Marine Pollution: Understanding The Human Impact

Marine pollution, also known as ocean pollution, is primarily caused by human activities along coastlines and far inland. It is a combination of chemical contamination and trash, such as plastic, oil, sewage, and agricultural and industrial waste. This waste enters the ocean through various pathways, including runoff from land, rivers, and the atmosphere, as well as direct discharge from ships and drilling operations. Natural sources, such as geothermal vents and lightning, also contribute to marine pollution, but human-made pollutants are the predominant cause. The impact of marine pollution is far-reaching, affecting marine life and ecosystems and human health, with toxins accumulating in the food chain.

Atmospheric pollution

One of the significant impacts of atmospheric pollution is the introduction of toxic chemicals into the marine environment. These chemicals, such as nitrogen, phosphorus, carbon, and pesticides, can cause an overgrowth of algae, known as algal blooms or "red tides." When these algal blooms die and decompose, they deplete the oxygen levels in the water, creating "dead zones" where marine life struggles to survive.

In addition to chemical pollution, atmospheric pollution can also contribute to marine debris or litter. This includes human-created solid material, such as discarded fishing nets and plastic pollution, which is a major threat to marine wildlife. Plastic pollution has increased tenfold since 1980, affecting at least 267 species, including marine turtles, seabirds, and marine mammals.

To address atmospheric pollution and its impact on marine environments, it is crucial to reduce littering, improve waste management practices, and transition to more sustainable alternatives, such as biopesticides, which have a shorter residual time and are generally non-toxic to beneficial invertebrates and vertebrates.

Oil spills

The largest marine oil spill in US history occurred on April 20, 2010, when the BP oil rig Deepwater Horizon exploded, resulting in the deaths of 11 workers and the discharge of over 134,000 barrels of oil into the Gulf of Mexico. This incident highlighted the challenges of removing oil from open water and prompted advancements in oil spill response techniques.

Additionally, oil spills can affect air quality due to the release of toxic chemicals such as benzenes, toluene, and poly-aromatic hydrocarbons. These chemicals can cause adverse health effects when inhaled and can also form fine particulate matter in the atmosphere, which can be inhaled and carry toxins into the human body. The cleanup and recovery process further contributes to air pollution through the generation of pollutants like nitric oxides and ozone.

Nonpoint source pollution

While human activities are a significant contributor to marine pollution, natural occurrences can also play a role. For instance, excess heat in bodies of water can be caused by natural factors such as geothermal vents, hot springs, and volcanoes. Additionally, lightning can release heat into bodies of water, and pesticides and herbicides used in agriculture can accumulate in soils, affecting biological processes and being hazardous to soil species.

Chemical contamination

Marine pollution is a pressing issue, with an estimated 171 trillion plastic particles in the world's oceans, weighing around 2.3 million tons. While plastic pollution is a significant concern, chemical contamination is another critical aspect of marine pollution, impacting the health of marine ecosystems and humans alike.

Agricultural practices also contribute to chemical contamination in marine environments through the use of pesticides and herbicides. While pesticides help control pests that affect crop yields, their accumulation in soils can have detrimental effects on soil species and enhance plant uptake of chemicals. One such pesticide, DDT, has been banned or restricted in many developed nations due to its environmental and health hazards. However, its continued use in underdeveloped countries contributes to marine water contamination.

Another significant source of chemical contamination in marine ecosystems is river and estuary systems. These waterways transport chemicals from land into the ocean through rainwater, flooding, and stormwater runoff. Estuaries, coastal wetlands, and marshes near urban areas or agricultural land often contain chemically contaminated sediments, impacting the local marine life and potentially entering the food chain.

Furthermore, individual human activities, such as the use of sunscreen, also contribute to chemical pollution in the ocean. With the majority of coral reefs located in tropical and subtropical latitudes, sunscreen application and ocean activities coincide, leading to sunscreen contamination in these environmentally sensitive habitats. Additionally, ineffective water treatment processes can contribute to the presence of chemical pollutants in marine environments.

Invasive species

An invasive species is one that has been introduced by human activity, either deliberately or accidentally, to geographic areas outside its native range. The introduction of invasive species can lead to environmental disturbances and ecological degradation, which in the case of aquatic ecosystems, can cause a marked decrease in water quality.

Shipping is the most significant vector for the introduction of marine invasive species. As much as 10 billion tonnes of ballast water is carried around the world per year, carrying up to 7,000 species of aquatic plants, microbes, and animals every hour. Large boats fill their tanks with seawater to counterbalance cargo weight at their loading port and release it, along with the species it contains, at their destination. This was the case with a European crab species that now has established populations on both US coasts, in southern South America, Australia, South Africa, and Japan. It is a ferocious predator and has affected the commercial shellfish industry, costing the American fishing industry millions of dollars.

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