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Landfall-Learning > Environment > Oceans


The oceans contain mountains taller than Everest, canyons deeper than the Grand Canyon, and the largest animals on earth. The oceans are home to 97% of all of the life on earth. The most important difference between the earth and the other planets in our solar system is the existence of water in liquid form. It is the source of all life as we know it. In fact, our bodies are made up mostly of water and the tears from our eyes are the same consistency as seawater. When you consider the fact that life in the oceans can be found from the surface all the way down to the very bottom of the deepest ocean trench, it is not surprising to realize that the oceans represent over 99% of the living space on Earth....we are indeed living on what is truly an Ocean Planet.

One recent study of a deep-sea community revealed 898 species in an area about half the size of a tennis court. More than half of these species were new to science! And, consider the fact that there exists a creature in the oceans that we know to be the world's largest invertebrate, that can grow to at least 60 feet in length, has eyes as large as volleyballs, but which has never been seen alive in its natural habitat.

The oceans, driven by the sun's heat, control our weather and maintain the temperature of our world. The oceans are as important to our survival as the air that we breathe. On the other hand, as powerful as the oceans are, they are equally as fragile. Threats to the health of our oceans equate to threats to our entire planet, and to us.

What color is the ocean?

Why are phytoplankton so important?

What is carbon dioxide and what does it have to do with the oceans?

What are the primary threats to the oceans as we know them today?

When you're finished reading, try the exercises.

To learn about the creatures who live in the ocean, check out the Sealife page.
To learn about rivers, check out the Rivers page.

What Color is the Ocean?

Did you know that the ocean isn't just blue?

If someone were to ask you what the color of the ocean was, chances are that you would answer that is was blue...and for most of the world's oceans, your answer would be correct.'s a little more complicated than that.

We see color when light is reflected by the things around us. White light is made up of a spectrum, or combination of colors, as in a rainbow, of many different wavelengths. The longer wavelengths of light are red and the shorter wavelengths are blue. The order of the colors in the rainbow - Red, Orange, Yellow, Green, Blue and Violet (ROYGBV) - reflect the order of their wavelengths, from longest to shortest.

When light hits the surface of an object, these different colors can be reflected or absorbed, in differing amounts, depending on the unique properties of the material on which the light is shining. So, the color we see depends on which colors are reflected and which colors are absorbed. For example, a book that looks red to us absorbs more of the green and blue parts of the white light shining on it, and it reflects the red parts of the white light. The same kind of thing thing happens when we look at the ocean.

When sunlight hits the ocean, some of it is reflected back directly (called sunglint), but most of it penetrates the ocean surface and interacts with the water molecules that it hits. Most of the light that is scattered back out of clear, open ocean water is blue, while the red portion of the sunlight is quickly absorbed very near the surface. So usually, the ocean looks blue to us. However, there are many things in addition to just water molecules in the ocean. It is these other things that can change the color that we see.

In coastal areas, runoff from rivers, sand and silt stirred up from the bottom by tides, waves and storms, and a number of other things can change the color of the near-shore waters and make it look brown or tan or even dark green.

However, for most of the world's oceans, the most important things that influence the color of the ocean that we see are phytoplankton.

Phytoplankton are very small (smaller than the size of a pinhead!) single-celled ocean plants that contain a green pigment called chlorophyll. All plants (on land and in the ocean) use chlorophyll to capture energy from the sun. Through the process known as photosynthesis, these teeny-tiny ocean plants convert water and carbon dioxide into new plant material and, importantly for us, into the oxygen that we need to breathe to stay alive.

Although each phytoplankton by itself is tiny, they can reproduce and "bloom" in such large numbers that they can change the color of huge areas of the ocean. We can even measure that ocean color change all the way from space.

Satellites use special instruments that are even more sensitive than the human eye. With them, we can measure the fantastic array of colors of the ocean. Because different types of phytoplankton have different amounts of chlorophyll, they appear as different colors to these sensitive satellite instruments. When we look at pictures of the ocean that are taken by these satellites, we see many different shades of blue, of course, but we also see other colors such as green, yellow and red. These different colors show us where there is phytoplankton, sediments, and other chemicals. This helps us to understand what is in the oceans, and how healthy the ocean is. Comparing pictures taken at different times shows us what is changing in the oceans' makeup and health.

