Bayden Russell
Description: Bayden Russell is the Associate Director of the Swire Institute of Marine Science and an Associate Professor at the University of Hong Kong. His research focuses on ecosystem restoration and conservation through nature-based solutions. In this episode we talk about Hong Kong’s unique history of oyster reefs and farming and the potential use for oysters and other “filter feeds” in ocean conservation efforts. Professor Russell explains the difference between ecological functions and the potential for marine systems to sequester carbon. He also highlights the complexity of our fragile ecosystems and how we can better coexist with them.
Websites:
Publications:
The Future of Blue Carbon Science
Articles:
Show Notes:
[0:00] Introduction and Background
[3:47] History of Oyster Reefs in Hong Kong
[7:08] Population Size of Oysters Over Time
[10:02] Benefits Comparison: Oyster Farming vs. Reefs
[12:02] Strategies for Oyster Farming
[14:39] Formation and Growth of Oyster Reefs
[15:49] Quality Differences in Farming Methods
[17:21] Impact of Pollution on Filtration Process
[21:17] Filtration Process in Other Filter Feeders
[22:36] Pearl Production in Bivalves
[25:01] Best Practices for Eating Filter Feeders
[27:01] Designing an Ecosystem-Friendly Aquaculture Farm
[30:10] Issues Facing Oyster Reefs and Recovery Debt Theory
[31:29] Ecosystem Functions vs. Services
[32:42] Valuing Ecosystem Services
[34:06] Oyster Reef Restoration Methods
[35:42] Challenges in Oyster Shell Availability
[37:27] Synthetic Calcium Carbonate for Restoration
[38:37] Making Concrete-Like Material for Restoration
[39:37] Decline in Recovery Rates
[43:45] Effects of Ocean Acidification and Hypoxia
[52:32] Resilience of Sea Urchins to Heat Waves
[56:24] Importance of Keystone Species
[57:08] Understanding Blue Carbon
[1:00:19] Valuation Challenges in Carbon Markets
[1:03:12] Giving the Ocean a Chance: Nature Credits
[1:05:10] Achieving Holistic Environmental Solutions
Unedited AI Generated Transcript:
Brent:
[0:00] Welcome, Professor Bayden Russell. Thank you for coming on today.
Bayden:
[0:03] Yeah, thanks for having me. It's going to be good to chat.
Keller:
[0:06] We'd love to start off by hearing a little bit more about your story. What got you interested in marine science and how you ended up in Hong Kong?
Bayden:
[0:13] Yeah, so I actually grew up by the beach. Grew up, you know, fishing and catching crabs and those sorts of things. You know, basically just my summer holidays were, you know, down the beach any chance I could get. Um and you know i started to notice over time as i was growing up that actually there were less there was less fish there was less crabs and you know even by the time i was in you know early teen i knew that i wanted to understand that more and and kind of thought well i'll be a marine biologist was was my thinking um yeah so that's kind of where it started and then honestly i fell in love with scuba diving not long after that, and that kind of got me away from fisheries and that thinking and more into how subtitle ecosystems function, and sort of started following that line and just really started to follow that passion and what I found interesting and followed that along.
Bayden:
[1:15] Started working on the Southern Great Barrier Reef for a few years. Then moved to South Australia to work in the kelp forests down there, trying to understand how nutrient pollution was affecting kelp forests and the functions. And then I had the opportunity to work in China, and so I was actually on a research fellowship in China, and I was flying back through Hong Kong back to South Australia, and a colleague of mine said, oh, so. Okay.
Bayden:
[1:47] Did you know we've got some jobs going? And the rest is kind of history. I ended up applying and got the job here in Hong Kong.
Brent:
[1:54] So did you grow up scuba diving the Great Barrier Reef?
Bayden:
[1:58] So I grew up a bit further south than that, sort of north of Brisbane.
Brent:
[2:02] Yeah.
Bayden:
[2:04] But very quickly, when I was young, it wasn't on the Great Barrier Reef. But then very quickly, once I got into research, it was all about the Southern Great Barrier Reef and spent a lot of time on heron island and and working in around there yeah.
Brent:
[2:17] No because we i just got my advanced scuba certification in malaysia he got his first uh first certification and we could already see like what seemed to be like the remnants of changing reefs and just it would have been great because my dad traveled to the great barrier reef when he was 18 and he's like 50 something now so he would say like it used to have like 300 feet visibility i don't know if he's actually actually if it's accurate or not but.
Bayden:
[2:49] Yeah i just.
Brent:
[2:50] See the changes to where it is now would be crazy.
Bayden:
[2:53] Yeah absolutely um i mean without a doubt that sort of visibility existed i mean some of the the diving i've done on the great bay reef you know 50 meter plus visibility you kind of you kind of stop guessing when it gets out above 30 meters right you kind of go it's kind of 50 um absolutely and and i have revisited some of the sites that that i was diving in the sort of late 1990s and absolutely it's been it's been affected by you know a range of different things not in the least climate change and i haven't even been back there in the last five or six years when you know heat waves and coral bleaching have really become intense tense um but you could see the change certainly from the 90s until the sort of early 2010s which is the period that i spanned you could absolutely see the change for sure.
Keller:
[3:47] Then looking towards Hong Kong, could you give us a brief overview of their history with the oyster reefs and oyster farming?
Bayden:
[3:54] Yeah, so that's a really fascinating topic, actually. We've known for quite a while that there's this really long history of oysters in Hong Kong. It's a really big part of the culture. There's actually a species of oyster which is named after Hong Kong. You know, this is where it is native, the Magallana Hong Kongensis. And so, you know, it's this sort of pride in the culture. But the history is really interesting. Back, you know, a couple of thousand years ago, Hong Kong was obviously just, you know, sort of a few interconnected fishing villages. Villages um but then uh about a thousand years ago give or take a bit um there was a bit of an industrial boom not industrial construction boom in southern china and lime which is a key component in you know cement for buildings you can burn oyster shells to make lime and so you know a 1,000, 1,200 years ago, the first real industry in Hong Kong was harvesting oysters from oyster reefs and burning it in lime kilns to provide lime for the construction.
