Lecture 5 - Pelagic Ecosystems Flashcards

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1
Q

What is the neritic / sublittoral zone?

A

In the continental shelf region.

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

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2
Q

How deep does the neritic zone go?

A

200m

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3
Q

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

A

8%

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4
Q

What is the neritic zone characterised by?

A

Areas of high productivity; nutrient-rich areas.

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5
Q

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

A

92%

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6
Q

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

A

65%

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7
Q

Give the 6 oceanic zones, from shallow to deep.

A
  • Neustic zone
  • Epipelagic zone
  • Mesopelagic zone
  • Bathypelagic zone
  • Abyssopelagic zone
  • Hadal zone
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8
Q

What are the oceanic zones?

A

Deep water beyond the continental shelves.

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9
Q

What is the neustic zone?

A

The surface centimetre of the water.

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10
Q

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

A
  • Jellyfish

- Portuguese man of war

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11
Q

How deep is the epipelagic zone?

A

0-200m

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12
Q

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

A

The epipelagic zone

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13
Q

How deep is the mesopelagic zone?

A

200-1000m

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14
Q

What characterises the mesopelagic zone?

A

Dominated by predatory fishes.

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15
Q

How deep is the bathypelagic zone?

A

1000m-4000m

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16
Q

What other name is given to the bathypelagic zone?

A

Midnight zone

17
Q

How deep is the abyssopelagic zone?

A

4000-6000m

18
Q

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

A

Because there are plankton blooms

19
Q

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

A

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

20
Q

What does spatial heterogeneity mean?

A

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

21
Q

Describe sargassum.

A
  • entirely pelagic
  • not attached to the seabed
  • seaweeds
22
Q

Give two species of sargassum.

A
  • S. natans

- S. fluitans

23
Q

Describe the work of Rooker et al (2006).

A
  • 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.
24
Q

Give four examples of forage fish.

A
  • Herring
  • Anchovies
  • Capelin
  • Menhaden
25
Q

What do forage fish feed on?

A
  • Blooms of plankton via filter feeding

- Targeting of larger copepods

26
Q

Describe the migration of the North-American Eel.

A

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

27
Q

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

A

Whaleshark.

Grow up to 12m.

28
Q

When did whalesharks originate?

A

60mya.

29
Q

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

A

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

30
Q

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

A

Looking for celestial navigation cues

31
Q

Describe the diving behaviour of whalesharks.

A

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

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

32
Q

How do whalesharks exploit resources?

A

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