organism called Trichodesmium, or ‘sea saw dust.’  These guys can make nitrogen fertilizer out of the 78% of our atmosphere that is inert di-nitrogen gas. Add iron to the Gulf, and it’s much easier for Trichodesmium to grow and make more nitrogen ‘fertilizer’ out in the middle of the Gulf of Mexico. With more Trichodesmium, you can supply more nitrogen to incipient blooms of the red tide organism, Karenia brevis. While red tide blooms originate offshore, once they get advected into our nearshore waters, they tend to become larger, more intense and hang around longer if there are human-related nutrient loads in those nearshore waters … Keep in mind that our estimates from Tampa, Sarasota and Lemon Bay and Charlotte Harbor suggest we are loading about 2 to 3 times as much nitrogen into our coastal waters as was the case before our watersheds were as fully developed. Once red tides get intense enough to start killing fish — at about 1 million cells per liter or so — then they start to make their own ‘fertilizer’ from the decomposing fish they’ve just killed.”

This is a June 3 satellite image provided by NASA showing a Saharan dust storm. Image courtesy of NASA.gov

The county’s Bee Ridge plant and Piney Point

This graphic shows the location of Piney Point. Image courtesy of the Florida Museum at the University of Florida

Nonetheless, Tomasko noted, “The good news is that while we may already be getting red tides initiated offshore from iron-triggered Trichodesmium blooms, we have yet to … experience the types of human-related nitrogen loads to our nearshore waters that we’ve experienced lately. Before the massive 2018 red tide blew up in our local waters, we experienced 10.5 inches of rainfall in May of 2018 — the highest amount of rainfall during that month in over 100 years, and more than three times the long-term average for that month. We were also experiencing peak overflows of high nutrient effluent from the Bee Ridge [Water Reclamation Facility, which is a Sarasota County structure]. [It added] a nutrient load of 6 tons of nitrogen … to the bay in 2018 alone — the worst overflow-related loads to our bay in over 20 years. Prior to the worst red tide experienced by Middle and Upper Tampa Bay in over 50 years (in 2021) discharges from Piney Point loaded the equivalent of about 80,000 bags of fertilizer into Tampa Bay.”

Tomasko continued, “So where are we now? Bee Ridge [facility] overflows are almost completely gone, and that plant is already working to upgrade to [Advanced Wastewater Treatment status] AWT, so that any potential future spills would have 80[%] to 90% less of an impact. The City of Bradenton’s WWTP [wastewater treatment plant] overflows (over 100 million gallons) are being acted upon and impacts from those overflows are being ratcheted back. We’ve had no discharges from Piney Point into our coastal waters in over a year. As we pointed out earlier, 2021 showed evidence of the best water quality across our bay than at any time in the past 5 to 15 years. While we should be very proud of that, we do still have issues out there — the loss of 2,000 acres of seagrass in the upper bay has not yet been recovered, and we have an intense but hopefully localized macroalgae bloom along a portion of Sarasota Bay where large amounts of an extensive mangrove forest’s canopy was cut down and then left to decompose in our bay. This doesn’t help.

“Although we are in the beginning of our wet season,” he noted, “and we still have over-fertilized landscapes and aging stormwater and wastewater infrastructure, we are likely in a better place then we were in 2018 and 2021. We may get a red tide advected into our bay — or maybe not. Right now, satellite imagery and data from ongoing monitoring efforts carried out in our local waters do not show evidence of red tide. But while we can’t control the initiation of red tides, we can act to reduce the human-related nutrient loads that make red tides worse. With Saharan dust clouds streaming across the Atlantic, this is a good year to maintain our vigilance.”

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