Bayden:
[5:18] And so we've just recently put together the historical sort of baseline for that, and we know that over-harvesting was driving sort of the first decline in that industry because of over-harvesting at least 1,000 years ago was the first decline. And then, you know, they stopped harvesting as much and then the reefs kind of came back. And then there was another sort of massive decline in the early 1800s through to sort of early 1900s. Basically, at that point, they were completely overfished, all of the hard substrate had been removed, and oyster reefs functionally don't really exist anymore. But the interesting part about that is that in that second period through the 1800s to 1900s, as there was that decline in natural oyster reefs because of dredging and harvesting, the increase in aquaculture started. And so where the reefs used to be on the mudflats and the sort of those shallow areas, they started to actually develop aquaculture farms. And so you kind of had the decline of one industry through the destruction of an entire habitat and then an ecosystem and then the increase in aquaculture to sort of replace some of that supply.
Bayden:
[6:43] So it really is a story that goes back. We've got documents dating back sort of 5,000 years, and it's really quite fascinating when you think about those sorts of timelines.
Brent:
[6:53] Yeah, that's crazy. So, do you guys have an estimate on the population size of the oysters prior to the harvesting for construction and now for aquaculture?
Brent:
[7:09] Like, are we close to replacing it or nowhere close?
Bayden:
[7:12] Yeah, not even close. Close. There's a couple of reasons for that. So the aquaculture itself has, when it first started, it was intertidal. And so it was only in the intertidal flats when the water went out that they were managing the farms. So that doesn't go anywhere near the subtidal areas that they'd dredged. And so you've actually lost all of that subtidal habitat. Even when they modernized the The farming away from literally sticking either rocks or concrete poles in the mud in the intertidal through to floating rafts, they still don't have that density of oysters that there would have been under the natural ecosystems when the reefs are properly formed. So, no, nowhere near the number of oysters or the density or biomass of oysters that they used to be. And honestly, the only way we'll get back to that is to sort of really kind of ramp up restoration and try and get some of these systems back.
Brent:
[8:20] And then how did the oysters build the reefs? Do they grow on top of coral reefs? Do they grow reefs in the same mechanisms that corals do? How does that work?
Bayden:
[8:29] So, there's actually some pretty cool biology and ecology in this in that oysters and corals are basically segregated in a lot of places because of the environmental conditions. So, you know, coral reefs need nice clear water, full salinity, oceanic type, you know, water, you know, no pollution or as little pollution as possible. You know sort of pristine you know that's what you think of with coral reefs oysters because they're filter feeders and actually don't need the sunlight like corals do they live in more estuarine areas it's a little bit muddy it's you know a little bit darker you can have you know some excess nutrients and you know stuff in the water so what you find is that certainly in hong kong there's a really good example in the eastern waters which are oceanic influence you get the corals and in the western waters, which is very much influenced by the Pearl River Delta, you get the oysters. And so you don't actually have the competition between those two because they're segregated by environmental conditions.
Bayden:
[9:40] As for how oyster reefs grow, effectively the same way. So you get oysters settling and growing on top of other oysters or dead shells and then And over time, as you go through generations, the reefs just sort of grow up steadily and form these big 3D structures that we call reefs.
Keller:
[10:03] Are there similar benefits to the ocean ecology to farming the oysters versus the reefs themselves?
Bayden:
[10:11] Yeah, there's this new concept called restorative aquaculture. And it's a really interesting concept because if you start to think about farming, you know, aquaculture farms in a way that you can maximise the benefits for the environment, then you can actually do things a little bit more environmentally sustainable. Yeah.
Bayden:
[10:38] So, I mean, the direct answer is no. You don't get the sum total of those same benefits. And mostly because you don't have that same 3D structure that you do. So in aquaculture farms, you don't have that same 3D structure that you do in reefs. And in fact, with aquaculture, to maximize the growth rate, to maximize your production, you don't actually want that density, right? You actually want to space your oysters out a little bit. Um, so, you know, you're not getting that density, the structure, and that means you're not getting as many species living in and around them. Um, you're not getting that same biodiversity effect. You're not getting, just because of the sheer numbers, you're not getting the same filtration rates and denitrification and all of those sort of services that we think of with oysters. Oysters um but designed in the right way you can certainly get more um and you know you still do get in an oyster farm you still get filtration of the water at a high rate you still get denitrification um and taking that nitrogen pollution out of the water you still get um other species living in and around so you know there's more turnover but
Bayden:
[11:58] yeah you really can actually design them to benefit the environment and.
Brent:
[12:02] Then could you help us like walk us through like a mental model of what how they are farmed because i think everyone can understand like what the reef would look like but what are the different strategies for farming and which ones are best at restoring the ocean.
Bayden:
[12:17] Yeah so there's there's multiple different ways that you can farm oysters oysters, um, everything from, um, you know, traditionally sticking posts or, or something like posts in, into the mud and then growing the oysters on those. So that's bent thick farming, you know, you're using the seabed, uh, through to floating rafts and, you know, hanging baskets, hanging lines, those sorts of things.
Bayden:
[12:48] All those options are used around the world, you know, so there's different modes that are used in different places. I mean, locally here in Hong Kong, there's still some farming, which is that benthic farming, but most of it now has sort of gone over to rafts with lines of oysters floating below the rafts.
Bayden:
[13:13] So raft culture you know you do get the filtration you get you know those sorts of you know improving the water quality um but if you really want to maximize the benefits um you know and getting other species in getting the biodiversity and and the fisheries benefits and things like that um and denitrification as well uh benthic farming is much better really yeah so So with benthic farms, there's more places for other animals to live, right? So there's just more structure. So that's the biodiversity side. You get more things living there. Denitrification is interesting because people think that it's the oysters themselves, but they're not. They're filtering the stuff out of the water and then depositing consolidated organic matter into the area on the seabed around them. It's actually the microbial community the microbiome which is associated with the oysters that then processes that waste and does the denitrifying so if you have a raft all of that waste that the you know the stuff that is being filtered out of the water it actually then just falls down onto the seabed and you don't have that same microbial community on the seabed as you do if you've got the oysters there so by having the oysters there you sort of amplify that rate of
Bayden:
[14:33] processing um that'll that that material that organic material and denitrifying it.
