The Convention on Biological Diversity in 2012, counted 663 species affected by marine debris. Nearly 90% of the impacts were associated with plastic debris and about 15% of the species affected through entanglement and ingestion were found on the IUCN Red List as vulnerable, endangered or critically endangered species.
Ingestion of micro-plastics has been widely reported in a range of marine organisms including seabirds, fish, mussels and zooplankton. Micro-plastics have also been identified as an emerging threat to much larger organisms, like whales, that are exposed to micro-plastics ingestion as a result of their filter-feeding activity.
Plastic pollution is a threat to marine biodiversity, already at risk from overfishing, climate change and other forms of man-made disturbance. The threats to marine life are primarily mechanical due to ingestion of plastic debris and entanglement in packaging bands, synthetic ropes and lines, or drift nets. Entanglement in and ingestion of plastic debris can be fatal but it can also have a range of sub-lethal consequences such as compromising the ability to capture and digest food, sense hunger, escape from predators and reproduce, as well as decreasing body condition and compromising the ability to move for short and longer distances.
The harm to wildlife that can be caused by ingested plastics varies, depending on the digestive system of the animals, the amount and type of plastic ingested and the developmental stage of the animal. For example, certain birds such as albatrosses are more vulnerable because they generally do not regurgitate plastics. One of the major effects of plastic ingestion is reduced appetite. A stomach full of plastic that cannot be digested reduces the animals’ appetite leading them to starve to death. Other harmful effects are blockage of the digestive tract and internal injuries that are particularly evident in sea turtles that tend to eat plastic bags mistaking them for jellyfish.
The king mackerel is one of the most important resources caught by fishermen in north-eastern Brazil and it has been reported that the show evidence of a very high rate of plastic ingestion (62.5%). This raises concerns on the impacts that micro-plastics, not only on the animal itself but also on human health. The presence of resin pellets in the guts of fish harvested for human consumption represents a potential public health hazard.
Over recent years there have been many cases of dead whales and other animals whose stomachs were found to be full of plastic waste:
• In 1989, a stranded sperm whale in the Lavezzi Islands in the Tyrrhenian Sea died because of a stomach obstruction after accidentally ingesting plastic bags and 100 feet of plastic sheeting.
• In August 2000, a Bryde’s whale was stranded near Cairns, Australia. Its stomach was packed with six square meters of plastic rubbish including supermarket bags, food packages and fragments of trash bags.
• In July 2006, a 20-year old female Cuvier’s beaked whale died in Rarotonga, in the Cook Islands, after the ingestion of a single plastic shopping bag.
• In August 2008, a sperm whale that washed up in Point Reyes, California was found with 450 pounds of fishing net, rope and plastic bags in its stomach. In the same year, the California Marine Mammal Stranding Database, reported another stranded sperm whale whose stomach contents included an extensive amount of netting from discarded fishing gear.
• In October 2008, a 10-meter-long female Bryde’s whale stranded in the eastern state of Pahang, Malaysia. The necropsy showed that the animal had swallowed a black plastic bag, a rope and a bottle cap that had blocked her intestine.
• In April 2010 a gray whale stranded and died on a west Seattle beach. In its stomach researchers found, among other things, more than 20 plastics bags, surgical gloves and various plastic pieces.
• In May 2011, a juvenile female Gervais’ beaked whale was found on a beach in Puerto Rico with ten pounds of plastic in her stomach.
• In 2011, a young sperm whale was found floating dead of the Greek island of Mykonos. Its stomach was so distended that scientists believed the animal had swallowed a giant squid. However, when they dissected its four stomachs almost 100 plastic bags and other pieces of debris were found in there.
• In March 2013, a 10-meter-long whale was found dead in the coast of Andalucia, Spain. The whale has swallowed 59 different plastic items for an amount of almost 37 pounds and had died because of an intestinal blockage. The majority of the plastic was transparent sheeting used to build greenhouses in Almeria and Granada in order to grow tomatoes for the European market but plastics bags, ropes and other items were also found in the animal’s stomach.
• In July 2013, a 14-meter-long sperm whale was found dead on Tershelling, a northern island in the Netherlands. The necropsy revealed that the animal had 20 kilos of plastic inside her stomach, the majority of which was plastic covers used in greenhouses across the Netherlands to grow tomatoes.
• In 2015, a 15-meter whale was washed up in Tainan, south Taiwan. Its stomach was found to contain a huge amount of rubbish including plastic bags and fishing nets.
• In March 2015, a whale washed up and died on McNabs Island in Halifax Harbour. After the necropsy, researchers found plastic bags and plastic strapping in the animal’s stomach that had blocked the whale’s stomach making the animal unable to ingest any other sort of food.
• In December 2015, an 18ft orca was found dead on the beach in Plettenberg Bay, South Africa. Very little food was found in her stomach which was instead full of rubbish including several pieces of plastic, yoghurt pots, shoe soles and food wrappers, that had blocked the animal’s stomach leading the orca to starve to death.
• In January 2016, a total of 13 young sperm whales washed up on the beach near the town of Tonning in Schleswing-Holstein in Germany. Necropsies conducted on the dead sperm whales revealed that the cetaceans had an array of plastics in their stomachs. Among the rubbish that has been removed from the whales stomachs, researchers found a fishing net that was 13 meters long and 1.2 meters wide, a 70 cm plastic cover from the engine compartment of a car and the sharp-edged remains of a plastic bucket.
We are focussing here on the effect of plastics in the marine environment, but it is important to remember that plastics are fossil-fuel based, which means that there is a climate change impact in their manufacture, as well as that of oil spills, pipelines and wells impinging on indigenous lands and communities, and the drilling of new wells in the Arctic and other important wildlife habitats.