Below the Surface Abiotic Factors Affecting Deep Sea

Below the Surface

Abiotic Factors Affecting Deep Sea Organisms 1. Oxygen Levels Thermohaline circulation: Where water is cold and salty, it sinks, pulling oxygen into the deep sea (Greenland & North Antarctica)

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)

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

Deep-sea environments

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

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

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

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

• difficult to find mates • ex. Parasitic male!

Abyssopelagic: ex. Rat Tails

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

History of mid-water science • Discovery followed from widespread use of echosounders during WWII. • The daily vertical migration of 100 s of millions of tons of animals on the order of 10, 000 body lengths is the greatest animal migration on Earth! • Zooplankton & krill (cmscale) migrate a few hundred meters, fish on scale of 10 – 15 cm migrate 100 s - 1000 m

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.

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 1980/90 s.