Micro-grazer biomass, composition and distribution across prey resource and dissolved oxygen gradients in the far eastern tropical north Pacific Ocean

► We quantify heterotrophic protist demographics across oxygen gradients in the ETNP. ► We measure heterotrophic protist grazing at two contrasting regions in the ETNP.► Higher than previously reported microzooplankton biomass was found. ► Dissolved oxygen concentration non limiting to microzooplankton in ETNP. ► Heterotrophic protist grazing estimates fall within ranges from other tropical regions.