Over the last couple of weeks the amount of marine litter and pollution that is currently in our oceans, especially plastic waste, has featured heavily in the news and social media, not to mention on millions of TV screens thanks to the BBC series Blue Planet 2. It’s great that so many people are becoming aware of this growing problem, as there are so many things everyone can do in their every day lives to help cut down the amount of human trash and chemicals that ends up in our seas. So this week, our blog is a beginner’s guide to a few of the types of marine litter that are currently causing problems for ocean life everywhere on the planet and why they are so dangerous.
Pieces of trash and debris from man made objects represent a huge threat to all types of marine life, from small corals to large whales. Rubbish of all kinds, including plastic packaging, shopping bags, glass, old tyres and basically anything you can think of that goes into a landfill site can end up in the sea if it’s not properly disposed of. Human debris can harm wildlife in several ways; creatures may get stuck or wrapped in the trash and injured by it (entangled), the trash can get used as nesting material and cause harm to offspring and litter can also be mistaken for food and eaten by sea life, causing collections of plastic in marine mammal and turtle stomachs and guts.
Trying to combat the marine litter problem is proving challenging as it’s an issue that requires global co-operation to tackle. Once human debris is in the ocean, it can drift huge distances and cross many country boundaries. Debris can also collect together in certain marine areas due to ocean surface currents forcing litter into one place, forming regions in the middle of seas that have high concentrations of floating plastic. This month, the United Nations discused completely banning plastic waste entering the sea worldwide, in an effort to combat the problem. By stopping litter entering the ocean globally, and by encouraging member nations to clean up their coasts, it is hoped that real progress can be made to improve the state of our seas. With more than 200 member nations commiting to tackle the problem, it is hoped that a legally binding agreement can be reached on marine plastic in the coming years.
However, one of the few positive things about combating marine litter is that there are lots ways that everyone can make small changes in their lives to make real reductions in the plastic going into our environment. Here are just a few, try them and be part of the solution!
- Get a re-usable water bottle (or coffee mug if you drink more of that than water!), and use water fountains to refil it through the day rather than buy bottled water. If there isn’t a water dispenser at your place of work, talk to your bosses to get one installed for everyone to use.
- Get re-usable shopping bags to use instead of disposable ones from supermarkets.
- Say you don’t need a straw at bars and restuarants.
- If you don’t have any use for something you own anymore, try giving it to a charity shop, or making it into something new rather than throwing it to landfill. Coming up with creative ways to re-use things can be lots of fun, as well as saving you money and helping the environment.
- If you are out for a walk and see some litter blowing around, pick it up! Then you can dispose of it properly at the next opertunity. Ever piece of trash picked up and taken to a bin is one less piece of garbage that will end up in the sea.
It’s not only litter and plastics that make up the marine debris problem. Fishing gear can also be deadly for marine life, types include:
- ‘Ghost’ fishing nets, which are no longer attached to boats or checked by people, can entangle creatures they come into contact with. Nets and ropes wrapped around sea life frequently will injure or kills the individual.
- Abandoned fish or crab traps catch fish, crustaceans and invertebrates while they sit on the sea floor, and sometimes even larger types of sea creature get stuck in them trying to eat the creatures already trapped inside.
- Recreational fishing gear, such as mono-filament lines and hooks, can end up embedded in all sorts of marine creatures if they are cut and discarded carelessly.
Here on the Isle of May we live alongside the grey seals that breed here for two months every year, and the marks the seals bear from interacting with marine debris are often painfully obvious. Seal species typically develop entanglements around their necks, and if an individual cannot get free, the strands of rope bite into the flesh of a seal as it grows, making open fleshy wounds deep into the body. This can cut through the skin, blubber and muscle layers of the neck, becoming incredibly tight and ultimately killing the individual if the rope cannot be removed. Even when the rope is gone, seals frequently bear the deep scars from the problem for the rest of their lives. In 2017 we have seen a few ‘rope neck’ seals on the colony, however the worst man made item removed from a seal this year was from one of our study females, who had a fishing hook embedded in her hind flipper.
Unfortunately, intact man made debris is only the tip of the iceberg in terms of man made substances in our oceans. Plastic dose not properly degrade naturally, rather it eventually breaks into smaller and smaller pieces as it becomes brittle and cracks, ultimately becoming ‘microplastics’; tiny fragments of plastic that then persist in the seas or in the substrates of coastal environments. Microplastic pollution can also be generated when tiny pellets used in factories to make plastic items, called ‘nurdles’, are spilled into rivers or oceans. Microplastics are especially troublesome because they spread widely through marine environments and, unlike intact litter, they’re so small that cleaning them out of an area is very difficult. They are also readily eaten by a variety of marine life; either directly by small organisms such as zooplankton or indirectly by species feeding on zooplankton, which then transfers the microplastics up the food chain. Once eaten, microplastics tend to accumulate in organisms as plastic is so difficult to break down, and to date they have been found in the digestive systems of many marine species, including invertebrates, small fish, sharks and marine mammals. While scientists are still working to understand the impacts microplastic accumulation has on individual health and survival, many studies have already shown the negative affects they have on a variety of marine creatures, including:
- negative affects on reproductive physiology and breeding success
- significant changes in feeding behaviour
- reduced individual survival
The links between these negative impacts and microplastic exposure are still being uncovered, however it is thought that some of the problems associated with accumulating microplastics in the body may relate to the chemical pollutants held within the plastics. Several correlations between high microplastic ingestion rates and high concentrations of a variety of pollutants have been found marine species (e.g. these sea birds). However, correlations do not always equate to causality, and there are also studies showing no links between pollutant concentrations in plastic debris and pollutant burden in individuals eating the debris. One thing is sure however, microplastics in the marine environment are not going away anytime soon, and more work is needed to understand the problem and its consequences for marine organisms. The PHATS team that I am part of is working to uncover the physiological affects of persistent organic pollutants (or POPs, e.g. PCBs) on fat tissue from seals, and we need to understand how individuals get exposed to pollutants. Microplastic ingestion may represent an additional, significant route of exposure to these harmful chemicals in addition to those that are eaten when bound to the fatty tissues of prey speices, that have bioaccumulated up the food chain. Hopefully in the coming years, the mechanisms underlying POPs bound to microplastics, and their absorption into the tissues of marine organisms that ingest them, will become clearer.
Our research for the PHATS project on the Isle of May is going really well, and almost all of our study pups are now weaned from their mothers. Watching the pups go from skinny, fluffy newborns to massively fat, sleek weaners in just over two weeks is always a part of our work that fascinates me; it’s incredible that they can put on so much mass in such a short time frame. Soon the weaned pups will start leaving the island to go to sea for the first time, and their large blubber reserves will hopefully tide them over until they can learn how to fish by themselves.
As it’s getting into the late part of the season for the research team here on the island, we’ve also had lots of human comings and goings in the last week. We’ve had a film crew out from the BBC winter watch team, so hopefully footage of the Isle of May seals and some of the science done on the island will be coming to TV soon. Almost half of the research team has also returned back to the mainland, including the PHATS team leader Dr Kimberley Bennett, who has to get back to the University of Abertay to continue her lecturing duties. As the season continues, the team will probably drop to fewer than 4 people, who will stay out to finish the research work and then close up the island for the holiday season. We won’t be gone for long though, as the PHATS team are already planning our return in early January!