Water Pollution's Deadliest Victims: Animals Commonly Killed

Water pollution is a pressing global issue that poses a grave threat to numerous ecosystems and their inhabitants. Among the various forms of water pollution, plastic waste stands out as a significant concern, with an estimated 9.5 million metric tons of plastic ending up in the oceans annually. This plastic pollution has devastating consequences for marine life, leading to the deaths of approximately 100,000 marine mammals and over a million seabirds each year. The impact of plastic pollution on marine animals is twofold: ingestion of plastic, which can cause internal damage and poisoning, and entanglement in plastic debris, which can restrict movement, cause injuries, and lead to drowning. Aside from plastic, other sources of water pollution, such as oil spills, toxic chemicals, and nutrient runoff, also contribute to the decline of aquatic life. These pollutants affect a wide range of creatures, from microscopic organisms to large marine mammals, and the repercussions extend throughout the food chain, impacting invertebrates, crustaceans, amphibians, and even terrestrial species reliant on aquatic ecosystems.

Abandoned fishing gear entangles and kills hundreds of thousands of cetaceans

Water pollution is a significant threat to marine life, with an estimated 100,000 marine mammals killed annually. One of the primary ways pollution harms these creatures is through entanglement in plastic-based fishing gear. Abandoned fishing gear, also known as "ghost gear," poses a severe and growing problem for marine conservation and animal welfare.

Cetaceans, which include whales, dolphins, and porpoises, are particularly vulnerable to entanglement in abandoned fishing gear. It is estimated that over 300,000 whales and dolphins die each year due to entanglement in fishing gear and bycatch, with many more entangled in marine debris. Small cetaceans, such as the Maui dolphin in New Zealand and the Vaquita porpoise in the Gulf of California, are facing extinction due to net entanglement.

The impact of entanglement on cetaceans can be devastating. It can lead to drowning, as entangled animals cannot reach the surface to breathe. Heavy ropes can also cause lacerations and infections, and towing heavy fishing gear hinders their ability to feed, leading to starvation. Even those that escape or are freed may still succumb to their injuries or infections later on.

The issue of abandoned fishing gear is not limited to a specific location but is a global concern. It affects not only cetaceans but also a wide range of marine creatures. For example, all seven sea turtle species are affected by plastic pollution, including entanglement and ingestion of plastic.

Addressing the problem of abandoned fishing gear requires a multi-faceted approach. On the one hand, there is a need for improved gear that minimizes the risk of entanglement. The field of ropeless fishing, for instance, offers promising solutions for protecting individual animals and their species. On the other hand, raising public awareness and reducing the demand for seafood can help decrease the amount of deadly fishing gear in our oceans.

Plastic ingestion causes physical changes, impairs movement, inhibits digestion, and kills fish

Marine animals, such as seabirds, sea turtles, and marine mammals, are among the most common victims of water pollution, with plastic pollution being a significant contributor to their deaths. Plastic ingestion by fish has been observed since the 1970s, and it continues to be a pressing issue. Plastic ingestion causes physical changes, impairs movement, inhibits digestion, and kills fish, as detailed below.

Physical Changes

Plastic ingestion has been linked to physical changes in fish, including tissue damage and oxidative stress. Microplastics, in particular, can cause neurobehavioral toxicity and affect the brain-gut-microbiota axis. The accumulation of plastic in the digestive tract can lead to internal ulcerations and partial blockages, impacting the fish's health and survival.

Impaired Movement

Studies have shown that fish that ingest plastic exhibit slower movement and hunting abilities compared to those that do not. This impairment in movement can make it difficult for fish to escape predators or capture prey, further endangering their survival.

Inhibited Digestion

Plastic ingestion has also been found to inhibit digestion in fish. Research on zebrafish (Danio rerio) revealed that while small microplastic spheres moved through the gastrointestinal tract and were excreted, there were rare occasions where microplastic particles were taken up by epithelial cells. Ingestion of plastic can lead to a reduced ability to control buoyancy, longer gastric evacuation times, and lower energy accumulation, resulting in energy depletion and potential starvation.

Mortality

The ingestion of plastic and the associated accumulation of pollutants can have fatal consequences for fish. Studies have shown that exposure to microplastics, alone or in combination with other pollutants, can induce liver toxicity and pathology, leading to mortality in fish. The transfer of hazardous chemicals, such as polycyclic aromatic hydrocarbons and plastics, poses a significant risk to fish health and can ultimately lead to their demise.

Seabirds mistake plastic for food, leading to intestinal blockages and death

Seabirds are particularly vulnerable to plastic pollution in the ocean. They often mistake plastic for food, which can lead to intestinal blockages and, ultimately, death.

Seabirds, such as pelicans, albatrosses, and seagulls, are attracted to the bright colours of plastic debris, mistaking it for fish eggs or other prey. As a result, they ingest large pieces of plastic that accumulate in their gastrointestinal tracts and stomachs. This leads to bowel obstructions and intestinal perforations, causing severe health issues and even death.

