Human Impacts: Four Main Causes Of Marine Pollution

Marine pollution is a pressing environmental issue that poses a significant threat to the health of our planet and the ecosystems that regulate it. The four main causes of marine pollution are non-point source pollution, oil spills, plastic pollution, and excess nitrogen and phosphorus in seawater. Non-point source pollution refers to the accumulation of pollution from various small sources, such as individual cars, boats, farms, and construction sites, which eventually make their way into the ocean through runoff. Oil spills, another major cause, release harmful oil into the ocean, ensnaring and suffocating marine animals and damaging their habitats. Plastic pollution, which accounts for 80% of all marine pollution, is caused by littering, wrongful fishing activities, and poor waste management, leading to the entanglement and ingestion of plastic by marine life. Lastly, excess nitrogen and phosphorus in seawater stimulate algal blooms, also known as red tides, which produce toxic effects harmful to marine life and humans. These four causes of marine pollution highlight the urgent need for collective action to protect our planet's health and ecosystems.

Nonpoint source pollution

• Excess fertilisers, herbicides, and insecticides from agricultural lands and residential areas.
• Oil, grease, and toxic chemicals from urban runoff and energy production.
• Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks.
• Salt from irrigation practices and acid drainage from abandoned mines.
• Bacteria and nutrients from livestock, pet wastes, and faulty septic systems.
• Atmospheric deposition and hydrologic modifications.

NPS pollution can have severe environmental, social, and economic impacts. It can affect marine ecosystems, drinking water supplies, fisheries, and wildlife. It can also impact the commercial fishing industry, property values in coastal communities, and human health. The pollutants in NPS runoff can be harmful and have various sources, including vehicles, farms, boats, and industrial activities.

Correcting the harmful effects of NPS pollution is costly, and efforts are being made to control and prevent it. The US Environmental Protection Agency (EPA), National Oceanic and Atmospheric Administration (NOAA), and other agencies are working to monitor, assess, and limit NPS pollution.

Oil spills

The largest marine oil spill in US history occurred on April 20, 2010, when the BP oil rig Deepwater Horizon exploded, killing 11 workers and spilling more than 134,000 barrels of oil into the Gulf of Mexico. This incident had devastating effects on the environment, with oil spreading rapidly across the water's surface, forming a thin oil slick that eventually became a very thin sheen, often resembling a rainbow. Oil spills can also contaminate drinking water supplies, as seen in 2013 when two separate spills impacted the water supply for 380,000 people in Miri, Malaysia, and Coca, Ecuador.

Cleanup activities after oil spills are challenging, and it is impossible to remove 100% of the spilled oil. Scientists must carefully choose methods that do not cause additional harm, as seen in the Exxon Valdez oil spill in 1989, where high-pressure, hot-water hoses used for cleanup caused more damage than the oil itself. The Oil Pollution Act of 1990 established that those responsible for oil spills can be held accountable for the cleanup and restoration costs. Federal, state, and tribal agencies work together with the responsible party to select restoration projects and assess the impacts of the spill.

Plastic pollution

The primary source of plastic pollution in the marine environment is land-based activities, contributing to approximately 80% of the pollution. This includes littering, improper waste disposal, and industrial runoff. Single-use plastics, such as plastic bags and food packaging, are a significant contributor to plastic pollution. These items are often discarded improperly and end up in waterways, eventually making their way into the ocean. Plastic debris accumulates in ocean gyres, forming massive garbage patches, with the Great Pacific Garbage Patch being the largest.

Microplastics, tiny plastic particles smaller than 0.2 inches, are another critical concern. They can come from larger plastics breaking down over time or be directly released into the environment through activities like washing synthetic clothing, which sheds microplastic fibers. These microplastics are easily ingested by marine organisms, causing internal injuries and transferring plastic up the food chain to larger animals, including humans.

The impact of plastic pollution on marine life is devastating. Marine mammals, such as whales, seals, and sea turtles, ingest plastic or become entangled in it, leading to injuries and death. Seabirds that feed on the ocean surface are also prone to ingesting plastic, which they then feed to their chicks, affecting their growth and survival. According to one study, approximately 98% of sampled chicks contained plastic.

