Future of Sarasota’s red tide depends on winds

K. brevis
A cell of K. brevis, the species of microscopic algae that causes Florida red tide. - Credit: Mote Marine Laboratory, used by permission.

Sarasota and Manatee Counties are experiencing a red tide bloom, but it’s not certain yet whether it will become severe or spread to the north or south — a lot depends on weather.

For an update, WMNF News spoke with Dr. Vince Lovko. He manages the phytoplankton ecology program at Mote Marine Laboratory in Sarasota.

“Probably about a month ago now is when we first realized that there was some sort of red tide activity going on. Based on cell counts there appeared to be a bloom patch in southwest Florida and also in the Panhandle. But over those ensuing weeks additional sampling showed that there was indeed a bloom patch in both of those locations. And the one in southwest Florida has continued to expand. And also another big tool that we use is the satellite imagery that is available to us through USF optical oceanography lab.”

Where is the red tide now?

“So, it started in Sarasota County as a pretty small patch. Because we had that very first cell count that indicated red tide – or elevated Karenia brevis, the red tide organism – literally the stations on either side of that, to the north and to the south, were free of red tide. So it was one very concentrated location. Since then it has expanded along the entire coast of Sarasota County and also appears to be in Manatee County and possibly getting up into Pinellas County and also Charlotte County. Now, a lot of that is with a caveat because we don’t get regular cell counts from that area, although Florida Fish & Wildlife has had some counts from some of those areas to verify. So a lot of this we go by the satellite imagery. We get weekly samples from the Sarasota Healthy Beaches program. So that gives us a good way to monitor what is happening right along Sarasota County. And even though the winds have shifted offshore – which certainly decreases the effects that we see on the beaches because the aerosolized toxins are being blown off shore instead of on shore – we would also expect that that would blow the cells that are in the surface waters offshore, which according to the satellite data that does appear to be what’s happening. But we are still getting medium to high counts along Sarasota County from that Healthy Beaches program.”

Is this a typical time of year for red tide outbreaks?

“Yes. Yes it is. They can occur any time of year but we do tend to see a pattern of late summer and early fall is when we often start to see indications of activity.”

Why, what triggers it?

“That’s kind of a million dollar question. That’s something that we’re still trying to determine. It’s going to be a combination of factors, it’s not going to be any one thing. It’s a combination of nutrients, the cells being present and all of this happening in at the right place at the right time. As well as winds and currents and what’s happening even in the deeper parts of the Gulf might influence it.”

There’s no way to tell for sure where it will go next or how long this will last, but what would you guess based on what you’ve seen?

“Well, it’s difficult to say. As I mentioned, the winds are offshore right now, which according to the satellite imagery does seem to be pushing a lot of cells further off shore. Like I said, we still have fairly high counts along the shore as well. And the satellite imagery indicates that it might be expanding. So if the wind switched back to onshore, it would of course bring the cells and the effects closer to shore once again. But if the winds sustain offshore or turn onshore only briefly and then go offshore again it could end up dispersing the bloom. So at this point we just have to wait and see and keep sampling.”

How would you compare the scale of this outbreak compared to other reed tides?

“Well, you know, that’s very difficult to say at this point. This is the early stages of this bloom. Now whether that means it’s going to develop into a large bloom we simply can’t say right now. At this point I would call it a relatively small bloom. You know there have been some effects of both respiratory irritation and dead fish reported, primarily last week when winds were blowing onshore and we’re not seeing that right now due to the offshore winds. If the bloom from here disperses and we don’t get any further effects then I would call it a relatively minor bloom. If it continues to intensify and winds bring it to the shore again then that might be a different situation. It’s a little early to compare it to previous blooms at this point.”

Here’s a link to Mote’s Beach Conditions Reporting System

Listen to the full interview:



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