Autonomous sailboat deployed to find red tide bloom
By MEGHAN McCOY
An autonomous sailboat was launched from Algiers Beach to map and take measurements of where the red tide is located and what kind of environment it feeds off of to better understand the bloom that has been near Sanibel since Thanksgiving weekend.
“This is a company that we are working with, Navocean. They actually made the boat. We are just sort of the scientist consultants on it. We are trying to promote this awesome tool and trying to show how useful it is for our research. You could put any sensor on this sailboat that you want,” Dr. Jordon Beckler, Mote Marine Laboratory & Aquarium program manager of ocean technology research, said.
Before the sailboat was launched Navocean Owner & Chief Designer Scott Duncan did some tests from his iPad to make sure everything was working correctly. A chart on his device showed where they were located near Algiers Beach, and the six locations the sailboat would cover.
“We can reprogram its course,” he said of the fourth generation prototype. “We hope it will go out for three to four days. We are building up to 30 days and 60 days.”
Sanibel-Captiva Conservation Foundation Laboratory Director Eric Milbrandt said the neat thing is they can see everything in real time.
“You send out a ship, a ship costs $20,000 a day, whereas this is much lower cost. You can find the patches and study them a lot more readily. And matching up with the satellite imagery is really important as far as telling people where it is and what the probability that it will kill fish and have respiratory irritation,” Milbrandt said.
Beckler said the autonomous sailboat can cover the distance and take measurements of what would take a normal research team a couple days to do.
For red tide to have an affect on fish and respiratory irritation, it has to be in where the waves are breaking and aerosolizing, Milbrandt said.
Duncan, a boat designer and builder, said he has been co-developing the sailboat with a close friend of his, Ethan Arutunian, who is a electronic software engineer.
“Between the two of us we have put a few prototypes over the years. The idea first got started over a bottle of wine in the year 2000. We had this little toy,” he said of a little wooden sailboat model. “It’s been a while. There are now four people involved in the company. We are just turning the corner now to get this out into real projects and doing real research.”
The deployment Wednesday morning, he said was really exciting.
“It’s been a great collaboration with Mote Research Lab and Jordon has been awesome to help make this happen,” he said.
Duncan said you want to have mobile measurements, or a ton of sensor networks, such as the RECON, which provides stationary measurements.
“Just having one red tide sensor isn’t great, so these mobile measurements are worth so much more,” he said.
Beckler said he has been working with a glider for the past three years, which travels under water and samples a red tide bloom in three dimensions.
“It showed a patch that was under the surface, off-shore. By having a glider you can get a depth measurement. When the wind blows from a certain direction, it upwells and can bring the bloom to the surface and onto the beach. Knowing where those patches are is helping us better predict where the bloom is and what areas it will affect,” Milbrandt said.
Mostly the red tide blooms start appearing in November and end two, or three months later.
Beckler said anything done by space can be affected by other elements, such as black water where there is river discharge, which is why the sailboat is such a great tool.
“When you have a device like this (the sailboat) in the water that is measuring directly, it’s more reliable, especially in murky water like this,” he said.
Over the last three years, Beckler has been studying red tide, which he said is still hard for scientist to understand.
“In shore, in fresh water, they are so much easier to understand what causes those. Red tide is offshore and you don’t have a lot of measurements offshore. That is really the main issue. You don’t have a lot of presence offshore,” he said. “It’s expensive to get measurements out there. That is why it’s important to have an autonomous means to actually send out there to get measurements.”
A regular Mote Marine Lab red tide monitoring program is once a month, when they go out and get samples from a routine set of stations and interpret long time distance between that.
“You can’t catch these upwelling events when the wind blows. It’s really hard to catch that without continuous measurements,” Beckler said. “In a perfect world we would have a fleet of five of these things all over Southwest Florida just going all around.”
The strategy last Wednesday with sending out the autonomous sailboat was to figure out how close the bloom is to shore, which is why the predetermined areas ran horizontally east to west with increasing distances from shore.
“This way we will see nothing, nothing and then all of a sudden there will be elevated chlorophyll, probably red tide related,” Beckler said. “There’s no real way to verify that, which is the problem with just using chlorophyll measurements because it’s not specific for red tide, so we kind of have to have some other evidence.”
The Caloosahatchee River, atmospheric and ground water are the main sources of red tide.
“The contribution of each can change every year and that has sort of been the most challenging part of understanding where these form and why they last long, or short. They are hard to study,” Milbrandt said.
The continuous discharge from Lake Okeechobee, they said is a major source for total nitrogen and total phosphorous.
“The red tide has a salinity threshold because they don’t want to be in fresh water,” Beckler said. “They are out at the perfect distance offshore where there is a nice balance of nutrients coming out of the river and gets dispersed. Now you have this nice beautiful seawater environment where the red tide loves to live. Perhaps there are other controls like light levels with the water being so murky. Maybe they prefer some shadowy niche and don’t like too much light and now they have this continuous nutrient.”
Red tide tends to show up in November, which he explained scientist believe is because there is rain and atmospheric dust that comes with hurricanes. Beckler said the same storms that come from Africa with iron rich dust eventually rains out in the Gulf of Mexico.
“The iron rains out and can stimulate this other organism called, trichodesmium, which we actually saw a bunch of yesterday,” Beckler said last Wednesday. “Trichodesmium makes some nitrogen that the red tide can use. It is iron dependent in this process, so that is kind of the dust connection and that explains the timing because you usually have this wet deposition during hurricane season. A couple weeks later you have a trichodesmium bloom. A couple weeks later you have this red tide bloom.”
That process, he explained is more favored to happen offshore.
“Maybe that supports the big blooms. Maybe when you have specific years like this year when you have a high river discharge that supports the more local blooms,” Beckler said.
Milbrandt said the bloom they were researching was first detected the Saturday after Thanksgiving. He said it was pretty intense with fish kills around the Tarpon Bay Road area.
The red tide bloom has been progressing south, starting around Captiva Pass and as of last week it was south of Sanibel.
“It seems to be trending to dissipate,” Milbrandt said.
Duncan said when they deploy the sailboat in January it will have another update with sensors that would enable it to send real time data while out on the water.
“Then you actually see where the bloom is right there at that moment,” he said.