Biomass, feeding and metabolism of mesozooplankton in the equatorial Pacific along 180°

摘要: Abstract Mesozooplankton biomasses, grazing rates, and metabolism (respiration, ammonium phosphate excretion) were measured in the central Pacific (180°; 8°S–8°N) during EBENE cruise, October–November 1996. In HNLC zone, highest mesozooplankton biomass occurred between 6°S equator. The decrease of at northern part zone was accounted to passage a tropical instability wave, carrying poorer zooplankton concentrations from north. Within most (60–96%) found above 100 m accordance with upper distribution phytoplankton heterotrophic protists. No significant day–night differences observed biomass. These results suggest strong permanent coupling first links food chain. Respiration excretion rates steady different latitudes, but equator, lowest, highest. variations latitudinal microzooplankton density particles C/N ratios, suggesting that more nitrogen available for Moreover, among dominant copepod species, higher proportions carnivorous Higher particle equator day, while chlorophyll gut content copepods did not show any diel cycle. trophic link feeding activity, on one hand, cyclic production their main predators (microzooplankton protists), other hand. From estimations protists euphotic layer dilution experiments, mortality autotrophic taxa (from picoplankton microplankton) computed Mesozooplankton, which mainly involved catch largest (>8 μm) particles, such as diatoms or dinoflagellates, only minor (22%) total grazing, compared microzooplankton. As ration insufficient balance its expenditures, had complete diet sources low level metabolic O:N use large protein content, supports this hypothesis.