Marine pollution has been an environmental issue for millennia. During ancient time a worn plank, leather shoe or a decayed rope would wash ashore here and there. However, with technical development and population increase the type and longevity of litter has changed. Today, litter has become a common sight along beaches and in parts of the open ocean.
It is estimated that 6.4 million tons of litter enter the ocean every year. This equals to 8 million individual litter pieces per day. Due to improper disposal, approximately 80% of the litter is originated from land (e.g. through storm drains) while the rest of the 20% comes from cruise ships (e.g. solid waste thrown overboard). Cargo ships are also a source of pollution. Around 10,000 containers are lost at sea, spilling their content into the ocean (a 2.4m by 12.2 m container can hold up to 26,000kg of cargo).
Once debris enters the ocean, it can accumulate in the middle of the ocean gyres (North and South Atlantic, Indian Ocean, North and South Pacific), reach the seabed or wash up on the coast.
In addition to mid-ocean gyres, densely populated coastlines can also accumulate large amounts of debris, as well as isolated beaches (e.g. Niihau island, Hawaii) and deep sea areas (e.g. on Arctic Ocean floor at 2500m 7710 items/km2).
In the mid-ocean gyres plastic makes up 60-80% of the marine debris (e.g. food packaging, fishing gears, household appliances, etc). Following 24 expeditions over six years across all gyres, scientists were able to quantify that a minimum of 5.25 trillion plastic particles weighing nearly 270,000 tons are currently floating at sea.
(Model results for global count density in four size classes. Model prediction of global count density (pieces km−2; see colour bar) for each of four size classes (0.33–1.00 mm, 1.01–4.75 mm, 4.76–200 mm, and >200mm)
Items made of plastic are especially durable. As an example, the breakdown of a single plastic bag and a bottle can take up to 10-20 and 400 years, respectively. Subsequently, plastic debris can have a deleterious impact on the marine biota.
Approximately 267 species are effected by plastic pollution globally. Plastic ingestion is largely associated with foraging strategies and prey items. For example, planktivorous birds, sea turtles, seals and whales are able to readily consume plastic items leading to problems such as internal wounds, impaired feeding capacity and blockage. Entanglement is associated with discarded fishing gears (ghost gears) effecting large bodied marine animals like sharks, turtles, whales, dolphins and seals.
In order to tackle the problem of ocean pollution, coastal and river bank clean ups are frequently organised across the world. The aim of these events are to remove litter from all bodies of water (ocean, rivers, inland lakes and underwater sites), to gain information about marine debris (e.g. type, source) and most importantly, to raise public awareness about environmental pollution.
Based on data from 2012 and 2013 reports (SAS, MCS), the most frequently found items on the world’s beaches are: cigarette butts, plastic bags, beverage glasses and cans, straws and bottle caps.
This year’s Big Autumn Beach Clean was organised by Surfers Against Sewage across the UK, and with the help of approximately 3500 volunteers 20 tonnes of debris was removed. As part of the events, a clean-up was organised at Gabriel’s Wharf in central London. Interestingly, my personal experience here was that besides the above mentioned items such as cigarette butts and glasses, the most common type of debris were single-used tie-wraps/cable ties, which are used by many industries, for example on construction sites.
For more information about marine debris and coastal clean-ups please visit the following organisations:
Clean Up the World (UNEP, Global)
Project AWARE (Global)
Algalita Foundation (US)
International Coastal Cleanup - Ocean Conservancy (US)
Save Our Shores (US)
Surfrider Foundation (EU)
Marine Conservation Society (UK)
Surfers against sewage (UK)
Thames 21 (UK)
Figure and image source:
Bergmann and Klages (2012) Increase of litter at the Arctic deep-sea observatory HAUSGARTEN, Marine Pollution Bulletin, Volume 64, Issue 12, 2734–2741
Eriksen M, Lebreton LCM, Carson HS, Thiel M, Moore CJ, et al. (2014) Plastic Pollution in the World's Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea. PLoS ONE 9(12): e111913. doi:10.1371/journal.pone.0111913
Maximenko et al. (2012) Pathways of marine debris derived from trajectories of Lagrangian drifters, Marine Pollution Bulletin, Volume 65, Issues 1–3, 51–62