What’s Altering Rhode Island’s Nitrogen Cycle?

Written by on May 14, 2014 in Other News, Physical Oceanography
Why is anammox alive and well in the sound but nearly absent in the bay?

Why is anammox alive and well in the sound but nearly absent in the bay? Photo credit: Mike Cohea, Brown University.

A specific process in Earth’s nitrogen cycle that was only just discovered, anammox, returns sedimentary nitrogen back to the atmosphere, while contributing to the health of waterways. A new study shows that this process is a major factor in Rhode Island Sound, but is almost completely absent just a little further inland in Narragansett Bay.

The study from Brown University examined the possible reasons for this change and identified differences in marine sediments between the bay and sound as the primary reason. It also raises questions about what may be preventing such an important process in Narragansett Bay.

Anammox (anaerobic ammonium oxidation) is one of two ways that various forms of nitrogen found in seafloor sediments get converted back into its inert form, N2, that composes 80 percent of the atmosphere. This process was only recently discovered and scientists don’t fully understand it yet. They do know, however, that it plays an important role in Earth’s nitrogen cycle and contributes to the health of waterways by removing excess nitrogen that could fertilize harmful algae blooms.

The researchers found that anammox contributed between eight and 42 percent of the N2 produced in the sound, while it produced no more than four percent in the bay. The differences weren’t seasonal and salinity was comparable in both locations. The primary difference was that the sediments of the bay had less oxygen mixed in (and therefore less nitrate) compared to sediments of the sound.

“Past research suggested anammox might be increasing in importance in the bay, but there was not any data to back it up. What we’re showing is it’s barely even there,” corresponding author Jeremy Rich, assistant professor of ecology and evolutionary biology at Brown University, said in a news release. “What’s wrong with the nitrogen cycle in lower Narragansett Bay? Why don’t we have anammox? Have we disturbed it to the point where we are missing this process?”

The findings suggest that Rhode Island’s bay waters lack the proper conditions to return nitrogen from the sea to the atmosphere, but the exact reason why is a question for another study.

To learn more:

Aerial view of the bay.

Aerial view of the bay. Photo credit: Mike Cohea, Brown University.

Copyright © 2014 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of MarineScienceToday.com. She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .

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