Recycling and Burial of Biogenic Silica in an Open Margin Oxygen Minimum Zone

An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11 degrees S and 12 degrees S. Each transect extends from the shelf to the upper slope (similar to 1,000 m) and dissects the permanently anoxic waters between similar to 200 and 500 m water depth. BSi burial (2,100 mmol m(-2) yr(-1)) and recycling fluxes (3,300 mmol m(-2) yr(-1)) were highest on the shelf with mean preservation efficiencies (34% +/- 15%) that exceed the global mean of 10%-20%. BSi preservation was highest on the inner shelf (up to 56%), decreasing to 7% and 12% under anoxic waters and below the OMZ, respectively. The data suggest that the main control on BSi preservation is the rate at which reactive BSi is transported away from undersaturated surface sediments by burial and bioturbation to the underlying saturated sediment layers where BSi dissolution is thermodynamically and/or kinetically inhibited. BSi burial across the entire Peruvian margin between 3 degrees S to 15 degrees S and down to 1,000 m water depth is estimated to be 0.1-0.2 Tmol yr(-1); equivalent to 2%-7% of total burial on continental margins. Existing global data permit a simple relationship between BSi rain rate to the seafloor and the accumulation of unaltered BSi, giving the possibility to reconstruct rain rates and primary production from the sediment archive in addition to benthic Si turnover in global models.

Automated summary

The study presents a comprehensive dataset of biogenic silica fluxes in the Peruvian oxygen minimum zone, showing that BSi burial and recycling fluxes are highest on the shelf, with greater preservation efficiency compared to global averages. The main control on BSi preservation appears to be the rate at which reactive BSi is transported. Existing global data allow for a simple relationship between BSi rain rate and the accumulation of unaltered BSi, providing the possibility of reconstructing precipitation rates and primary production in sediment archives within global models.