The origin of transparent exopolymer particles (TEP) and their role in the sedimentation of particulate matter

Seasonal changes in the concentration of suspended transparent exopolymer particles (TEP) and flux rates of TEP and other particles at 500 m were measured at 2-week intervals at a station in the Santa Barbara Channel between May 1995 and June 1997 in order to investigate the hypothesis that the presence of TEP is necessary for the aggregation and subsequent sedimentation of particles from the pelagic zone. During the 2-year period phytoplankton appeared to be the most significant source of TEP. However, in association with phytoplankton, the concentration of TEP was also positively affected by bacteria abundance. Possibly bacteria enhance the production of TEP by phytoplankton. The presence of TEP was necessary for the sedimentation of diatoms. However, only 67% of the peaks in particulate organic carbon flux corresponded to peaks in TEP flux. Lithogenic silica sedimented only when scavenged by marine snow; either by TEP-rich diatom aggregates or by zooplankton-derived snow (larvacean houses). TEP were not involved in the sedimentation of foraminifera. Although sedimentation was the dominant loss processes of TEP out of the euphotic zone, other loss process must have been important at greater depth, as only a small fraction of the standing stock of TEP arrived at 500 m.