Surprises from the sea floor

Unknown planet: Around 72% of the Earth’s surface is covered by oceans, and much of that surface is still unchartered territory for science. (Graphic: SuperStock.) More than seventy percent of the surface of our planet is covered by oceans. 88 percent of their area is deeper than 1,000 metres and thus difficult to access for research. There are only a handful of research submersibles that can descend to kilometre depths, including the US research vessel Alvin, which was recently reconstituted to expand its diving range (Curr. Biol. (2011) 21, R94– R95). Remote sensing from satellites or ships also becomes challenging once there are several kilometres of water column in the way. It is for such trivial but substantial technical reasons that we still know the topography of the far side of the moon in greater detail than that of the ocean floor. Every now and again, discoveries of unexpected phenomena, which at first appear wildly exotic, highlight how little we know about the oceans. Examples include the discoveries of living coelacanths (although the species was believed to be long extinct) in 1938, of hot springs and ‘black smokers’ with rich chemosynthetic ecosystems in the late 1970s, and of ecosystems consisting mainly of archaea and their phages in 2008. Two recent publications describe biogeochemical processes in sea floor sediments that were similarly unexpected and are bound to change the scientific view of sea floor ecology.