130-year-old brain coral reveals encouraging news for open ocean

What is the effect of nitrogen pollution far out in the open ocean?

Research conducted at Princeton University found less nitrogen pollution in the open ocean off the East Coast of the United States than previously estimated. The researchers evaluated nitrogen levels in the calcium carbonate skeleton of this living brain coral (Diploria labyrinthiformis). Photo courtesy of the researchers
Research conducted at Princeton University found less nitrogen pollution in the open ocean off the East Coast of the United States than previously estimated. The researchers evaluated nitrogen levels in the calcium carbonate skeleton of this living brain coral (Diploria labyrinthiformis). Photo courtesy of the researchers

A 130-year-old brain coral has given the answer, in any event for the North Atlantic Ocean off the East Coast of the United States. By estimating the nitrogen in the coral’s skeleton, a group of specialists driven by Princeton University found essentially less nitrogen contamination than previously estimated.

Scientists took a gander at coral skeleton samples gathered in the open ocean around 620 miles east of the North American landmass close to the island of Bermuda, a region thought to be emphatically affected via airborne nitrogen discharged from U.S. mainland sources, for example, vehicle exhaust and power plants.

They found no evidence that human-made nitrogen was on the rise. Scientists noted varieties in nitrogen that compared to levels anticipated from a characteristic atmosphere wonder called the North Atlantic Oscillation.

The previous study suggested elevated nitrogen pollution in another open ocean site in the South China Sea, coinciding with the dramatic increase in coal production and fertilizer usage in China over the past two decades. In contrast, the results of this new study indicate that U.S. pollution control measures are successfully limiting the amount of human-generated nitrogen emissions that enter the ocean.

Xingchen (Tony) Wang, who conducted the work as part of his doctorate in geosciences at Princeton said, “Our finding has important implications for the future of human nitrogen impact on the North Atlantic Ocean. Largely due to advances in pollution technology, human nitrogen emissions from the U.S. have held steady or even declined in recent decades.”

“If emissions continue at this level, our results imply that the open North Atlantic will remain minimally affected by nitrogen pollution in coming decades.”

When emitted to the atmosphere, fixed nitrogen can influence the ocean far from land. However, the impacts on the ocean are difficult to study because of the challenges involved in making long-term observations in the open ocean.

Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences at Princeton said, “It has long been my dream to use the nitrogen in coral skeletons to reconstruct past environmental changes; thanks to Tony, we are now doing it.”

While studying in the university, Wang had developed a sensitive and precise method to measure the 15N-to-14N ratio using a mass spectrometer, which is like a bathroom scale for weighing molecules.

After collecting the samples, scientists removed a sample of the calcium carbonate skeleton from a living brain coral (Diploria labyrinthiformis) about 10 feet below the surface on Hog Reef, about six miles from the main island. The researchers confirmed that Bermuda’s nitrogen run-off was not a factor at the site by measuring nitrogen levels in plankton floating nearby.

The study is published in the journal Proceedings of the National Academy of Sciences.