Antje Boetius: Why the deep sea is so important

In this edition of The Naked Scientists, deep sea microbiologist Antje Boetius explains how she discovered methane-consuming microbes, and why the seafloor is such a precious and important ecosystem...

Will - Now, as you said, these microbes convert, via chemical means, methane into carbon dioxide. And as you said, again, they are all over the world. So presumably this is a lot of methane that is getting converted.

Antje - That's exactly so. So in the very beginning when I worked on this problem a lot, I often got the question by people, is that a useful knowledge? So with that knowledge that these organisms exist, can we do something? Can we cultivate them? Can we make them eat methane from the atmosphere? Because methane is actually an aggressive greenhouse gas. It is 22 times more potent than CO2. And it is very stressful in our times where basically every gigatonne of carbon counts to know that there's so much methane leakage from the ocean, from our industry, from the cows and so on. So there was often this question to me like, can one use your microbes to control methane fluxes? So when you know these deep ocean floor microbes and when you know how slow they grow, it actually takes them months to double. Then, you know, this is not really something you can build a world's climate savings from. When you know that they live without oxygen, that they need a certain surrounding and environment and they grow better with a bit of pressure, you know, that it's actually, it's fantastic that nature has such microorganisms, but it doesn't look like they are immediately relevant to biotechnology. However, my answer was always just think about these organisms providing their services since really almost billions of years. We humans, we live on this planet not even knowing them. The planet runs the way we know it because it's of those microorganisms in the deep sea that have this job of controlling the methane. Would they not be there? And would all of that methane leak out from the ocean into the atmosphere? It would be a completely different planet. We couldn't live on it. And so my answer to why is that knowledge relevant is because it helps us understand how planet Earth functions and that this network of life of which we know not so much is essential to make the planet habitable. And so we humans, we better know who lives with us on this planet, that we don't produce mistakes, that we don't increase our risks because we have overseen that certain organisms, certain species in life are essential for the functioning of Earth, and essential for our way of living.

Will - As is so often the case in conservation, it is always best just to leave stuff alone and think better than to add to it or try and add your own. Which kind of brings us to the subject as, given you're a leading authority on the deep sea, I'm sure you're aware of the deep sea mining sort of expansions that certain countries have been looking to expand operations. Do we know what kinds of impacts this mining could have on the deep sea and therefore the sort of methane fixing that's going on?

Antje - Oh, well, in a way we could simply theoretically figure that out by understanding what resources are to be mined. Where are they, how much of the sea floor would it destroy and where and what other forms of life are living there and what is their function? So what my lab and I were studying, we were simply thinking like, what if you plug out the manganese nodule, which is one kind of a resource that in theory could deliver valuable metals, rare metals. So when you look at these manganese nodules that look like a black cauliflower <laugh>, in a way, these manganese nodules take millions of years to grow. So we could pick them only once and then they would be gone. And so when you pick them, they're a bit like when you pick up a rock from your garden, you pick up a rock and then another rock and, and on the rock is all kinds of life and insects and tubes. And so the manganese nodules themselves are kind of a home to a lot of different species. In fact, we found that some sponges in the deep sea grow only exclusively on manganese nodules and only on the sponges with some octopods lay their eggs and breed. And so again, we found so many stories about the network of life that depends on the nodules and in the intact sea floor that we found. Really, it's hard to imagine that there would be a sustainable way to take out some nodules and sea floor without destroying or harming life. And so what we do is regularly publishing our data, just alerting us of the risk that we cannot be sure that even if it's a limited area of sea floor that is destroyed, that it will not take down entire species of life because we just don't know enough. Where do they live? Are there enough around? And so that's why we find it a big risk at the time when there's so little knowledge about sea floor life. Then we also found that some of the nodules have a radioactive surface and some of the materials are toxic and the valuable metals are only a tiny percentage of these resources. And then you have to go somewhere with a lot of waste, toxic metal, maybe radioactive waste. And so the whole business case is actually also understudied and it's not clear if there would be a good business case for that. And so in many areas, we just don't have enough knowledge.

Will - Unfortunate for the deep sea, given that, as you said, it's such a slow moving process. They haven't needed to do anything quickly. They live in a dark, cold world. They've never had to encounter anything as frantic as a human being. <laugh>. They've never needed to know this sort of life where suddenly somebody could come in and tear up the entirety of the seabed.

Antje - Yeah, that's correct. So the speed of things is because it's so cold, it is slower than at the surface, which also makes the case for a whole different area of research that is super interesting. And that is really the biology of deep sea life. Now, a lot of the deep sea life forms, for example, deep sea sponges, deep sea corals, some deep sea fish, they get immensely old. And so their relatives that live in shallow water, so closer to the coast, they are not so long lived. And so there is something about life in the deep sea that is maybe slower, but also healthier because how can you be a sponge, for example I worked on arctic deep sea sponges, and get like many, many hundred years old. So we found some that are 400, 500, 600 years old, and they're healthy, reproducing, and growing really well also. And their counterparts in shallow waters, they maybe do 30 years, 40 years. That is interesting. And so for so many species in the deep sea, we still have to solve these deep biological answers. How can you be programmed to get so old? And even for the microbes, as I said, some of the microbes in the deep sea get very, very old. And that's intriguing. So is that a gene that determines how old they get? Is that biochemistry? What is it actually that some organisms are so long lived?

Will - Maybe the take home message of this really is everyone take it a bit slower and you'll live a longer, better life.

Antje - <laugh>. Yeah. And the cold helps too. Apparently, the absence of sunlight as we know might help there as well.

Will - That's a life I'm already living, so I look forward to reaching 200. One of the other things that I think I feel I have to ask and feel free to tell me this is absolute nonsense, but in terms of aerobic oxidation and methane, the early world, the early earth, was pretty hostile. Not a lot of oxygen around. How realistic is the theory that maybe the first organisms used this very mechanism?

Antje - <laugh> Yeah, that's a good question. Yes. For the longest time, Earth was anoxic. And even little amounts of oxygen got immediately consumed because there were reduced metals around and the chemistry was, you know, just sucking up any oxygen that ever emerged. However, these microorganisms, when we look at their genome and their abilities, it's super complex. So to have a suite of enzymes that allows you to break methane, activate it, and respirate with sulphate, that is a long, long list of enzymes you need. And so, as we say today, it is not imaginable that very early on we would have photosynthetic organisms because again, it's so complex to run photosynthesis. You might say the same for the methane oxidisers, that it's just too complex, all the enzymes they need to function that could not possibly be and a really early metabolism. So today we think more about hydrogen consuming microorganisms or maybe, maybe fermentors. But not really neither methanogens, nor those that make methane or those that break methane.