What is ocean plastic pollution and how can we reduce it?

There are trillions of pieces of plastic floating in the oceans. Some estimates put the total figure at 270,000 tonnes of plastic, or 10 times the weight of the Statue of Liberty.

IBTimes UK spoke to Tamara Galloway of the University of Exeter about where ocean plastic pollution comes from, why it's harmful and what we can do about it.

If you throw plastic in a bin, why does it end up in the ocean?

About 50% of all the plastic we produce every year is for things we use once and then throw away after one use. About 10% of that discarded litter will end up in the ocean. It's a lot of the things we use in everyday life that we throw away. Marine plastic pollution can come from landfill sites and a portion of it comes from fishing activities.

How much plastic is there in the ocean?

It's estimated that there are around about 5 trillion pieces of plastic floating on the surface of the ocean at any one time. But that's only a tiny fraction of the plastic we think is actually in the ocean. It gets eaten by animals, broken down into smaller pieces and it will eventually sink to the ocean floor.

What kind of plastic ends up in the sea?

There's been a lot of research on the types of plastic that ends up in the marine environment and on beaches, much of it based on beach litter surveys. First you have to ask, what do we mean by plastics? A lot of effort has gone into characterising and counting all the things you can find on the beach – like cigarette butts, cotton buds, bottles and bottle tops, plastic cutlery and packaging. By far the highest percentage is small fragments of plastics called nurdles.

Does as much recyclable plastic end up in the ocean as non-recyclable plastic?

I would say it's roughly even. There are certain types of plastic that turn up more than other kinds. The things that we use most in daily life are the things that appear most in the oceans, regardless of whether they could have been recycled or not. There are four main plastic types that we see in the ocean: polyethylene, polypropylene, polystyrene and PVC. These are the four we use most in daily life.

Are some countries worse polluters than others?

A number of studies have looked at which countries are producing the most in terms of littering. Interestingly, the Far East, China and countries in the southern part of the globe are producing vast quantities of plastic waste. That's largely because the waste disposal methods available for countries that are starting to use plastics are not mature enough to cope with the volume that is being used and thrown away. Countries find it particularly difficult to constrain contamination into the environment if they don't have the infrastructure.

Does plastic pollution affect most oceans equally, or are some much worse than others?

It's very widely distributed around the world. Plastics are lightweight and durable. They're moved by winds and tides for very long distances, and very quickly, and they're highly persistent and don't break down. The marine environment is governed by winds and tides, and so plastics tend to accumulate in certain areas more than others.

One area of accumulation is the great Pacific garbage patch – how bad is the plastic pollution there?

The great Pacific garbage patch is a very big area – about 700 square kilometres. It's a large area where plastics are buoying around at higher concentrations than elsewhere in the oceans. It's not really visible to the naked eye. It's not a giant floating island of plastic. It's an area with a higher accumulation of plastic than the rest of the oceans. A lot it bobs about just below the surface. The great Pacific garbage patch is not the only one of its kind, though. The five main oceans of the globe each have their own gyre where plastics collect.

What are the environmental impacts of ocean plastic?

There are a number. If you look at larger pieces of plastic, what they can do is entangle animals and drown or injure them. Some marine animals eat the plastic, which can cause blockages in their intestines or alter their feeding. Larger pieces of plastic floating in the ocean can also support invasive species that be moved long distances over the ocean. They're also taking different kinds of pathological microbes into areas they wouldn't otherwise go.

What about tiny, microscopic pieces of plastic?

When you look at tiny pieces of plastics, known as microplastics, there are some similar problems. People might ask, well, if these fragments of plastic are so small, is it really such a problem? But these microplastics overlap with the size range of the preferred prey for lots of marine organisms. Many filter-feeding organisms eat tiny pieces of floating material. The plastics get ingested as well. They have a similar effect on filter feeders as the larger pieces of plastics on other animals.

Can eating plastics lead to problems with animals' reproduction too?

This is one of the big issues. Plastic has a hydrophobic surface, which attracts substances that don't dissolve well in water. Many of the contaminants in the marine environment are hydrophobic too. So when there are contaminants floating around in the ocean they collect on the plastics. What happens if that is then ingested into an animal? Do the contaminants pass out or start to accumulate up the food chain? In many animals consuming some of these pollutants is linked to reproductive problems.

Could these hotspots of ocean plastic pollution be cleaned up?

One of the issues is – especially if you're looking at the Pacific and the Atlantic – you're talking about some areas hundreds of miles from the nearest shoreline. Although it's a nice idea to go and clear them up, you would have to travel all the way there and get plastics from a vast area and take them all the way back again, so it's not really practical. Clearing them up is something we need to think about, but the best thing to do is to stop throwing plastic in the ocean in the first place. We could make a lot of difference by addressing the behaviours and the economics of the way we use plastic.

What can people can do to reduce their plastic waste?

There are some really good schemes that people have put in place – not just reducing the plastic you buy but changing your behaviour. So for example, bringing a reusable cup with you instead of buying a disposable coffee cup with a plastic lid every time. Making sure you don't use straws, plastic cutlery or one-time disposable plastic bottles are a couple more.

What are organisations doing to help cut back on plastic waste?

There are plenty of interesting developments – businesses are looking at the circular economy and how to avoid spending so much time and money making materials that we're only going to use once and throw away. There's a mismatch in how we're using things and how we're designing them, so reassessing the design is a key step.

What is the government doing about the issue?

One of the biggest breakthroughs recently is the microbead ban in the UK. My colleagues and I gave evidence to the environmental audit committee on the issue and the UN also considered our research on microplastics and plastic debris in the oceans as part of their laws of the oceans review.

We've had the introduction of charging for plastic bags. That's one of those great pieces of legislation that led to a huge decrease almost immediately in the number of plastic bags used, which is a great example.

What's the next breakthrough that could help reduce ocean plastic pollution?

The next thing is how we can reduce plastic input into the environment overall by supporting manufacturers to reduce the amount of plastic they use and to make green plastics that degrade better. It's got to be a multi-pronged attack. Reduce our use more, recycle more and replace with alternatives.