Chapter 19 Polar Communities

How do the Arctic and Antarctic differ? Especially with regard to food webs?

Summer ice cover about half winter cover in Arctic

Antarctic summer ice about 1/6th of winter

Key role of krill in Antarctic

Fish like capelin important and missing in Antarctic food webs

-Antarctic =

Diatoms still largely the base

No polar bears, but orca still present

Krill vital to the food web

Common prey

How do marine mammals find holes in the ice for breathing?

-push their noses through new ice?

Explain how freezing ice preserves nutrients for the next spring.

Phytoplankton (especially diatoms) major primary producer

Trapped in ice as it forms

Nutrient storage for next spring, along with increased sunlight

Big blooms in summer

-they get trapped in the ice, and when the ice thaws, the food is there

Explain the role of freezing ice in benthic pelagic coupling.

Sediment can also be frozen in ice

Thawing of ice deposits lots of nutrients to sediment

Strong benthic pelagic coupling

How do Antarctic benthic communities differ from other benthic communities we have studied?

Space can be limiting for benthos, depending on substrate. Strong hierarchies found in Arctic benthos, but not quite monopolies.

No keystone predator identified with the benthos, but krill considered keystone species.

Physical forces restrict what organisms are in the polar regions altogether. Within these communities, however, tolerance refuge lacking for many. However, a temperature barrier between the shelf and the deep

-colder at surface than in deep

-Tolerance greatly restricts what's there. But the organisms with in polar communities not really a tolerance refuge.

Disturbance isn't gonna suppress a competitor.

-No competitive monopolies- rsp doesn't apply

Explain how climate change has affected Adelie and chinstrap penguins. Go step by step including ice, diatoms, krill larvae and the penguins. Why are gentoo penguins not affected?

- climate change = increased temperature -> less ice = less krill

- Less krill = less food for penguins

-Gentoo penguins are not affected because they are less reliant on krill

Provide examples of overharvesting.

-Stellar sea cow?

European populations of gray whale?

Explain how PBDE and PCBs can concentrate in polar regions. How do these compounds affect the animals? DO they biomagnify?

-The higher an organism feeds in the food web, the more toxins it can accumulate

PCBs Evaporate and carried to polar regions come back to earth with snow, etc. Stepwise toward higher latitudes.

Air currents can concentrate PBDEs in polar regions

-Some biomagnify

-can affect reproduction and immune system

Be sure to explain how these communities do or do not follow the rocky shore paradigm.

rsp doesn't apply

-Toleracne greatly restricts whats there. But the organisms withing polar communities not really a tolerance refuge.

-Disturbance isn't gonna suppress a competitior.

-Space can be limiting for benthos, depending on substrate. Strong hierarchies found in Arctic benthos, but not quite monopolies

No keystone predator identified with the benthos, but krill considered keystone species.

Physical forces restrict what organisms are in the polar regions altogether. Within these communities, however, tolerance refuge lacking for many. However, a temperature barrier between the shelf and the deep

Be sure to be able to discuss the relative importance of top-down and bottom-up factors in regulating these communities

-bottom up = prob ice and krill

-polar bear mostly eat seals

-polar bears and orcas are apex predators

-no polar bears in antarctica but orcas still present