Alyson Santoro

Alyson Santoro, a postdoctoral researcher at Woods Hole Oceanographic Institution, writes from off the coast of Chile, where she is studying microbes in the nitrogen cycle.

Saturday, March 19

The federal government isn’t the only group with a problem balancing its budget these days. Oceanographers have a budget problem too. Nitrogen — an essential nutrient for all life on the planet — is at the heart of this budget crisis. Some estimates of the amount of nitrogen leaving the ocean exceed estimates of the amount of nitrogen coming in by several hundred teragrams (that’s one billion kilograms) per year. Does this mean that the ocean is actually losing nitrogen? Probably not, but it does mean that we don’t have a good understanding of where in the ocean nitrogen is coming and going. Over the next five weeks, I will be joining a team of researchers from around the world on a research cruise to the eastern tropical South Pacific off the coast of Chile to see if this could be one area where the “missing” nitrogen could be entering the ocean.

I just arrived in the port of Valparaíso, Chile, after a nearly 24-hour journey from Cape Cod, Mass. My home for the next five weeks is the 279-foot-long research vessel Melville, which is owned by the United States Navy and operated by the Scripps Institution of Oceanography. Our planned cruise track looks like a large rectangle with the long sides on the top and bottom. Along the way we’ll stop at six “stations,” or geographic way points, to collect water, deploy sampling devices, and hopefully retrieve some samplers we left out over a year ago. All our efforts will be centered around nitrogen.

Carolyn Buchwald

Nitrogen can make it into the ocean in one of three ways: it can be deposited as particles from the atmosphere, it can come from the land via rivers or groundwater, or it can be taken directly from the atmosphere by specialized microscopic organisms that break the very strong chemical bond between two nitrogen atoms. It is this last pathway, called nitrogen fixation, that will be the focus of the cruise.

Nitrogen fixation, like every other major transformation in the nitrogen cycle, is carried out by microorganisms — bacteria and archaea. Though nitrogen fixation is the main topic of the cruise, many of the 20 researchers on board, including me, will be studying other parts of the nitrogen cycle to try to learn more about how the different reactions, and different microbes, work together.

Just as microbes work together, an essential part of oceanographic research is working with other scientists, and I’ll be doing lots of it on this cruise. One of the most important people for my work is Carly Buchwald, a graduate student in the Woods Hole-M.I.T. Joint Program. Carly and I began our work for this year’s cruise back in January, when we started planning details of our sampling plan and experiments with Karen Casciotti, an assistant professor at Stanford University and the principal investigator for the project. We’ll also be helping out with the larger goals of the cruise, collecting samples that will be used by scientists from the University of Southern California and the University of Miami to assemble a nitrogen budget for this region.

Our equipment and supplies left Los Angeles in a shipping container about two months ago. Before our ship leaves on Wednesday, our job is to unload the container and set up our laboratory space. We need to be ready to take and process samples by the time we arrive at the first station, 900 nautical miles and three days of steaming from the coast. The ship’s crew will also be busy, filling the hold with food and supplies, and fueling up for our 35 days at sea. I look forward to writing about the details of our scientific work, and of life at sea. A link to the ship’s position and at-sea photos is available here.