The Impact Of Multiple Pollutions On Killer Whales

Killer whales, or orcas, are facing an existential threat from human-caused marine pollution. As top predators, killer whales are particularly vulnerable to pollutants that accumulate in the fatty tissues of animals as they move up the food chain. These pollutants, known as Persistent Organic Pollutants (POPs), include chlorinated hydrocarbons, flame retardants, and polychlorinated biphenyls (PCBs). High levels of these contaminants have been found in killer whales, leading to various health issues such as reduced immunity, hormonal imbalances, reproductive issues, and even cancer. The impact of marine pollution on killer whales is a growing concern, and while there are still many unanswered questions, improving science and technology are helping to enhance our understanding of the issue.

Oil spills

The impact of oil spills on killer whales was first observed after the Exxon Valdez disaster of 1989, which released 11 million gallons of oil into Alaska's Prince William Sound. Before the disaster, it was believed that marine mammals would be able to detect and avoid oil in the event of a spill. However, this proved to be untrue, as the Chugach transients, a pod of 22 killer whales, lost nine of their members immediately after the Exxon Valdez spill, presumed dead from ingesting or inhaling oil. Another six went missing, and the pod has failed to reproduce in the three decades since.

The Southern Resident Killer Whale (SRKW) population, which faces other threats such as food depletion, high toxic loads, and vessel traffic noise, is particularly vulnerable to oil spills. An oil spill within their critical habitat would likely lead to a major decline or even an irreversible path to extinction.

When oil spills occur, "hazing" methods are sometimes used to deter whales from the area of the spill. These include acoustic deterrent devices, pre-recorded killer whale calls, Oikomi pipes, boat traffic, helicopters, and fire hoses. However, these hazing and monitoring activities are often the only mitigation measures possible, as capturing and rehabilitating killer whales is improbable.

To protect killer whales from oil spills, it is essential to prevent spills from happening in the first place. Additionally, programs like the Spill Prevention, Preparedness, and Response Program work to decrease the effect of potential oil spills on endangered Southern Resident Killer Whales.

Marine debris

The impact of marine debris on killer whales is not limited to physical entanglement. Plastic pollution, in particular, poses a severe threat to these majestic creatures. Plastic waste, including bags, ropes, and even car parts, can be ingested by whales, mistaking it for potential food or prey. This ingestion of plastic can cause physical damage to their digestive systems, leading to tears or punctures in the stomach lining. Additionally, the presence of plastic in their stomachs can disrupt their feeding patterns, resulting in malnutrition.

Moreover, ocean plastic serves as an ideal surface for persistent organic pollutants (POPs) such as DDT to adhere to. These pollutants can enter a whale's body when plastic is ingested and accumulate in their blubber through bioaccumulation. As top predators, killer whales are highly susceptible to accumulating high levels of these toxic chemicals, which can have detrimental effects on their health and reproduction.

To address the issue of marine debris and its impact on killer whales, it is essential to reduce and properly recycle plastic waste. Reusable alternatives, such as water bottles and shopping bags, can play a significant role in decreasing plastic pollution in our oceans. Additionally, initiatives like beach cleanups and the development of new fishing technologies to prevent entanglement are crucial steps towards mitigating the harmful effects of marine debris on killer whales.

The understanding of how killer whales interact with marine debris and pollutants is constantly evolving, and ongoing research will help inform conservation efforts to protect these magnificent creatures and their ecosystems.

Industrial pollutants

PCBs accumulate in the blubber of killer whales, which are apex predators in the marine food chain. The process of biomagnification causes PCBs to work their way up the food chain, resulting in higher concentrations in the blubber of killer whales that consume marine mammals. Studies have found that killer whales with high PCB loads are at risk of health issues such as immunosuppression, cancer, nervous system dysfunction, endocrine disruption, and reproductive issues. These health risks are particularly pronounced in female killer whales, where PCB exposure has been linked to reproductive failure.