One satellite that is used to take pictures of the ocean from space is called the Sea-viewing Wide Field-of-View Sensor (SeaWiFS). Their Website has many interesting and beautiful pictures that SeaWiFS has taken of the ocean.

Why are Phytoplankton so Important?

These tiny little plants that drift with the currents throughout the ocean play an absolutely critical role for all life on this planet. You may ask "why should I care about a bunch of tiny little floating plants in the ocean that I can't even see, and what could they possibly do for me?"

Well, it is safe to say that without phytoplankton, life on earth as we know it would never have happened and without them, life on earth as we know it would cease to exist. That's pretty important!

Just to give you a few facts to whet your appetite:

  • A teaspoon of sea water can contain as many as a million one-celled phytoplankton
  • The world's phytoplankton generate at least half of the oxygen we breathe
  • Over 99.9% of all the carbon dioxide that has been incorporated into living things over geologic time is buried in marine sediments, and most of that was done by phytoplankton
  • Phytoplankton are the base of the marine food web and therefore, with a few fairly unusual exceptions, they support almost all life in the oceans

These small plants are the beginning of the food chain for most of the planet. As phytoplankton grow and multiply, small fish and other animals eat them as food. Larger animals then eat these smaller ones. The ocean fishing industry finds good fishing spots by looking at ocean color images to locate areas rich in phytoplankton.

The ocean color pictures taken by satellites show scientists where ocean currents are full of phytoplankton. Depending on their color, they can also show where pollutants poison the ocean and prevent plant growth. Even subtle changes in the climate, warmer or colder, more saline (salty) or less saline, affect phytoplankton growth. Since phytoplankton depend upon very specific conditions for growth, they often are the first indicators of a change in their environment.

What is Carbon Dioxide?
And What does it Have to do With the Oceans, Anyway?

Carbon dioxide is one of the gases in our atmosphere that helps to maintain the earth's temperatures. Although it is colorless and odorless, we may notice it because it is the gas used to make the fizz in our soft drinks. It is also used as a refrigerant (dry ice is solid CO2), and in fire extinguishers. Plants, including phytoplankton in the oceans, use carbon dioxide to make the oxygen that we breathe. When we (and all animals) exhale, carbon dioxide is one of the gasses that comes out of our lungs. Scientists use the notation CO2 (pronounced see-oh-two) to represent carbon dioxide.

Click here for a diagram of the Carbon Cycle.

Phytoplankton are a critical part of ocean chemistry and of the world's food and sources. As we learned above, phytoplankton acts as the first link in the ocean's food chain. In addition, during photosynthesis, phytoplankton remove carbon dioxide from sea water and release oxygen as a by-product. This allows the oceans to absorb additional carbon dioxide from the atmosphere. If fewer phytoplankton existed, atmospheric carbon dioxide would increase. If fewer phytoplankton existed, the web of life in the sea would shrink.

Phytoplankton also affect carbon dioxide levels when they die. Phytoplankton, like plants on land, are composed of substances that contain carbon. Dead phytoplankton can sink to the ocean floor. The carbon in the phytoplankton is soon covered by other material sinking to the ocean bottom. In this way, the oceans act as a sink, a place to dispose of global carbon, which otherwise would accumulate in the atmosphere as carbon dioxide.

Other global sinks include land vegetation and soil. However the carbon in these sinks frequently is returned to the atmosphere as carbon dioxide by burning or decomposition. Deforestation contributes to the accumulation of carbon dioxide in the atmosphere by reducing vegetation that takes up carbon dioxide.

