Sunday, August 21, 2011

Denizens of the Deep

Hello, this is Alex. I want to tell you about some of the amazing animals that we are finding below 600 meters. Using the MOCNESS we capture samples as deep as 1000 meters, from a habitat unfamiliar to most people.
A deep sea sample gets poured through a sieve from the cod end of the net 1 (800-1000 m) [photo: A Bergan]

Light is too low here for us to percieve, and those animals that are visual must either create their own light (biolumnescence) or have specially adapted eyes.

Red is the first wavelength to disappear as we descend to depth, so this deep red shrimp would simply look black, and have a better chance of hiding from predators than if it lived at the surface. [photo: A Bergan].
Another fact of deep sea living is that food is patchy in time and space. But if you move around too much in search of food, you become more likely to be ambushed and eaten. The key is to keep your prey once you find it, which is acomplished by large teeth as seen in the fish below.
[photo: A Bergan]

[photo: K. Wurtzell]
Many deep sea species have slow growth rates, but long lives and end up becoming rather large. We found our largest pteropod between 800-1000 m; see the Clio polita from Gareth's post on August 18th. Here is a particularly large amphipod who is also found in that depth range.
This gammarid amphipod has reduced eyes. For it the cost of sight outweighs the benefit. [photo: K. Wurtzell]

The deep sea is full of mystery and we are only scratching the surface. Often the open ocean is deeper than 4000 meters, and we are only sampling to a quarter of this depth. What lies beneath? If this excites your sense of exploration, then deep sea oceanography is for you!
A squid found between 600-800 meters. We also see squid from the deck at night. Does this species have a daily vertical migration? Is it a different species that stays at depth? Is this a juvenile that stays deep to grow up before rising to the surface? [photo: A Bergan]

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