Newly-discovered whale graveyard dates back millions of years

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1:17Welcome back to The Nature Podcast. This week, a newly discovered whale necropolis. And turning plant material into chemical building blocks. I'm Benjamin Thompson. And I'm Sharmini Bandel.

1:43A team of researchers have made a completely unexpected discovery seven kilometres below the surface of the Indian Ocean. When we're at the seafloor, we didn't know what it is. But when we get back to the laboratory, we find, oh, this is fossils. This is Zhao Tongpeng from the Institute of Deep Sea Science and Engineering, part of the Chinese Academy of Sciences. He was part of a team who made multiple voyages in a specialised submersible, capable of withstanding the enormous pressures found at the bottom of the deep ocean floor. During their dives, the team found a lot of fossils. In every dive, we found not just one, but maybe two, three or ten.

2:32Analysis revealed that these fossils were whale bones, one of which was dated to 5.3 million years ago. The team had stumbled upon what they describe as a whale necropolis, and they got a paper about it out in Nature this week.

2:56Now, when we think of fossils, we typically think of bones that need to be dug up. In this case, though, the fossilised remains of these wells were essentially just lying uncovered on the seabed, in what's known as the Diamantina Zone, a deep 1 ,200km long indentation on the ocean floor west of Australia. Its location out in the ocean helps explain why these bones were lying there waiting to be discovered. Here's paleontologist Stephen Godfrey of the Calvert Marine Museum in the US to explain. Since you're so far away from any continent, right, you're not having the influx of continentally derived eroded sediments carried by rivers.

3:35So you don't have sands or silts that are like covering over. So that's why it was so readily available to the people in the submersible vehicle to sort of pick up all these specimens and bring them to the surface. Zhao Chong and his colleagues explored 32 small patches of the enormous Diamantina zone, and they found 476 fossils. Most of the fossils were fragments of beaked whales, including a previously unknown extinct species from this group. These whales are reclusive animals who inhabit deep waters, and the males in particular have hard bony beaks, which are much more likely than the bones of other species to survive and fossilise.

4:13While other species and other bones have been broken down over the millennia, these hard beaks remain. Strontium isotope dating showed that the oldest of these specimens had died approximately 5.3 million years ago. The most recent bones, however, weren't fossils at all. They were the bodies of whales that had died relatively recently, and these remains were feeding a whole host of deep sea creatures. So that is like a sea floor garden. So you can see a bright star as well as some clay which can use the chemical energy to grow up. There were other organisms living on and around the remains too, like pale, feathery, bone-eating worms.

4:56These are creatures that rely on whale carcasses for food down in the depths where no light can reach. When whales die, their bodies bloat up with gas and may float up to the surface and drift on ocean currents. If and when they eventually sink to the seafloor, this so-called whale fall can provide a feast for deep-sea creatures. A single whale carcass can sustain a miniature localised ecosystem for decades. But when it comes to the whale necropolis that Zhao Tong found, there's an important question that remains unanswered. The question is why so many choose this place to rest on peace? The team's submersible has visited the ocean's depths many times, but the vast plains of the deep are relatively barren compared to the density of bones in this narrow region.

5:44Well, graveyards can be found in different places around the world. In some places, collections of fossils are thought to be the result of mass strandings or groups of whales killed by toxic algal blooms. But no other whale graveyard has been found as large as this one, as deep below the surface, or with this unique mixture of new and ancient bones. Since the team think that whale carcasses have been collecting in this spot for millions of years, it's understandable that Xiaotong wants to know, why here? The team's current best guess is that the shape of the seafloor trench essentially acts as a V-shaped funnel directing the flow of water.

6:21The bottom current can concentrate those carcass and transport those carcass on the bottom of the trench. This may be part of the answer, but there are other things to consider, such as surface currents and the behaviour of the whales, including the fact that beaked whales are some of the deepest diving cetaceans. It's currently unknown how all these factors contribute. But solving this mystery could reveal whether this kind of continually growing whale necropolis is one of a kind or whether it points the way to other lost graveyards. What's certain is that Xiaotong and his team have discovered the deepest whale fall community ever found, filled with strange and exciting creatures far below the sea.

