We will conduct field-based, process studies of mesozooplankton-mediated export in the NE Pacific and N Atlantic Oceans. Our objectives are to: 1) Quantify production and export of fecal pellets and other zooplankton by-products (e.g., mucous feeding webs, molts, carcasses), and 2) Quantify active transport of carbon (C) from the euphotic zone by both diel and ontogenetic (seasonal/life-cycle) vertical migrations. The guiding hypothesis is that changes in phytoplankton community structure and NPP affect zooplankton abundance, biomass, size, and taxonomic structure, all of which controls and scales to export in a quantifiable and predictable way. Satellite observables and data products, including euphotic zone phytoplankton functional type, relative phytoplankton size, particle size spectrum, light attenuation, and temperature are all variables that can be used to predict zooplankton community structure, and in turn zooplankton-mediated export. Fecal pellet production experiments will be conducted on board, and fecal pellet production rates will be scaled up to community rates using abundance quantified from net tows. Production of fecal pellets in surface waters will be compared to export of fecal pellets at different depths as measured by sediment traps–to examine export efficiency of pellets or other zooplankton by-products, and to mesopelagic zooplankton community structure. To quantify active transport by vertical migration we will perform depth-stratified day/night net sampling through the epi- and mesopelagic zones using a MOCNESS (multiple opening-closing net) and a CTD-mounted camera system. Onboard incubation experiments measuring the metabolism of representative, abundant migrating taxa from different size classes, combined with existing size-temperature algorithms of metabolism will be used to quantify export by diel and seasonal migrators. These will also be compared with electron transport system measurements on size-fractioned zooplankton to determine depth-stratified metabolic carbon demand.