Trophic StatusIn our motivation page we cited a desire to
return Lake Mendota to its
original trophic status by decreasing the impact created by human
development. In order to do so, we have
suggested creating
an algae farm in the north end of Lake Mendota that would harvest the
algae
created by the excess nutrients of the Yahara River.
In order to understand how such a process
could help return Lake Mendota to its original settings some
information is
needed to gain a better understanding of llakes and their
characteristics. Essentially there are two main types of lakes, olgotrophic (Lake Mendota originally) and eutrophic (Lake Mendota now). Olgotrophic Lakes are characterized by low nutrient content, low algae levels, clear water, and high oxygen content. A visual display of such a lake can be seen below.  Prior to human settling of Wisconsin many of
the state’s glacial lakes
were olgotrophic, but as farming and urban development have increased
so have
the nutrients entering the lakes. As a
result many of the state’s once pristine waters have become eutrophic
lakes. Eutrophic Lakes are characterized
by a high
level of nutrients, large algae blooms, low oxygen content, and poor
water
quality. While eutrophic lakes are
necessary
environments in the scheme of the Earth, they are not the most desired
visually
or recreationally as can be seen in the picture below.
Using this new knowledge of olgotrophic and
eutrophic lakes it is easy
to see how a lake can transition from one to another.
In the case of Lake Mendota, it was once considered
an olgotrophic lake. Early settlers
reported that the bottom of the lake was visible even at its greatest
depths. But due to human activities in the
area,
which has introduced large amounts of phosphorus into the lake, Lake
Mendota is
now classified as a eutrophic lake. As
an eutrophic lake, Lake Mendota has struggled with aspects such as
water
quality and clarity and there is now growing concerns in regards to the
blue-green
algae blooms that can be harmful to humans. If an algae farm is created as proposed the
hope is to reduce the
overall amounts of algae in the lake and reduce phosphorus levels by
consuming it
in the production of algae used for biodiesel. This
in turn could reduce the over nutrients in the Yahara
lakes and
hopefully begin a process of returning them to their original settings.
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