Polar Seas: The Arctic & the Antarctic

Long Winter Nights w/o sunlight & zero degrees Celcius temperatures (even in

the summer months!)

Covered with ICE:

• The primarily environmental factor that delineates “polar” areas is ice – large parts of both the Arctic and Antarctic remain perpetually covered with ice.

• The ice is either PACK ICE (thaws away in the summer) or FAST ICE (permanent ice year-round).

Approximate distribution of fast and pack ice

FAST ICE

“Sea Ice,” although never more than a few meters thick, is critically important in polar regions because it:

(1) Is a solid physical structure to rest, breed and raise young (while being relatively predator free);

(2) Acts as a barrier to insulate seawater from atmospheric seasonal temperature changes.

North Pole – The Arctic

• An ice covered ocean surrounded by continents. The Arctic is NOT a continent!

• Fast ice common and water flow interrupted by land masses (thus low primary productivity area).

• The Bering Strait, Norwegian Seas, Greenland etc.

South Pole – The Antarctic

• An ice covered continent surrounded by ice covered seas. The Antarctic IS a continent!

• Sometimes called the (5th) “Southern” Ocean• Pack ice common and water flow not interrupted

by scatterings of land masses (thus very high primary productivity).

• Uninterrupted zone of ocean (current) travel

Marine Birds And Mammals In Polar Seas

– Strong contrasts exist between the north and south poles.

– The Arctic is an ice-covered ocean surrounded by continents.

– The Antarctic is a frozen continent surrounded by ice-covered seas.

Comparison of Arctic and Antarctic Oceanographic Features

The Arctic

– Phytoplankton productivity patterns at higher latitudes are marked by large swings between:

• long winters of essentially no productivity• short bursts of high summertime production

– These in turn feed relatively large consumers and lead to short food chains supporting large aggregations of marine mammals and seabirds.

The Arctic– Marine mammals and seabirds that cope with the

seasonal variability in their food supplies via extended fasting and long migratory excursions to lower-latitude waters in winter.

Generalized migratory patterns of large whales between summer feeding and winter breeding grounds. Northern and southern populations follow the same migratory pattern but do so 6 months out of phase with each other. Consequently, northern and southern populations of the same species remain isolated from each other, even

though both populations approach equatorial latitudes. Adapted from N. A. Mackintosh. Whales, Dolphins and Porpoises. University of California Press, 1966.

The Arctic

• Arctic Mammals– Several species of seals, including ringed,

harp, and hooded, breed on arctic fast or pack ice.

– These species all show a reduced level or complete absence of polygyny.

– Mating in the water is common.

Large male walrus displaying prominent tusks

© Corbis/age fotostock

The Arctic

Geographic distribution of the Atlantic (red) and Pacific (black) subspecies of

walrus, Odobenus rosmarus.

Benthic suction-feeding behavior of walruses used to capture buried bivalves

Hair-covered paws of a swimming polar bear

© Emily Veinglory/ShutterStock, Inc.

The Arctic• Arctic Mammals

– Polar bears have few specialized adaptations for efficient swimming and usually prey on ice seals.

– They endure prolonged seasonal fasts as the availability of food declines or when reproductive activities prevent foraging.

A polar bear mother and her twin cubs at

rest.

Courtesy of Captain Budd Christman, NOAA Corps

A polar bear mother and her twin cubs at rest

Courtesy of Captain Budd Christman, NOAA Corps

The Arctic

• Arctic Mammals

– Mysticete whales, among the largest animals on Earth, are filter feeders of crustaceans or small shoaling fishes.

– All mysticetes show reverse sexual dimorphism.• This may provide females with larger lipid stores to help offset

the energetic costs associated with rapid fetal growth and lactation.

The Arctic

• Arctic Mammals– Mysticete whales exploit these polar and subpolar

production systems with intensive summer feeding followed by long-distance migrations to low latitudes in winter months.

– Both mating and calving occurr in warm and often protected waters.

The Arctic

• Arctic Mammals

Pattern of latitudinal migrations of female gray whales through a

complete two-year reproductive cycle.

A gray whale showing baleen

© C. Allan Morgan/Peter Arnold, Inc.

Figure 14.25c

Skimming feeding behavior of bowhead whales

Adapted from Pivorunas, A. Sci Am. 67 (1979): 432-440.

Figure 14.25d

Engulfment feeding behavior of fin whales

The Arctic

Migratory route (white line) of the Northeast Pacific gray whale, with summer feeding

(red hatching) and winter breeding areas (pink)

indicated.

Courtesy of NASA

The Arctic

Two gray whales courting in their winter breeding lagoon.

© Francois Gohier/Photo Researchers, Inc.

The Arctic

The reproductive cycle of female gray whales (Eschrichtius robustus), including the

accompanying growth of fetus and calf during its period of dependency on the

female.

Adapted from Berta, A., and J. Sumich. Marine Mammals: Evolutionary Biology. Academic Press, 1999.

The Arctic• Arctic Mammals

• Arctic waters are inhabited, • or at least visited, by belugas,

narwhals, and killer whales.

• Belugas are medium-sized • whales with a very flexible • neck, small flippers, thick • blubber, and a stout dorsal • ridge used to break through • ice from below. They feed on

seasonally and locally abundant fishes and invertebrates, both in the water column and on the seafloor.

