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Student Worksheet: Arctic Sea Ice and the Food Web
Arctic sea ice.
Kathy Conlan © Canadian Museum of Nature
Introduction
The Arctic is an exotic ecosystem, as fascinating and varied as any place on Earth. In some regions the land is
drier than the Sahara, while the ocean's life forms can be as colourful as those in a tropical reef.
The influence of ice and its freezing and thawing is everywhere and affects everything. It is a region of extreme
temperatures, nutrients and colours. In the height of summer there is sun 24 hours a day, and in the middle of
winter, no sun at all. Towns and roads dot the map in some places, and open wilderness stretches for hundreds
and thousands of kilometres.
The summer is boom time—the oceans teem with life, and whales and birds travel from all over the globe to
reap the Arctic's riches while the air temperatures are as low as 0 °C. However, the winter is a solemn test of
survival, one without sunlight and with temperatures as low as minus 50 °C. In the ocean, the temperature is
much less variable; it changes by only a few degrees, and species don't need to go into an over-wintering
survival stage or emigrate in order to survive.
The plants and animals that make the Arctic home—and there are many—are all highly adapted to the extreme
environment and they are often unique. In the oceans, many species live only in the Arctic, but others have
broad ranges throughout the deeper waters of the Atlantic and Pacific. True, there are not nearly as many
different species here as there are in a tropical rainforest, but there are more kinds of plants and animals here
than you might think—in fact, thousands of them. The species that have adapted to survive in the Arctic have
relatively little competition, and can often be found in abundance.
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Resolute Bay, Nunavut.
André Martel © Canadian Museum of Nature
People living in the Arctic are, in some areas, hearing thunder for the very first time in their lives, and
encountering new "southern animals" such as robins, for which they have no names in their language. This is
because the Arctic climate is warming. In fact, the Arctic is changing faster than any other place on Earth.
The circumpolar region is experiencing its warmest air temperatures in four centuries, and temperatures are
increasing at approximately double the global rate. A recent report notes that there has been a 7% reduction in
ice cover in just 25 years, and a 40% loss of ice thickness. Scientists predict that the Arctic summer will be
mostly ice-free within 30 years if trends continue.
With increased warming, many of the organisms that have adapted so well to the Arctic will be under threat.
No-one knows exactly what will happen, but for animals such as polar bears and seals, their habitat—the sea
ice—is in grave danger. With the ice gone, the algal community that lives on the undersurface will also
disappear, affecting everything else in the food web that depends on it. Scientists don't fully understand the
diversity of life of the Arctic Ocean; and it is quite possible that because of climate change, they never will.
Activity 1: Seasonal Arctic Ice Coverage
Review the following resources and then answer the questions below:
• Animation: Normal Ice Season in Canadian Waters
http://www.ice-glaces.ec.gc.ca/app/WsvPageDsp.cfm?Lang=eng&ID=11860
• Map: Minimum and Maximum Sea Ice in Canadian Waters.
http://atlas.nrcan.gc.ca/site/english/maps/environment/seaice/cis_min_max_map.jpg/image_view
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1.1 Where is sea ice found in Canada?
1.2 During which months do the maximum and minimum sea-ice extents occur?
1.3 What seasons do these times represent?
1.4 Is there an east–west, ice-free route (passage) through the Canadian Arctic Ocean at any time of the year?
Activity 2: A Unique Ecosystem
Algae in sea-ice drainage channels.
Alex Tirabasso © Canadian Museum of Nature
Review the following animation, which shows how a unique ecosystem forms underneath Arctic sea ice, and
then answer the questions below. Consult the glossary if necessary for an explanation of the terms used.
• Animation: Sea-Ice Ecosystem
http://nature.ca/education/cls/lp/lpasi3danim_e.cfm
• Glossary: Arctic Sea Ice and the Food Web
http://nature.ca/education/pro/gl/gecosgl_e.cfm
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2.1 How do drainage channels form in sea ice?
2.2 What enters the tiny holes created by sea water draining out of the ice?
2.3 What feeds on these organisms?
Activity 3: A Phycologist at Work
Crew of the CCGS Amundsen deploying
a rosette.
© Martin Fortier/ArcticNet
Watch the following video where Canadian Museum of Nature scientist Michel Poulin talks about his research
on diatoms in the Canadian Arctic, and then answer the questions below:
• Video: Arctic Marine Research (3 min. 4 sec.)
http://nature.ca/education/cls/video/varct_e.cfm
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3.1 What is a phycologist?
3.2 What are diatoms?
3.3 What is the name of the instrument lowered into the water from a ship to collect phytoplankton samples?
Activity 4: Arctic Food Web
View the PowerPoint on Arctic marine life and then read the background information for the Arctic Food Web
provided below. Look at the photos in the photo gallery.
• PowerPoint: Arctic Sea Ice and the Food Web
http://nature.ca/education/_doc/lpasi_e.ppt
• Photo Gallery
http://nature.ca/education/cls/lp/lpasi_ph_e.cfm
4.1 Using the information provided and other material that you can find, draw a diagram of an Arctic Ocean
food web. You should include:
• at least four trophic levels
• ten groups of organisms
• labels for all organisms
• some indication of relative abundance of organisms
• representation of the relationships between organisms.
Background Information
Sea ice plays an important role in the food web of the Arctic marine ecosystem. The following are some
examples of animals that are part of this ecosystem.
