Danwei Huang
Description: Danwei Huang is an associate professor in the Lee Kong Chian Natural History Museum at the National University of Singapore. His work focuses on the ecology, evolution, and conservation of coral reefs, aiming to uncover insights into their overall health. In this episode, we explore the human-induced factors affecting reefs, including coastal urbanization and reclamation projects, and their complex impact on coral reefs. Despite the challenges posed by rising sea surface temperatures and massive bleaching events, Danwei shares an optimistic view on the resilience of coral reefs. Emphasizing the critical role of collaborative data collection and the power of local initiatives in addressing a global issue, Danwei underscores the importance of community engagement in coral reef conservation.
Websites:
Publications:
Classes Taught:
LSM3252: Evolution and Comparative Genomics
LSM4261: Marine Biology
BL5225: Marine Conservation
Show Notes:
0:00:01 Introduction to Coral Reefs and Interest in the Field
0:04:15 Coral Bleaching and its Widespread Impact
0:07:21 The Resilience and Recovery of Reefs
0:10:13 Bleaching Events Driven by El Nino and Increase in Temperature
0:13:42 Coral Reefs Support One-Third to Half of Ocean's Biodiversity
0:17:11 Different conditions affect the vibrancy of coral reefs
0:20:19 Bleached corals can recover if algae is restored
0:23:56 Anthropogenic impacts reduce coral reproductive output
0:26:30 Witnessing Coral Spawning and Extracting Skeletons for Research
0:30:07 DNA sequencing reveals hidden species in coral ecosystems.
0:33:15 Cryptobiome: Unveiling the hidden species living in reef environments.
0:36:29 Deploying ARMS worldwide for global analysis of biodiversity.
0:39:03 Coral Triangle: A hotspot of marine species diversity.
0:43:30 Solutions for Increasing Coral Resilience and Tolerance
0:49:52 Coral Transplantation and Environmental Adaptation
0:53:18 Interactive Impact of Multiple Stressors on Coral Reefs
0:56:34 Tailoring Solutions for Different Reef Conditions
1:01:34 Getting Involved: Learning and Taking Local Actions
Unedited AI Generated Transcript:
Introduction to Coral Reefs and Interest in the Field
Brent:
[0:01] Welcome Professor Danwei Huang, thank you for joining us today Thanks.
Danwei:
[0:05] Thanks for having me, it's a pleasure to speak to you about what we do in the reefs We'd.
Keller:
[0:11] Love to start off by hearing exactly that, what got you interested in coral reefs and how you ended up at the National University of Singapore.
Danwei:
[0:17] Yeah, that's an interesting question, I guess I've been working on coral reefs for the past 20 years or so I started really, as a recreational diver I learned diving in this region, I learnedit in Malaysia and back then, 20 years ago, the reefs they look pretty healthy and vibrant vibrant colours, lots of species amazing diversity, almost anywhere you go in this region and thenwhen I started working on my first projects in Singapore, I realised there are reefs in this region which have undergone declines to different extents because of anthropogenic impacts.
In particular for Singapore, it's caused mostly by coastal urbanization.
[1:09] We have had several decades of these development projects and also reclamation projects.
So basically the sea is being reclaimed to be land And so that buried, you know, about 60% of Singapore's reefs over the last five decades.
[1:28] And through that, of course, the reclamation also caused an increase in sediment load.
So there'll be a lot more sediment that is floating in the water as well as settling onto the environment, the coral reef environments and other habitats. has.
So this sediment actually reduced the light penetration and that caused all sorts of problems.
For instance, for corals which rely on sunlight to make food, to supply the energy for the entire ecosystem that reduced the amount of energy present and of course has limited the areaswhere reefs can grow.
And so all these impacts hacks sort of showed me that, you know, there's a lot we need to do, you know, to try and understand the biodiversity of reefs, their health before they, you know,they might even be lost to us.
And so I guess that was when I started to work on projects in Singapore and then I did my PhD overseas.
I came back about eight years ago to Singapore and I continued working on trying to to understand biodiversity on coral reefs in particular, but also other marine ecosystems in Singaporeand the region.
Brent:
[2:47] And then when you came back and saw the changes firsthand, was it bleaching?
Was it just different species, just less overall habitat? What were some of those changes that you saw?
Danwei:
[2:57] Yeah, I think there's this long-term impact from coastal urbanization and reclamation.
That has always been there, even before I started.
But I think right after I started, there were at least two major events of coral bleaching.
And coral bleaching is this phenomenon where uh corals because they are symbiotic with a an algae that lives within them that algae you know makes food for the corals and so when youhave increase in sea surface temperatures the corals and the algae are stressed and the balance between them are disrupted so what happens is that the algae is expelled from the coral andwhen that happens the corals turn white right so that's why we call them call it that phenomenon coral bleaching uh and there has been three major coral bleaching events globally there'sthere was one in 1998 which i didn't witness uh there was one in 2010 which which i saw um but you know i wasn't um actively working on on um coral bleaching topics at that point butwhen i came back in 2014 to singapore uh witnessing the the bleaching in 2016 that was uh really quite eye-opening because that you saw how widespread that impact is, right?
Coral Bleaching and its Widespread Impact
[4:15] You would think, you know, if it's like a reclamation, you're covering a reef.
[4:21] And of course you see that impact, but coral bleaching is, you know, reef after reef, you go, regardless of the history of that reef.
[4:30] The current impacts on the reef, the health of the reef, you know, it just, all the corals just turn white, ghostly white.
And that sort of really gave me a perspective on how major this bleaching phenomenon is in that because of just climate change and this increase in sea temperature, you have numerousreefs that are affected, not just the localized impacts that coastal urbanization and reclamation can cause, but really it's just very, very widespread.
And so that really changed how I look at... You know, I think we use the thing that there's some resilience to the reefs.
I think there is still resilience to reefs and reefs can turn around and, you know, they can recover from the beaching.