7:05The combination of living ecosystems and ancient fossils makes this a unique sight in the field of paleontology. Stephen, who you heard from earlier, was excited by the finding. I was just like blown away. Stephen has written a News & Views article for Nature about the research. He says that the specimens found so far could be just a fraction of the total fossils left in the as-yet unexplored areas of the Diamantina zone, and that it could provide researchers with a chronological record of the evolution of these mysterious beaked whales. So if the dates are accurate, and the oldest is like over 5 million years old, and who knows how much older it could go, but it would essentially be continuous.

7:47There would have been no reason for there to be any hiatus or break in that fossil record. So in theory, in that trench, we have a continuous record of the diversity and abundance of beaked whales that lived in that part of the southeastern Indian Ocean. And we're going to be able to document the evolutionary history of these lineages of beaked whales, which we would never have access to in typical terrestrial type environments. So that's one thing that I find super exciting about this discovery. Xiaotong's team have so far explored less than a square kilometre of the total area of this long, thin groove along the ocean floor.

8:28Yet each of their 32 dives reveal multiple fossils. There's undoubtedly a lot of research yet to be done here on both the fossils and the living creatures that make their home feeding on the whale remains down here. The team are continuing their work exploring the deepest areas of the world's ocean, and Jiaotong says they may return to the Diamantina zone next year. A key task is to figure out how this whale necropolis formed here, but they're also keen to explore deep-sea trenches in other parts of the world where beaked whales live, and to see if fossils of their bony beaks are also accumulating elsewhere.

9:04Whether it's whales or brittle stars or bone-eating worms, The ocean depths still have a lot more secrets to reveal. I feel very, very excited because you just use your old eyes to watch a new world. So this is quite an amazing thing.

9:27That was Zhao Tong Peng. You also heard from Stephen Godfrey. To read Zhao Tong's paper and Stephen's News and Views article, head over to the show notes for a link. Coming up, a new way to turn sawdust into a building block of nylon. Right now though, it's time for the Research Highlights with Dan Fox.

9:49A study of almost 100 ,000 expectant parents has found that giving pregnant people money can increase the birth weight of their babies. The research found that a government-led programme that provided cash transfers, home visits and nutrition counselling to pregnant people in the state of Rajasthan in India was associated with an increase of around 70 grams in mean birth weight. Low birth weight is associated with an increased risk of dying during childhood and is a persistent problem in several Indian states. The team behind this paper studied an initiative that provided up to 6 ,000 rupees, around 70 or 80 US dollars at the time, to people from a low-income indigenous population who were in their second pregnancy.

10:31The authors found that around 29 % of babies born after the interventions began had low birth weight, compared to almost 35 % of babies born to mothers who were enrolled in the program but gave birth before the payments began. You can read that research in full in Nature Health.

10:52Seafloor trails left by animals more than half a billion years ago could be the earliest evidence of the evolution of vision. These solidified remains of trails left by primordial creatures on muddy sea floors are the earliest known evidence of animals' locomotion, dating back to the Ediacaran period, some 635 million years ago. Sophisticated eyes don't appear in the fossil record until the subsequent Cambrian explosion, when predators and prey became locked in an arms race of improving vision. Researchers examined 231 trails from the end of the Ediacaran and the start of the Cambrian Explosion for clues about the early animals' senses.

11:34Earlier trails tended to scatter in random ways, the authors found, but later ones were more likely to loop around to cover previously unexplored terrain. Simulations showed that the earlier patterns emerge from animals foraging using only non-visual senses, whereas later ones are consistent with longer-range sensing. Use your sophisticated senses to find that research in the proceedings of the National Academy of Sciences of the United States of America.

