EDEP Program Fall 2013| Week 3-4: Ocean Currents and Pollution
Lesson Topic
How do marine biologists know how currents in the ocean
work?
Why is pollution so important to understand?
What are scientists doing about pollution?
Lesson Objective
After this week, students will be able to:
- Model how ocean currents work
- Describe the causes and the effects of Pollution.
- Outline various methods for combating pollution.
Words to know: circulations, topographic, pollution, sediment,
pesticides, pathogens, ecosystems, alien species, conservation
Background Information
Ocean currents are the mass movements and circulations of water caused by various factors. They flow
throughout the world connecting the oceans’ water and resources. The patterns of these movements are
determined by wind, major topographic landmarks - like the world’s largest salt flat in Bolivia, many hot
springs from around the world, volcanoes found throughout the oceans, deserts, salinity, heat distribution,
and the rotation of the earth. Both surface and deep water currents are present in the movement of ocean
water and are the exchange system that distributes heat, salinity, nutrients, the inhabitants of the oceans, and
all other resources.
Ocean currents have two different methods of moving water. Surface currents move as a result of blowing
winds and are influenced by atmospheric factors. Deep ocean currents move as a result of the density
differences that are present in the ocean. Density is determined by both salinity and temperature; in areas
such as the Poles, the water is very cold and has glaciers forming so the freshwater is taken out of the water
and the remaining water becomes more saline, resulting in very dense water. This water that is formed in the
poles then moves throughout the world to mix the oceans. Water from the equator is less dense because it’s
warmer, so it moves towards the poles. The water is then used in thermohaline circulation, commonly
referred to as the oceans conveyor belt. The ocean conveyor begins in the Norwegian Sea, where warm water
from the Gulf Stream heats the atmosphere in the cold northern latitudes. This loss of heat to the atmosphere
makes the water cooler and denser, causing it to sink to the bottom of the ocean. As more warm water is
transported north, the cooler water sinks and moves south to make room for the incoming warm water. This
cold bottom water flows south of the equator all the way down to Antarctica. Eventually, the cold bottom
waters are able to warm and rise to the surface, continuing the conveyor belt that encircles the globe.
The two largest currents on earth are the Kuroshio Current which circulates near Japan, and the Antarctic
Circumpolar Current which circulates around Antarctica. Other currents are: the North and South Equatorial
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Currents, the Gulf Stream, and the East Australian Current (many seen below).
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Conservation Concerns/Pollution in the Ocean
The pollution of water bodies affects marine life and humans alike. Today, marine life is seriously impacted by
many different sources of pollution— oil spills, garbage dumping, accumulation of toxic materials and
industrial wastes in the ocean. Since oceans are the biggest natural sources of water, taking care of them and
the marine life thriving in the water bodies is the responsibility of every human being and necessary to
ensuring survival of the planet.
Plastic bags, balloons, medical waste, soda cans, and milk cartons all find their way into the oceans of the
world. These items float in the water and wash up on beaches. They often create health hazards for marine
life. Ocean mammals can get entangled in old nets and drown because they cannot get to the surface for air.
Birds, turtles, and fish ingest a variety of plastic items and their digestive systems become clogged. Sea turtles
are especially attracted to floating plastic bags which appear to be jellyfish, one of their favorite treats. The
plastic bags block the digestive system and cause a slow and painful death. Various pieces of trash can cause
entanglement, starvation, drowning, and strangulation. Scientists estimate that there is one hundred million
metric tons of plastic debris in the ocean.
Excess nutrients result in poor water quality, leading to decreased oxygen and increased nutrients in the water
(eutrophication). This can lead to enhanced algae growth on reefs, crowding out corals and significantly
degrading the ecosystem. In addition, sediment deposited onto reefs smothers corals and interferes with their
ability to feed and reproduce. Finally, pesticides interfere with coral reproduction and growth. Sewage
discharge and runoff may also introduce pathogens into coral reef ecosystems.
When the trash washes up onto beaches and into marshes and wetlands, it ruins breeding grounds and
habitats. Oxygen is necessary for all life. As trash degrades in the water, it uses up oxygen. When oxygen levels
are low marine life can't thrive.
See the chart of the following page for more information on types of pollution that are impacting the oceans.
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Type of Pollution
Primary Source/Cause
Effect
Nutrients
Runoff: approximately 50% sewage, 50% from
forestry, farming, and other land use. Also
airborne nitrogen oxides from power plants, cars
etc.
Feed algae blooms in coastal waters. Decomposing algae
depletes water of oxygen, killing other marine life. Can
spur algal blooms (red tides), releasing toxins that can kill
fish and poison people.
Sediments
Erosion from mining, forestry, farming, and other
land-use; coastal dredging and mining
Cloud water; impede photosynthesis below surface
waters. Clog gills of fish. Smother and bury coastal
ecosystems. Carry toxins and excess nutrients.
Pathogens
Sewage, livestock.
Contaminate coastal swimming areas and seafood,
spreading cholera, typhoid and other diseases.
Alien Species
Several thousand per day transported in ballast
water; also spread through canals linking bodies of
water and fishery enhancement projects.
Outcompete native species and reduce biological
diversity. Introduce new marine diseases. Associated with
increased incidence of red tides and other algal blooms.
Problem in major ports.
Persistent Toxins
(PCBs, Heavy
metals, DDT etc.)
