Question

The Arctic cod is a small forage fish that is a very important part of the food web. It eats mostly zooplankton and lives water between -2 and 0°C due to a type of antifreeze in its blood. How does a warming climate and seas waters as well as ice melt impact the Arctic cod and the other organisms in the food web?
Responses
A As the water temperatures warm, the plankton increases, the cod increases and all of the higher level consumers also increase.As the water temperatures warm, the plankton increases, the cod increases and all of the higher level consumers also increase.
B As ice melts and temperatures increase, the polar bears decline so all other animal populations, including the Arctic cod, increase.As ice melts and temperatures increase, the polar bears decline so all other animal populations, including the Arctic cod, increase.
C The Arctic cod lives in a very small temperature range. If it begins to die out, the food source for the next level of consumers will be reduced.The Arctic cod lives in a very small temperature range. If it begins to die out, the food source for the next level of consumers will be reduced.
D The Arctic cod will eventually adapt to the changing water temperatures. Since there is plenty of food for the cod, its population should remain stable.

Answer 1

C

Reason: Arctic cod require very cold, ice-associated waters and have a narrow temperature tolerance. Warming and ice loss reduce their suitable habitat and change zooplankton communities, so Arctic cod populations are likely to decline. That reduces food availability for seals, seabirds, whales and other predators and can cascade through the food web (and may allow more temperate species to move in and alter ecosystem dynamics).

Why the others are wrong, briefly:
- A: Warming does not simply increase plankton and cod; plankton composition and timing change and cod are confined by temperature and ice habitat.
- B: Polar bear declines do not cause all other animals to increase, and Arctic cod are unlikely to increase as a result.
- D: Rapid warming and specialized physiology make quick adaptation unlikely; populations are more likely to decline or shift.