Helena Joyce
Ocean pollution is a pressing environmental issue that poses a serious threat to the health and well-being of our planet. Oceans cover 70% of the Earth's surface and are essential for the health of marine and land-based ecosystems. Human activities have led to the contamination of our oceans with a wide range of pollutants, including plastics, toxic chemicals, sewage, fertilisers, and heavy metals. These pollutants have far-reaching consequences, including harm to marine life, compromised biodiversity, negative health outcomes for humans, and economic impacts on industries such as fisheries and tourism. The effects of ocean pollution are exacerbated by global climate change, and despite growing recognition of the issue, gaps remain in our understanding of its sources, levels, and impacts.
| Characteristics | Values |
|---|---|
| Marine debris | Plastic, derelict fishing gear, abandoned vessels, microplastics |
| Marine species affected | Dolphins, fish, sharks, turtles, seabirds, crabs, penguins, whales |
| Human health | Contaminated seafood, cancer, birth defects, disease |
| Chemical contamination | Nitrogen, phosphorus, mercury, pesticides, petroleum, pharmaceuticals, heavy metals |
| Environmental impact | Eutrophication, harmful algal blooms (HABs), dead zones, oxygen depletion |
| Economic impact | Negative impact on fishing and tourism industries |
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What You'll Learn
Chemical contamination
One of the significant impacts of chemical contamination is the proliferation of algal blooms, also known as Harmful Algal Blooms (HABs). These blooms are promoted by the increased concentration of chemicals, particularly nitrogen and phosphorus, in coastal waters. While algal blooms can be toxic to wildlife and harmful to humans on their own, their decomposition further exacerbates the problem. When dense algal blooms die off, they severely deplete the dissolved oxygen in the water, creating "dead zones" where marine life struggles to survive. These dead zones have detrimental effects on fisheries and tourism, with one of the largest occurring annually in the Gulf of Mexico due to nutrient pollution from the Mississippi River watershed.
The sources of chemical pollutants in the ocean are diverse and widespread. Crude oil and petroleum product spills, such as the Deepwater Horizon oil spill, have had catastrophic ecological consequences. Other sources include antifoulants, pesticides, pharmaceuticals, personal care products, and heavy metals. These toxic chemicals accumulate in the food chain, impacting both marine life and human health. Small organisms ingest toxins, which are then passed on to larger predators, including seafood that humans consume. The presence of these toxins in human tissue has been linked to long-term health issues, cancer, and birth defects.
Additionally, chemical contamination can disrupt the production of oxygen by beneficial marine microorganisms, further exacerbating oxygen depletion in the ocean. This reduction in oxygen levels has detrimental effects on the health of marine ecosystems, leading to the death of various marine animals, including penguins, dolphins, whales, and sharks.
Addressing chemical contamination in the ocean requires a multifaceted approach. It involves regulating the use and runoff of chemicals in agriculture, implementing better waste management practices, and mitigating the release of toxic chemicals from industrial sources. By tackling these issues, we can help reduce the harmful effects of chemical contamination on marine ecosystems and human health.
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Marine debris
Common types of marine debris include various plastic items like shopping bags, beverage bottles, cigarette butts, bottle caps, food wrappers, and plastic packaging. Microplastics, smaller than 5 mm, are another type of marine debris that is of particular concern. These tiny plastic particles can be ingested by marine organisms and accumulate in their bodies, potentially harming them and any creatures that eat them, including humans. Abandoned and derelict vessels (ADVs) are another highly visible form of marine debris, with thousands littering coastal waters and threatening the environment and human activities.
The impact of marine debris on wildlife and habitats is evident in many coastal and island refuges across the world. For example, in the Northwestern Hawaiian Islands National Wildlife Refuge, which spans 1,200 nautical miles of the Pacific Ocean, marine debris threatens the diverse marine and coastal ecosystems found there, including coral atolls, rocky shorelines, and sandy beaches. Similarly, in Palmyra Atoll and Kingman Reef National Wildlife Refuges, shipwreck debris has fuelled outbreaks of algae and invasive corallimorphs, damaging the delicate reef ecosystem.
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Eutrophication and algal blooms
Eutrophication is a process that occurs when a body of water becomes enriched with nutrients, leading to an increase in the growth of aquatic plants and algae. This process can occur naturally over time, but human activities such as agricultural runoff, wastewater discharge, and air pollution have accelerated eutrophication in many water bodies. The main sources of nutrients that contribute to eutrophication are phosphorus and nitrogen, which can come from agricultural runoff, wastewater discharge, and air pollution. These nutrients can also enter water bodies through human waste, household cleaning products, and soaps, as well as overflow events caused by storms and flooding that wash raw sewage into water bodies.
