A sediment trap-based study of particle fluxes in San Pedro basin, CA: Remineralization rates of organic carbon and biogenic silica

A four-year sediment trap study, beginning January 2004, was conducted in San Pedro Basin, CA using moored traps located at 550 m and 800 m water depth. Two floating sediment traps were deployed seven times at 100 m and 200 m between November 2007 through June 2008. Fluxes of mass, particulate organic carbon (POC or Corg), calcium carbonate (CaCO3), biogenic silica (bSiO2), detrital, Corg/N, delta 15N, and delta13C were determined.;Deep trap fluxes were examined along with climatological data to explore the relationship between the timing of physical forcing and particle deposition. Rainfall history, compared to detrital flux and patterns of delta 15N and delta13Corg shows that the detrital fluxes and organic carbon fluxes into the sediment traps are marine-derived. There is no immediate pulse of terrestrially-derived sediment delivered to San Pedro Basin following winter rains.;Remineralization patterns were examined using flux data from all traps and the Martin equation, which predicts the downward flux of POC based on a power law relationship with a variable "b" that dictates the attenuation of the flux curve. Martin b values were highly variable with no seasonal pattern, although the average b value was 0.47 compared to the open ocean value of 0.86. This implies that given the same flux of POC from the surface, Corg is removed from San Pedro Basin more efficiently than in the open ocean.;Incubation experiments were performed on freshly captured particles from 100 m and 200 m to examine the affects of temperature, oxygen, depth, and season on remineralization rate constants for Corg and bSiO 2. Both Corg and bSiO2 showed higher reactivity at 100 m versus 200 m and also higher reactivity at 25°C versus 10°C. Corg remineralized faster in the fall than in the spring and bSiO 2 showed the opposite trend. Remineralization rates for Corg did not change in oxic versus suboxic conditions, although for bSiO2 they were different at 200 m and not at 100 m. Incubation data reveal detailed information of remineralization rates under changing oceanic conditions that can be incorporated into global circulation models to better predict how oceans will change with changing environmental conditions.