Ocean Contamination: Understanding The Impact Of Pollutants

Ocean pollution, also known as marine pollution, is a mixture of chemical contamination and trash. The ocean is contaminated by a variety of toxins, including mercury, pesticides, fertilisers, oil, sewage, and plastic. These pollutants enter the ocean through runoff, rivers, and direct discharges, with over 80% of ocean contamination originating from land-based sources. The sources of these contaminants range from individual cars, boats, and farms to industrial activities such as factory runoff and chemical leaks. The effects of ocean pollution are detrimental, causing a loss of marine life, endangering species, and impacting human health through the consumption of contaminated seafood.

Plastic pollution

The majority of plastic pollution in the ocean is caused by littering. Humans buy or use disposable plastic items such as food wrappings, plastic bags, razors, and bottles, and do not dispose of them properly. As a result, these items end up in waterways and, eventually, the ocean. In addition, about 20% of the ocean's plastic pollution comes from industrial fishing, and lost fishing gear, also known as ghost gear, accounts for a significant portion of this.

The impact of plastic pollution on marine life and ecosystems is devastating. Plastic debris can cause damage to animals through suffocation, entanglement, laceration, infection, and internal injuries. Sea turtles, for example, can mistake plastic bags for food, leading to choking and internal injuries or starvation as their stomachs fill up with plastic. It is estimated that half of the world's sea turtles have ingested plastic. In addition, hundreds of thousands of seabirds ingest plastic each year, and it is predicted that by 2050, 99% of seabird species will have eaten plastic. Marine mammals also ingest plastic and get tangled up in it, with whales consuming millions of plastic particles each day as they filter-feed in the oceans.

Beyond the direct impact on individual animals, plastic pollution also has broader ecological consequences. Plastic debris accumulates in garbage patches in the center of the ocean's gyres. The Great Pacific Garbage Patch, located between Hawaii and California, is a well-known example, containing 1.8 trillion pieces of plastic and covering an area twice the size of Texas. Plastic pollution has also been found in all five of the Earth's major ocean gyres, from the equator to the poles, and even in the Arctic ice sheets and the seafloor. Not a single square mile of surface ocean anywhere on Earth is free from plastic pollution.

The presence of plastic in the ocean also contributes to chemical contamination. As plastic breaks down, it can release toxic chemicals, such as bisphenol A (BPA), into the marine environment, which can have harmful effects on marine life and potentially enter the human food chain.

Addressing plastic pollution requires a combination of individual actions and systemic changes. Individuals can play a role by reducing their use of single-use plastics, properly disposing of plastics, and opting for reusable and recyclable alternatives. However, the scale of the problem also calls for industry and government action. This includes improving waste management and recycling infrastructure, regulating plastics as a pollutant, and holding companies accountable for their plastic waste.

Chemical contamination

One example of a harmful chemical contaminant is DDT, a pesticide that was commonly used in the mid-1900s and is still used in some parts of the world today. DDT has been found to cause ecological damage and harm to human health, leading to its ban or restriction in most developed nations. Despite this, contaminated sediments in estuaries continue to release DDT into the ocean, impacting marine life and entering the human food chain.

Another group of chemical contaminants is Perfluoroalkyl substances (PFAS), which are used in the manufacture of non-stick cookware, stain-resistant carpets and furniture, water-repellent clothing, and firefighting foam. PFAS chemicals are highly persistent in the environment and have contaminated surface waters, groundwater, and oceans. These chemicals have been incorporated into the marine food chain, leading to potential health risks for both marine life and humans.

Nutrient pollution is another form of chemical contamination, caused by excess nutrients such as nitrogen and phosphorus entering bodies of water. These nutrients act as fertilizers, promoting excessive algae growth that restricts sunlight and oxygen from reaching aquatic plants. This process leads to the creation of ""dead zones" where marine life cannot survive due to the lack of oxygen.

