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All About HABs: Uncovering the Mystery of Harmful Algal Blooms

NOAA Ocean Podcast: Episode 20

Harmful algal blooms ( HABs) ... it's a term that many people became familiar with in 2018 due to a persistent "red tide" event along the Gulf Coast of Florida. In this podcast, we uncover what HABs are, what they aren’t, and how we can learn to minimize their effects on our daily lives.

view of a large harmful algal bloom event in Lake Erie, September 2017.Photo credit: NOAA Great Lakes Environmental Research Laboratory

An aerial view of a large harmful algal bloom in Lake Erie, September 2017. Photo credit: NOAA Great Lakes Environmental Research Laboratory


HOST: You’re listening to the NOAA Ocean Podcast! I’m Megan Forbes and in this episode we’ll be talking about harmful algal blooms. We’ve been hearing this term in the news of late with the events that have been occurring in Florida for quite some time now. I wanted to understand more about the overall phenomenon of harmful algal blooms – so I’ve invited Steve Kibler, an oceanographer with the National Centers for Coastal Ocean Science at NOAA to talk more about them. Steve works at the NOAA lab in Beaufort, North Carolina. Welcome Steve! Thanks for joining me!


HOST: Let’s get right down to it – I have a lot of questions about harmful algal blooms, or HABs as we sometimes refer to them. Red tide or harmful algal aloom…? Are they the same? Are they different? Can you tell me more...

STEVE KIBLER: The term "red tide" is an older term for harmful algal blooms. It was based on people’s perception of the change in color of the water when certain types of blooms happen. It doesn’t mean that the water always turns a reddish color – sometimes it can be green or brown or even more exotic colors, but that’s where “red tide” comes from.

HOST: So the color is based on the color of the algae that’s in there?


HOST: Okay. What is making the algae harmful?

STEVE KIBLER: Well, algae can be harmful in a lot of different ways. Generally, when you say the word “algae” to somebody, they think of seaweed, they think of large plant-like creatures they see on the beach, for example. What we’re really talking about here are microscopic algae or microalgae, generally they are individual cells that occur at high density in the water, and they’re dense enough that they can discolor the water. They can be harmful in a number of different ways; talking about Florida red tides, for example, the cells produce a type of toxins, there’s a whole category of them, they’re called brevetoxins, and the species involved is Karenia brevis. So, brevetoxins are a potent neurotoxin, and they can cause mortality in a lot of different marine organisms. If you have a high enough dose, they can also be harmful to people as well.

HOST: Neurotoxin means that it affects your brain, correct?

STEVE KIBLER: That's right

HOST: So that’s why I’m hearing about people’s eyes stinging and burning, and not being able to breathe…it’s not that they’re seeing these floating flats of plants, it’s that its tiny... microscopic. Is it getting into the air? How does it get into our lungs, for example?

STEVE KIBLER: So in a Karenia brevis bloom, for example, the cells are relatively fragile and are easily broken by wave action, by wind…and so the toxins themselves are aerosolized into tiny particles. So, if you happen to be on the beach during a bloom, the toxins end up in your eyes, you can breathe them in, and they typically cause asthma-like reactions in people that are sensitive.

HOST: Mmm hmm. So with the waves, they’re breaking up the algae itself and the toxin is being released. People aren’t breathing in the algae…just the toxin that is within the algae.

STEVE KIBLER: That’s right.

HOST: How can somebody tell when a harmful algal bloom is occurring?

STEVE KIBLER: Generally, it goes back to the term “red tide” again…it’s this visual perception. You can actually see a dense accumulation of material in the water, and maybe it discolors the water…there sometimes can be funny smells...there can be other effects like dead marine life – floating dead fish, for example. It’s generally fairly obvious when a bloom is dense enough for people to be able to see. The real problem is blooms where you can’t really tell – they’re not dense enough to be perceivable by human eye, but their effects can still be there.

HOST: How does it affect the animals in the water? Is it that they’re ingesting the water, or even through contact with their skin? Is that how it is affecting them?

