(gentle music)
>>Hello, I'm Dr. Caryn Vaughn,
Professor in the Department of Biology
at the University of Oklahoma.
I'll be highlighting some of the impacts
of climate change on our freshwater ecosystems.
Most of the Earth's water is in the oceans.
Only 2.5% of water is in fresh water,
and most of this is in glaciers, ice caps, and ground water.
Fresh surface water in our streams,
rivers, marshes, and lakes
makes up only 1.2% of all fresh water.
Yet, this is the water that terrestrial organisms,
fresh water organisms, and humans rely on for survival.
Fresh water provides many important ecosystem services
for humans, including water for drinking and irrigation,
recreation, and economically important fisheries.
Humans are using fresh water faster
than it can be replenished through precipitation.
As a result, water scarcity is a growing problem,
and it varies both geographically and temporally.
Water scarcity can lead to political instability
and human conflict.
Unfortunately as surface temperatures
warm in our changing climate, more water evaporates
from these important sources of fresh water.
This reduction of water adds more stress
to an already stressed system.
Climate change also will lead
to increases in water temperature.
We already know that lakes are warming an average
of .34 degrees Celsius per decade.
This is greater than the warming rate
for either the ocean or the atmosphere.
Changes in water temperature can affect
both the way that organisms function and their distribution.
If air temperatures were to increase
and average of four degrees Celsius,
the thermally appropriate habitat
for economically important cold water species,
such as trout and salmon,
is predicted to climb by 50%.
In addition, warming lakes are leading to increased blooms
of noxious blue-green algae, impacting water quality.
The life processes of many aquatic organisms
depend on temperature.
For example, with increased temperatures,
aquatic insects at the base of the food web
may mature more rapidly and at a smaller size
and reproduce more quickly.
This could result in more food for fish.
However, increased temperatures will also lead to
increased rates of microbial activity
and increased rates of decomposition of organic matter,
which would result in less food for aquatic insects
and ultimately fish.
In both cases, warm water holds less oxygen,
so water quality will be reduced.
Aquatic species at the southern limit
of their geographic range
will face extinction unless they migrate.
The ability to migrate depends on dispersal mode
and available migration corridors.
For example, in the Southern Plains ecoregion,
many riverine species may not be able to migrate northward
because they are restricted to river systems
that flow from west to east.
Climate change will alter seasonal patterns
of precipitation and runoff.
In turn, these changes will lead to altered hydrology.
Many fresh water organisms are adapted
to particular hydrological conditions,
such as the seasonality and frequency
of floods and droughts.
And they time their reproduction around these events.
For example, some fish such as bull trout
lay their eggs in the fall so that they will hatch before
streams are scoured by spring snowmelt.
Earlier snowmelt would destroy these eggs.
In locations where drought conditions
may become more common, there is even more concern
about increased water temperatures.
My research in the rivers of southeast Oklahoma
shows that fresh water mussels are declining
because increased drought leads to shallower water
and thus higher water temperatures
in rivers in the summer.
In fact, we have measured temperatures
over 100 degrees Fahrenheit.
Losses of mussel biomass in species richness
have lead to large losses in ecosystem services
provided by mussels, including biofiltration
and nutrient recycling in storage.
Fresh water ecosystems are already impacted
by overuse of water, land use change,
pollution, and diversion.
Climate change is a new threat.