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Abstract

A fraction of organic carbon produced in the oceans by phytoplankton sinks storing 5–15 gigatonnes of carbon annually in the ocean interior. The accepted paradigm is that rapid aggregation of phytoplankton cells occurs, forming large, fresh particles which sink quickly; this concept is incorporated into ecosystem models used to predict the future climate. Here we demonstrate a slower, less efficient export pathway in the Eastern Tropical North Pacific. Lipid biomarkers suggest that the large, fast‐sinking particles found beneath the mixed layer are compositionally distinct from those found in the mixed layer and thus not directly and efficiently formed from phytoplankton cells. We postulate that they are formed from the in situ aggregation of smaller, slow‐sinking particles over time in the mixed layer itself. This export pathway is likely widespread where smaller phytoplankton species dominate. Its lack of representation in biogeochemical models suggests that they may be currently overestimating the ability of the oceans to store carbon if large, fast‐sinking, labile particles dominate simulated particle export.

Item Type:	Article
Authors/Creators:	Cavan, EL and Giering, SLC and Wolff, GA and Trimmer, M and Sanders, R
Keywords:	organic carbon cycle, lipids, sinking particles
Journal or Publication Title:	Journal of Geophysical Research: Biogeosciences
Publisher:	Wiley-Blackwell Publishing Inc.
ISSN:	2169-8953
DOI / ID Number:	https://doi.org/10.1029/2018JG004392
Copyright Information:	©2018. The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) http://creativecommons.org/licenses/by/4.0/
Related URLs:	Google Scholar: Cavan, EL UTAS Profile: Cavan, EL
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