Carbon dioxide acts as a "greenhouse gas" in the atmosphere, and therefore may contribute to global warming. Sources of carbon dioxide in the Earth's atmosphere include decomposition of organic matter (such as trees), the carbon dioxide that animals and people exhale, volcanic activity, and human activities such as the burning of fossil fuels and wood. No one yet knows how much carbon the oceans and land can absorb. We also do not know how the Earth's environment will adjust to increasing amounts of carbon dioxide in the atmosphere. Studying the distribution and changes in global phytoplankton using ocean color and other tools will help scientists find answers to these questions. You can learn more about the ocean colors project at the Sea-viewing Wide Field-of-View Sensor (SeaWiFS) Website.

Ocean Pollution and its Sources
While pollution comes from visible sources like oil spills and trash, many little known sources have big impacts as well. These include polluted runoff, invasive species, marine deforestation, careless boaters and ship operators, and many others. Even fertilizers and pesticides used on lawns and farms contribute greatly to the pollution of the oceans.

During recent years the number of beach closing and advisory days have topped 11,000 per year in the United States alone. Many more beaches are polluted around the world, but they are not tested or reported regularly. There are several culprits behind this rampant pollution.

As rain water washes over roads, parking lots, construction sites and commercial and industrial sites, it becomes contaminated with oil and grease, heavy metals, pesticides, litter and pollutants from vehicle exhaust. This polluted runoff flows into storm drains and eventually most of it ends up in streams, rivers and coastal waters. In fact, about 25% of our nation's polluted estuaries and lakes are fouled by urban storm water. In rural areas, rainwater flows over farmland, roads, golf courses and lawns into waterways. The rainwater can become a toxic mix of animal waste, fertilizers and pesticides.

When too many homes and businesses are hooked up to a sewage treatment plant, it can't treat the sewage adequately, especially after heavy rainstorms. The overburdened facilities can, and often do, malfunction. Under these circumstances, untreated wastewater (from emptying sinks and showers, and all the stuff flushed down toilets) is released into local waterways.

Floating debris regularly washes up on the shores of places as remote as Antarctica, and plastic bottles and bags are routinely seen floating in mid-ocean. In a single day in 2000, 850,000 people removed 13.6 million pounds of debris from the world's beaches and coastal waters. On that same day, volunteers discovered nearly 13,000 syringes on the worlds beaches, and found 373 dead marine animals entangled in debris.

Cruise Ships
Floating cities with their own zip codes, cruise ships carry millions of people each year to some of the world's most pristine and sensitive ecosystems. Largely unregulated, cruise ships also discharge huge amounts of waste directly into the water. From raw sewage to toxic chemicals, cruise ships dump huge amounts of waste directly into ocean waters, posing a potential threat to marine wildlife, fragile habitats and human health. Cruise ship impacts have increased exponentially with the industry's dramatic growth. In 1998, 223 cruise ships carried 10 million passengers through some of the world's most sensitive ocean ecosystems. Since then, the industry has grown by an average of 10 percent annually, and is expected to bring more than 49 new vessels into service by 2005.

If you want to help bring an end to the pollution problem, there are three things we can all do.

  • Most importantly, try not to be a part of the problem.
    --Remember that virtually every chemical we use ultimately ends up in the ground water. So, ask your parents to only use soaps and cleansers that are biodegradable and don't contain bleach or antibacterial cleaners.
    --Avoid the use of pesticides and fertilizers on your lawn at home and make sure all of the plastic packaging from the products you do buy are properly disposed of.
    --Never let a helium balloon fry free into the atmosphere, because they bust and fall back to earth, where many animals confuse them with food, eat them, and choke to death.

  • Volunteer to help out in cleaning up your community on Earth Day.
    Every piece of trash you pick up potentially saves the life of an animal somewhere down the line and makes your world just a little cleaner.

  • Write the government officials on every level who represent you and your community and ask them what they are doing to help with this problem.

Overfishing and Whaling
Once vibrant wildernesses teeming with diverse marine life, many of today's ocean ecosystems face the devastating effects of overfishing. A number of species have gone commercially or ecologically extinct, causing dramatic changes in ocean ecosystems. Rebuilding over-fished species will actually increase the amount of fish that can be caught sustainably.

