Little is presently known about the conditions under which dissolved organic carbon (DOC) is produced or destroyed in modern oceans or about the role of DOC in the structure and dynamics of aquatic marine microbial ecosystems. The objective in this research is to develop a mass spectrometric method for shipboard determination of carbon-isotopic compositions of DOC and shorebased determination of carbon-isotopic compositions of DOC and shorebased determination of carbon-isotopic compositions of organisms constituting the marine microbial food web. Availability of such techniques should facilitate large-scale studies of the origin and recycling of DOC. DOC is the largest organic carbon reservoir in seawater and, accordingly, is particularly important in the global carbon cycle. Techniques for study include light stable mass spectrometry for carbon isotopes, high-temperature catalytic combustion techniques for the determination of the abundance of DOC, flow cytometry for the separation of individual cell types and experimental growth of mixed bacterial populations.