The impact of PCBs on killer whale populations is a global concern, with populations in highly polluted seas around Japan, Brazil, the UK, and the northeast Pacific facing potential collapse. While PCB production has been largely discontinued, their persistence in the environment and the changing diets of predators continue to pose challenges. Efforts to monitor and mitigate the presence of PCBs in the environment are ongoing, but the long-term impact of these chemicals on killer whale populations remains a significant threat.

In addition to PCBs, other industrial pollutants such as hexachlorobenzene (HCB), polybrominated diphenyl ethers (PBDEs), and dichlorodiphenyltrichloroethane (DDT) also pose risks to killer whales. These pollutants are introduced through various industrial products and have been linked to health issues in killer whales, including immunosuppression, cancer, and reproductive impairments. The complex food webs in northern oceans, particularly around Europe and North America, where PCB usage was prevalent, further contribute to the exposure of killer whales to these industrial pollutants.

Acoustic pollution

Firstly, there are short, extremely loud noises that can physically harm whales. Sources of such noise include sonar and seismic surveys. The impact of mid-frequency military sonar on a whale's hearing can be equivalent to that of a jet engine at takeoff on the ears of a human located only three feet away. This intense noise disturbs whales, leading to their fatal rapid ascent and decompression sickness, also known as "the bends". For example, in September 2002, 14 beaked whales washed ashore in the Canary Islands bleeding from their ears and eventually died, which many experts suspect was caused by a fear response to naval sonar testing.

Secondly, constant and ever-present noise, primarily from shipping, fills the ocean. This noise reduces whales' ability to use sound to perform essential life functions such as foraging, finding a mate, communicating, and evading predators. This phenomenon is called acoustic masking, and while it doesn't directly harm or kill whales, it may reduce their chances of survival over time. Acoustic masking is particularly problematic for baleen whales, as the frequency of the sounds that ships produce overlaps with the frequency baleen whales rely on.

The COVID-19 pandemic provided a unique opportunity to study acoustic masking, as noise levels in many ocean areas decreased due to reduced boat traffic and human activity. During this time, research groups collected data on how whales' behaviour changed in a quieter ocean.

While there is some dispute among marine biologists regarding the relationship between naval sonar testing and decompression sickness in whales, the marine biology community agrees that human-generated noise pollution significantly disrupts marine life. As our understanding of the impact of acoustic pollution on whales continues to evolve, further initiatives and research are needed to broaden our knowledge and implement effective protective measures.

Chemical pollution

One of the most well-known groups of POPs is polychlorinated biphenyls (PCBs), which were extensively used in building materials for decades. Despite a global ban on PCBs in 2004, they continue to seep into the environment due to improper disposal of products and the presence of contaminated material worldwide. PCBs accumulate in the food chain, with the highest concentrations found in top predators like killer whales. These toxins are stored in the fatty tissue (blubber) of whales, and their levels increase over time as they consume more contaminated prey.

The consequences of PCB exposure are severe. They cause sterility, reproductive issues, hormonal imbalances, and immune system suppression, making whales more susceptible to diseases and increasing their mortality rate. Additionally, high PCB levels can lead to cancer, nervous system dysfunction, skeletal abnormalities, endocrine disruption, and birth defects. The impact of PCBs is particularly pronounced in female killer whales, as they pass on a significant portion of their PCB burden to their first-born calves, which sometimes proves fatal.

Another type of POP that affects killer whales is dichlorodiphenyltrichloroethane (DDT), an insecticide. While it has been banned for decades, DDT still enters the marine environment through landfill sites and industrial wastewaters. Other POPs of concern include polybrominated diphenyl esters (PBDEs), dioxins, and organochlorine pesticides such as aldrin, dieldrin, and endrin.

To address the global issue of chemical pollution, the Stockholm Convention was signed in 2001 by the UK and 90 other countries. The treaty aims to reduce or eliminate the production, use, and release of POPs, and it includes a process to identify and address additional POPs of concern. As of 2023, 38 chemical substances have been targeted for elimination or reduction.

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