L9 Ocean depths

Question 1

What are 5 regions of ocean depth?

Answer 1

Epipelagic - 0-200m
Mesopelagic - 200-1000m
Bathypelagic - 1000-4000m 
Abyssopelagic - 4000-6000m
Hadopelagic - 6000-11000m

Question 2

at what depth are continental shelves?

Answer 2

<200m

Question 3

Which is the deepest part of the ocean?

Answer 3

Mariana trench - 10,000m +

Question 4

general trend of biomass from shallow to deep

Answer 4

shift in biomass so reduced food availability and lack of photosynthesis. From 1000-10,000m plankton biomass is small and reduces gradually

Question 5

How is deep water formed?

Answer 5

Deep water is formed when temperate water moves to poles, gets colder and denser so it sinks. Moves along thermohaline conveyor belts.

Question 6

4 properties of the deep ocean

Answer 6

Oxygen rich
Temp drops from 30-1000m, then stays low
Constant environment
Constant density

Question 7

Where is the oxygen minimum zone?

Answer 7

in the mesopelagic
plants at surface produce O2, die and sink to mesopelagic where bacteria decompose them, using up O2. Allochthonous system (C generated elsewhere).
Only 1-3% of productivity reaches ocean floor.

Question 8

What are barophilic animals and how are they affected by pressure?

Answer 8

Pressure loving animals
Have pressure resistance proteins so evolved to be more efficient under pressure.
Pressure affects protein structure,death on decompression can be caused by metabolic disturance.

Question 9

General trend with light in the ocean

Answer 9

Irridiance decreases with depth

Blue light present as it is reflected so ocean appears blue

Question 10

What is the general trend of macrofauna diversity and depth?

Answer 10

Declines with depth.
Deep water is a homogeneous environment so species have a vast range. Shallow water is much less homogeneous and more competition with smaller ranges.

Question 11

Why may chondrichthyes mainly found in shallow water

Answer 11

Must be barrier preventing them going deeper. Rely on lipids for buoyancy so need a large food supply.

Question 12

What are some mesopelagic species?

Answer 12

Crustaceans, Zooplankton - present in huge groups. Often bright red.
Blue light is often the only available light, so red light cannot be reflected so they are effectively invisible.
Squid, many species
Fish - Bristlemouth and lanternfish dominate. Also Lancelet fish common

Question 13

Deep pelagic fish

Answer 13

Fish adapted to the very dark, only light available is from bioluminescence. Specialized for low energy lifestyle.
Tadpole fish have huge lateral line pores, with many neuromasts.
Deep fish often very flabby, little muscle.
Typically scavenging species, wait for food to fall down
DOM and POM all used in shallower waters.
‘Benthopelagic’ - use both habitats, olfactory regions in brain highly developed.

Question 14

Describe a significant C shift

Answer 14

Diurnal vertical migration
Bristlemouth and benthotomids?? Shallow at night when predators aren’t a threat, then migrate to 200m each day.
Largest migration, many phyla . 1000 million tonnes

Question 15

What adaptations might species have for a vertical migration?

Answer 15

Well developed bone structures and muscles for much swimming.
Swim bladders - open, for rapid depth changes. use lipids instead to control buoyancy at constant depth.
Active, visual predators with large eyes and large mouths.
Photophores

Question 16

What are characteristics of non migratory species?

Answer 16

No swim bladders - use lipids instead
Weak bones and flabby muscle. Sit and wait predators.
Small body
Red colour as in Krill - although some predatory species can emit red light to show up krill.

Question 17

What adaptations might deep water organisms have for camouflage?

Answer 17

Some anglerfish are jet black, and don’t illuminate themselves.
Refractive index matching that of the water - for all body tissues so makes body completely transparent.

Question 18

What is a light producing organ and describe its structure

Answer 18

Photophore
Luciferins are oxidised by luciferases from either EK tissue or symbiotic bacteria.
Pigment coat around outside, covering a cell mass. Lantern in centre of cell mass. Outside has Lens and reflective ring.

Question 19

What functions does bioluminescence have?

Answer 19

Ventral bioluminescence hides silhouette from below
To hide organism - eg mesopelagic shrimp, amount of ambient light is directly proportional to the light produced.
Startle predators, escape from predators, lures, species recognition.

Question 20

Describe a mesopelagic vision strategy

Answer 20

Mesopelagic species can have v large eyes
eg Barrel eyes in Micropinna, Sometimes have 2 lenses in different directions.
Bog upwards lens projects light onto the main retina, and the small lateral lens - secondary retina. Gives 2 fields of view.
Deep pelagic - V poor visual capabilities

Question 21

What are some meso and deep pelagic prey handling adaptations?

Answer 21

mesopelagic - Efficient predators of animals of smaller sizes, big recurved teeth, large eyes.
Deep pelagic- Smaller eyes, sit and wait, relatively small fish