1. Epipelagic environment Upper pelagic –Surface to 200 m –Neritic Over continental shelf –Oceanic Beyond the shelf Correlates to the photic zone –Most of the primary production –Phytoplankton –Zooplankton

2. Adaptations Staying afloat –Increased drag Increase surface area Higher SA/V ratio with small size –Increased buoyancy Lipids Gas filled floats / bladders Lighter ionic concentrations

3. Simplified food web –Little loss of energy… more efficient –Feeds other ecosystems …in reality is much more complicated…

4. …Where does it all go?

5. Habitats at depth Below the Epipelagic –Beyond the high light penetration –Depths > 200m Pelagic zones Benthic zones –Bathyl slopes 300-2000m –Abyssal bottoms Ave 4000m –Hadal trenches 6000-11000m

6. Mesopelagic Mid-water organisms are less abundant vs. Epipelagic Examples: zooplankton (krill & copepods); squid; midwater fishes Living within a gradient of decrease: temp., food, & light –Some light, but not enough to sustain 1 0 production Only about 20% of epipelagic food supply sinks to provide at this level –Many have adapted to make their own light Photophores (light organs) –Bioluminescence –See, be seen, then hide again Fig. 16.1

7. Many midwater critters exhibit gradients of red colors. Why? How far does light penetrate? Of different wavelengths? How will red pigment appear in an environment absence of red light wavelengths? Fig. 16.2

8. Many midwater predators (fish & inverts) are also prey E.g. Photophores on squid – why the distinct patterns? –Interspecific & Intraspecific communication –Protection & defense – counter shading, disruptive colorations –Startle / confuse predators Fig. 16.4

9. Countershading and counterillumination Camouflage by light and depth Transparency Reduction of silhouette More important in mesopelagic than epipelagic because it is one of their only defense adaptions Protection from above and from below –Darker dorsal patterns blend in with dark below –Lighter ventral blend in with light above

10. (a & b) Appearance of prey w/out photophores - silhouettes on a light background (as seen from a predator below) (b) blurriness caused by water (c & d) Appearance of prey with photophores - silhouettes are broken up against the background Fig. 16.15

11. Tubular eyes & “double vision” Tubular eyes provide greater acuity vision (binocular); but this would limit lateral vision. To compensate, extra lateral retina allows directional and lateral vision. Fig. 16.12

12. General diversity is portraid by relatively small size. Why? Midwater fish generally have comparatively large mouths. Why? Limited food supply Hinged jaws, lots of teeth, and unspecialized diets…can’t afford to be picky or pass-up a potential meal Fig. 16.6

13. ViperfishRattrap fish Hinged, protrusible jaws to accommodate larger prey Fig. 16.10

14. One of the most numerous in the mesopelagic –Lanternfishes & Bristlemouths Feed at upper depths –feed at night –Safer from predators Non-migrators: –Reduce cost…energy conservation Fig. 16.9

15. Oxygen Minimum Zone Another rapid decrease below photic zone because: Less mixing with surface Less O 2 produced Only have respiration Below the OMZ the amount of food drops greatly, therefore less respiration Fig. 16.18

16. Deep Sea Even less resources –Light, oxygen, DOM, food Only about 5% of food makes its way from photic zone to the deep Energy saving adaptations –Less developed muscles, skeletons, & organ systems –Most consumption goes into growth first, reproduction later

17. Compare the bristlemouths of meso vs. deep sea… Smaller eyes, less muscle, fewer light organs, less developed nervous and circulatory systems –…weaker bones, poorly developed swim bladder Fig. 16.20

18. Deep-sea Angler fishes: large mouth to take advantage of the limited prey, and a specialized “lure” Fig. 16.19

19. Fig. 16.21

20. Fig. 16.27

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22. Hydrothermal Vent communities Deep-sea vents are rich –Supported by chemosynthetic microbes –Seep hydrogen sulfide (H 2 S) and methane (MH 4 ) –Up to 120 o C Fig. 16.28

23. Riftia tubeworm Plume (gill) absorbs H 2 S and CO 2, pumped in blood where it is converted to food by symbiotic bacteria & extremophiles via chemosynthesis Fig. 16.29