So here we are in Antarctica and we're here to try and address an ecological mystery.
So we're here studying the sea ice which is an amazing habitat for microorganisms.
There are bacteria there are microalgae and we call them
extremophiles. Some of them are actually able to thrive within the ice. They're present all
the way through the ice column but mostly are concentrated in the bottom 10 centimetres.
It is also a habitat that ebbs and flows,
so at its greatest extent there is about 20 million square kilometeres of sea ice.
In the summer months when we have perpetual sunlight the sea ice starts then to to melt.
When the ice begins to melt all those millions and millions of cells are liberated back into
the water column. They form the base of the food chain for the entire southern ocean ecosystem.
A lot of my research over the last 20 years has focused on photosynthesis - so the microscopic
plants just like plants that you see around you in a terrestrial environment are producing oxygen.
They're producing the oxygen that we breathe. A very recent discovery, only about 20 years ago,
is another type of light harvesting capability, specifically in bacteria. So like you and I,
bacteria typically consume other sources of food but what we've found in Antarctic sea ice and in
fact in just about every ecosystem that we've looked, is a brand new type of phototrophy. And
the phenomena that we're studying - rhodopsin photobiology - for microbes it allows them to
attract energy from the Sun. But it's in a brand new way - it is not photosynthesis as we currently
understand it. And what fascinates me is that up to 80 percent of all the prokaryotes, so all the
bacteria, in any given ecosystem appear to have the capacity to produce these proteins that can
attract and utilize energy from the Sun. But we don't know what they're doing with that energy.
So what we're interested in doing is establishing what is the relationship between sunlight
and this generation of energy within these cells. What is really unique about coming to Antarctica
is that we have an ecosystem that is static. What we are doing this year with our experiments
is exposing these microbes to quite specific colours of light to see how they will respond.
Our first mission if you like was to install or attach to the surface of the ice acrylic sheets -
some blue, some green and some red. And that is a technique whereby we can influence the wavelengths
of light that these microbes are exposed to inside the ice. So you can almost think of it as a study
in the relationship between the Sun and some of the oldest and simplest organisms on the Earth.
What's particularly fascinating is the fact that as we influence the light within the ice
these microbes are able to respond accordingly. Howthey attune to the Sun and how they then make
the supplementary energy with respect to specific wavelengths is still a mystery.
So what we're essentially trying to do here is better understand how light,
particularly wavelength which we're representing with colour,
affects the microbial community throughout the sea ice column.
We're doing that by using the plastic sheets but it's also important to remember that light
behaves differently as we move from the surface of the sea ice column down to the Southern Ocean.
So as part of our experiment here my colleagues have already drilled three holes.
And these holes go all the way through the beautiful white and blue sea ice
down to the biomass at the bottom which is where we get this brown colouration from.
Because these colored sheets have been put out for a few days they've been tampering with the things
underneath the ice. So what you see us doing today is removing what might be affected putting it off
to the side and we're drilling new holes with fresh biomass that hasn't been affected by these
colors and putting it back in. And we'll over time pull each of these three and that's going
to give us a lot of information not only about how the colour is affecting the microbial community
within the sea ice, but also how the gradients that happen in the sea ice from the part that
touches the Southern Ocean all the way back up to the surface where we're standing, can affect the
microbial community and its ability to survive. So my colleagues have started drilling some cores for
us so we can take a look at how we extract the biomass from the bottom of the sea ice column.
What we are mostly interested in are the bottom 10 centimetres.
So now we've got it prepared we're going to take it to the lab for sampling.
Even though it doesn't look like there's much going on there's actually millions of cells
just down in the bottom here and so all I want to do is fill in the top of this vial. It will melt
and then we're going to store it at negative 80 degrees with liquid nitrogen.
So this sample is prepared now. Now this puck is ready to go back
out onto the ice to be redeployed under the green perspex that we saw earlier.
So this is going to be the top of core one and we'll work our way down to the middle and then
the bottom. We've taken the old sea ice, we've added in the new biomass pucks, we've put it
all together and it's time to put it back in the hole. Here is the top puck with biomass
and we're going to put the green perspex back on top and screw it down.
And we're done ready to move on to the next colour acrylic sheet. So the reason that you
see us doing three cores is that we've set this up to be a time interval study. We're going to
come back in seven days, 14 days and hopefully 21 days, so that we can get a really big snapshot of
what happens when we change the light treatment over longer periods of time. That's especially
important because bacteria that live in the ice take a really long time to grow and multiply.
So one of the ways we look to understand this process is to actually go within the cell. So we
can use molecular biology to determine are these special genes, the genes for these rhodopsins
present? And are they being expressed? So the cell also has the decision whether or not to utilize
this capacity to harness energy from the Sun, and whether or not those genes are turned on and
whether or not the genes then create the proteins that do the job. We're also able to look at that
and that tells us to what extent the different wavelengths of light are triggering the response
within the cell to harness energy from the Sun. We also need to gain an understanding of
what is happening in the water column. So here we have a small ROV. Right now we're going to
use this to get beneath the ice to take a look at our perspex experiment from from the bottom
of the ice to see what it's actually doing to the algae and the bacteria under there.
So an ROV is a remotely operated vehicle, so think of it as sort of like a
small remote control submarine.
It's controlled by a remote that has a screen on it to actually let us see
what the ROV is seeing and then we can record that video as well. That gives
us some really powerful images of what our experiment is actually doing yeah
What our experiment is doing is we're affecting the light that these little microorganisms are
experiencing. So when we place a green sheet of perspex down we filter out all
of the colours of light except for green light. So when we drive the ROV beneath
it and you're seeing a green square that's green light coming through the ice. So same
thing with the blue and the red perspex and that means the little organisms in the ice
are growing under blue or red or green light which is what our experiment is looking at.
So from the surface of the ice all you see is white right? Ice and snow,
but beneath the ice it's a completely different environment. There's a ton of algae, there's this
layer of really beautiful fragile platelet ice and we're seeing that sort of sub ice ecosystem.
It's a really unique marine environment and even this morning we heard some seals as well - the
way they communicate with each other beneath the waters with these sort of whistles and and thumps.
So we were on the ice and we just hear this this guttural grunting and sort of wondering
if something was running into the bottom of the ice but it was the seals talking to each other so
that was pretty special. So this sea ice ecosystem here in the Ross Sea and generally across a lot of
the Antarctic is a highly seasonal ecosystem. So here during the spring and summer the Ross Sea is
covered in ice and there's a lot of growth there's a lot of biological activity in the ice. And
that's really important for the rest of the marine ecosystem, because as this ice breaks up - which
all of this ice will break up here in probably a couple of months - all of that organic matter,
all of the algae and nutrients in the ice is released into the water and that leads to this
huge phytoplankton bloom in the Ross Sea. Then you start getting higher trophic levels and so
what that means is sort of penguins and whales and seals and those much larger marine mammals
and marine species come in here. And it's really interesting because it experiences
this huge change every single year. So the ice freezes, algae grows in the ice and then
the ice breaks up and all that is released and you get this period of very high productivity.
In a changing world with predictions of less sea ice in the future, these tiny tiny little
microorganisms' capacity to adapt and then to maintain the entire southern ocean food chain is
a fascinating thing to study. And we hope that they do have this capacity to adapt
but we don't know. So we're dealing with some of the oldest organisms on the planet and some of the
simplest - they're single cells. It's a staggering amount of energy coming into the ecosystem
going - we don't know where.