- Good morning, everyone. Delighted to have you here. I'm Liz Cohen. I'm Dean of the Radcliffe
institute for Advanced Study. And I couldn't be more
pleased to welcome you to the Linda N. Cabot
Science Symposium entitled, "From Sea to Changing Sea--
a Science Symposium About Oceans." I'm especially pleased to see
so many members of the Radcliffe Institute's Dean's Advisory
Council here today. I thank them, along with
our Radcliffe associates, and many other faithful friends
of the Radcliffe Institute, for your support
for all that we do. At the Radcliffe Institute
for Advanced Study, scholars, scientists,
and artists work at the forefront of their
field and across disciplines. We are dedicated to
fostering and sharing innovative work with the
public in all subjects. But we are especially proud
of our strong tradition in the sciences, a tradition
that manifests itself in this annual science symposium
and in the related lecture series that runs throughout
the academic year. Science flourishes at Radcliffe
because of the many ways it intersects with
other disciplines. And we will certainly see
those intersections on display here today at our
science symposium. We are very grateful for the
generosity of Linda Cabot and her husband, Ed Anderson,
for their support of today's symposium, and also for the way
that they embody the Radcliffe mission. Linda Cabot, Class of 1980,
is the founder and president of an educational
organization dedicated to inspiring the next
generation of ocean caretakers. She is also a visual artist
and a lifelong sailor, who brings both of
these perspectives to her love of the ocean,
just as we here at Radcliffe bring a multi-disciplinary
approach to many urgent subjects. It is hard to imagine a more
urgent subject than oceans. They cover three-quarters
of our planet, and supply 50% of the
oxygen we breathe. As Secretary of State
John Kerry said last month at a conference on the ocean
hosted by the State Department, and I quote him, "Our
ocean is absolutely essential for life itself. Not just the food, but
the oxygen and weather cycles of the planet
all depend on the ocean. Throughout the world, the
sea sculpts the shorelines of our continents, and
influences the changing climate." Here in New England, the ocean
is especially inescapable. The coastline is literally
right at our doorstep. So concerns about rising sea
levels hit very close to home. Scientists predict that
sea levels in Boston could rise anywhere
from two to six feet by the end of the century. Our doorsteps, in other words,
are the very ones the rising seas are going to flood. But the ocean shapes far
more than our landscape here in New England. It undergirds our economy,
shapes our culture. It inspires our urban planning. It influences public
health, and much more. So when we say that the ocean
has an impact on climate change, we mean the economic
and cultural climates as well as the natural one. Let me give you some examples. Cod was once so plentiful
off the coast of New England that fisherman joked that they
could walk across the Atlantic on the backs of this
ubiquitous fish, and never get their feet wet. Now cod populations
have collapsed, partly because of overfishing,
but also because of the rising temperatures of New
England's coastal waters. In fact, the cod catch
has declined by fully 90% over the past three decades. One of our speakers today will
address this critical question. At the same time,
warmer waters have led to increases in stocks of
shellfish, including lobster. More lobster might
sound like good news, until we realize that the
sudden increase in supply can make wholesale
prices plummet. In 2012, the price paid
to lobstering crews fell to $2 per pound, compared
to the more typical rate of $4 per pound. And it caused real
economic hardship. One specific place where
shifts in the ocean have ripple effects on the
local economy and culture is the town of Chatham
on Cape Cod, site of the Monomoy Wildlife Refuge. Tides, storms, and
rising sea levels have redrawn the
boundaries of the Refuge. US Fish and Wildlife Service
has responded with a wildlife management plan that
Chatham town officials and Massachusetts attorney
general Maura Healy say will threaten
the fishing economy. Meanwhile, after generations
of careful stewardship, fishing families perceive
the outside restrictions as an attack on local identity. In short, oceans shape
our world and our lives in very real ways. If we want to
understand the ocean, then we need to look at it from
many different perspectives, which is exactly what we
are going to do here today. Scholars and experts
on subjects ranging from evolutionary
biology to oceanography will be sharing the stage with
public officials, a Coast Guard officer, and a law professor. Today's conference
has been argued organized by John Huth, the
Donner Professor of Science at Harvard, and Faculty Director
for the Physical Sciences at the Radcliffe Institute. I want to thank John
for putting together such a probing and
fascinating day for us. He is the ideal leader
for a Radcliffe conference about oceans, because so
many of John's professional and personal interests
have to do with the water. He is a physicist
who has written about the science of navigation
from the shores of New England to the Marshall Islands. And he is an expert kayaker,
who is as comfortable in a boat as he is in a computer lab. So please join me now
in welcoming John Huth. [APPLAUSE] - Thanks, Liz. So welcome to everybody,
and good morning. I think we have an
exciting program that will be very informative,
and you'll enjoy it. So let me just frame
my own interest, and how I came to set this up. As part of my explorations
of how people navigate, I went to the Marshall
Islands, and went on a voyage with an outrigger canoe
between two of the atolls. And we ended up on the
island of Tabal, which is on the remote atoll of Aur. And there, we were greeted with
flower garlands and a feast, where we had all of these fish,
and breadfruit, and lobsters, and crabs. And we were welcomed
with open arms. In a sense the people who we
were coming with and visiting were trying to revive the
culture in the Marshall Islands, which is under a
tremendous amount of stress, both from colonial powers,
but also from the encroaching oceans as the sea levels rise. And what might have been
an abstract thought prior to my visit there
became quite visceral-- how their lives were
inextricably linked with the oceans. And this hit home. And what I realized when
I got back to the States was that we, indeed-- our
fates are inextricably linked to the oceans, and we
come from the oceans. And we also put a lot
of stress on the oceans. So as part of the
Radcliffe duties, I suppose-- I'd hardly
call them duties anymore, because it's so enjoyable to
work here-- I put together this Science Symposium on
Oceans, which gave me something of a hunting license to
explore a set of topics that I found to be at
the frontiers of science, but also fascinating. And in trying to find
these speakers that you'll hear today, I realized
how incredibly complex the oceans are, and
the diversity of things you find in the oceans. It's just unbelievable. So I'm grateful for the
speakers that we have today, and I welcome you. I also want to thank Linda
Cabot for supporting us in this. She's done a fantastic
job and provided me with a lot of insight, too,
in conservation of the oceans. So I'm grateful for that. So let me invite our
first panel today. It's going to talk about early
life, and interesting life in the ocean. So we have Chris,
Peter, and David coming. You can take your seats
