3 Although the polar regions and seas are cold, a great variety of conditions exist in both the Arctic and Antarctic. Towards the North and South Poles the cold is intense but at their margins the climate can be almost temperate and a great deal of life exists at these margins. The ice can take many colours and hues including white, grey, blue and turquoise. It can form huge mounds as icebergs or lie flat as a vast sheet covering the surface of the water. High winds in the polar regions can also cause huge waves and blistering storms but there are also periods of calm and tranquillity. In the summer, the polar regions have 24 hours of sunlight but in the winter, there are months of darkness. ARCTIC & ANTARCTIC REGIONS The Antarctic (Southern) Ocean surrounds the Antarctic continent. The Antarctic region is defined by a line where cold Antarctic waters meet and sink below warm northern waters – this is called the “Antarctic Convergence”. The Arctic, however, is more complicated because it includes land masses that stretch into temperate latitudes. Arctic life does not exist above a mean upper temperature limit of 10°C (50°F). Thus, the boundary is a meandering line that circles the top of the northern hemisphere. Important! The Antarctic ice-cap contains 30 million cubic km (nearly 70%) of the world’s freshwater. It covers 98% of the continent and is nearly 5 km (3 miles) thick in places. In comparison, the Greenland ice-cap contains just 2.5 million cubic km of water.
4 7. POLAR SEAS ARCTIC AND ANTARCTIC DIFFERENCES In spite of both the Arctic and Antarctic having cold, dark winters and a large amount of ice, they are different places with very different characteristics: The Arctic: A frozen ocean surrounded by the land masses of North America, Greenland and Eurasia The Arctic Ocean is colder than the Antarctic Ocean The Arctic is significantly warmer than Antarctica Land animals can cross the ice sheets during the winter Antarctica: A continent of rock with a thick ice-cap surrounded by the Antarctic Ocean Antarctic Ocean is warmer than the Arctic Ocean Antarctica is significantly colder than the Arctic Land animals cannot reach Antarctica because it is remote REFERENCES & FURTHER READING Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 5, DK Publishing Inc., (2001), ISBN 0- 7894-8265-7 Important! The key seasonal factor that governs animal behavior in polar regions is the growth and melting of sea ice. This either allows or prevents access to feeding and breeding grounds.
6 7.1.1 The Arctic The Arctic Ocean is small and is almost entirely covered by a layer of ice several meters thick (there is no rock). It is surrounded by the northern fringes of the great land masses of North America, Greenland and Eurasia. These land masses are extremely important because they affect the climate dramatically. Land absorbs much more of the sun’s radiation than ice, warming the rock, fresh water and the air itself. Moderate temperatures of 10°C (50°F) can be reached in the summer and only certain places like Siberia attain the intensely cold temperatures of -50°C (-60°F) in the winter. The Arctic has a variety of climates and habitats including a frozen sea, the ice-cap of Greenland, the forests of Scandinavia, and the Siberian tundra.
7 7.1 NORTH Greenland is somewhat analogous to the Antarctic plateau. It is high and cold and has glaciers streaming down to the sea. However, it is much smaller than the Antarctic plateau (10% of the area) and thus its impact is less. The coldest places in the Arctic are on the Greenland ice-cap and in Siberia, both of which are far from the warming effects of the ocean. In spite of the cold conditions, life exists in the Arctic. The Arctic Ocean is bordered by shallow continental shelves, fed by rivers and mixed by currents. In spring, phytoplankton (e.g. diatoms) blooms. Diatoms sustain the invertebrates that live within the sea ice. Copepods, which are a type of shrimp-like crustaceans, are a critical component of the marine ecosystem since they form the base animal of the Arctic food chain. They are the equivalent of the Antarctic krill and feed on phytoplankton. Numerous animals, in turn, feed on them. Other invertebrates found in the Arctic include: Periwinkles Bivalves Crabs Amphipods Sea Stars
8 7.1 NORTH Arctic animals are closely related to those of the northern Atlantic and Pacific oceans but may have certain adaptations to the cold. For example, periwinkles avoid ice crystals forming in their tissues by becoming dehydrated for the winter. They can then survive in temperatures as low as -15°C (5°F). A variety of sea mammals are found in the Arctic including pinnipeds (e.g. true seals such as harp seals and walruses) and cetaceans (bowhead whales, beluga whales, and narwhals). The largest predators in the Arctic are the polar bear, Arctic fox and humans. Polar bears hunt ringed seals, harp seals and beluga whales while Inuit people hunt a variety of animals including seals and whales for skin, blubber and meat. Inuit people also hunt the narwhal for their long tusks and their skin, an important source of vitamin C in the traditional Arctic diet.
9 7.1 NORTH 7.1.2 Melting Sea Ice A recent concern about the North Polar region is the rapid melting of the Arctic sea ice. The figure to the right illustrates the extent of the sea ice at the same time of year between 1979 and 2003. Indeed, some reports suggest that the ice is melting so quickly that Arctic summers could actually be ice-free by the middle of the 21 st Century Many scientists attribute this disturbing loss of ice cover to global warming. Global warming suggests that the planet is getting slightly warmer as a result of human activities, such as the burning of fossil fuels (e.g. oil, coal, wood). Burning fossil fuels releases gases, such as carbon dioxide, into the atmosphere. Carbon dioxide increases the atmosphere’s ability to hold heat which contributes to the planet warming.
10 7.1 NORTH Global warming is a contentious subject and two questions are often asked by sceptics: Is it really happening or are higher temperatures just normal fluctuation? If it is happening, is human activity the cause of it? An enormous amount of research has been carried out to answer these questions and much evidence has been gathered. The result is that most reputable scientists today are almost certain that global warming is indeed occurring, and that humans are the cause of it.
