Ocean Pollution: The Human Factor

Plastic is the leading source of ocean pollution, with 14 million tons ending up in the ocean each year, making up 80% of marine debris. Rivers are a major contributor to this, with 1000 rivers responsible for nearly 80% of global annual riverine plastic emissions. The remaining 20% of plastic emissions are distributed over 30,000 rivers. Most of the plastic in our oceans comes from land-based sources, with only 20-30% coming from marine sources such as fishing nets, lines, and ropes. Nonpoint source pollution is another significant contributor to ocean pollution, which includes small sources like septic tanks, cars, and trucks, as well as larger sources like farms and ranches.

Plastic pollution

Plastic debris in the ocean has severe ecological and environmental impacts. It injures and kills marine life, including fish, seabirds, and mammals. It has impacted at least 267 species worldwide, including sea turtles, seabirds, and marine mammals. Plastic pollution also affects the human food chain, as fish and other marine organisms ingest plastic fragments. A 2008 study found that 35% of the fish caught during a Pacific Gyre voyage had ingested plastic pieces.

Microplastics, particles less than 5 millimeters in width, are a significant component of plastic pollution. They are generated from vehicle tires, textiles, and other sources, and can be found suspended from the ocean surface to the seafloor. Microplastics mimic fish eggs and other tiny organisms, making them more likely to be consumed by marine life. Once in the ocean, they are challenging and costly to filter out, becoming a permanent feature of the ecosystem.

To address plastic pollution, a global approach is necessary. This includes reducing plastic waste, improving waste management practices, and promoting eco-friendly alternatives to disposable products. Governments and industries have the most power to effect large-scale change, but individuals also have a role in preventing plastic pollution by reducing their plastic consumption and properly disposing of plastic waste.

Nutrient pollution from fertilisers

Agricultural practices, including the use of fertilisers and animal manure, contribute significantly to nutrient pollution. When nitrogen and phosphorus from fertilisers are not fully utilised by crops, they can be washed away from farm fields, ending up in nearby waterways and, eventually, the ocean. This runoff can also occur through soil erosion, with nitrogen being lost from fields in the form of gaseous compounds.

Urban areas also play a role in nutrient pollution from fertilisers. Lawn and garden fertilisers, as well as wastewater and stormwater runoff from populated areas, can carry excess nutrients into water bodies. This is particularly true in regions with a high population density and a large number of coastal residents.

Nutrient pollution has severe ecological consequences. The rapid growth of algae caused by excess nutrients blocks sunlight and oxygen from reaching aquatic plants, leading to their decay. This further depletes oxygen levels in the water, creating an uninhabitable environment for marine life. Additionally, harmful algal blooms (HABs) can produce toxins that are dangerous to both humans and aquatic ecosystems.

To address nutrient pollution from fertilisers, several solutions can be implemented. Farmers can adopt improved nutrient management techniques, such as applying the right amount of fertiliser at the appropriate time and location. Conservation practices, such as planting field buffers and implementing conservation tillage, can also help prevent nutrient runoff and improve soil health. Engaging in watershed efforts and collaborating with various stakeholders can further reduce nutrient losses and mitigate the impact of nutrient pollution on our oceans.

Nonpoint sources

Nonpoint source pollution is one of the biggest sources of ocean pollution, accounting for 80% of all marine pollution. It occurs as a result of runoff, which carries pollutants from land into waterways and oceans. This can include small sources like septic tanks, cars, trucks, and boats, as well as larger sources such as farms, ranches, and forest areas.

Motor vehicle engines, for example, can leak small amounts of oil onto roads and parking lots, which can then be washed into nearby waterways and eventually make their way out to sea. Dirt, topsoil, or silt from fields or construction sites can also run off into rivers and oceans, harming fish and wildlife habitats. Nonpoint source pollution can make river and ocean water unsafe for humans and wildlife, and in some areas, it is so severe that beaches have to be closed after rainstorms.

Nutrient pollution is another form of nonpoint source pollution, which occurs when excess nutrients, usually nitrogen and phosphorus, enter bodies of water and act as fertilizers. These nutrients can come from agricultural runoff or wastewater generated from lawns, which generally contain fertilizers. The excess nutrients cause high levels of algae growth, which restricts sunlight and oxygen from entering the water, leading to the creation of "dead zones" where marine life cannot survive.

