Marine Debris
Primary reference(s)
UN Environment, no date. Marine Litter. Accessed 14 October 2020.
NOAA, no date. National Ocean Service. What are microplastics? National Oceanic and Atmospheric Administration (NOAA). Accessed 14 October 2020.
Additional scientific description
Marine debris originates from many sources and causes a wide spectrum of environmental, economic, safety, health and cultural impacts. The very slow rate of degradation of most marine litter items, mainly plastics, together with the ever growing quantity of debris disposed of, is leading to a gradual increase in marine litter found at sea and on the shores (United Nations, 2017).
Marine debris is present in all marine habitats, from densely populated regions to remote areas far from human activities, from beaches and shallow waters to deep ocean trenches (Wang et al., 2016). The average density of marine debris is estimated to vary from 13,000 to 18,000 pieces per square kilometre (UNEP, 2017). However, data on plastic accumulation in the North Atlantic and Caribbean from 1986 to 2008 showed that the highest concentrations (more than 200,000 pieces per square kilometre) occurred in the convergence zones between two or more ocean currents (Law et al., 2010). Computer model simulations, based on data from about 12,000 satellite-tracked floats deployed since the early 1990s as part of the Global Ocean Drifter Program, confirm that debris will be transported by ocean currents and will tend to accumulate in a limited number of subtropical convergence zones or gyres (Wang et al., 2016).
Plastics are by far the most prevalent debris item recorded, contributing an estimated 60% to 80% of all marine debris. Plastic debris continues to accumulate in the marine environment. The density of microplastics within the North Pacific Central Gyre has increased by two orders of magnitude in the past four decades. Marine debris commonly stems from shoreline and recreational activities, commercial shipping and fishing, and dumping at sea. The majority of marine debris (approximately 80%) entering the sea is considered to originate from land-based sources.
Nanoparticles are a form of marine debris, the significance of which is only now emerging. They are minuscule particles with dimensions of 1 to 100 nanometres (a nanometre is one millionth of a millimetre). A large proportion of the nanoparticles found in the ocean are of natural origin. It is the anthropogenic nanoparticles that are of concern. Those originate from two sources: from nanoparticles deliberately created for use in various industrial processes and cosmetics and from the breakdown of plastics in marine debris, fragments of artificial fabrics discharged in urban wastewater, and leaching from land-based waste sites. Recent research has highlighted the potential environmental impacts of plastic nanoparticles: they appear to reduce primary production and uptake of food by zooplankton and filter-feeders (United Nations, 2017).
Metrics and numeric limits
Not available.
Key relevant UN convention / multilateral treaty
Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (IMO, 2019).
Examples of drivers, outcomes and risk management
Marine debris takes many forms, including derelict fishing gear and vessels, abandoned recreational equipment, and discarded consumer plastics, metals, rubber, paper, and textiles.
Marine debris can result in economic losses, habitat damage (including to fragile coral reefs), hazards to shipping resulting in costly vessel damage and loss, transport of potentially invasive species that may have devastating impacts on ecosystems, and wildlife injury, illness, and death (NOAA, no date).
Marine debris can affect a wide range of marine life, from small microorganisms to humpback whales. Animals may inadvertently eat debris or become entangled in it. For instance, plastic bags are a common threat to sea turtles, which often mistake them for jellyfish; a common food item. Marine debris also affects other species, such as the endangered Hawaiian monk seal, where one death caused by marine debris is a huge loss (NOAA, no date).
References
IMO, 2019. Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter. International Maritime Organization (IMO). Accessed 28 April 2021.
Law, K.L., S. Moret-Ferguson, N.A. Maximenko, G. Proskurowski, E.A. Peacock, J. Hafner and C.M. Reddy, 2010. Plastic accumulation in the North Atlantic subtropical gyre. Science, 329:1185-1118. 10.1126/science.1192321
NOAA, no date. Marine Debris. Office for Coastal Management. National Oceanic and Atmospheric Administration (NOAA). Accessed 14 October 2020.
UNEP, 2017. UN Environment contribution to Concept Papers for Partnership Dialogues of The Ocean Conference. United Nations Environment Programme (UNEP). Accessed 28 February 2021.
United Nations, 2017. The First Global Integrated Marine Assessment: World Ocean Assessment I. Cambridge University Press. Accessed 14 October 2020.
Wang, J., K. Kiho, D. Ofiara, Y. Zhao, A. Bera, R. Lohmann and M.C. Baker, 2016. First Global Integrated Marine Assessment: World Ocean Assessment I. Accessed 28 February 2021.