STEVE KIBLER: So the brevetoxins in a Karenia brevis bloom are absorbed through mucous membranes. So for fish, the toxins are absorbed through the gills. In other types of organisms, it comes through ingestion. Manatees, for example, which graze on seagrasses, the cells in the toxins can accumulate on the surface of the seagrass so that when they’re eating the grass the ingestion arrives through their stomach. And then in humans, if we were to ingest shellfish that are occurring where there is a bloom, you can get a dose of the toxins directly through the shellfish themselves.

HOST: You specifically mention shellfish – I remember seeing that, going to the coast – “Red Tide…please don’t ingest shellfish”. Why shellfish over finfish?

STEVE KIBLER: Well, shellfish feed by filtering out small particles in the water…mostly harmless types of phytoplankton that naturally occur…but when there is a harmful algal bloom happening, they also ingest a lot of the harmful algae themselves. So the cells and the toxins can accumulate in the tissues of shellfish more so than other types of organisms, and so typically, the state will post closures for shellfishing to prevent people from coming into contact during a bloom. But, there’s also economic damage that comes along with that…coastal communities that depend on tourism and depend on seafood and the seafood industry can really be damaged by an occurrence of a harmful algal bloom. There is precedent for Federal relief and disaster mitigation money that at times is made available because of the effects of these blooms.

HOST: So are harmful algal blooms only found along the Gulf Coast or can they be found in other coasts as well?

STEVE KIBLER: There are harmful algal blooms throughout the U.S. – throughout the world, really. They can occur in marine environments and also freshwater environments. We’re just talking about different species of algae that can be causing them. In Florida, Karenia brevis is a very common harmful algal bloom cause, and it also occurs across the rest of the Gulf and even into Mexico as well. In different parts of the U.S., for example New England states, the harmful algal bloom that occurs there is called Alexandrium catenella. It’s a similar type of organism, but different species and different toxins are involved. And there are also blooms on the west coast of the U.S., all the way up to Alaska, different blooms in Hawaii, and the inland states in lakes and reservoirs.

HOST: What is the actual cause of a harmful algal bloom – have you been able to determine what specifically is causing this?

STEVE KIBLER: So, harmful algal blooms are a natural process. They’ve occurred long before humans lived in the U.S., for example. Some of the earliest history of European colonists recorded harmful algal bloom problems when they arrived in Florida, back in the 1500’s. However, humans can cause environmental changes that promote the development of harmful algal blooms, maybe making them worse. For example, a common trigger for freshwater HABs is nutrient runoff. In a small pond or reservoir, within a housing development – retention ponds are a common place to see freshwater harmful algal blooms happening. Sometimes they can be toxic, sometimes they just look gross…they discolor the water, smell funny, cause fish kills…but nutrient runoff is a very common one for freshwater environments. Not so much on the coast where it’s more of a natural progression of wind, weather, and ocean currents that often drive these.

HOST: So when you say “nutrient runoff”, can you explain that a little bit more?

STEVE KIBLER: Sure. When I say “runoff” it means, simply, dissolved chemicals that are in the water on the land. This can be because of rainfall or because of farm irrigation, can be effluent from sewage treatment plants. All this material ends up in the water system and then eventually makes its way to the ocean, and coastal environments often times see high levels of nutrients just because of this runoff. This can contribute to harmful algal blooms.

HOST: We’re all connected, right? We always talk about how water [exists from] “rivers to the sea”, and that truly happens.

STEVE KIBLER: That’s right!

HOST: You’ve said that this is a natural occurrence...is there any way to stop it from continuing, or to prevent it from occurring?

STEVE KIBLER: There’s a little bit that can be done to prevent it – situations where runoff can be controlled can sometimes help prevent the development of harmful algal blooms, or make them so that they’re less severe. But in other instances, it’s a natural offshoot of human population growth, so it’s much more difficult to get a handle on. It’s hard to get millions of people to change the way that they live, and, in a sense, there’s probably no easy way to prevent harmful algal blooms from occurring in most instances. Like in the Gulf of Mexico, for instance, we’re talking about a large regional area where the cells can be distributed over thousands of square miles and there’s just simply no way to be able to remove these from the environment without harming the environment itself.

HOST: Yeah, so removing it may actually do more harm than good.

STEVE KIBLER: Right – then you have the toxins to deal with as well, which may already be dissolved in the water.

