Marine Mammals: Pollution's Devastating Impact

Marine mammals are suffering from various kinds of pollution, including plastic, chemical, and agricultural runoff. Plastic pollution, for example, kills an estimated 100,000 marine mammals each year, with 81 out of 123 species known to have ingested or become entangled in plastic. Chemical pollution, such as PCBs, pesticides, and metals, can cause a range of health issues, including hormonal and reproductive problems, nervous system damage, and cancers. The long life span and position at the top of the food chain of marine mammals mean that they are particularly vulnerable to the accumulation of toxic chemicals. Additionally, climate change poses a significant threat to marine mammals, with rising sea levels, ocean warming, and acidification affecting vital marine species.

Plastic pollution

Entanglement in plastic-based fishing gear, such as nets, ropes, and pots, is another significant threat to marine mammals. Large items of plastic can capture and entangle marine mammals, preventing them from escaping and leading to injuries, starvation, and increased vulnerability to predators. This issue is particularly prevalent with "ghost gear," abandoned or lost fishing equipment that continues to entangle marine life. It is estimated that 300,000 whales, dolphins, and porpoises die each year from entanglement in ghost gear.

The impact of plastic pollution on marine mammals is devastating and widespread, with 81 out of 123 marine mammal species known to have been affected. It is essential to address this issue through measures such as reducing single-use plastic, improving waste management practices, and participating in beach clean-up efforts to protect marine life and ecosystems.

Chemical pollution

Marine mammals are facing significant health risks from chemical pollution, which is having a detrimental impact on their survival. As top predators, these mammals accumulate high levels of toxins in their bodies, particularly in their fatty tissues and breast milk.

One of the major issues is the presence of Persistent Organic Pollutants (POPs) in the ocean. POPs are industrial compounds that resist environmental breakdown and can persist for decades or even centuries. They are toxic to marine life and have been linked to various health issues in marine mammals, including reproductive problems, endocrine system damage, and growth and development issues. PCBs, for example, have been shown to make whales more vulnerable to infectious diseases and have been found to impair normal growth and development. POPs are also estrogen imitators, causing low sperm counts and impaired reproduction. PBDEs, a type of flame retardant, are another significant concern, with concentrations doubling every four years in marine mammals.

Pesticides and herbicides are also a major source of chemical pollution, with agricultural runoff delivering these chemicals into the ocean. Beluga whales, for instance, have been found to be so saturated with pesticides and herbicides that their carcasses must be handled as toxic waste. These chemicals have been linked to various health issues, including cancer. Metals, or trace metals, are another common pollutant, making up 30% of studied pollutants.

In addition to the direct impact on marine mammals, chemical pollution also affects their habitat and food sources. Toxins accumulate in plankton, which are consumed by small fish, which are then eaten by larger fish, and eventually by marine mammals, leading to a concentration of toxins in their bodies. This process, known as biomagnification or bioamplification, results in higher concentrations of toxins in organisms higher up the food chain.

The presence of microplastics in the ocean further exacerbates the problem, as they can carry and release toxic chemicals into the water, leading to physical and health issues in marine mammals. Microplastics have been linked to hormonal and reproductive problems, nervous system and kidney damage, digestive and heart issues, and an increased risk of cancer and parasitic diseases.

Climate change

One of the most vulnerable groups of marine mammals are the cetaceans, such as whales and dolphins, which are particularly affected by ocean warming due to the melting of polar ice. The loss of sea ice also impacts the hunting abilities of larger marine predators, as their prey's range shifts. For example, the North Atlantic right whale and the humpback whale are two species that have been documented to be impacted by climate change.

The vulnerability of marine mammals to climate change varies across regions, with the North Pacific, Greenland Sea, and Barents Sea identified as hotspots. These regions face threats from human activities, such as marine traffic, pollution, and offshore oil and gas development, which synergize with the effects of climate change, increasing the overall vulnerability of marine mammals.

Additionally, climate change has been associated with the decline of several marine species, including the smallest corals to the largest whales. The combination of climate change and pollution poses a significant threat to marine mammals, and urgent steps must be taken to protect the oceans and the species that depend on them.

Agricultural runoff

The impact of agricultural runoff on marine environments and, consequently, on marine mammals, is significant. Firstly, it causes eutrophication, where the excess nutrients from fertilizers lead to harmful algal blooms. These blooms deplete oxygen levels in the water, creating 'dead zones' where marine life, including mammals, cannot survive. For example, the Gulf of Mexico has a significant dead zone due to agricultural runoff from the Mississippi River, severely affecting local fisheries and marine biodiversity.

Secondly, the toxins produced by certain algal blooms can accumulate in the food chain, affecting not just fish but also marine mammals that consume contaminated prey. These toxins can lead to health issues such as cancer, reproductive problems, endocrine system damage, and growth and development issues in marine mammals. Beluga whales in the St. Lawrence Seaway and Estuary have been found to be highly contaminated with agricultural runoff-delivered chemicals, resulting in various health issues.

Additionally, agricultural runoff can carry pesticides, herbicides, and phosphorus into marine ecosystems. These chemicals can directly harm marine mammals, as seen in the case of the St. Lawrence Estuary beluga whales, which suffer from polycyclic aromatic hydrocarbons (PAHs) that are linked to cancer. Furthermore, runoff from intensive livestock farming can introduce bacteria, such as E. coli, and excess manure into water bodies, further degrading water quality and threatening the health of marine mammals.

The impact of agricultural runoff on marine mammals highlights the importance of sustainable farming practices. Implementing soil and water conservation methods, such as contour strip cropping, can help reduce erosion and minimize the runoff of pollutants into marine environments. By addressing agricultural runoff, we can mitigate its harmful effects on marine ecosystems and the mammals that depend on them.

Persistent organic pollutants (POPs)

POPs include industrial chemicals such as polychlorinated biphenyls (PCBs), which were widely used in electrical equipment, and unintentional by-products formed during industrial processes, degradation, or combustion (such as dioxins and furans). They resist environmental breakdown via biological, chemical, and photolytic processes, with some taking as long as a century to degrade to safe levels.

The health risks posed by POPs are significant. They have been linked to reproductive impairments, making them a potential risk for men and women of child-bearing age. In marine mammals, a 2007 study found that PCB contamination in Pacific Northwest orcas will last until at least 2030 for a northern population of 230 animals, and the southern population of 85 may face risks until 2063. PCBs make whales more vulnerable to infectious diseases and impede normal growth and development. POPs also impair reproduction by acting as estrogen imitators and causing low sperm counts.

International cooperation is necessary to address the risks posed by POPs. The Stockholm Convention on Persistent Organic Pollutants, which entered into force in 2004, is a global treaty that aims to safeguard human health and the environment from highly harmful chemicals that persist in the environment. The Aarhus Protocol also regulates POPs worldwide. The United States, through the Environmental Protection Agency (EPA), has shown commitment to addressing POPs in cooperation with other countries. Additionally, the Arctic Council Action Plan has launched projects to reduce the use and release of POPs within the Arctic nations, and the European Union has implemented the POPs Regulation to control and restrict the production, use, and release of POPs.

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