Overfishing occurs when fish are caught faster than they can reproduce, so their overall population declines. Many marine scientists now believe that overfishing is the biggest human impact on the world's oceans. A recent study in the prestigious journal Science showed that overfishing makes ocean ecosystems more vulnerable to harm from other human impacts like pollution.

Evidence of overfishing abounds throughout US waters, including the near-disappearance of fish that were once abundant, and the shrinking sizes of average-sized fish. Today, many fish are caught before they are old enough to reproduce. Overfishing also can contribute to declines in marine bird and mammal populations by reducing their food supplies.

Depletion of fish populations is actually an accepted goal for most fishery managers. Fishermen are encouraged to achieve maximum exploitation by "fishing down" populations to about half their original size. Such goals ignore the role of fish as an integral part of marine food webs.

Valued for their oil, blubber, meat and baleen, many species of whales were hunted nearly to extinction by the 20th century. Even with laws enacted by the International Whaling Commission (IWC), most species haven't recovered. Some countries, like Japan and Norway, still ignore conservation plans, threatening the survival of these awesome animals.

Several scientific concerns must be addressed before the resumption of commercial whaling is even considered, including:

  • increasing our knowledge of stock structure to ensure minimal damage and sustain genetic diversity for each species
  • gathering reproductive data to determine overall sustainability of each species
  • studying the cumulative impacts of environmental variables on each species, including contaminants and prey availability
In addition, as past experience has revealed, ensuring responsible whaling by all nations is a constant struggle due to inadequate enforcement and monitoring capabilities.

From dolphins to whales, sea turtles to sea lions, thousands of animals die each year entangled in commercial fishing gear or in abandoned fishing nets and lines, and in marine debris. Fishing line and nets, rope and other rubbish can wrap around fins, flippers and limbs-causing drowning, infection, or amputation. Several species of dolphins, porpoises and whales are particularly vulnerable to entanglement. Often, these species feed on the same fish that nearby humans are fishing. Other times, they swim with, feed near, or inhabit the same area as those fish.

The Marine Mammal Protection Act (MMPA) provides the only defense for these species. It requires that teams of specialists develop mechanisms to reduce entanglements and to ensure the continued health of marine mammal populations.

Global Warming
Energy from the sun drives the earth's weather and climate, and heats the earth's surface; in turn, the earth radiates energy back into space. Atmospheric greenhouse gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse. Without this natural "greenhouse effect," temperatures would be much lower than they are now, and life as known today would not be possible. Without the Earth's atmosphere, our planet would become extremely cold and barren of life. Instead, thanks to greenhouse gases, the earth's average temperature is a more hospitable 60F. However, problems may arise when the atmospheric concentration of greenhouse gases increases.

The atmosphere consists of nitrogen (about 70 percent) and oxygen (about 20 percent). The other ten percent consists mostly of carbon dioxide, water vapor, and several "trace" gases such as neon and argon.

Like the glass roof and walls of a greenhouse, the Earth's atmosphere keeps its surface much warmer than it would be without the "greenhouse effect." How?

Energy from the sun arrives as short-wavelength radiation (light), while the Earth emits long-wavelength (infrared) energy back into space. The hotter an object is, the shorter the wavelength of the radiation it emits. The short-wavelength sunlight easily penetrates the atmosphere and warms the Earth. However some of the long-wavelength energy emitted from the Earth is absorbed by the atmosphere before it escapes into space.

Carbon dioxide, water vapor and other gases in the atmosphere are responsible for absorbing escaping long-wavelength energy. Thus, the Earth keeps some of the heat that would otherwise have been lost to space.

The concentration of carbon dioxide in the atmosphere has changed in the last hundred years. Before the Industrial Revolution, carbon dioxide levels stayed nearly stable for thousands of years. Since human beings developed a fossil-fuel- based global economy and lifestyle, the amount of atmospheric carbon dioxide has increased dramatically. Since the beginning of the industrial revolution to 2004, atmospheric concentrations of carbon dioxide have increased nearly 35%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. This increase means that less long-wavelength energy emitted from the Earth can escape to space. These increases have enhanced the heat-trapping capability of the earth's atmosphere. The heat-trapping property of these gases is undisputed, although uncertainties exist about exactly how earth's climate responds to them.

