The Ocean: Earth's life support

It's not called the blue planet for nothing. The ocean covers up to 71% of the Earth's surface and 90% of the biosphere. It is integral to life and provides anywhere between 50 to 80% of the planet's oxygen, making it a vital part of the carbon cycle. The ocean's origins are still unknown, but it is thought to have formed 4.4 billion years ago, providing a catalyst for early life-forms.

Despite its sheer size, we actually know very little about the ocean. In fact, over 80% of this underwater realm has yet to be mapped or explored. Scientists are working to unlock its mysteries, which could help us better understand environmental change and how to manage vital ocean resources in times of climate change.

We do know that the ocean plays a major role in regulating the Earth's climate by absorbing solar radiation, distributing heat and driving weather patterns. But climate change is already starting to disrupt this balance, affecting the ocean's ability to perform key ecosystem tasks, such as carbon storage and oxygen generation.

The ocean is home to at least 230,000 known species. Coral reefs on the sea floor provide a safe-haven for invertebrates like crabs, starfish and mollusks, as well as colorful reef fish. Plant life flourishes in the shallow depths, while bigger creatures like sharks, whales and dolphins roam the deep open waters.

Unsurprisingly, scientists also think up to two-thirds of all ocean species may still be undiscovered. But researchers are finding new species every year — many of them unlike anything found before, such as this squidworm (pictured), discovered in the Celebes Sea in 2007. What else might be lurking down there is anyone's guess.

But the ocean is under pressure. One of the most obvious examples being the increase of coral bleaching events in reefs around the world. Increased temperatures and pollution stress corals, causing them to expel a special kind of algae which allows them to grow and reproduce, leaving behind a ghostly skeleton. Some corals can recover, but prolonged stressors increase the chances of reef mortality.

Climate change is also seriously impacting marine species, with recent research showing that local populations of fish, mollusks and crabs are disappearing at twice the rate of land species. Extreme temperatures are the main culprit, as the ocean offers fewer places to hide from the heat. Sadly, the majority of ocean species won't be able to evolve fast enough to adapt to the changing conditions.

In the cryosphere — parts of the Earth's surface covered in solid water, including ice and snow — atmospheric warming is causing the melting of glaciers and ice. The current melting event is already contributing to global sea level rise and could also lead to higher levels of ocean acidification, thanks to methane released from seafloor permafrost in the Arctic Ocean.

Humans are inextricably linked to the ocean. For thousands of years communities have thrived along the coast, relying on it for food and livelihoods. Today, more than one billion people live in low-lying coastal regions which are likely to be impacted by rising sea levels.

But this connection has come at a cost. Just 13% of the world's oceans are completely free from human activities such as fishing, with almost no true wilderness left along coastal areas. Technological advancements mean even the farthest reaches of ocean in the Arctic are no longer untouched. Protecting the remaining wilderness will be a challenge for generations to come.