11 7.1 NORTH POTENTIAL EFFECTS Irrespective of whether humans are causing global warming, the effects of the melting ice can still be felt. Some of these effects include: (a) Rising sea level and flooding As ice enters the sea, the sea level may rise which can cause flooding in low-lying areas. (b) End of polar bears? The polar bear is a vulnerable species at high risk of extinction. Zoologists and climatologists believe that the projected decreases in the polar sea ice due to global warming will reduce their population by two thirds by mid-century. As the ice melts, the bears’ habitat decreases. Local studies show that 7 out of 19 subpopulations are declining or are already severely reduced. In the U.S., the Centre for Biological Diversity petitioned to list the polar bear as an endangered species under the U.S. Endangered Species Act in 2005. The U.S. Fish and Wildlife Service also formally proposed to list the polar bear as a threatened species on January 9, 2007. REFERENCES & FURTHER READING http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html - Arctic warming http://www.nasa.gov/vision/earth/environment/Arctic_Warming_ESU.html - Arctic warming http://news.bbc.co.uk/2/hi/science/nature/6610125.stm - Arctic ice melting http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_3974000/3974997.stm - Arctic ice melting http://www.msnbc.msn.com/id/6433717/ - Arctic warming http://www.bbc.co.uk/sn/climateexperiment/ - Global warming http://www.ncdc.noaa.gov/oa/climate/globalwarming.html - Global warming
13 7.1 NORTH POLAR BEAR The polar bear (Ursus maritimus) is native to the Arctic and is the world's largest land carnivore. Males are generally much larger than females. Adult males weigh 350–650 kg (772–1433 lb) and measure 2.5–3.0 m (8.2–9.8 ft) in length while adult females weigh 150–250 kg (331–551 lb) and measure 2–2.5 m (6.6–8.2 ft). Its skin is black and its fur appears white or cream. Thick blubber and fur insulate it against the cold. The bear has a short tail and small ears that help reduce heat loss, and a relatively small head and long, tapered body to streamline it for swimming. The polar bear is semi- aquatic and has adapted for life on a combination of land, sea, and ice. It is the apex predator within its range and feeds on seals, walruses and whales although it will eat anything it can kill.
14 7.1 NORTH ARCTIC FOX The Arctic fox (Alopex lagopus) is a hardy animal that can survive frigid Arctic temperatures as low as -58°F (-50°C) in the treeless lands of its home. The Arctic fox’s head and body is 46-68 cm (18- 26.75 in) long while its tail is 35 cm (13.75 in) long. Its weight is 3-8 kg (6.5-17 lbs). It has furry soles, short ears and a short muzzle which are important adaptations to the cold. Arctic foxes live in burrows and may tunnel into the snow to create shelter. Arctic foxes have white (sometimes blue-gray) coats that act as very effective winter camouflage. When the seasons change, the fox's coat turns brown or grey providing cover among the rocks and plants of the summer tundra. These colours help foxes effectively hunt rodents, birds and even fish. In winter, arctic foxes will follow polar bears and eat leftover scraps. Foxes will also eat vegetables when they are available. The fox's thick tail (brush) aids its balance and is also useful as warm cover in cold weather.
15 7.1 NORTH WALRUS Walruses (Odobenus rosmarus) are large marine mammals that are found in the north Atlantic & Pacific Oceans. Walruses are immediately recognizable by their prominent tusks, whiskers and great bulk. Adult Pacific males can weigh 2,000 kg (4,400 lbs) and are exceeded in size only by elephant seals among pinnipeds (marine mammals with flippers such as true seals, eared seals and walruses). Walruses reside near shallow oceanic shelves and spend a significant proportion of their lives on sea ice in pursuit of their preferred diet of benthic bivalve molluscs. They are relatively long-lived, social animals and are considered a keystone species in Arctic marine ecosystems.
16 7.1 NORTH HARP SEAL Harp seals (Phoca groenlandica) spend relatively little time on land and prefer to swim in the chilly waters of the North Atlantic and Arctic Oceans. These sleek swimmers feed on fish and crustaceans and can remain submerged for up to 15 minutes. Harp seals are 1.9 m (6.2 ft) in length and weigh 180 kg (397 lbs). Harp seals return each year to breeding grounds in Newfoundland, the Greenland Sea, and White Sea. Here, males fight for mates with sharp teeth and powerful flippers. After mating, females gather in groups to give birth. Born on the ice, young harp seals are famous for their white coats which are highly valued and have drawn hunters to the Newfoundland breeding grounds for centuries. In the last few decades, these grounds have become a scene of conflict between sealers and animal rights activists. Modern hunts are better regulated than in the past but the harp seal arguably remains the most commercially important seal with hundreds of thousands killed each year.
17 7.1 NORTH BELUGA WHALE Belugas (Delphinapterus leucas) are white whales and their unusual colour makes them one of the most familiar and easily distinguishable of all whales. Calves are born gray or brown and fade to white as they become sexually mature around five years of age. Belugas are comparatively small whales and are about 6.1 m (20 ft) in length and 1,361 kg (3,000 lbs) in weight. They have rounded foreheads and no dorsal fin, and distinctively flexible necks. Belugas are social animals that generally live together in small groups known as pods. They are very vocal with a diversified language of clicks and whistles. Belugas feed on fish, crustaceans and worms. They are common in Arctic Ocean coastal waters though they are also found in sub-arctic waters. Arctic belugas migrate southward in large pods when the sea freezes. Animals trapped by the Arctic ice are often prey to polar bears and killer whales.
18 7.1 NORTH NARWHAL The narwhal (Monodon monoceros) is a pale-coloured porpoise found in Arctic coastal waters and rivers. Narwhals are 6.1m (20 ft) in length and weigh 1,600 kg (3,500 lbs). In males, one of the narwhal’s teeth grows through the narwhal’s upper lip into a spear- like, spiral tusk up to 2.7 m (8.75 ft) long. Scientists are not certain of the tusk's purpose but it may be used in mating rituals to impress females or battle rival suitors. Females sometimes grow a small tusk of their own but it does not become as prominent as the male's. Narwhals are related to bottlenose dolphins, belugas, harbour porpoises and orcas. Narwhals travel in groups and feed on fish, shrimp, squid, and other aquatic fare. They often swim in groups of 15-20 but gatherings of hundreds or several thousand narwhals have been reported. These groups sometimes become trapped by shifting pack ice and fall victim to polar bears or Inuit hunters. Orcas also prey on narwhals in open waters.