now, and I'll just say a few introductory words. So to frame this
a little bit, we had a recent talk on the
search for life on exoplanets. And the speaker talked about
looking for signatures of life that more or less are kind
of our conventional ideas of what life might be like--
carbon-emitting creatures and certain ratios of
gases that we would see. But it was very much tied to
a conventional view of life as we know it. And people were
asking the question, what about other forms of life? And the speaker said,
well, we can't really imagine other forms of life
than the conventional sorts of things. And it's difficult to imagine
what the origins of life might have been in an
earlier epoch in our planet. But then you start to
scratch the surface, and you look at people that
study different forms of life. And you realize that there are
some amazing forms of life that don't really conform to
our normal visions of what they might be in the oceans. And so what I tried to do
was assemble some speakers that could talk to that. So with little
further ado, I'm going to introduce Chris
Bowler, who we're grateful to have as a Radcliffe
Fellow here this year, who just kind of spoke up at
one of our initial meetings. And immediately, I was
able to start digging up some information. And the wheels started turning. He is a director of the
CRNS Institute for Biology, and Professor at L'Ecole
Superieure in Paris, and works on phytoplanktons,
and amazing to talk to. Chris. [APPLAUSE] - Great, well, thank you, John. It's great to be here. Yes, as John mentioned, I'm
based in Paris, normally. But I'm on sabbatical here
at the Radcliffe Institute as a fellow for this year. And it's a wonderful
opportunity to meet many people, and to explore new avenues
of research, and so on. And it's great to see,
also, that the ocean is receiving so much interest in
the US, as it is in Europe. We've had a lot of talks,
a lot of discussions, about the importance of
the ocean, a lot of concern about the ocean in
Europe, and it's great to see the same sort of
concern over here in the USA, too. So without further ado, I'll
introduce the first session, which is entitled, "Early
Life in the Oceans," which is a really
important topic, obviously, because everything
that is in the ocean to date came from this early
life in the ocean. In fact, everything--
all life on Earth-- evolved from the ocean three and
a half billion or so years ago. So we're all evolved from
these little organisms which started the process
of life on this planet. So it's a fascinating topic. We've got two great
speakers here, who will introduce their
research on the topic. We'll have two
talks, and then we'll have a discussion time
with questions and answers, and so on. So please save your
questions until the end. And so the first speaker
is David Emerson, who is Senior Research
Scientist and Associate Director for Bacteriology in
the Bigelow Laboratory for Ocean Sciences, which is a very, very
well-known institute worldwide, and also has a very,
very important culture collection of microorganisms
from the ocean. That is a very, very important
resource for scientists throughout the world. So thank you for being
part of this institute, and for the work you do. And I'll hand it over to you. [APPLAUSE] - Thanks very much, Chris, for
that very nice introduction. It's really terrific to
be here, to be leading off this symposium. I'm really excited to have
the opportunity to do this. We had a wonderful
dinner last night at Dean Cohen's residence. It was really amazing to
learn about the Radcliffe Institution, and appreciate
everything they do, and especially Linda Cabot
for supporting this symposium. So I'm going to
jump right in here. I have 20 minutes to talk
about three billion years worth of Earth history. So I think the reason
that rust features prominently in my title will
become apparent during my talk. But I want to emphasize
my talk will be entirely about the Earth's ocean. But for that reason, I actually
put in my opening slide here a picture of Venus
on the left and Mars on the right, as the
two other rocky planets that we share what's referred
to as the "habitable zone" in our Solar System-- that
zone in the Solar System where life could
exist, because there could be liquid water on
the surface of the planet. Venus very clearly does not have
liquid water on its surface. It's got a 95% CO2 atmosphere,
a runaway greenhouse, very much too hot on the surface
of Venus to support an ocean. Mars, we believe probably
did have an ocean several billion years ago,
but it lost its atmosphere at some point, and
now, it's much too cold to sustain liquid
water on the surface. So just to go into a bit
of Earth history here, I'll start with
this first slide, which shows the Hadean Period. So we're going to start at
the formation of the Earth, sometime between 4.5 and
4.6 billion years ago. This is an artist's
rendition of what times would have been like
that-- very violent, very hot, asteroids, meteorites hitting
the planet repeatedly. The Moon broke off from
the Earth at this time, it's thought. There would have been times
when the entire surface of the planet was
essentially magma pools, and again, could not have
sustained a liquid water ocean. But then, there this
period came to an end somewhere around four
billion years ago. And we came to
what we have today, what we call the Blue Planet. And this is a picture from
space, obviously, done by NASA. And I chose this image because
it shows the Pacific Ocean, primarily. You don't see many land masses. Antarctica is at
the bottom there. But this is presumably
what the planet could have looked like for the last
four billion years from space, was this blue planet that
has a sustained ocean. And that's why we're
here, because life could evolve and develop
because of this water world. And then as the
continents developed, we moved to the
continents, obviously. So the question then becomes,
what was this ancient ocean like? And that's the topic I'm
going to address today. And so what can we learn? So we can't learn much
by looking at water. I mean, you take
bucket of ocean water from anywhere, at any
depth of the ocean, or anywhere on the
planet, and you really can only get maybe
a few thousand years worth of Earth history. So from just
looking at water, we can't get a history
of the Earth, really. And so where can
we go to do that? Well, one place we can go is
to the middle of South Africa. This is a picture of my
daughter, [INAUDIBLE], and I sitting on a
banded iron formation in the Kalahari Desert, hundreds
of miles from the ocean. But we know that these
rocks were actually formed, were part of the seabed two
and a half billion years ago. This is a two and a half
billion year old outcrop. And these banded
iron formations are very important in
terms of telling us what the ancient ocean
was like, and how life may have come to develop on Earth. And so banded iron
formations have-- this is a closeup here of one. And they have these
striated appearances. Where you see these very dark
red bands, that's hematite, a very iron-rich
mineral, interlayered with these chert layers,
which could be clays, muds, that developed. So you see a very
distinct pattern here. And as a scientist, that's
a very interesting thing. Whenever we see a
pattern, we think there must be some sort of
cause-and-effect relationship. Something was going on. There was some kind of
cycle, perhaps, going on here that could tell
us a lot about what the ancient Earth was like. And so we go to these banded
iron formations to study these. And these are not
small features. This is a picture of
an iron mine in Brazil. So banded iron formations
