GRETCHEN HOFMANN: As I was growing up,
climate change became such a dominant backdrop
to how to think about the environment.
Things like the Antarctic ozone hole and CO2 emissions
and how it was a greenhouse gas and changing our planet
in terms of warming.
The thing that we're studying most closely right now,
we call it the other CO2 problem.
MACKENZIE ZIPPAY: This morning, we're going to go ahead
and dive right here off the pier,
and we're hoping just to do a beach dive
and collect 10 or 15 red sea urchins that we're
hoping to be able to bring back to the lab to do some ocean
acidification experiments.
GRETCHEN HOFMANN: What's going on with ocean acidification
is that up until now, the world's ocean has absorbed
something like a third of the CO2 that
was released since the Industrial Revolution,
and that's a lot.
Now there's CO2 dissolved into the surface waters of the ocean
and literally alters the pH.
So now what we're seeing is a little bit alarming,
because the pH of the ocean could change very rapidly.
And we're not really sure that organisms have enough time
to adapt to these rapid changes in ocean chemistry.
MACKENZIE ZIPPAY: We collected two species of sea urchins.
This is Strongylocentrotus purpuratus, also known
as the purple sea urchin, and this one here
is the red urchin, which is Strongylocentrotus
franciscanus.
NANN FANGUE: As the oceans become more acidic,
the carbonate levels are going to change such
that they may affect organisms that rely on calcium carbonate
to form their skeletons, like sea urchins.
MACKENZIE ZIPPAY: For example, the adults
here, you can see that the spines are made out
of carbonate, the test, which is the exoskeleton structure,
and then even on their oral end, which is-- this is their mouth,
the teeth are made out of carbonate structures as well.
GRETCHEN HOFMANN: The way CO2 affects
the ability of marine calcifiers to make their skeletons is
that the CO2 dissolves into the ocean, changes
the chemistry so that literally there are fewer carbonate
ions around.
And the carbonate ions you can kind of
think as like the building blocks for their skeleton.
If they can't get those out of the ocean,
they're not going to be able to build their skeleton as
effectively.
And it is this connection, the CO2
to the pH reducing the availability of carbonate ion,
that makes it so difficult for them to make their skeletons.
The goal of our research is to understand
whether marine calcifiers like sea urchins
will be able to make their hard parts,
will they be able to make their skeletons, in the oceans
that we know are coming.
All we do is mix gas, bubble it into our larval cultures,
change the pH of the water by bubbling in CO2,
and basically make future oceans right in our tanks down here.
Then we ask the larvae to try to develop in them
and show us what they got.
What we're discovering is that the larvae develop, so they're
able to make their calcium carbonate skeleton,
but that skeleton is shorter, and they're just
basically a little bit stumpier than they would
be if they grew up normally.
It's really hard to see these subtle differences
when they're swimming and moving under the scope,
so we collect thousands of images
of lots of different individual larvae,
and we do measurements on all their little hard parts.
And most of the metrics are shrinking by about 10% to 15%.
So what we think this says for sea urchins in general
is that although the larvae are able to make
their little skeletons, this seems to come at a cost.
An embryo only has so much energy to do its development,
and one of the things we're learning
is that they're becoming much more
sensitive to high temperature.
We've got an acidifying ocean, and we've also
got an ocean that's warming.
When we think about the ecology of this in a climate change
context, what you end up with is sort of an ecosystem that's
out of whack.
It's out of balance.
If we don't change the technology
that we use right now, and we continue
to emit CO2 at the level that we're doing so,
we're looking at an ocean that is much more acidic.
We're looking at an ocean that has fewer organisms in it.
And we're looking at a planet that will be completely changed
in our lifetime.