Marine Debris
Silke from the Two Hands Project
Dr. Kelli Anderson
Marine debris has become a serious problem for oceans on a global scale. I even attended a marine conservation meeting earlier this year (2013) where one of the guest speakers, a well known marine debris researcher, was asked ‘just how serious’ the issues of marine debris is. She promptly stated that marine debris could end up being worse for the ocean than climate change... Say what?!?! I was quite shocked by the statement at the time, but the more I learn about marine debris, the more I've come to realise that her impromptu statement may not be far from the truth. Let’s have a look at what we know so far...
First and foremost, marine debris of anthropogenic origin can be pretty much anything that has been discarded, and can be made from a variety of materials. Plastics (made from fossil fuels), wood, metal, glass and other synthetic materials are becoming more and more common. Items can be of terrestrial origin, such as cigarette butts that are washed down curb side gutters, or can be accidentally released directly into the ocean from boats or jetties. Items such as nets may have been manufactured for marine use, but may have been abandoned or broken free from their moorings. The potential biological/ecological impact may vary depending on the type of debris. However, the types of debris that I feel are the most concerning are those that are persistent in the environment, can be consumed or may entangle marine life.
Marine debris has become a serious problem for oceans on a global scale. I even attended a marine conservation meeting earlier this year (2013) where one of the guest speakers, a well known marine debris researcher, was asked ‘just how serious’ the issues of marine debris is. She promptly stated that marine debris could end up being worse for the ocean than climate change... Say what?!?! I was quite shocked by the statement at the time, but the more I learn about marine debris, the more I've come to realise that her impromptu statement may not be far from the truth. Let’s have a look at what we know so far...
First and foremost, marine debris of anthropogenic origin can be pretty much anything that has been discarded, and can be made from a variety of materials. Plastics (made from fossil fuels), wood, metal, glass and other synthetic materials are becoming more and more common. Items can be of terrestrial origin, such as cigarette butts that are washed down curb side gutters, or can be accidentally released directly into the ocean from boats or jetties. Items such as nets may have been manufactured for marine use, but may have been abandoned or broken free from their moorings. The potential biological/ecological impact may vary depending on the type of debris. However, the types of debris that I feel are the most concerning are those that are persistent in the environment, can be consumed or may entangle marine life.
Consumption of Debris
It’s important to realise that conventional plastics are not readily biodegradable, and as such may persist in the environment for decades or even hundreds of years as they break into smaller and smaller pieces (microplastics). In Australia, an average of >4000 pieces of microplastics have been counted per square kilometre using surface water net tows. The nets used in that study had a mesh size of either 333 or 335 µm, and as such, it's possible that smaller nanoparticles were not accounted for and the total number of plastic particles is likely to be higher. As plastics enter the water, they may be targeted by many types of organisms, and some animals may prefer certain types of plastics. For example ‘benthic phase’ turtles living off the east coast of Australia tend to eat more soft, clear plastic relative to other types of plastic, possibly because these plastics resemble natural prey such as jelly fish. Ingestion of marine debris can cause a variety of sub-lethal impacts including reproductive problems and appetite suppression; however the consequence can be as severe as death. In late March 2012, a 10 m sperm whale was found dead on a beach near Castell de Ferro in SE Spain. A necropsy revealed that the whale had consumed marine debris including lengths of hose, two flower pots, burlap, rope, and a total of 59 plastic items. The whale was emaciated and in a state of starvation, and a large mass of plastic had ruptured a compartment of its stomach. More and more cases of debris ingestion and subsequent death are being documented. If you’re interested, you can check out a documentary that shows the impacts of marine debris on the albatross, http://www.midwayfilm.com.
Apart from the ill-effects caused by the physical presence of plastic pollution, substances that are used in their manufacture can leach into the environment. For example toxic heavy metals are commonly used as catalysers, stabilising additives, plasticisers and in pigments. Furthermore, contaminants found in the water column and sediments such as polychlorinated biphenyls (PCBs) and dioxins can sorb to plastics, then desorb and bioaccumulate (build up in the animal) once the plastic has been eaten by marine life. In fact, the concentration of these endocrine disrupting chemicals can be much higher on plastics than in the surrounding water. In the English Channel, 10 species of fish were surveyed (including cod, mackerel and whiting) and 36.5% of all fish had microplastics in their gastrointestinal tracts. This raises serious questions pertaining to the health of marine life, and may be of concern for those people who consume marine organisms as well.
Apart from the ill-effects caused by the physical presence of plastic pollution, substances that are used in their manufacture can leach into the environment. For example toxic heavy metals are commonly used as catalysers, stabilising additives, plasticisers and in pigments. Furthermore, contaminants found in the water column and sediments such as polychlorinated biphenyls (PCBs) and dioxins can sorb to plastics, then desorb and bioaccumulate (build up in the animal) once the plastic has been eaten by marine life. In fact, the concentration of these endocrine disrupting chemicals can be much higher on plastics than in the surrounding water. In the English Channel, 10 species of fish were surveyed (including cod, mackerel and whiting) and 36.5% of all fish had microplastics in their gastrointestinal tracts. This raises serious questions pertaining to the health of marine life, and may be of concern for those people who consume marine organisms as well.