12:05When it comes to chemistry, some of the most useful molecules around are known as aromatic hydrocarbons. Featuring a ring of six carbon atoms, they're the building blocks for so many other things. plastics, pharmaceuticals, you name it. But aromatic hydrocarbons have a downside. They are petrochemicals. Ultimately, they're made out of oil, meaning these molecules have a significant environmental footprint. There is another potential source of aromatic compounds, though. Plants. Specifically, a polymer called lignin, a major component of plant cell walls, which helps them to stand up straight, is vital for water movement and for protection against pathogens.

12:53Lignin is abundant, renewable and it's made up of lots of aromatic compounds, but it's been hard to get at them and use them in a meaningful way. This week though, a team describe a hybrid approach, using chemistry and synthetic biology to refine lignin into a specific molecular product called adipic acid, which is needed in the production of a type of nylon called nylon 6-6. To find out more about the research, I spoke to one of the team, Glenn Beckham, from the National Laboratory of the Rockies in the US, who took me through their process. Before then, he described why lignin has been so difficult to work with.

13:36So lignin, it's a very heterogeneous polymer. It's made up of three different aromatic monomers that are combined together in a random way. You know, most polymers that we think about that are used like as plastics, you know, have very regular repeat units, right? Lignin, on the other hand, doesn't have necessarily a perfectly linear structure. And the linkages between each of the aromatic building blocks can vary, right? Sometimes they can be carbon-oxygen bonds. Sometimes they can be different forms of carbon-carbon bonds. and all of that together that that heterogeneity of lignin makes it a major challenge for chemists and engineers and biologists to go in and access aromatic building blocks that could then be used to go and say make new materials or make interesting compounds and so what was it you were looking to overcome then about 12 or 14 years ago or so our group and several other groups around in the world, sort of all at the same time had this idea of in nature now, lignin is broken down by fungi and, you know, maybe some bacteria.

14:46And in nature, you know, you take this heterogeneous polymer and you break it down and it's going to produce a heterogeneous soup of aromatic compounds. But nature has already figured out how to deal with all of that heterogeneity. And there's all these soil bacteria, you know, in many cases, which have been really well studied, like the one that we work on. It has a large battery of enzymes that are able to basically take many different heterogeneous aromatic compounds and defunctionalize them all into a single aromatic compound. So that idea has been around for a long time. But the field has never been able to make high yields of single products from lignin in the tree.

15:23And that is simply untenable. Polymer building blocks are commodity chemicals, right? You need to be able to make them cheaply and at high yield, right? That's super important. And that's what you've shown evidence of in your paper this week, taking lignin and working it through to adipic acid, then this building block of nylon 6-6. We know that with petrochemicals, this is a stepwise process. Have you taken a similar approach here? So central to all of this is we always think about how do we use what is frankly like fairly old and I sometimes refer to as maybe boring chemistry that has precedent in scaling in other contexts, we start with sawdust, right?

16:03And so we take that sawdust, we put that into a batch reactor at high pressure, and that extracts the lignin out of the sawdust, right? And so then we get this oil that's sort of hydrophobic, sticky, and quite dark in color oil. We then put that into a flow reactor, and we remove all of the oxygen from that, and that gets us this much less viscous hydrocarbon aromatic mixture that has aromatic monomers in it and also has all of these carbon-carbon linked dimers and oligomers, right, and sort of larger molecules. We add oxygen to that. We add a catalyst to that. And that gets us to these aromatic carboxylic acids that are then able to be converted by a bacterium.

16:47The challenge has always been, what is your sort of single ring aromatic monomer yield that you can feed to a bacterium? We were able, in this case, to get around 71 weight percent yield of aromatic compounds that were bioavailable, that could be consumed by a bacterium. That can then metabolize those to continue the process. Right. So we use a model soil bacterium called Pseudomonas putida KT2440. It's like the E. coli or the Saccharomyces cerevisiae of the aromatic catabolism world. It's extremely tough. And we engineered it to consume all of the aromatic carboxylic acids, at least the high-yielding ones, and then to funnel those down into a single compound, which is muconylactone.

