Chapter 16 The Ocean Depths

1. Chapter 16 The Ocean Depths

2. Life in the mesopelagic and deep sea is linked to plankton and light intensity in the water.

3. Nightly Migrations ~11 cm/sec (~4 BL/sec)

4. Animal Adaptations in the Mesopelagic Mid-water Realm Vertical Migrations of Animals Diel (daily) vertical migrations: cycle is coupled to downwelling light (the ‘Zeitgeber’ or ‘time-giver’)

5. 10 Z (m) 200 DAY NIGHT DAY Three kinds of migrations... New moon Full moon Nocturnal migrations

6. 10 Z (m) 200 DAY NIGHT DAY Three kinds of migrations... Twilight migrations

7. 10 Z (m) 200 DAY NIGHT DAY Three kinds of migrations... Reverse migrations

8. Why vertically migrate? • Reduce light-dependent mortality • Metabolic advantage • Light damage avoidance • Minimize horizontal advection (use deep counter-currents) • Prevent over-grazing • Maximize genetic exchange • Minimize competition

9. In the end, it’s all about fitness… Cumulative risk from predation must be balanced by energetic benefit going to reproduction. ‘better hungry than dead’

10. Oxygen Minimum Layer

11. Torres et al. Reduced with depth

12. Tuna Vent fish Measured at 10 C Fish activity decreases with depth

13. Theusen and Childress Only visual predators show this decrease in activity

14. Oxygen binding capacity of OMZ animals

15. Summary of Low oxygen adaptations Reduced oxygen consumption with depth Results in reduced athleticism Oxygen binding high

16. Mesopelagic Crustaceans

17. Photophores Specialized light structures that make “living light” or bioluminescence.

18. Typical Mesopelagic Fish

19. Rectangular midwater trawls used to collect mesopelagic organisms. Net has remote control to open only at certain depths.

20. As more shallow fish are over fished other deeper fish like this black scabbord fish are being caught.

21. Adaptations of Vertical migrators like the Lanternfish on left and non-migrators like dragonfish on right. • Well developed muscles and bones • Swim bladder of air or fat • Withstand extreme temperature changes

22. Viperfish Large hinged jaw that can accommodate large prey

23. Many non-migrators like this Rattrap Fish eat the more muscular migrators because they have more protein!

24. Special Eyes Tubular eyes like this midwater bristlemouth fish, with acute (great) upward vision.

27. Coloration and Body Shape • Midwater predators rely on sight. • Midwater prey cannot afford energy cost of swimming fast, spines, or scales so they… • Camouflage with countershading (dark on top, light bottom or sides) • Transparency = see through them (in upper mesopelagic – jellies, shrimp, etc) • Reduce the silhouette (bioluminescence on bottom) With blue-green light they control!

28. Value of Photophores Photophores on lower or ventral surface makes the silhouettes hard to see when they are viewed through water.

29. Bioluminescence • Living light is used for… • Counterillumination to mask silhouette • Escape from Predators with confusing light • Attract or see prey • Communication and Courtship

30. Typical Characteristics of deep-sea pelagic fish

31. Comparing mid-water and deep-water fish -

32. Living under pressure • Tremendous pressure of 1,000 atmospheres or 14,700 psi • Tough to visit and bring fish back alive • Metabolism affected by pressure • Molecular adaptations to allow enzymes to work under extreme pressures.

34. Sex in the Deep Sea • Finding mates is a problem in the dark • So animals use… • Bioluminescence • Chemical signals • Hermaphroditism • Male Parasitism

35. Benthic Fish

36. Nature of Life in Deep-Sea Benthos Reduced eyes or are completely blind (Live in complete darkness) Huge mouths to eat prey larger than themselves (Scarce food -less than 5% from higher waters) No vertical migrations to richer surface waters (small to reduce metabolic demands; flabby muscles, weak skeletons, no scales, and poorly developed respiratory, circulatory, and nervous systems)

37. Nature of Life in Deep-Sea Benthos Slow Pace(Save Energy) Low Temp and High Pressure(slow pace) Live Long and Large(up to 100 years) Produce fewer larger eggs(a lot of food for larva) Dominated by Deposit Feeders(eat marine snow)

38. Summary

40. Amount of nutrients at different depths is controlled by photosynthesis, respiration, and the sinking of organic particles. Nutrients are recycled but sink!

41. The deep currents are part of the great ocean conveyor. Small variations in the conveyor produce big changes in weather patterns around the world (El Nino). Large changes create ice ages.

42. Deep water originates at the cold surface at the poles. Cold water sinks and spreads out along the bottom.

43. Vampire Squid

47. Hydrothermal Vent Tube Worms

48. Deep-sea Hydrothermal vents harbor rich communities. The primary production that supports these communities comes from microbial chemosynthesis, not photosynthesis. Tubeworms have symbiotic bacteria in them that take the hydrogen sulfide or methane from vents, or dead bodies and make energy rich molecules to feed the worms!

49. A Review of Abiotic Properties of the Deep Sea metazoans per 100 m3 10-2 100 102 104 0 2 bumps 1000 2000 Z (m) 4000 8000

50. A Review of Abiotic Properties of the Deep Sea metazoans per 100 m3 10-2 100 102 104 0 2 bumps 1000 2000 Z (m) 4000 8000