With all due respect to Dunkin’ Donuts, America really runs on nitrogen. Neither donuts, nor coffee, nor any other form of life or product could exist without tapping into nitrogen’s delicate global cycle. Given how vital the nitrogen cycle is, it’s amazing what we don’t know about it.
Jeremy Rich, newly appointed assistant professor of ecology and evolutionary biology, is trying to get everyone up to speed on this chemical pillar of existence. In one molecular form, nitrogen is in every protein and strand of DNA. In another form it constitutes 80 percent of the atmosphere. Farmers know it is crucial for plant growth, and fishermen know that it feeds unwanted blooms of algae when there is too much of it.
In his research, Rich focuses on the newly discovered but apparently important role in the cycle played by tiny creatures called planktomycetes. The bacteria carry out a process called anaerobic ammonium oxidation or “anammox.” In some places, Rich and other scientists have found, the marine microbes send up to 100 percent of the nitrogen in the environment on its way through the cycle. Rich, who has been a research faculty member at Brown for a few years, has been working to figure out anammox’s contribution at sites around the globe, including Naragansett Bay and the Block Island and Rhode Island Sounds.
Rich has found that the bodies of water, despite their proximity, turn out to be quite different. In the bay anammox accounts for only 5 percent or less of nitrogen cycling, but in the sounds it’s more like 20 to 40 percent. A better understood process called denitrification does the rest.
“We don’t detect anammox very readily in Naragansett Bay,” he said. “We think this has to do with nitrogen availability.”
It’s an interesting scientific question, as well as a potentially important environmental mystery to account for this difference. Anammox depends on a mixing of nitrogen-rich sediments with oxygen. In the sounds, the wriggling of little shrimp-like bugs accomplishes this pretty well. He thinks that same activity is not happening nearly as much in the bay.
Hypothetically, the bay’s environment may have become less hospitable to the wriggling shrimp, creating a deficit of anammox activity, stunting a portion of the nitrogen cycle. Rich is looking into it because denitrification works on a different form of nitrogen than anammox, so nothing picks up the slack for a lack of anammox.
“If there’s no anammox there, there’s less of a sink for this ammonium which could then diffuse into the water column and promote phytoplankton growth,” Rich said.
Rich is also set to begin looking at anammox in an exotic locale with exotic conditions. Next year he’ll join the “9-North” expedition, nine degrees north of the equator along the east pacific rise. It’s a large collaboration with some famous equipment: the ship Atlantis and a new version of its legendary submersible diving craft Alvin, operated by the Woods Hole Oceanagraphic Institute.
By studying the undersea nitrogen cycle at 9-North’s hydrothermal vents, Rich and other scientists hope they’ll observe it under the extremely hot conditions that approximate conditions when life on Earth was just getting its start billions of years ago.
Rich was just getting started in environmental science — and, as it turns out, a vital part of his personal life — when as a University of Wisconsin student he traveled to Oregon as part of a National Science Foundation-sponsored summer program called the Research Experience for Undergraduates.
He not only studied forest ecology but also met Harvard undergraduate Heather Leslie. They married and went on to graduate school together at Oregon State University and then postdoctoral positions at Princeton. They joined the Brown faculty, where they share lab space.
With his new appointment this fall, Rich joins Leslie in another important way: on the tenure track. That will not only help sustain his research but also means that his teaching opportunities will increase. For the first time he’ll get to focus more on teaching undergraduates. He’s developing a new sophomore level course for next spring about “microbes in the environment,” which will explain how the tiny creatures matter to everything from food production to climate change to energy.
As the nitrogen cycle illustrates, one could also claim that America runs on microbes.