Brent:
[14:39] So the microbes won't grow on like the normal floor but it has to grow in between the two oyster shells it has like the organic matter.
Bayden:
[14:46] Yeah so you do again depending on the environment and a bunch of different things you you get largely similar microbial communities you know in just the mud versus the oysters, but you can actually get more denitrifying bacteria that are associated with the oysters. And so it's growing on the shells and in the crevices between the shells and on the mud in between the shells. Yeah. So you do... Um a slightly different community often of the microbial community uh associated with the oysters but the the other the big thing is you're just creating more surface area yeah if you think of a flat you know flat mud flat versus the 3d really complex structure of oyster shells piled up on each other um just that surface area you you know the sheer volume of
Bayden:
[15:44] um microbial activity because of the community is just massively increased.
Keller:
[15:49] Are there differences in the, like when they are farmed versus when it's benthic or the floating, is there a difference in the quality of the oysters that come out of that?
Bayden:
[16:00] Again, it depends on where you are. Um, a lot of, uh, a lot of places around the world, the, I think the quality probably wouldn't vary much, um, but the growth rates will possibly change. And so often you will get better growth rates floating because you've just got more water exchange. Some places, if they're heavily polluted, being close to the seabed actually means that if there's any resuspension of the mud, you're getting resuspension of anything that's in that mud. So you might actually find that there's some toxins or whatever being kicked up. And obviously, if you're an oyster that's sitting right there, you're filtering it. So, yes, there can be a difference. In some places in the world, they have to make sure that their oysters are into tidal when they're farming them. So, they go through a drying cycle every six hours through the tides. And that keeps, you know, things like parasite loads and whatever down. So, it really depends on where you are. But yeah, generally speaking, you know, if there's pollution around, oysters are actually going to be filtering that water. So it's, you know, they're taking it in.
Keller:
[17:21] And then could you explain a little bit more on the filtration process as a whole and like other species that are involved with that and how that's being impacted with pollution, just being able to like plastics, just closing off that ability to do the filtration?
Bayden:
[17:33] Yeah. So, I mean, oysters are really cool. Everyone kind of thinks that they, or has this impression that they just filter water and they just eat everything that comes in, but they're actually really selective in the size particles that they ingest. So they suck water in and they you know they they do filter it but then at the point that they're ingesting it they select for the different size particles and they have each oyster species and at different sizes you know in their lifespan they will actually select for a different size food and they'll ingest food of the right or particles of the right size and then anything Anything that isn't the right size, they actually string together with mucus and it's called pseudopheces and then that kind of just sort of is put out the side of the shell.
Brent:
[18:27] Is that the organic matter?
Bayden:
[18:29] I was just going to say, and that's actually the organic matter that we were just talking about, right? So, they're filtering all this stuff out of the water and then using pseudofeces, which is this mucus string that sticks it together. And then that goes into the spaces in between the oysters. And that's what's then processed through the denitrifying cycle. So, I think part of your question there was microplastics and what's happening. Was that all?
Keller:
[18:58] Yeah, like is there an effect on like just physical plastics, whether it be micro or macro plastics, like inhibiting the ability to do the filtration?
Bayden:
[19:08] Yeah, so I mean... They're going to, I mean, if it's the right size, if microplastics is the right size, they're absolutely ingesting it and they will store it in their bodies. And this is the thing about filter feeders. You know, if they filter something out of the water and it's the right size, it ends up in their bodies, right? But that's it. It's there. And then if you eat them, you eat it. And that's how filtration works. Um they would have to be i mean yeah if if there was a heavy enough load of microplastics then it would affect their filtration rates um but it's more likely that it's going to be more of an effect of if you're eating a lot of plastic then you're not eating your food and so that's actually going to affect your growth rate and sort of all of your energetic balances um so So certainly, if it's the right size, they're ingesting it and it is having an impact on the biology at some stage.
Bayden:
[20:10] But if it's not the right size, then they'll just be sticking it together in that mucus chain and sort of sticking it back out into the mud, which, as we know, it's not then processed. It just stays there. So, yeah, it's one of those insidious – impacts that just keeps hanging around yeah i mean people sorry no just say people underestimate plastics i think we've even even with all of the media that we have on plastics we still um still underestimate how bad it is i think um i teach you know introductory marine biology and one of the things that i point out in that class the basically the first thing i say about plastics is do you realize that other than what's been burnt, all of the plastic we've ever manufactured still exists in the world somewhere? And that's the case. It breaks down into smaller and smaller pieces, but it never actually goes away. And so I think that's something that we really need to remember when we're thinking about it.
Brent:
[21:18] And then do mussels and clams and other filter feeders, do they work in a relatively similar process?
Bayden:
[21:25] Yeah. Yeah, they work in a very similar way. The biology differs slightly among the different taxa, but effectively they do the same thing. The things like muscles are less associated with the mud, for instance. You know, they tend to be more on hard structure because they attach with their bistle threads. So they don't have quite that same attachment to that microbial loop. So, you know, your denitrifying rates are a little bit different. But certainly they filter well. They filter the water. and, you know, also have that structure that you get more biodiversity and things like that. So mussels work in a similar way to oysters. Clams, broadly as a group, tend to be buried more. They tend to be in the soft sediment. So they don't create that structure. So they do the filtration and things like that, but they don't actually kind of have that same biodiversity association.
Brent:
[22:32] And this might be a simple question, of the clams are the ones that make pearls right.