can be hundreds or thousands of feet thick. They can cover tens or
hundreds of square miles. These were enormous
events in Earth's history, when these iron
formations were laid down. And it's also
important to point out, this is where we get the
iron to produce steel. And because these are very
highly concentrated ores, steel is very cheap. We can thank this, really,
for modern civilization in some respects. So this timeline is going to
be a central theme of my talk for the ancient oceans. So we're starting here over on
the right side of the x-axis one billion years ago,
and then going back to four billion years
in Earth's history. And on the top panel
here, I'm showing what geologists have found
as the major episodes of banded iron, or BIF
deposition in Earth's history. So these are regions where we've
seen large BIF developments. And this tells us something
about the ocean chemistry here in the middle panel. And it also tells us something
about what the oxygen levels were like on early Earth. And the reason for
that is because to get this deposition of
these iron deposits, there must have been
ferrous iron in the ocean. So ferrous iron is soluble. But it reacts very
quickly with oxygen, and precipitates as something
like a banded iron formation. So in other words,
to get these types of formations there must
have been very low oxygen. And We believe those
oxygen levels were a fraction of a
percent of what we have today in the atmosphere. As we move forward
in time, there was what we refer to
as this great oxidation event, where at
least the surface ocean became oxygenated. That would have
reacted with the iron, precipitated some of it out. But then, most of the
iron would have probably been down in the deeper
sediments, not so reactive. And then there was
also this period. There was a lot of
sulfide being developed. Now the ocean is
very sulfate rich. In our modern ocean, we have
a lot of sulfate in the ocean. And the chemistry between iron
and sulfur is very interesting. You could actually have somebody
who is a sulfur geochemist or microbiologist talk,
and give a similar talk that would use sulfur as a proxy
for these ancient environments. But anyway, I'm going to
come back to this timeline, and use this kind of as a
theme for talking about how these banded iron
formations formed, and what that could tell us
about the different forms of life. So the first group-- and
since I'm a microbiologist, I have a very microbiological
slant on this particular topic. There are chemists who
have different views-- that maybe there
was more chemistry, abiotic reactions going on. But I'm taking a very
microbialcentric point view. And the first group of organisms
I'm going to talk about are these bacteria that can
grow in the absence of oxygen, and carry out photosynthesis. It's called "anoxygenic
photosynthesis." And there's this process
here called photoferrotrophy, where these organisms can
take light and react with iron to extract chemical
energy, that they can use then used to fix
carbon dioxide to make cells. And the result of that is rust. Iron oxides precipitate
out as a rusty material. So this is a culture that was
isolated about 25 years ago, and it's growing in light. And it's using iron. And when you inoculate it,
you see the culture tubes turn rusty. So there's no oxygen in here. If this was just a
fully oxygenated tube, the iron that was in here
would oxidize very quickly just by itself. But there's no oxygen, so
the only way this can happen is by the bacteria
catalyzing this reaction. This slide on the right here
shows one of these bacteria. The white arrow there points
to the bacterial cell. And it's incrusted or
coated with these iron oxide particulates around it. And one thing you
note here, there's one little cell and
a lot of iron oxide. And that's a characteristic of
any microbe that oxidizes iron. It's actually quite
a poor energy source, so you have to oxidize a lot
of iron to make a living. So how could this
process have worked? This is a cartoon
from a colleague of mine, Ruth Blake at Yale. And this is the role for
these photoferrotrophs. So again, you have an ancient
ocean here, no oxygen, and these organisms
growing in the sunlight, oxidizing the iron which
forms these iron oxides. These rain down to
the ocean floor, and ultimately,
some of them end up being moved onto the continents,
and forming those banded iron formations through
geological processes. So another important thing
to point out-- the point that Ruth was making
with this slide-- is that not only do you
precipitate these iron oxides, but we know that
iron oxides are very reactive with a lot
of other elements, particularly phosphorous. So they can bind a
lot of phosphorus, and that's shown here. And what would happen
is that iron oxide was raining out of the ocean. It was taking the
phosphorus out of the ocean. Now, phosphorous is another
very important nutrient for all of life. So perhaps, as that phosphorus
was stripped out of the ocean, that reduced the ability
of organisms to grow. And maybe you had
cessations in this process, and then the
phosphorus gradually built up again and
allowed the organisms to start working again. That's one possibility. That's one possible
explanation for these bands that we see in the
banded iron formations. So I'm going to come back
to the timeline again here. So I talked a little bit
about these photoferrotrophs, which may have played a
significant role, certainly from before the great
oxidation event, and definitely back in this
three and a half billion year time period, where
we see these banded iron formations, when we
know there was virtually no oxygen in the atmosphere. But what about this
great oxidation event? What happened here? So what happened here
was the cyanobacteria. And this is an image that
my colleague, Pete Countway at Bigelow, provided to me. This is a picture
of a cyanobacteria. And Pete actually did
a number of the images that you see of the tiny
giants on the wall here. He's a terrific oceanographer
as well as microscopist. And so this these
organisms grow. This is a colonial type
of these organisms. And they typically either
grow as single cells or sort of as these
microcolonies. And you can see the
very green color is due to the chlorophyll
these bacteria have developed. And so this was the evolution
of the first oxygenic photosynthesizing organisms. So these were the organisms
that we believe really provided the first source
of oxygen to the planet. So this was probably
the most important evolutionary adaptation
that we know of. So that's what these
organisms do, is they take carbon dioxide, and they
split water-- use light energy to split water. And then they, again,
produce their autotrophs. So they make their cell biomass. But the byproduct
of this process is oxygen. So at
this point, you could have oxygen in the Earth's
ocean start developing. So this picture here
is a cyanobacterial mat in Guerrero Negro in the
Baja Peninsula of California. This is considered sort
of a potential analog for the early
Earth, where you had shallow seas with these
mats forming on the ocean floor or the sediment. And the reason Guerrero Negro
is special-- it's actually quite salty there. It's near a saltworks. It's too salty
for macroorganisms to live-- snails, shrimp--
anything that would normally be grazing on these mats. So there's no grazing here. So these mats can develop in
ways that potentially they could have two billion
years ago when there were no macroorganisms around. And this is just a closeup
of one of these mats. The top layer here is
these cyanobacteria producing oxygen.
