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World Ocean Day: What is ocean sustainability?

As we approach World Ocean Day this year, we decided to explore the topic of ocean sustainability, and reveal how you can help save our oceans.

Ocean Sustainability

The ocean is one of the most important places on planet earth and home to thousands of different plant and animal species. To celebrate World Ocean Day this year, we’re discussing all things to do with sustainable oceans.

We’ll be exploring the difference between oceans and seas, why the ocean is so important, the current threats to ocean sustainability, and how the Sustainable Development Goals are attempting to protect the ocean. Finally, we’ll discuss how you can protect and save the ocean on an individual and community level.

What are oceans? 

Technically, there is just one ocean globally, but we often divide it up into five major sections: the Pacific, Indian, Atlantic, Arctic and Southern (or Antarctic) oceans. Ocean ecosystems make up 70% of the earth’s surface, hold an enormous amount of life, and act as a buffer against many global issues, including over-harvesting and pollution. 

If you need more confirmation of how enormous the oceans are, they contain 97% of the earth’s water and represent 99% of the living space on the planet by volume. Even though the ocean might feel like a mysterious entity to a lot of us, it’s a vital ecosystem that supports the entire planet, so it is essential that we look after it.

Oceans vs seas 

We often talk about the sea and ocean as if they’re interchangeable, but they’re actually not the same. While the ocean is the entire mass of water surrounding land on earth, a sea is a smaller section of the ocean that is normally contained by land to some extent. The only exception to this rule is the Sargasso Sea, which is enclosed by ocean currents. 

Generally, the sea is more shallow than the ocean, but this is not always the case. For example, the Caribbean Sea is deeper than the average depth of the ocean. However, even the largest sea is smaller than the smallest ocean – the Mediterranean Sea is 2.9 million square kilometres compared to the Arctic’s 14.06 million square kilometres.

Why are the oceans important? 

The oceans are extremely important for many reasons, but we’ll divide these into three main categories: the climate, earth’s ecosystems, and our economies and livelihoods. This won’t be an exhaustive list, but it might help you to understand why the oceans are so vital.


You may have heard before that the warming of the ocean is a large contributor to climate change, but we’re going to delve into some more detail on this topic. The ocean has absorbing properties, comparable to a sponge, meaning that it can absorb excess heat in the climate system. Although this is a very useful quality, it also means that the temperature of the sea has increased by almost 1 degree celsius over the last century. 

As discussed in our open step about climate change and the ocean, this may not sound like much, but the ocean and its inhabitants are sensitive to temperature change. Temperature changes can affect the distribution and movement of marine life, including fish, shellfish and turtles, which can, in turn, affect fish stocks in certain areas. 

This isn’t the only impact on the climate, however. The ocean is responsible for extreme weather patterns, including monsoons, cyclones, and El Nino. Over the years, we’ve started to experience more harmful extreme weather events, which reflects the change in ocean temperatures. 

If you’re interested in learning more about the causes of climate change or solutions to climate change, we have some excellent courses available for you to try, where you can learn more about ocean warming. In addition, you can learn how to reduce your carbon footprint by checking out the tips in our blog. 


The ocean is an essential ecosystem, and any changes to its natural state can result in wildlife disruptions. In our open step about ocean warming, experts at the University of York discuss how ocean warming affects species in four different ways: distribution, population size, food chains and habitats.

These disruptions mean that wildlife may move to more favourable environments, especially large mobile species such as dolphins and sharks. Additionally, certain marine life may see boosts or drops in population size, which can cause disputes in different fisheries.

Small changes to marine life low down in the food chain can affect wildlife at all different levels, which can have a negative effect on a species chance of survival. Finally, habitat changes can be hugely detrimental to marine life. The Great Barrier Reef has suffered from five major coral bleaching events since 1998, and some experts believe that coral reefs will continue to disappear.

It is therefore vital that we do our best to protect these essential ecosystems, which you can learn more about in one of our courses. Whether you’re interested in ecology and wildlife conservation or marine ecosystems in the Indian Ocean, we have something for you.

Economies and livelihoods

Seeing as the ocean surrounds us, it’s unsurprising that it’s such an important part of our economy and livelihoods. This importance is amplified even more in coastal areas. In fact, nearly half of the world’s population rely on fish for 20% of their daily protein intake, with this rising to beyond 70% for some coastal communities.

Thinking more about the economy, the market value of marine and coastal resources and industries is estimated to be $3 trillion per year, which is roughly 5% of global GDP. This is hugely significant and demonstrates how the ocean contributes to poverty eradication by creating jobs and sustainable livelihoods for communities and individuals.

On a more human level, the ocean is also an incredible resource for our physical and mental health. Spending time by and in the sea is a relaxing, inspiring and sometimes healing process, and this is a concept recognised as ‘Blue Mind’ by the UK government.

What does ocean sustainability mean?

Ocean sustainability is all about approaching ocean management in a way that protects it and the services it provides. The oceans are essential to planet earth, and the coastal areas, in particular, contain a wide range of different habitats and ecosystems. 

As we discussed in one of our previous blog posts, the definition of sustainability more generally is any action or process we perform that causes little or no harm to the natural world or living creatures, including other humans. It’s all about finding ways to meet the demands of life without causing detriment to society or compromising future generations. This sentiment can be applied to oceans more generally.

What is World Ocean Day?

This year, the United Nations World Oceans Day is on June 8thand has the theme of The Ocean: Life and Livelihoods. The United Nations describe World Ocean Day as a way of informing the world about the impact and importance of human actions on the ocean. After educating people, the intention is to “develop a worldwide movement of citizens for the ocean, and mobilize and unite the world’s population on a project for the sustainable management of the world’s oceans”.

