Ocean Depths

1. Ocean Depths Chapter 16

2. The Ocean Depths • “Inner space” it has been called. Dark and cold, inhabited by bizarre, fearsome looking creatures, it is a little reminiscent of the outer space of science fictions movies. • Tremendous pressures, perpetual darkness • This is the Deep ocean

4. Oceanic Zonation – upper layers • The ocean depths include a number of distinct habitats • The uppermost layer is the epipelagic zone. This is roughly equivalent to the photic zone. (surface – 200 m) • Beneath the epipelagic is the mesopelagic zone – or the middle pelagic – light still penetrates, but not enough for primary productivity. This layer is sometimes called the twilight zone (200 m – 1000 m)

5. Oceanic Zonation – lower layers • Beneath the upper layers of the epipelagic and the mesopelagic we find the lower layers of the ocean – truly the deep ocean • The bathypelagic zone (1000 m – 4000 m ~ 2.5 miles) is a world of perpetual darkness • The conditions of life in the deep pelagic environment change very little. Not only is it always dark, it is always cold: 35 degrees F……salinity 35 ppt. • Below the bathypelagic there is the abyssopelagic zone (4000 m – 6000 m ~ 4+ miles) • Below the abyssopelagic zone exists the deepest locations on earth, the hadopelagic zone (6000 m – 11000 m ~ 4+ to 7 miles) • The deepest place on earth is at the Mariana Trench; Challenger Deep in the Pacific ocean (10,991 m / 36,061 ft) • Mt. Everest by comparison – the highest point on earth, has a height of 29,035 ft.

6. Mariana Trench: Challenger Deep in the Pacific ocean 10,991 m / 36,061 ft Trieste

7. Topography and Bathymetry

8. Oceanic Zonation

9. Life Down Below • Deep-water organisms depend on the surface not only for food, but also for oxygen. If the ocean were stagnant, the oxygen below the surface would quickly be depleted by respiration and animal life. • The thermohaline circulation / the great ocean conveyer constantly replenish the supply of oxygen to the deep sea • Oxygen still becomes depleted in some places though

10. Oxygen Minimum Zone (OMZ) • In many places, mid-water organisms have to deal with a shortage of oxygen in the water • Oxygen enters the water in two ways: • Gas exchange with atmosphere (dissolved gasses) • Photosynthesis • OMZ – 500 m

11. The oxygen minimum zone: ~ 500 m

12. Animals of the Mesopelagic • Photosynthetic organisms cannot exist in the mesopelagic – too dark to total darkness • Zooplankton (Krill and copepods, shrimps) • Squids, octopus, fish (usually small) • Common adaptation of mid-water animals • Photophores ~ light organs • bioluminescence

16. Some typical deep sea bottom fish

17. Sense Organs • To help them see in the dim light, mid-water fishes characteristically have eyes that are not only large, but unusually sensitive. • Large, light-sensitive eyes also occur in squids, shrimps, and other groups • Some mid-water fish have developed tubular eyes, a complex visual system that is almost like having two pairs of eyes

18. Photophores

20. Barreleye (Macropinna microstoma)~ 800 m Clear forehead Tubular eyes capped by green lenses nostrils

21. Bioluminescence • Most midwater animals have evolved an even more effective way to mask their silhouettes. • Their bioluminescent photophores, found mostly on their ventral side, produce light that breaks up the silhouette and helps the animal blend in with the background light filtering down from the surface: counter illumination.

22. Counterillumination

23. Photophore arrangement

24. Matching background light intensity

25. Giant deep sea amphipod

30. Sex in the Deep Sea • Food is not the only thing that is scarce in the deep sea • In such a vast, sparsely populated habitat, finding a mate can be difficult • Hermaphrodites • Bioluminescence • Pheromones • Male parasitism (anglerfishes ~ Cryptopsaras Ceratias) • Male bites into much larger female, male’s modified jaws fuse with the female’s tissue. Their circulatory systems join, female nourishes the male

31. Male Parasitism (The Anglerfish)

35. Hydrothermal vent system

36. Hydrothermal vent communities are based on chemosynthetic prokaryotic organisms

37. Anatomy of giant tubeworm: The chemosynthetic symbiosis

38. Reflection • So…….animals called corals share a mutalistic symbiotic relationship with zooxanthellate dinoflagellate protists in which they utilize each others byproducts • And here we have animals – tubeworms, fish, crustaceans, mollusks, etc. – sharing a mutualistic symbiotic relationship with extremophile archaebacteria in which they utilize each others byproducts…… • Amazing…… • Light energy + photosynthetic protist + animal = incredibly beautiful marine life in otherwise nutrient poor environments • Inorganic and thermal energy + chemosynthetic prokaryotes + animal = incredibly strange marine life in an otherwise extremely cold, dark, highly pressurized, and desolate place

39. The end