Six years ago, I entered into an underwater world
on my first scuba dive.
And what I noticed immediately were so many colors,
tons of new marine life that I had never seen before.
I was able to swim up, down, and around,
and explore this beautiful ecosystem.
And later, I decided I would definitely study this ecosystem
in both college and, later, graduate school.
Why were these ecosystems so important in the first place?
Well, they are biodiversity hotspots.
This means that while coral reefs only cover 1% of the ocean,
they support more than 25% of marine life.
The corals build a calcium carbonate skeleton
that provides space for all of the fish.
You can think of corals as the trees of the rainforest
that provide habitat, food, and nursery space.
Coral reefs are spread throughout the tropics,
and so nearly every nation relies on them one way or another.
Coral reefs are also the canaries of the ocean.
Canaries tell miners whether the environment that they're in
is healthy or not.
And so, a healthy coral reef supports a healthy ocean.
Now, why do we care about a healthy ocean?
Well, humans rely on the ocean
for seafood that sustains thousands of coastal communities.
We also rely on the ocean, and coral reefs,
to protect our coasts from erosion,
especially during storms.
And the ocean exchanges compounds with the atmosphere,
which brings us clean air and water.
An interesting fact is that corals
are made up of tiny little polyps,
and these polyps excrete a protective mucus layer.
And this mucus layer helps the coral
gather nutrients and even protects it from different toxins.
So, you can think about it as a living boulder.
You may know that corals have zooxanthellae,
which are tiny algae that live within these polyps.
And this algae exchanges nutrients with the corals
and helps keep the coral healthy.
However, as you see in this graph,
each bar represents temperature around the globe.
And our world is warming,
both on land and on sea.
And this is a sad reality,
because it can disrupt that relationship between the coral and its algae.
Now, imagine being in a bathtub that is boiling water.
You would want to grab the towel and leave right away.
However, corals don't have the ability to move,
like fish and birds do.
They have to stay in their environment.
And corals are even more sensitive to temperature than we are.
The relationship between the algae and the coral
breaks down very quickly.
But luckily, the coral stays alive.
What you see here is white,
but it's not a skeleton just yet.
It's just the tissue that has expelled the algae
that gives the coral its color.
Once the thermal stress passes,
the coral can recruit back that algae,
and the coral can continue to grow its skeleton
and support a healthy ecosystem.
Now, scientists wondered,
how have these corals been able to stay alive during bleaching?
Well, new technology has shown us that
there are bacteria living inside of these corals,
along with the algae.
So, this is similar to our own guts.
Have you heard of probiotics?
Well, we have bacteria in our guts
that help us break down our food
and produce vitamins that we can't produce ourselves.
And so, this discovery helped us understand
yet another threat that harms coral reef ecosystems.
Typically, the tissue of a coral is uniform in color,
and underwater it even glitters in the sun.
But corals experience disease,
and sick corals are brought to the brink of death.
Unlike bleaching, the coral tissue during disease actually breaks down,
as you see in these images.
There is no chance of the coral tissue growing back
if there are organisms such as algae
that start to take over that blank,
exposed skeleton of the coral.
And this is a major cause of death
and breakdown of coral reefs.
Scientists are still unsure about which bacteria
live inside of the mucus of healthy corals
that support this living ecosystem.
And so I joined UGA as a PhD student
to study coral reef ecosystems.
I was excited for the opportunity
to study the Florida Keys reefs
that I fell in love with six years ago.
At 3 AM, I left with excitement
to see the beautiful ecosystem.
And mind you, I have never been excited
to wake up at 3 o'clock in the morning.
As a graduate student,
I put on my scuba gear,
and I was eager to get in the water to see that same colorful ecosystem
I was expecting.
As soon as I got in, though,
I got a knot in my stomach.
I felt a little bit warm,
and I noticed it wasn't as colorful as I remembered it last time.
In fact, it was a little bit bleak.
There were no fish that I could see, that I saw the last time.
And I noticed that it was mainly flat,
with only a few coral boulders left standing.
I was sad, and I was confused.
Have the corals reached a point of stress
that has no return and has caused this ecosystem
to be so bleak?
The more I swam, the more I noticed different diseases,
discoloration of coral tissue,
tissue loss.
And in action, I was seeing these living boulders
become eroded skeletons.
I remembered the thriving reef that I saw six years ago
that inspired me to go into graduate school.
And in only those six years,
have the corals gotten so stressed
that they are sick and eventually dying?
And if so, if the corals are stressed,
are the bacteria that live in them also stressed?
Sometimes the environment surprises you,
as it did on that day of my first field season.
And as a scientist,
I needed to change my approach.
Instead of studying the healthy bacterial communities
that live inside of the coral
and support a supposedly thriving ecosystem,
I switched my question to ask,
what does the bacterial community look like
when a coral is sick?
You could say I was at the right place at the right time
in that summer of 2017, not too long ago.
Over two days, I collected more than 100 samples
of healthy and sick coral,
in only two reefs that were very close to each other.
But this did allow us to control for environmental variables,
such as space and also time.
That allowed us to compare the bacterial communities
of all of these corals at the same time.
We collected the mucus from several different species of coral,
ten of them to be exact.
And each of these corals independently
had different diseases.
These diseases included dark spots disease, wasting disease,
white plague, and yellow band disease.
So, I started my search for corals,
finding more sick corals than I did healthy corals.
But I also was able to collect my samples.
I used a needle and syringe
to suck up that thin tissue layer
outside of this living boulder that is the coral.
Inside of this mucus that was in my syringe,
I knew that there were thousands of bacteria represented.
