80% of plastic found in the sea - comes from the land. So, how does the plastic get there? Plastic is light and can enter our water sources in many ways. Discarded plastic can come from people mindlessly dropping their litter in the street, from landfill sites or from products we use to exfoliate, whiten our teeth or clean our clothes. Our towns and cities are designed to drain water from our houses and streets to prevent flooding. These extensive waterways transport plastic waste through drainage systems ending up in canals, river and eventually the sea. Across the globe, 8 million tonnes of plastic ends up in our oceans every year and of this, 50% has been produced for single use.
Recent research shows that 50% of the ocean’s plastic originates from just 5 countries - China, Indonesia, Philippines, Vietnam and Sri Lanka. Many countries around the world transport waste to these countries to recycle some of the “more valuable” plastics such as PET, the plastic that water bottles are made from. The unwanted plastic is dumped in poorly managed landfill sites, meaning much of the plastic is at risk of ending up in the sea.
A Hidden Problem
Some 250 million people earn their living from fishing and up to 70% of humans rely on fish as their primary source of protein. In the marine environment, plastic is capable of absorbing harmful toxins from the water and concentrating the toxic levels of chemicals such as PCBs, PAHs, and DDT up the food chain leading ultimately to us. It is not just the plastic we can see which is the danger to us! Plastic is broken down by wave action and UV light into small microplastics. Microplastics are eaten by filter feeding plankton which is near the bottom of the food chain affecting the animals depending on that food chain. Long exposure to these toxins has been linked to serious health conditions such as cancer, diabetes, low sperm count, altered immune systems and developmental problems in children.
Plastic affects marine animals by physically tangling them leading to injury, distress, ingestion, and drowning. 1 in 3 species of marine mammals has been found entangled in marine litter. Scientists have found that over 650 species have been known to have adversely interacted with plastic, and 1 in 3 marine mammal species have been found entangled in marine litter.
80% of marine litter is plastic.
One plastic bag can kill an animal which can survive eating a toxic Portuguese-man-of-war. It is estimated that there are now 46,000 pieces of plastic per square kilometre of the world’s oceans, with 5 trillion pieces of plastic floating on the oceans worldwide.
Estimates by scientists repeatedly show that the concentrations of plastic are increasing with a recent paper stating an average density of 9.8kg/km2. This plastic can be mistaken for food. Approximately 500 species of marine animal have been known to have either eat or become entangled in plastic. This includes 1 in 3 seabirds many of whom feed their chicks plastic after mistaking them for food. Whales, dolphins, seals, turtles, and fish have also been found containing ingested plastic.
Waste of Life
Turtles are known to be affected by plastic litter in range of ways. Turtles use sight and scent to select their prey and often mistake plastic for prey as marine plastic can look and smell like natural prey. Research has shown that plastic found in the digestive tracts of turtles differ between species depending on what they feed on. Scientists estimate that there is between 1000-3000 tonnes of floating plastic in the Mediterranean at any one time. If a turtle accidentally ingests plastic, it not only makes the animal feel falsely full resulting in starvation but can leave internal injuries leading to infection. The presence of plastic in the digestive tract can also affect the animal’s buoyancy. Turtles entangled in floating plastic are subjected to increased drag when swimming, causing starvation or drowning.
Litter on the beach can also be a hazard to turtles. Female turtles come to the beach to lay their eggs and they're emerging hatchlings become entangled in plastic and other waste on their journey to the edge of the sea. The discarded plastic can even effect turtles before they hatch from their eggs as the sex of turtles is determined by the temperature of the nest during development. The build-up of litter on the sand could affect the temperature of the nest leading to an unnatural sex ratio of the hatchlings.
Plastic - Whales and Dolphins
There are two types of whale – baleen and toothed whales. Baleen whales have 2 ‘comblike’ keratin plates in their mouths that they use to filter their prey through, whereas toothed whales such as dolphins and porpoises have teeth. These differences have an effect on plastic ingestion. Baleen whales take in large amounts of water each time they open their mouths to feed (up to 75,000 litres in blue whales!), resulting in the high potential of plastic consumed.
When ingested, microplastics found in the water or in the plankton that they are feeding on can lead to long term health issues. Larger plastics, which can block their digestive tracts and lead to starvation, are also a danger, especially as larger pieces of plastic are unable to filter out of the keratin plates once sucked in. Globally there are many recordings of whale deaths, including in Cairns in 2009 a Bryde's whale was found dying of starvation on the shore with 6mÑ of plastic found inside it.
Toothed whales and Dolphins are more at risk of ingesting large amounts of plastic, mainly due to mistaking the plastic for their food, although microplastics are also a threat. In Schleswig-Holstein, Germany in 2016, 13 stranded sperm whales all had the presence of plastic in them, ranging from 13 metre long fishing nets to a 70 cm long plastic component from a car.
99% of seabirds will have consumed plastic by 2050
A recent study showed that 90% of seabirds have consumed plastic, with models predicting this to rise to 99% by 2050. Seabirds are highly susceptible to ingestion of plastic as they mistake floating debris for food. Even worse, many seabirds regurgitate the plastic matter directly into the mouths of their chicks. Plastics reported being ingested range from large plastic items to nurdles, that is used as a feedstock material in the plastics industry, plastic bags, and fishing lines.
Plastic can become lodged in the digestive passages of birds leading to a false sense of fullness and starvation, or sharp pieces can damage the gut resulting in infection or death. Over 16% (56 species) of seabirds have been recorded to become snared in plastic, either after mistaking it for food or accidentally swimming into it. Entanglement can lead to injury, infection or drowning of the seabird. Discarded fishing gear and six-pack can holders are the most common causes of entanglement. Some seabirds also become tangled in plastic debris after using it to build their nests.
Hazardous chemicals such as DE and PCBs from the surrounding seawater concentrate on the surface of plastic particles adding to toxins already present in the plastic from their production process. These build up in the body tissues and have serious detrimental health effects.
Around 70% of plastic sinks, but there is currently no global estimate into how much plastic is present in the deep sea.
Most seabed surveys have focussed on the shallower continental shelves, however, roughly half the earth’s surface is deeper seabed where fewer studies have been carried out as this environment is challenging and expensive to explore. What we do know, is that plastic has been found on the seabed in every sea and ocean, even at depths exceeding 7000 metres! Deep sea plastic is likely to have travelled a long distance on the surface of the sea before being fouled by marine organisms and sinking. It will then be swept in ocean currents and affected by the topography of the area before settling on the seabed with other litter such as fishing gear and tyres. A recent study found microplastics and fibres in the deep sea sediment. Their presence in every sediment sample taken suggests that microplastic is abundant in the deep sea.