If they manage to recover that symbiont, you know, algae, within them, they can restart making food and continue to be functional.
But there will be reefs that will be, you know, completely wiped out because of the death of the corals from starvation.
Yeah so that sort of made me think that you know we have to do something about about reefs and to learn more about reefs but through that learning contribute to perhaps conservationand restoration.
Keller:
[5:46] With all three of these major bleachings, were they all caused by increases in sea surface temperature or were there other environmental factors?
Danwei:
[5:53] The increase in sea surface temperature is the major driver, but of course it is affected by other effects as well.
So what we know is that, in fact, Singapore, because the reefs here, because they are under this sediment, right, which there is some protective function of these sediments.
What I mean by that is that it is actually light that is the final nail in the coffin for corals.
In that you have corals that can be stressed because of high temperatures, but it's actually high light that actually causes the symbionts to leave the coral.
And so it's both temperature and light that drives bleaching.
And so in areas where, often in areas where it's quite pristine, you have no anthropogenic impact because of the high light it can also cause bleaching so both light and temperature but inthe case of Singapore I think one of the reasons why it was also badly hit is because of the.
[7:01] History of urbanization and the local impact that it already has so it reduces its resilience against, bleaching and so when you have high temperatures plus highlight, plus localimpacts, those act together to cause bleaching and mortality eventually.
The Resilience and Recovery of Reefs
[7:21] And so there are two sides of it. So there's, of course, the bleaching, but there's also the recovery.
[7:27] And I think what corals here are pretty good at, and that's why they're resilient is because they can recover from it.
So from the 2016 bleaching, we actually saw most of the reef recovering to pre-bleaching levels as of about two years ago.
So we've been monitoring the reefs since 1980s. So we sort of have a good idea of how reefs have responded to impacts and how they have bounced back.
And I think in this case, the 2016 leaching was severe, but actually they have managed to recover, at least in Singapore.
But we know in many parts of the world, a lot of reefs elsewhere, that they may not have recovered fully because it actually caused a change in the way reefs function.
So if you remove the corals, if they die, in some parts of the world, you have algae that takes over, macroalgae, seaweed that takes over.
And so corals can't get back into the system. but in singapore it's kind of unique because our light levels are quite low because of the sediment so the seaweed are also not able to competeout compete the corals and the corals eventually come back so i think there's uh there's this complexity that is quite interesting about reefs yeah in the recent region because.
Brent:
[8:38] When we do some research for this we heard that about 30 percent of the great barrier reef was destroyed in 2016 do you have any idea if like that's recovering like similar tosingapore or is that struggling more because it is like clear waters.
Danwei:
[8:52] Um i i would say clear waters is one of the um reasons why it has not all not all of it has bounced back um i think that um there are also reefs that are quite similar the inshore reefsor the great barry reef are also quite similar in that it has high sediment sedimentation um and And in some reefs, they have a protective effect, so they can recover from the bleaching.
But I wouldn't be able to say if most of that has the same effect.
But in Singapore, it's quite clear that the communities have recovered generally to pre-bleaching levels since 2021 or so.
So we're seeing relatively similar communities now on the reefs compared to pre-bleaching.
And so that's a good thing, but with climate projections telling us that, you know, we might reach annual bleaching, that means every year we are going to have bleaching, you know, inhalf a century or so, that is rather worrying.
Because, you know, from 2016 to 2021, five years, that was the amount of time it takes for reefs to recover.
And so if reefs are going to be bleaching every year, then they're not going to have the opportunity to recover. cover fully from the, those events.
Keller:
[10:09] And when there are like large bleaching events, how quickly do those happen?
Bleaching Events Driven by El Nino and Increase in Temperature
Danwei:
[10:13] So the bleaching events are caused by global and local sort of increases in temperature.
So those three, 1998, 2010, and 2016, were caused by a variety of sort of oceanic or oceanographic events, but primarily El Nino.
And that that cause extreme alnino cause this really high, extreme increases in temperatures and we're actually alnino is returning right end of the year to next year so there are projectionsthat coral reefs will glitch again in this region in, the summer or just before summer of 2024 so yeah mainly is alnino which drives increase in temperature in this part of the world in otherparts of of the world, Central Pacific, for instance, you might have a slightly different trajectory, of temperatures and thus coral conditions.
But in this part of the world, El Nino is a big driver of increases in sea surface temperatures.
Keller:
[11:20] Yeah. And then before we keep going, could you give a little bit of background on just the basic biology of corals?
Danwei:
[11:27] So corals are the foundational species of coral reefs.
And what I mean by that is that, you know, if you go diving in a coral reef, what is on the seafloor that is, you know, these colourful sort of rock-like organisms.
[11:46] These are corals.
And these corals are essentially animals. And, you know, people used to ask, you know, are corals, you know, animal, they rot or are they algae or animal, algae or rot?
And in fact, there are three, all three, because corals are animals themselves, but they host an algae within them, a microalgae, a single cell algae, which helps to make food and to supplyenergy for the corals to grow.
And corals grow by producing calcium carbonate, which is a rock part of the coral.
And this grows to large structures, which becomes reefs.
So multiple species that form these large structures of calcium carbonate or limestone, these are called reefs.
And the reefs, of course, because of the way corals grow, they are different life forms, they are different morphologies, they are branching, they are massive, they are plating species.
Different species coming together form these very complex structures.
And these structures then host lots of other species, right?
You have fish, you have other invertebrates like crabs and snails and other molars.
And this becomes an ecosystem because you have multiple species and they contribute to the functioning and they produce lots of biomass.
And that becomes essentially the coral reef ecosystem, which is very complex because of the underlying coral animal, whose growth is driven by the algae. um.
Brent:
[13:14] They.
Danwei:
[13:15] Are called zooxanthellae um or symbiodynium and that's that's essentially what corals are and and how they drive reef growth and and reef persistence.