At FutureLearn, we believe that it’s important to celebrate World Ocean Day and educate ourselves around topics related to the ocean. That’s why we have a range of courses that can help you learn more about the ocean, such as our Exploring Our Ocean course, where you can discover how our lives impact the ocean depths and marine life.

Current issues affecting oceans and sustainability 

There are several significant issues affecting the ocean right now. These are all things we need to face head-on and attempt to find solutions for in the future if we ever want to have a sustainable ocean. Below, we describe some of the most pressing issues facing our waters.


Whether you’ve seen the documentary ‘Seaspiracy’ or not, you might be aware that overfishing is a big issue the oceans are facing. The Food and Agriculture Organization of the United Nations stated that the amount of overfished stocks has tripled globally over the past half a century, and one-third of assessed fisheries in the world are being pushed beyond their biological capacity.

Overfishing can obviously be devastating for marine ecosystems. There is a lot of bycatch – which is when unwanted sea creatures are captured accidentally while fishing for different species. This leads to a lot of needless and unnecessary loss of life. In addition, overfishing is bad for many people’s livelihoods. Lots of the world’s population rely on fish for protein, but it is becoming harder to access fish.

If you saw Seaspiracy, you might have seen that they recommend a total ban on eating fish to combat overfishing. However, there has been some backlash to their approach and claims. Marine biologist, Daniel Pauly, suggests that claiming veganism will save ocean diversity undermines the potential people have to work together and push for policy and rule changes in the marine industry.

Chemical pollution 

Another big threat to our ocean comes in the form of chemical pollution. Our open step by the University of York suggests that there are three major pathways that lead to chemical pollution ending up in the water. These pathways are:

  • Direct input. This is when waste is dumped directly into the ocean, whether this waste is from an oil spill or sewage disposal. Although the ocean is huge, and lots of waste will disperse evenly across the ocean, some chemicals are hydrophobic. This means they might bind to the ocean floor and remain for centuries.
  • Atmospheric deposition. A lot of chemicals are released into the air, and these are known as volatile chemicals. When there are meteorological changes in air pressure, humidity or rain, some chemicals can be deposited onto the earth’s surface, including the ocean.
  • Indirect exposure. There are many different types of indirect chemical exposure. This can include pesticides and herbicides running off of land into the sea or runoff water from floods getting into the ocean.

Carbon levels 

The amount of carbon dioxide in the ocean is increasing as we release more and more Co2 into the atmosphere. This is because the ocean absorbs 30% of Co2 in the atmosphere, so the more we burn fossil fuels and allow deforestation, the more carbon the ocean will absorb.

An increase of carbon in the ocean results in an increase of hydrogen ions and a lower pH. This process is called ocean acidification and has many negative repercussions on marine life. One example is that shellfish and coral find it harder to build and maintain their shells, skeletons or structures.

Habitat loss and damage 

We’ve already explored how some habitats, such as coral reefs, are suffering due to the way we treat the ocean, but this is unfortunately only the tip of the iceberg. To learn more about this topic, you can try our Tackling Environmental Challenges for a Sustainable Future course. Below are some examples of habitat loss or damage that the ocean is facing:

  • Pollution from factories and cities are damaging reefs, birds and fish
  • Wetlands are being filled in for development purposes
  • Inland dams are cutting off fish migration routes
  • Deforestation is creating soil erosion and blocking sunlight from coral reefs
  • Destructive fishing techniques like poisoning are wrecking habitats
  • Tourist boats and divers are damaging fragile reefs and ocean ecosystems

Why the oceans are key to sustainability goals 

As we discussed in more detail in our blog about living sustainably, the Sustainable Development Goals (or SDGs) were created in Rio de Janeiro in 2012 at the United Nations Conference on Sustainable Development. They were an attempt to create a series of goals that would tackle the most important challenges we face today by the year 2030.

Oceans are key to sustainability goals because the main objective of SDG 14 is to “conserve and sustainably use the world’s oceans, seas and marine resources for sustainable development”. The aim is to unite ocean stakeholders together so that a common framework and ocean science can help them achieve more sustainable oceans by 2030.

It’s not just SDG 14 that the oceans have an impact on, however. As the World Economic Forum has stated, the oceans hold the key to solving many of the earth’s problems, from eradicating hunger and poverty, to fighting disease, creating jobs, ensuring peace, and combating the climate crisis. 

How we can help the oceans 

Now you understand more about why the ocean is so important and the struggles we’re facing, it’s time to act. In our open step by the University of Southampton, experts explain what you can do to help. On an individual level, they suggest we can recycle our waste, fly less frequently, eat ethically and locally sourced seafood, stop using single-use plastics, and volunteer to clean up our beaches and oceans.

As a global community, we need to start working together with peers, pressure groups and local governments to push policies and legislation regarding sustainable ocean management and marine conservation. A Forbes article on the blue economy also suggests that we promote greater ocean literacy. This means we should foster a greater sense of responsibility and knowledge surrounding the oceans – children should know just how dependent we are on the ocean as a life support system.

Final thoughts

It may seem difficult to know where to start, but educating yourself is the first step to making changes and discovering ways you can help save the ocean. Perhaps you’ll find that there are some great initiatives or volunteer programs near you, or you might even decide to enter a career where you can have a positive impact, directly or indirectly. 

Hopefully, we’ve encouraged you to think about what you might be able to do to reduce your impact on the ocean, whether that’s taking an online course, speaking out about these issues, or taking practical action. With World Ocean Day coming up, it’s the perfect opportunity to make a difference.

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