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Marine Biology > Lecture 10 - Polar Ecosystems > Flashcards

Lecture 10 - Polar Ecosystems Flashcards

1
Q

How North is the Arctic Circle?

A

66 degrees

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2
Q

Which is the enclosed ocean; the Arctic or the Antarctic?

A

The Arctic

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3
Q

Give the three pieces of land that surround the Arctic.

A
  • Siberia
  • Alaska
  • Northern Canada
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4
Q

Define the Arctic.

A

The extent of the midnight sun and the polar night.

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5
Q

Why is the Arctic described as the position oft he treeline?

A

North of the treeline is where it is too cold for trees to grow.

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6
Q

Where is the coldest place on the planet?

A

A mountain in Antarctica, goes down to -90

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7
Q

What is the range of winter temperatures at the coast of the Antarctic?

A

0 to -30 degrees

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8
Q

How much of the Earth’s surface can pack ice cover at its maximum extent?

A

13%

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9
Q

What is the dominant feature influencing both polar ecosystems?

A

Sea ice dynamics

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10
Q

In the Arctic, when is the

a) Maximum sea ice extent?
b) Minimum sea ice extent?

A

a) Maximum = end of winter; March

b) Minimum = end of summer, September

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11
Q

In the Antarctic, when is the

a) Maximum extent?
b) Minimum extent?

A

a) Maximum = November

b) Minimum = February

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12
Q

Give the three polar habitats.

A
  • Sea-ice realm
  • Pelagic realm
  • Benthic realm
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13
Q

How does sea ice form?

A
  • Once it begins to freeze, salt is excluded from the ice crystal in brine rejection.
  • Surrounding seawater becomes saltier and denser, and sinks.
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14
Q

What is the difference between first year and multi year ice?

A
  • First year ice contains pockets of brine that form channels within the ice where brine is collecting and dropping out of the bottom.
  • Multi-year ice; brine channels drop out and ice consolidates and becomes denser.
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15
Q

Describe primary production in polar environments.

A

Comes in short, sharp pulses.

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16
Q

Where in polar environments are there changes in seawater temperature?

A

Towards the edge of the environment

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17
Q

When do plankton peak in polar environments?

A

In the early spring

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18
Q

How much of the total annual primary production does primary production in the Arctic sea ice contribute?

A

Over 50%

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19
Q

True or false:

Production in first year ice is greater than multi-year ice.

A

TRUE.

This is true because there are more channels in first year ice.

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20
Q

What are sympagic species?

A

Ice-associated flora and fauna

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21
Q

What are the most common invertebrates in the Arctic sea ice?
How do they feed?

A

Calanoid copepods and amphipods.

Eat diatoms that sink to the sea floor upon ice melt.

22
Q

What temperature can sea ice bacteria and algae survive up until?

A

-25 degrees

23
Q

Describe how antifreeze proteins work.

A

Bind ice crystals as they start to form and lower the freezing point in thermal hysteresis.

24
Q

Describe the winter-spring transition in the Arctic

A
  • Sun rises a few hours a day from March to April
  • April-May, 24 hours of sunlight
  • Ice thins, forming more channels, and nutrients drop out, leading to blooms of phytoplankton.
  • Invertebrates then increase in abundance.
25
Q

Describe the peaks in algal blooms at

a) 70 degrees North
b) 75 degrees
c) Higher

A

a) 70 degrees = two peaks of algal blooms
b) 75 degrees = a single peak
c) Peaks become smaller

26
Q

How are calanoid copepods adapted to cope with seasonal pulses of primary production in the polar environments?

A

Overwinter with high lipid reserves.

Have a lipid sac which grows through primary production period.

27
Q

Give the three key calanus species in the Arctic.

A
  • C. hyperboreus; specialises in deeper parts of the Arctic.
  • C. glacialis; in the Arctic shelf
  • C. finmarchicus; in the Atlantic.
28
Q

What percentage of the total mesoplankton biomass in the Arctic is made up of Calanus species?

A

50-80%

29
Q

Describe reproduction of Calanus species in the Arctic.

A
  • Suppress metabolic rate in Winter.
  • Enough lipid reserve to form eggs before they feed, timing release of eggs with algal blooms.
  • Larvae have food to eat as soon as they hatch, but must grow quickly due to short summer period.
30
Q

In stead of Calanus, what occupies the primary consumer niche in the Antarctic?

A

Krill

31
Q

Ho many tonnes of krill are there in the Southern ocean?

A

500 million tonnes

32
Q

Describe the lifecycle of krill in Antarctica.

A
  • Begin life feeding on algae beneath the sea ice.

- In summer, leave the ice and form swarms with millions of individuals (feed by swimming upside down).

33
Q

Why are krill a keystone species in Antarctic ecosystems?

A
  • Key source of food for many other animals

- Release high levels of iron - Antarctic is iron-limited.

34
Q

Compare the differences in production in the Arctic and Antarctic environments.

A
  • Strong stratification of water column in Arctic due to high freshwater input, not in Antarctic.
  • Primary prduction nutrient-limited in Antarctic, but iron-limited in the Antarctic.
35
Q

What structures the benthos in polar ecosystems?

A
  • Ice scour
  • Effective at removing attached intertidal organisms
  • Holds environment in early successional stages.
36
Q

What is the polar benthos dominated by?

A

Suspension feeders such as crinoids and brittle stars

37
Q

What is the polar benthos dominated by?

A

Suspension feeders such as crinoids and brittle stars

38
Q

Describe the Antarctic benthos.

A
  • Modern skeleton-crushing predators e.g. sharks, rays, lobsters, crabs; rare, if not present. Too cold for them.
  • Slow-moving invertebrates, e.g. echinoderms, are the top predators.
  • Soft-bodied suspension feeders evolved in the absence of crushing predators.
39
Q

Describe an Antarctic invasion.

A
  • Crabs mostly lacking from Antarctica, but invasion of King Crabs into Antarctic shelf seas.
  • King crabs from warmer deeper waters migrating to shallow waters due to warming.
  • Could have ecological impacts, as benthic invertebrates are not evolved to protect themselves from crushing predators.
40
Q

Why are invertebrates slow moving in polar environments?

A

Aerobic capacity is low

41
Q

How can polar fish maintain aerobic scope for fast swimming?

A

They have more mitochondria.

42
Q

Why is gigantism common in polar environments?

A

They live much longer, due to slower growth rates and higher oxygen content.

43
Q

How many more times species does the Antarctic have compared to the Arctic?

A

1.5-6 times

44
Q

Why is there higher endemism in the Antarctic species?

A

Due to isolation of Antarctica from the rest of the world’s oceans.

45
Q

How did the Arctic benthos arise?

A

From invasions from the Pacific in the last 2 million years.

46
Q

How many species of marine fish are found in the Arctic marine waters?

A

240

47
Q

Name a commercially important species in the Arctic.

A

Arctic cod.

Uses ice revises to hide and avoid predation.

48
Q

What two groups of fish dominate the Antarctic?

A
  • Notothenoids (icefish)
  • Liparids
  • Do not have strong jaws for crushing
49
Q

Describe an adaption of notothenioids in the Antarctic

A

Lost heat shock proteins and haemoglobin due to stable temperatures and high levels of oxygen.

50
Q

Give some charismatic megafauna found in the Antarctic.

A
  • Leopard seals
  • Penguins
  • Walruses
  • Killer whales
51
Q

Give some charismatic megafauna found in the Arctic.

A
  • Polar bears
  • Migratory whales
  • Seals

Marine Biology (19 decks)

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