Date: May 17, 2017
Source: American Society of
Agronomy
Studying the effects of great
cormorant droppings on water reservoirs is a dirty job, but someone's got to do
it.
At the Maji Agricultural
Reservoir in Wonju, Gangwond-do, South Korea, that someone is Tae Kwon Lee. Lee
regularly jogs around the reservoir. One day he noticed large black birds
completely covering the small island in the lake. The black birds were great
cormorants, a type of large water bird, and the trees on the islet were
completely covered in the birds' feces. As time passed, Lee made another
observation: the lake suffered a severe algal bloom.
Algal blooms deplete oxygen in
lakes, produce toxins, and end up killing aquatic life in the lake. This
sequence of events got Lee wondering: Did the bird feces cause or contribute to
the algal bloom?
The Maji reservoir is an
important water source for local farmers who use the water for their crops in
the summer. Maintaining water quality is important. About five years ago, the
cormorants showed up and now there are 300-500 great cormorants inhabiting the
lake and islet. That's a lot of birds and a lot of bird feces, so it's
important to understand how the bird feces affects the water. The bird
droppings are rich in phosphorus and nitrogen, and when it gets into the water,
it adds those nutrients to the water.
Adding nutrients to an existing
ecosystem can have a cascading effect. "The feces can influence not only
water quality but also whole ecosystems including plants, soil, and other
birds," explains Lee.
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