Ocean carbon sequestration: The climate solution hiding in seaweed forests

0:00 Seaweed forests may be one of the planet's largest natural climate allies, yet most are invisible to climate policy, unprotected by conservation laws and missing from carbon accounting entirely. While mangroves and seagrasses get the spotlight, kelp forest and other seaweed habitat are quietly doing the work without recognition, protection, or funding. So how can one of the most productive ecosystems on earth be almost completely ignored in climate solutions? We're gonna be talking about that on today's episode of the How to Protect the Ocean Podcast. Let's start the show. Hey everybody. Welcome back to another exciting episode of the How to Protect the Ocean Podcast. I'm your host, Andrew Lewin, Marine biologist and science communicator here to tell you what's happening with the Ocean, how you can speak up for the Ocean, and what you can do to live for a better Ocean by taking action.

0:48 And you're probably wondering right off the bat, Andrew, what's going on with your voice. If you listen to this podcast for any number of times, this is not my normal voice. If you're new here, this isn't my normal voice. I was at a hockey tournament. I coach hockey for my youngest and she's in new 18. We had a great tournament. We got to the semis, and I lost my voice. It just happens. This is what happens. I tried to do a recording beforehand, ran outta time, but now I am doing this recording because this is an important topic. We're talking about seaweed, not seagrasses, which I've talked about before. I've talked about seaweed before in terms of kelp, but we're gonna talk about a number of different things of seaweed, and I just want you to think, although I may not mention every species of seaweed or really a lot of species of seaweed. I'm gonna be telling you just about seaweed in general and how important it is in climate solutions in blue carbon capture.

1:34 Now, a lot of the times you're going to hear about carbon capture in Canada, you're gonna be here all around the world. A lot of oil and gas execs and supporters like to use the fact that they use carbon capture. Well, carbon capture can be done well except if you're putting out so much greenhouse gases. Carbon capture does not and has not been able to keep up with the demand. But we do have natural sources of carbon capture. Trees and forests are one, but they do not have the ability to take in as much carbon as you would think. When you have seagrasses, mangroves, kelp forest is a seaweed and other seaweed, you would be able to capture four to 10 times more carbon than any other tree on the planet. So. Why do we not focus on that?

2:16 Why are we not focusing on rebuilding or protecting seagrasses, mangroves and then the seaweeds like kelp so that we can better protect our planet against climate change? That is the question that we're gonna be talking about today, especially focusing in on seaweed. Kelp and other seaweed. The first thing we should do is define what blue carbon is. Blue carbon refers to the carbon captured and stored by coastal and Marine ecosystems. So traditionally it includes, like I said, mangrove, salt marshes even, and seagrass meadows. These systems trap carbon in sediments for centuries to millennia, which is great. They are recognized in climate frameworks such as National Carbon Inventories.

2:57 but there's a major carbon capturing ecosystem that is missing from that list, and that is seaweed. Seaweeds, including kelp forest and macroalgae grow incredibly fast, and a lot of times people don't like seaweed. We have to have a lot of problem with seaweed when we put our feet into the Ocean, if we're away on a trip to a tropical paradise, we see seaweed. We're like, ah, I don't like seaweed on my feet. It feels gross. But it's a naturally occurring thing. It's something that should be in the ocean. Now sometimes, it's a lot and sometimes it's not so much, but it's always there and people don't like it. Oftentimes in resorts and in anywhere where there's tropical areas where there's a high tourist attraction or a high tourist usage, you'll see dredging of the seaweed.

3:38 And dredging of the beach because people don't wanna see seaweed, so they'll clean up the seaweed. But it's a natural occurring It's required to be there in the ecosystems because part of the ecosystem, and it does a really good job at capturing carbon. The only thing is, is like even though they capture massive amounts of carbon dioxide through photosynthesis, much of their carbon isn't staying in that same area like seagrasses or mangroves. When seagrasses or mangroves take in carbon through photosynthesis, they actually put it into the sediments right below where they are. With algae, algae can break off and it can float across oceans through circulation patterns and so forth. And so the fact that they don't stay there is very difficult to measure how much carbon is actually being captured in that one area. That carbon can sink as it floats away.

4:19 A carbon can sink into the deep sea and it can be stored for hundreds of years in the deep sea, which is fantastic to have as it's naturally occurring. Seaweed does not store the carbon place like mangroves, but it exports carbon across the ocean, which challenges how we measure and value it. Why do seaweed meadows matter beyond carbon? We'll seaweed habitats like kelp forests, they support fish invertebrates and juvenile fish and all different types of life stages. They act as a coastal buffer against waves and erosion. They improve local water quality. Many of the coastal fisheries depend on kelp associated species as another seaweed species. So this is something that is huge.

5:01 If kelp forests disappear, entire food webs unravel, not just carbon pathways. Entire food webs unravel. So the central problem that the recent scientists have uncovered is that most seaweed ecosystems lack formal protection. Marine protected areas often don't consider kelp specifically. Seaweed is excluded from many blue carbon policies because it does not store carbon locally. So it's very difficult to measure the local carbon storage effect because seaweed is transported across oceans. So climate finance mechanisms rarely apply to macroalgae because even though we know the science of seaweed, it matters, but the policy hasn't caught up to what seaweed could do for the climate system.

