Sargassum superblooms are choking coastlines around the Atlantic

[MUSIC PLAYING] FLORA LICHTMAN: Hey, it’s Flora, and you’re listening to Science Friday. An unwelcome visitor is arriving on beaches from West Africa to the Caribbean, Brazil to Florida. I will give you a hint. It’s brown, it’s stinky, and it’s more abundant than ever– sargassum, a type of free floating seaweed. It’s become a major problem for coastal ecosystems, communities, tourism, and infrastructure. So what is fueling the sargassum superbloom, and is there anything to do about it?

Joining me now is Dr. Brian Barnes, satellite oceanographer at the University of South Florida who studies sargassum. Brian, welcome to Science Friday.

BRIAN BARNES: Thanks so much for having me, Flora.

FLORA LICHTMAN: Thanks for being here. Introduce us to sargassum. What is this seaweed all about? How should I picture it?

BRIAN BARNES: Yeah. So sargassum is a floating macroalgae, macro meaning it’s big enough, you can hold it in your hand. And if you were to grab it, it kind of feels like a bunch of prickly blades of grass and has got these little, pea-sized, floaty structures in it, and that’s what keeps it at the surface of the ocean.

It’s been around for a long, long time. The first recorded observations that we have of it are from the Columbus days, the first trips across the Atlantic. And this is really a habitat in the middle of the wide, vast ocean. This is kind of like an oasis of life and activity in and amongst the sargassum rafts that are created.

FLORA LICHTMAN: So is the Sargasso Sea its epicenter, its HQ?

BRIAN BARNES: Yeah, historically, yes. So the Sargasso Sea is off the eastern coast of North America. And this is the area that was so named the Sargasso Sea because of this sargassum macroalgae. The little floaty bits in it are– resembled to Columbus grapes. And so there’s this grape in Portuguese is sargasso.

The Great Atlantic Sargassum Belt is something that is a new occurrence. It’s not this historical habitat that we know dates back to Columbus days. Instead, it stretches from the west coast of Africa, through the Caribbean, into the Gulf of Mexico, and then out into that Sargasso Sea area. But we never saw before this type of bloom in the records that we have, in the oral histories, in the satellite data. Instead, in 2011 was the first time we observed this bloom, and it’s really been getting bigger and bigger ever since.

FLORA LICHTMAN: Yeah. So when you say bloom, what do you mean? I mean, how is its abundance changed in recent years?

BRIAN BARNES: Yeah, so a bloom is an expansion of the biomass. And it happens seasonally for most things. Just like a plant, you have a life cycle whereby you have a growth phase and then some die back in the wintertime, perhaps. The sargassum goes through the same type of cycle. And what we see now every summer is that there is an expansion, a growth of the sargassum awesome, and impacts on the coastal environments in the Caribbean and so forth. And more so than just the seasonal expansion and decay, we now have a trend where every year that expansion reaches higher and higher heights, larger and larger abundances.

FLORA LICHTMAN: Do we what’s driving the boom?

BRIAN BARNES: Yeah, it’s really hard to tell. So there’s evidence that suggests some of the initial growth may have been supported by some deep water mixing. So in the ocean, the deep water generally has more nutrients. And if you have a good wind blowing over it, it can mix some of those nutrients up into the surface water and make it available for sargassum.

There’s also tons of rivers in the area, like the Amazon and the Congo and the Orinoco. These rivers can provide nutrients that can be used by the sargassum. And then, finally, that kind of community of life that exists in and amongst the sargassum, it kind of recycles nutrients within that own ecosystem such that sargassum can continually support and sustain its own growth.

FLORA LICHTMAN: So there could be a snowball effect, basically?

BRIAN BARNES: Exactly.

FLORA LICHTMAN: Hmm, it’s complex.

BRIAN BARNES: Yeah, always.

FLORA LICHTMAN: So you mentioned this community of life that it supports. You mentioned that animals hide in it. Does anyone treat it like a salad bar? Does anything eat it?

BRIAN BARNES: Yeah, yeah, of course. There are things that eat it, and there are secondary consumers that eat those things hiding in and amongst the sargassum. So it’s a huge– as I said, an oasis of life in the middle of the pelagic ocean. There’s structure. There’s food. There’s community and larger populations that span all the way from invertebrates, all the way to fish and birds and mammals, marine mammals.

FLORA LICHTMAN: So far, sounds great. When does it become a problem?

BRIAN BARNES: Right. So this is the tricky problem. It’s got a duality. Sargassum out in the open ocean, it’s a beneficial habitat. And it’s actually classified as essential fish habitat, which limits the amount that you can tamper with sargassum when it’s out in the open waters.

But the problem is, especially in these new environments that don’t have a history of sargassum, or at least not these levels of sargassum, that sargassum can wash ashore and start to have cascading effects, negative effects on the local ecosystems, economies, and so forth.

FLORA LICHTMAN: Give me some specifics around that. How does it become a problem?

BRIAN BARNES: Yeah, so sargassum, it comes in sometimes to particularly beach communities or coastal communities in huge aggregations, thousands of tons of sargassum. And it kind of is just this floating mass. So if you have something like corals or seagrasses that are on the bottom, these can get shaded by the sargassum that’s overlaying it. Or if the sargassum is thick enough, it can get actually physically smothered by that sargassum biomass.

