Impacts to Freshwater Aquatic Systems | Managing for a Changing Climate


(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.

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