Marine Debris Surveys
An introduction to marine debris
Current estimates are that over six million tones of rubbish reach the world’s oceans each year and that there is more than one hundred million tonnes of plastic in the world’s oceans. This means that beach rubbish such as hard plastic pieces, bottle tops, balloons, straws, food wrappers and polystyrene can now be found on every beach in the world, including our own local beaches. Plastic rubbish has even reached pristine wilderness like Antarctica, with up to 40,000 pieces per square kilometre of ocean being recorded during 2012. About 20% of plastic debris comes from ocean sources like derelict fishing gear, while about 80% comes from land where it enters the ocean from our waterways. A large segment of what ends up as marine debris is single use disposable consumer items like plastic bags, drink bottles and lids, food wrappers, straws, plastic cutlery and lollipop sticks. These items, if not properly disposed of, can fall to the ground, blow or wash into stormwater drains and flow into the ocean. The plastics industry also contributes to the marine debris problem, as pre-production plastic pellets lost during industrial processing can now also be found in the sand on beaches throughout the world. These pellets are also called “nurdles”.
Why worry about plastic debris in the ocean?
Very little plastic packaging is recycled, even when you put it in the recycling bin. In Australia for the year ending 30 June 2011, approximately 38% of all plastic packaging was recycled – the rest goes to landfill and there are only limited landfill sites available.
Plastic is not biodegradable and requires exposure to sunlight to break down (referred to as photodegradation). It can take several hundred years to break down. During this time it simply breaks into smaller and smaller pieces and travels over vast distances in the ocean as it is lightweight and durable. Some of the pieces can be so small (less than 5mm) that they cannot easily be seen – these very small pieces are called microplastic pieces.
Plastic is responsible for the deaths of over 1 million marine animals every year. Marine animals including fish, seabirds, turtles, seals and whales mistake plastic pieces for food or get entangled in them, resulting in injury or death.
In some parts of the world’s oceans, plastic now outnumbers surface zoo plankton by 6 to 1.
Plastic debris releases chemical additives into the ocean. It also absorbs pollutants and pesticides up to one million times the concentration of the surrounding seawater. These pollutants bio-accumulate in the tissues of marine animals, bio-magnify up the food chain and find their way into the foods we eat.
FACTS ABOUT PLASTIC BAGS
What happens once plastic enters the ocean?
It takes longer for the sun to break apart a piece of plastic in the ocean than a piece of plastic on land. This is because the ocean water cools the plastic piece, prevents heat build up and limits ultraviolet light exposure.
Plastics are carried by currents which can concentrate the plastic in certain areas of the ocean and prevent it from washing ashore.
Circulating currents in the ocean caused by stable weather patterns are called gyres. Plastic that ends up in a gyre tends to circulate there for a number of years, creating what resembles a “plastic soup”. Because a gyre covers such a huge area of ocean and the plastic pieces within the gyre are unevenly spread, it is virtually impossible to remove all the plastic pieces from the gyre.
Not all plastic floats on the surface of the ocean – about half accumulates on the bottom of the ocean floor where there is no access to sunlight. These pieces are not visible from the surface or the beach, but they are absorbed by bottom dwelling organisms.
When plastic pieces wash ashore, they can mix with grains of sand on the beach and change the structure and temperature of beach sand.
Have you heard of “nurdles”?
They are tiny pellets of plastic that are melted down to make almost every plastic product on earth. Nurdles are made in huge numbers and are often discharged into the environment during the manufacture of plastics or transport of the pellets. They wash into stormwater systems and into the ocean, where they are mistaken for food by fish, birds and marine life. They also act as sponges that concentrate pollutants. It is impossible to estimate how many nurdles are in the ocean. Unfortunately nurdles are present on our very own local beaches as they have been located during our monthly beach rubbish surveys. If you look very closely at the high tide line along the beach you will find them.
What can we do to prevent the plastic problem from getting worse?
Although plastic products benefit our lives in the medical industry, the use of safety equipment and other technologies, it is important that we reduce the flood of plastic waste into the environment. Here are some simple ways to reduce how much plastic you use:
Some results of our monthly marine debris surveys
Further reading and websites:
Books about marine debris – just a sample