NSF Extends Funding for Research

By Richard Hoops on January 26, 2010 7:48 AM

Rising levels of carbon dioxide in the atmosphere might indirectly fertilize the ocean with nitrogen in places that are now poor in this essential nutrient. The marine organisms that are first to take advantage of this fertilizer might be at the leading edge of a profound transformation of ocean ecosystems.

David Hutchins, a marine ecologist in the USC College Department of Biological Sciences, is examining the way CO2 in the atmosphere controls nitrogen fixation at sea and how this process might change as concentrations of airborne CO2 continue to rise.

Hutchins is the principal investigator on a three-year grant from the National Science Foundation that began in 2007. The program officer who oversees the grant recently awarded Hutchins a “Special Creativity Extension” that will support his lab’s work on this study for an additional two years.

Hutchins’ research centers on a critical link between carbon dioxide in the air and nitrogen in the seawater that is determined by marine bacteria known as diazotrophs.

“We’ve established that diazotrophs are going to benefit from increased CO2 and fix more nitrogen,” Hutchins said.

One species of diazotroph known as Trichodesmium grows exceptionally well at levels of CO2 that are predicted for the future.

“We’ve looked at a lot of different species of phytoplankton at different CO2 concentrations,” Hutchins said. “Out of all of the marine microorganisms that have been examined so far, Trichodesmium shows the biggest response to increased CO2. Its growth benefits more from higher concentrations of CO2 than any other marine microorganism that has yet been examined.”

The impact of carbon dioxide on Trichodesmium could, in turn, have an enormous impact on the ocean because it provides nitrogen, an essential nutrient, for other marine life.

Nitrogen is the most common element in the atmosphere, but it does not break down easily. The bonds between molecules of nitrogen in its gaseous form are exceptionally strong, but diazotrophs like Trichodesmium produce enzymes that can break those bonds. In doing so, they fix nitrogen into compounds that marine life can use for food.

Hutchins said the winners in a nitrogen-enriched marine environment might be fast-growing but short-lived microorganisms that can respond quickly to the new inputs of nitrogen. Some of these organisms give rise to hundreds of new generations each year, and each successive generation might be better adapted to the changing marine environment.

Hutchins said these complex changes in marine chemistry and biology have the potential to overwhelm the marine ecosystems that support larger sea creatures, such as fish and marine mammals, with longer life spans.

“We’re probably not going to be happy with these kinds of changes,” Hutchins said. “They would not support the food webs and fisheries that we use now.”

Hutchins’ research so far has involved research cruises near Puerto Rico, Bermuda and the west coast of Florida and laboratory studies of diazotrophs at CO2 levels up to and beyond those predicted for the year 2100.

He said the two-year extension of the National Science Foundation grant would be used for more lab work to study how diazotrophs might adapt to higher levels of CO2, such as by changing their physiology or expression of genes.

TAGS: humanities, research

Search search

Search prior to August 2008