In partnership with Volvo Ocean Lovers Festival

By Felicity Bonello

For the most part we’ve done the research, joined initiatives like Plastic Free July, and read the articles around the damage created from mismanaged waste dumped in the oceans each year, and yet in the past ten years, we’ve still made more plastic than the last century. It’s hard to fathom, but at this rate it’s projected that by 2050 the populatuon of fish will be outnumbered by our dumped plastic. Education and answers are key. On the eve of the Volvo Ocean Lovers Festival and the incredible program of activities that aims to share hope, solutions and action for the ocean, the Green + Simple team are delving into the science and issues surrounding ocean plastics and their intersection with sub-lethal toxicity; with a little help from Dr Charlene Trestrail, Research Associate, Climate Change Cluster, UTS. 

Ocean plastics and sub-lethal toxicity

When we hear the word toxic, we usually think of mortality. And sure, when you consider 100 million marine animals succumb to plastic waste each year, death is certainly part of toxicity. However, what scientists have uncovered is when it comes to marine pollution, it doesn’t necessarily eradicate an animal outright, rather, another layer of toxicity, called-sub lethal toxicity is having an effect on the overall health of marine life. 

“Just because you’re alive, doesn’t mean you’re healthy,” explains Dr. Charlene Trestrail. 

“For example, an animal that’s exposed to pollution may have a slower growth rate, or it might produce fewer offspring. Or in cases where a whale might eat a plastic bag, while it’s unlikely one plastic bag will kill a whale, it might interfere with digestion, and that whale might have problems getting the energy it needs from its meal. When we talk about pollution and toxicity there’s this really interesting layer of sub-lethal toxicity and that’s where we find that a lot of ocean plastics sits.”

The chemical and physical effect of ocean plastic

We know chemicals can attach to the surface of plastic in the ocean. Indeed, heavy metals tend to absorb onto the surface of plastic and once an animal makes a meal of it, those chemicals on the surface can be released inside the body. We find this primarily with microplastics. But ocean plastic is not waiting for the next oil leak to wreak havoc and attach its heavy metals, because, by its very nature, plastic is full of chemicals that can leak out. 

“Plastic is a cocktail of different chemicals. Plasticizers and other things we put into plastic during manufacturing actually leak out into the environment. That environment might be water and the ocean or that environment might be stomach contents. It’s a really unusual type of pollution because it’s a physical thing and it’s a chemical thing at the same time,” says Dr Trestrail. 

“It almost gives plastic a double whammy because it can have physical effects like when we see birds tangled up in plastic netting, and it can have the chemical effects when it’s leaking chemicals into the stomach of animals that eat it. It’s a really odd kind of pollution we’re dealing with here.”

When plastic becomes microplastic

According to Dr. Trestrail, scientists estimate there’s over five trillion pieces of plastic in the ocean, but because we’re releasing plastic every day, it could actually be more. And while many of us are trying to do the right thing with recycling, because it is so lightweight it can easily escape the waste system. We need to consider all the plastic we use and dispose of on land has the potential to escape and become pollution in the ocean. 

“The problem here is that, while we might accidentally release one plastic wrapper, over time that plastic in the ocean is exposed to salt, wind and sun and it gets brittle, and then it starts to fragment into microplastics.

One piece of plastic can potentially become thousands of smaller pieces of plastic that effect a whole range of animals, which are needed to keep the ecosystem functioning and healthy. Furthermore, it’s hard to quantify how many microplastics will come out of one big piece of plastic and once they’re out in the environment, it’s incredibly tricky to capture them again. Take the Great Pacific Garbage Patch for instance. Many people would assume this is a giant pile of plastics floating in a patch, but it’s mostly made of microplastics, it’s like a soup.”

Great Pacific Garbage Patch

Sadly, we’re all too familiar with images of whales, dolphins, seabirds, and turtles in distress but the hidden element here is that microplastics are being eaten by animals that are equally as important but aren’t perhaps given as much attention. “Things like shrimp or oysters, or little crabs on the sea floor, they’re all eating these microplastics and they’re being affected by them and that’s a problem because we need these animals to recycle nutrients, and to be the base of food chain. The plastic problem in the ocean is enormous, but half of the problem is invisible because of microplastics.”

With a PhD on the Effect of Microplastic on Marine Muscles, Dr Trestrail discovered that when a muscle eats microplastics, it produces up to 50 per cent fewer digestive enzymes and that can have an effect on how much energy the muscle is getting from the food it eats, which impacts energy, growth rates and offspring rates. 

“Furthermore, I found having a belly full of microplastics would cause cellular stress. So, these animals were still alive but markers inside their cells were telling me that they were experiencing damage on a cellular level. There are these invisible toxic effects of microplastics. And that’s just one marine species,” explains Dr Trestrail.

The importance of our ocean

Thanks to micro algae and cyanobacteria photosynthesizing, scientists estimate  50-80 per cent of the oxygen production on Earth comes from the ocean. And while it’s not wholly responsible for the air humans breathe, most of the oxygen produced by the ocean is directly consumed by the microbes and animals that live within it, or as plant and animal products fall to the seafloor. It’s important. When the ocean cycles nutrients throughout the planet, and it’s a food source for so many people, these are all incredible eco system services we can’t afford to take for granted. 

“If you don’t want to protect the ocean for recreation purposes or you don’t appreciate the biodiversity and the beauty of the ocean, you should at least be thinking about the services the ocean offers us. Nutrients, a food source, and oxygen. Those are things every human needs. Without the ocean, everything collapses because the ocean and the land is so intimately linked. The consumer choices we make on land, have an effect on the ocean,” states Dr Trestrail.

Certainly, the ocean is under a lot of stress with climate change, and any effort we make to reduce the plastic pollution burden will provide breathing space for the sea, and also time for scientists to come up with a solution. 

“I really believe each one of us has the power to make this problem a little bit better. The plastic pollution problem is at the scale that it is because of millions of consumer choices that we make every day. If we got into the problem through consumer choices, we can start to find a way out of the problem through consumer choices,” Dr. Trestrail explains. 

“Every time you consume consciously and you’re aware of what you’re buying and trying where you can to make a choice away from plastic, that’s one less piece of plastic waste you put out into the world. It’s one less piece of plastic that can potentially float away into the ocean and fragment into thousands of microplastics.”

To be part of the solution, book your seat at the Volvo Ocean Lovers Festival Ocean Plastic Action Forum, and hear industry leaders, innovators, scientists, government and community leaders discuss how to ‘turn the tide’ on plastic in our ocean.

The Volvo Ocean Lover’s Festival

Tapping into Australians love of the ocean lifestyle this festival of ideas, art and music is the largest dedicated ocean science and cultural celebration in Australia. On a mission to share hope, solutions and action for the ocean, The Volvo Ocean Lovers Festival 2023 will use the power of entertainment, art, and science to connect people and engage them in behaviour that positively impacts our ocean. This accessible and interactive festival is open to all-ages over five filled days at Sydney’s iconic Bondi Beach from March 15-19, 2023.  As well as showcasing interactive experiences, captivating talks, and some of the latest innovation and technology saving our seas, the festival aims to promotes indigenous coastal care and provide a platform to ocean champions, marine scientists, government initiatives and community groups. 

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