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1

Features of polar waters

-Cold
-Rich in dissolved gases (dissolve better in cooler water)
-Rich in nutrients
-Weak thermocline
-Weak pycnocline (density gradient)
-Primary production light-limited

2

Biological differences between Arctic and Antarctic Oceans: macrobenthic diversity

-Arctic: low
-Antarctic: high (6 times higher than Arctic)

3

Biological differences between Arctic and Antarctic Oceans: endemism

-Arctic: low, benthos similar to cold-temperate Atlantic and Pacific
-Antarctic: extremely high (95% fish species)

4

Biological differences between Arctic and Antarctic Oceans: biomass

Arctic: low
Antarctic: High (10-100x higher at given depth)

5

Biological differences between Arctic and Antarctic Oceans: benthos characteristics

Arctic: typically infaunal species that feed in particulate organic matter suspended in the water or settled on the bottom
Antarctic: large numbers of epifaunal and infaunal species

6

Biological differences between Arctic and Antarctic Oceans: biotic disturbance

Arctic: high (many large mammals)
Antarctic: low

7

Why is the ice margin important in the Antarctic?

Important foraging area

8

What are macrobenthos?

Organisms living on, or in, the sea bottom which are larger than 1mm

9

Biological differences between the Arctic and Antarctic Oceans: biotic disturbance

-Arctic: biotic disturbance very high due to bioturbation of sediment and skeleton-crushing (durophagous predators)
-Antarctic: less disturbance and harder sediment

10

Physical differences between Arctic and Antarctic Oceans: ocean form

Antarctic: circumpolar ring
Arctic: almost enclosed by land

11

Physical differences between Arctic and Antarctic Oceans: current system

Arctic: transpolar current
Antarctic: circular currents that cause upwelling in the convergence zone

12

Physical differences between Arctic and Antarctic Oceans: river input

Arctic: high (low saline stratified surface + sediments)
Antarctic: None

13

Physical differences between Arctic and Antarctic Oceans: euphotic zone nutrients

Arctic: seasonally depleted
Antarctic: high all year round

14

Physical differences between Arctic and Antarctic Oceans: pack ice cover

Arctic: little seasonality - 90% in winter, 80% in summer, 3.5m thick
Antarctic:high seasonality - 50% in winter, 10% in summer, 1.5m thick, melted ice leads to high productivity

15

Physical differences between Arctic and Antarctic Oceans: continental shelves

Arctic: wide continental shelves, large river discharge, two shallow straits into Pacific and Atlantic Oceans
Antarctic: narrow, open to all oceans, exchange with deep ocean

16

Where is the convergence zone of the Antarctic?

A transition region of the Southern Hemisphere separating the Antarctic and sun-antarctic regions. Major area of upwelling so huge phytoplankton blooms

17

Physical differences between Arctic and Antarctic Oceans: temperature

Antarctic: waters coldest of anywhere in Earth (0 to -1.9 degrees Celsius)

18

Types of ice

Sea ice (pack ice): formed from saltwater freezing into base of pack ice
Ice shelf (continental ice sheet or glacier): formed on land from snow but extends into sea

19

Sea ice community features

Diatoms live within brine channels in sea ice - chlorophyll concentrations 1000x that of open surface waters in southern ocean
Provide a highly concentrated food source for grazing zooplankton in winter
As it melts in spring it provides a seed population of plankton for blooms along the ice edge - important grazing grounds

20

What is the word for organisms capable of growth and reproduction in cold temperatures?

Psychrophilic

21

Antarctic krill

Euphausia superba
Dominant herbivore in Antarctic pelagic ecosystem
Grow up to 6cm
Occupy all layers in the water column which makes them prey to surface, pelagic and benthic feeders
Whole food web based on them - form dense swarms covering miles

22

How to krill depend on sea ice?

Extensive winter sea ice means plentiful winter food from ice algae
Promotes larval recruitment, replenishing krill population

23

Krill versus Salps

Salps are free-floating tunicates which move and feed by pumping water through hollow gelatinous body.
They are the primary competitor of krill for phytoplankton, but can’t feed on ice algae.
In the absence of krill, salps can exploit spring phytoplankton blooms and undergo extensive population growth.
In years following low sea ice cover in winter, they reach high densities.
They can tolerate warmer water than krill

24

What is the benthic ecosystem dominated by in ice habitats

Suspension feeders - they are dependent on highly seasonal pulses of food from waters above

25

Benthos and ice scours

-Icebergs or hard pack ice scours the benthic species at the bottom
-High faunal mortality and skewed population structures result, with dominance of mobile secondary consumers
-At the regional scale, this promotes biodiversity and habitat heterogeneity

26

What grows where there is low ice disturbance?

Giant slow-growing sponges

27

What colonises after ice shelf collapse?

Fast growing ascidians

28

What is a polynya?

An area of persistent open water surrounded by sea ice.
Caused by upwelling of circumpolar deep water which is warmer and melts the sea ice.

29

Polynyas and Emperor and Adélie penguins

-Polynyas provide ideal conditions for early and intense phytoplankton blooms
-90% of these penguins are sited next to recurrent coastal polynyas
-Breeding success of Emperor and Adélie penguins depends on distance of breeding colony to open water foraging ground
-To adapt to the unpredictable length of foraging trips, there is great flexibility in chuck rearing/feeding