Oceans are Indispensable

Oceans give life! The Earth needs oceans because all the elements on the planet are carefully balanced, including water, air, soil, and living things. All of these elements form a community we call an ecosystem, which could be anything from a puddle to a planet. Everything in an ecosystem interconnects, rather like the vital systems in your body. For instance, imagine what would happen if your kidneys or heart stopped working.

Here's how the ocean contributes to the planet's ecosystem:

• Oceans help regulate climate. Their currents absorb heat in the summer and release it in the winter. Water heats up more slowly than land, but holds its heat longer.
• Oceans supply huge amounts of oxygen. Ocean plants (especially tiny phytoplankton) provide more oxygen than rain forests — between 30 and 50 percent of the planet's supply.
• Oceans supply most of our water. Since time began, the same amount of water has splashed around in an everlasting circle called the hydrologic cycle. It begins when the sun's heat changes water to vapour (evaporation). Plants also give off vapour through their leaves. Then, when the vapour cools, it falls to earth as rain, snow, or sleet. The oceans play a huge part in this cycle: each year, about 330,000 cubic km of water evaporate from oceans! (The salt stays behind, by the way.) In all, oceans provide 97.5 percent of the Earth's water and cover about 75 percent of its surface.

What we do affects the oceans, no matter where we live. Pesticides sprayed on crops hundreds of kilometres inland can wash or fall into a nearby stream and eventually gurgle out to sea. Garbage dumped in the Pacific and Atlantic oceans can make its ugly way through currents and tides to Antarctica's shores.

By protecting our oceans' health, we also protect the planet. Of course, a healthy planet is good news for all living things, including us. To help oceans, we must act.

• Scientists define oceans as the whole bodies of salt water that cover nearly three-quarters of the globe's surface.
• All the oceans are actually one enormous ecosystem, connected by great currents flowing from hemisphere to hemisphere.
• The planet's huge ocean consists of seven connected oceans: the Arctic, Antarctic, North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian oceans. Also included are seas, such as the Gulf of Mexico and the Mediterranean.
• Oceans and seas can be 10 kilometres deep.
• Oceans are saltiest where they are very hot, such as the Red Sea, or very cold, such as the Arctic.
• Unlike countries, oceans have no boundaries. No one knows exactly where one ocean becomes another.
• All water drains into oceans eventually.

Besides providing the world with water, oxygen, and climate control, oceans give us many other benefits:

• Food: Seafood is the main source of protein for nearly half the five billion people on Earth, who eat 80 to 90 million tonnes per year.
• Medicines: We have developed anti-leukemia drugs from sea sponges, bone-graft materials from coral, and anti-infection agents from shark skin, to name a few medical gifts from the sea. Half of all prescription drugs come from wild things!
• Products: We use algin from kelp in ice cream, drinks, medicines, paper, cosmetics, ceramics, paint, insecticides, and other substances.
• Money and jobs: Fishermen catch about 90 million tonnes of fish each year in the world's oceans. More than 200 million people work in the marine fishery, with more than Five million people fishing full-time in Southeast Asia alone.
• Tourism: The sea draws countless people to its shores and waves for swimming, snorkelling, sailing, surfing, photographing, camping, and more.
• A gene pool: Scientists use the genetic material in wild species to develop improved crops, new drugs, medicines, and more. So, even tiny snails, leeches, or seaweeds may be far more important than we realize.
• Transportation: For centuries, we have explored our world by travelling across oceans.
• Beauty: The ocean provides a feast for our senses, soothes us, and inspires our creativity.

Guess what? An ocean is like an organism that breathes, drinks, and eats. All the living and non-living parts of the ocean ecosystem (such as plants, air, animals, and water) help this large, soggy creature function. And just like humans, the whole ocean system needs every single part to work properly.

Ocean creatures are like you and me. They get energy from food. The energy in food begins with the sun in an amazing process called photosynthesis. (Some scientists say that the most important mechanism on Earth is photosynthesis!) This complicated process allows ocean plants to capture and store energy from the sun. This energy helps plants grow, and, in turn, it is passed on to ocean creatures that eat the plants. Just like plants on land, ocean plants release oxygen. In fact, they provide between 30 and 50 percent of the planet's entire oxygen supply.

A huge and vital part of the ocean ecosystem is plankton. These tiny plants (phytoplankton) and animals (zooplankton) feed an amazing variety of ocean creatures. You could say that humble plankton provide food for the whole ocean. For example, small fish like herring eat plankton. Larger fish, like cod, eat the herring. Even larger fish, such as the mackerel shark, devour cod. Tiny bacteria and fungi serve as ocean recyclers. They break down dead plants and animals into simple substances that plant roots slurp up to help them grow.

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