Why are greenhouse gas concentrations increasing? Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide. Plant respiration and the decomposition of organic matter release more than 10 times the CO2 released by human activities; but these releases have generally been in balance during the centuries leading up to the industrial revolution, with carbon dioxide absorbed by terrestrial vegetation and the oceans.

Many scientists believe this increase in the heat-trapping capability of the earth's atmosphere can lead to a gradual warming of the Earth, but others believe that different factors counteract this warming effect. For example, cloud cover reflects sunlight before it ever reaches the Earth, thus reducing the amount of sunlight that reaches the Earth's surface. For another example, sulfate aerosols, a common air pollutant, cool the atmosphere by reflecting light back into space, but sulfates are short-lived in the atmosphere and vary regionally. Studying these processes is difficult, because they are complicated.

Ocean color information provides one of the many tools scientists use to try to find what changes are occurring, and how they may affect us. According to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities.

Rising global temperatures are expected to raise sea levels and change precipitation and other local climate conditions. Changing regional climates could alter forests, crop yields, and water supplies. It could also affect human health, animals, and many types of ecosystems. Deserts may expand into existing range lands, and features of some of our National Parks may be permanently altered.

Most of the United States is expected to warm, although sulfates may limit warming in some areas. Scientists currently are unable to determine which parts of the United States will become wetter or drier, but there is likely to be an overall trend toward increased precipitation and evaporation, more intense rainstorms, and drier soils.

Unfortunately, many of the potentially most important impacts depend upon whether rainfall increases or decreases, which can not be reliably projected for specific areas. However, most scientists agree that this Greenhouse effect is responsible for accelerating the melting of the polar ice cap, which is changing the temperature of our oceans. This has devastated coral reef formations around the world, which is home to innumerable species of marine life. A change of only 1-2 degrees can destroy these delicate formations.


1, There are areas of the ocean with relatively large concentrations of nutrients that animals and plants use as food substances. In these areas you see a lot of phytoplankton the plant portion of plankton), especially in the spring. Why do some areas have greater amounts of phytoplankton? Where would be the best place for deep-sea fishing?

2. If a zooplankton, a very small animal type of plankton, eats a phytoplankton, generally speaking, what happens to the zooplankton and the carbon that remained in the phytoplankton?

3. What is an example of the lowest level of the "food chain" on land?

4. Scientists use two types of satellites to study the environment. A geostationary satellite remains above the same spot on the Earth's equator from an altitude of about 22,500 miles, and can "see" an entire hemisphere all the time. A polar orbiting satellite travels in a circular orbit, passing above the North and South Poles while the Earth rotates beneath it. This type of satellite can "see" details as small as a mile or less. Which of these satellites probably would be better for our ocean color instrument? Would one prove better than the other to track hurricanes and other large weather systems?

5. How do the atmosphere and the ocean interact?

6. How could global warming affect sea levels? Why is global warming important?

7. Where do plankton grow?

Project: Make a Greenhouse
Materials needed:

  • Two cardboard shoe boxes
  • Clear plastic wrap
  • Two regular "weather type" thermometers
  • Desk light with 15 watt or larger bulb

1. Place some paper towels loosely in the bottom of each shoe box, then lay the thermometer on the towels.

2. Cover the open top of one box with plastic wrap, taped to the side of the box; leave the other box with the top off (open).

3. Place the boxes side by side, and move the desk light so it shines evenly into both boxes.

4. Record the temperature in each box every minute for 10 minutes.

5. Plot the temperatures on a graph with time as the "x" (horizontal) axis and temperature as the "y,' (vertical) axis.

Discuss the differences you see in the observed temperatures in the two boxes, and why this is happening.

Try replacing the paper towels in each box with black paper. Repeat the experiment. What differences do you note?

Photo Credits:
Color globe and map: Sea-viewing Wide Field-of-View Sensor (SeaWiFS) project
Carbon dioxide molecule: Russell Knightly Media