1. Below the Surface

2. Abiotic Factors Affecting Deep Sea Organisms
Oxygen Levels
Thermohaline circulation: Where water is cold and salty, it sinks, pulling oxygen into the deep sea (Greenland & North Antarctica)

3. 2. Light - lack of or tiny eyes Lack of color (its not useful)
bioluminescence to attract prey, mates or escape predation
Chemosensory organs most evolved here (smell)

4. Muscle absent or flabby Swim bladders are absent / filled with oil
3. Pressure
Muscle absent or flabby
Swim bladders are absent / filled with oil
8,730 meters – deepest fish recorded (27,460 ft)
Can effect enzymes and metabolism
Scuba Record: Only eight persons are known to have ever dived below a depth of 800 feet (240 m) on self contained breathing apparatus recreationally.That is fewer than the number of people who have walked on the moon!!
The Holy Grail of deep SCUBA diving was the 1,000 ft (300 m) mark, first achieved by John Bennett in 2001, and has only been achieved five times since

5. Deep-sea environments

7. A.k.a. Twilight zone
includes the oxygen-minimum layer, where organic matter decaying uses up oxygen rapidly
Includes thermocline, a rapid drop in temperature
“Deep Sea” includes everything below 1000meters, only 20% of organic matter reaches the twilight zone, only 5% reaches the deep sea!

8. Mesopelagic/Twilight Zone Morphology
Small (5-15 cm)
Largest Eyes
Migrators have strong muscle and bone and developed swim bladders
Non-migrators are flabby, with no swim bladder
Ventral photophores along the underside for counterillumination

9. Deep Sea Morphology Larger than in the mesopelagic
Do not vertically migrate
small or non-functional eyes
Large mouths & teeth
Swim bladder oil or non-existent
Food is scarce

10. Deep Sea Gigantism
Many organisms of the deep sea have evolved to be GIANT versions of their shallower selves. Using their energy to increase their size rapidly aids in survival and energy conservation

11. difficult to find mates
ex. Parasitic male!

12. Abyssopelagic: ex.Rat Tails

14. The cause of narcosis is related to the increased solubility of gases in body tissues, as a result of the elevated pressures at depth (Henry's law).12 Modern theories have suggested that inert gases dissolving in the lipid bilayer of cell membranes cause narcosis.13 More recently, researchers have been looking at neurotransmitter receptor protein mechanisms as a possible cause of the narcosis

15. History of mid-water science
Discovery followed from widespread use of echo-sounders during WWII.
The daily vertical migration of 100s of millions of tons of animals on the order of 10,000 body lengths is the greatest animal migration on Earth!
Zooplankton & krill (cm-scale) migrate a few hundred meters, fish on scale of 10 – 15 cm migrate 100s m

16. Deep Scattering Layer
a layer in the ocean consisting of a variety of marine animals
discovered through the use of sonar, as ships found a layer that scattered the sound and was thus sometimes mistaken for the seabed
sometimes called the "false bottom". It can be seen to rise and fall each day in keeping with diel vertical migration.

18. History of Midwater Science
Praya dubia: 30 – 50 m long siphonophore, one of the largest animals on Earth.
The discovery that such giant siphonophores are dominant mesopelagic predators followed from advances in midwater ROVs and photography in
1980/90s.