Bayden:
[22:36] No well so technically yeah it depends on what you mean by pearls technically uh a lot of the bivalves um you can make that so the mother of pearl that sort of really shiny inside to the to the shells um and all a pearl is what you think of as the you know the jewelry is layers of of that that nacre right that that mother of pearl and the funny thing about it is that it's actually a reaction to an irritant so you know before we started farming them you know a grain of sand gets stuck in under the mantle under the fleshy mantle and and they all actually you know form that effectively extra bit of shell around it um so that it's not an irritant and we've just capitalized on that so now you know we actually induce that process so that pearls are formed um but the best pearls come from oysters and oh really and there's yeah there's a group of voices that we call the pearl oysters okay um that's not to say they're the only ones that make pearls it's just they make the nicest pearls in the most predictable way and we we farm them for it so yeah.
Brent:
[23:45] We saw uh in halong bay the farming process when we went out there.
Bayden:
[23:50] Oh nice but.
Brent:
[23:51] Yeah i was actually going to ask have we started to see the pearls being formed because of plastics in nature now?
Bayden:
[24:00] Good question. No idea. I really don't know. That's a really interesting question. It's not impossible, and I know that there are people who are working on doing different technologies. So traditionally, you seed pearls with bits of shell from the same species, and so it's not a foreign object per se. The start of a pearl is effectively the same material. But I know that there's a lot of people doing research and using other materials to seed pearls. Um for a lot of different reasons um honestly i don't know about plastic i would have to think about whether biologically it would be irritating or that would force it or whether it's too light material or i don't know yeah and.
Brent:
[24:58] Then uh do you eat filter feeders i.
Bayden:
[25:01] Do eat filter feeders i um i'm actually quite you know clams and different types of clams and mussels i really quite like, but I tend to like the ones that come from more oceanic waters so you know mussels that come from clean water, That's kind of my thing.
Brent:
[25:23] So do you think for people, like, best practices could be, like, eating these farmed filter feeders from, like, cleaner waters because you're not taking the natural ones that are really helping the environment there and you're also a little bit further away from pollution? Would that be, like, ideally the best practice?
Bayden:
[25:42] Yeah. Yes. I mean, eating sustainably farmed filter feeders, you know, from an area that's not polluted is absolutely a good way to go. I mean, in my opinion, obviously, you know, that's my opinion. The really good thing about bivalves as a food source is that they're eating at that low end of the food chain, right? And so the higher you get up the food chain, the more intensive the production becomes as far as energy inputs. And so if you're eating something that is filtering phytoplankton and other material out of the water, then you're eating right at that lower level. So production's faster, energetically it's cheaper. You're not wasting that energy as it goes up the food chain. So it's certainly, from that perspective, quite a sustainable way to eat. And certainly, you know, aquaculture can be done in sustainable ways if you target it well. Yeah, I think it's a good way to go.
Keller:
[26:54] If you had to design your own aquaculture farm, what would be the best way to have the best net benefit to the ecosystem?
Bayden:
[27:01] Oh, gee, that's a big one. Firstly, it wouldn't be single species. And I think that we have to get away from this industrial mindset that you farm the one thing. And that really is an industrial mindset that it's like we'll just maximize production of the thing.
Bayden:
[27:23] And you can really have these complementary farming techniques. So, for instance, there's some relatively recent information that if you're farming seaweed and – so, your target, your high-value crop might be a fish species. And so, you've got your fish species, which is your high-value crop. And then if you have seaweeds close by, they're actually absorbing the nitrogenous waste and effluent from the farm. So you're cleaning up that waste at the same time as producing another edible crop. At the very least, it's good for fertilizer and stuff like that or some other product. But honestly, most seaweeds are really good to eat.
Bayden:
[28:08] And then if you've got a bivalve filter feeder close by as well you're then reducing the particulate waste so they're filtering in those particles and you've got the microbial loop and all that as well but you've also got another crop that you can sell and if you've got the right species of sea cucumber around you can actually use sea cucumbers and you can kind of have them under the pens and they're picking up all that detrital material and eating that as well so where once upon a time you might have had a sea pen with fish in it that you're feeding, now if you look at it you've got that crop but you've also got sea cucumbers um seaweeds and oysters or mussels um and you've got more crop and you're not damaging the environment in the same way so that's that's the way i think we need to think about aquaculture um you know.
Bayden:
[29:03] You can look into it a little more. You get fish species that aggregate around your seaweed farms and stuff like that. There's a whole range of benefits that you can have from that.
Brent:
[29:14] Is anyone doing it that you know of?
Bayden:
[29:16] There are places around the world that are looking at that sort of thing um there's some small trial stuff uh in europe and they've got some really good data coming out and i can't remember the numbers off the top of my head but i think they reduced their nitrogenous waste by i was like 60 and their particulate waste by 40 or something by having um it was a fish farm uh kelp next to it and muscles. And so you are having, you know, a really good impact on, well, maintaining higher sustainability levels by doing that. But to my knowledge, there's nothing at full scale yet. It's all very sort of early stage, but it's promising.
Brent:
[30:00] Yeah. I feel like it's much like the grass-fed cows and just like more sustainable regenerative farming. You're still buying from like local farms, not like industry yet.
Bayden:
[30:10] Yeah.
Keller:
[30:11] And then switching towards the actual oyster reefs themselves, not the farming, what are some of the issues facing that? And I guess to start that, could you give a definition of the recovery debt, kind of where that places the whole situation?
Bayden:
[30:23] Yeah, so recovery debt's a really interesting theory. It's something that was first introduced as a theory a few years ago. And basically, if you think about a damaged ecosystem, whatever's damaging it, so it might be nutrient pollution or it might be harvesting or whatever it happens to be. Once that pressure stops, so you stop the nutrient pollution, that natural ecosystem will start to recover at some rate. And the recovery debt, if you think about all of what you've lost every year, that ecosystem is in a damaged state. The recovery debt is the cumulative total of all of that you're losing every year. And you can measure it in either ecosystem function or ecosystem services. Mostly people think about services on that one.
