Ocean Pollution: Understanding The Causes Of Water Contamination

Marine pollution is a pressing environmental issue that poses a significant threat to the health of our planet and its ecosystems. Oceans cover more than 70% of the Earth's surface and play a crucial role in sustaining life, regulating weather patterns, and providing resources for millions of people. However, human activities have led to the contamination of these vital water bodies with various pollutants, including chemicals, trash, and noise. The primary sources of ocean pollution are non-point source pollution, point source pollution, and runoff pollution, which originate from a range of human activities on land and at sea.

Marine debris

The impact of marine debris is far-reaching and detrimental, posing a danger to both wildlife and humans. Marine debris can harm or kill marine and coastal wildlife through ingestion or entanglement. It can also damage and degrade habitats, as well as interfere with navigational safety. The economic repercussions of marine debris are significant, causing losses to fishing and maritime industries and negatively impacting the quality of life in coastal communities. Moreover, it can threaten human health and safety, with plastics and microplastics ending up in the seafood we consume.

Plastics are one of the most prevalent types of marine debris, with at least 8 million tons of plastic ending up in our oceans annually. Microplastics, smaller than 5 mm, are a particular concern as they can be ingested by marine life, leading to loss of nutrition, internal injuries, intestinal blockage, starvation, and even death. Seabirds are especially vulnerable to plastic pollution, with recent studies finding plastic in 90% of seabirds. The impact of plastics is not limited to the oceans, as research has shown high concentrations of plastic particles in the Great Lakes, with Lake Erie and Lake Ontario recording over one million plastic particles per square mile.

The majority of marine debris originates from land-based sources, including littering, poor waste management practices, stormwater discharge, and extreme natural events such as hurricanes and tsunamis. However, some debris, such as derelict fishing gear and abandoned vessels, comes from ocean-based sources. Derelict fishing gear, in particular, poses a significant threat to marine life, as it can entangle and harm marine animals.

Addressing the issue of marine debris requires a multifaceted approach. While prevention and cleanup are crucial, it is essential to recognize that some debris, such as certain types of plastics, may be impossible to clean up. Therefore, a shift in society's approach to plastic use is necessary, and many countries are taking steps in this direction. According to a 2018 United Nations report, over sixty countries have implemented regulations to restrict or ban disposable plastic items. Additionally, organizations like the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration (NOAA) are actively working to address marine debris through research, education, and collaboration with partners.

Chemical contamination

Fertilisers and sewage are significant contributors to chemical contamination in ocean waters. They introduce excess nutrients, such as nitrogen and phosphorus, which promote the growth and reproduction of phytoplankton, a type of photosynthesizing algae. This results in vast algal blooms that can often be observed from space through satellite imaging. While the increased phytoplankton benefits higher levels of the food web, including zooplankton, small fish, and predatory marine mammals, it also leads to a natural increase in mortality within these populations due to the higher volumes of animal waste and faeces produced. Additionally, the algal blooms on the sea surface reduce the amount of sunlight reaching plants on the seafloor, disrupting the ecosystem's balance.

Human activities on land play a significant role in chemical contamination. Urban areas and agricultural practices are responsible for introducing various industrial, commercial, and recreational pollutants into the ocean. Ineffective water treatment systems and sewage leaks contribute to this issue, allowing pharmaceutical, health, and body care products to enter marine ecosystems. River and estuary systems are the most common pathways for chemical contamination to reach the ocean. Rainwater, flooding, and stormwater carry pollutants from land into nearby streams, rivers, and estuaries, which then transfer these contaminants into the ocean.

Another emerging concern is the impact of sunscreen on marine environments, particularly sensitive habitats such as coral reef systems. With the majority of reefs located in tropical and subtropical regions, the application of sunscreen by individuals engaging in ocean activities has become a direct source of chemical contamination. While water treatment systems and river systems also contribute to sunscreen contamination, their impact is relatively lesser. The accumulation of these chemicals in the ocean can have detrimental effects on environmentally sensitive ecosystems, such as coral reefs.

Additionally, pesticides like DDT continue to be a significant source of chemical contamination in marine waters, especially in undeveloped countries where their use is still unregulated. Even in regions that no longer utilise DDT, contaminated estuarine sediments can release previously bound DDT through sedimental shifts, highlighting the persistence of this chemical pollutant. With water treatment systems not being entirely effective in removing anthropogenic products and annual flooding events occurring, hundreds of man-made chemical products find their way into the ocean, posing ecological and human health risks.

Noise pollution

The effects of noise pollution are not limited to marine mammals but can also have indirect effects on other species. For instance, if a whale strands on a beach due to noise pollution, the seafloor-dwelling animals that rely on the whale's body as a food source are left without a key food source. Additionally, noise pollution can interfere with the detection of acoustic signals in the marine environment, masking the sounds produced by marine wildlife and leading to changes in individual and social behaviour, altered metabolisms, and hampered population recruitment.

To mitigate the impacts of noise pollution on marine life, policies and regulations are needed to reduce propeller noise from ships and mitigate the sounds of sonar equipment, seismic air guns, pile driving, and construction. Quieter technologies and improvements in ocean noise monitoring and management are also essential to reducing noise pollution and improving the ocean soundscape, enabling the recovery of marine life.

Oil spills

Cleanup and recovery from an oil spill are challenging and expensive, depending on factors such as the type of oil, water temperature, and shoreline characteristics. Physical cleanups can be very costly, and spills may take weeks, months, or even years to clean up. During the cleanup process, air pollutants such as nitric oxides and ozone from ships may also be generated.

Carbon emissions

Ocean acidification poses a severe threat to marine organisms, particularly shellfish and coral reefs. The changing chemistry of the ocean water makes it more difficult for shellfish to form and maintain their shells. The availability of calcium carbonate, which is crucial for shell formation, is reduced due to the increased acidity. This can have economic repercussions, especially for shellfish fisheries and industries that rely on these resources.

Coral reefs, another valuable ecosystem, are also negatively affected by ocean acidification. The process hinders the ability of corals to recover from bleaching events and other stressors. Corals require calcium carbonate to grow and maintain their structures, and the reduced levels of this compound in more acidic waters impact their health. Warmer ocean temperatures further compound the issue, as the rate at which water absorbs CO2 decreases as temperature increases.

Addressing the root cause of carbon emissions and transitioning towards renewable energy sources, such as offshore wind and ocean energy, are crucial steps in mitigating ocean acidification and reducing water pollution in the ocean.

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