The importance of transparent exopolymer particles over ballast in determining both sinking and suspension of small particles during late summer in the Northeast Pacific Ocean

Gravitational sinking of particles is a key pathway for the transport particulate organic carbon (POC) to deep ocean. Particle size and composition influence particle velocity thus play critical role in controlling flux. Canonically, that reach mesopelagic are expected be either large or ballasted by minerals. However, presence transparent exopolymer (TEP), which positively buoyant, may also velocity. We investigated relationship between during Export Processes Ocean from RemoTe Sensing (EXPORTS) campaign Northeast Pacific using Marine Snow Catchers. Suspended were sized FlowCam imaging, their biogeochemical was assessed measuring concentration nitrogen, inorganic carbon, biogenic lithogenic silica, TEP. Sinking fluxes calculated. Overall, both suspended small (<51 μm, diameter) this late summer, oligotrophic system. Contrary expectation, ratio ballast minerals POC higher than particles. Further, showed TEP-to-POC ratios three times These suggest TEP content not dictated whether system would sink (low TEP) remain (high TEP). Fluxes averaged 4.3 ± 2.5 mmol C m−2 d−1 at 50 m (n = 9) decreased 3.1 1.1 300–500 6). flux estimates slightly measured EXPORTS with drifting sediment traps Thorium-234. A comparison these approaches illustrates an important component summer