But then below it, you have all these
other layers, which are a lot of these anoxygenic
photosynthetic organisms-- these purple bacteria that I
showed in the earlier slide. So you have very
complex communities that were developing. So now we have the cyanobacteria
that started producing oxygen. And we believe the
current information for when life
originated on Earth keeps getting pushed back. And it's now pushed back
almost to four billion years. There's chemical evidence
for organic molecules that could have been derived
from living organisms as long as four billion years ago. We think that the cyanobacteria
evolved somewhere between 3 and 3.5 billion years ago,
although that may change in the next paper in Science. You never know. But at any rate, certainly
within this period, we believe that there
were these cyanobacteria. And so they were starting
to provide oxygen, and potentially providing these
oases of maybe local areas where there was quite
a lot of oxygen. And it doesn't show up
too well on this slide, but I'm showing these
little peaks here, where what we refer to
as "whiffs" of oxygen could have been in the
atmosphere and in the ocean. And so this could have
combined with iron, and started helping to
precipitate these banded iron formations. But there's also a
microbial role here, too. And I'm going to
talk about that now. Because that's really
what I work on, is a group of organisms that can
oxidize iron using oxygen, and use the energy they get
from that oxidation to grow. This is an image of
a hydrothermal vent. It's a diffuse flow vent. It's at Loihi Seamount about
1,000 meters below the surface. So what we have here is
a vent fluid coming out with a lot of iron
in it, flowing over this rock surface-- you see
all this rusty material here-- and a little bit of oxygen.
This is an interesting site, because it's an
oxygen minima zone, so there's only a
few micro molar. This is about a
tenth of a percent of what is in our atmosphere. So who grows here? So this is an organism called
Mariprofundus ferrooxydans, which I isolated
about 20 years ago. And this was the first
iron oxidizing bacteria isolated from the
marine environment-- a very interesting organism. This is the cell here. And so it it's oxidizing
iron, and producing this stalk material, which is composed
almost entirely of these iron oxides. And so this is the member of
a new class of proteobacteria called Zetaproteobacteria. They're very common in these
high iron environments. Hopefully, this movie
plays-- maybe not. Anyway, this was a movie
of time lapse images showing this bacterium growing. And as it grows, it forms
this stalk material, and makes this very
characteristic helical stalk. So just to show how
these organisms work, this is a process we call
chemolithoautotrophy. I expect you all to
remember that word. So these organisms,
again, they oxidize ferrous iron to this ferric
iron, which immediately precipitates as iron
oxide that they produce, and produce this stalk. They're able to take up
CO2, so their autotrophs. They can also fix nitrogen.
So they can pretty much do everything they
need to survive. And so could they have
played a significant role in forming these banded
iron formations when there was trace amounts
of oxygen present? And that's one of the
questions that we're definitely interested in. And to dig deeper
into that, this is a picture of
an intact iron mat that we brought up
from the ocean floor. So it's only about a
centimeter-- half an inch, maybe to an inch thick. I'll show a picture in
a minute, but these mats can get much more
extensive than that. But the top image here
is just the intact mat. And then what we've
done is sectioned it. And you can see, it has this
very fibrous appearance. And then as we focus in
with more and more powerful microscopes-- this is a scanning
electron micrograph here of one of these sections
of this mat-- you can see it's all this fibrous
material is those stalks that were produced by this organism,
this Mariprofundus-like organism that I described
earlier-- so amazing ability to carry out a lot
of iron oxidation. As a microbiologist, we're
very interested in the fact that these things all grow
in the same direction. We're trying to figure
out what's up with that. And there's a
whole other groups. There's a whole village of these
iron-oxidizing bacteria that live in these mats, that have
various different morphologies, which are very
characteristic of biology. You can't form these
types of structures without biology being
present, in the presence of these iron-oxidizing
bacteria. And just to bring
home the fact, these are not necessarily very
localized or very small features on the ocean floor. This is a place we call
The Golden Tower, which we found about two
years ago in the Mariana in the southwestern Pacific. And this is a meter here. When we first saw this
from the submersible, we thought it was an extinct
hydrothermal vent chimney. But we went up and started
really investigating it, poking it, we realized it was
constructed almost entirely of these microorganisms. We could stick the
temperature probe of Jason, the submersible, right
through this thing. We could have driven
Jason right through it. We didn't do that, fortunately. So the point is,
these organisms can form these really
interesting biofabrics, these mat-like structures here. And we can see these
in the fossil record. Again, because it's
a mineral structure, it's quite resilient if it gets
preserved in the right way. So this is a 300 million year
old hydrothermal vent sample. And you can see very
clearly these distinct sort of helical stalk-like
structures in this. Now we're going back in
the right picture here. We're going back
1.7 billion years old to these
filaments, which I also would believe could very
well be the remnants of ancient
iron-oxidizing bacteria. So this brings me back
to the timeline again. And so could these aerobic
iron-oxidizing bacteria have played a significant role
in this banded iron formation? And I would contend certainly,
at 1.7 billion years, we have pretty good
evidence that they were present, and
could have played a significant role in forming
these types of iron formations. It's harder when you go further
back in time, to this 2.5 to 3 billion year period
here, to find really well-preserved rocks. And so one of our goals
in scientific research is to try to find places
where we could find actual preserved
evidence for these, or other biosignatures that
are associated with them. So I'm going to finish
up here, with this slide of the very modern ocean. This picture was given to
me by Catherine Mitchell, a post-doc at Bigelow
who studies ocean color. And so this is a picture from,
I think this was [? SEWIS ?], NASA's satellite, going
over the Gulf of Maine about three weeks ago. So here we are in Boston. Bigelow is right up about here. And I'll just let you
contemplate the beauty of what the modern ocean looks
like, and how fortunate we are to have it. And with that, I will also
thank sources of funding for this, that support my work
and a lot of the work that I've described, which, of
course, is the work of a lot of geologists,
earth scientists. But the National Science
Foundation and NASA are the two major supporters
of that work, and a number of colleagues, of
course, including Pete Girguis from Harvard,
who I collaborate with. So thank you. [APPLAUSE] Thank you, David. So we'll move on to
the second presentation from Pete Girguis,
who is Professor of Organismic and Evolutionary
Biology here in Harvard. Thanks for coming, Peter. [APPLAUSE] Good morning, everyone. It is my pleasure
to be here today. Thank you to Liz Cohen and all
the organizers, and John Huth, for the invitation. This is a fantastic symposium. And I'm just as excited as
the rest of you to be here, and to see what some of these
amazing speakers who are coming up are going to share with us. Dave and I, as Dave
mentioned, were tasked with the
job of summarizing three billion years of life. This is a task I think