Brent:
[13:25] Yeah and then off the top of head do you know like generally like how much biodiversity coral reef supports like within the ocean or just like some general ways for people to thinkabout like they're located all over the world they kind of drive this much do you have any of those in your generally speaking Yeah.
Coral Reefs Support One-Third to Half of Ocean's Biodiversity
Danwei:
[13:42] In terms of biodiversity, so there have been many estimates of trying to understand how many species there are in the marine environment, in the terrestrial environment, and ofcourse in coral reefs specifically.
The more recent estimates place, there are about 2 million species, and we're talking about more of the eukaryotic species, so multicellular eukaryotic species, about 2 million across alloceans.
One million of them live on coral reefs that's the last estimate so about one third to half of all species in living in the oceans are, in coral reefs so that's sort of the estimates that we arelooking at so it's a very large um or a high proportion of all species that live in the oceans and also on earth so it's a it's a it's a very rich environment and that richness is you know you canwitness it right you can you go in there and you can see different colors different sizes different structures and then that's just the amazing thing about coral reef yeah.
Brent:
[14:45] We went diving in tioman oh.
Danwei:
[14:47] Yeah a.
Brent:
[14:48] Couple weeks ago.
Danwei:
[14:48] And uh.
Brent:
[14:49] It was crazy to see just how much was there. Yeah.
Danwei:
[14:53] Yeah, yeah.
Brent:
[14:53] And just curious because we saw sea turtles look to be like feeding on the corals.
Are they eating corals or are they eating like something on them?
Danwei:
[15:01] It's likely to be, you know, it could be a combination of the seaweed that might be growing on the corals if they're dead or sometimes they just like to scrape off small bits of toughalgae and things like that.
Brent:
[15:13] But primarily.
Danwei:
[15:14] Turtles feed on sea grasses but they They often just nibble on other things around.
If there are no seagrass growing on it.
Brent:
[15:23] Yeah. Because did you say that the seagrass would only grow on the dead corals?
Because a lot of the corals over there looked like kind of like covered in a little bit of moss.
And they weren't overly vibrant.
Maybe that's what you can touch on too, is just how vibrant are corals supposed to be?
Because it seems like relatively dull and like more of like the reds, browns, and less so like very vibrant like colors.
Danwei:
[15:48] Yeah, the coral, the colors of corals come from two things.
So they have the host, that means the corals themselves, they have host pigments, but they are also, they of course host the microalgae within them and that's usually green, greenish,brownish.
Um so for corals that you know and there's a range of uh different pigments so if the pigments of the corals themselves are more greenish and brownish of course that will show up but ifthe algae themselves have you know if the colors of the algae dominate then it'll be greenish and brownish um but it'll be important to distinguish between living corals and the dead coralsthe living corals they can be green but they can also be in different colors but But corals that are dead, they almost would be usually covered by algae.
So these are macroalgae or turf algae that can be greenish or brownish if they are bigger.
And those will cover the corals when they are dead.
Because often when corals are alive, they actually would prevent the algae or the seaweed from settling on the corals or growing on the corals.
So what you're seeing if let's say the corals if it's like a fuzzy kind of surface, likely the corals those corals that you're looking at have died and are colonized by turf algae.
Brent:
[17:06] Yeah because I would say a lot of the corals out there that we saw were like that yeah.
Different conditions affect the vibrancy of coral reefs
Danwei:
[17:11] So it depends on the site so I like Kioman a lot and I did some of my diving courses there, but again there's a diversity of health conditions conditions on in tioman so if you go ifyou are just on the house reef for instance or near to the resorts nearer to the coast the the environment tends to be a bit more nutrient rich and so the favors algae growth right so then youhave um the algae is competing with the live corals and so maybe that it's not as colorful but if you go offshore a bit you know some of the other outer the water islands near the Tioman,they can be more colorful and they have less sediment, they have less nutrients.
Different environmental conditions you know drive the how the how the reefs look you know as well generally because.
Brent:
[18:02] For what i would estimate like the ones closest to like the shore were probably a little bit more vibrant more active and then as you like got a little bit deeper like away from theisland a little bit more offshore it that's where you kind of started to see more of the moss and like the dead.
Danwei:
[18:16] Okay so so i think if if it's deeper it's probably um just corals not being able to thrive in in that kind of depth with the perhaps there's a lot of sediment uh and the sediment isoccluding the light and so some algae would you know those micro uh those not micro but those tough algae that's growing uh they they can dominate this ecosystem um yeah so so itkind of depends on where you are and the local conditions yeah.
Keller:
[18:43] And for the dead corals how does it work in in terms of regrowth like if you have a live coral and a dead coral adjacent to each other can the live coral spread on to the dead coralshost or is that area like not viable for growth after the fact.
Danwei:
[18:58] Yeah so so let's say you have a living coral and uh and then around it you basically have dead corals the dead corals will remain dead but what will have might happen is that youcan have the living coral growing sideways and then colonizing or taking over that dead coral space, assuming it's able to grow faster than the seaweed that's coming in as well.
Or you can have new recruitment.
So you have actually coral larvae that's spawned in the waters or they reproduce from adult colonies somewhere else.
They come to a certain spot, maybe it could be a dead coral area, and then it settles and then grows up to a new colony.
So that space it just becomes space so a dead coral will not just be revived but you you, Especially if the whole coral colony is dead. You may have a colony that is mostly dead.
There's maybe a small area of it that's still alive, that's still live animals.
And that live animal can spread to cover that space.
But if not, then it's new growth from juvenile, from larvae that's settling onto the corals and then forming a new colony on its own.
Brent:
[20:16] But bleached corals aren't dead corals.
Bleached corals can recover if algae is restored
Danwei:
[20:19] That's a good comment. I think there is this time frame where corals bleach and then they are white and they are not dead yet.
And so they just have their algae expelled. So they can, if they were to recover, for that colony to recover, it has to recruit that algae back into their cells.