Industrial discharge; wastewater discharge from
cities; pesticides from farms, forests, home use
etc.; seepage from landfills.
Poison or cause disease in coastal marine life, especially
near major cities or industry. Contaminate seafood. Fatsoluble toxins that bio-accumulate in predators can cause
disease and reproductive failure.
Oil
46% from cars, heavy machinery, industry, other
land-based sources; 32% from oil tanker
operations and other shipping; 13% from
accidents at sea; also offshore oil drilling and
natural seepage.
Low level contamination can kill larvae and cause disease
in marine life. Oil slicks kill marine life, especially in
coastal habitats. Tar balls from coagulated oil litter
beaches and coastal habitat. Oil pollution is down 60%
from 1981.
Plastics
Fishing nets; cargo and cruise ships; beach litter;
wastes from plastics industry and landfills.
Discard fishing gear continues to catch fish. Other plastic
debris entangles marine life or is mistaken for food.
Plastics litter beaches and coasts and may persist for 200
to 400 years.
Radioactive
substances
Discarded nuclear submarine and military waste;
atmospheric fallout; also industrial wastes.
Hot spots of radio activity. Can enter food chain and cause
disease in marine life. Concentrate in top predators and
shellfish, which are eaten by people.
Thermal
Cooling water from power plants and industrial
sites
Kill off corals and other temperature sensitive sedentary
species. Displace other marine life.
Noise
Supertankers, other large vessels and machinery
Can be heard thousands of kilometers away under water.
May stress and disrupt marine life.
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Looking for Solutions
What can we do to help? The cornerstone of fighting pollution is going green; this is actively reducing, reusing
and recycling whenever possible. Conservation is the wise use of natural resources (nutrients, minerals, water,
plants, animals, etc.) and cultural resources (different groups of people from different parts of the world). It
may also include protecting the large collections of resources that make up a habitat or environment.
Conservation is important to make certain changes don’t happen too quickly. Rapid change can force animals,
plants, places, or people to become endangered or extinct.
Activities
Exploring Ocean Currents
Materials
 Milk (whole or 2%)
 Dinner plate
 Food coloring (red, yellow, green, blue)
 Dish-washing soap
 Cotton swabs
Procedure
Pour enough milk in the dinner plate to completely
cover the bottom and allow it to settle. Add one
drop of each of the four colors of food coloring red, yellow, blue, and green - to the milk. Keep the drops
close together in the center of the plate of milk, but not close
enough that they begin to mix. Find a clean cotton swab for
the next part of the experiment. Have the students predict
what will happen when you touch the tip of the cotton swab
to the center of the milk. It's important not to stir the mix just
touch it with the tip of the cotton swab. Place a drop of liquid
dish soap on the tip of the cotton swab. Place the soapy end
of the cotton swab back in the middle of the milk and hold it
there for 10 to 15 seconds. Add another drop of soap to the
tip to the cotton swab and try it again. Experiment with
placing the cotton swab at different places in the milk. Be
sure that the students notice that the colors in the milk
continue to move even when the cotton swab is removed.
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The long-term effects of pollution on water
Materials
 Measuring cup
 Tap water
 1-gallon (4-liter) glass jar
 Food coloring
 Spoon
Procedure
Students (individually, in groups, or as a class) will start with ½ cup of water in the 1-gallon jar. The activity
leader will then add 2 drops of food coloring to the mixture. The activity leader will explain that this
represents pollution being dispersed into the water. Students are then to add 1 cup of water a time until the
color disappears. Students should find that it takes about 7 cups of water to make the color disappear.
Initially, the red is visible because the molecules of red are close together (pollution starts concentrated at
once source). As clean water is added, the color molecules spread evenly throughout the water (as with
pollution). Eventually, the pollution molecules become far enough apart to become invisible to the naked eye.
As pollution flows downstream from where it is initially dumped, it becomes mixed with more water. This
does not mean that it is gone. When you drink water from the jar, you ingest a small amount of red food
coloring; likewise, drinking water from the polluted water means you’re drinking a small amount of pollution.
It is because of this that it is quite easy for animal life in streams miles away from the source of pollution can
be affected by the pollution.
Coral Reef:
This week the coral reef activity is going to be placing sea life photographs and images (shown below), or
drawn on their own. Coral reefs are not stagnate structures in the ocean. They are full of life and many
different animals use them as shelter, for hunting, and for social interaction.
Students can add it on by taping items to craft sticks/pipe cleaners and taping it onto the reef, or they could
tape it to the base. However they do it, it should be how they feel most creative and inspired!
The below images are merely examples and suggestions, feel free to come up with your own—even add your
own drawings!
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Glossary
Circulations: Water current flows in a closed circular pattern within an ocean
Topographic: The description of surface shapes and features of the Earth and other observable astronomical
objects including planets, moons, and asteroids.
Pollution: The introduction of contaminants into the natural environment that cause adverse change.
Sediment: Naturally occurring material that is broken down by processes of weathering and erosion.
Pesticides: Substances meant for preventing, destroying or mitigating any pest.
Pathogens: A biological agent that causes disease or illness to its host.
Ecosystems: A community of living organisms in conjunction with the nonliving components of their
environment.
Alien species: Animals and plants that are introduced accidently or deliberately into a natural environment
where they are not normally found.
Conservation: Protecting animals, fungi, plants and their habitats.
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