marine snow
n.— «The discarded mucus houses are one of the components of what scientists call “marine snow,” remains of dead organisms that sink down to the seabed. Marine snow is an important part of the marine vertical carbon flux.» —“What is on the menu for zooplankton?” by Lars Holger Ursin På Høyden (Bergen, Norway) Jan. 19, 2007. (source: Double-Tongued Dictionary)