Faith Breeden: Hi. My name is Faith Breeden and I'm
an environmental science student
at the University of Minnesota Duluth
and I'm going to be speaking
today about the variability in
stream temperature and isotope composition
in the Lester River watershed.
As of right now, we don't
really know a lot about the storage and
release of groundwater to streams
around the north shore of Lake Superior,
but this information is
actually really important to understand
how well the stream can
adapt to changes in the environment.
These changes,
they not only affect the streams themselves,
but they affect the organisms that live in it.
For example, trout,
they are a species of fish that we generally
find in colder moving water
because this water can actually
hold more dissolved oxygen,
and trout are a species of
fish that require a lot of oxygen to survive.
If the stream was unable to maintain
the colder temperatures and hold this oxygen,
we could actually see a decrease in trout populations.
When we're talking about a stable stream,
we generally mean a stream that
has fairly consistent temperatures and
isotope compositions of hydrogen and oxygen.
Changes in its temperature and isotopes would
generally tell us that there's a lot of
evaporation happening at these sites.
When there's a lot of evaporation,
we would see heavier isotopes
because evaporative process is going
to lift up the lighter isotopes first
just leaving the heavier isotopes in the streams.
The overall goal of this project was to track the changes
in temperature and isotope composition
in the Lester River watershed.
To do this, we collected water samples from
15 sites in the watershed every other week,
starting back in 2018.
All these samples, they were kept in
glass vials that would sealed with parafilm,
and when they were ready to be analyzed,
we brought them to the large lakes observatory to
get analyzed on
a Picarro cavity-ring down mass spectrometer
for hydrogen oxygen isotopes.
When we got the results back,
we plotted them along the local meteoric water line.
Looking at Figure 2,
it's pretty clear that most of
the points are being plotted below this line.
Essentially, this is telling us that there's a lot of
heavy isotopes and that there's a lot of
evaporation occurring along the watershed.
Even though we're missing
a lot of temperature data from 2018,
you can still see that there is a trend happening
where there are temperature differences
between sites and over the seasons.
Most of the warmer sites were usually
found in the headwaters of the watershed.
But around fall, they
all tend to drop down to the same cool temperature.
In Figure 4,
we also get pretty similar
results to our temperature data.
We're seeing differences in
isotope composition in the summer.
But again, we're seeing that in the fall and spring,
there is more precipitation,
so we're seeing these lighter isotopes.
This is telling us that in the summer,
we are seeing a lot of evaporation occurring.
Overall, we saw a lot of
variation in temperature and
isope signatures in the summer,
but throughout fall and spring,
they remained pretty consistent.
This agrees with our data plotted against
the local meteoric water line that
tells us that there is a lot of evaporation occurring.
All of this data is essentially telling us
that this stream is going to be more
sensitive to air temperature changes
and less likely to support aquatic life.
That is my presentation. A quick thank you to
the University of Minnesota and the URO Program
for letting me do this project,
and also thank you to everyone that
has contributed to collecting data.
Also, especially thank you to
doctor Salli Dymond for
helping me throughout this whole project.
I would not have been able to do this without her.
Thank you for listening.