To combat nonpoint source pollution, organizations like NOAA's Coastal Zone Management Program are developing nonpoint source pollution control plans for coastal states. Scientists at NOAA also help track down the exact causes of nonpoint source pollution incidents and work on finding solutions to prevent future occurrences. Additionally, organizations like The Ocean Cleanup are working to tackle the 1000 most polluting rivers, which account for nearly 80% of global annual riverine plastic emissions. By developing and implementing mitigation measures and technologies, they aim to stop plastic from entering the oceans and persisting there for long periods, harming marine life and ecosystems.

Light and noise pollution

The ocean is plagued by various pollutants, with plastic being the most prevalent. Eighty per cent of ocean pollution comes from land-based sources, including rivers, coastlines, and human activities like shipping and oil exploration. While plastic pollution is a significant concern, other forms of pollution, such as light and noise pollution, also have detrimental effects on marine ecosystems and wildlife.

Light pollution in the ocean is a growing concern, though it is often overlooked. While the specific impacts of light pollution on ocean ecosystems are still being studied, it is known to affect the behaviour and physiology of marine organisms, particularly those that rely on light for vital functions like navigation, feeding, and reproduction. For example, artificial light can disrupt the migration patterns of sea turtles, confuse hatchlings trying to find the ocean, and alter the feeding behaviours of zooplankton, which form the base of the marine food chain.

Noise pollution, also referred to as anthropogenic or underwater noise, is an increasing threat to marine life, especially for species that rely heavily on sound for survival, communication, and navigation. The primary sources of ocean noise pollution include commercial shipping, oil exploration, seismic surveys, and military sonar activities. Cargo ships, in particular, can emit noise levels of up to 190 decibels, which is comparable to the noise level of a rock concert. This excessive noise can mask the natural sounds produced by marine wildlife, interfering with their communication and behaviour.

The impacts of noise pollution on marine species are significant and wide-ranging. It can cause behavioural changes, such as altered vocalizations in dolphins and whales, and even lead to hearing loss in some species. Noise pollution can also drive marine animals away from important feeding or breeding grounds, forcing them to alter their migration routes. In some cases, sudden and intense noise can cause marine animals like whales to strand themselves on beaches, leading to their death and creating knock-on effects for seafloor-dwelling animals that rely on their carcasses for food.

Addressing light and noise pollution in the ocean requires a multi-faceted approach. To mitigate noise pollution, policies should focus on reducing propeller noise from ships, regulating the use of sonar equipment, and developing quieter technologies. Similarly, reducing light pollution calls for measures such as shielding or redirecting artificial light sources near coastlines and promoting the use of energy-efficient lighting that minimizes light trespass. By implementing these strategies and raising awareness about the impacts of light and noise pollution on ocean health, we can work towards creating a more harmonious and sustainable marine environment.

Industrial chemicals

One of the main ways industrial chemicals reach the ocean is through runoff from factories and industrial sites. These facilities may discharge waste products containing harmful substances directly into waterways, which eventually flow into the sea. This was the case in Minimata Bay, Japan, where a factory discharged waste containing methyl mercury, leading to tragic consequences for human health.

Another source of industrial chemical pollution is the use of chemicals in various manufacturing processes. For example, chemicals like PFAS, phthalates, and bisphenol A (BPA) are infused into plastics to make them water-repellent, flexible, and clear. These chemicals leach into the ocean, disrupting endocrine systems and affecting reproduction in various aquatic organisms, including molluscs, crustaceans, insects, fish, and amphibians.

Pharmaceuticals, health, and body care products also contribute to industrial chemical pollution in the ocean. Medicines, sunscreen, and cleaning products can contain chemicals that, while tolerable for humans in small doses, can build up in aquatic environments and harm wildlife. For example, some chemicals in medicines have been found to cause fertility problems in fish, and sunscreen has been identified as a growing source of chemical pollution, particularly in coral reef systems.

Additionally, agricultural activities introduce industrial chemicals into the ocean through fertiliser and nutrient runoff. Excess nutrients, such as nitrogen and phosphorus, act as fertilisers in marine environments, leading to excessive algae growth. This restricts sunlight and oxygen from reaching the water, creating "dead zones" detrimental to marine life.

Addressing industrial chemical pollution requires a collective effort from governments, industries, and consumers. Initiatives like the Green Chemistry & Commerce Council, which promotes the development of environmentally degradable chemicals, offer promising steps towards mitigating this complex and pressing issue.

Frequently asked questions