Nutritious science: Nitrogen and Phosphate's ecological use explained in Stoichiometry lecture

Ian Larsen/Sun Star Reporter
Sept. 17, 2013

Approximately 50 students, teachers and community members attended Jim Elser’s stoichiometry lecture in the Murie Building auditorium on Friday, Sept. 13.

UAF graduate students chose Elser to give his lecture for the Institute of Artic Biology’s Life Science Seminar Series. Elser is a sustainability scientist and Regent’s professor at Arizona State University, he has completed a number of stoichiometry research projects across the world in places like China, Sweden, Norway and Canada.

Stoichiometry is a field of chemistry that looks at the quantity of reactants and products of chemical reactions in soil and organisms. Elser focused his presentation on the biological, economical and political sides of stoichiometry.

The first topic presented in the lecture was the ratios of carbon, nitrogen and phosphorus in the diets of freshwater, salt water and herbivore ecosystems. Elser spent time talking about the nitrogen and phosphorus experiments involving Daphnia, a microorganism favored in experiments due to their clonal ability and genetic makeup. In the experiment, two groups of cloned Daphnia were made to process phosphorus efficiently. One group was then put into a high phosphate environment and the other a normal environment. After the experiment ended, a large majority of the regular group could not sustain themselves, while the group in the high quality of phosphorus thrived.

“I am a big Daphnia nerd,” said Justin Burrows, a UAF graduate student studying plant defensive chemistry. “They are clonal so you can produce large sample sizes on top of removing the variables of genetic differences.”

On top of having a heavy scientific presentation, Elser discussed how stoichiometry affects our own lives. One of these ways is agriculture.

Understanding the use of stoichiometry can help prevent pests such as locusts from destroying crops, by changing the amount of phosphorus yield in crops and pastures, locust populations can be trimmed down due to a bad food supply. The use of phosphorus the world is just as important as oil and it is not something we usually take into consideration, Elser said.

“I thought the impact phosphorus has [in] the world as a whole was interesting,” said Garrett Savoy, a Biology graduate student. “Besides the ecological impact, the possible political impact, I mean, how is the morocco monopoly going to work out?”

Roughly five different countries control 85 percent of the world’s phosphorus, the majority being in Morocco.

According to Elser, the phosphorus cycle has nearly quadrupled since the 1940s and about 23 million metric tons are used in fertilizer per year and at the current rate of consumption it is estimated that we will run out in about 400 years. Just about all food sources need phosphorus, and the affluence of civilizations and the biofuel economy are hurting the phosphorus ecology.

“This is no way to run a biogeochemical cycle,” Elser said.

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