Brent:
[31:21] Could you expand on that? Yeah.
Bayden:
[31:23] So the difference between functions and services?
Brent:
[31:26] Yeah. What are the numbers that you measure?
Bayden:
[31:29] Yeah. So ecosystem functions are things that ecosystems do naturally, right? It's just the way they function. So some examples are nutrient processing, right? So nitrogen cycling, that's a function. And you can measure that by measuring nitrogen fluxes, for instance, right? So that's a quantifiable thing that you can measure. uh the the important thing and figuring out whether something's a function or a service is a function would happen in the absence of humans it would just it's just the ecosystem doing its thing um services are exclusively about humans an ecosystem service is something that we derive from an ecosystem so just continuing that example the the nutrient cycling um if we We dump semi-treated sewage effluent out into an area. Any of the nutrient processing that's happening by, say, an oyster reef that's there, that is a service to us because we don't have to clean the water up perfectly. We're just dumping some of our waste out there and the oyster reef is doing it for us.
Bayden:
[32:42] So, services only exist with humans in mind. It's effectively a natural function that we're capitalizing on.
Bayden:
[32:52] And putting a value on services is a bit of a tricky thing and and it's always an argument but effectively you quantify the function then put a dollar value on it okay so that's that's how you do it so you can measure these things and if you think about every year that lost lost functional service sort of accumulates, you're getting this big running bill, not in dollar values, but in ecosystem value. What restoration can do is actually reduce that bill by giving a bit of a kickstart to that ecosystem coming back. And so the sooner you start restoration and the better that restoration is, the less debt will be accrued every year. And you can sort of accelerate that system back towards what it was like, the state it was in before it was damaged. So it's a... A theoretical concept which I think really kind of demonstrates how you can have these benefits if you accelerate the pace at which ecosystems recover.
Keller:
[34:07] And what are some of the methodologies that are used for oyster reef restoration itself? How are they trying to fix them?
Bayden:
[34:15] Them so i mean the the core biological way that reefs oyster reefs form is by juvenile or larval oysters settling on the shells of other oysters whether they be dead or alive and then growing in place and then so over generations you get the building of the reef um and you know it's no surprise because it's evolutionarily hardwired that the preferred substrate hard substrate for an oyster to settle on is the shells of the same species of oyster you know very closely behind that is other oysters so oyster larvae prefer to settle on oyster shells and grow there, um so one of the the big things and going back to that sort of example of the lime or harvesting of shells for limes is that you're removing that hard substrate and you're taking away all of that shell and leaving mud or sand. And what you have to do is put that hard substrate back. Oysters need something hard to settle and grow on. And so the best thing you can put back is oyster shell. And so that was sort of the early days of restoration was putting putting oyster shell back and then, um, um, you know, the oysters would settle and grow.
Bayden:
[35:42] The problem is that there's actually a finite amount of oyster shell in the world. And so it's a hard commodity to scale up with. If you're thinking about covering thousands of hectares, and that's the scale we're talking about here. I mean, around Pearl River Delta, Hong Kong, tens of thousands of hectares have been lost. Cost um you know we we've actually done estimates that the habitable area that could have support and we're not saying it covered the entire area but could have supported oyster reefs something like 700 000 hectares right so it's it's a large area you just don't have enough oyster shells to do that and so other hard substrate comes into it and you look at other things and uh yeah we we did Did a big study that looked at restoration over the last 30 or 40 years to try and pull out what might perform best. No surprise, oyster shell and other shells do the best. And then reasonably closely behind that is limestone. And, you know, it's an ancient form of calcium carbonate. You know, it's rock that's effectively been formed from shells. Shells and so that comes in a close second and so you know a lot of the restoration now focuses on.
Bayden:
[37:08] Getting crushed up limestone of various sizes and using that as the base for the reef and then trying to seed a small amount of oysters and oyster shell on top to then sort of accelerate that.
Brent:
[37:20] Growth yeah i think that basically answer where i'm gonna go so they recognize that the calcium carbonate as like the main thing to attach to.
Bayden:
[37:26] Yeah okay yeah so.
Brent:
[37:28] Is there a way of like making it synthetically or do you pretty simply have to find it naturally.
Bayden:
[37:35] Uh there's there's a few groups around the world now starting to do research on that um and, I mean, yeah, you could make it synthetically. What we don't know is, you know, you'd have to have a process which would actually get it to a similar sort of, you know, pH and chemical signature when it starts to sit in the ocean. And I think that's the key thing. The contact with the seawater changes some of this stuff. It's not just a straight line between calcium carbonate and what happens. But, you know, there are groups around the world doing things Things like sort of extending how much shell we've got to use by crushing it up and putting it in a matrix similar to concrete. And so, rather than having a ton of shells covering a small area, you can have a ton of shells covering a really large area by sort of spreading it out. You've still got that chemical queue happening, but it's spread over a larger
Bayden:
[38:36] area to give you more hard substrate.
Brent:
[38:37] So, are they making that like concrete like material to just use as the base for the restoration?
Bayden:
[38:43] There's some early sort of attempts, research going on in that sphere. Yeah, absolutely. There's a reasonably large push around the world to start to make concrete more biologically nice, I suppose, is the flippant way to put it. Because concrete itself is acidic and really nasty. And so there's a recognition that if we're going to develop coastlines, we should actually at least make it something that will not just be a hard structure that nothing likes, but make it a little bit more biologically amenable. So there's a fair bit of research going into that. Yeah.
Keller:
[39:27] And then within the recovery rates, I think one of the papers you sent us showed that over time they tend to decline, even though in the first few years,
Keller:
[39:36] they might be very promising. Could you explain that phenomenon and kind of what those implications are?
Bayden:
[39:41] Yeah. So, I mean, the important thing to recognize here, I think, is that a decline in rate of recovery happening is not a bad thing. It's not like you've done something wrong, and that's just normal ecosystems being assembled.