best left to the gods, for certainly she or he
would do better than I. But I will do my best. And thinking about what
Dave was presenting, who we sort of colluded
in this effort, decided that I wanted to
share with you a perspective on the evolution of
animals in our ocean, and to move from the past up to
today with the idea of giving you a sense of what
these animals look like to those of us who consider
ourselves physiologists. That is, what do the animals
in Earth's past look like? What do the animals in our
modern ocean look like? And what can that tell us
about our changing world, and how these anthropogenically
induced changes may shift the kind of diversity
we see in our ocean? So I'll start with the
evolution of animals. And by animals, I
mean organisms that have sort of complex shapes. This is not the same
as the evolution of life, which Dave gave
you a very nice overview of. But these are the
kinds of things that we might look at and
recognize as being animals. I'm going to start our
conversation about 600 million years ago, in a
period in Earth's history where, as Dave
mentioned, we started getting these whiffs of
oxygen. And we started seeing, in the fossil record, evidence
for soft-bodied organisms that evolved in
this period of time. These early marine animals came
in a variety of amazing shapes. And for those of us who think
about life in a lower oxygen ocean-- as was likely the
case 600 million years ago-- these shapes likely play a
role in conferring function. That is, for an organism that's
relatively simple in terms of its tissues-- meaning it
doesn't have lungs, and gills, and all these sort
of fancy apparati to help get gases out
of your environment-- being thin, and having a
lot of ripples, or ruffles, or things of the sort, increases
what we call your surface area. And it helps them take
up the dissolved gases. And you can see that. You can see that in many of
the shapes of these organisms that we recover from
the fossil record. There is a debate
as to whether or not these organisms are related
to today's modern organisms. But for the sake of
this presentation, and for the sake
of our dialogue, I would just point out that
in this lower oxygen ocean, we have plenty of animal
or animal-like creatures that have shapes that tell
us something about how they may have access to oxygen. Now, a little later on,
coral reefs began to appear. And these are the
kind of corals that we think of today-- these sort of
large, reef-forming organisms. Believe it or not, they
bear a striking resemblance to many of the
reefs we see today. And then if you continue
moving forward in time, at about 400 million
years ago, we start to see the
first jawed fishes. This is a fish
called a Placoderm. It doesn't have scales in the
way you think of a fish having scales, but it had
the predecessor to scales-- that is,
these kind of bony plates that acted as armor
for this fish. Now, these and many
other organisms have continued to evolve
into the diversity of life we see in our ocean today. And so when we go to
something like a coral reef, we see echoes of
these organisms, whether they were
the frilly sort of invertebrate-like organisms
we saw back in the [INAUDIBLE], the reefs we saw about
500 million years ago, and of course, the bony
fish that we're all familiar with today. And you can see how
evolution has shaped life to occupy a variety
of niches or habitats, from the near shore
environments where we see beautiful communities
like these sharks and rays, to the darkest depths where
I do most of my research. This is an anglerfish. And actually,
while we're here, I can't resist-- this
is too much fun. I want to take a poll. How many of you
think this is a boy? See a show of hands. How many of you
think it's a girl? I love this. It's a well-informed audience. This is a girl. Her mate is probably
attached back here. Men bite onto females,
and they eventually degenerate into little more than
a pair of reproductive organs and some semblance of
fins, and that's it. So on my lazy
days, this actually sounds pretty appealing. But we'll move on. We have seen communities
evolve around these undersea volcanoes that
occupy our Earth's ocean ridge system. This is some 60,000
kilometers of a mountain range that's peppered with volcanoes. And you should know, 90% of
the volcanic activity on Earth takes place in the ocean. And many unique organisms have
evolved around these sites. I'll tell you about some
of them in a few minutes. But again, in the interest
of sharing some of the wonder that we scientists experience
when we study the ocean, I wanted to show
two short videos. This is, well, you'll
see what this is. But it certainly quickened
the beating of my heart. [VIDEO PLAYBACK] This is an underwater
autonomous vehicle called a REMUS being attacked by
a Great White Shark-- or let's be clear here-- being
interrogated by a Great White Shark. This is the way they
understand their world. So this, for your
information, is on exhibit at the Woods Hole Oceanographic
Museum down in Woods Hole, if you want to go see it. Many of these other organisms
captivate our imagination in other ways. I'm fortunate to be working
closely with the Ocean Exploration Trust. This is founded by Bob Ballard. And it's an institute
solely dedicated to exploration, and outreach,
and engaging the public in ocean science. What you would hear is
a bunch of scientists screaming and yelling about
what you're about to see. As we dive in our ocean, we come
across things we don't expect, in this case a sperm whale-- a
young sperm whale checking out the remotely operated submarine. Can you see it there? It's just swimming underneath. And the scientists
went just berserk. And this, by the way, is
broadcast live in real time. So if any of you are interested,
you can look up Nautilus Live, and you'll be able to join
us on our expeditions. But check this out--
the sperm whale is just as interested
in us as we are in it. And you can see its
mouth, and its fin, and that's its belly
as it swims by. Now, these charismatic
macrofauna-- or megafauna, as we call them-- always
capture our imaginations. But it's important to remember
that today's ocean also harbors a lot of microbes. There are about 10 to the
27th microbes in our ocean. And if each of them
is a micron in length, and you placed them
end on end, they would extend 10 to
the 21st meters. This is 105,000
light years, so that would stretch to the
Milky Way, and would span our galaxy in microbes. And so that is a very
excellent reminder that just because
they are small doesn't mean they are unimportant. And in fact, the microbes
in our world run our planet. And without them, our
biosphere would come to a halt. And so in fact, sometimes
it's easy to forget that the ocean alone
represents about 85% of our planet's habitable space. And so that is every
other environment you think of-- from the
desert, to the tundra, to the upper half mile
of ocean-- all of that fits in the other 15%. So 85% of our planet's
biosphere is deep ocean. That's perpetually
dark, perpetually cold. And so while we tend
to think of that as the extreme environment,
arguably, we're the ones who live in
the extreme environment. And if you took this map,
and used the surface area to represent the
habitable space, it really should look
something like that. But our knowledge of our
oceans and its denizens really is still in its infancy. There's about two million
known animal species. Estimates from the
census of marine life suggest there's likely
18 million more species we have not discovered. If you are brave enough to
include microbes, and try to actually figure out what
a microbial species even is, that puts you up
at near a trillion. And again, these
microbes run our planet. They run our biosphere. And without them, we
wouldn't be able to live, yet we only have less than a
percent of them in culture. So we have a daunting
task ahead of us. And our ignorance about the
ocean, if I can call it that, is based in part on
