Pollution's Deadly Impact On Fish Populations

Marine pollution, especially from plastic, is a critical environmental issue that poses a significant threat to marine life. While it is challenging to estimate the exact number of fish that die from pollution each year, it is evident that the impact is substantial. Plastic waste in oceans can kill fish through ingestion or entanglement, with abandoned fishing gear being a significant culprit. The presence of plastic also affects coral reefs, which provide habitats for fish and other marine animals. According to reports, there will likely be more plastic in the ocean than fish by 2050, underscoring the urgency of addressing plastic pollution to protect marine ecosystems and the livelihoods of billions of people dependent on them.

Sewage spills in England's rivers

Sewage spills into England's rivers pose a serious threat to the country's waterways and the local environment. In 2023, the number of sewage spills more than doubled compared to the previous year, with 3.6 million hours of spills recorded, up from 1.75 million hours in 2022. This increase was attributed to heavy rainfall, which can overwhelm the combined sewage systems that manage both rain and sewage in the same pipes. While sewage spilling can be legal in exceptional weather conditions, environmentalists argue that it should only occur in such circumstances.

The high number of spills has been partly blamed on a lack of oversight by regulators and the failure of water companies to invest in fixing leaky pipes. The impact of these spills is significant, with sewage containing human waste, wet wipes, and sanitary products that can endanger local wildlife and people who use the affected waterways for activities like swimming. Sewage pollution can reduce oxygen levels in the water, harming aquatic life, and can also lead to the presence of harmful microorganisms and parasites, posing risks to human health.

The River Thames, for example, experienced a significant sewage spill in March 2024 during a flood. Testing revealed up to ten times the permitted amount of E. coli bacteria for bathing water status. This incident highlights the potential consequences of sewage spills on water quality and the health of both ecosystems and humans.

To address the issue, Thames Water has been working on a £5 billion super sewer project to capture and divert sewage from the River Thames. Additionally, Water UK, the industry body for sewerage companies, has announced a £10 billion investment to upgrade sewage infrastructure across England, pending regulatory approval. These efforts aim to reduce sewage spills and mitigate their environmental and health impacts.

The situation with sewage spills in England's rivers is critical, and it is essential to hold responsible parties accountable while also recognizing the complex challenges posed by aging infrastructure, intensive farming, population growth, and climate change.

Plastic ingestion

Plastic pollution has far-reaching consequences, impacting almost every facet of the biosphere. It has been detected in all aquatic compartments and is considered an omnipresent contaminant. Laboratory and field studies have confirmed that aquatic organisms, including fish species of commercial interest to humans, ingest microplastics. This poses a potential risk to humans who consume fishery products.

The plastic ingestion rate among fish is increasing. Research has found that the average plastic ingestion rate in fish has doubled and continues to rise at a rate of 2.4 ± 0.4% year⁻¹. This increase is driven by improved detection methods and a higher incidence of fish consuming plastic. Plastic ingestion by marine fish is widespread, with 386 marine fish species, including 210 species of commercial importance, having ingested plastic debris.

The impact of plastic ingestion on fish health and, consequently, on human health through the consumption of fishery products, is a growing concern. Microplastics can release chemical substances and act as carriers of microorganisms. Additives present in microplastics, such as polybrominated diphenyl ethers (PBDE), bisphenol A (BPA), and potentially toxic elements, can be harmful to humans. However, the data available is limited, and the risk to human health from consuming fish with microplastics is not yet fully understood.

Plastic entanglement

Plastic pollution is a critical environmental issue that continues to grow in magnitude. Millions of tons of plastic waste enter the oceans each year, wreaking havoc on marine life. Marine animals that ingest plastic or become entangled in it are injured or killed. While it is challenging to estimate the exact number of marine animals that die from plastic pollution, the impact is significant.

One of the most vulnerable groups to plastic entanglement is marine mammals. Whales, dolphins, seals, and sea lions can become entangled in plastic debris, often resulting in severe injuries or death. In some cases, marine mammals may drown as they are unable to breathe underwater while trapped in plastic nets. A study on right whales found that 83% of the individuals photographed had been entangled at least once, with 59% experiencing multiple entanglements. Calves and juveniles are particularly susceptible, often suffering from more severe entanglements.

Sea turtles are another group highly vulnerable to plastic entanglement. All known species of sea turtles are affected by entanglement or ingestion of marine debris. Plastic bags can resemble jellyfish, a crucial part of their diet, leading to accidental ingestion or entanglement. Sea turtles can also become entangled in abandoned fishing nets and other plastic debris, causing injuries or death. In Brazil, 4.3% of stranded sea turtles died due to fishing-related activities, and in eastern Australia, 14% of mortality cases were attributed to fishing gear or shark netting.

