A particle flux study in the Santa Monica-San Pedro Basin off Los Angeles: particle flux, primary production, and transmissometer survey

In May 1983, two short-term (2.5 d) deployments of sediment traps at 100, 300, and 500 m measured the sinking flux of mass (as dry weight), particulate organic carbon and carbonate carbon in the nearshore basins off Los Angeles. The flux of organic carbon at 100 m depth was about 15% of the mass flux and about 5% of the rate of primary production measured in the surface waters. At 500 m the flux of organic carbon had decreased to about half that at 100 m. Characteristics of the trap collections indicated a large biogenic contribution. In the second deployment, much of this appeared to be the fecal material of the pelagic red crab, Pleuroncodes. The biomass carbon of microorganisms determined by microscopy (exclusive of heterotrophic bacteria) in the surface waters was dominated by nano- and picoplankton size categories. In the sediment trap collections, total microorganism carbon comprised