Bayden:
[40:00] So if you think about an empty space, I'm sure I could bring like a rugby stadium sort of analogy in here somewhere I'll think as I'm talking to try and bring that in you know think of an empty space the first species in right they've just got all the resources all the space and they can come in and it tends to be the fast ones you know so the the short generation time early colonizing species that get in there and you get You get a bunch of species that do that really quickly. So when you put new habitat in when you're doing the restoration, you very rapidly increase in species diversity. So that rate is really, really high.
Bayden:
[40:41] But then somewhere around the two or three year mark, that rate of increase in species starts to decline. So it's not the number of species that's declining, it's the rate at which you're adding new species. And there's a couple of ecological phenomena there. One is that the more species you have, the less there are to add. So rather than adding 10 a month or whatever it happens to be, you're adding one or two a year. So that rate declines. you've still got the diversity and it's still increasing just at a much slower rate the other thing is that then you start to get species turnover and so those early colonizers they tend to be species which are outcompeted by some of the more pinnacle species and the later successional species and so you start to get replacement as well and so that that sort of stabilizes the rate at which your diversity increases.
Bayden:
[41:35] But the really important part is even though the rate of, you know, increase in diversity is decreasing, you're starting to get that ecosystem complexity, right? And it's those networks and complex structures of the reef, that ecosystem which is starting to come in. And that's where you get all those really important functions from. It's that complexity and diversity.
Brent:
[42:05] So diversity growth slows, but the overall net benefit impact continues to get better and better.
Bayden:
[42:12] Absolutely. And at some point you will reach a plateau in everything, but that's just normal ecosystems, right? Once they hit their stable state, they wobble around a bit. That's what they do yeah.
Keller:
[42:25] And then so i think that covers most of the ocean and they're rather that's the whole ocean.
Bayden:
[42:30] And that's a wrap, but i.
Keller:
[42:36] Think we want to talk about one of the other papers you sent us which was about ocean acidification and hypoxia on the psychophysical responses for um some oysters, could you explain kind of what the particular functional changes happening with those are.
Bayden:
[42:53] Yeah it's that was that was really quite an interesting study because we you know you go into that thinking well we know what happens right you you've got these preconceived um ideas and you think well ocean acidification is bad and hypoxia is bad so the the combination is going to be extra bad um but the the changes were much more subtle and we found that um well you know Oysters being really hardy individuals, they're hardy species. They live in these places which tend to be relatively difficult conditions at times. There was a decrease in things like their immune system function. There was a decrease in general metabolic function and things like that.
Bayden:
[43:45] But they actually didn't do too badly. I mean, we expected to have mass mortalities and, you know, declines, but they were surprisingly resilient, actually.
Bayden:
[43:57] But then it was the subtle changes that I think we need to dig into a bit more because, for instance, there was a change in the microbial community associated with the oysters. And this has kind of been a recurring theme throughout our chat, but if you have a change in the functional profile of a microbial community, then you start to diminish things like nutrient cycling and denitrification, things like that. So, if we think about an environment, it's a big estuary that's got some level of pollution happening and then that leads to hypoxia, which the low oxygen as well, then you could have these subtle shifts. We may not see initially big oyster mortalities and declines, and so we think everything's kind of going okay, but if you've got these subtle shifts in microbial communities or immune function, things like that, then you could end up dying. Declined function of the system itself uh but then also you can get to these crash points where you know you they look like they're doing fine but suddenly a disease gets in and then just everything dies so it was it was an interesting um little study in that we kind of got these subtle effects not the big effects that we were expecting.
Keller:
[45:23] Are any of the microbial communities specifically resilient to any of these changes or were they all affected rather poorly.
Bayden:
[45:31] Well Well, the thing about microbial communities is that they turn over really quickly and so you can very rapidly go from one that's quite healthy and resilient to something that is functionally different. And you can have even a lot, you can have the same sorts of species in that community but then just the ratios change. I don't know, with some other work we've done, you know, We got a shift in, and this was actually the microbiome of some crabs. We got under warming and heat wave conditions, we got a shift away from species of bacteria, which are thought of as probiotics, so positive health attributes on the host, towards pathogenic species which cause disease like Vibrio. So there wasn't an overall change in the microbiome, but there was this shift in the relative abundance of these taxa. So you're kind of going away from that healthy probiotic type cycle into pathogens and disease.
Brent:
[46:51] So, yeah, that kind of segues straight into the heat wave conversation we also wanted to talk about.
Bayden:
[46:56] Which actually wasn't intentional, by the way.
Brent:
[46:58] Yeah. But what are some of the other – well, first off, on that one, what was the temperature difference that switched it from probiotic to pathogenic?
Bayden:
[47:08] So, we had – so, that was – so, one of the things that, you know, people talk about, you know, global warming or ocean heating as one thing and marine heat waves as another. Other but the the fact is they're both happening um you know you've got this slow warming and then on top of that every now and again you get these extreme events which is these heat waves, and so that that experiment was specifically um we had two different experimental uh levels of warming and we had um three degrees and five degrees and then on top of that we had so that That was a long-term gradual warming. And then on top of that, we had a six-day heat wave of three degrees on top of those warming scenarios. So, yeah. But I mean, three degrees as a heat wave scenario is actually reasonably moderate. That's not extreme at all. You know, it's not uncommon or you wouldn't be surprised now to see anywhere between sort of five and six degrees in a heat wave. Some of these more extreme ones.
Keller:
[48:12] For both land and ocean?
Bayden:
[48:13] Oh, land, much more. Ocean, ocean, five, six degrees water temperature increase over anything. I mean, now there are heat waves that are going for anything up to a year. So there's actually quite long things happening. Mostly they're reasonably short, a couple of weeks, but you can get months to years now. On land, a terrestrial heat wave, you're talking tens of degrees hotter.
Brent:
[48:42] And then just to under, like, is there a way to describe the sensitivity to marine animals or marine life in general to a heat wave? Because- Well, the crab was one. The three degrees just changed it from probiotic to pathogenic. Corals, can't they switch to bleaching really quickly?