19 7.1 NORTH SEA ANEMONE Sea anemones are simple animals (cnidarians) that are often attached to the sea bottom. Sea anemones have cylindrical bodies that are surrounded by upward-facing tentacles. The tentacles have stinging cells on them which kill prey and move the food into a sea anemone’s mouth. The mouth leads into the body cavity which digests the food. A continuous current of water through the mouth circulates through the body cavity and removes waste. Sea anemones are found in cold and warm waters. Many are colourful, and large species can be 1 m (3 ft) in diameter. PERIWINKLE The common periwinkle is a species of small edible sea snail and is a type of marine mollusc.
20 7.1 NORTH DIATOMS Diatoms are microscopic algae that can photosynthesize food using sunlight. They have cells walls that are made of silicon and often take beautiful shapes and forms. Along with other phytoplankton, they are the base of the food chain upon which zooplankton and other animals all ultimately depend. REFERENCES & FURTHER READING http://www.polarbearsinternational.org/ - Polar bears http://animals.nationalgeographic.com/animals/mammals/arctic-fox.html - Arctic Fox http://animals.nationalgeographic.com/animals/mammals/harp-seal.html - Harp seal http://animals.nationalgeographic.com/animals/mammals/beluga-whale.html - Beluga Whale http://animals.nationalgeographic.com/animals/mammals/narwhal.html - Narwhal
22 7.2 SOUTH 7.2.1 The Antarctic Antarctica is a continent which is covered with an ice-cap. At one time, it was the center of the super-continent Gondwanaland with South America, Africa, Australasia and India grouped around its perimeter. The surrounding Antarctic (Southern) Ocean is much larger than the Arctic Ocean. It is also much warmer because it is contiguous with the Pacific, Atlantic and Indian oceans (ice covers just 2.6% of it). Antarctica is completely isolated by the ocean which no land animals (even good swimmers) can cross. Antarctica is also much colder than the Arctic. This is because it is not significantly warmed by the great landmasses of South America, Australia or Africa which are too distant to have an effect. It is also surrounded by a recurring barrier of sea ice which grows out from the continent every autumn.
23 7.2 SOUTH Antarctica is also much colder because it has a comparatively high altitude. The average height of the continent is 2,500m (8,200 ft) (North America averages 720m (2,360 ft). As a result of the isolation and altitude, Antarctica is significantly colder than the Arctic and temperatures in the Antarctic can reach - 70°C (-95°F) or less. However, Antarctica’s climate and temperature is not uniform. Antarctica’s plateau, with a higher latitude and elevation above sea level is unrelentingly cold with mean temperatures of -40°C (-40°F) in summer and -70°C (-95°F) in winter. The plateau icecap receives almost no rain or snow and, because of the extreme cold, there is no moisture in the air. Thus, it is an icy desert where virtually no life survives. It is the driest place on Earth with all water “locked up” in ice. However, at the perimeters of the continent, on the coasts, it is much warmer. The mean temperature is 0°C (32°F) in the summer and -30°C (-20°F) in the winter. There is rain here and the winds are stronger.
24 7.2 SOUTH In spite of the cold conditions, life exists in the Antarctic Ocean. Many invertebrates are found in the Antarctic Ocean including: Krill Limpets Sea Stars Ribbon Worms Crustaceans Soft Corals Hydroids Sea Anemones Sponges In spring, phytoplankton (e.g. diatoms) blooms. Diatoms sustain the invertebrates that live within the sea ice. Krill (Euphausiacea spp.), which are shrimp-like crustaceans, are a critical component of the marine ecosystem since they are the base animal of the Antarctic food chain. Numerous animals feed on krill, including, fish, birds, crabeater seals and a variety of baleen whales (including the humpback, right, blue, sei, fin and minke whales). These whales take in huge mouthfuls of water and use hanging plates of baleen – a horny material made of keratin – in their mouths to sieve krill from the water. Antarctic krill (Euphausia superba) is opaque and pink in colour. It is about 6 cm (2.4 in) in length and feeds on phytoplankton (microscopic single-celled algae and plants). It is among the largest of the 85 known krill species. The total estimated weight of krill in the waters around Antarctica ranges from 100- 500 million tonnes. During certain times of the year, they congregate in swarms so dense and widespread that the swarms can be seen from space.
25 7.2 SOUTH Antarctic krill can live up to 10 years, an amazing longevity for such a heavily hunted creature. They spend their days avoiding predators in the cold depths of the Antarctic (Southern) Ocean, some 100 m (330 ft) below the surface. During the night, they drift up the water column toward the surface in search of phytoplankton. Alarmingly, there are recent studies that show Antarctic krill stocks may have dropped by 80 percent since the 1970s. Scientists attribute these declines in part to ice cover loss caused by global warming. This ice loss removes a primary source of food for krill, namely, ice-algae. In spite of the diversity of sea life, Antarctica has very few plants and no freshwater fishes, amphibians or reptiles. However, there are sea birds and sea mammals. Penguins are perhaps the most famous inhabitants of the Antarctic with several species found here including the emperor, gentoo, chinstrap and Adelie penguins. Crabeater seals are found in abundance – numbering in the millions. In spite of their name, they mainly eat krill. The two largest predators in Antarctica are the leopard seal and killer whale, both of which will hunt penguins and crabeater seals. REFERENCES & FURTHER READING http://en.wikipedia.org/wiki/Antarctica - Antarctica Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 5, DK Publishing Inc., (2001), ISBN 0-7894-8265-7
26 7.2 SOUTH 7.2.2 Ozone Layer Depletion WHAT IS OZONE? Ozone is a gas that occurs naturally in small amounts in the upper atmosphere (the stratosphere) and is made up of three oxygen atoms (O3). “GOOD” STRATOSPHERIC OZONE Ninety percent of the ozone in the atmosphere sits in the stratosphere, the layer of atmosphere between about 10-50 km (6.2-31.1 miles) altitude. The natural level of ozone in the stratosphere is a result of a balance between sunlight that creates ozone and the chemical reactions that destroy it. Ozone is created when the oxygen we breathe (O2) is split apart by sunlight into single oxygen atoms. Single oxygen atoms can re-join to make O2 or they can join with O2 molecules to make ozone (O3). Ozone is destroyed when it reacts with molecules containing nitrogen, hydrogen, chlorine, or bromine. Some of the molecules that destroy ozone occur naturally but people have created others. Ozone in the stratosphere absorbs most of the ultraviolet radiation from the Sun. Without ozone, the Sun’s intense UV radiation would sterilize the Earth’s surface. Ozone screens all of the most energetic, UV-c, radiation, and most of the UV-b radiation. Ozone only screens about half of the UV-a radiation. Excessive UV-b and UV-a radiation can cause sunburn and can lead to skin cancer and eye damage.
