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Global impact of marine debris
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Global impact of marine debris

Marine debris is a global issue, impacting a wide range of marine species and ecosystems. Watch Dr. Kathy Townsend explain more.
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In this section, you’ll learn about the global impacts of marine debris. Hi, my name is Dr. Kathy Townsend, and I’m a specialist in the impacts of marine debris on sea turtles from the University of the Sunshine Coast, here in Australia. I’m reporting to you here from Minjerribah North Stradbroke Island in Brisbane, and I want to tell you a story about plastic. It’s a good news bad news story. As a society, we’ve created this light, durable material that’s inexpensive, and has provided many social and economic benefits, including things such as sterile items for medical use. However, the success is a double edged sword. We have doubled plastic production in less than 20 years to over 400 million tonnes per year.
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Disappointingly, only 14% of this consumer waste is actually recycled with 33%, escaping rubbish collection and is lost to the environment. This equates to four to 12 million tonnes of plastic entering the oceans annually. And it’s been estimated that there’s currently 150 billion tonnes of plastic in the world’s ocean. But where does all this plastic go? And why are we not just knee deep in plastic along every single shoreline? Well, the plastic is swept out to the oceans and in out to sea in the ocean currents. And there it collects an ocean gyres many of you may have heard of the North Pacific garbage patch off the coast of the Americas.
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However, many of you would be unaware that there are garbage patch is pretty much every ocean in the world. But where does this plastic end up? Of course, much of it washes up on shore and it can be collected, however much of it ends up inside or round marine animals. Over 690 marine species have been recorded interacting with marine plastic debris globally. And this includes things like sea turtles, fish, whales, seabirds, and even invertebrates such as krill, and bivalves like mussels. I want to tell you about how I started research on the impact of marine debris on sea turtles. It started over 15 years ago, and I was fortunate to live in work on an island based Marine Research Station.
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During my time there, we took care of sick and injured sea turtles. There were over 200 turtles reported stranded per year in the region with many dying from no obvious external wounds. And this made me ask why? Well, I talked to other cares, and they said that they were observing sea turtles defecating plastic during rehabilitation. Now this is where my internal scientist turned on. And I looked up the only data available at the time from the Queensland marine animal stranding database, which recorded that at the time, only about 2% of the stranded turtles seem to be affected by marine debris.
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But much higher levels were being recorded globally, with some locations of South America showing 100% of sea turtles having ingested plastics and other types of debris. So my very first question was, is marine debris ingestion Actually a problem for Australia sea turtles? So to do this, I started to collect recently dead sea turtles ones that were either washed up stranded or had died soon after having been taken into care. My team and I perform necropsies which are like autopsies. To try to understand what possibly killed them. We found our answer very quickly. Over 35% of the sea turtles we necropsied had swallowed plastic, another 10% of the deaths were found to be caused by entanglement in marine debris. Wow.
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Now that we knew it was a problem, it led to more questions. Firstly, we asked, was it only one species of turtle that was impacted? Or was it every species that we had access to? Initially, we thought it was only green turtles that were being affected. However, we found plastic in every species. This included loggerheads hawksbills, greens, and flat bags. And speaking of flatbacks, ours was the first lab to record plastic in the stomach of a flatback turtle. Since we started that study, all seven species of the world’s turtles have now been recorded having consumed plastic and other types of debris. The next question we asked was just age make a difference.
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And we found that plastic in all life stages from the little tiny post hatchlings all the way through to the sexually mature adults. However, the greatest impact was on open ocean juveniles, which were equated to about 55% of them, and the coastal immature turtles at 27%. While fully sexually mature adults are much less likely to be impacted by eating plastics less than 5%. This possibly is due to their increased diameter of their gastrointestinal system as they grew, making it less likely for the plastics become stuck. We now knew we had a problem on our hands, over a third of stranded turtles from all species and all life stages were being impacted by marine debris here in Australia.
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But this left us was a conundrum though, as the chances that we could completely remove plastic from our society is pretty much impossible. So instead, we asked the question, are sea turtles selecting for certain types of debris, because if they’re targeting certain types of debris, then maybe we can do something about it. So then what we did is we compared what we could find in the environment, like on the beaches behind me here. With what we’re removing from the guts of both the sea turtles and seabirds, we’d started studying those at this stage as well.
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And what we found was, is that sea turtles definitely did target certain types of debris, and sea turtles targeted soft plastics such as plastic bags and balloons, while seabirds also targeted balloons, but they had a preference for hard plastics. But why are they eating it if it’s so bad for them? After all, eating plastic can cause gut perforation, dietary dilution, gut impaction and it has potential toxic effects as well? Well, it turns out that both sea turtles and seabirds are highly visual predators, and the plastics and balloons look like natural prey items like jellyfish and squid. So where are all the sea turtles getting listed marine debris from? After all, they swim huge distances across ocean basins?
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Well, our work found that they interact with debris within 250 kilometres of where they were first found stranded. So for Australia, that means it was plastic found locally. However, not all the debris originates from local sources, with plastic debris washing up on some of the most isolated beaches in the world, such as the Antarctic and the Galapagos Islands. With this in mind, we asked the question, Where are the areas of the world where sea turtles are at highest risk of eating plastic? To answer this question, we overlaid the map of where marine debris is distributed throughout the oceans with where we know sea turtle populations occur.
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And by combining these two data sets, that resulted in a global risk that that highlighted locations that have a high probability of sea turtles consuming plastics. Our lab is now turning its attention to microplastics and the biological and chemical impacts that may occur on sea turtle health. We know that microplastics are ubiquitous throughout the globe, they can be found on the very highest mountain down to the ferry deepest trenches in the oceans. The problem is, however, that every large piece of plastic slowly breaks down into smaller and smaller pieces, making it available to greater numbers of animals.
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Microplastics can be fed on directly by animals, or alternatively, they can be exposed to it by prey items containing the plastics within their own guts, causing secondary exposure. This means that species that feed on the smallest prey of the ocean plankton - may actually be exposed to microplastic in a type of plastic soup. This is horrible news. Well, what can we do about it? Well, the research that was produced by my colleagues and myself have resulted in legislative changes across Australia and the world, including mass helium balloon release bans, plastic bag bans, we now have a container deposit scheme in Australia, and single use cutlery and straw bans.
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It’s through a combination of research industry and people power that these changes have come about. The exciting thing about marine debris is that small actions taken by individuals can actually make a really big difference. So you can help by following the seven R’s of recycling. Recycle refuse Reduce, Reuse, repair, regift, and recover. And together, we can help to protect life below water.

Marine debris is global issue, impacting a wide range of marine animals and coastal ecosystems. In this section, you will hear about how a local study of sea turtles in Australia, has helped to create change around the way society uses single use plastics.

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Life Below Water: Conservation, Current Issues, Possible Solutions

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