Definition of "planktonic"

planktonic

/plaŋkˈtɒnɪk/

adjective
not comparable
1. Of or pertaining to plankton.
  Quotations
  Tiny shells of planktonic animals rain down from the surface waters of the ocean on to the deep sea-floor.
  2004, Richard Fortey, The Earth, Folio Society, published 2011, page 146
2. Floating in the open sea rather than living on the seafloor.