The ocean, a vast expanse covering over 70% of our planet, has historically been perceived as a limitless repository for waste. For centuries, societies have utilized its depths as a convenient disposal site. This practice, often driven by a lack of land-based alternatives or a misunderstanding of marine ecosystems, has led to significant environmental challenges. Understanding its nature and consequences is important for appreciating global efforts to protect marine environments.
Defining Ocean Dumping
Ocean dumping refers to the deliberate disposal of waste materials into the marine environment from vessels, aircraft, platforms, or other human-made structures at sea. This act is distinct from other forms of marine pollution, such as land-based runoff or accidental spills. While both contribute to ocean contamination, ocean dumping specifically denotes a planned discharge. It also excludes discharges that occur incidentally during normal vessel operation, like treated sewage or ballast water, or the placement of materials for purposes like enhancing fisheries.
Historically, regulation of ocean dumping were less strict, with many substances being routinely discharged without significant oversight. Over time, as understanding of marine ecosystems advanced, the scope of what constitutes harmful dumping has broadened. This includes not only direct disposal but also the abandonment of structures at sea, such as offshore oil and gas platforms at the end of their operational life, if not repurposed.
Commonly Dumped Materials
A wide range of materials have been, and in some cases continue to be, disposed of in the ocean. Dredged material, which consists of sediments removed from harbors, rivers, and navigation channels, represents a substantial portion, accounting for approximately 80% of all waste dumped into the ocean. This material can contain heavy metals like cadmium, mercury, and chromium, along with hydrocarbons, nutrients, and organochlorines from various land-based sources.
Industrial waste, historically including acids, alkaline waste, scrap metals, and byproducts from fish processing and coal ash, was legally dumped in significant quantities, with 17 million tons in the 1970s alone. Sewage sludge, a semi-solid byproduct of wastewater treatment, also used to be commonly dumped. This sludge can contain pathogens, heavy metals, and micropollutants.
Radioactive waste, often packaged in drums, was disposed of at over 50 sites in the Atlantic and Pacific Oceans, including low-level waste from research, medicine, and nuclear industries. Some instances involved the dumping of higher-level waste, such as disused nuclear submarines and reactors. Additionally, military armaments and chemical weapons have been deposited in various ocean locations.
Environmental Consequences
The disposal of waste in the ocean has significant consequences for marine ecosystems and human well-being. One impact is habitat destruction, where the accumulation of excess sediment or the release of toxins can degrade or eliminate marine environments. This includes effects on coastal areas, leading to erosion and salutation, and harming habitats like seagrass meadows, kelp beds, and coral reefs.
Marine life faces harm through toxicity and entanglement. Toxic substances such as heavy metals, DDT, mercury, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) can accumulate in marine organisms, causing health issues and impacting entire food chains through a process called biomagnification. Eutrophication, caused by excessive nutrient loads from waste, leads to algal blooms that deplete oxygen levels, creating “dead zones” where marine life cannot survive.
Entanglement in discarded fishing gear, plastics, and other debris can injure or kill species, including seabirds, turtles, dolphins, and whales. Ingestion of plastic debris blocks digestive tracts and leads to starvation. These impacts disrupt marine food webs.
Water quality degradation from ocean dumping can extend beyond immediate disposal sites, with currents spreading pollutants far and wide. This pollution can affect coastal communities by contaminating seafood, posing health risks, and damaging industries like fishing and tourism. The long-term effects of some dumped materials, such as radioactive waste, are still under study.
International and National Responses
Global efforts to address ocean dumping gained momentum in the early 1970s, leading to the adoption of international agreements. The Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972, commonly known as the London Convention, was one of the first global instruments to regulate deliberate disposal at sea. It established a framework by prohibiting the dumping of certain hazardous materials and requiring permits for others.
In 1996, the London Protocol was agreed upon to modernize and eventually replace the London Convention, adopting a more restrictive “reverse list” approach. Under this Protocol, all dumping is prohibited unless explicitly listed as permissible, and it also banned incineration at sea and the export of waste for dumping. Permitted materials under the Protocol include dredged material, fish wastes, vessels, inert geological material, and organic material of natural origin.
In the United States, the Marine Protection, Research, and Sanctuaries Act (MPRSA) of 1972, often referred to as the Ocean Dumping Act, regulates intentional ocean disposal within U.S. jurisdiction. The MPRSA prohibits the transportation of material from the U.S. for ocean dumping and requires permits for any allowed dumping, with a standard that dumping must not “unreasonably degrade or endanger” human health or the marine environment. Since 1991, the MPRSA has banned the dumping of industrial wastes and sewage sludge, and it also prohibits high-level radioactive wastes and medical wastes.