Plastic waste in the ocean refers to the accumulation of plastic products in marine environments, leading to issues for wildlife, habitats, and human populations. Millions of tons of plastic debris enter the world’s oceans annually, with estimates suggesting between 75 and 199 million metric tons are present. This global problem has intensified significantly since the widespread introduction of plastics in the early 20th century, with annual production skyrocketing from 2 million tons in 1950 to 460 million metric tons by 2019.
Where Ocean Plastic Comes From
Plastic waste enters the ocean from both land-based and sea-based sources. Land-based sources account for approximately 80% of marine debris. This includes mismanaged waste, litter from construction, households, and packaging, as well as industrial discharge and urban runoff, carrying trash into waterways and the ocean. Inadequate waste management infrastructure, particularly in middle-income countries where plastic use is increasing, allows plastic to escape into the environment.
Sea-based sources contribute the remaining 20% of ocean plastic. A prominent example is abandoned, lost, or discarded fishing gear, often referred to as “ghost gear,” comprising 46% to 70% of macroplastic marine debris by weight. Including nets, lines, ropes, and traps, an estimated 640,000 tons enter the oceans each year. Other sea-based sources include shipping operations, aquaculture, and offshore oil and gas activities.
How Plastic Accumulates in the Ocean
Once plastic waste enters the marine environment, it travels and concentrates. Ocean currents play a major role, carrying floating debris into large circulating systems called gyres. There are five main ocean gyres, such as the Great Pacific Garbage Patch, spanning 1.6 million square kilometers and containing trillions of plastic pieces. Coastal areas and river estuaries also act as collection points, with plastic concentrations significantly higher than in the open ocean.
Plastic debris, especially buoyant types, can undergo biofouling, as microorganisms and aquatic life colonize its surface, increasing its density and causing it to sink. Over time, larger plastic items degrade into smaller fragments from sunlight, wind, waves, and friction. This fragmentation process leads to the formation of microplastics, particles less than 5 millimeters in size, and even smaller nanoplastics, less than 100 nanometers. These tiny particles spread throughout the water column and can accumulate in seabed sediments, forming “hot spots” with millions of pieces per square meter.
Environmental and Health Consequences
Ocean plastic pollution inflicts harm on marine life and ecosystems. Marine animals face threats from entanglement in larger plastic debris like fishing nets, causing injuries, suffocation, or drowning. Ingestion of plastic is another severe problem, as animals often mistake plastic fragments for food, leading to internal injuries, blockages in the digestive tract, and a false sense of fullness resulting in starvation or malnutrition. Toxins, such as persistent organic pollutants, can adsorb onto plastic surfaces, and when ingested, these chemicals can transfer into the animals’ tissues, causing reproductive issues or affecting immune function.
Plastic pollution disrupts marine ecosystems by damaging habitats like coral reefs and seagrass beds. Accumulations of plastic on coral reefs can block sunlight, hindering photosynthesis and harming polyps. Similarly, plastic can smother seagrass meadows, serving as nurseries and feeding grounds for many species, reducing plant cover and altering the ecosystem’s structure. The presence of microplastics in sediments can also impact seagrass growth and lead to reduced decomposition rates of organic matter, affecting nutrient cycling.
Microplastics can enter the human food chain through consumption of seafood, salt, and drinking water. Studies have detected microplastics in various seafood, with some estimates suggesting that a top European shellfish consumer might ingest approximately 11,000 plastic particles annually. Research also indicates that microplastics are present in table salt and drinking water, and inhalation is another potential exposure route. While research into human health implications is ongoing, concerns exist regarding the physical and chemical toxicity of these particles, as plastics contain chemical additives that can leach out or accumulate environmental pollutants.
Addressing Ocean Plastic Pollution
Addressing ocean plastic pollution requires a multi-faceted approach, including prevention, cleanup, and policy initiatives. Reducing the use of single-use plastics, such as bags, bottles, and food containers, is a key prevention method, and many places globally have successfully implemented bans or taxes on these items. Improving waste management and recycling infrastructure is also important, particularly in regions where waste collection and disposal systems are lacking. This includes investing in modern facilities for collection, sorting, and recycling, and enforcing regulations against illegal dumping.
Cleanup efforts remove existing plastic from marine environments. Technologies like The Ocean Cleanup’s barrier systems are deployed in oceanic gyres to collect much floating plastic, to remove much debris from areas like the Great Pacific Garbage Patch. River cleanup technologies, such as The Interceptor, are also being deployed to prevent plastic from reaching the ocean by capturing it in rivers. Coastal and river cleanups, often involving volunteers, contribute to direct removal and raise public awareness.
International cooperation and policy development are also important. The United Nations Environment Assembly adopted a resolution in March 2022 to develop a legally binding agreement on plastic pollution by 2024, addressing plastic’s entire lifecycle from production to disposal. This global treaty aims to establish common standards, including bans on harmful plastic products and chemicals, and to facilitate financial and technical support for effective implementation worldwide. Public awareness campaigns and individual actions, such as proper recycling and reducing personal plastic consumption, are also important in fostering commitment to protecting marine environments.