5:41 So climate is only now uncovering the way that carbon is stored in seaweed and how much of it is actually stored in seaweed. And that's through improved tracking of carbon export pathways. So the fact is we start to be able to see how carbon is stored within seaweed and how it's traveled across the way. Now it's a number of different ways that we can see what's happening. Like we better model deep sea carbon sequestration. We better model ocean currents. We recognize that ignoring seaweed underestimates ocean carbon uptake, and of course, growing calls to expand the definition of blue carbon helps include different pathways such as seaweed in this carbon. Now, some of the ways that we can track carbon is very interesting.

6:24 So we have better ocean centers and autonomous platforms. So autonomous gliders, floats and underwater vehicles now carry biogeochemical sensors. So we can see where carbon is stored and we can also track where that carbon is coming from. So it's not just, this is Marine carbon. It's coming from, this is a carbon that was coming from specific species of seaweed. That's how good we've got it. So these instruments that we have, like these autonomous gliders, the floats, the underwater vehicles, these instruments continually measure dissolved carbon, oxygen, nutrients. They operate for months, even years, in some cases across coastal and offshore water. So these are huge, huge things. So seaweed carbon does not just stay where it grows.

7:05 These platforms let researchers detect carbon rich water masses moving offshore. Something that ships alone could not track this reliably. So you have to have something like this, some sort of improved systems like we do, like I just mentioned. Now of course we can use stable isotopes to better help distinguish seaweed derived from phytoplankton carbon. Biomarker compounds unique to macroalgae can now be traced in sediments and deep waters. So scientists can now say with far more confidence that this carbon came from kelp and not that just this carbon is Marine. Huge, huge aspect of that. Now of course we can also use particle tracking and ocean balls. This is something that I was going to be doing for my PhD. If I was gonna go through with it.

7:47 We were gonna be tracking particles within a network of Marine protected areas to see how these biological systems are connected within the marine protected area network to make sure that all the biology, all the larval stages will actually go to another part of the Marine protected area to ensure that is protected. So these high resolution circulation models simulate how seaweed fragments drift and sink particle tracking models follow carbon pathways from coastlines to the deep sea. And models are validated with real world sensor data that I just discussed before. We can also track kelp forests and kelp through remote sensing. So any kind of seaweed extend or productivity satellites can map kelp canopy extent and seasonal growth. So we can see the growth or even a retraction of that habitat from a number of different disturbances.

8:31 And then of course, long term data sets show how much biomass is produced each year. So you can't just estimate carbon export without knowing how much seaweed exists in the first place. So these satellite imagery are able to close this major accounting gap. And of course now linking the export to long-term storage sediment cores that these big long tubes that go into the sediment, right into the sediment, they can get a number of different layers depending on the size of the core reveals that macro algal carbon is buried at depth. And then genetic and chemical markers linked, buried carbon back to coastal seaweed. If you have the same markers, you can track it back to, like from the depth in like say the middle ocean to a coastal area that's nearby or even further.

9:12 And it's really cool to be able to have that. So the fact is, without these systems, we didn't know how much carbon the seaweed was actually bearing into the deep sea or around the ocean. And now that we have this, we know that we're underestimating the carbon capture and we know that there's more, and we're getting closer and closer to fully understanding how much the seaweed is not only capturing carbon, but also, that is dispersing it across the ocean. So here is what really needs to change when we talk about seaweed. We need to expand blue carbon definitions to include macroalgae, which is seaweed. Protect seaweed habitats through targeted marine protections, like marine protected areas of kelp habitats. And fund research into carbon export and sequestration.

9:53 This is something that's really important 'cause we don't have a lot of knowledge in it. And include seaweed ecosystems in climate and biodiversity planning. I can't stress enough how much biodiversity is in like a kelp forest. It is something that is huge, is a part of the ocean needs to be introduced and it needs to be shown how important it is. To be honest, doing this research was actually surprising that kelp hasn't been included in more of these policies or seaweed hasn't been included in more of these policies, I guess because of the way it gets dispersed across the ocean. But I'm glad we're seeing more progress to get it better. But as climate solutions become more urgent, overlooking powerful, natural allies like seaweed is a risk we can't just afford. The ocean is already doing the work, but only if we let it.

10:35 So we have to understand how the seaweed works, how it is able to be dispersed, and what it could do for climate change for us in terms of carbon sequestration. If we want real climate solutions, we have to start paying attention to the ecosystems we have that we've been ignoring for a long time. This is something that we've done for a while. We need to fund more research in this, to understand this. The solutions might already be there. We just might not know that they're there, and we may not know how we can play a role. So that's it for today talking about seaweed and climate solutions and blue carbon. It's something that is very important to fighting climate change, reducing climate change. So I encourage you to follow, subscribe to this podcast. Make sure you support the podcast not only for seaweed, but for seagrasses that we're trying to do.

11:19 Go over to speak up for blue.com/sea grass. We need to talk more about how these systems are so important for blue carbon and for doing something for climate change or to reduce climate change. And so going to speak up for blue.com/seagrass Supporting the Seagrass podcast as crowdfunded. I'm an independent podcaster. I wanna bring more information to you. I need your help, so go to speak up for blue.com/seagrass and hopefully my voice gets better when I start recording this podcast after it gets funded. I'm sure it will be. This is temporary. Might be for one other episode, but we'll be good in the long run. But I wanna thank you so much for joining me on today's episode of the How to Protect the Ocean Podcast. I'm your host, angel Lewin. Have a great day. We'll talk to you next time and happy conservation.