This study will use enzymatic indicators of metabolic function and direct measurements of respiratory rates to describe the pattern of metabolic potentials of midwater animals as a function of depth of occurrence, the presence of mid-depth oxygen minima, and body size. Preliminary data suggest that previous generalizations based on physiologically complex, visually-orienting fishes and crustaceans are not generally applicable to micronekton and zooplankton of other taxa which have largely been ignored in previous studies. This study will allow investigation of a broader range of animals than previously possible, especially those which are more fragile in structure, enabling us to extend the description of the patterns of variation in metabolic potential to all of the major midwater groups (with emphasis on chaetognaths, medusae, worms and molluscs and more superficial work on ctenophores and siphonophores). The research is directed at achieving a synthesis of the carbon fluxes through this ecosystem. This application of the research will be tested by collecting data on the biomass of the major groups of midwater animals in a 4100 m California Current water column and using the metabolic data to estimate respiratory carbon flux due to zooplankton and micronekton in this community.
