The smallest particles (0.5–10 μm) comprise
microalgal cells, bacteria, fine organic detritus and inorganic
particles such as coccoliths, diatom skeletons and
clay particles which often have an organic coating. The
size range of tens to hundreds of μm includes the larger
microalgae (especially diatoms), detritus and faecal pellets;
these particles often result from biological
repackaging of organic matter through feeding and excretion.
Larger particles are known as marine snow (or
fluff) which consist of detritus, phytoplankton and bacterial
cells, and some clays and other inorganic matter. Thus
the term “POM” can comprise a complex mixture of living
and nonliving organic matter having a broad size
range, form and reactivity.