Amazon powers Atlantic Ocean's carbon sink: study

Yahoo News 21 Jul 08;

Nutrients carried by the Amazon River help create a carbon sink deep in the Atlantic Ocean, a study released Monday has found.

The key ingredients transported by the river are iron and phosphorus.

These elements are all that an organism called a diazotroph needs to capture nitrogen and carbon from the air and transform them into organic solids that then sink to the ocean floor.

Researchers from the United States, Greece and England found that the Amazon carries these elements hundreds of kilometers into the ocean and has an impact on the carbon and nitrogen cycles much farther afield than previously thought.

It is likely that other rivers also help seed carbon sequestering in the world's oceans, wrote senior author Doug Capone of the University of Southern California.

The findings may help scientists find the best places to test seeding the ocean with iron, a controversial practice that some biologists believe could help mitigate climate change.

There are concerns that iron fertilization could harm sea life and potentially lead to increased production of other greenhouse gases, Capone said.

But while iron fertilization in cooler waters could be undermined by the upward flow of water from the depths, tropical waters could keep captured carbon solids from returning to the surface, he said.

"If we choose as a human society to fertilize areas of the oceans, these are the places that probably would get a lot more bang for the buck in terms of iron fertilization than we would at high latitudes," Capone said.

The study was published in the Proceedings of the National Academy of Sciences.