Answer: diatom

AnswerCrossword Clue
DIATOMOne-celled sea creature
DIATOMSingle-celled alga
DIATOMPlankton constituent
DIATOMMicroscopic algae
DIATOMMicroscopic alga
DIATOMForm of algae
DIATOMMicroscopic alga: Bot.
DIATOMAquatic one-celled plant.
DIATOMMicroscopic plant: Bot.
DIATOMOne-celled marine plant.
DIATOMMarine or freshwater alga.
DIATOMOne-celled alga
DIATOMSimple bit of plankton
DIATOMPlankton component
diatomany of a class of algae