Ocean Pollution Crisis: How Much Water Is Poisoned?

Ocean pollution is a significant environmental issue that poses a threat to the health of our planet. Oceans are now acidifying faster than they have in 300 million years, and plastic waste is a major contributor to this problem. The majority of the garbage that enters the ocean each year is plastic, and it is estimated that there is currently between 75 and 199 million tons of plastic and waste in our oceans. This plastic waste comes from a variety of sources, including runoff pollution from land-based activities, littering, illegal dumping, and poor waste disposal practices. Oil from boats, airplanes, cars, and factories also contributes to water pollution, along with raw sewage and agricultural runoff. The consequences of ocean pollution are severe, including the release of chemicals that are absorbed by marine life and the disruption of marine ecosystems and food webs.

Plastic pollution

The majority of plastic pollution in the oceans is caused by littering and the mismanagement of waste. People use single-use plastic items for a short time (for example, the average use of a plastic bag is just 12-15 minutes) and then dispose of them improperly, causing them to end up in waterways and, eventually, the ocean. Rivers are the main arteries that carry plastic from land to sea, and coastal cities in middle-income countries are the world's plastic emissions hotspots. Over 80% of ocean-bound plastic comes from Asia, although many European countries also ship their plastic waste to Asia.

Plastic in the ocean has a devastating impact on marine life and ecosystems. Marine animals such as birds, whales, fish, and turtles mistake plastic for food, and ingest it or become entangled in it. This can cause internal and external injuries, intestinal injury, and death, and plastic is transferred up the food chain to bigger fish, marine mammals, and humans. It is estimated that over 56% of all marine life has ingested plastic, and 17% of the species affected by plastic in the ocean are on the International Union for Conservation of Nature Red List of Threatened Species. Floating plastic can also help transport invasive species, threatening marine ecosystems, biodiversity, and the food web.

Microplastics have been found in human blood and placentas and in food and drinks, including tap water, beer, and salt. Several chemicals used in plastic production are known to be carcinogenic and can cause developmental, reproductive, neurological, and immune disorders. Plastic pollution also affects the economy, with income declines in sectors such as small and medium enterprises, tourism, fisheries, and agriculture.

There have been some efforts to combat plastic pollution, such as the UN Environment Assembly's resolution "End plastic pollution: towards an International legally binding instrument," which aims to address plastic pollution throughout the entire lifecycle of plastic, from source to sea. Local and global organizations, companies, and initiatives are also working to clean up plastic pollution. However, it is clear that more needs to be done to address this urgent issue.

Oil and chemical discharge

Oil spills have devastating and long-lasting impacts on marine ecosystems. Oil on the ocean surface blocks sunlight, reduces dissolved oxygen levels, and harms plant life and the insulating properties of feathers and fur, leading to hypothermia in birds and marine mammals. Oil ingestion is toxic to animals and can slow the long-term recovery of affected populations. Oil spills also have economic repercussions, impacting tourism, commerce, and industries that rely on seawater.

In addition to large spills, routine ship operations, such as bilge pumping, contribute to oil pollution. Each discharge is relatively small, but thousands of releases add up to a significant amount of oil in the oceans. This type of pollution is challenging to measure as it is often done clandestinely, as it is illegal for ships to release bilge into ocean waters.

Chemical discharges from factories, raw sewage overflow, and agricultural runoff also play a significant role in marine pollution. These discharges introduce harmful substances such as pesticides, pharmaceuticals, personal care products, heavy metals, and industrial waste into the oceans. Even chemicals banned decades ago, like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), are still found in high concentrations in deep-sea creatures, impacting their reproductive abilities and reducing offspring survival rates.

Excess chemical fertilisers used in agriculture eventually make their way into the oceans, contributing to nitrogen-phosphorus pollution. On average, around 20% of nitrogen fertiliser is lost through surface runoff or leaching into groundwater, and up to 60% can vaporise and later fall into the ocean. The use of organic fertilisers at half strength or less frequently can help reduce this form of pollution.

Sewage and wastewater

There are several causes of sewage pollution in the ocean. One major cause is the lack of proper sanitation and wastewater treatment facilities in many parts of the world. In some areas, treatment plants exist but may be inadequate due to a lack of repair, maintenance, or flooding during the rainy season, leading to the generation of more wastewater than the plant can handle. In these cases, the excess wastewater is often released into nearby streams, bays, and rivers, which eventually flow into the sea. Additionally, sewage can be absorbed into the soil when pumped into the ground, but this does not completely filter out the pollutants.