And if they happen to do that, be able to do that, especially when the temperatures go down to normal, they can still continue to live with, you know, so be the same colony but maybe newnew algae new new symbiodinium so so there's there are you know there's a time frame where actually corals can still recover but if they don't, and they die because of starvation becausewhen they bleach you don't have the algae with them so they you can still that space can still be colonized by corals but it would be the next generation of corals.
Brent:
[21:13] In that sense and then are corals are the male and female corals are they the same And is it all within one animal? How does that work?
Danwei:
[21:21] So there are different species have different reproductive strategies.
So you've heard of coral spawning, I suppose. So coral spawning is this phenomena where once or twice a year, majority of coral species spawn by releasing their eggs and their sperminto the water.
And then external fertilization takes place so the egg and sperm will meet or from a different colony will meet.
That happens once or twice a year. So if a coral produces both egg and sperm, they are both male and female, then they are hermaphrodites.
They are both male and female.
But there are some species where the males and the females are different colonies.
So there are different strategies, right? So different species use different strategies to reproduce.
But I think majority of species are hermaphrodites, meaning that there are males and the females males are together in one single colony and they release both egg and sperm.
Brent:
[22:21] And the fertilization happens in the water and then that larva will settle and recolonize if it meets like an area it can live?
Danwei:
[22:28] That's right.
Brent:
[22:29] Yeah. Okay.
Danwei:
[22:29] That's right. So the reproduction for most species is external.
So they release the eggs and sperm and, you know, but millions of them, right?
So in the hopes that they will meet another colony with the eggs and sperm and the eggs will meet the sperm.
Of the other one and then they become larvae and then they settle.
Brent:
[22:46] Have you had or seen any data showing like how far some larvae could travel?
Danwei:
[22:52] I think there are, so there's both the movement of the gametes, the eggs and the sperm, but there's also movement of larvae and larvae can move hundreds to thousands of kilometersbefore they settle because there's this period of time, we call it pelagic larval duration where they are actually swimming.
So you know corals adult corals just stay there they don't move but actually the for many marine invertebrates including corals their larvae swims around all right and they can swim tovarious degrees so some swim a lot faster some swim slower but also they spend different amounts of time as larvae so the longer they spend as larvae the presumably the further they cantravel And so there are coral larvae that can survive or be in larval stage for weeks.
And because there are weeks in the swimming phase, they can reach hundreds to even thousands of kilometers away.
But of course, the further away it is, the less likely you have surviving larvae.
Anthropogenic impacts reduce coral reproductive output
[23:56] But all that is a game of numbers in a sense. So the more larvae you produce, the more gametes and the more eggs and sperm you produce, the more larvae you produce.
And so the reproductive output of corals is also an active area of research.
And we know also that anthropogenic impacts, climate change and a lot of coastal impacts have reduced the reproductive output of corals.
And so that has adverse effects also.
Brent:
[24:30] You've said a certain word a couple of times now, anthropogenic, could you define that?
Danwei:
[24:34] So anthropogenic means anthropo, which is an impact that's caused by humans.
So anthropo will be humans, and so anthropogenic is impacts generated or caused by humans.
So that's why we use the term anthropogenic impacts, which includes climate change, obviously.
Brent:
[24:55] And.
Keller:
[24:56] Then with the reproductive event that happens only once or twice a year, I guess two questions of that is like, one, do you or do researchers know when those events are?
And then with that, how do they study fertilization rate if it's such a broad scale?
Danwei:
[25:11] So locally at every reef, there will be localized timings of reproduction.
We know that the majority of species spawn eggs and sperm generally in April, and sometimes there's a second time in the second half of the year.
But that's for certain reefs, there are other reefs where they spawn in different months, but generally it's once or twice a year.
And that really was, you know, the discovery was actually quite recent.
The discovery was known only since the 1980s when some Australian, you know, scientists, they witnessed this corresponding.
And usually it's after dusk, so when it's starting to get dark.
So not many people are in the water witnessing this thing. So when they made this discovery, it was like, oh, okay, we've been missing this phenomenon for decades, right? Right.
And so since then, people have started to go out there to, to, you know, to record when corals, you know, spawn and reproduce.
And so now we have a pretty good map and like a calendar of when different species spawn and at different localities when they spawn.
Right. So it can be the same species, but you know, in different ways they spawn at different times.
Keller:
[26:30] And.
Witnessing Coral Spawning and Extracting Skeletons for Research
Brent:
[26:30] That's something you can see, right? Yeah.
Danwei:
[26:32] So you can see in two ways. One is, you can see it going off right when they spawn. And that happens over an hour or two.
So it's like on a reef, you can have several species going off at the same time over one or two hours or sometimes throughout the night.
Or you can, if you don't witness it during that night or that evening, a few days before or up to even a few weeks before, if you actually, for researchers, what they do is they will extract abit of the skeleton skeleton of the coral and then they will see eggs inside the coral when you see the pink eggs that are developing uh ready to go that's when you know it's going to spawnsoon so you can so when.
Brent:
[27:14] The spawning occurs it's like pink plumes of smoke.
Danwei:
[27:17] That's eggs yeah exactly so so the eggs uh often for for species that are hermaphroditic they that means they have both male and female they reproduce with, egg and then the spermis around it so it's like an egg bundle then when it reaches either before it reaches the surface or reaches the surface you'll break apart because the sperm will actually have to fertilizeanother egg somewhere right and so they'll break apart and so now i have eggs and sperms floating around looking for what kind of looking for you know another egg and another spermso it's quite quite an interesting phenomenon in itself yeah and and a beautiful phenomenon as well for is for a lot of photographers they like to go up you know to the reefs during thespawning time because it's like this massive rain that's upside down you know going up all the eggs floating out it's quite cool.
Brent:
[28:03] Definitely sounds like it.
