Metabolic Poise in the North Atlantic Ocean Diagnosed from Organic Matter Transports

Recently there has been discussion about the metabolic state of the ocean, with arguments questioning whether the open ocean is net autotrophic or net heterotrophic. Accurately determining the metabolic balance of a marine system depends on fully defining the system being evaluated and on quantifying the inputs and outputs to that system. Here, a net northward transport of dissolved organic carbon (DOC) (across 24.5°N) of 3.3 ± 1.9 Tmol C yr-1 was determined using basin-wide transport estimates of DOC. This flux, coupled with DOC inputs from the Arctic Ocean (2.2 ± 0.8 Tmol C yr-1 the atmosphere (0.6 ± 0.08 Tmol C yr-1) and rivers (3.1 ± 0.6 Tmol C yr-1), indicates net heterotrophy in the North Atlantic (full depth, 24.5-72°N) of 9.2 ± 2.2 Tmol C yr-1. This rate is small (