Diatoms
The basis of the food web in oceans depends primarily on microscopic plants called phytoplankton. They
usually live in the water, but in the Arctic they are also found in and on the sea ice. One group of phytoplankton
includes diatoms. Diatoms are found in almost every aquatic environment. There are so many different types of
diatoms that they have not yet been counted; a best guess is more than 100 000 species. Diatoms are
microscopic, but they sometimes stick to each other, thus forming clusters or colonies that grow so big that they
can be seen floating on top of the water.
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Through photosynthesis, these microscopic plants consume carbon dioxide while releasing oxygen and
producing carbohydrates. Elements in the water such as nitrogen, phosphorus and sulphur attach to these
carbohydrates and convert them into organic compounds that provide food for tiny plant-eating creatures called
zooplankton, as well as other marine invertebrates.
Diatoms on the underside of a sea-ice core.
Michel Poulin © Canadian Museum of Nature
Isopods
Isopods are a very diverse group of animals. They include sowbugs, which can often be seen in basements or
gardens. The isopods that live in the Arctic Ocean are mostly carnivorous and feed on dead whales, fish and
squids; they may also be active predators of slow-moving prey such as sea cucumbers, sponges and other
animals that live on the ocean floor.
Amphipods
Amphipods are small, shrimp-like animals. The majority of amphipods in the Arctic live in holes in the sea ice
and on the underside of pack ice. Amphipods are eaten by fish such as Capelin and Arctic Cod, which are very
important in the diet of other fish, marine mammals and seabirds. Some seabirds, such as the Arctic Tern, also
feed on amphipods, as do young seals.
Cockles
The cockle is a bivalve, which is a group of animals that have two halves to their shell, joined together by a
ligament. Other examples of bivalves include clams, scallops, mussels and oysters. Arctic cockles are preyed
upon by fish, walruses, bearded seals and several duck species. About 140 Arctic bivalve species are currently
known.
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Nudibranchs
Nudibranchs are commonly referred to as sea slugs. They are carnivores that live on the sea floor. Depending on
the group, they feed on sea anemones, sponges, bryozoans and other animals.
Sea Cucumbers
Sea cucumbers are animals that generally use their special tube feet to trap food particles, such as dead and
decaying matter, from the sea-floor sediment. Many also use their branchial tree to trap particles suspended in
the water. They are related to sea stars and sea urchins, which have the same radial symmetry in which their
bodies are divided into five segments: their body has five lines running down it, sea stars usually have five
arms, and urchins have five rows of tube feet.
Sea Anemones
Sea anemones are animals that are sometimes mistaken for plants. They usually remain attached to hard
surfaces such as shells or rocks, but some of them burrow into the sea floor. Anemones are most diverse in the
tropics, but are found in the Arctic Ocean as well, in particular on the continental-shelf sea floor.
Sea Urchins
Eleven sea urchin species are known to live in the Arctic Ocean. They usually live on hard surfaces, and feed by
scraping off algae and encrusting animals with their five teeth. The teeth are located in a complex organ called
an Aristotle's lantern that is on the underside of their shell.
Sea Stars
Most sea stars are carnivores whose favourite food is bivalves. They have a unique feeding method: they use
their tube feet to pry open the two halves of a bivalve and then they insert their stomach inside it! Their stomach
then releases enzymes that slowly digest the animal within its own shell.
Arctic Cod
Arctic Cod (Boreogadus saida) are fish that eat mainly shrimp, amphipods and copepods. They are eaten by a
variety of other large fish, as well as many seabirds and most Arctic marine mammals. They spend much of
their time associated with sea ice and remain in Arctic waters throughout their life cycle. This fish is a key
component of the Arctic food web because it is the link in the food chain between small amphipods and higher
vertebrates such as seabirds and marine mammals.
Walrus
Walruses (Boreogadus saida) overwinter in areas of pack ice where the ice is thin enough (less than 20 cm
thick) to allow them to break through and maintain breathing holes, but thick enough to support the weight of
groups of these large animals. Walruses prefer to eat bivalves such as clams, mussels and cockles, which they
suck from the shells. They also consume many other kinds of invertebrates, including nudibranchs, sea
cucumbers and other soft-bodied animals.
Ringed Seal
Ringed seals (Pusa hispida) are the most abundant seal species in the Arctic. They use the ice for breeding,
moulting and resting, and rarely, if ever, move onto land. They maintain their cone-shaped breathing holes by
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clawing the forming ice with their front claws. These seals can be found under ice up to 7 m thick. Before
surfacing, a seal may blow bubbles into the hole to test for predators. As snow drifts over the hole, a space is
hollowed out to provide some protection from cold and predators, and to give birth to pups. Ringed seals have a
varied diet composed primarily of shrimp-like crustaceans and small fish such as Arctic Cod.
Beluga
Belugas (Delphinapterus leucas) are commonly found in ice-covered waters where they use open water at iceedges, leads and polynyas to surface for breathing. These whales feed on crustaceans and small fish such as
Arctic Cod. Like those of narwhals and bowheads, Arctic beluga populations stay in the Arctic year-round.
Polar Bear
The polar bear (Ursus maritimus) is dependent on sea ice for most of its needs, and as a result, is often regarded
as a marine mammal. Factors that influence the distribution, movement, duration and structure of sea ice have a
major impact on the population ecology of polar bears, whose diet consists mainly of ringed and bearded seals.
They will catch and consume, on average, about one seal every six and a half days. Polar bears also
occasionally feed on whales and young walruses.
http://nature.ca/education/cls/lp/lpasi_e.cfm