Pictures from a dive with ecodivers at Manly Cove West, Sydney, Australia, and from the Two Hands Project (far right).
Entanglement
Entanglement is a persistent problem worldwide and can cause temporary injury or a slow and agonising death for marine life. Entanglement may result in amputation, infection, drowning, smothering or starvation by restricting mobility which prevents effective hunting/foraging. Health problems and stress may also negatively affect the animal’s reproductive success even if it doesn't cause the animal to die. For Stellar sea lions in Southeast Alaska and northern British Columbia, packing material was the most commonly found debris type that caused neck entanglement. Other type of entangling debris frequently encountered included rubber bands, nets, ropes and monofilaments used in fishing. Furthermore, a survey of just seven datasets collected along the central coast of California revealed that entanglements had been recorded for forty species including endangered leatherback turtles, sea otters and Guadalupe fur seals.
Ghost nets are discarded or lost fishing nets that travel on currents and tides while continually fishing. They are a significant problem, for example GhostNets Australia have removed in excess of 7500 ghost nets to date, and have found that 52% of caught wildlife are marine turtles (http://www.ghostnets.com.au/, site accessed December 2013). In the Puget Sound (Washington) it was estimated that a single ghost net could entangle 4368 Dungeness crabs in its lifetime. Putting an end to destructive and indiscriminate killing by ghost nets and other entangling items is essential for the health of our oceans, and will also have economic benefits.
Ghost nets are discarded or lost fishing nets that travel on currents and tides while continually fishing. They are a significant problem, for example GhostNets Australia have removed in excess of 7500 ghost nets to date, and have found that 52% of caught wildlife are marine turtles (http://www.ghostnets.com.au/, site accessed December 2013). In the Puget Sound (Washington) it was estimated that a single ghost net could entangle 4368 Dungeness crabs in its lifetime. Putting an end to destructive and indiscriminate killing by ghost nets and other entangling items is essential for the health of our oceans, and will also have economic benefits.
Above is some footage I took while diving at Southwest Rocks in NSW, Australia. It shows a grey nurse shark with some kind of rope (or may be packaging) wrapped around the back of its head and cutting into the gills.
Further Reading
GhostFishing.org
Ghost Nets Australia
Moore, M.J., van der Hoop, J.M. (2012) The painful side of trap and fixed net fisheries: chronic entanglement of large whales. Journal of Marine Biology, doi: 10.1155/2012/230653. View Article.
Nakashima, E., Isobe, A., Kako, S.i., Itai, T., Takahashi, S. (2012) Toxic metals derived from plastic litter on a beach. Interdisciplinary Studies on Environmental Chemistry - Environmental Pollution and Ecotoxicology, 321–328. View Article.
Raum-Suryan, K.L., Jemison, L.A., Pitcher, K.W. (2009) Entanglement of Steller sea lions (Eumetopias jubatus) in marine debris: identifying causes and finding solutions. Marine Pollution Bulletin. 58, 1487-1495. View Article.
Reisser, J., Shaw, J., Wilcox, C., Hardesty, B.D., Proietti, M., Thums, M., Pattiaratchi, C. (2013) Plastic pollution in waters around Australia: characteristics, concentrations, and pathways. PLoS One. 8, e80466. View Article.
Schuyler, Q., Hardesty, B.D., Wilcox, C., Townsend, K. (2012) To eat or not to eat? Debris selectivity by marine turtles. PLoS One 7, e40884. View Article.
de Stephanis, R., Giménez, J., Carpinelli, E., Gutierrez-Exposito, C., Cañadas, A. (2013) As main meal for sperm whales: Plastics debris. Marine Pollution Bulletin 69, 206-214. View Article.
Ghost Nets Australia
Moore, M.J., van der Hoop, J.M. (2012) The painful side of trap and fixed net fisheries: chronic entanglement of large whales. Journal of Marine Biology, doi: 10.1155/2012/230653. View Article.
Nakashima, E., Isobe, A., Kako, S.i., Itai, T., Takahashi, S. (2012) Toxic metals derived from plastic litter on a beach. Interdisciplinary Studies on Environmental Chemistry - Environmental Pollution and Ecotoxicology, 321–328. View Article.
Raum-Suryan, K.L., Jemison, L.A., Pitcher, K.W. (2009) Entanglement of Steller sea lions (Eumetopias jubatus) in marine debris: identifying causes and finding solutions. Marine Pollution Bulletin. 58, 1487-1495. View Article.
Reisser, J., Shaw, J., Wilcox, C., Hardesty, B.D., Proietti, M., Thums, M., Pattiaratchi, C. (2013) Plastic pollution in waters around Australia: characteristics, concentrations, and pathways. PLoS One. 8, e80466. View Article.
Schuyler, Q., Hardesty, B.D., Wilcox, C., Townsend, K. (2012) To eat or not to eat? Debris selectivity by marine turtles. PLoS One 7, e40884. View Article.
de Stephanis, R., Giménez, J., Carpinelli, E., Gutierrez-Exposito, C., Cañadas, A. (2013) As main meal for sperm whales: Plastics debris. Marine Pollution Bulletin 69, 206-214. View Article.