A possible origin of some olive‐green cells in aphotic marine environments 1

Spheroidal cellular fragments were produced by resting cells of Amphora coeffaeformis (Bacillariophyceae) in laboratory cultures simulating the cold, dark conditions of aphotic ocean water. The light microscopic morphology and ultrastructure of these cellular fragments resemble olive‐green cells (group 1) that occur below the euphotic zone. The abundance of olive‐green cells in deep water beneath high productivity regions may result from the settling of phytoplankton into the dysphotic and aphotic zones where resting cells and their cellular fragments could be produced.