27 7.2 SOUTH Increased levels of human-produced gases such as CFCs (chlorofluorocarbons) have led to increased rates of ozone destruction, upsetting the natural balance of ozone and leading to reduced stratospheric ozone levels. These reduced ozone levels have increased the amount of harmful ultraviolet radiation reaching the Earth’s surface. When scientists talk about the ozone hole, they are talking about the destruction of stratospheric, “good,” ozone. Since “good” ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation, its destruction is a serious matter. “BAD” TROPOSPHERIC OZONE Although ozone high up in the stratosphere provides a shield to protect life on Earth, direct contact with ozone is harmful to both plants and animals (including humans). Ground-level, “bad,” ozone forms when nitrogen oxide gases from vehicle and industrial emissions react with volatile organic compounds (such as paint thinners). In the troposphere near the Earth’s surface, the natural concentration of ozone is about 10 parts per billion (0.00001 percent). According to the U.S. Environmental Protection Agency, exposure to ozone levels of greater than 80 parts per billion for 8 hours or longer is unhealthy. Such concentrations occur in or near cities during periods where the atmosphere is warm and stable. The harmful effects can include throat and lung irritation or aggravation of asthma or emphysema. Thus, in the lower atmosphere (the troposphere) near the Earth’s surface, ozone is created by chemical reactions between air pollutants from vehicle exhaust, gasoline vapours, and other emissions. At ground level, high concentrations of ozone are toxic to people and plants.
28 7.2 SOUTH WHAT IS THE OZONE HOLE? The ozone hole is a region of exceptionally depleted ozone in the stratosphere over the Antarctic that occurs at the beginning of the southern hemisphere spring (August–October). Satellites provide daily images of ozone over the Antarctic region. The image (on the right) shows the very low values centered over Antarctica around October, 2004. Historically, the total column ozone values of less than 220 Dobson Units were not observed prior to 1979. From an aircraft field mission over Antarctica, a total column ozone level of less than 220 Dobson Units is a result of catalyzed ozone loss from chlorine and bromine compounds. For these reasons, scientists use 220 Dobson Units (or less) as the boundary of the region representing ozone loss – the so-called “ozone hole”.
29 7.2 SOUTH CHLOROFLUOROCARBONS AND OZONE The ozone hole is caused by chemicals called chlorofluorocarbons (CFCs). CFCs escape into the atmosphere from refrigeration and propellant devices and processes. Once widely used in domestic appliances and aerosol sprays their usage has been restricted in many countries. However, in the lower atmosphere, they are so stable that they persist for years or even decades. This long lifetime allows some of the CFCs to eventually reach the stratosphere. In the stratosphere, ultraviolet light breaks the bond holding chlorine atoms (Cl) to the CFC molecule. A free chlorine atom goes on to participate in a series of chemical reactions that both destroy ozone and return the unchanged free chlorine atom to the atmosphere where it can destroy more ozone molecules. REFERENCES & FURTHER READING http://ozonewatch.gsfc.nasa.gov/facts/hole.html - What is the ozone hole? http://ozonewatch.gsfc.nasa.gov/ - Ozone Hole Watch
31 7.2 SOUTH LEOPARD SEAL The leopard seal (Hydrurga leptonyx) is named for its black-spotted coat. They are the most formidable hunters of all the seals and the only ones that feed on warm-blooded prey such as other seals. Leopard seals use their powerful jaws and long teeth to kill smaller seals, fish, and squid. These effective predators live in frigid Antarctic and sub-Antarctic waters, where they also eat penguins. They often wait underwater near an ice shelf and snare the birds just as they enter the water after jumping off the ice. They may also come up beneath seabirds resting on the water surface and snatch them in their jaws. Shellfish are far less dramatic prey but still an important part of the leopard seal's diet. Leopard seals are true seals. They have long bodies 3.5m (11.5 ft) in length and elongated heads, and weigh up to 380 kg (840 lbs). Like most other seals, leopard seals are insulated from frigid waters by a thick layer of blubber. Though the leopard seal is known for its coat, it has not been commercially hunted for its skin.
32 7.2 SOUTH EMPEROR PENGUIN Emperor penguins (Aptenodytes forsteri) are the largest of all penguins. An average bird stands some 115 cm (45 in) tall and weighs 40 kg (88 lbs). These flightless animals live on the Antarctic ice and in the frigid surrounding waters. Penguins employ physiological adaptations and cooperative behaviors in order to deal with the incredibly harsh environment. For example, they huddle together to escape wind and conserve warmth. Individuals take turns moving from the cold perimeter to the relatively warm interior of the group.
33 7.2 SOUTH ICE FISH The Antarctic icefish are the largely endemic, dominant fish found in the cold continental shelf waters surrounding Antarctica. They reach about 33 cm (12 in) in length. Most icefish live at seawater temperatures between –2°C and 4°C (28-39°F), but some sub-polar species inhabit waters that may be as warm as 10°C (50°F) around New Zealand and South America. Icefish lack a swim bladder and the majority of species are therefore benthic (pertaining to the bottom of a sea) or demersal (found at or near the bottom of the sea). Icefish have evolved a variety of adaptations that permit survival in the Antarctic Ocean. Many are able to survive in the freezing waters because of the presence of an antifreeze glycoprotein in their blood and body fluids. Another adaptation is that while the majority of animal species have hemoglobin in their blood, some icefish do not. These icefish are able to survive without hemoglobin in part because of the high oxygen content of the cold waters of the Antarctic Ocean and in part because oxygen is absorbed and distributed directly by the plasma.