its inaccessibility. It's a world that's very
different than ours. As I mentioned, on average,
the seawater temperatures are near freezing. Because once you get
into the deep sea, it's chronically cold. It's chronically dark. And this has an influence
on the evolution of life in that environ. And in this chronically
cold, chronically dark world, pressures increase
as you go deeper. And when you're at
the Mariana Trench, you're talking about 14,000 PSI. Those of you who fill
your car tires dutifully, top them off to about 35 PSI. So think about 14,000. This is about the
weight of 50 jumbo jets on any person in this room. And yet, life exists
there, and does just fine. But the ocean is a hostile
work environment for us. And that's what
makes it challenging. And so these organisms
thrive in our oceans through what I
would call a range of evolutionary adaptations. And that's really what I want to
focus on in the remaining time here, is to give you a
sense of what those are, and why it is that we see the
kinds of diversity that we see. So this is a glimpse
into our oceans through the eyes
of a physiologist. But our ocean really isn't one
homogeneous bucket of soup. It is an environment that
has many habitats within it. And starting from
the upper ocean, which is well lit by sunlight,
and a very dynamic and exciting place, as you go
deeper and deeper, and you find fewer and
fewer organisms-- equally interesting, equally
important, fewer in number, but incredible in
diversity, meaning we find organisms that we
don't find anywhere else on Earth, and in great numbers. So the upper ocean or what
we call the photic zone is what most people think
about when I say "ocean." It's a part of our ocean
that, from a physiologist's perspective, is
very energy rich. There's plenty of sunlight. This leads to the growth
of algae, and diatoms, and other organisms that
are the primary producers of our planet. They're the ones who feed
the rest of the animals. And so it's that
availability of energy that allows organisms
to be very active, and provides them with energy
to cope with the temperature changes that occur
over day and night, changes that occur
seasonally, and the like. But as you go deeper
into the ocean, the conditions become more
constant and more stable. That is, you don't see the
kinds of temperature or chemical oscillations that you do. And as a consequence of this
stability-- not only in space, but frankly, over
evolutionary time-- we see this incredible
diversity of organisms arise in the mid-water. For example, this is a
creature called Phronima. Does anybody recognize this? Couple of fans here, yeah. Those of you who are fans
of the Aliens movies, this was the inspiration--
no joke-- for the creature in the Aliens movie. And perhaps the artist
knew that this creature makes a living by killing
jellyfish, called salps. It kills the barrel-shaped ones,
and crawls inside their body, and lives there. That's what it does. This is a fish called
the barreleye spookfish. Anybody want to tell
me what this is? It's its mouth. What are those? Nope, that's its nose. Those are its eyes. It has a translucent
or transparent head, and two large eyes that
rotate inside its skull, that allow it to look upwards
and then forward. It's a really,
really wild critter. As we go deeper and
deeper into the ocean, we start to see
similarly wild organisms. We start to see things happening
that we still don't understand. For reasons that are unclear,
some organisms in the deep sea grow to incredibly large
size, like this amphipod, or a little beach hopper. And so their cousins, if
you will, on the beach are about this big. And they probably
irritate you when you're sitting there on the beach. In the bottom of
the Mariana Trench, this is how big they get. We see sea cucumbers that
have evolved to swim. This snail fish--
that is a new species. And there are
parts of our ocean, in fact, that have
always had, or rather that have low oxygen over time. They're sort of chronically low
in oxygen-- so-called oxygen minimum zones. And these are very
interesting, because as we start to see changes
to our climate, we start to see some
of these expanding. But I want to talk
to you about some of the denizens of this
zone, and I'll come back to why they're important later. But this is an area
with very little oxygen, and yet we see a diversity of
organisms that have evolved to cope with that low oxygen. We see these large sponges,
that we see on the sea floor. The famous vampire squid has a
blood protein that binds oxygen with incredibly high affinity. That means when it
comes into contact with a little bit of
oxygen in seawater, it can pull it out, and
provide it to the animal. Same with this organism
called gnathophausia, which is a kind of mysid shrimp. Organisms in the deep-- when
we get to the soft bottom sediments, many of them
have similar adaptations to low oxygen. We see
that a lot of them have symbionts
that can help them cope with sulfide,
that Dave mentioned, that may be produced
in sediments. There are also some
really neat morphological adaptations, like
this sea pen here that puts its stalk
in the sediment, puts its fronds upwards to get
oxygen and to filterfeed food. And this is just
one of my favorite. I just have to show
you the tripod fish. The pectoral fins have
turned into stands, so it's like a
little camera tripod. And its pectoral fins actually
are like two big baskets, and it puts its face
into the current, and it grabs food
as it comes by. But I have a soft
spot in my heart for the hydrothermal vents. These are the most extreme
environments on our planet, without question. Because of the pressure
found in the deep ocean, the water does not boil. And as a consequence,
the water temperature can reach 450 degrees Celsius. That's hotter than your
oven in self-clean mode. And yet, we see a
tremendous amount of life living around events--
not in the 400 degree waters. They actually live in the sort
of bathtub kind of temperature waters that you see. But this is a tremendous
amount of life that's based on chemical energy. The microbes that live
in vents will carry out processes similar to what
Dave shared with you. But instead of just
being iron, many of them are oxidizing compounds
like hydrogen sulfide-- that rotten egg smell
that comes out of a sewer. Or they're getting
energy from methane. And we all know there's
plenty of energy in methane, if you've ever used a
gas grill or a barbecue. So these microbes have
evolved the capacity to harness energy
from these chemicals, and feed themselves
and their host. And so vents are
tremendously diverse, and harbor animals that are
some of the most tolerant on earth, including
these worms that are the most thermotolerant
animals that we know of. They can withstand the highest
temperatures, chronically, of about 55 degrees Celsius
or 120-ish or so Fahrenheit. Now, all these marine animals
have evolved morphological, physiological, and
biochemical capacities that enable them to thrive in
their particular environment. This is true whether
we're talking 600 million years ago or today. And that includes variations
in oxygen, or carbon dioxide, or temperature, or
pH-- many of the things that we're worried about
in our changing world. There are marine organisms
that have evolved naturally to cope with those. You can see that some of
these marine organisms from [INAUDIBLE] look
a lot like the sea pens we have today, that again,
have these very frilly body plans to help them take
up oxygen and to feed. We know that some animals
have evolved unique features in their guts to host
certain kinds of microbes. In fact, this is a
study that I worked on with Dave Emerson looking at
the gut microbes of the North Atlantic right
whale to understand how they get their nutrition. And there are many other
biochemical attributes that have evolved, like
these two worms at the vents. They have a
hemoglobin-- actually, surprisingly similar to
yours and mine-- that can bind oxygen and bind sulfide. Even the mussels