Keller:
[28:05] What does that like coordinated spawning tell us about the communication between coral reefs.
Danwei:
[28:09] Yeah it's again also an active area research so it's how what are the cues that they use and I think there have been a lot of, tests or some studies to show you know there's acombination of moon phases you know which cause the waters to be in a certain condition, right?
So when the water is pretty still, that's when it's a good time to spawn because then the eggs and sperm are not swept away immediately, whereas they're in this contained environment.
So I think moon, the moon phases, the lunar phases is one big driver.
So corals have adapted over a long time to be able to perceive either through the light of the moon or somehow, wind speeds or even the tide levels.
You know, all these contribute, all these are driven by the moons, right, the moon phases.
So, all these might contribute but I think we don't actually have a full picture of what's going on.
What are the main drivers of, you know, what are they perceiving that they need to spawn, right?
Keller:
[29:21] So.
Danwei:
[29:21] I think that's a really interesting question that a lot of scientists these are working on and then.
Brent:
[29:27] Based on the conversations so far do you think there's anything that we're missing to understand about coral reefs or that you want the listener to know like just to get a goodholistic understanding of what they are.
Danwei:
[29:38] Yeah i i think generally um you know we going back to the question you asked about how many species there are on coral reefs uh it is still an open question so i think we we weonly know going by what we have have recorded, but actually, if you look at what's hidden on the reef structure is, you know, there are lots of species that we are, we are not, we have notactually seen and.
DNA sequencing reveals hidden species in coral ecosystems.
[30:07] And the reason is because you have corals that are of different life forms.
They grow to different shapes and hidden within those lots of species, which are rarely collected, like rarely seen.
So more recent work have tried to use genetic information.
So using DNA technologies to sequence what's in the water in the hopes of understanding what other species that are there. So we know that all organisms shed DNA into the water.
So like us, we shed DNA into the air, right? So if you two leave the room now, I can filter the air out and then I can actually sequence your DNA and your genome can be sequenced justfrom the DNA.
So it's pretty amazing the amount of information that DNA can provide us with.
And the same goes for the marine environment. So the organisms shed DNA.
So what scientists have been doing is to, you know collect that water filter it and that DNA can be sequenced and then what they have found is the large majority of that DNA that is in theenvironment come from organisms that we have totally no idea about you know they have been never been described never been discovered but the DNA signature is there right so there'snew lineages and so on and of course there's one way to do it we call that environmental DNA so sort of concentrating that that DNA that's from the environment.
[31:36] But you could also, you know, use some standardized sampling devices where you put out some kind of a trap, right? So organisms go in.
So it could be fish traps, but for the large proportion of species, they tend to be small.
What we have done is we have deployed these reef monitoring structures, autonomous reef monitoring structures or ARMS.
They are made out of plates, several plates, because those plates are stacked.
[32:04] On each other and you have a tiny space in between those plates and then what happens then is you have all these tiny organisms that are used to being, you know embedded in thematrices of the reef on the structure a structurally complex environment of the reef they go hide in these plates and then what we do is after one or two years we go extract that thosestructures and then we sequence or we just recover what's on the plates and we sequence everything reading this on the structure.
And again, we have found that about 50% to 75%, organisms that are recruited all the way from macro fauna to bacteria those have not been you know there's no you know there's no,previous understanding of what they were right these are new sequences, new records of organisms that have never been seen right living on the you know if we just went out therecollecting these are just you know probably a lot of them are new species yeah and.
Brent:
[33:12] This is describing your work with the cryptobiome.
Cryptobiome: Unveiling the hidden species living in reef environments.
Danwei:
[33:15] Yeah so essentially cryptobiome is are the species that are living on any um environment but they are generally hidden from from observation uh and on the reef of course they hidein the crevices and in within the matrices of the of the corals and of the reef and so the only way to get them out is to remove the reef but of course that will destroy the reef so what we dois we deploy those autonomous reef monitoring structures the arms to characterize them much better.
Brent:
[33:45] And then are you storing all this data like are you like open sourcing it so other people can look at it or are you like partnering with other institutions because is there an ultimategoal here saying like we are discovering like half of these new things we're discovering or like could they unlock potential answers for like helping save the corals.
Danwei:
[34:03] Yeah certainly so i think uh all the data that that we get from these arms so we have deployed a dozen of these over the last three or four years.
The data is all put in an open source database.
So we call this the GenBank, right? And that's hosted in the United States.
And basically, these are sequences that anyone can download and to figure out, you know, maybe another researcher from elsewhere would like to compare, you know, know what speciesthey have there versus what they have in singapore then they can match you know what's the degree of overlap between the fauna here and there so all the data is open source open accessand you just have to download them and and do some analysis to understand how widespread these species are do you get the same species here versus somewhere else yeah so that'sthat's sort of the goal of this and and what one good thing about this program This is the Global Arms Program.
And so when we deploy them, they are standardized across all of the...
You basically purchase them for a small price and they are standardized in terms of size, in terms of how they look like.
[35:21] And so everyone, every group that does this will have... The data that comes out will be, in a way...
Quite comparable across different areas and also across different time points so apart from just understanding what's there in different parts of the world this program has also allowed usto set up a monitoring program so you know rather than having to go into the water and survey small little things you know visually inspect or visually examine small organisms what wedo is you deploy this over time and then we extract them at different times so then we had we actually have a time series of of these diversity that is you know uh that can be changed overtime because of of you know human impacts anthropogenic impacts uh and so we can track you know what's the diversity change over time with these structures so that's sort of the uh thebeauty of this program is is that it allows us to compare over space and over time in the same time yeah at the same.
Deploying ARMS worldwide for global analysis of biodiversity.
Keller:
[36:29] Place yeah you guys put in 12 how many do you know how many have been put in globally oh.
