Resting stages of Skeletonema marinoi assimilate nitrogen from the ambient environment under dark, anoxic conditions: Anaerobic N assimilation in diatoms

The planktonic marine diatom Skeletonema marinoi forms resting stages, which can survive for decades buried in aphotic, anoxic sediments and resume growth when re‐exposed to light, oxygen, and nutrients. The mechanisms by which they maintain cell viability during dormancy are currently poorly known. Here, we investigated cell‐specific nitrogen (N) and carbon (C) assimilation and survival rate in resting stages of three S. marinoi strains. Resting stages were incubated with stable isotopes of dissolved inorganic N (DIN), in the form of 15N‐ammonium (NH4+) or ‐nitrate (NO3‐) and dissolved inorganic C (DIC) as 13C‐bicarbonate (HCO3‐) under dark and anoxic conditions for two months. Particulate C and N concentration remained close to the Redfield ratio (6.6) during the experiment, indicating viable diatoms. However, survival varied between