Newly discovered deep-sea currents carry biota from one vent to another

Newly discovered deep-sea currents carry biota from one vent to another

The "accepted wisdom" for many years has been that the deep-sea ocean floor was boring; nothing much happened, including currents. Some areas were assumed to be so devoid to life and motion that they were considered as potential burial sites for nuclear wastes. They are no longer viewed that way.

With the discovery of deep-sea vents in the 1970's, the deep-ocean bottom has opened up an entirely new and fascinating world of biota. Vents support populations of bacteria, giant worms, clams, shrimp, and other animals. Unlike most other ecosystems on Earth, these "communities" do not rely on photosynthesis. The bacteria at the bottom of the food-chain rely on the chemicals emitted by the vents for energy.

One issue has puzzled researchers for a long time. Vents often have a very finite "life time", and are spaced widely apart. How do the various "critters" travel from one vent to another? Why do I say travel? Because researchers have found surprisingly little genetic variation between populations around various vents even though the vents are widely spaced. A research report last year noted that even after a vent was destroyed by a volcanic eruption, it was quickly recolonized by larval creatures, some of which appeared to have travel over 300 km (186 miles) from another vent. See, for example, http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011646.

Researchers have recently noted one mechanism by which such travel could happen, and in the process discovered how surface weather influences the deep ocean, an area (as noted) previously thought to be isolated and closed from surface activity. Researchers were monitoring vents more than 2 km below the surface. They noted that the quantity of larva and certain vent chemicals feel sharply during periods of unusually strong deep-sea currents. The researchers suggest that the process of sweeping larva away and, so to speak, scattering them to the wind is akin to the strategy many plants adopt on land (scattering seeds or pollen, only some of which land where they can grow).

What was also interesting was that these currents were correlated with wind-generated mesoscale eddies (swirls of water tens or even hundreds of kilometers across) on the ocean surface. They also noted that surface eddies tended to form in spring and autumn and were more common in El Nino years. This would seem to provide a mechanism by which larva could disperse ("travel") from one vent to another. See http://www.womenoceanographers.org/Default.aspx?pid=E1E3254E-1C80-4e6d-ABBF-1EC5F5436C3E&id=laurenmullineaux and http://www.sciencemag.org/content/332/6029/580.

Thus, insight into one problem has also shown that surface activity has an influence on events in the deep-ocean, events that change our understanding of deep-ocean dynamics.

Ocean

Lexis.com subscribers can access our extensive resources on Environmental Law.

For more information about LexisNexis products and solutions connect with us through our corporate site.