is defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres or the point of transition from continental shelves to continental slopes.
Deep sea
- Sunlight zone or epipelagic zone
- surface layer down to 150-200 m
- there is enough light
Euphotic Zone
- Mesopelagic Zone
- surface layer from 200-1000 m
- There is still some dim light
Dysphotic Zone
- Bathypelagic, Abyssopelagic, & Hadopelagic Zones
- depth below 1000 m
- no sunlight
Aphotic Zone
Animals migrate to the surface at night.
Vertical Migration
Only about ……. of surface primary production sinks to the
mesopelagic .
20%
Have:
● swim bladder
● Well developed muscles and bones
Vertically migrating fishes
They help mid water animals see in the dim light
Sense organs
Some mid water fishes have developed tubular eyes that give very acute vision in the direction that the eyes are pointed, either upward or forward, but are not good for lateral vision.
Tubular eyes
Most mid water animals have evolved an even more effective way to mask their silhouettes
Bioluminescence
includes depths between 1,000 and 4,000 m
bathypelagic zone
lies from 4,000 to 6,000 m.
abysso pelagic zone
consists of the waters of the ocean trenches, from below 6,000 m to 11,000 m.
hadopelagic, or hadalpelagic, zone
- always dark
- always cold
- temperature remains nearly constant, typically at 1-2°C
World of Perpetual Darkness
- prey attraction
- communication
- courtship
uses of bioluminescence
Many deep-sea animals have functional eyes, especially in
upper parts of the deep sea
mesopelagic fishes spend less energy on …… and more on ……
growth, reproduction
females apparently release a special chemical that the male can detect and follow. Such chemicals are called
pheromones.
pressure in the deep sea is
tremendous
deepest known fish was recorded at a depth of
8,370 m.
Bacteria that live in the deep sea where there is pressure and cold, known to be
slow bacterial growth
