First Author

The oceans' plants need nitrogen for their growth. So oceanographers are interested in how the levels of this element in the oceans change over time, how they vary in different environments, and how nitrogen interacts with other elements. Nitrogen fixation incorporates the element into compounds such as nitrate that sustain plant life; in the reverse process of denitrification these compounds are broken down to release nitrogen. University of Washington oceanography postdoc Curtis Deutsch and his colleagues discovered that these two processes may be more closely connected than previously thought (see page 163).

How did you conduct this study?

I don't actually go to sea as I tend to get seasick. I think about new ways of using the resources of the World Ocean Atlas, which includes hundreds of thousands of measurements of things such as temperature, salinity and nutrient concentrations. Using these measurements we studied the relationship between nitrate and phosphate to learn about the rates and distribution of nitrogen fixation.

What did you find?

We found that nitrogen fixation and denitrification seem to be happening in the same ocean basins. Previously it was believed that denitrification happened in the Pacific and Indian Oceans, whereas nitrogen fixation happened halfway around the world in the Atlantic Ocean. In fact, it looks as though nitrogen fixation can happen in the well-lit surface waters more or less overlying areas of denitrification below the surface.

What is the significance of changes in the amount of nitrogen in the ocean?

Nitrogen is a scarce resource over vast expanses of the ocean. If the reservoir of marine nitrogen declined, biological productivity would fall, with a host of consequences for the ocean and climate.

Have these processes changed recently?

Our results suggest that nitrogen fixation and denitrification could be closely linked to each other in magnitude and on short time scales — such as decades. That suggests that the overall fertility of the ocean can be stabilized as opposed to undergoing rapid, dramatic fluctuations.

What is your next step?

We'd like to make measurements year after year in a few ocean regions, to get an in-depth look at how denitrification and nitrogen fixation interact with each other. That would mean I'd finally need to get over my seasickness.