Bayden:
[49:03] Yeah, absolutely. So, I mean, generally speaking, organisms tend to live – they tend to be at their most productive and what we think of as their optimal temperature is actually up towards their upper limits. And it's just because your biological rates, which are determined effectively by chemistry, all of that happens faster if you're warmer. And so, you know, over evolutionary time, organisms tend to lean towards their optimal temperatures being right up towards their maximum temperatures. So that means that you can switch very quickly from being just fine and happy and functioning really well. To being too hot and going through protein degradation and metabolic stress and things just literally falling apart. And that's the case with corals. They've got that symbiotic relationship with dinoflagellates and when the metabolic costs of the dinoflagellates being internal to their tissues becomes too high, they expel them and that's bleaching. And yeah, it can happen within three, four degrees. Like it's not that much.
Keller:
[50:29] Have you found any species that are particularly good at adapting to these heat waves? And like, are there any traits that can be gleaned from that that can be shared, As used in other species?
Bayden:
[50:40] Yeah. So it's really difficult. And there are two things in that, actually. One is how much plasticity an organism has.
Bayden:
[50:54] And plasticity is the ability to sort of change your physiology on those time scales and be able to deal with that stress. And then there's adaptation, which is a multi-generational thing. And that relies on surviving, reproducing, and passing on your superior genes to the next generation. And then that happening over generations.
Bayden:
[51:18] We're just learning that there is also epigenetic effects where if your parents are stressed, that gets them to switch on genes which deal with that stress. And then some genes, once they're switched on, will be passed to the offspring switched on. And so you can actually have this sort of not adaptation, multiple generation adaptation through natural selection, but this sort of epigenetic intergenerational effects that's happening. And so there's several different mechanisms that species can deal with these, you know, extra hot conditions and the stress. And frankly, you know, as a scientific collective, you know, community around the world where we're just, we're really at the early stages on that. But generally speaking, organisms that tend to survive in more stressful environments, they tend to cope or they have the coping mechanisms which mean that they can cope better with these sorts of things. It's the sensitive ones which are really falling apart.
Brent:
[52:29] Didn't you send us an example about sea urchins being able to cope better?
Bayden:
[52:32] Well, so...
Bayden:
[52:35] Again, it's some species can and some species can't. And so I suspect the example I was giving you is we started working, when I first got to Hong Kong, we started working on a couple of different species of sea urchins and some of them are more tropical affinity and so they like the warmer waters and some of them are subtropical, the temperate, so they like sort of the colder waters. And the the temperate species they're pretty resilient up to a point but then you know it just gets too hot um but the tropical species we were really surprised how resilient they are we we kind of went into it thinking well they're tropical in their range they must be you know right near their upper limits and so you'll you know one or two degrees and it's going to push them over the edge and they're all going to die it turns out actually they're remarkably resilient and it started to change the way we're thinking about the theory underlying what might happen because the theory has been until reasonably recently that tropical species are living very close to their upper thermal limits and so any warming will kill them whereas temperate species are you know in colder areas and that's you know nowhere near their upper thermal limits for biology and so they'll actually, you know, they'll have more of that safety margin with warming.
Bayden:
[54:02] It turns out it might not be that way. You know, tropical, some tropical species, I'm not going to say all because obviously we've just talked about corals.
Brent:
[54:10] Right?
Bayden:
[54:10] But, you know, some of these sea urchins, for instance, they seem to do reasonably well, you know, when it gets warm, and they seem to have this plasticity that we're talking about Um, whereas, uh, the temperate species might actually be more susceptible to it. And so, um, we might actually find that the, the colder ends of some of the distributions might actually start to be impacted much before we, or much sooner than we thought they would.
Keller:
[54:45] For scenarios like that, like with the sea urchin or if it was like maybe a seaweed, if they were to be resilient with the benefits of that resilience, go up the food chain as well, or not necessarily.
Bayden:
[54:55] It depends on effectively how functionally important that species is. So there are some species which are, you know, you kind of have what we call functional redundancy. And if one of the species is taken out of the food chain because it gets too hot and their population becomes locally extinct, then there will be another species which fills that gap. And so some you can kind of almost have a one for one replacement. Very loosely speaking, I'm not suggesting by any means that we should kind of, we can get rid of some species and it doesn't matter because, you know, biodiversity does matter in a big way. But there are some species which are functionally very important for a system. And, you know, they tend to, there's an ecological theory called keystone species. And whether you subscribe to it or not, because some people don't, certainly there are some species which are key species. And you can very quickly think of a list which you know as functional groups are important you know so the the habitat forming species so oysters kelps or other seaweeds that form big big habitats corals those sorts of things if you lose kelp from a location that is usually a kelp ecosystem then that system has entirely changed right so they're key if you lose them then that's it.
Bayden:
[56:24] Sea urchins some sea urchins have a really big role in grazing whereas others don't and that's just a biological difference between some species so some species of sea urchin the system itself would keep functioning if they were lost but others um you know like the the big tropical, diadema species they're key to eating the algae which otherwise overgrows the corals and so you lose the diadema then you have these coral reefs starting to look like algal reefs so yeah it kind of long-winded way of saying it depends on the species actually yeah.
Brent:
[56:59] I think that covers a lot of what we wanted to talk about on like your research
Brent:
[57:04] i also want to ask like what is blue carbon because we came across that as well.
Bayden:
[57:09] Yeah so blue carbons uh well a concept that has obviously recently got a lot of attention so basically you know we all know that climate change is being driven by um well mostly by carbon dioxide in the atmosphere so greenhouse gases carbon dioxide methane those sorts of gases um the more we burn fossil fuels the more carbon dioxide there is in the atmosphere the more there is in the ocean the more climate change just accelerates. The focus on how we do something about climate change has two components. One is to start to hopefully rapidly reduce our use of fossil fuels and go towards renewable sources of energy and decarbonizing that energy infrastructure. That's absolutely key. But the other thing is that because the rate at which climate change is going up, or accelerating is much greater than the rate we're going to decarbonize. And so the other thing to do is to actually start to get some of that carbon dioxide out of the atmosphere.
