Using oyster shells to decrease acidic seawater

6 days ago
With funding from Oregon Sea Grant, researchers from Oregon State University are placing bags of oysters on different amounts of empty shells to see if the ...

English subtitle

So with ocean acidification,
you get some harm
that can come to the oysters.
They don't grow as
well, especially
in their juvenile stage.
That can cause massive
mortality rates.
This Oregon Sea
Grant-funded research
is essentially
looking at analyzing
whether implementing
shell bags will improve
the health of the oysters.
In water, those shells will
dissolve slowly over time.
That releases calcium
and carbonate.
And so that carbonate
essentially buffers the water.
And it allows the shells
to grow a little better.
The shells are essentially
acting a little bit
like an antacid in your stomach.
You know, you take a
Tums or put Alka-Seltzer
in a glass of water.
And what does it do?
It fizzes in your stomach.
It, you know,
counteracts that acid.
And so that's kind of what
these shells are doing.
So approximately
one year ago, we
took those oysters
from the hatchery
and then put them on varying
amounts of empty shell
to examine whether or not the
growth rates would be different
depending on how much
shell material was there.
So these are dead oyster shells.
So they're just shells --
no meat.
They're not alive.
So we've got essentially three
stacks high, two stacks high,
and one stack high of the bags.
And so we want to know how many
shell bags do we really need
to get enough of a
buffering effect --
enough dissolution as
that acidified water
comes into the bay.
How much is enough to actually
buffer these bags because,
economically, you have
to pay to get these bags.
You know, how many
do you actually
need in order to make it
enough to actually work?
More oysters means
more dissolution,
which means more buffering.
But if you get enough
buffering from two bags
high as opposed to
three bags high,
you're going to choose
the two bags high.
So we're trying to figure
out which one actually
works the best.
Over the past year, Sophie and
the rest of the research team
has been staining the
oysters with manganese
and a fluorescent
stain, called calcein,
to measure the growth
of the oysters.
The oysters are taken off of
those experimental conditions,
put into buckets,
where the stains
are included or incorporated
into the shell for a few hours.
And then they're
placed back out into
their respective treatments.
And that process, more or
less, happened every two weeks
for a year.
Now we can actually
take a cross section
of the shell, as you
would with a tree ring,
and look at those growth
lines, as they've grown
over time in the past year.
On the screen here,
you can see some
of these fluorescent marks.
Those represent different
points in time--
different sample periods,
where Sophie actually
immersed the oysters as they
were growing and the stain.
And then what Sophie and
Alyssa and Adam are doing
is essentially looking
at what the chemistry was
like during these
periods in the water
and what the chemistry
in the shell was like,
and then seeing if
we can establish
that relationship between them.
So we're going to measure
uranium and calcium
in the oyster shells.
And we're going to use this as
kind of a fingerprint for pH.
So the ratio of
uranium to calcium
will actually
change in the shells
depending on the acidity
of the environment.
We're going to use the
uranium-calcium ratios
to compare between
the treatments
that we have out in the
field, so actually see
if those bags of shells
are effectively buffering
against local acidity.
But we want to see is whether
or not we've actually changed
the chemistry, right?
And so once we developed
this calibration,
or this relationship between the
shell chemistry and the water
chemistry, then we can see
if we've actually changed
that because of the shells.