Impact of bacteria and zooflagellates on the composition of sinking particles: an in situ experiment

Abstract

Multiple sediment trap (MULTITRAP) arrays were deployed at 3 hydrographically and biologically distinct stations in the eastern North Pacific Ocean and used to evaluate experimentally the hypothesis that protozoan grazers are important in the diagenesis of sinking biogenic materials in the ocean. Trap-collected bacteria and zooflagellates accounted for a low percentage of the total POC (2 to 11%) but a high percentage of the total microbial biomass (an estimated 25 to greater than or equal to 100% of total ATP). Zooflagellates were the principal protozoans collected and accounted for 2 to 25% of the total microbial biomass. Synthesis of RNA and DNA was observed at all stations and depths, indicating microbial growth in the live traps. ATP and microscopic analyses, however, independently confirmed that death rates exceeded growth rates on the sedimenting particles.