Sargassum, as it kind of gets further up on the beach, piles up on the beach. We’re talking feet high of sargassum, just piled up on beaches. All of those critters that lived in and amongst the sargassum are in trouble because they’re no longer necessarily in the water, as well as for turtles. Turtles use the sargassum when it’s offshore. But if you have something– a huge barrier of sargassum preventing a young turtle hatchling from getting from the beach where it’s hatching out into the water, as it would start its next phase of life, there’s another huge impact in these coastal ecosystems.

It also starts to decay. When the biomass comes ashore, it starts to rot, decay. It releases a terrible smell that’s awful for residents and tourists. And also, that decay can also make a tea or a brown tide, as we call it, that impacts the water quality for the local ecosystems, as well.

FLORA LICHTMAN: What’s this year been like?

BRIAN BARNES: This year was pretty bad. It was the second worst overall abundance that we’ve ever observed in the Great Atlantic Sargassum Belt. The largest bloom that we had ever seen was last year. But the difference between last year and this year is that, instead of a lot of the sargassum being in the more offshore areas, there were a lot more sargassum in these areas that was available to wash ashore and impact the communities.

FLORA LICHTMAN: So there are these negative effects on ecosystems, on infrastructure, fishing, tourism. Are there solutions? Can it be used for something?

BRIAN BARNES: Yeah, it’s tricky. And there’s a huge effort towards valorization, turning the sargassum problem into something positive, or at least reduce the negative aspects of the sargassum.

FLORA LICHTMAN: But–

BRIAN BARNES: Yeah. The problem is, as we talked about, the decay of sargassum. The more a fresh material decays, the less value it has, the less ability you have to turn it into something of value. So you have to be very responsive to where sargassum is coming ashore. Sargassum impacts are generally pretty patchy. You may see a lot of sargassum in one beach and not on an adjacent beach. So you have to be very responsive to where sargassum is coming from, how quickly you can pull it out of the water and try and translate it into any of these products.

FLORA LICHTMAN: What about getting it before it reaches the shore?

BRIAN BARNES: Yeah, that’s often one of the best ways to really ensure that you’re getting the fresh part of the sargassum. But it does come with costs. You have to establish barriers, typically, that will prevent the sargassum from coming directly into the shore. And then you have to go collect it offshore, which is much more costly than if you were to wait for it to come all the way to shore. But, again, you’re increasing the amount of value that you can potentially get out of your sargassum and reducing the impacts of the sargassum as it comes into the coastal ecosystem.

FLORA LICHTMAN: I’m hearing a lot of challenges, Brian. Do these approaches seem viable to you?

BRIAN BARNES: It’s– yes and no. It is something that we have to do. Essentially, necessity is the mother of invention in this scenario. We have to deal with this. And so we are trying to overcome these challenges in various ways, by, for example, using satellite data to identify individual patches and make decisions as to whether or not those will come ashore. And thus, those would be the ones that we need to prioritize for offshore collection.

There’s also– in this context, there’s a regulatory framework that is really difficult to deal with. Again, you have to make that decision of where sargassum– when is it going to change from being that essential fish habitat to being a harmful algal bloom?

FLORA LICHTMAN: And this is your work as a satellite oceanographer. Are you sargassum forecasting?

BRIAN BARNES: Yes, absolutely. So we use two broad scales of satellite data. So some of them are global sensors that enable us to look at that entire sargassum belt domain, West Africa, all the way into the Gulf of Mexico, every single day. We can observe the sargassum current situation and make some broad projections on where sargassum may be moving.

But, again, with sargassum being very patchy, the forefront of research here is using high-resolution satellite data, so between 4 and 10 meter resolutions that can identify really small patches. And if you couple that with models that show where the water is going, again, sargassum is floating at the surface. So it’s responsive to where the water is moving. Coupling the hydrodynamic models with the satellite-based detections is really how we can start to make those predictions of where– not just where sargassum is, but where it’s going to be going in the next couple of days.

FLORA LICHTMAN: So you’re in Florida. Does Florida have a plan for dealing with this?

BRIAN BARNES: Oof. Each municipality in Florida has its own different way of dealing with it. So for example, the Florida Keys, much of it is a National Marine Sanctuary. So there’s even more limitations on what exactly can be done to collect sargassum or otherwise remove from beaches.

Some beaches, like in Miami Beach, they have regular beach raking that will collect any sargassum that washes ashore. And when they have exceptionally bad sargassum inundation events, they’ll just send the rakes out more often and collect more of that biomass to keep it off of the shoreline. So the management response varies between these various entities. But the sense is that this is going to become a kind of recurring cost, a recurring need as the sargassum situation continues into the future.

FLORA LICHTMAN: So doing nothing, it sounds like, isn’t an option in your view?

BRIAN BARNES: Yeah. From all of the partners that at least that I deal with that handle sargassum either on the detection, the modeling, the valorization, everyone views this as a problem that needs to be solved because it will be something that we are going to be dealing with in the future. So we come up with the best solutions and try and implement them as effectively as possible.

FLORA LICHTMAN: Dr. Brian Barnes is a satellite oceanographer and associate professor at the University of South Florida. Brian, thank you so much for joining me today.

BRIAN BARNES: Thanks so much, Flora. Great chat.

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FLORA LICHTMAN: One more thing– Science Friday is a finalist for best science podcast in the Signal Awards, and we need your vote. If you love the show, please vote for us. Sciencefriday.com/signal will take you right there. This episode was produced by Rasha Aridi. Thank you for listening. I’m Flora Lichtman.

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