In conclusion, plastic entanglement is a pressing issue that affects a wide range of marine life, including fish, marine mammals, seabirds, and turtles. It leads to injuries, restricts movement, and causes fatalities. The increasing presence of plastic in the oceans underscores the urgency of addressing this issue through reduced plastic consumption, responsible waste disposal, and collaborative efforts to prevent and respond to entanglement incidents.

Chemical contamination

While it is challenging to estimate the exact number of fish that die from chemical contamination each year, plastic pollution is a critical environmental issue that continues to grow in magnitude. Millions of tons of plastic waste enter the oceans annually, threatening marine life and ecosystems.

Plastic waste can directly kill marine animals through ingestion or entanglement. It is estimated that about 100,000 marine animals, including fish, die from plastic pollution each year. However, this number only accounts for the animals we find, and the actual figure is likely much higher. Additionally, plastic pollution can cause chemical contamination, which can harm the reproductive systems of marine animals.

One significant way plastics contribute to chemical contamination is by leaching toxic chemicals. Plastics are known to absorb and release toxic chemicals, such as PCBs, PBDEs, dioxins, chlorinated pesticides, and mercury. These chemicals can be absorbed by fish from the water, sediments, and their food sources. In contaminated areas, bottom-dwelling fish are especially likely to have high levels of these chemicals as they settle to the bottom, where the fish feed.

Mercury, a toxic metal, is of particular concern. It is present in the environment due to natural and human-related activities, with coal burning and mining being significant sources. When mercury enters water bodies, bacteria convert it to methylmercury, a more toxic form that can easily accumulate in fish and other organisms. This process, known as bioaccumulation or biomagnification, results in higher levels of mercury in larger, older fish and those higher on the food chain. The consumption of contaminated fish poses risks to human health, especially for women who are pregnant or planning to conceive, nursing mothers, and young children.

In addition to mercury, fish can absorb other chemical contaminants, such as per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), and dichloro-diphenyl-trichloroethane (DDT). These contaminants can persist in the environment for long periods and accumulate in fish tissues, including the skin, fat, internal organs, and muscle tissue. The accumulation of these chemicals in fish can lead to health risks for humans who consume them, with potential long-term effects, including developmental issues and, in some cases, cancer.

While plastic pollution is a significant contributor to chemical contamination, other sources also play a role. Harmful algal blooms (HABs) can produce toxins that affect aquatic ecosystems and human health when contaminated seafood is consumed. Additionally, chemical pollutants in water can come from factories, sewage treatment plants, chemical spills, runoff from farm fields and city streets, and atmospheric deposition from the land and air. These pollutants can be carried long distances and degrade water quality, leading to contaminated fish and adverse effects on ecosystems and human health.

Coral reef destruction

Coral reefs are among the most biologically diverse and valuable ecosystems on Earth. They are home to 25% of marine life and provide food, protection, and livelihoods for millions of people worldwide. However, coral reefs are in decline due to various local and global threats, and their very existence may be in jeopardy unless efforts to protect them are intensified.

One of the major threats to coral reefs is pollution. Land-based runoff and pollutant discharges from dredging, coastal development, agricultural activities, and sewage treatment plants can introduce high levels of nutrients, chemicals, insecticides, oil, and debris into the water. This promotes the rapid growth of algae and other organisms that smother corals and block the sunlight needed for photosynthesis. Trash and microplastics, such as plastic bags, bottles, and discarded fishing gear, can also snag on corals, entangle and kill reef organisms, and cause physical damage to coral structures.

Destructive fishing practices, including the use of dynamite or cyanide, and collecting coral for the aquarium and jewelry trade, also pose significant dangers to coral reefs. Blast fishing, for example, involves detonating explosives to startle fish, but this practice indiscriminately kills other species and severely damages coral colonies. Overfishing can alter food-web structures and reduce the number of grazing fish that keep corals clean of algal overgrowth. Additionally, anchors dropped from fishing vessels and abandoned fishing nets can break and destroy coral reefs.

Climate change and rising ocean temperatures also negatively impact coral reefs, increasing coral bleaching events and making them more susceptible to disease. To protect coral reefs, it is crucial to address these local and global threats, reduce pollution and destructive fishing practices, and mitigate the impacts of climate change.

Coral reefs are invaluable ecosystems that support a diverse range of marine life and provide essential goods and services to communities worldwide. It is imperative that we take urgent action to address the threats facing coral reefs and work towards their conservation and restoration.

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