Lecture 5 - Pelagic Ecosystems

Question 1

What is the neritic / sublittoral zone?

Answer 1

In the continental shelf region.

Found adjacent to the shore (subtidal region), always flooded by water.

Question 2

How deep does the neritic zone go?

Answer 2

200m

Question 3

What percentage of the ocean surface is composed of the neritic zone?

Answer 3

8%

Question 4

What is the neritic zone characterised by?

Answer 4

Areas of high productivity; nutrient-rich areas.

Question 5

What percentage of the ocean’s surface is composed of oceanic zones?

Answer 5

92%

Question 6

What percentage of the entire Earth’s surface is composed of oceanic zones?

Answer 6

65%

Question 7

Give the 6 oceanic zones, from shallow to deep.

Answer 7

• Neustic zone
• Epipelagic zone
• Mesopelagic zone
• Bathypelagic zone
• Abyssopelagic zone
• Hadal zone

Question 8

What are the oceanic zones?

Answer 8

Deep water beyond the continental shelves.

Question 9

What is the neustic zone?

Answer 9

The surface centimetre of the water.

Question 10

Name two organisms that are adapted to live in the neustic zone.

Answer 10

• Jellyfish

- Portuguese man of war

Question 11

How deep is the epipelagic zone?

Answer 11

0-200m

Question 12

In which oceanic zone does the majority of primary production occur in?

Answer 12

The epipelagic zone

Question 13

How deep is the mesopelagic zone?

Answer 13

200-1000m

Question 14

What characterises the mesopelagic zone?

Answer 14

Dominated by predatory fishes.

Question 15

How deep is the bathypelagic zone?

Answer 15

1000m-4000m

Question 16

What other name is given to the bathypelagic zone?

Answer 16

Midnight zone

Question 17

How deep is the abyssopelagic zone?

Answer 17

4000-6000m

Question 18

Why do nutrients drop off in the North Atlantic during spring?

Answer 18

Because there are plankton blooms

Question 19

Why is a second plankton bloom seen in autumn in the North Atlantic?

Answer 19

Autumn storms pick up, and nutrients are recirculated.
Thermocline begins to break down.
Nutrients available for plankton growth.

Question 20

What does spatial heterogeneity mean?

Answer 20

An ocean water sample would be different according to wear you took it from.

Question 21

Describe sargassum.

Answer 21

• entirely pelagic
• not attached to the seabed
• seaweeds

Question 22

Give two species of sargassum.

Answer 22

• S. natans

- S. fluitans

Question 23

Describe the work of Rooker et al (2006).

Answer 23

• Questioned whether sargassum were underpinning the food web.
• Isotope analysis, evidence Sargassum is not primary producer.
• Possible primary producers: Cladophora and POM.
• Composition of fatty acids in tissue of organisms; POM profile matches higher trophic levels.

Question 24

Give four examples of forage fish.

Answer 24

• Herring
• Anchovies
• Capelin
• Menhaden

Question 25

What do forage fish feed on?

Answer 25

• Blooms of plankton via filter feeding

- Targeting of larger copepods

Question 26

Describe the migration of the North-American Eel.

Answer 26

Spend some time of their life in freshwater environments, from juvenile to adult stages.
Travel to Sargasso sea and spawn once, before dying.

Question 27

What is the largest fish on Earth, and its size?

Answer 27

Whaleshark.

Grow up to 12m.

Question 28

When did whalesharks originate?

Answer 28

60mya.

Question 29

In 2000, what was the whaleshark found to be feeding on?

Answer 29

Euphasiid krill, found in large patches in coral reef environments.

Question 30

Suggest a possible reason why whalesharks might spend a significant amount of their time near the surface.

Answer 30

Looking for celestial navigation cues

Question 31

Describe the diving behaviour of whalesharks.

Answer 31

Can dive up to 1000m, experiencing 20C temperature gradient.

Ectothermic – warm up at the surface, giving them a competitive advantage when they dive deep.

Question 32

How do whalesharks exploit resources?

Answer 32

Good at exploiting short-lived feeding events over a large scale, e.g. crab larvae of Christmas island, and krill off of Ningaloo.