Danwei:
[36:34] I think um definitely hundreds if not thousands um i i don't have the numbers but they have been deployed in many parts of the world hawaii indonesia um many parts of southeastasia um and uh there has been many groups working on it i think there's now uh you know a global collaboration that's ongoing to try to put all that data together to do a global analysisum and so that's that's sort of the benefit of this kind of projects where you're using the same device by doing it in different places different lengths of time of deployment and that gives usa good uh understanding of both diversity but also you know how that diversity change or changes over time yeah so So that's one of the exciting things about this project.
Keller:
[37:21] Have you guys been able to draw any conclusive insights from the data yet?
Danwei:
[37:25] So at least locally, we know actually that what's clear is that the biodiversity of a site, so if it's generally healthy and has good coral diversity, it will also increase the amount ofdiversity of these small little critters, fauna.
That's growing on those arms.
[37:51] So there is a general positive correlation between local biodiversity and the diversity of this fauna that's growing in these areas.
So it's actually a good monitoring tool because it gives us a good sense of whether the waters are clean enough, whether they are healthy enough to support those species that are growingin corals and so on.
But at the global level, I think it's not as clear.
It seems to suggest that there are, so we know that this Southeast Asia is a biodiversity hotspot, but there are actually other, there are actually arms that have been deployed elsewhere thatshows that they equally have quite high diversity. diversity.
So I think the interesting questions about where do we have a highest biodiversity is, you know, we are getting some interesting findings from this that suggest maybe it's not justSoutheast Asia or the coral triangle, but, you know, other areas which can be rich in different groups of organisms.
Brent:
[39:01] Where's the coral triangle? The.
Coral Triangle: A hotspot of marine species diversity.
Danwei:
[39:03] Coral triangle is this area of maximum diversity.
We're usually referring to marine species and that goes from Philippines to southwest to Indonesia and then all the way to Solomon Islands on the east.
So that triangle, physically a triangle, denotes this area of maximum diversity.
Brent:
[39:26] And that doesn't include the Great Barrier Reef. That's too far south, right?
Danwei:
[39:28] Yeah, that's generally quite south. But this is the area where we start off to be the where you have highest diversity of corals fish and other invertebrates but this triangle have shiftedin its configuration you know it used to be more of a, It's not a literal triangle.
Brent:
[39:50] Right?
Danwei:
[39:50] It's more of, you know, this area resembles a triangle and areas around, even Singapore is not really inside a core triangle.
West Malaysia is also not really part of the triangle, but it has a lot of diversity.
So a lot of peripheral areas are also considered to be in this part of core triangle.
And it's more of a management tool and policy tool that it allows countries that are within this area to use it as a way to generate more resources or, you know, for conservation.
So it is a good way to, you know, tell people, you know, we are part of the coral triangle, we have a lot of biodiversity and we need resources to conserve that biodiversity.
Keller:
[40:35] And another part of your research that we saw was your work on temperature tolerance.
Could you explain a little bit about that and kind of tying back to what we started off with about global temperature rises as being one of the leading causes for bleaching events?
Danwei:
[40:48] Yeah, again, I know our lab's work is focused on the diversity of organisms.
And when we are looking at the impacts of heat and our thermal stress on reefs, we are actually looking at how that impact or how that thermal stress impacts diversity.
And so we have been looking at... So the symbionts that live in corals, that make food for the corals, it's not just one species.
There are actually hundreds or even thousands of species that are, you know, at one time, each colony of corals can host hundreds of them in a single colony.
And so what we are trying to understand is what happens.
We know that during bleaching, those algae are expelled.
[41:39] So what is being recruited back now? What are the dynamics of what is leaving the coral and what's coming back to the corals?
So generally what we have found is that during a bleaching event, it reduces the diversity of the symbionts that are present inside.
So we think that certain certain more tolerant species of that algae are able to stay inside the coral.
Even though most of it is gone, most of the algae is gone, some of that is retained.
And when it's recovered, it recovers the lower diversity of those symbionts.
So the diversity of symbionts are actually affected from the bleaching.
And we also look at microbial communities. So looking at the bacteria that is residing in and around the coral.
And we have been able to find some disease factors, so some pathogen-like sequences that are showing up in our data.
[42:42] Showing that during bleaching you can have some potential diseases that can come in because either they thrive in higher temperatures or that the corals have lower resilienceagainst diseases And that changes the communities of bacteria that are around the coral.
So those are the findings that we've been getting from the work that we're doing in terms of bleaching.
And overall what we you know I think the the general finding that bleaching reduces diversity not just in corals but also in the symbionts in the microbial microbial communities isprobably quite a general one and you, take away from some of these studies.
Solutions for Increasing Coral Resilience and Tolerance
Brent:
[43:30] So when we're looking at solutions to these problems would it for two parts first like how exactly does the coral kick out the algae and i asked that because when we look forsolutions are we looking at trying to create more resilient coral or more resilient algae yeah.
Danwei:
[43:51] Um i think that the i would say the short answer is both um because there's is host factors that will increase resilience, meaning the host is adapted over generations to be able totolerate thermal stress, but there are algae that are also adapted over generations to be tolerant against thermal stress.
So at the community level, what we have seen is that in certain reefs where they have bleached previously, they tend to be a bit more resilient in future bleaching events.
Not all, but at least some of those that are being studied. So we think that it's both the host and the algae that actually confers that resilience.
So there are groups out there, a lot of researchers that work on symbionts that are actually trying to select for symbionts that are more tolerant and then to put them in, you know, in thetanks with the corals so that the corals will take them out.
But there are also groups where they have done some experiments showing that if you.
[45:02] Thermally stress the coral but you don't kill them so you sort of give them small stresses you increase the temperature by a bit over time, that actually increases the tolerance of thecoral just within a single generation but of course you can also select over generations select for for larvae that comes from more tolerant hosts.
And then that over generation will increase the tolerance of the entire population.
So a lot of those studies are being done right now across by different groups.
