| Summary: | During the Arctic Shelf Growth, Advection, Respiration and Deposition (ASGARD) cruise in the northern Bering Sea and Chukchi Sea (5 – 28 June 2017) we examined diatom production and phytoplankton growth and microzooplankton grazing losses. Quantification of total silica production can be a metric to estimate diatom production. Normalizing silica production to diatom biovolume-derived living-cell-associated silica using low-temperature allometric equations gave realistic growth values (considering the temperature at the time of sampling and a survey of literature measuring diatom growth in culture and field conditions). Field experiments to quantify grazing rates on phytoplankton showed that small phytoplankton, primarily non-diatoms, were heavily and consistently grazed, while larger phytoplankton (e.g. diatoms) were not. Out of 26 separate experiments, grazing on large-sized phytoplankton (e.g. diatoms) by microzooplankton was quantifiable in 14 experiments (54%) whereas grazing on smaller phytoplankton (non-diatoms) was quantifiable in 23 experiments (88%).
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