Investigating the nutrient landscape in a coastal upwelling region and
its relationship to the biological carbon pump
Abstract
We investigated nutrient patterns and their relationship to vertical
carbon export using results from 38 Lagrangian experiments in the
California Current Ecosystem. The dominant mode of variability reflected
onshore-offshore nutrient gradients. A secondary mode of variability was
correlated with silica excess and dissolved iron and likely reflects
regional patterns of iron-limitation. The biological carbon pump was
enhanced in high nutrient and Fe-stressed regions. Patterns in the
nutrient landscape proved to be better predictors of the vertical flux
of sinking particles than contemporaneous measurements of net primary
production. Our results suggest an important role for Fe-stressed
diatoms in vertical carbon flux. They also suggest that either
preferential recycling of N or non-Redfieldian nutrient uptake by
diatoms may lead to high PO:NO and Si(OH):NO ratios, following export of
P- and Si-enriched organic matter. Increased export following Fe-stress
may partially explain inverse relationships between net primary
productivity and export efficiency.