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Deep-Sea Ecology
  • Largest marine biotop, but poorly known due to sampling problems (ship time)
  • Stable biotop: Temperature 1-4°C; dark; oxygen stable and seldom limiting; bottom currents generally slow (<5 cm/s); salinity ca. 35
  • Substrate is soft bottom; rocky substrates limited to mid-ocean ridges, seamounts 
  • Species composition: Holothuria (sea cucumber) and star fish are dominant below 2000 m with holothurian dominance increasing with depth; small polychaetes (brittle worms) are numerically important
  • Special groups: Pogonophora, Entero-pneusta and Echiurida (worms) are deep-sea phyla with maximum diversity/ abundance below 5000 m depth
Deep-Sea Life
  • Tendency to gigantism: benthic foraminifera and xenophyophores (gigantic amoeba), some cephalopods (squid)

  • The giant amoeba, the xenophyophores of the deep-sea; for more information visit this article on the xenophores

  • Tendency to dwarfism: deep-sea meiofauna is dominant over macrofauna; nematodes make up majority of soft-bottom meiofauna
  • Bioluminescence: to attract/lure food and to communicate with potential mates
  • Anglerfish: dwarf male lives parasitic on female (circumvents search for mates)
  • Hadal zone and regions below 6000 m depth are often inhabited by species endemic to a certain trench
The Giant Squid Archetheutis
  • The giant squid Archetheutis dux grows up to 18 m in length. Only dead, washed-up specimens have been found to date. It is assumed to be a prey for sperm whales, based on battle scars on whale skin