As the levels of nitrogen and phosphorus in the water increase, they surpass the capacity of the water to purify itself. This abundance of nutrients, particularly phosphate, encourages the rapid growth of plants and algae, known as algal blooms. Algal blooms can also be influenced by warm water temperatures and light availability, as algae need light to photosynthesize. Eutrophication sets off a chain reaction in the ecosystem, as the excess algae and plant matter eventually decompose, producing large amounts of carbon dioxide.
This increase in carbon dioxide leads to a process known as ocean acidification, which lowers the pH of seawater. Acidification slows the growth of fish and shellfish and can even prevent shell formation in bivalve mollusks, such as oysters, clams, and scallops. The decomposition of algae also contributes to oxygen depletion in the water, creating hypoxic or anoxic conditions that can be harmful to fish and other wildlife. Additionally, some species of algae produce toxins that are harmful to fish, animals, and humans.
Harmful algal blooms (HABs) have various impacts on human health and the environment. They can cause acute illnesses and potentially contribute to chronic health issues. HABs also hurt local fishing and tourism industries, leading to economic losses. HABs are monitored by organizations such as NOAA, which provides information to help protect public health, such as deciding whether beaches need to be temporarily closed. While HABs cannot be prevented, managing nutrient pollution and reducing excessive nutrient inputs into water bodies can help mitigate their impacts and protect ecosystems and human health.
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Plastic pollution
The impacts of plastic pollution on marine life are devastating and often deadly. Plastic debris can cause ingestion, suffocation, and entanglement, leading to internal injuries, intestinal injuries, and even death. Wildlife such as birds, whales, fish, and turtles mistake plastic waste for food, which can fill their stomachs and lead to starvation. Plastic ingestion can also cause developmental toxicity, affect the body's endocrine system, and lead to neurological, reproductive, and immune disorders. For example, research has found that corals that come into contact with plastic have an 89% chance of contracting diseases, compared to a 4% likelihood for corals that do not.
Floating plastic debris can also transport invasive species, threatening marine ecosystems, biodiversity, and the food web. Microplastics, tiny particles of plastic that result from the breakdown of larger plastics, can be ingested by marine animals and enter the food chain. These microplastics have been found in seafood, tap water, salt, beer, and even in the soil where we grow our vegetables. While the long-term effects of microplastics on human health are not yet fully understood, studies indicate that plastic can pass through the blood-brain barrier in mice within two hours of consumption.
The presence of plastic in the ocean also has economic implications. Marine ecosystems provide benefits valued at up to $50 trillion per year through ecosystem services. However, plastic pollution is estimated to reduce the value of these services by $500 to $2500 billion per year. Additionally, derelict fishing gear poses a safety risk to vessels at sea if it gets stuck in propellers.
Addressing plastic pollution requires global cooperation and ambitious reductions in plastic production. Phasing out harmful products and chemicals, improving waste management practices, and adopting strong national plans and compliance mechanisms are crucial steps in mitigating the harmful effects of plastic pollution on ecosystems.
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Agricultural pollution
One of the most concerning aspects of agricultural pollution is the introduction of nitrogen and phosphorus, also known as nutrient or eutrophic pollution. Agriculture is a primary source of these pollutants, through the runoff of excess nutrients from animal manure and chemical fertilizers. This type of pollution has led to the global issue of harmful algal blooms (HABs), which can be toxic to marine life and ecosystems. When these dense algal blooms die off, they severely deplete the dissolved oxygen in the water, creating "'dead zones'" where marine life struggles to survive.
The excessive use of chemical fertilizers in agriculture has resulted in a tenfold increase in their use since the mid-20th century. This has had a direct impact on the ocean, with nitrogen discharges from rivers into the sea rising by 43% between 1970 and 2000, with agriculture being the primary source. The global spread of industrialized agriculture has also contributed to the extension of HABs into previously unaffected regions.
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Frequently asked questions
Marine pollution is defined by the 1982 UN Convention on the Law of the Sea as "the introduction by man, directly or indirectly, of substances or energy into the marine environment … which results or is likely to result in such deleterious effects as harm to living resources and marine life."
Ocean pollution is caused by human activities, including littering, illegal dumping, poor waste disposal practices, stormwater discharge, agricultural runoff, and extreme natural events like tsunamis.
Ocean pollution has contaminated seafood, created massive dead zones, and compromised biodiversity. It has also led to the ingestion of toxins by small organisms, which are then eaten by larger predators, including humans, potentially leading to long-term health conditions, cancer, and birth defects.
Plastic pollution in the ocean has harmed ocean wildlife, including dolphins, fish, sharks, turtles, seabirds, and crabs. It has also contributed to the creation of garbage patches, such as the Great Pacific Garbage Patch, which is composed primarily of microplastics.
Solutions to ocean pollution include prevention through improved waste management practices and cleanup efforts. Many countries have also enacted regulations to limit or ban the use of disposable plastic items.
