Early diagenesis of organic matter in sediments off the coast of Peru

Measured rates of SO4 and NH4 were used to estimate organic matter regeneration from the sediments in an area of intense upwelling and high primary production off Peru. While the estimated rates of remineralization were high compared to other ecosystems at comparable water depths, this source of nutrients appeared to be on the order of 10% of the phytoplankton demand. Disparities between measured vs modelled estimates of sulfate reduction appear to be a function of the concentration gradients across the sediment-water interface and mixing by biological and physical processes. The suite of measurements allowed estimation of 'irrigation' and an 'irrigation' coefficient at the nearshore station where measured rates were considerably above those estimated from the pore water sulfate gradient.