Another cause of sewage pollution is the direct discharge of untreated or partially treated sewage into the oceans. This can occur through ageing infrastructure, facility malfunctions, or heavy rains that overwhelm sewage treatment systems, leading to combined sewer overflows. Even in countries with strict rules to prevent sewage discharge, such as the United States, wastewater treatment facilities may still release untreated wastewater into the environment due to system overloads. Cruise ships also contribute significantly to sewage pollution, discharging an estimated 95,000 cubic metres of sewage from toilets and 5,420,000 cubic metres from sinks, galleys, and showers into the oceans each day.

The impact of sewage pollution on ocean health is significant but often overlooked due to the cultural taboo of discussing sewage. Sewage pollution can lead to eutrophication, creating "dead zones" in marine environments where oxygen levels are depleted, suffocating plants and animals. It can also cause harmful algal blooms, which can produce neurotoxins that affect wildlife such as whales and sea turtles. Additionally, sewage pollution has been linked to illnesses in humans, with EPA estimates suggesting that 3.5 million Americans contract health issues such as skin rashes, pink eye, respiratory infections, and hepatitis from sewage-laden coastal waters each year.

To address the issue of sewage and wastewater pollution, several solutions have been proposed. One approach is to build and update wastewater treatment systems in communities worldwide, although this can be costly and time-intensive. Alternative solutions include the introduction of wetlands, ditches, and reed beds, which act as natural purification mechanisms by utilising bacteria and fungi to digest organic material in the water. Additionally, behavioural interventions have been explored to shift human behaviour and reduce water pollution.

Nonpoint source pollution

One common example of nonpoint source pollution is urban runoff. When rain or snowmelt moves across surfaces like parking lots, roads, or roofs, it picks up various pollutants, including motor oil, oil-based chemicals, and contaminants from human activities. This polluted runoff eventually flows into nearby streams, rivers, lakes, or oceans, impacting the health and aesthetics of these water bodies.

Agricultural practices also contribute significantly to nonpoint source pollution. Pesticides, fertilizers, and manure used in farming can be washed into nearby water bodies during rainstorms or irrigation. Additionally, soil erosion from tilled fields can result in sediment runoff, leading to increased turbidity and reduced light penetration in aquatic ecosystems.

Forestry operations, boating activities, and household runoff are other sources of nonpoint pollution. Forestry practices, such as clear-cutting or road construction, can increase soil erosion and sediment runoff into nearby streams and rivers. Boating and marina activities can contribute to water pollution through oil spills, chemical discharges, and sewage disposal. Household runoff, including lawn chemicals, pet waste, and improper waste disposal, can also carry pollutants into storm drains and, ultimately, into larger water bodies.

The impact of nonpoint source pollution on coastal communities can be significant. High population densities along coastlines further exacerbate this issue. As nonpoint source pollution affects the beauty and health of coastal areas, it can deter tourism and impact the commercial fishing industry. The economic and social conditions of these communities may deteriorate, and property values can decrease due to the decline in environmental quality.

Noise pollution

Ocean noise pollution is a form of environmental pollution caused by human activities that generate unnatural and excessive sound underwater. Sources of ocean noise pollution include commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, and military sonar. These activities can have detrimental effects on marine life, which relies heavily on sound for survival.

Marine animals use sound to navigate, communicate, find food, locate mates, and avoid predators. Noise pollution can interfere with these activities, leading to serious and sometimes fatal consequences. It can cause hearing loss in marine mammals and disrupt their natural behaviours and communication. For example, seismic activities searching for oil and gas deposits can emit deafening noise pulses of up to 260 decibels, which can drive away or even kill marine animals.

Shipping is another major contributor to ocean noise pollution. Globally, just 15% of the fleet accounts for half of the noise emissions caused by shipping. With shipping increasing massively in recent decades, ocean noise pollution in many marine areas has doubled every decade since the 1960s. Cargo ships can emit noise levels of up to 190 decibels, which is much louder than a plane taking off.

The impacts of ocean noise pollution on marine life are significant. It can alter the feeding behaviour of whales, increase their stress levels, and lead to changes in their individual and social behaviour. It can also mask the sounds produced by marine wildlife, affecting their health and the functions of marine ecosystems. However, unlike other ocean stressors such as warming or chemical pollution, the effects of noise pollution can be reversed almost instantly by reducing anthropogenic sound.

To address ocean noise pollution, international regulations and policies are needed to reduce propeller noise from ships, mitigate the sounds of sonar equipment, seismic air guns, pile driving, and construction. Quieter technologies and alternative methods, such as 'marine vibroseis' instead of airguns, should also be implemented. By reducing noise at the source, we can improve the ocean soundscape and enable the recovery of marine life.

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