Ch.4 Polar Communities (pt.2)

Why is primary production high in polar regions despite cold temperatures?

because nutrient availability is high and seasonal light + ice conditions support blooms of algae

What organisms dominate primary production in polar waters and ice?

diatoms (ice algae), especially large phytoplankton species

Why does thinner ice increase primary production?

it allows more light to penetrate, boosting ice algae growth

What makes Antarctic (Southern Ocean) waters nutrient-rich?

permanent upwelling brings nutrients to the surface

What is the role of North Atlantic Deep Water in Antarctic productivity?

it sinks in the North Atlantic, flows south for hundreds of years, and upwells near Antarctica bringing nutrients

What characterizes Arctic sea ice communities?

well-developed ice algae communities within and under sea ice

Why does Arctic sea ice support high algae growth?

thinner ice allows more light penetration

What happens when Arctic sea ice breaks up in summer?

it releases plankton into the water, fueling food webs

What organism is a key link in polar marine food webs?

krill (small shrimp-like zooplankton)

What do krill feed on in polar ecosystems?

diatom (phytoplankton) blooms

What is the structure of the polar marine food chain?

diatoms → krill → large predators

Why do whales migrate in the Southern Ocean system?

they feed in Antarctic waters during summer and migrate north to breed during winter

Which whales are commonly associated with Antarctic feeding grounds?

blue, right, and fin whales

What do penguins primarily eat in Antarctic waters?

krill

Why are penguin juveniles especially vulnerable?

they are highly dependent on krill, so low krill availability increases juvenile mortality

What is a key adaptation of crabeater seals?

specialized teeth that filter/strain krill from water

What do leopard seals eat?

penguins, crabeater seals, and also krill

What is the main prey of squid in Antarctic waters?

squid are major prey for sperm whales (squid eat other marine organisms including krill)

Why are sessile organisms often absent in shallow Antarctic seafloor areas?

ice scouring physically disrupts the seabed

What organisms are common in shallow benthic zones when ice is absent?

mobile species like sea stars, sea urchins, and nemertean worms

What organisms dominate deeper Antarctic benthic zones?

sessile organisms such as sponges, corals, and sea anemones

What is anchor ice mortality?

ice forms around organisms and buoyant ice lifts and kills them

What is unusual about many Antarctic ice fish?

they lack hemoglobin and red blood cells

Why can icefish survive without hemoglobin?

cold water holds more oxygen, and they compensate with large hearts, high blood volume, and dense capillary networks

What adaptation prevents ice formation in icefish blood?

antifreeze proteins

What caused the collapse of the whaling industry in the 1960s?

overfishing

What major regulation was introduced for Antarctic whaling?

a moratorium on commercial whaling in 1986

What fish species have been heavily impacted by commercial fishing?

mackerel icefish and Patagonian toothfish (Chilean sea bass), which have been overfished and unstable

When did krill fishing begin and what is it used for?

in the 1970s; krill are processed into fish meal

What is the Antarctic Treaty?

a 1959 agreement by 12 nations protecting Antarctica from war, development, and territorial claims

Does the Antarctic Treaty regulate the surrounding Southern Ocean?

no, it primarily applies to the continent, not the surrounding waters