So I think what's nice is that, you know, you have not just one solution that we're targeting, but we are, you know, the entire coral reef community is actually looking at different solutions,right?
And we are targeting different parts of that coral holobion.
That's called a coral biome because it's the entire coral as an ecosystem.
You have the host, you also have the symbionts, and also some groups are working on the microbial communities because the microbes also confer some resilience or tolerance againstheat stress.
So there are also microbiologists that are involved and they are also looking at what are the kinds of bacterial communities that will increase the host tolerance to bleaching.
So you might take those communities and then you put them together with the corals in the hopes that they will take up those microbes and then they become more tolerant.
[46:29] Heat stress so yeah lots of different interesting potential solutions um i think.
[46:37] Preliminarily there are some quite positive results coming from that i think one of the biggest questions everyone have been asking is how do we scale this up because you can dothis in the lab you can do this in your tanks um but being able to do this at the reef level that is is again, an open question, also active area research.
So ultimately before we can get there, I think we still need to figure out how to reduce emissions and reduce the impacts of climate change at a global level.
We cannot just rely on these solutions that are just really just currently very expensive and also just emerging.
So we have to attack this problem from many different scales, many different ways and through collaboration across.
Brent:
[47:26] The globe. It.
Keller:
[47:27] Sounds like, so the lab-grown corals or the lab-altered corals, are they generally accepted back into the reef environment?
Danwei:
[47:35] Yeah. So when we test those corals, we tend to take from the local populations and then we put them back where we find them.
Or we put them in the same, more or less the same environment, but maybe in areas where maybe it's a bit more degraded. So we need more of those corals there.
But we typically haven't discussed or thought about perhaps transplanting corals across national boundaries because that will require a broader discussion about what can we do.
There has been, you know, 10 years ago, people were discussing, you know, assisted migration of organisms, right? right?
And corals were one of these possibilities where you can transplant corals from maybe more heat stress environments to areas where it's less warm.
And so they get better. So that conversation is again restarting because now that we have these technologies to boost resilience in corals, the question is can we put those corals back or putthose corals in other areas where they might.
[48:46] Actually help to restore local populations so that again is still a conversation that people are having is it's just a lot of ethical questions as well as you know the the the question ofwhether you have uh you have to conserve genetic diversity if you only have a certain types of corals that you are putting out in the environment are you reducing the diversity in terms ofthe the genetic makeup of those um of those species that might cause problems down the line so if if you have another type of stress maybe not thermal stress.
[49:19] Ocean acidification would they you know cause more problems because now you only have a limited set of uh genetic diversity on in those restock corals so those are questions thatyou know scientists are still asking and still trying to grapple with.
Brent:
[49:34] But for the most part when you place a coral in a certain area it'll tend to grow from that spot because i know earlier we talked about the way the sexual reproduction occurs it getsreleased it grows it can float wherever but for for the most part, it will still like pick up in that one location?
Coral Transplantation and Environmental Adaptation
Danwei:
[49:52] If it's suited for the environment. So typically, if you, if they are locally adapted to the environment and you have no other stresses, it will thrive.
So you, you know, you grow out some, you pick up a coral fragment, you grow it up in a tank, you put it back in the same place it typically would.
As long as it's attached properly to the substrate, to the reef, it will typically grow, grow fine.
Um so the question is could will you be able to transplant that coral to elsewhere and i think there's some experience that we have in singapore where we have done a lot of restorationprojects, transplanting corals from one place to another um the success rate is pretty high um but again singapore is very small so you think about um the environmental conditions are notvery different between between sites so i think we we have that benefit and and so we can potentially take one one coral from one area, we grow it up in a tank where they have, once theyare healthy and they are in a better shape, we can put them back in another reef and they should survive quite well.
Brent:
[50:57] That's great.
Keller:
[50:59] And earlier you were talking about, you know, we need to reduce our emissions and that'll help corals.
Are there other threats that we know the weight to?
In a sense, like, we know that sea temperature rise is a big problem.
Do we know that pollution causes, like, a certain amount? Or do we know that... The certification.
Brent:
[51:16] Yeah.
Keller:
[51:17] Acidification. Do we have an idea? Do we have any mapping with that?
Danwei:
[51:20] Yeah, we know a lot less about ocean acidification in terms of the responses of species, right?
And while for corals, we know...
Quickly quite we knew quite quickly that you know if you increase in temperature it drives the symbionts out of the coral um for acidification there seem to be differences in termtolerances of different species um within between coral species but also with other um shell uh calcium carbonate making organisms right so yeah molars we have shells that can dissolveuh you have um you know, organisms that rely on having generally a non-acidic environment.
But overall, the change in the, or the decrease in pH that we're seeing.
[52:12] Actually, some of those values have already been, you know, you have recorded those values in some areas.
So in naturally quite acidic waters, there still are corals growing.
And so there's a bit of, you know, different areas or localities having different tolerances plus different species also have different tolerances.
And so I think the effects are a lot less clear for ocean acidification.
But also, as you know, I was mentioning that in Singapore, we have had decades of coastal urbanization and that's not seen in many other pristine reefs or more pristine reefs.
So that in itself is already you know one threat that has been ongoing and he has not declined that threat has not declined now we have ocean acidification, thermal stress or bleaching allcoming together.
[53:12] And so I think the worry is more of the interactive impact between them rather
Interactive Impact of Multiple Stressors on Coral Reefs
[53:18] than individual impacts.
Because now we know quite clearly that there are some tolerances against thermal stress.
There are some tolerances against ocean acidification.
And also corals have survived the increase in sediment in our waters for a long time.
But what happens if all three or all these multiple impacts come together in the next century or so?
And that's what we don't really know. Like what are the impacts, combined or integrative impacts of all these happening together.
[53:52] So we have done some work to look at, you know, what is the impact of sediment plus heat?
What is the impact of sediment plus acidification?