34 7.2 SOUTH KILLER WHALE (ORCA) Orcas (Orcinus orca) or killer whales are the largest of the dolphins and one of the world's most powerful predators. Killer whales are 9.7 m (32 ft) in length and weigh up to 5,443 kg (12,000 lbs). Orcas are easily recognizable by their distinctive black-and-white colouring. They eat fish, squid, and seabirds. They also hunt marine mammals such as seals, sea lions and whales, employing teeth that can be 10 cm (4 in) long. Though they frequent cold, coastal waters, orcas can be found from polar regions to the Equator. Females give birth every 3-10 years after a 17-month pregnancy. Killer whales form resident or transient pod populations (family groups of up to 40 individuals). These different groups hunt different prey and use different techniques to catch them. Resident pods tend to prefer fish while transient pods target marine mammals. Orcas herd schools of fish into tight circles to kill them. Orcas make a wide variety of sounds and they use echolocation to communicate and hunt.
35 7.2 SOUTH KRILL Krill (Euphausiacea spp.) is a small shrimp-like crustacean that is about 6 cm (2.4 in) in length. Krill feed on phytoplankton (microscopic, single-celled algae and plants) and they, in turn, are the main diet of literally hundreds of different animals including fish, birds and baleen whales. Simply put, without krill, most of the life forms in the Antarctic would disappear. Antarctic krill can live up to 10 years, an amazing longevity for such a heavily hunted creature. They spend their days avoiding predators in the cold depths of the Southern Ocean, some 100 m (330 ft) below the surface. At night, they drift up the water column toward the surface in search of phytoplankton.
36 7.2 SOUTH LIMPET Limpets are marine molluscs with flattened, cone-shaped shells. They live throughout the intertidal zone on the rocky coasts of most oceans. A hard shell protects limpets from drying out and against predators. At high tide, limpets search for seaweed on rocks. After feeding, limpets always return to the same spot. REFERENCES & FURTHER READING http://animals.nationalgeographic.com/animals/mammals/killer-whale.html - Killer Whale http://animals.nationalgeographic.com/animals/birds/emperor-penguin.html - Emperor Penguin http://animals.nationalgeographic.com/animals/mammals/leopard-seal.html - Leopard Seal http://animals.nationalgeographic.com/animals/invertebrates/krill.html - Krill http://en.wikipedia.org/wiki/Icefish - Icefish http://www.odu.edu/sci/cqfe/species%20studied/ocellated-icefish/ocellated-icefish.htm - Icefish
38 7.3 OCEAN LIFE 7.3.1 Pinnipeds There are 5 groups of marine mammals today: Pinnipeds (True Seals, Eared Seals, Walruses) Cetaceans (Whales and Dolphins) Sirenians (Manatees and Dugongs) Sea Otters Polar Bears The pinnipeds consist of the: True seals Eared seals Walruses There are 33 pinniped species as follows: 18 True seals – e.g. Harbour seal, grey seal 14 Eared seals – e.g. Northern fur seal, California sea lion 1 Walrus – e.g. Pacific walrus (Atlantic walrus subspecies)
39 7.3 OCEAN LIFE DISTRIBUTION Found in all seas except in India and Southwest Asia Still tied to land for breeding Some are pelagic (relating to open ocean waters away from the coasts and continental shelf areas). Others are found on loose pack ice, fast ice, rocks, sand, and even upland. POLLUTION EFFECTS Entanglements – fishing line, fishing nets, etc. can cause entanglement and possible injury and death, especially if the animal is unable to break free and is snared by it. Oil spills – toxic chemicals initially accumulate in the blubber. Subsequently, when the animal fasts during breeding, fat reserves are mobilized, releasing poisons into the blood and depressing the immune system.
40 7.3 OCEAN LIFE ADAPTATIONS 1. Temperature regulation – water absorbs heat 25 times faster than air Fat/blubber/hair – to maintain internal mammalian temperature of 36.5-37.5ºC (97.7-99.5ºF) Countercurrent heat exchange – a temperature regulation system consisting of a network of veins and arteries in the extremities that allows an animal to retain or dissipate heat. “Jugging” – a posture sometimes assumed by sea lions and fur seals while resting in the water: one fore flipper and both hind flippers are held above the surface and resemble a jug handle; used to conserve heat. “Bottling” – a posture sometimes assumed by a seal resting in the water; the face and nose are extended above the surface while the rest of the body remains vertically submerged. 2. Blood shunting – during dives, blood and oxygen is mainly sent to essential organs (e.g. brain) 3. Senses for navigation, foraging and communicating Echolocation (occurs in toothed whales; possibly occurs in baleen whales and pinnipeds) Vocalization for mating, auditory cueing (cow/pup) Hearing essential for predator/prey location (skull modified for directional hearing) 4. Tactile senses Walrus have 600-700 whiskers called vibrissae (singular vibrissa) – these are stiff hairs that project from the face and serve as sensory receptors Ringed Seal vibrissae are 10 times more sensitive than land mammals 5. Sight In low light, pupils dilate to allow more light Walruses have small eyes because they are benthic (bottom) feeders where visibility is limited. They use their vibrissae to feel for food such as molluscs on the bottom
41 7.3 OCEAN LIFE MOST ABUNDANT PINNIPEDS Crabeater Seal (Lobodon carcinophagus) – Southern true seal – 11-30 million animals Ringed Seal (Phoca hispida) – Northern true seal – 6-7 million animals RARE/ENDANGERED PINNIPEDS Hawaiian monk seal (Monachus schauinslandi) – ~1000 animals Mediterranean monk seal (Monachus monachus) – <300 animals West Indian monk seal (Monachus tropicalis) – Extinct? Last reported in 1952 TYPICAL PINNIPEDS (a) Phocid (True) Seals Harbour seal (Phoca vitulina) 600,000+; widespread in N. Hemisphere; eats fish & invertebrates Grey seal (Halichoerus grypus) 225,000+; N. Hemisphere (Britain & Ireland); eats fish, invertebrates & seabirds (b) Otariid (Eared) Seals California sea lion (Zalophus californianus) 160,000; California, Mexico & Galapagos; eats fish & cephalopods Northern fur seal (Callorhinus ursinus) 1,300,000; N. Pacific Ocean (Japan to California); eats fish & squid (c) Walruses Walrus (Odobenus rosmarus) – Pacific & Atlantic Ocean; tusks in both sexes; eats bivalves
