The central equatorial Pacific is a very large region with high primary production, which is hypothesized to support a substantial faction of global new production. New production is important because of its link to the vertical flux of meterial from the upper to the lower ocean and the implied role of that link in how the ocean cycles radiatively-active gases (the greenhouse problem). This project constitues a part of the US joint global ocean flux study (JGOFS) in the central equatorial pacific and seeks to answer some baic questions about the role of heterotrophic bacteria in the equatorial Pacific. Heterotrophic bacteria are believed to be an important component of the equatorial pacific system as: 1. they are one of the predominant sinks of dissolved organic nitrogen and carbon; 2. they are nitrogen rich with a carbon to nitrogen ratio of about 4.5; 3. they comprise a large portion of the biomass, and may at times be greater than the phytoplankton; and 4. they account for a large fraction of ammonium uptake in a number of marine systems. This project will examine the role of heterotrophic bacteria in nitrogen cycling in the equatorial pacific and will specifically measure bacterial production, biomass, and nitrogen uptake by bacteria.