DOWNWARD EXPORT OF RESPIRATORY CARBON AND DISSOLVED INORGANIC NITROGEN BY DIEL-MIGRANT MESOZOOPLANKTON AT THE JGOFS BERMUDA TIME-SERIES STATION

Published calculations suggest that downward fluxes of respiratory carbon (RC) and dissolved inorganic nitrogen (DIN) associated with diel-migrant zooplankton are significant forms of export production. In this study, we examined variability in downward fluxes of RC and DIN due to diel-migrant mesozooplankton (200-2000 mu m) on seven occasions between 25 March and 8 April 1990 at the JGOFS (Joint Global Ocean Flux Study) station off Bermuda. Downward fluxes due to migrators crossing 150 m ranged from 6 to 41 mgC m(-2) day(-1) (RC) and 2 to 5 mgN m(-2) day(-1) (DIN). In comparison to gravitational fluxes of POC and PON measured with particle traps at 150 m during the same period, mesozooplankton RC flux was 18-70% of POC flux and mesozooplankton DIN flux was 17-82% of PON flux. If the RC and DIN fluxes due to migrators are considered in calculations of export production, the percentage of the production exported below 150 m over the study period would increase by an average of 25% for carbon and 21% for nitrogen. These results support the contention that metabolic activities of diel-migrant zooplankton should be included in calculations of export of carbon and nitrogen out of the mixed layer.