46 7.3 OCEAN LIFE DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS FamilyPhocidae (True Seals)Otariidae (Eared Seals)Odobenidae (Walrus) Ear PinnaNo externalYes, externalNo external Fore flipperFurred, grooming use Northern: short, broad long claws Southern: elongated, shorter claws Hairless palm Elongated claws short, not useable for grooming Hairless Short and square claws short Hind flipperCannot be turned forward under body Can be turned forward under body and used for movement on land Used for grooming Can be turned forward under body and used for movement on land Used for grooming SwimmingHind flippers alternate side to side, with lateral swinging of lower body Fore flippers not used Fore flippers like oars Hind flippers not used Hind flippers alternate side to side with fore flippers as stabilizers
47 7.3 OCEAN LIFE DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS FamilyPhocidae (True Seals)Otariidae (Eared Seals)Odobenidae (Walrus) Marine, Fresh or Estuarine Mostly marine but also fresh and estuarine Baikal seal, two ringed seals are freshwater Some harbour estuarine Marine but occasionally ascend freshwater rivers Marine only Breeding System VariablePolygyny 1 Size variation by sex VariableSexual dimorphism 2 Lactation periods 4 days – 10 weeks after birth of pup Several months to over 2 years after birth of pup Two or more years after birth of pup Gestation9.5-11.5 months11-11.75 months15 months Delayed implantation 0-6 months0-4.3 months4-5 months Give BirthAnnuallyUsually annually; sometimes biennially Biennially and longer in older females
48 7.3 OCEAN LIFE DIFFERENCES BETWEEN PHOCID, OTARIID & ODOBENID SEALS FamilyPhocidae (True Seals)Otariidae (Eared Seals)Odobenidae (Walrus) FastingFemales & males often fast or feed little during lactation and breeding Females feed during lactation, territorial males fast during breeding Females and males feed during lactation & breeding but reduced during migration Mammae2 teats, except monk and bearded seals with 4 4 teats MilkRich in fatLess fatty Pup growth rate RapidSlow Polygyny (Polygynous) 1 : A breeding system in which one male mates with more than one female. Sexual dimorphism 2 : Males are significantly larger than females. Males may also have distinctive secondary sexual characteristics such as the male hooded seal’s inflatable nasal sac.
49 7.3 OCEAN LIFE DIFFERENCES BETWEEN SEA LIONS & FUR SEALS FamilyOtariidae (Eared Seals) SubfamilyOtariinae (Sea Lions)Arctocephalinae (Fur Seals) Overall SizeLarger than fur sealsSmaller than sea lions Pelage (fur or hair covering a mammal) Short, coarseThick, luxuriant guard hairs keep undercoat dry Muzzle ShapeRounded (California, Galapagos, Japanese have sagittal crest in mature males Pointed REFERENCES & FURTHER READING http://www.imma.org – International Marine Mammal Association Inc. http://www.marinemammal.net – Marine Mammal Net http://www.seaworld.org – Sea World Animal Information Database http://tmmc.org - The Marine Mammal Center Waller, Geoffrey, Burchett, Michael and Dando, Marc, Sea Life, A Complete Guide to the Marine Environment, Smithsonian Institution Press, Washington 1996. ISBN: 1-56098-633-6
50 7.3 OCEAN LIFE 7.3.2 Penguins DESCRIPTION Penguins are thickset birds with an upright stance on land. Unlike most birds, penguins cannot fly but they are fast and agile swimmers and are perfectly at home in the ocean, with some species spending as much as 75% of their lives at sea, only coming ashore to molt and breed. On land, penguins are slower and waddle or hop awkwardly, although some Antarctic penguins can toboggan more quickly over the ice on their bellies using their flippers and feet to propel them along. An adult penguin’s body has a dark dorsal surface and a light ventral surface. This counter-shading helps conceal swimming penguins from predators – a predator looking down in the water column cannot easily distinguish a penguin’s dark dorsal surface from the dark ocean depths while a predator looking up also cannot easily distinguish a penguin’s light ventral surface from the light ocean surface. Penguins began to lose the ability to fly about 65 million years ago. Over the course of 20 million years, their wings became smaller and more flipper-like, their feathers became sleeker and waterproof, and their bones and bodies became denser and heavier. By about 45 million years ago, penguins had become well-adapted to life swimming and diving in the world’s southern oceans.
51 7.3 OCEAN LIFE SPECIES 17 species – all penguins are found in the southern hemisphere SIZE Largest: Emperor penguin– 45 kg (99 lb) wt., 130 cm (51 in) ht. Smallest: Little penguin– 1 kg (2 lbs) wt., 46 cm (18 in) ht. FEATHERS & BLUBBER Penguins rely on feathers and blubber to insulate them from the cold. Penguin feathers are small and densely packed (~70 per sq. inch). The downy base of each feather traps an insulating layer of air against the bird’s skin while the tips of the feathers overlap to form a waterproof outer coat. Oil from a gland at the base of a penguin’s tail also helps waterproof the feathers – a penguin regularly “preens” or spreads this oil over its feathers with its bill. A layer of blubber (stored fat) also insulates penguins from the cold and allows them to go without food for long periods of time while they are molting or incubating their eggs. Typically, the colder the climate, the thicker the blubber and “fatter” the penguin. A penguin’s insulation is so effective that a penguin can actually overheat. To allow excess heat to escape, penguins pant and cool warm circulating blood through less insulated parts of their bodies, such as their wings, faces and feet.
