View article

The subtropical South Pacific Gyre (SPG) encompasses the largest oligotrophic region of the global ocean. In these remote waters dissolved organic matter (DOM) accumulates in the surface waters, though constituting a potential source of nutrients and energy to sustain microbial life. On a zonal transect across the SPG, we quantified bulk dissolved organic carbon (DOC) and assessed the DOM composition via ultrahigh resolution mass spectrometry (UHR-MS) of solid-phase extracted DOC (SPE-DOC) to elucidate the molecular-level reasons behind the apparent recalcitrance of the DOM prevailing in the SPG. We included a comparison between two individual formula assignment approaches to UHR-MS data in absorption and magnitude mode which yielded consistent results.

DOC concentrations exceeding 100 μmol C L⁻¹ in the warm and saline waters of the central gyre were higher than in the surface waters …