Investigating the Nutrient Landscape in a Coastal Upwelling Region and Its Relationship to the Biological Carbon Pump
Michael R. Stukel, Katherine A. Barbeau
Abstract
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 4 3− :NO 3 − and Si(OH) 4 :NO 3 − 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.