Hi.
My name is Julie Huber, and I'm an oceanographer at Woods Hole Oceanographic Institution.
My background is in marine science, microbiology, and molecular biology.
And what I want to do today is tell you a story about how I've woven those three fields together,
studying life in the deep ocean.
But to start out, in Part I of this talk, I just want to give you a really broad introduction
to microbes and how they operate in the deep ocean.
So, first, I need to convince you that microbes are important and they basically run our planet.
So, I like to think of Planet Earth as also Planet Microbe.
Microbes are so-called "simple" organisms but in fact they can do some pretty complex things.
Shown here is a very basic Tree of Life, where we have the two domains of life
that belong to microbes: bacteria and archaea.
Now, microbes have no true nucleus.
They have a single chromosome.
They don't have any membrane-bound organelles.
And they divide by simple binary fission.
However, given how simple they are, they take up a huge diversity of life on our planet.
This is a much more complicated Tree of Life that's been put together using the power of
DNA sequencing.
And just to orient you on this tree, you're down here, in the eukaryotes at the very tip.
The rest of the tree, in the bacterial and archaeal domains, are taken up by microbes.
So, they fill up a huge phylogenetic space on our planet.
These microbes are not only diverse, but there are a huge amount of them on the planet.
So, there's upwards of a hundred million microbial cells in a single gram of soil.
And there's more biomass, or more carbon, trapped inside these microbes
than plants and animals combined.
And if you were able to in fact count every microbial cell on Earth, you would see
that there are more microbes than stars in the universe.
These microbes come in a lot of shapes and forms and colors, many of which are illustrated here.
And they serve a huge range of functions on our planet.
Some of these are probably familiar to you, such as the microbes that provide our drugs,
over here, in the form of antibiotics.
They also help us make food, things like cheese and beer, which we all enjoy.
They also help plants grow, for example, by fixing nitrogen in the soil.
And of course, the oxygen that we breathe on our planet, many microbes,
in the world's oceans in particular, make that oxygen through photosynthesis.
They're also really important here, in the human body, right?
We are covered with microbes, and they fill our insides, and they keep us healthy in most situations.
And in the oceans, they also play a really critical role in associations with other animals,
such as coral reefs, and also, recently, with the Deepwater Horizon oil spill.
It was actually microbes that were primed to eat oil that were the first responders.
These were the microbes in the ocean that ate a lot of the carbon and the hydrocarbons
even before scientists and engineers were able to fix that problem.
So, we have a lot of things on our planet to thank microbes for.
And what I want to do now is show you how they operate broadly in the ocean,
and then move into the deep sea.
So, I already called our Planet Microbe, but it's also obviously Planet Ocean.
70% of the Earth's surface is covered in seawater.
And in the oceans, microbes do some pretty amazing things.
This is another way of looking at the ocean.
This is basically a map showing the topography of the seafloor and the continents.
And what I really want you to notice here is these large swaths of blue.
This isn't seawater.
This is actually the bottom of the ocean.
And there's a huge range of features on the bottom of the ocean, which I'm gonna be
talking about today.
And the microbes that are living in the deep sea.
So, before I get deep, I wanna make sure you understand how microbes operate in the surface ocean.
And this is a really complicated look at how they work in the surface ocean.
But the very basics are that there are microbes in the surface ocean that are using sunlight
to fix carbon, over here, and they produce oxygen, and this moves a bunch of carbon
into the microbial food web and higher life forms.
We can really simplify this diagram, though, and look at those key players again.
So again, we have photosynthetic primary producers up here.
And that carbon, also called dissolved organic matter, it feeds a lot of different organisms.
But the first step is it goes into heterotrophic microbes, organisms that eat that organic carbon.
We then have the secondary consumers, which in this case are grazers.
Things like copepods or zooplankton.
And this feeds into sort of our classic food chain, higher life forms like fish and crabs
and things like that.
One important component of this microbial food web are these viruses, shown over here.
And I'm not going to be talking about viruses today.
We mostly think about them in causing the flu and things like that, but viruses
are actually also very important in cycling that carbon, and also moving genes around
between microbes in the ocean.
So, in the deep ocean, what we need to do is flip this whole picture upside down.
