9314610 Glibert This US-Brazil Cooperative Science award will support the collaboration of Patricia Glibert of the University of Maryland and Patricia Metzler, a Ph.D. student at the University of Sao Paulo, Brazil. The project aims to measure planktonic nitrogen transformations off the coast of Brazil. The importance of nitrogenous nutrients in marine primary production has long been recognized. Their regeneration is known to be a major source of nitrogen for oceanic primary producers, but it is the rate of supply of "new" nitrogen which ultimately determines the amount of production. There have been virtually no direct measurements of the rates of nitrogen transformation in the western South Atlantic. In this project, the researchers will apply 15N stable isotope tracer techniques to investigate physiological and trophodynamic responses to nitrogen fluxes in Brazil's coastal and offshore waters. The experiments will elucidate the relationship between size- and time-dependent responses by plankton to new nitrogen inputs and the dependence on new versus regenerated nitrogen. These studies will benefit both sides by producing data for an undersampled part of the world's oceans, establishing a new area of research in Brazil, and training a Brazilian student in methodology for these experiments. ***