that you would enjoy in a nice chioppino--
they are very tolerant to
environmental changes because of where they live. They can cope with
changes in temperature, and pH, and the like. So basically, look--
our oceans have and will continue to evolve. This will continue to happen,
whether we want it to or not. And they'll continue to
evolve-- I love this comic. I should just end it here. But they'll continue to evolve
whether you talk about oxygen, temperature, pH, and the like. But here's the
punchline-- as we think about the evolution of
animals over the last 600 million years, it's important
to remember the rate of change. And most organisms
today are really not well poised to respond to
the rapid pace of change in our environment. And so the question
in some ways is that we know that
humankind is always going to have an impact on our ocean. The question is
really not, are we going to kill all ocean life? Because short of complete
nuclear holocaust, our activities are not likely
to bring our ocean to a halt. But the question is, what kind
of an ocean will we create? And so when we think about
the diversity of organisms that exist in our
ocean, bear in mind that as we see these
changes occurring, we will start to see things like
the increase in lobsters that was mentioned
earlier, and changes in our mid-water and
deep ocean community. And we have to recognize
that those changes come with an intrinsic and
an extrinsic loss, meaning that we're going to
lose natural biodiversity, but we may also
impact species that are important to
our own well-being. So with that, I'd like to
thank you for your time, and appreciate your attention. [APPLAUSE] Well, thank you very much. Yeah, that's working. So that's been a great
introduction to the day. As you see, we've been looking
at early life-- really, the early life from
three, three and a half billion years ago
from Dave, and we've been looking at the
evolution of animals, in particular from 500 million
years or so ago from Pete. So thank you for those
two great presentations. But we do have a gap in
between-- so between three billion years ago and 500
million years ago, we've got about two and a
half billion years. Presumably, things
happened during that time. So perhaps the two
of you would like to mention a few
things about what we know about how life
evolved during that time, and how the evolution of
oxygenic photosynthesis three billion years ago
ultimately permitted the evolution of animal
life 500 million years ago. I think you're the right
person for the job, Chris. Want to give it a go? Do you want me to start? Yeah. By all means. Yeah, [INAUDIBLE] The expert's right here. That was not my intention. Well, you're up here. Yeah, I didn't
prepare an answer. I just prepared the question. So certainly one thing, we know
that oxygenic photosynthesis evolved as we saw this morning. And that subsequent to that,
respiration sort of evolved. And respiration is
photosynthesis in reverse. So rather than consuming
CO2 and generating oxygen, respiration is consuming
oxygen and generating CO2. So this happened at some point. And then subsequent
to that, there was the evolution of
the eukaryotes, what Dave talked about
with the prokaryotes-- the primitive bacteria
and Archaea organisms. Subsequently to those,
we had the eukaryotes, which are more complex
cells-- the sorts of cells that we have, where
we have respiration happening inside mitochondria,
which used to be bacteria that we acquired. And the photosynthetic
organisms took the cyanobacteria inside the cells, and
generated the chloroplasts, which power photosynthesis now. So we had the evolution of
the eukaryotic organisms-- unicellular, still. And then I don't really
know too much more. Those may be the evolution
of some fairly primitive multicellular life forms, not
very complex, not very well developed, which then
subsequently gave birth to the incredible explosion
of multi-cellular life in the Cambrian. So I wonder how that happened. I think I had the privilege
of teaching a course a couple of years ago with Andy Knoll. And one of the things
that we really tried to do is step away from
concerning ourselves about the particular organisms
that evolved over time, and focus on this sort
of fundamental question. And I think Chris, you
set this up really well, in that as we think about
the evolution of life and the evolution of the
eucaryotes-- actually, let's go back to respiration. Once we start to see the
evolution of eukaryotes that have in them what was likely
a bacteria that now came inside another
cell, and you have a cell with this
mitochondria, which are your power
plants in your body, you have an organism
that's carrying out aerobic respiration. And from the physiologist's
point of view, one thing that's
neat to think about is how much energy you get
from different substrates that you might use. And so Dave talked a lot
about iron oxidizers. And if you start
looking at the energy yield you can get from oxidizing
iron with oxygen, or nitrate, or something else, you
get a certain amount of energy per mole. Or think of it as
like how much energy do you get from eating a dozen
eggs versus a dozen celery sticks? The eggs are going to have
a lot more energy per unit. And when we think about
energy metabolism, respiration is an incredible
way to get a lot of energy per unit substrate. And this opens up a
lot of possibilities. And it's, I would argue,
one of the factors why we see the evolution
of multicellularity. The punchline, in a way,
comes down to this-- that all of the diversity of
animal life you see on Earth is based to a lesser extent
on the differences in energy metabolism. Because how you make your energy
is frankly, not that different than a goldfish, or a leopard,
or a snake, or a lizard. All of those organisms--
we all eat organic matter. I don't mean Whole Foods,
I mean organic matter. And we breathe
oxygen. And that's how we generate our energy. And that's it. You can hold your breath
and do some amount of work for some time, but that's it. Microbes have this tremendous
physiological diversity. Some of them seem to get
energy from oxidizing uranium. I mean, it's out of
control what microbes do. But we organisms, we get
our energy by eating things. And it's led to this
tremendous diversity of morphological adaptations. We see all these kinds of
multicellular life having very different shapes,
and different forms, that capitalizes on our environment. And so I think that
isn't necessarily what happened over
that period of time. But once you get
respiration, and you start to get
eukaryotes, you do start to see this diversification
of multicellularity. Excellent. So maybe I could just add a
little genetic touch to that. So the microbes that Pete
talked about as being incredible abundance, well, that
genetic diversity is also incredibly abundant. And all of our genes
are somehow derived from a microbial ancestor,
and the gene for using oxygen. Pete and I are looking
at trying to-- one of the things we're interested
in is trying to measure how low a microbe can go in terms of its
ability to respire on oxygen. But it was the development
of those processes, and that genetic
adaptations, that ultimately led to multicellular life. And I think that's
a great question, is can we see those ancestral
gene exchange events, even, to try to
track that process. We'll perhaps take some
questions from the floor. So if you want to go to the
mike and start lining up. And maybe while
you get organized, perhaps I'll ask another quick
question for the two of you. You did talk about--
in particular Dave, you talked about-- the
generation of oxygen, and how that has
influenced the Earth. But neither of you
talked too much about climate and the
connection between life on our planet and
changes in climate. So these organisms, in
addition to generating oxygen, they also manipulate carbon
dioxide and methane, which we know are greenhouse gases. So what evidence do we