The ingestion of plastic also reduces the birds' stomach capacity, as the accumulated plastic takes up space, limiting their ability to consume sufficient food. This leads to starvation and deprives them of essential nutrients necessary for survival.

Furthermore, microplastics and toxic chemicals associated with plastic can be ingested by shellfish and plankton, which are then consumed by seabirds. These toxins can have detrimental effects on the birds' health, growth, development, and reproductive capabilities.

The issue of seabirds ingesting plastic is widespread, with studies estimating that up to 90% of seabirds have plastic in their guts. The problem is expected to worsen, with predictions suggesting that by 2050, 99% of seabirds will have plastic in their systems.

The high mortality rate among seabirds due to plastic ingestion highlights the urgent need to address plastic pollution in our oceans. It is crucial to reduce plastic waste, dispose of plastic responsibly, and transition to more sustainable alternatives to protect these vulnerable creatures.

Coral reefs are damaged by plastic, oil, trash, and fishing nets, threatening marine life

Coral reefs are incredibly diverse ecosystems that are home to a wide variety of marine life. However, these delicate environments are under constant threat from human activities, with plastic, oil, trash, and fishing nets being some of the most significant contributors to their degradation.

Plastic pollution is a pervasive issue that has detrimental effects on coral reefs. A four-year study involving dives on 159 reefs in the Pacific revealed heavy plastic contamination in Australia, Thailand, Indonesia, and Myanmar. Plastic clings to coral, particularly branching coral, and facilitates the spread of disease. The presence of plastic increases the likelihood of disease in corals from 4% to a staggering 89%. It abrades and tears the coral, creating openings that allow pathogens and infections to invade. The plastic itself may also be a source of harmful bacteria and microorganisms that directly harm the coral.

Oil spills are another significant threat to coral reefs. When oil comes into contact with corals, it can impede their reproduction, growth, behavior, and development. Even small amounts of oil exposure over an extended period can be just as detrimental as large amounts of oil for a brief time. Oil spills can occur due to grounded ships or leaks from offshore sources, and they can have devastating consequences for the entire reef ecosystem. The impact of oil spills extends beyond the coral itself, affecting the many species of fish, crabs, and marine invertebrates that rely on the reef.

Trash and debris, including building materials, aluminum cans, tires, disposable diapers, and plastic waste, also pose a significant threat to coral reefs. This debris can become entangled with the coral, causing physical damage and leaving scars on the reef. Additionally, lost fishing gear, such as nets and traps, can ensnare hard corals, breaking or scratching them and leading to fragmentation and dislodgement. The impact of these threats is widespread, with trash and fishing gear found in remote locations like the Northwestern Hawaiian Islands and the Marshall Islands.

The consequences of plastic, oil, trash, and fishing net pollution are dire for coral reefs and the marine life they support. The degradation of coral reefs leads to a loss of habitat and resources for numerous species, threatening their survival. Additionally, the pollutants and pathogens associated with these forms of pollution can directly harm and kill marine animals. Efforts to address and mitigate these threats are crucial for the preservation of coral reefs and the diverse marine ecosystems they support.

Water pollution causes harmful algal blooms, killing seagrass beds and marine life

Water pollution is a pressing issue that poses a severe threat to marine life and ecosystems. One of the most detrimental consequences of water pollution is the occurrence of harmful algal blooms (HABs), which have far-reaching impacts. HABs occur when colonies of algae, simple plants that live in water, grow out of control and produce toxic or harmful effects. These blooms can be unsightly, foul-smelling, and even toxic, impacting both the environment and human health.

HABs are a growing concern in coastal areas and freshwater ecosystems, including rivers, lakes, ponds, and reservoirs. They are caused by increased nutrient pollution, primarily from excess nitrogen and phosphorus, which act as fertilizers and promote excessive algae growth. This nutrient pollution can come from sources such as urban and rural runoff, agriculture, and natural phenomena like sluggish water circulation and high water temperatures.

As HABs grow thicker, they absorb more sunlight, leading to warmer water and further algal growth, creating a feedback loop. This process results in the formation of thick, green muck that blocks sunlight from reaching underwater plants, disrupting the growth of seagrass beds and other aquatic vegetation. Additionally, when the algae eventually die, their decomposition consumes oxygen, creating "dead zones" where aquatic life cannot survive due to low oxygen levels.

The impact of HABs extends beyond just the plant life. They can directly kill fish, marine mammals, birds, and even humans in extreme cases. For example, golden algae blooms in Texas and New Mexico have caused significant fish kills, resulting in the loss of millions of fish and economic repercussions. HABs also affect the "health" of economies, particularly in coastal communities that rely on fishing and tourism.

Apart from HABs, water pollution also directly harms marine animals through plastic pollution and abandoned fishing gear. Marine mammals, such as whales, dolphins, and seals, often mistake plastic bags for prey, leading to fatal ingestion. Additionally, entanglement in plastic-based fishing gear and abandoned nets is a significant cause of death for various marine creatures, including dolphins and turtles.

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