The Ocean Depths

Zones of the Ocean Epipelagic- Photic Zone (500- 650 ft) Sun, plants, photosynthesis, O2 Mesopelagic- Dim light, but no plants No photosynthesis 660-3000ft Deep sea- perpetually dark

Overturn- oxygen rich water reaches the bottom in the Atlantic (S Overturn- oxygen rich water reaches the bottom in the Atlantic (S. of Greenland) and just north of Antarctica Great Ocean Conveyer- regulates the Earth’s climate and replenishes oxygen to the deep sea.

The Twilight World- (the Mesopelagic) 3,000 ft- dim light Main thermocline- large temperature change Animals: Midwater ***have photophores = bioluminescence Zooplankton Copepods*** Siphonophores Krill *** Shrimps*** Comb Jellies Ostracods Larvaceans Amphipods Pteropods Chaetognaths Squids Jellyfish Vampire squid

Mesopelagic Fish: 1. Bristlemouth Most abundant fish on earth

2. Viperfish

3. Dragonfish

4. Hachetfish

Mesopelagic Adaptations Only about 20 % of food produced in the epipelagic makes it to the mesopelagic. 1. Small size: Hides easily and uses less energy 2. Large mouths- hinged extendable jaws (large teeth) Usually will eat anything that will fit in mouth

Non-migrators (couch-potato fish) Copepods and krill filter detritus and fecal pellets of epipelagic copepods. Fishes, shrimps, and squids: Ambush Predators Flabby, watery, flesh instead of muscle no swim bladder soft, weak bones no spines or scales

Blob Fish

Vertical Migrators Swim up at night to feed. Well developed muscles and bones Swim bladder for buoyancy Tolerate temperature changes Vertical Migration is important in transporting food into deep water This increases food supply in mesopelagic Non-migrators feed on migrators

4. Sense Organs tubular eyes- up or forward to increase field of vision yellow filters can distinguish natural light from bioluminescence lateral lines very large eyes = more surface area to collect light

5. Coloration and body shape Countershading- black backs and silvery sides Reduction of the silhouette Laterally compressed bodies reduce outline

Bioluminescence

6. Bioluminescence Counterillumination- light production that helps animal blend in with background light filtering down from the surface Most common color is blue and the 2nd most common color is green Light can be from photophores, special cells, glands, ink. Can be used in communication and to attract mates, vision, or to lure prey.

Oxygen Minimum Layer Gas exchange from atmosphere & photosynthesis 1,600 ft- O2 minimum layer

The World of Perpetual Darkness Bathypelagic- 3,000- 13,000 ft Abyssopelagic-13,000- 20,000 ft Hadalpelagic- 20,000 – 36,000 ft Fish have little color bioluminescence is used for attracting prey, communication, & courtship many are blind or have small eyes.

Life in the Darkness 5% of food makes it to deep water “Couch potato” fish Huge mouths and expandable stomachs Anglerfish use “lure” to catch prey

Anglerfish

Sex in the Deep Hermaphrodites- both sex organs Bioluminescence – attracts mates Pheromones- special chemical released to attract mates Male parasitism- anglerfish attaches to female for life

Living Under Pressure Lack of swim bladder is due to high energy cost of filling it under extreme pressure. Divides zones: deepest living fish is 27,000 ft. Pressure effects enzymes that control metabolism

Life in the Benthos Benthic animals have more time to find food and eat it. Slow decomposition of detritus Fecal pellets are an important source of organic matter. Slow growth but long life (Deep-sea gigantism)

Hydrothermal Vents Undersea hot springs associated with mid-ocean ridges Discovered in 1977 by Bob Ballard Tube worms (3.3 ft long) Clams (12 in) Mussels Shrimps Crabs Fishes

Chemosynthesis Seawater trickles down through the cracks in the crust, is heated and emerges at hydrothermal vents. Contains hydrogen sulfide (H2S) and other minerals Bacteria use H2S to make organic matter which is chemosynthesis When they crystallize they form black smokers and chimneys. Primary producer is chemosynthetic bacteria

Tube Worm The giant tube worm contains symbiotic bacteria Worms supply raw materials H2S is toxic to most animals but tube worm has special hemoglobin