Ascending marine particles: Significance of transparent exopolymer particles (TEP) in the upper ocean

The high abundance of transparent exopolymer particles (TEP) in marine and freshwater greatly affects particle dynamics. TEP act as glue for colliding particles and form the matrix in aggregates, thereby altering aggregation dynamics. We studied the sinking behaviour of freshly produced, particle-free TEP and of aggregates composed of TEP and latex spheres in a laboratory using water collected from Santa Barbara Channel, California. Particle-free TEP ascend and accumulate in the surface layer of a settling column at an average velocity of 1.6 X 10(-4) cm s(-1). The estimated density of TEP ranges from 0.70 to 0.84 g cm(-1). TEP also transported latex spheres of 45.6 and 1.82 mum in diameter and a density of 1.05 g cm(-1) to the surface layer. We describe a simple model illustrating the role of TEP for the vertical transport of solid particles. The densities and relative proportions of TEP, solid particles, and interstitial water within an aggregate determine its sinking or ascending velocity. High rations of TEP to solid particles retard the sinking of aggregates, prolonging their residence time in the surface ocean. Our results demonstrate that TEP can provide a vehicle for the upward flux of biological chemical components in the marine environment, including bacteria, phytoplankton, carbon, and reactive trace elements.