Particulate matter fluxes into the benthic boundary layer at a long time-series station in the abyssal NE Pacific: composition and fluxes

Sediment traps were deployed to collect contiguous 10-day samples of sedimenting particulate matter at 600 and 50 meters above bottom (mab) at an abyssal station off of the central California coast (Sta. M, 4100-m depth) over a 6-yr time period. Interannual variations were manifested in fluxes at both depths with high fluxes in 1991, 1993, and 1994. Low particulate matter fluxes observed in 1992 may have resulted from a well-documented El Niño-Southern Oscillation (ENSO) event, but the mechanisms responsible for the low fluxes observed in 1995 and 1996 were not resolved. Particulate fluxes were impacted by upwelling with a lag time of ∼50 days between the Bakun upwelling index and the arrival of particulate matter to the 600-mab trap. Allowing time between the upwelling of nutrients and the flux of material from the photic zone, we estimate a sinking rate of ∼100 m day -1. There was generally a peak in particulate fluxes in the summer with a secondary peak in the fall. Decreased concentrations (mg gdwt -1 of total particulates) of organic carbon, CaCO 3, and particulate nitrogen in the summer were attributed to dilution effects from siliceous plankton. Particulate fluxes were higher at 50 mab (4050 m depth) than at 600 mab (3500-m depth), suggesting an input of laterally advected material at 50 mab, possibly from the Monterey Canyon northeast of Sta. M. The variability of particulate and component fluxes during this 6-yr period illustrates the importance of long time-series studies for interpreting organic matter input and its importance to deep-sea communities.