17:31And this is then what can be converted into adipic acid. So the cool part about muconylactone is it can go into two directions. One, it can be made into adipic acid, right? And so that can go directly to nylon 6-6. It can also be chemically converted into dimethyl beta-keto adipic acid that can be used as like a performance advantage to Nylon 6-6. And it gives it better properties for higher temperature applications, for example. Right, because Nylon has a multitude of applications. It's not just clothes. It can be food packaging and stuff like that as well, right? Yes, absolutely. I mean, often when we read papers, we get a sense of the actual chemical pathway, but not necessarily the amount.

18:07How much lignin are you starting with? Most of the development work that we did in this project, we did sort of at the 100 milliliter scale. However, to be able to demonstrate from start to finish, we definitely did scale this process up as well. We were able to extract lignin out of, you know, an eight liter reaction that's, you know, on the order of hundreds of grams of plant material. We took all of that through all the way to the biology step and we were able to run those in, you know, multi-liter fermentation vessels. And so we were able to produce, you know, tens of grams of product. And you tested this process using actual tree, poplar, I think you mentioned in your paper.

18:46Yeah, absolutely. We originally did all of the development using poplar, which is a well-known hardwood that's grown in many regions around the world. And then we were prompted and asked by the reviewers, rightfully so, can it work on other substrates? And so we tested pine and also birch, and it worked within error the same. And what will be of interest to folk is the overall yield for the whole process. and you managed to get 26 % of the lignin that could ultimately be turned into adipic acid. Now, this is half of the theoretical maximum. Potentially, you can get up to, what, 57%. Obviously, what you've achieved isn't perfect.

19:23What needs to be done to increase this, do you think? Yeah, definitely, you know, we're at about half of theoretical yield in this process. A lot of that honestly involves things like transfer losses that are inherent to small-scale experimental research. You know, when you put wood sawdust into a reactor and you then, you know, run a reaction, you have to go clean it all out, really washing that extremely thoroughly and things like this, you tend to get transfer losses. And at this point, it's optimizing each of the chemical steps. But I think much closer to theoretical yield as well within sight.

19:54And in terms of how you've gone about it, you're looking at this from a sustainability angle. What are some of the impacts of this method? Does it involve unpleasant solvents or anything like that? And energetically, how does it compare to conventional petrochemical production? The short answer, Ben, is we don't know yet. We have not yet done the rigorous process modelling, techno-economic analysis and life cycle assessments to be able to directly compare this to conventional processing. That is very much on the docket to answer those questions directly. So the jury's still out. And obviously, this was done in a very controlled environment.

20:32How do you think this might work when things are messy, like waste wood from a paper mill, something like that? That is absolutely the direction we want to go and we're actively working on now. How do we use, say, lignin from the pulp and paper industry that right now is just burned for heat and power on site? There's a lot of challenges there, right? That lignin is more recalcitrant to breakdown. It has sulfur in it. sulfur is notorious at poisoning catalysts and affects metallurgy in reactors and all kinds of things like this and yeah there's going to be a lot of challenges but i'm quite optimistic that we'll be able to get this to work and what is it that's important do you think about this paper is it what you've achieved or is it the method you've used to achieve it in this particular study nylon was kind of a performative product in some ways.

21:23One of the cool parts to me is that the tricks of metabolic engineering and synthetic biology, once you can get these aromatic building blocks at high yield to a bacterium, we can engineer it to make a whole bunch of different things, right? This study doesn't quote just make nylon building blocks, but it also gets you a high yield of aromatic compounds from lignin from a tree to a bacterium where we can engineer it to then make whatever product we want really. And that to me is I think what I hope was useful for the field. Glenn Beckham from the National Laboratory of the Rockies there. To read his paper, look out for a link in the show notes.

22:04And that is all for this week. So as always, it just remains for me to say, if you've enjoyed the show, do let us know. You can leave a review on your podcast app of choice, or you can reach out to us on social media. We're at Nature Podcast, or you can send us an email. We are podcast at nature.com. I'm Sharmini Bandel. And I'm Benjamin Thompson. See you next time.

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