Chapter 19 Key Concepts

Polar ecosystems are influenced by strong seasonality, especially of ice cover, and a diverse phytoplankton assemblage fuels the polar food webs. Carnivores exert top-down effects; overfishing of carnivores has had strong effects on polar food webs.
Climate change is causing strong reorganizations of polar ecosystems, especially where warming waters are causing increased seasonal retreat of sea ice.
Arctic environments are characterized by cold seawater temperatures, seasonal changes in sea ice, and high productivity, which influences the subtidal benthos by deposition of organic matter.
High primary productivity of open-water phytoplankton and ice algae provide an abundant source of organic matter that is deposited on the seabed and subsidizes benthic communities.
Global climate change has had strong effects on Arctic environments, resulting in reduced summer sea ice, higher seawater temperatures, and a wide range of effects on the physiology, geographic ranges, and community structure of Arctic biotas.
Incursion of warmer waters into the Barents Sea and reduction of sea ice has led to major expansions of krill, capelin, and cod.
On a larger geographic scale, disappearance of Arctic ice from climate change interactions with typical ocean climate fluctuations may be causing much broader ecological effects on Atlantic food webs distant from the Arctic Ocean.
Krill occupy a central role in driving coastal Antarctic food webs: They interact with shifting sea ice and feed on algae, and they are consumed by a wide variety of predators.
Warming in the Southern Ocean, the sub-Antarctic southwest Atlantic Ocean, and the West Antarctic Peninsula is causing major declines of krill, some predators, and reorganizations of the Antarctic ecosystem.
The Antarctic shelf benthos are isolated from the rest of the ocean’s benthic fauna and have adapted to permanently cold waters.
The Antarctic shelf benthos is dominated by a diverse fauna with unusual elements and lacks shell-crushing predators, such as crabs and lobsters.
Global climate change is rapidly increasing sea-surface temperatures around the Antarctic Peninsula, perhaps making the fauna vulnerable to invasion by formerly absent predators.