epiplankton

from The Century Dictionary.

• noun The animals and plants which float or swim at the surface or above the hundred-fathom line, considered collectively and in contrast with the dwellers in deeper water; the pelagic plankton (which see, under plankton).

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Plankton normally living in the top hundred fathoms of a body of water (at a depth of about 180 metres or less).