52 7.3 OCEAN LIFE BILL Penguins use their bills to capture prey, such as fish. Like all birds, penguins don’t have teeth but they have soft, flexible bristles on their tongues and in their throats, which helps them keep hold of prey and prevent it from escaping. LIFESPAN In the wild, the lifespan of a penguin ranges from 6 years for the little penguin to 10-11 years for the black-footed penguin to 50 years for the emperor penguin, with an average lifespan of 15-20 years. Protected in captivity, penguins can live much longer. SWIMMING Penguins are excellent swimmers. A penguin’s body is wedge- shaped and moves easily through water. A penguin’s flaps its strong, flipper-like wings to propel itself forward while steering with its wings, feet, and tail. Black-footed penguins can swim up to 24 kph (15 mph) – four times faster than the fastest human swimmer). DIVING Most dives to find prey are less than 50 m (164 ft) but some can be much deeper. Emperor Penguins have been recorded diving to depths of 400 m (1300 ft) and they can stay under water for as long as 30 minutes. Interesting! Unlike other birds, penguin bones are solid and heavier than flying birds. This adaptation allows them to swim and submerge to hunt for prey but it also means that they cannot fly.
53 7.3 OCEAN LIFE DIET A variety of fishes, squids, and krill (various small crustaceans) NESTING BEHAVIOR Penguins gather in colonies (“rookeries”) of hundreds or thousands to nest and molt. A nest is usually just a pile of rocks on bare ground or a mound of grass and twigs, although some penguins, such as the black-footed penguin, nest in real burrows or rock crevices. Males and mated pairs defend nesting territories that typically extend from the center of the nest to the far reach of the owner’s bill. Nest owners deter intruders through a variety of squawks, pecks, and wing slaps. Males call and display to advertise their territory and attract mates. Mated pairs also call and display to one another as they court and build their nest, and when they trade places on the nest. Penguins form strong bonds with their mates and often breed with the same partner for life. Both parents are essential for the chick’s survival – if either parent is missing, the chick is unlikely to survive. Interesting! Penguins do not swim while they molt because their feathers lose their waterproof quality and they would freeze in the cold water. While they molt, they depend on their blubber for warmth and nourishment.
54 7.3 OCEAN LIFE BREEDING & REPRODUCTION Black-footed penguins lay 1-2 eggs at a time. The incubation period begins mid-November to early December and continues for approximately 5 weeks. These penguins use a special fold of skin extending from the stomach to cover the eggs and keep them warm. Emperor penguins incubate eggs by balancing them on top of their feet (so that the egg never actually touches the ice) and covering them with their stomach. Emperor penguins will huddle together for warmth and incubate their eggs for many weeks weathering Antarctic temperatures, winds, and storms. Chicks are born covered in fluffy down. This down is replaced by a woolly juvenile plumage as the chick gets older. It may be a year or more before the juvenile plumage falls out to be replaced by black and white adult feathers. PARENTAL CARE Male and female penguins share parental duties. While one parent tends to the nest and offspring, the other will go off to hunt and feed. When the feeding parent returns, it takes its turn on the nest and regurgitates food for its chicks. As the chicks mature, both parents may need to hunt to meet their growing offspring’s needs. If both parents are away, chicks may gather in groups (“crèches”) for protection or hide in their burrows until their parents return with food.
55 7.3 OCEAN LIFE PREDATORS In the ocean, predators include leopard seals, fur seals, sea lions, sharks and killer whales. On land, predators include foxes, snakes and introduced predators such as feral dogs, cats, and stoats. Antarctic and sub-Antarctic penguin eggs and chicks are also susceptible to predatory birds, such as Antarctic skuas, sheathbills, and giant petrels. Gulls and ibises also eat approximately 40% of the black-footed penguin eggs. Interesting! All penguins are found in the southern hemisphere but only a few of the 17 species of penguin actually live in Antarctica (emperor, gentoo, chinstrap and Adelie). Others live in the sub-Antarctic, New Zealand, Southern Africa and South America. The Galapagos penguin lives near the Equator.
57 7.3 OCEAN LIFE FEATURES Size and colour of the head, eye, bill and body patterns are important in species identification. Their range and whether or not they have a crest is also important in species identification. Stiff-tailed 1 : Long tail compared to shorter-tailed penguins Crested 2 : Flashy yellow or orange crests on the sides of their heads
58 7.3 OCEAN LIFE ANTARCTIC & SUB-ANTARCTIC PENGUINS NameWeightHeightRangeDescription Emperor45 kg 99 lb 130 cm 51 in Circumpolar AntarcticaLargest penguin. Pale yellow neck King15 kg 33 lb 94 cm 37 in Sub-Antarctic, not Antarctica Second largest penguin. Orange neck patches Gentoo6.4 kg 14 lb 89 cm 35 in Circumpolar Antarctica, sub-Antarctic & Antarctic peninsula Stiff-tailed 1. Distinctive white band over eyes & crown. Bill, legs and feet orange-red Chinstrap6.4 kg 14 lb 76 cm 30 in Almost circumpolar Antarctica & sub- Antarctic Stiff-tailed 1. Narrow black chinstrap on white face. Eye red; bill black Adelie4.1 kg 9 lb 71 cm 28 in Circumpolar Antarctica & sub-Antarctic Stiff-tailed 1. Black head and throat with conspicuous pale eye. Bill dark red Macaroni5.9 kg 13 lb 74 cm 29 in Sub-Antarctic islands & Antarctic peninsula Crested 2. Orange and yellow crest joined across forehead. Eye red, bill red. Waddles Rockhopper3.6 kg 8 lb 58 cm 23 in Sub-Antarctic, not Antarctica Crested 2. Smallest crested penguin. Similar to Macaroni but hops rather than waddles. Yellow crest does not meet on forehead.