An arctic beluga whale, Delphinapterus leucas.

© Ryan Morgan/ShutterStock, Inc.

The Arctic• Arctic Mammals

– All narwhals possess a tusk that is actually an elongated upper tooth projecting through the lip.

– They feed mostly on polar and arctic cod, and sometimes dive to depths greater than 1000 m to feed on bottom fishes and midwater squid.

Two narwhals, Monodon monoceros (tusked male in foreground).

© David Fleetham/Alamy Images

A killer whale

Courtesy of NOAA

Transient killer whale attacking a Dall’s porpoise

Courtesy of Dr. Robin W. Baird, Cascadia Research Collective

• Other Arctic Inhabitants

Warm bodied seabirds and marnine mammals are able to out-compete fishes for the role of apex predator in polar seas

© Armin Rose/ShutterStock, Inc.

Hooded seals

© Fred Bruemmer/Peter Arnold, Inc.

Ringed seal

© jack stephens/Alamy Images

Harp seal pup

© AbleStock

Hooded seal with inflated hood

© Biosphoto/Bruemmer Fred/Peter Arnold, Inc.

Hooded seal with inflated nasal balloon

© Fred Bruemmer/Peter Arnold, Inc.

The Arctic

• Arctic Seabirds– Seabirds obtain their food from the sea, excreting

excess salt ingested during feeding with nasal salt glands.

– All species of seabirds are either • Charadriiformes (gulls, skuas, jaegers, terns, auks,

and puffins)• Procellariiformes (petrels, fulmars, and albatrosses)• Sphenisciformes (penguins).

The Arctic• Arctic Birds

– Only northern fulmars, ivory gulls, and Ross’s gulls consistently depend on arctic ice-associated prey in summer.

A northern fulmar, Fulmarus glacialis, in search of prey.

© David Woods/ShutterStock, Inc.

The Arctic

Tufted puffin pursuing prey underwater.

© Chris Gomersall/Alamy Images

A northern Fulmar

© David Woods/ShutterStock, Inc.

Antarctic prion

Courtesy of Tony Palliser

The Antarctic…It’s all about the Trophic Structure here

The Antarctic

– All Antarctic communities depend directly or indirectly on krill, Euphausia superba.

• E. superba is a 6-cm-long, 1-g, herbivorous crustacean that occurs in enormous swarms around much of the Antarctic continent.

– Vast shoals of krill probably support half the world’s biomass of seals, and a large proportion of its baleen whales and seabirds as well.

krill

krill

The Antarctic

Antarctic food web with krill, Euphausia superba, occupying a

central position on the second trophic level.

Inset: © Frank T. Awbrey/Visuals Unlimited

Food Web

The Antarctic• Antarctic Mammals

– Filter-feeding blue, fin, humpback, and minke whales occupy antarctic waters to feed on krill in summer.

Engulfment feeding behavior of fin whales and other rorquals.

Adapted from Pivorunas, A. Sci Am. 67 (1979): 432-440.

The Antarctic• Antarctic Mammals

– Today, blue, fin, and humpback whale populations still remain depleted as a result of the intense commercial whaling during the first half of the 20th century.

– With the larger whale species removed from antarctic food webs, numbers of smaller minke whales (most common whale here), Adelie penguins, crabeater and leopard seals, and fishes that also rely on E. superba have increased dramatically.

Japanese Whaling Vessel

The Antarctic

• Antarctic Mammals

– Crabeater seals, the most abundant seal on Earth, forage almost exclusively on E. superba, using their highly modified teeth as effective strainers.

– These monogamous seals spend the entire year on pack ice.

Crab Eater Seal

The Antarctic• Antarctic Mammals

– Weddell seals are found associated with openings in the fast ice that they maintain as breathing holes by constant abrasion with their teeth.

– They dive to 600 m for 80 minutes or more to feed on antarctic cod and other large bottom fish and squid.

A Weddell seal lingers near its preferred breathing hole.© Kim Westerskov/Alamy Images

Fin Whale

The Antarctic• Antarctic Birds

– Most polar seabirds:

• are found in the southern hemisphere, nesting at high latitudes during summer, often in enormous and crowded colonies

• leave to spend winter months at lower latitudes elsewhere.

The Antarctic• Antarctic Birds

– Antarctic prions feed by running/flying along the water’s surface and scooping krill with their modified bill.

Antarctic prion

Antarctic prion beak, showing the bill lamellae used for filtering krill.

Courtesy of Tony Palliser

Courtesy of Janet Hinshaw, University of Michigan, Museum of Zoology

The Antarctic

• Antarctic Birds– Adelie and emperor

penguins are abundant in antarctic pack-ice habitats.

An Adelie penguin on antarctic pack ice.

Courtesy of Michael Van Woert, NOAA, NESDIS, ORA

Figure 9.06a

Fnft: Emperor penguins

Courtesy of Michael Van Wort/ORA/NESDIS/NOAA

Some great shots!

• Frozen Waves (2008 coldest year on record)

• Green = algae

• Blue = frozen water (so fast there are no bubbles to lessen “color”)

• Other colors = sedimentation results