To address chemical contamination in the ocean, proper waste disposal, the reduction of runoff, and the improvement of water treatment processes are essential. Additionally, individuals can make small changes, such as choosing organic fertilizers and reducing the use of single-use plastics, to help mitigate chemical contamination and protect marine ecosystems.

Noise pollution

Marine species, such as dolphins, whales, fish, and crustaceans, are highly dependent on sound for their survival. They use vocalizations to communicate, locate prey and mates, navigate, and defend their territories. Noise pollution interferes with their ability to interpret acoustic signals and can mask the natural sounds they rely on. This disruption can lead to changes in their individual and social behaviour, affecting their ability to hunt, coordinate, and detect predators. For example, increased ship noise has caused bottlenose dolphins to simplify their vocal calls, potentially reducing the effectiveness of their communication.

The introduction of anthropogenic noise can also cause hearing loss in marine animals and even strand them, leading to death. Loud noises from activities such as seismic surveys have been known to damage the internal organs of giant squid and cause hearing damage in sea turtles. The impact of noise pollution on one species can have indirect effects on others. For instance, if a whale strands and dies on a beach due to noise, seafloor-dwelling animals that rely on its body for food will lose a crucial food source.

To reduce noise pollution in the marine environment, policies and quieter technologies are needed. This includes addressing propeller noise from ships, mitigating the sounds of sonar equipment, seismic air guns, pile driving, and construction. By reducing anthropogenic noise, marine life will be better equipped to withstand other human-induced pressures, such as overfishing and climate change.

Mercury pollution

Contaminants cause pollution in the ocean when chemicals and trash are either washed, blown, or intentionally dumped into the ocean. Most ocean pollution 80% originates on land and is caused by humans. Nonpoint source pollution, for example, is the accumulation of pollution from small sources like individual cars, boats, farms, and construction sites that can't be pinpointed. This type of pollution typically becomes ocean pollution via runoff, when rain or snow moves pollutants from the ground into the ocean.

The primary source of mercury in the environment is human activity, particularly coal-combustion electrical power generation and industrial waste disposal. Once released, mercury can be converted into methylmercury by microorganisms in soil and water, making it even more toxic and easier to accumulate in the food chain. Methylmercury is the form of mercury found in fish tissue, and it can biomagnify through marine food chains to top predators, including humans.

The effects of mercury pollution were evident in Minamata Bay, where many animals exhibited abnormal behaviors and high mortality rates after consuming contaminated seafood or absorbing mercury from seawater. Birds fell out of the sky, and fish swam in circles. The cat population in the area essentially disappeared.

To reduce mercury pollution, proper disposal of mercury-containing items, such as medicinal packaging and thermometers, is crucial. Using mercury-free bulbs and batteries and choosing consumer products with minimal mercury emissions are also essential steps. Additionally, reducing coal power usage and shifting to cleaner energy sources can minimize mercury emissions.

Nanotechnology offers promising solutions, such as using synthesized aluminum oxide nanoparticles that mimic coral structures to absorb heavy metal toxins. Another approach uses orange peels as raw material to create a polymer that can significantly reduce mercury content with a single treatment.

Radioactive waste

The ocean has a remarkable capacity to dilute nuclear contamination, but this does not eliminate the potential for harm. Radioactive isotopes can move up the food chain, affecting marine life and, eventually, humans. For instance, small fish several dozen miles south of Fukushima displayed elevated levels of radioactive cesium and iodine, and high levels of radioactivity were found in seawater 25 miles offshore. While the full extent of the damage caused by the Fukushima incident is still unknown, it is clear that the impacts will be significant and long-lasting.

To address the issue of radioactive waste in the ocean, international policies and guidelines have been developed. The London Convention of 1972, for example, aimed to control and prevent marine pollution by banning specific substances from being dumped in the ocean. Ocean floor disposal, or sub-seabed disposal, which involves delivering radioactive waste to the ocean floor and depositing it into the seabed, has been considered but never implemented. Instead, it is now recognised that radioactive material needs to be isolated and encased (in glass and concrete) to prevent leakage on the ocean floor.

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