Bayden:
[58:23] And so carbon sequestration is now a focus across all sorts of industries and biomes. Um in terrestrial you know in terrestrial realms uh obviously the planting forest planting trees those sorts of things is is the the big focus so blue carbon is about how you um get carbon sequestered in the ocean right and there are a range of different ways that people are talking about doing that.
Bayden:
[58:59] From a coastal perspective, which is obviously I'm a coastal subtitle marine ecologist, we're thinking about things like seagrasses, mangroves, seaweeds, anything that photosynthesizes and sucks carbon dioxide down and puts that carbon into biomass. And then you have to figure out what to do with it. Because if you've got a seaweed Seaweed, which has a lifespan of two to five years, you know, it's great. It grows really fast. Like the seaweeds draw down carbon or use carbon at rates which far exceeds, you know, terrestrial plants. But they also don't have that really woody kind of, you know, what you think of as the woody parts of trees. And so they're not locking that carbon up. It can be back in the environment within six months to a year to two years. So it's not being sequestered. It's just actually cycling. And so what you need to do is if you're growing seaweeds... For blue carbon you need to then get that biomass somewhere that that carbon's locked up for a long time um yeah so it's you know blue carbon is a catch-all for anything that can sequester carbon,
Bayden:
[1:00:17] out of the atmosphere um and related to the ocean that's.
Keller:
[1:00:20] Very interesting is the cyclical nature part of one of the reasons why there's not a ton of like valuation going into it because like i know like the carbon market is like always pretty complicated.
Bayden:
[1:00:30] But it's.
Keller:
[1:00:31] Easier if you can say okay okay, I'm going to sequester this amount and it'll stay for this amount of years. When it's shorter, is that like an issue that's in the field or not so much?
Bayden:
[1:00:41] Well, I think that, I mean, the reality is, all right, we're heading very solidly into my opinion phase now. The reality is, I think that a lot of that, the carbon valuation and the carbon markets, Like that's a political side of things, right? That's business and politics because if someone had the political will to and the reach in terms of where you could legislate, then you could do it. You could put a price on it and go, that's it, right? But the reality is that carbon dioxide, carbon crosses so many jurisdictions that it's just a complete nightmare. Putting a price on it. And I know the EU is working really hard on this, but then they run into a whole bunch of issues about imports and exports and construction and making goods. It's just a complete nightmare internationally. And if we're being completely honest, I cannot see a point where internationally, the international community agrees on a single carbon market. So there's going to be these regional markets which will have an effect at some point, but But I think we're a little while off that.
Bayden:
[1:02:01] That then means that the valuation of carbon comes back to almost, you know, a voluntary status, right? So it's you pay something when you book a flight, you pay something to the airline who then pays that money to another company to, you know, do something which draws down carbon and sequesters it away. And so that's actually, I think, the stage we're at.
Bayden:
[1:02:29] And that means that the valuation is not at a regulatory level. It's at that sort of service level. So there's a whole bunch of really difficult things that are tied up in that. That but the reality is that you know to some degree and there's a lot of caveats in that but to some degree figuring out how much carbon is captured by say a species of algae and then knowing how much you can lock away, somewhere is not, technically complex, you can do it. And then it's the valuation that becomes very complex. How much is a gram of carbon worth?
Keller:
[1:03:12] Yeah. Yeah.
Brent:
[1:03:13] So, what do you think are maybe some more tangible ways we can give the ocean a chance?
Bayden:
[1:03:19] You know, I think we need to, and this is actually starting, I think we need to start looking at something that's beyond carbon and look at something like nature credits or something which is more holistic. I mean, whether you want to believe it or not, there is still a proportion of the world's population which, for some reason, doesn't think that climate change is linked to carbon dioxide or greenhouse gases. And I can't get my head around that, but there it is. There's also a very large proportion of the world's population which is, in developing nations, they actually don't have easy access to non-carbon sources of energy. So, you know, there's a lot of problems in that. But you can start to look towards these more holistic type interactions.
Bayden:
[1:04:17] And if you think about pricing, for instance, all right, so we've got carbon sequestration happening and we've got increase in nutrient cycling and we've got increase in biodiversity and a bunch of different things all at once, then you can actually more easily capture that. And I think you can actually not sell that, but you can say to people, hey, look, all right, you might not be interested in carbon, but what you are interested in pollution of your local oceans. And you can see that that nutrient pollution is causing these negative effects. Well, actually, let's buy in. Let's actually fix that up. And you can do all of these things at once. And so I think having something which is more holistic is actually more achievable in some ways than saying
Bayden:
[1:05:07] just carbon or just… That makes sense.
Keller:
[1:05:10] Yeah.
Bayden:
[1:05:11] Yeah. And I think there's some positive signs. Again, I mean, the EU is on the forefront. The EU and the UK are on the forefront of this sort of stuff. And I think that there are some very good ways to push that forward. I mean, the reality is that we have to head more towards a sustainable sort of way of doing everything, you know.
Bayden:
[1:05:38] It's human activities and our consumption, which is actually driving all of these negative effects. And so if we can start to do some of them more sustainably, I think that's going to be a really good head start. And lastly, I think that we all need to be a little bit more open. And this, again, is an easy thing to say but difficult thing to achieve. Um you know we have this very um sort of in the box thinking about things like food and and what you like or what you don't like and where it comes from and those sorts of things but the reality is we have to we really have to start eating down the food chain we need to sort of make products from things like phytoplankton and bivalves and you know the stuff at the lower end of the food chain. And if we can do that, we can actually take a lot of the pressure off agriculture and other things which are completely maxed out. So I think there's a lot of things we can do, but we just need to kind of convince the public, convince people that there are these things that we can do.
Keller:
[1:06:52] Wonderful. Thank you.
Bayden:
[1:06:54] My pleasure. Absolutely. It was great.