Ocean Education
Teacher's Notes
These notes will give you some basic background on ecological
principals and conservation issues relating to oceans.
Biodiversity
Biodiversity means "biological diversity," or the variety
of living things. Biodiversity is usually described at three
levels: genetic, species, and ecosystem. Genetic diversity
occurs within each species or population. A genetically diverse
species or population will have members that exhibit a broad
range of characteristics. Broad genetic diversity is what
allows a species to adapt to changing conditions over time.
Species diversity refers to the variety of species that occur
in a particular area. It allows for more complex food webs
and, therefore, more resilient ecosystems, since creatures
may have several alternate food sources. Ecosystem diversity
refers to the variety of ecosystems on Earth. The greater
the variety of living spaces, the greater the variety of life
forms that can inhabit them.
Ecosystems
Ecosystems include the living and non-living components of
an area, along with interactions among them. The living parts
of an ecosystem consist of micro-organisms, plants, and animals
(including humans). Non-living elements include minerals,
soil, water, and so on. Vital processes, such as the carbon
cycle, water cycle, and energy cycle, also occur within healthy
ecosystems. Ecosystems can be any size, from microscopic to
enormous. Larger ecosystems contain smaller ones. For example,
we might consider the world's oceans to be one giant, interconnected
ecosystem, and the Pacific, Atlantic, and Arctic oceans to
be smaller ecosystems within it. We might also consider each
reef, estuary, salt-marsh, and beach to be a separate ecosystem.
Habitat
Habitat is where an animal or plant lives. All organisms,
including humans, need the right habitat to survive. The four
main components of habitat are food, water, shelter, and space.
Habitat components for an ocean organism might be quite specific
and far apart. For instance, the whooping crane requires nesting
grounds on Canada's northern tundra in summer and coastal
marshes along the Gulf of Mexico in winter. It also needs
feeding and resting places to make the long journey between
breeding and wintering grounds. That's why prairie wetlands
are important habitats for this species and why human prairie
communities that protect wetlands are part of a healthy ocean
community. Sea turtles spend most of their lives in the open
ocean, but without protected beaches where they can lay their
eggs, they cannot survive. Many marine animals, including
fish, depend on coastal habitats to meet all or part of their
needs. Yet these parts of the ocean are the ones most affected
by pollution and human development.
Natural communities
Natural communities are collections of living things that
share the same space. The plants, animals, and micro-organisms
that inhabit natural communities tend to depend on one another
either directly or indirectly. For instance, polar bears depend
directly on seals that make up the main part of their diet
and indirectly on the fish that feed the seals. Polar bears,
seals, and fish form part of an Arctic ocean community.
Watersheds and drainage basins
All land is drained by systems called watersheds, which include
creeks, lakes, wetlands, and rivers that eventually empty
into the ocean. Smaller, local watersheds flow together and
can be considered as larger units on a regional level. Canada's
watersheds are organized into five main drainage basins, the
boundaries of which are determined by the ocean bodies they
flow into: the Pacific, Atlantic, Arctic, Hudson Bay, and
Gulf of Mexico.
Estuaries
Estuaries are areas where freshwater from rivers meets salt
water from oceans. The mixing of these waters and daily rhythms
of rising and falling tides create unique conditions that
encourage rapid plant growth. Estuaries are critical habitats
for a rich diversity of species. Canada's extensive coasts
are lined with thousands of rivers of all sizes, from the
tiniest coastal creek to the giant St. Lawrence River. Estuaries,
great and small, add up to a major ecological asset for Canada.
Unfortunately, our coastal areas, especially estuaries, are
being increasingly disturbed by human development.
Bioaccumulation in food chains
Some toxic chemicals "bioaccumulate" in wildlife. Scientists
discovered this phenomenon when they noticed that the levels
of certain chemicals in some animals' bodies were significantly
higher than those in the surrounding environment. These levels
were highest at the top of food chains. The more links in
a food chain, the higher the levels of toxic chemicals. Many
types of chemicals are stored in fat tissues and eliminated
by animals far more slowly than they are consumed. Over its
lifetime, an animal will gather and store toxic chemicals
at levels far above those in its environment. This bioaccumulation
happens at each successive level of a food chain. Predators,
such as polar bears, eagles, and people, are at the top of
long food chains and sometimes accumulate concentrations of
toxic chemicals in their bodies hundreds of times greater
than those in the surrounding environment. Bioaccumulation
can lead to serious health risks, including cancer.
Marine pollution
Eighty per cent of marine pollution originates from human
activities on land, coming mainly from individuals and communities,
not industries. Pollutants make their way to the ocean through
sewers, waterways, and atmospheric currents.
Untreated or partially treated sewage from domestic waste-water
often ends up in waterways. Its main threat to humans is the
bacterial and viral contamination of shellfish, which can
turn seafood into a lethal meal and lead to the closure of
economically important fisheries.
Persistent organic pollutants (POPs) are a class of chemicals
that accumulate in food chains and cause tumours, deformities,
loss of reproductive ability, and even death in plants and
animals, including humans. Some examples are DDT, PCBs, and
dioxins. POPs enter the environment through pesticides sprayed
on lawns and crops and industrial chemicals that leak from
landfills. They are transported long distances by waterways,
ocean currents, and the atmosphere. POPs affect ocean wildlife,
such as beluga whales, fish, seals, and even arctic species
like polar bears.
Heavy metals, such as mercury and cadmium, cause problems
similar to those caused by POPs. They enter the environment
through mining and smelting operations, the burning of coal
for electrical generation, and pulp and paper industrial processes.
Oil is toxic to aquatic life if ingested or absorbed through
the skin. It also fouls the fur and feathers of wildlife and
smothers aquatic habitats and beaches. Oil finds its way into
the ocean through marine oil spills and land-based sources
like domestic storm sewers. Urban communities introduce an
estimated 30 million litres of oil into aquatic ecosystems
each year, as people carelessly pour waste oil down the drain.
Marine debris, particularly plastic litter, chokes and entangles
wildlife, such as sea turtles, whales, dolphins, and seals.
Litter gets into the marine environment through direct dumping
from ships and by entering waterways from poorly managed waste-disposal
sites.
Habitat Destruction
Coastal habitat destruction is a growing concern. As human
communities expand, critical habitats, like salt-marshes,
beaches, and estuaries, are altered to accommodate houses,
harbours, and recreational facilities. The loss of habitats
vital to marine migrators is another major threat. Many ocean
travellers, including endangered waterfowl and shorebirds,
use inland wetlands as stopovers during their migrations.
Salmon travel up coastal rivers to reach spawning habitats.
The importance of such habitats is often overlooked because
wildlife does not visit them for long. Consequently, we often
drain marshes for agriculture, obstruct rivers with dams,
and develop shorelines for condominiums and marinas.
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