And each of these bacteria had different fingerprints,
and that would tell us which type of bacteria they are.
Once I got back into the lab,
I took my syringe samples,
and I applied a technique called amplicon sequencing of bacterial DNA
to find out, what were the fingerprints of each of these corals?
And this would tell me the genus and species, at times,
of the different bacteria in each of my coral samples.
But also, it would tell me how many of these bacteria
were present in each of my coral samples.
We performed an analysis called beta-diversity analysis.
Essentially, we took the coral mucus that was collected,
we took the bacteria inside of that mucus,
we took our fingerprinting technique,
and we came up with a representative value.
This representative value
was a summary value that encompassed
both the types of bacteria present
and their abundance.
This way, we can compare and contrast
the different communities in the different corals.
Now, this figure is a little bit complex, so bear with me.
On the axes, you will notice
they aren't your typical x and y axes.
Instead, these are variation axes.
This means that the farther apart two points are,
the more different the bacterial communities are,
and the closer they are,
the more similar they are.
You will also see that each of the dots
will have a different color.
And these colors represent our different coral species.
Now, I collected three of the same types of coral,
and they're represented by three different dots
of the same color.
So, let's take a look at one dot.
It's a representative value
describing the bacterial community of the coral.
Now, let me show you the entire figure.
We see that those three replicates formed triangles,
and that all of these triangles are intersecting.
The bacterial communities of each coral, therefore,
are similar to each other.
And these are for all healthy corals.
Now, here's a similar figure,
but instead, I've overlaid the diseased coral samples,
which are represented by the different shapes.
We have our dark spot, wasting, white plague,
and yellow band diseases.
And again, they're represented by different colors,
which are our coral species.
Our axes are still variation axes,
and so they're going to tell us how similar or different
the communities are from each other.
Let's start with just a couple of examples in this figure.
We see three triangles that are three different colors.
They represent the same disease
-- circle, white plague --
and three different species, which are labeled here.
You can see that these triangles
are not intersecting,
and so these communities are very different from each other.
If I show you the rest of the figure,
you will see that this is quite different than the figure I showed you before.
There are more triangles
that are more or less separated from each other.
This means that the bacterial communities of each of these diseased corals
are different from each other.
And even when different species
are infected with the same disease,
they have different bacterial communities.
We can summarize this data
by using Tolstoy's Anna Karenina novel,
where he states that all happy families are alike,
but each unhappy family is unhappy in their own way.
There is an Anna Karenina hypothesis for animals.
And so, we applied this to the coral bacterial communities,
to say that healthy corals are all alike,
but every sick coral is sick in its own way.
What does this mean?
We have a new perspective to understand coral disease,
which is way more complex and dynamic
than we thought it would be.
And this could lead us to discover
new probiotics that the corals might need
to stay healthy.
And we want them to stay healthy
because 25% of the marine life
is dependent on those corals.
Next, we wanted to quantify the difference
between the different states of health:
sick and healthy.
What we did is we took the numbers of bacteria
that we knew were associated with healthy corals,
and the numbers of bacteria that we knew were associated with diseased corals,
and we counted them up.
We decided to create a dysbiosis ratio.
Here, I'm calling it the coral imbalance ratio.
This ratio took the average abundance of the disease-associated bacteria
divided by the average abundance of the healthy-associated bacteria.
And by taking a log of that,
we were able to create a graph,
where the coral imbalance ratio is on that y-axis.
And we have our healthy, apparent healthy, and sick mucus
on the x-axis.
Now, for the healthy coral mucus,
we would expect that the imbalance of the microbial community
is low,
meaning that the bacterial community is doing
a good job of working together
to keep the coral healthy.
However, for the sick coral, as we saw,
it had a higher imbalance ratio,
meaning that the bacteria were not doing a very good job
of keeping the coral healthy.
Now, to test this imbalance ratio,
we collected samples from apparently healthy coral mucus
that were part of a sick coral colony.
And we tested this ratio,
and found that it fell right in between the healthy and sick coral mucus ratios.
This shows us a transition
between healthy, apparently healthy, and sick corals.
So, the coral disease is truly very dynamic,
and now we have a quantitative way of looking at that.
Now, we do have monitoring efforts
that show us where disease is at,
which species are affected,
what types of disease,
and prevalence.
But this is new.
This is a potential to monitor the actual health state of the coral
and predict when an outbreak might be imminent.
So, my drive back from Florida to Georgia
was truly reflective.
We had caught an outbreak that happened in real time,
and we controlled for space and time
so that we could effectively compare the different communities
of the different bacteria to each other.
But I wanted to do more than just monitor these bacteria.
What can we do?
For sure, we don't know
which probiotics are appropriate for coral disease currently.
But we are stewards of our planet,
and there must be something that we can be doing right now.
We need to do this to protect our fisheries' economies,
and even to have clean water and air
for future generations.
Remember, if a healthy reef means a healthy ocean,
a dying coral reef does mean a dying ocean.
And since coral reefs are throughout the entire tropics,
every nation is affected.
And so, this is a global and complex problem
that we need to work together to fix.
Until scientists find a cure, though,
you can help scientists out.
You could become a scuba diver yourself
to help track the disease progression of these corals.
You could vote for local and national politicians
that are interested and passionate
about the relationship between the environment and people.
You could also educate yourself further,
and discuss and communicate with other people
who might not know about this global problem.
And lastly, you can make your own lifestyle changes,
such as recycling, eating locally,
taking public transportation,
to make a difference in your own footprint.
You have the power to act now.
So, let me ask you -- what are you waiting for?
I hope you learned from this presentation.
Thank you very much.