Nav: Home

When birds of a feather poop together

May 17, 2017

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.

Lee designed a microcosm experiment to test his hypothesis. He collected water, sediment, and yes, cormorant droppings, and created 14 miniature ecosystems. Each microcosm contained the same amount of water and sediment from the lake. Then Lee added .5 g, 1.0g, and 5.0g of cormorant droppings to the microcosms. Over the next 21 days, he tested samples of the water. Specifically, he was looking to see if the feces affected the amount of nitrogen, phosphorous, and other nutrients in the water.

Lee found that even a small amount of cormorant feces was enough to produce noticeable changes in the nutrient conditions of the water. These could be long lasting: "Furthermore, feces in the water acted as a nutrient source for days," said Lee.

Lee also analyzed both the water and the sediment to document changes to the microbial (bacterial) communities.

While the microbial community of the water was only significantly affected when 5.0g of feces was added, the microbial community of the sediment was impacted by smaller amounts of feces. Based on his findings, Lee can't blame the algal bloom completely on the cormorants. But Lee thinks their feces may have some influence, since chlorophyll concentrations, signaling more algal growth, doubled after adding only 0.5g of feces to the microcosms.

"Our results confirmed the changes in nutrient condition and microbial community in water caused by a small amount of feces," Lee concluded. "Fecal input may adversely affect the condition of the reservoir, bringing about undesirable changes such as algae bloom."

Lee recognizes the limitations of his experiment. "Microcosm experiments give researchers more control over variables normally not possible in the real world. But the results don't fully represent what happens in the real world because the microcosm can't completely mimic the real environment," he explains.

Lee hopes to continue his research. "We want to understand how many birds a waterbody can support before becoming seriously polluted." For Lee, studying the cormorants in the real world means the dirty work continues.
-end-
Read more about Lee's research in Journal of Environmental Quality.

American Society of Agronomy

Related Nitrogen Articles:

Fixing the role of nitrogen in coral bleaching
A unique investigation highlights how excess nitrogen can trigger coral bleaching in the absence of heat stress.
Universities release results on nitrogen footprints
Researchers have developed a large-scale method for calculating the nitrogen footprint of a university in the pursuit of reducing nitrogen pollution, which is linked to a cascade of negative impacts on the environment and human health, such as biodiversity loss, climate change, and smog.
A battery prototype powered by atmospheric nitrogen
As the most abundant gas in Earth's atmosphere, nitrogen has been an attractive option as a source of renewable energy.
Northern lakes respond differently to nitrogen deposition
Nitrogen deposition caused by human activities can lead to an increased phytoplankton production in boreal lakes.
Researchers discover greenhouse bypass for nitrogen
An international team discovers that production of a potent greenhouse gas can be bypassed as soil nitrogen breaks down into unreactive atmospheric N2.
Bacterial mechanism converts nitrogen to greenhouse gas
Cornell University researchers have discovered a biological mechanism that helps convert nitrogen-based fertilizer into nitrous oxide, an ozone-depleting greenhouse gas.
Going against the grain -- nitrogen turns out to be hypersociable!
Nitrogen is everywhere: even in the air there is four times as much of it as oxygen.
Soybean nitrogen breakthrough could help feed the world
Washington State University biologist Mechthild Tegeder has developed a way to dramatically increase the yield and quality of soybeans.
Trading farmland for nitrogen protection
Excess nitrogen from agricultural runoff can enter surface waters with devastating effects.
Measure of age in soil nitrogen could help precision agriculture
What's good for crops is not always good for the environment.

Related Nitrogen Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".