59 7.3 OCEAN LIFE NEW ZEALAND PENGUINS NameWeightHeightRangeDescription Fiordland2.3 kg 5 lb56 cm22”NZ, TasmaniaCrested 2. Broad yellow crest reaches base of bill. Diagnostic white stripes across cheeks. Breeds in temperate rainforests. Royal6.8 kg 15 lb76 cm30”Macquarie Island, NZ Crested 2. Largest crested penguin. Similar to Macaroni but has a whitish throat and face. Snares1.8 kg 4 lb61 cm24”Snares Island, south of NZ Crested 2. Like Fiordland but has prominent pink gape. Black cheeks and partly raised crest. Erect- crested 5.4 kg 12 lb69 cm27”South of NZCrested 2. Like Snares but with upswept brush-like crest. Yellow- eyed 7.7 kg 17 lb79 cm31”South Island, NZPale eye and distinctive yellow band through eye and across nape. Breeds in temperate forests. Little1 kg2 lb46 cm18”South Australia and NZ Smallest penguin. Distinctive grey and white plumage. Also known as the Little blue Penguin or Fairy Penguin.
60 7.3 OCEAN LIFE SPHENISCUS PENGUINS NameWeightHeightRangeDescription Humboldt5 kg11 lb66 cm26”Peru & ChileSingle breast band. Large bill with pink base Magellanic4.1 kg9 lb71 cm28”Falklands, Argentina & Chile Two breast bands. Smaller bill than Humboldt Black-footed5 kg11 lb71 cm28”Southern AfricaBlack breast-band (sometimes two). Eye black, bill black. Also known as the African penguin or Jackass penguin. Galapagos2.3 kg5 lb53 cm21”Galapagos IslandsTwo indistinct breast bands and narrow white line from eye to throat.
63 7.3 OCEAN LIFE THREATS Oil spills Pollution Rubbish – penguins can ingest plastic and become tangled which causes injury and death Over-fishing has contributed to penguin population declines Introduced predators (e.g. dogs, pigs, ferrets) which prey on eggs, chicks, and even adults Although egg collecting was banned in 1969, illegal egg harvesting continues today CONSERVATION Currently, all penguin species are legally protected from hunting and egg collecting. The threat to each penguin species varies – some species are not in any immediate danger while others are at great risk. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) lists the Humboldt penguin as “endangered” or in danger of extinction, while the black-footed penguin is listed as “threatened”, or likely to become endangered. The World Conservation Union (IUCN) lists the erect-crested, yellow-eyed and Galapagos penguins as “endangered”, the gentoo and Magellanic penguins as “threatened”, and the rockhopper, royal, Snares, Macaroni, Fiordland, black-footed, and Humboldt penguins as “vulnerable”,. Under the U.S. Endangered Species Act of 1973 (ESA), the Galapagos penguin is listed as “endangered" (i.e. the species faces a very high risk of extinction).
64 7.3 OCEAN LIFE REFERENCES & FURTHER READING http://www.antarcticconnection.com/antarctic/wildlife/penguins/index.shtml - Antarctic Connection http://www.seaworld.org/animal-info/info-books/penguin/index.htm - Penguins Peterson, Roger Tory, Penguins, Houghton Mifflin Company, Boston, MA 1979. ISBN 0-395-27092-8 Waller, Geoffrey, Burchett, Michael and Dando, Marc, Sea Life, A Complete Guide to the Marine Environment, Smithsonian Institution Press, Washington 1996. ISBN: 1-56098-633-6
66 7.4 ACTIVITIES 7.4.1 Adaptations to the Cold CORE ACTIVITY (a) Match the animals to their adaptations to the cold by drawing a line between the animal and the adaptation. (Note that some animals may have more than one adaptation).
67 7.4 ACTIVITIES ANSWERS (a) Match the animals to their adaptations to the cold by drawing a line between the animal and the adaptation. (Note that some animals may have more than one adaptation).
68 7.4 ACTIVITIES 7.4.2 Pinnipeds CORE ACTIVITY (a) Add the following labels to the picture: TRUE (PHOCID) SEAL Eye No external ear pinna Fore flipper Hind flippers for main propulsion. Cannot be turned forward under body on land. EARED (OTARIID) SEAL Eye External ear pinna Fore flipper Hind flippers can be turned forward under body and can also be used for swimming and/or walking (b) What are some endangered seals? What seals are abundant?
70 7.4 ACTIVITIES ANSWERS (a) Add the following labels to the picture: TRUE (PHOCID) SEAL Eye No external ear pinna Fore flipper Hind flippers for main propulsion. Cannot be turned forward under body on land. EARED (OTARIID) SEAL Eye External ear pinna Fore flipper Hind flippers can be turned forward under body and can also be used for swimming and/or walking (b) What are some endangered seals? What seals are abundant? Hawaiian monk seal and Mediterranean monk seal are endangered Crabeater and Ringed seals are quite abundant
72 7.4 ACTIVITIES 7.4.3 Penguins CORE ACTIVITY (a) Add the following labels to the picture of the penguin: Eye Pointed Bill Light Ventral Surface Dark Dorsal Surface Foot Tail Flipper-like wing Pale yellow neck patch (b) Can polar bears prey on penguins? If not, why not? (c) What preys on penguins?
73 7.4 ACTIVITIES ANSWERS (a) Add the following labels to the picture of the penguin: Eye Pointed Bill Light Ventral Surface Dark Dorsal Surface Foot Tail Flipper-like wing Pale yellow neck patch
74 7.4 ACTIVITIES (b) Can polar bears prey on penguins? If not, why not? No. Polar bears live in the Arctic while all penguins live south of the Equator. Thus, polar bears and penguins never meet in the wild. (c) What preys on penguins? In the ocean, predators include leopard seals, fur seals, sea lions, sharks and killer whales. On land, predators include foxes, snakes and introduced predators such as feral dogs, cats, and stoats. Antarctic and sub-Antarctic penguin eggs and chicks are also susceptible to predatory birds, such as Antarctic skuas, sheathbills, and giant petrels. Gulls and ibises also eat approximately 40% of the black-footed penguin eggs.
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