HOST: Would you consider yourself a harmful algal blooms specialist?

STEVE KIBLER: Uh, yeah, I guess that’s one way of putting it. My own background is in oceanography – so I’m interested in the physics and the chemistry of the oceans, and how they drive or limit harmful algal blooms. But, I’ve really gotten involved because of the human side of it and some of NOAA’s role in mitigating these problems in the environment.

HOST: How is NOAA involved in HABs?

STEVE KIBLER: So we’re involved in a number of different ways...to go right to the legislation, there’s currently HABHRCA, which is the harmful algal bloom Hypoxia Research and Control Act, which basically gives us a legal mandate that we’re supposed to be studying harmful algal blooms, looking for ways to mitigate their effects, and looking for ways to provide early warning when a bloom is going to occur, or where it’s going to be severe. There’s a whole bunch of different mechanisms that we can use to do this – not just basic research in our own laboratories, but also through funding other organizations. There are really three funding levels that we can use to do this: one is called the ECOHAB Program – which is the ecology and oceanography of harmful algal blooms – and that provides funding for Universities and other individual groups to look at the ecology of the organisms and why they bloom, where they occur and why they do what they’re doing to do. There’s also MERHAB, which stands for Monitoring of and Event Response to harmful algal blooms, that’s a more practical approach providing funding to look at methods for testing technologies to detect toxins in the cells themselves, and ways to characterize their abundance, for example. And then the third one is called PCMHAB, which is Prevention, Control and Mitigation of harmful algal blooms, and that is funding focused on what can be done to prevent people from coming into contact with harmful algal bloom effects, to better inform the public and to provide more directed early warning products for harmful algal blooms. There’s a good example of another product that NOAA produces which is a forecast. So NOAA uses harmful algal bloom forecasting as a way to provide early warning to coastal citizens, to healthcare organizations, to the government, to regulating agencies – to give them information to try to help mitigate the effects of harmful algal blooms, and to direct resources towards detecting them and preventing people from coming into contact with them. This is a weekly update that is provided. The way that this forecast works is that we combine many of the resources that NOAA has at its disposal – so we have satellite information, we have researchers on the ground, people working to collaborate and coordinate some of the coastal communities to try to help them focus their efforts as well. And, what is produced is an early warning – much like a weather forecast – that shows people where the blooms are in any particular week, and also gives some idea about where we think that they are going to go in the future.

HOST: It’s as if you had ESP – you knew all the questions that I was going to ask you as you were explaining that! That was a good overview. Where can we, as the public, access these types of forecasts?

STEVE KIBLER: The best way to get to the link is just to search for “NOAA harmful algal bloom Forecast” - that will take you right to our forecasting page where we list the resources that are available. We also have a series of other products that are still being produced, that are still in the experimental stage. We’re working with private organizations and academic institutions to try to get these in place in the coming years. I mean, ultimately we work for the American public, so we’re trying to provide resources and guidance on how we can best get the information out where it’s most needed. So forecasting is one approach that is used.

HOST: I only have one more question for you, Steve, and that is, what should people do if they are in an area where a HAB is occurring?

STEVE KIBLER: Because there are so many different types of HABs, it really depends on the particular type of area. For the most part, you should pay attention to closures, for example, if shellfishing is closed by the state government or by the county, there’s a really good reason for that. So just be aware of these different types of warnings that are posted. Often times on the news and in the newspaper they’ll have details about harmful algal blooms, where they’re occurring. Generally speaking, if there is a bloom going on and there is dead organisms in the water, people aren’t typically going to go in the water anyway. Don’t drink the water or allow your pets to come into contact with it.

HOST: Well I think that is all we have time for today. Thanks so much, Steve, for talking with me about this very interesting, very pertinent natural phenomenon that we’re experiencing all over the world…harmful algal blooms.

That’s it for this episode of the NOAA Ocean Podcast. Thanks to Steve Kibler for educating us on harmful algal blooms…what they are, what they aren’t and how we can learn to minimize their effects on the natural world and our daily lives. To learn more about this science, or any ocean-related topic, visit our website at oceanservice.noaa.gov. We appreciate you taking the time to learn with us, and hope you’ll join us again soon. Until then…thanks for listening.