So now, instead, what we have for our primary producers are microbes that are harnessing energy
from the Earth's crust, down here, and fixing carbon.
So, these primary producers are not using sunlight.
Instead, they're using chemical energy, and I'll be talking more about that as we move on.
But we have a lot of the key players... the same key players as we do in the surface ocean.
So, we have this carbon being produced.
We have heterotrophic organisms consuming it.
We have these grazers.
But what of course is most interesting about these systems is the higher life forms
that are supported by these microbes look very different.
Importantly, we do also have viruses in the deep ocean, although we know very little about them.
So, what do these ecosystems look like?
Well, this is one example, perhaps the most well-known example, of a hydrothermal system
being supported by these microbes in the Galapagos spreading ridge.
This is where hydrothermal vents were first discovered in 1977.
And what you're looking at are these giant tubeworms that have sort of a fake gut
that is packed full of bacteria.
And what those bacteria are doing is harnessing chemical energy from the fluids leaking
out of the seafloor.
They're fixing carbon.
And they are producing the carbon that then feeds the worm and the other animals
you can see in this movie, like there's some squat lobsters, these are limpets and other organisms.
And so we're supporting an entire ecosystem in a very different way than what we have
in the surface ocean.
These types of ecosystems are called chemosynthetic ecosystems.
As opposed to the surface world that we all live in, which is really driven by photosynthetic organisms.
So, the fact that these ecosystems exist was a huge surprise to science when they
were first discovered in 1977.
They were not predicted.
There was no hypothesis that giant tubeworms would be living at underwater volcanoes.
And the fact that it exists really has to do with this long-term interaction
between Earth and life on our planet, for the billions of years of Earth's history, and in particular,
the last 3.5 billion since life first originated on this planet.
And what happens is the rocks that make up the surface of our... the bottom of our ocean,
they interact with seawater and create a variety of energy sources that can support life.
And I'm gonna spend the next couple parts of my talk only talking about one potential example.
But I do want you to appreciate that there's actually a huge range of environments on our planet
that can use this water-rock reaction to support life.
Now, I just wanna go into that a little bit to help you understand the broad differences
based on these water-rock reactions.
So, shown here is a highly schematized version of oceanic crust, right here.
And at the very top are these rocks called basalt or mafic rocks.
And if you've ever seen videos of... like the Big Island of Hawaii erupting, for example,
that's the type of rock that's being erupted there.
When basalt reacts with seawater at high temperature, you get things like hydrogen sulfide and iron,
which microbes really love to eat.
And as a result you get ecosystems like the one I just showed you the movie of,
at the Galapagos spreading ridge.
In the last 15 years, however, oceanographers have discovered a variety of different types
of habitats with different types of water-rock reactions occurring.
So here, if we go to deeply buried rock, which sometimes gets thrust up onto the seafloor,
we get rocks that are called ultramafic.
And when these rocks react with seawater, you get very different food sources for microbes.
You get things like hydrogen, methane, and even simple organic compounds.
And in turn, these ecosystems -- this is one example called the Lost City hydrothermal vent field --
they look different, the microbes are different, and the animal communities
are thus different.
So, there's this very, you know, deep connection between the types of rocks present,
the types of microbes, and then the other life forms that you can get.
So, as I mentioned, I'm only gonna be talking about one ecosystem in detail today.
But I really want you to appreciate that there's a huge range of water-rock reactions on our planet
that can sustain life.
And they include everything from mid-ocean ridges, where plates are spreading apart;
to volcanic arcs, which are very common, in particular in the western Pacific;
to even really cold environments, where fluids are just eking out of the seafloor.
So, I've been studying these ecosystems because I'm especially interested,
not only in the life at the seafloor but also life beneath the seafloor.
And this is a relatively new field of study.
But I really like this cartoon that was in an article in Nature a number of years ago,
kind of illustrating very simply the habitat I'm interested in studying.
So, this is seawater.
And beneath all that seawater, as I already mentioned, is the seafloor.
And you have marine sediments.
And then, beneath that, the rock.
And within those sediments and rocks are microbes.
And I'm especially interested in those microbes in these rocky environments.