have that life has actually changed our climate over time? Maybe answer quickly. And then-- Sure. Dave, you want to
give it a shot? Sure. I mean, certainly
methane, obviously, is a microbial process. Most of the methane we
see in natural iron seeps is coming from methanogens. That was presumably a very
ancient group of organisms. I mean, they're very
oxygen sensitive, so they die in the
presence of oxygen. So that development of
methanogenesis and the methane production was certainly-- I
mean that might alone, as well as-- well, and then
also CO2 fixation, which we also didn't talk about. The other major innovation
besides photosynthesis was the development of RuBisCO,
the enzyme that actually fixes carbon dioxide, and makes
all the biomass we have-- incredibly important in terms
of influencing the atmosphere. So two very quick
thoughts-- so one is, we should not
assume that our world is an aerobic world alone. There are plenty of anaerobic
environments in our world. And as Dave said, we're
very interested in the role that microbes play
in methane cycling. But there are also big
questions about the role they play in carbon
cycling, and just what's the fate of carbon that
gets buried, and the like. I know Professor Ann
Pearson is in the audience. And her lab studies
quite a bit of that. So it's really
vastly complicated. I guess that's a
good way to end. OK, so please go ahead. If you introduce yourself, and
then ask your question, please. My name is Adam Sachs. I'm with an organization called
Biodiversity for a Livable Climate. And I have a question
for Dr. Emerson. On your first two slides,
at four and a half billion years ago, we had a
very hot and inhospitable place. And on a given date-- say
June 4th, because that's my birthday-- in advance
of my birthday, in the year four billion BCE, the
Earth suddenly turned blue. Where did that water come from? Great question. So I looked into
this a little bit, because of course, this didn't
happen just on your birthday, unless you're a few
hundred million years old. But where the water came from--
so we believe a lot of it came from asteroids and
meteorites hitting the Earth. But there's also accumulating
evidence that a lot of it just came from rock
reactions, condensation as the planet condensed to
become a hard, rocky planet, that water was released
from those reactions, too. So people study
isotope ratios, and get into some very detailed
geochemistry, which I don't entirely
understand, I must admit. But it's an interesting
question, actually, as to where that
water came from. And it's a lot of water. But you know that the moon of
Europa, the moon of Jupiter, has an ocean that's twice the
volume of the earth's ocean? But it's under 20
kilometers of ice. So think about that. OK, next question, please. David Jackson,
Radcliffe Institute. Doctor Emerson was alluding
to genetic processes are very important in the
evolution of oceans and things that live in them. I wonder if you
could say something about the role of viruses,
which more and more are being discovered daily in the
oceans, both as agents for genetic exchange, and
as natural selective agents in their own right. You showed the picture of the
microbes strung [INAUDIBLE]. How far do the viruses go? Yeah, exactly, that's probably
another astronomical number. So just to provide
a bit of context-- so viruses can play a
role in moving genes from one organism to another. And one of the challenges we
have in thinking about microbes is that there seems to be
a degree of promiscuity among microbes in their genes. That is, we see genes from one
microbe in another microbe. This is also true
in animals, where we start to see genes in animals
and microbes, and vice versa. And so I think it
is absolutely fair to say that our community's
ongoing studies of viruses, or the so-called
virome, is going to show that they
play a tremendous role in the evolution of microbes
on Earth, and animals as well. And so this, to me, really
challenges our notion of the species concept, which is
robust in the absence of that. But then, if we find out,
for example, that you, sir, are 3% algae-- I'm being
ridiculous-- but then what does that mean? And so a lot of work is being
put into studying viruses, not only in the open
ocean, but actually, in the deep subsurface
biosphere as well, where we know that there are
tremendous communities of microbes, and are trying to
understand the role of viruses in mediating exchange. Just one quick
addition to that-- it's estimated by my colleagues
at Bigelow, some of whom are virologists, that basically,
all these phytoplankton you see on the walls here could
turn over almost every day, just due to virolysis as well. Oh, yeah, right. Just an incredibly important
process in terms of the carbon cycle in the ocean. So don't think of
viruses as just nasty, disease-causing things, but more
like lubricants in the ocean, making sure that the
ecosystem is turning over and gene flow and [INAUDIBLE]. Next question, please. I am Prudence Steiner on the
Radcliffe Institute board. I have perhaps the most
naive question of all. And that is, how
do you define life? And by the way, I'm not
thinking theologically. One of those naive
questions [INAUDIBLE]. Let's dump it on Chris again. Chris? Virus is not considered to be
living organisms, for example. So in our definition of life,
viruses are not in there. So then, they're not in there
because they are not self replicating. They need other
things to replicate. So yeah, once you cross that
border, that a virus isn't life, then where do you go? It's hard. You have to be able
to generate energy. You have to be able to
reproduce, replicate. I'd say those are-- and I
was just at the NASA workshop where we were discussing
some of these issues. And one of the issues that
came up was being able to move, being mobile, being able to
move is another potentially very important thing for life. Because you can move around. And to move, you
can eat in one spot. But if you can't
move somewhere else, then you consume
all your resources. And yet, of course,
we know there are organisms that don't move. I mean, it's a tough one. And this is of great interest
to the astrobiology community, because if we start looking for
life on other planetary bodies, the question is, do you
look for things like DNA? Well, you might not find
the same core molecules. And there may be other metrics
we need to put into place. Thank you. My name is Davidson
[? Reuben, ?] a student at Harvard. I'm curious as to-- this is
directed at Professor Peter Girguis-- given-- I'm not as
courageous as the previous questioner to ask the question. Given that there's not
been as much research as we've explored in
other fields, such just space and terrestrial
planes, what does the data give so far as to
what our oceans might become? As we've previously seen, it's
not going to be eradicated. It's not going to
be annihilated. So would it more favor
aerobic organisms, or will anaerobic organisms
grow in multitude? What would be the effects that
we see from the current data? Thank you. So Davidson's a
students in my class, by the way, so this is
definitely an extra credit point. So in the interest of time,
Davidson, I'll keep it simple, and say that I suspect our
speakers this afternoon are going to touch
upon a lot of that. So we'll let them do
the heavy lifting. But I think it's more
than just the simple idea of, oh, the temperature
might change, or oxygen might be less. Because those all have
subsequent consequences. If temperature changes enough,
and we disrupt the global ocean circulation, that
has huge implications for the distribution of
oxygen and other components. And so I'll leave it to our
speakers this afternoon. But that's the tough part. There is no crystal
ball that we can look into that says, oh,
it's as simple as this. We really don't
know, in my opinion. OK, well, if there's
no more questions, then thanks for your interest. And thanks to a great
starting session. [APPLAUSE] [MUSIC PLAYING]