But if you, you know, designing experiments that try to put all these together and, you know, they have to be controlled in certain ways is a scientific challenge, right?
You need to have multiple different treatments to try and mimic that multiple stress.
And so what we have found at least for temperature and heat stress, sorry, heat stress and sediment stress is that heat stress actually drives a lot of the physiological changes.
Whereas sediment, they have already sort of adapted to that sedimentary environment.
So I think overall, it's still the heat stress that is actually stressing the, you know, is causing a lot of the mortality and reaching mortality, of course.
So, yeah, thermal stress appears to be the biggest threat so far, I think, compared even to the local stresses that we are seeing.
Brent:
[55:02] And then how would you say, do you think the global community researchers are doing a good job collaborating and talking amongst each other to kind of compare all thesedifferent threats and come up with some solutions?
And then are there any solutions that you're aware of that are succeeding right now?
Danwei:
[55:17] Yeah, I think the Coral Reef research community is generally quite, you know, collaborative. You go to conferences and everyone's really happy to work with one another, providedata, provide corals even, provide material.
I don't see a problem with that. I think generally we all want to work together.
I think the challenge is in the complexity of the coral reef system.
In that we have reefs that have different histories and they are spread over different areas. and they all, not all, but many of them respond very differently.
And so, a solution that's well tailored for Singapore waters, it may not work for, you know, somewhere in Hawaii, right?
Because, you know, we have a lot of sediment, we, you know, Singapore waters have a lot of sediment, there are very specific ways in which we help corals.
So, for instance, in Singapore, we know that if we get, if we are able to increase the, the, thermal tolerance of the corals. I think the corals will do quite well.
But in other areas, you have to deal with light, increase in light, you have to deal with changes in the local.
Tailoring Solutions for Different Reef Conditions
[56:34] Oceanographic conditions and of course increase in the urbanization impacts in some areas.
So we are all at different stages of impact and the nature of the impacts are different and so i think that's one of the challenges so even though we work together that the the solutions umthat we can come up with even though they're general they may not apply to every single reef and so um it is a continuing discussion we have to tailor you know the solutions to twodifferent areas so in singapore for instance i think um we are we are working with increasing the host tolerance so we we are sort of doing sub-lethal stress on the corals so that we buildtheir resistance up and then we are also looking at microbial, microbial communities that are better at surviving or conferring some resistance to bleaching to the corals and we are usingthat as well so that's for us but then for other places they might be doing different things and but we of course we share notes and some of the processes that we do or the experiments thatwe do will be very similar maybe the conditions that we subject corals those two will be slightly, But yeah, we, of course we, we have to work together.
Keller:
[57:55] And then as we start to wrap up here, why should people care about coral reefs, especially people that live inland that are never going to go see them?
What impact did they have on humanity?
And then along with that, if we were to stop intervention now and continue to degrade our reefs at the rate we're going, what would that look like in the next 10 years, 20 years?
Danwei:
[58:15] Yeah, it's, you know, I, I think it's, it's clear.
Hundreds of millions of people rely on reefs not necessarily directly so not every one of these millions of people harbors from reefs um but ultimately they may be either living close tothe coast coastline or they may be uh even in a city relying on you know food fish right from on reefs and so on um i think we just i mean most of us just don't have that um uh sort of thatthe link back to the oceans anymore and i and and that's unfortunate but i think ultimately we need to still um you know tell people that you know a lot of people are reliant uh and it'ssizable enough that if these people are deprived of their protein of their livelihood because the reefs are gone um that can cause a lot of you know could be geopolitical could beeconomical uh problems um and and that ultimately can will affect us right so so even though we are not directly reliant i mean i don't eat a lot of reef fish or anything we we areultimately affected by the the um you know the the societal changes that can happen if reefs are gone you know tomorrow um i think.
[59:39] What we as a scientist we we you know we have seen reefs change right i've seen new change for 20 years over 20 years but we have seen them recover as well if you look at thegeological record reefs have survived for thousands of years our modern reefs were built over the last seven eight thousand years corals have been around for millions of years right up to400 million So I don't think we need to worry that species will go extinct. There'll be some species that go extinct.
And so I think the narrative that we should be thinking about is that actually we are more reliant on reefs than reefs need us.
[1:00:21] To conserve them. Ultimately, you know, we are not going to be producing enough food even if you are good at growing lab-grown meat and so on.
We still will have to rely on part of our protein source on reefs and other marine environments.
So I think it's really important to have that perspective that perhaps also it's not just us but also communities that living closer to the coast they are directly, relying on the reefs and if theydon't get their protein, they don't get their livelihood you know we need to you know think about what are the impacts that will be for us down the line you know so yeah i i think i thinkwe all need to it's our responsibility to sort of understand it well because um the impacts can be upon us very quickly and impacts may not be direct not that we'll be starving but actuallymight be other issues that that can cause us to to lower our, to have a lower standard of living and things like that, even if you're just living in the city.
Brent:
[1:01:23] Certainly. And then do you have any final words of advice for students or people listening with how to get involved, easy actions you can take, where you can learn more,anything like that?
Getting Involved: Learning and Taking Local Actions
Danwei:
[1:01:34] Yeah, there are plenty of resources online. I think, you know, just to learn about what reefs are and, you know, what you can do locally.
Obviously at the global level, we all, it's really, in a way it's simple, but in a way it's a mammoth task that we need to reduce emissions.
That is really the number one solution, right?
And because that will reduce the impacts of bleaching or thermal stress on corals.
But locally, again, our research has shown that local impacts can magnify these global impacts.
So if we can can minimize pollution that's going into the waters, into our waterways, which eventually lead to reefs.
I think that would be important to educate ourselves on all these different impacts and the fact that local actions can have positive benefits for reefs.
I think that's really important to have in mind.
Keller:
[1:02:40] Yeah perfect well thank you professor wrong it's been wonderful thank.
Brent:
[1:02:44] You thanks so much.