Additionally, plastic debris can act as a transport mechanism for invasive marine species and pollutants. Persistent organic pollutants adhere to the surface of plastic debris, allowing them to be transported through ocean currents. As a result, marine life that ingests plastic coated with these toxins absorbs them into their bodies, further spreading them up the food chain and eventually reaching humans.

To address plastic pollution, a multifaceted approach is necessary. While individual efforts to reduce, reuse, and recycle plastic materials are essential, it is also crucial to advocate for better waste management practices, hold industries accountable for their plastic waste, and support initiatives that aim to prevent plastic from entering waterways and the ocean.

Chemical pollution

Marine pollution is defined by the 1982 UN Convention on the Law of the Sea as "the introduction by man, directly or indirectly, of substances or energy into the marine environment... which results or is likely to result in such deleterious effects as harm to living resources and marine life." Chemical pollution is a significant aspect of this, encompassing a range of toxic substances that can have detrimental effects on marine ecosystems and human health.

One of the critical issues with chemical pollution is its persistence in the marine environment. Even chemicals banned decades ago, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), continue to be found in high concentrations in the deep sea. These persistent organic pollutants (POPs) accumulate in the tissues of marine organisms and can biomagnify in the food chain, reaching harmful levels in top predators, including humans.

Oil spills are another significant source of chemical pollution in the marine environment. While major oil spills have declined due to improved technologies and policies, they still occur and have devastating impacts on marine life. Oil can ensnare and suffocate marine animals, impair the ability of seabirds to fly or feed, and cause cancer and reproductive issues in those who survive. Oil spills contribute to the overall petroleum pollution in the oceans, which also includes crude oil and other petroleum products, antifoulants, and shipping-related discharges.

In addition to the direct harm caused by chemical pollution to marine organisms, there are also indirect effects on human health. Toxic chemicals, such as mercury, can become concentrated in the food chain as they are absorbed and accumulated by organisms at higher trophic levels. This process, known as biomagnification, results in high levels of toxicants in fish and other seafood consumed by humans, potentially leading to long-term health issues, cancer, and birth defects.

To address chemical pollution in the marine environment, international agreements, such as the London Convention and its updated version, the London Protocol, have been implemented. These agreements aim to prohibit or strictly regulate the disposal of hazardous materials at sea. However, enforcing these regulations remains a challenge, and the persistent nature of chemical pollutants means that they continue to pose a threat to marine ecosystems and human health.

Deep-sea mining

However, deep-sea mining is also likely to have a range of environmental impacts. Firstly, the noise from mining vehicles and equipment can interfere with communication between marine mammals, affecting species such as whales, tuna and sharks. This is particularly concerning given that sound travels faster and over larger distances in water than in air.

Secondly, light pollution from artificial lights used to control mining vehicles and monitor sites can disturb organisms adapted to the darkness of the deep sea, many of which have reduced visual capacity. This light pollution can also impact species that use bioluminescence to communicate and find prey.

Thirdly, the physical act of mining will involve scraping the seabed, which will kill plants and animals and remove or disturb the top layer of sediment, leading to the potential extinction of species living on or within it. The sediment plumes created by mining can smother and suffocate organisms, impacting marine life in all zones of the ocean.

Finally, the discharge of wastewaters containing sediment, mining fines and toxic compounds back into the ocean can form mid-water plumes that cloud the water column and introduce toxic concentrations of metals to marine food webs. This can affect filter-feeding organisms and increase seawater temperatures, reduce oxygen levels and disturb carbon-rich sediments, impacting the ocean's ability to store carbon.

Overall, deep-sea mining has the potential to cause severe harm to marine biodiversity and ecosystems, and there are concerns that the marine environment cannot be effectively protected from its harmful effects. While it may provide access to valuable mineral deposits, the potential environmental and ecological impacts must be carefully considered and adequately addressed before any large-scale operations are allowed to proceed.

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