Plankton metabolic activity in the eastern tropical North Pacific

Abstract

Respiratory electron transport system (ETS) activity of nannoplankton and zooplankton in the euphotic zone was measured at 14 stations in the eastern tropical North Pacific. In addition, ETS activity and zooplankton biomass were measured from the surface to 3000 m at two stations. Respiration rates were calculated from the ETS activities using empirically derived constants. The respiration rates in the euphotic zone, when compared to the regional productivity, indicate that most of the carbon fixed in the euphotic zone was respired there. This was supported by a vertical respiration budget that indicated that 75% of the respiration from 0 to 3000 m occurred within the euphotic zone and > 90% occurred above 200 m. ETS-derived respiration rates in the deep sea (1 to 3 km) were in agreement with rates calculated from temperature, salinity, and oxygen data using a vertical advection-diffusion model.