And the way I study them depends a lot on what the question is, but in particular
go to places where fluids are naturally leaking out of the seafloor, such as at volcanic systems,
and sample those fluids to infer what's happening beneath the seafloor.
This is a really exciting area of research, I think, because it's very exploratory in nature,
and we don't know that much.
But the general idea is that seawater is circulating not only through the ocean but also
through oceanic crust.
And so this is very similar to aquifers that we have on land,
where groundwater is moving through some matrix.
And in this case, it's seawater moving through the rocky ocean matrix.
And that's illustrated in this cartoon, where there are areas of the seafloor where seawater
enters the crust and travels for some period of time.
In some cases, we have no idea how long.
In other cases, we've constrained it to a few hundred years, or a few days.
But along this pathway, the seawater gets modified.
And the seawater can change in its chemistry.
But it's bringing microbes and viruses and nutrients with it.
And eventually, it has to pop back out somewhere.
So, in this case, at points of hydrothermal discharge.
So, in all cases, and what I'm going to be talking about today, is finding those points
where it's popping out.
And basically capturing those fluids, and trying to understand what's happening
beneath the seafloor.
So, as you can imagine, this is a pretty challenging thing to do since I've never walked
beneath the seafloor.
I'm always looking at the seafloor, trying to figure out what's going on beneath it.
So, to do this, I often have to go to sea.
And this is one example of a ship that we stay on for weeks at a time.
This is the RV Atlantis, which is operated by Woods Hole Oceanographic.
And the ship is fully equipped to take a bunch of scientists, engineers, and ship's crew.
And they basically take care of you while you're doing your science.
And once we're on the ship, we also need a way to then get to the bottom of the ocean.
Most of the systems that I study are a mile or more beneath the surface of the ocean,
so we need vehicles and instrumentation capable of handling the deep pressures...
the great pressures and depths of the ocean.
So, shown here are a couple examples of how I study the deep ocean.
Up here is a remotely operated vehicle called Jason.
So, this is a vehicle that's tethered back to the ship, so no people actually go
to the seafloor in it.
And we gain... we get... because of that cable, we get video, and we can interact
with the vehicle the entire time to collect our samples.
Shown next to that is the human-occupied submersible called Alvin.
This is the vehicle that first discovered hydrothermal systems.
And two scientists and one pilot go down.
You basically launch after breakfast; you come back at dinner.
And it is not attached to the ship in any way.
So, the people on the ship don't really know what's going on, but you get to
go to the seafloor and do your studies that way.
There's a couple other examples here.
This is a vehicle called Nereus, which unfortunately imploded a couple years ago and was lost.
But Nereus had the ability to go to the greatest depths of the oceans, up to 11,000 meters.
And finally, shown here is something I'm gonna be talking about in Parts II and III,
which is, instead of sending ships and vehicles, oceanography is trying to move toward
more observational science using infrastructure that's constantly in the environment.
This is obviously really challenging in the deep ocean.
But what this is showing is a number of cables that have been put on the seafloor,
basically plugged in to land, so we can constantly monitor and take samples more frequently
than when we have the opportunity to go on these ships.
So, this is a shot of me diving in Alvin, which is, as I said, one way that we do our work.
It was definitely one of the coolest experiences of my career, to travel, you know,
thousands of meters -- in this case, 2,200 meters -- to the seafloor to study these hydrothermal systems.
If we're using a remotely operated vehicle, we have a control station up on the ship.
And this is an example of what I see sitting in that room, where we have a group of pilots
sitting at the front and engineers who are operating the vehicles.
And then scientists interacting with them to get our samples, to navigate on the seafloor,
and things like that.
Once our samples are back, in my lab we use a huge suite of tools that draw on the training
that I've had in microbiology, molecular biology, and ocean sciences.
And just a few examples are shown here, ranging from chemistry to trying to grow these microbes
in the lab, which is especially challenging given the pressure and extreme conditions.
We do a lot of engineering on the side to try to get our samples back.
And what I'll be talking about Parts II and III is kind of combining genomics and stable isotopes
to understand how we can go from DNA, down here, all the way up to
how this ecosystem functions.
So, if you stay tuned, in the next part of the talk I'll start focusing in on some of these methods,
and how we use them to study sub-seafloor life.