50% to 70% of oxygen comes from the ocean. That is more than the oxygen percentage given by all the rainforests in the world.

The ocean is the foundation of all life, an extraordinary and largely unexplored place. The 5 oceans, namely the Pacific Ocean, Atlantic Ocean, Indian Ocean, Arctic Ocean, and Southern Ocean (Antarctic Ocean) cover about 70% of the Earth. The ocean is a vital resource, but it has faced many threats due to human activities.

The main aims of World Oceans Day are to remind people about the importance of oceans, to identify the threats that oceans face due to human activities, and to discover and implement measures to protect the oceans.

Importance of Oceans


50% of life-giving oxygen comes from the ocean. Tiny plankton and ocean plants absorb CO2, and through the photosynthesis process, O2 is released back into the atmosphere. So, every time you breathe, half of the oxygen inhaled comes from the ocean.

The oceans are home to an incredible diversity of life. Scientists think that there could be more than 2 million species living in the oceans, from tiny plankton, which form the foundation of many ocean food chains, to the biggest creature, (blue whale).

Weather and Climate

Oceans play an important role in keeping our planet’s temperature and weather in balance. 98% of the heat from the sun’s rays is absorbed by the ocean. This heat is then moved around the Earth via currents, so the warm water at the equator is moved around the Earth up to the poles.

Without the oceans, our planet would be much warmer. Water is really good at storing heat and there is lots of water in the oceans.

Water cycle

The ocean plays a key role in the water cycle. When the sun shines and the warm currents heat the ocean, water evaporates. This forms clouds and it also increases the air temperature and humidity, creating weather. The clouds then get blown back over the land, and it rains, this water is used by every living being on the planet before making its way back to the ocean. Without this process, most of our planet would be a desert.

Food and economic uses

Fish and seafood form a major source of protein in our diets. We use seaweeds to make useful chemicals. Billions of people around the world rely on the oceans for their jobs.


The ocean can also provide numerous ways to generate renewable energy through waves, tides, and winds.

Threats to oceans

Climate change

The ocean and climate change are inextricably connected. Rising temperatures are having huge impacts on the ocean. For example, coral reefs are extremely sensitive to warming waters. This is the cause of the bleaching and death of coral reefs.

Ocean acidification

Ocean acidification is caused by the increased levels of carbon dioxide in the atmosphere. The pH of water is constantly decreasing as the oceans absorb higher levels of CO2. It has been shown that lower pH values can affect the behaviour of marine species, putting them at life-threatening risk.

Plastics and ocean debris

Studies show that more than 80% of marine pollution originates on land and is caused by direct human impact. An estimated 8 million tons of plastic end up in our oceans each year. The majority of plastic debris in the ocean is caused by littering, mainly disposable plastic items (food wrappings, plastic bags, and bottles), which, if disposed improperly, will end up in the waterways and eventually in the ocean.

At first, plastic pollution may stay in coastal waters, but it is soon picked up by rotating ocean currents (gyres) and transported literally all around the world. This leads to the formation of garbage patches, which are plastic accumulation areas in the centre of the ocean’s gyres. The biggest is the Great Pacific garbage patch between Hawaii and California.

Plastic pollution has a devastating impact on sea life and ecosystems. The most obvious impact is the damage plastic items cause to animals, which includes suffocation, entanglement, laceration infections, and internal injuries. Yet plastic in the ocean also harms human beings, exacerbates climate change, and is detrimental to the global economy.

Fishing and fishing gear

Overfishing is incredibly destructive for the ocean. Fish that were once extremely common, such as the bluefin tuna, are now becoming endangered species. Fishing nets, usually made of plastic, are often abandoned in oceans. About 20% of the ocean’s plastic pollution comes from industrial fishing.

Shipping and transport

90% of global trade currently uses sea routes but shipping can be harmful for the ocean as the waste and oil spills generated by ships pollute the ocean water. The noise produced by shipping has been demonstrated to be harmful to marine organisms, as marine life is extremely sensitive to noise as many species rely on underwater sounds for basic life functions.

Solutions to minimize threats to the ocean

Establishing marine reserves

Marine reserves would preserve all kinds of marine life, from corals to sharks and whales, stopping unregulated fishing, drilling and mining to restore a pristine environment for all species to thrive undisturbed.

Reducing and preventing pollution

  • Eliminating coal combustions to reduce the emission of harmful gases.
  • Completely transitioning from fossil fuels to renewable energy as soon as possible.
  • Controlling the production of coastal pollution and involving local communities in monitoring the coastal areas.
  • Implementing a ban on single-use plastic items, like straws and plastic bags, in order to reduce the amount of plastic in our environment.

According to data from the European Parliament, single-use plastics are responsible for 49% of all marine pollution.

Sustainable energy and lower emissions

It is essential to work towards reducing shipping emissions effectively. Ocean-based renewable energy production has begun. Now all we need to work towards is increasing investments to enable the adoption of new technologies.

Finally, it is proven that human activities lead to the destruction of the marine ecosystem. So, let us protect the ocean, as it is one of the Earth’s most valuable natural resources, and the ocean is Earth’s life support system.

Written by:

Sandini Gihansa

1st Year Undergraduate

Faculty of Science

University of Colombo.


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