6.0 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Marine pollution | 4/7 | https://en.wikipedia.org/wiki/Marine_pollution | reference | science, encyclopedia | 2026-05-05T07:36:11.497461+00:00 | kb-cron |
Apart from plastics, there are particular problems with other toxic pollutants that either do not break down or only very slowly in the marine environment. Examples of persistent toxicants are PCBs, DDT, TBT, pesticides, furans, dioxins, phenols, radioactive waste, and PFAS. Heavy metals are metallic chemical elements that have a relatively high density and are toxic or poisonous at low concentrations. Examples are mercury, lead, copper and cadmium. Some toxicants can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation. They are also known to accumulate in benthic environments, such as estuaries and bay muds: a geological record of human activities of the last century. DDT is a very toxic chemical that was used as a pesticide in mass quantities throughout the United States and is known to be neurotoxic, a reproductive toxin, an endocrine disruptor, and a carcinogen. DDT is a major focus of the book Silent Spring published by Rachel Carson in 1962. This is often attributed to launching the modern environmental movement and setting the stage for the creation of the EPA in 1970. DDT was banned in the U.S. two years later in 1972. Unfortunately, large quantities had already entered the ocean through runoff and had been dumped directly into the ocean. This toxin impacts marine ecosystems by accumulating from lower trophic levels and up the food chain into higher trophic levels such as from arctic cod into seals, from fish then eaten by dolphins, and from cod and eels into seals. Shortly after Rachel Carson's publication of Silent Spring, PCBs were identified as another persistent, toxic chemical that has been released in extensive quantities to the environment. PCBs are a very well-studied class of chemicals that are manufactured from oil. These chemicals are banned in the United States under the Toxic Substance Control Act, but are still found in the soil, air, sediments, and biota. PCBs are known to accumulate in the fatty tissues of animals. In particular, PCBs build up and are stored in the blubber of marine mammals including dolphins and killer whales. These chemicals cause reproductive issues for many species. In mud crabs, PCBs have been discovered to be immunotoxic by reducing resistance to bacterial disease, reducing antioxidant enzyme activity, and damaging DNA responsible for immune system functions. PFAS are an important emerging class of man-made persistent toxicants that contain extremely strong carbon-fluorine bonds which make these chemicals extremely difficult to break down. They have unique properties that make them useful for manufacturing a wide variety of products such as firefighting foams, clothing, carpets, and fast food wrappers. These useful properties in manufacturing unfortunately translate to problematic properties in the environment and organisms from plants to people. Because PFAS are not broken down in the environment, they have been circulated through the air and water to essentially all regions of the atmosphere, land, and ocean. These chemicals have many negative effects on marine life, such as significantly inhibited growth of phytoplankton over time and accumulation in seals, polar bears, and dolphins. Current research is underway investigating the full extent of the harm to marine ecosystems caused by PFAS.
Specific examples
Chinese and Russian industrial pollution such as phenols and heavy metals in the Amur River have devastated fish stocks and damaged its estuary soil. Acute and chronic pollution events have been shown to impact southern California kelp forests, though the intensity of the impact seems to depend on both the nature of the contaminants and duration of exposure. Due to their high position in the food chain and the subsequent accumulation of heavy metals from their diet, mercury levels can be high in larger species such as bluefin and albacore. As a result, in March 2004 the United States FDA issued guidelines recommending that pregnant women, nursing mothers and children limit their intake of tuna and other types of predatory fish. Some shellfish and crabs can survive polluted environments, accumulating heavy metals or toxins in their tissues. For example, mitten crabs have a remarkable ability to survive in highly modified aquatic habitats, including polluted waters. The farming and harvesting of such species needs careful management if they are to be used as a food. Surface runoff of pesticides can alter the gender of fish species genetically, transforming male into female fish. Heavy metals enter the environment through oil spills – such as the Prestige oil spill on the Galician coast and Gulf of Mexico which unleashed an estimated 3.19 million barrels of oil – or from other natural or anthropogenic sources. In 2005, the 'Ndrangheta, an Italian mafia syndicate, was accused of sinking at least 30 ships loaded with toxic waste, much of it radioactive. This has led to widespread investigations into radioactive waste disposal rackets. Since the end of World War II, various nations, including the Soviet Union, the United Kingdom, the United States, and Germany, have disposed of chemical weapons in the Baltic Sea, raising concerns of environmental contamination. The Fukushima Daiichi nuclear disaster in 2011 caused radioactive toxins from the damaged power plant to leak into the air and ocean. There are still many isotopes in the ocean, which directly affects the benthic food web and also affects the whole food chain. The concentration of 137Cs in the bottom sediment that was contaminated by water with high concentrations in April–May 2011 remains quite high and is showing signs of very slow decrease with time. During the 20th century, large amounts of DDT, petroleum products, radioactive materials, sulphuric acid, and other toxins were dumped in the Pacific Ocean off the coast of Southern California.
=== Underwater noise ===