Award: OCE-1459584

Oxygen minimum zones (OMZ) are vast regions of the world?s oceans where oxygen drops to zero. Unlike the notorious "dead zones" in places like the Gulf of Mexico, they are not caused by human activities but have existed for thousands of years. Oceanographers study their chemistry because processes occur there that do not take place elsewhere in the oceans that can affect global budgets of nitrogen, iron and other elements important to marine life. In this project, we are studying how iron chemistry in these zones affects its transport from the coast to the ocean?s interior. Our study site is the OMZ off the coast of Southern Mexico. Iron enters the system from the land as dust, and also from the Rio Balsas, Mexico?s largest west coast river. Within the OMZ some of it is converted to ferrous iron - a form that would oxidize quickly to the ferric form (i.e. rust) in the presence of oxygen. Instead, it stays dissolved and moves offshore in an underwater plume 100-300m below the sea surface. This plume is important in supplying iron – an element essential for all life – to the ocean interior. But ferrous iron is hard to measure, and many previous workers think they are measuring the ferrous form when they are measuring something else. So we made some key improvements in the methodologies that scientists use. Ph.D. student Ken Bolster has written a peer-reviewed scientific article that describes what we did. The work also gives us an idea about iron and other elements behaved in ancient oceans, before there was any oxygen in the oceans and atmosphere. The project involved collaboration with Mexican Scientists, including Alejandro Arias, a postdoc funded jointly by this project, the University of Southern California and CONACYT, a Mexican funding agency. The project also supported two undergraduates, Rafael de la Zerda (University of Miami) and Natalianne Tuttle (Humboldt State University) who were studying iron redox chemistry off the coast of Southern California?s Catalina Island. Last Modified: 03/31/2018 Submitted by: James W Moffett