Pollution's Impact On Killer Whales: Understanding The Danger

Killer whales are one of the most widespread mammals on Earth, but pollution is threatening their future. As top predators, killer whales are extremely vulnerable to chemical pollution, such as PCBs, which accumulate in their fatty tissue (blubber) and are passed on to their calves through their milk. This contamination has severe impacts on their reproductive organs, immune systems, and overall health, with some populations, such as those around the UK, the Strait of Gibraltar, Brazil, Japan, and California, facing an uncertain future. Noise pollution from human activities, such as oil exploration and military exercises, also poses a significant threat to killer whales, disrupting their natural behaviour and survival. With plastic pollution and other contaminants choking our oceans, the survival of killer whales and many other marine species hangs in the balance.

How does plastic pollution affect killer whales?

Plastic pollution poses a significant threat to killer whales, also known as orcas, by causing ingestion, entanglement, and chemical contamination.

Ingestion of plastic waste is a critical issue affecting killer whales. They often mistake plastic bags and other plastic debris for their prey, such as squid. This leads to the consumption of large quantities of plastic, resulting in internal injuries and even death. Microplastics, tiny plastic particles, are also ingested by killer whales and can have detrimental effects on their health. These microplastics can break down into toxic chemical compounds, disrupting the development and reproductive health of killer whales.

Entanglement in plastic-based fishing gear, often referred to as "ghost gear," is another major issue. Abandoned, lost, or discarded fishing nets and ropes ensnare killer whales, leading to slow and painful deaths through suffocation, starvation, or exhaustion. The impact of entanglement goes beyond the immediate physical injuries, as entangled killer whales experience extreme energy exertion when trying to move with the burden of debris dragging behind them.

Additionally, plastic pollution acts as a surface for persistent organic pollutants (POPs) to cling to. When killer whales ingest plastic, these pollutants enter their bodies and accumulate in their blubber through bioaccumulation. As top predators, killer whales are highly vulnerable to the toxic effects of these chemicals, which include reproductive issues and a suppressed immune system.

The impact of plastic pollution on killer whales is not fully understood yet, but it is clear that it poses a significant threat to their health and survival. Addressing this issue requires a global effort to reduce plastic pollution and implement sustainable practices to protect these majestic creatures and the oceans they inhabit.

How does chemical pollution affect killer whales?

Killer whales are in grave danger due to persistent chemical pollution in the environment. A recent study suggests that more than half of the different orca groups worldwide may not survive. Populations around the UK, the Strait of Gibraltar, Brazil, Japan, and California are especially at risk. The primary issue is polychlorinated biphenyls (PCBs), highly toxic chemical compounds that were once widely used in plastics, paints, electrical equipment, and sealants. Despite being banned decades ago, PCBs have accumulated in the environment and continue to leach into the ocean.

As top predators, killer whales absorb all the PCB pollution accumulated by their various prey in the food chain, from fish to seals and sharks. This accumulation of PCBs has severe consequences for their health and reproductive success. The chemicals stunt the ovaries of female orcas, limiting their ability to produce calves, and they also suppress the immune system. Additionally, the high levels of PCBs in a mother's milk are passed on to her offspring during lactation, exposing newborn calves to very high doses of these toxic chemicals.

The impact of PCBs on killer whale populations is evident in the decline of certain groups. For example, the killer whales off the west coast of Scotland have not produced a calf in over 20 years, and their numbers have dwindled to just eight individuals. The outlook for orcas in polluted seas is grim, with predictions of significant population declines in the next 30-50 years.

The persistence of PCBs in the environment poses a significant challenge. While some countries, like the US, have made progress in reducing PCB levels entering the ocean, urgent action is needed in other regions, such as Europe. Improper disposal of PCB-containing equipment and contaminated building materials contributes to the ongoing leakage of these toxic chemicals into the ocean and other water bodies.

While there is little that can be done to recover PCBs once they have reached the ocean, addressing parallel issues such as noise pollution, habitat changes, and prey availability could help reduce the overall stress on orca populations. The situation underscores the need for a coordinated global response to tackle plastic pollution and ensure the safe disposal of PCBs to protect marine life and the health of our oceans.

How does noise pollution affect killer whales?

Noise pollution is a serious threat to whales, including orcas. In fact, it can even be deadly.

Orcas, also known as killer whales, communicate through touch, movement, and, most importantly, sound. They use sound to navigate, find food, and socialise. They are highly collaborative and communicate constantly with one another, so noise pollution can be incredibly disruptive to their daily lives.

Boat noise, for example, can overpower whale calls, making it difficult for them to communicate with one another, find mates, or locate prey. It can also scare away their food sources, such as schools of herring. This is particularly problematic for orcas, as they have specific hunting grounds and techniques that are passed down through generations. Noise pollution can also cause whales to swim out of their usual living areas, sometimes dangerously close to coastlines, and interrupt their normal behaviour.

In addition to boat noise, loud underwater seismic surveys used to locate oil and gas, military exercises, and industrial shipping traffic can all contribute to noise pollution that affects orcas. These noises can be louder to marine life than fireworks from three feet away and can be heard underwater for months.

The impact of noise pollution on orcas is not yet fully understood, but it is clear that it has the potential to cause significant harm. It can interfere with their ability to communicate, navigate, and find food, and may even contribute to hearing loss and strandings.

To protect orcas and other whale species from the detrimental effects of noise pollution, measures such as implementing speed limits and restricted zones for vessels, as well as developing acoustic warning systems, are being explored.

How does marine debris affect killer whales?

Marine debris is a serious threat to killer whales and other marine mammals. One of the most common forms of marine debris is derelict fishing gear, which often traps marine life long after it is no longer in use. Whales can become entangled in plastic, usually in the form of fishing nets and ropes, which can cause surface injuries and lead to extreme energy exertion as they try to move with the burden of debris dragging behind them. This can sometimes be lethal.

Toothed whales often mistake plastic for potential food or prey, and baleen whales can unknowingly ingest plastic debris when feeding. This ingestion of plastic can result in internal injuries and even death. A recent study found that flexible plastic, such as plastic bags and packaging, is responsible for the largest proportion of deaths from debris due to gastric obstructions. In 2018, a sperm whale stranded in Indonesia was found to have ingested over 13 pounds of plastic, including bags and flip-flops. Microplastics, plastic pieces of 5mm or less, are also a concern for baleen whales, as they can end up ingesting these tiny plastic particles along with their prey while filter feeding.

Marine plastic has been found to be a surface for chemicals known as persistent organic pollutants (POPs), which can enter a whale's body when ingested and are sometimes stored within their blubber. Through bioaccumulation, species at the top of the food chain, like killer whales, are likely to accumulate the highest amounts of these toxic chemicals.

In addition to the direct impacts on killer whales, marine debris can also affect their food supply. For example, oil spills can kill off smaller animals, such as krill, that are a source of food for whales. Noise pollution from human activities such as oil exploration and military exercises can also disrupt the normal behaviour of killer whales, driving them away from areas important for their survival and potentially causing injuries or deaths.

How does oil pollution affect killer whales?

Oil spills are toxic and can cause both acute and chronic exposure in killer whales. They can cause external problems, such as skin or eye irritation or ulceration, and internal problems when oil is ingested or inhaled.

Oil spills can also kill off smaller animals, such as krill, that are a food source for killer whales. This means that even if the whales do not ingest oil directly, they can be affected by it through their food sources.

Research has shown that toxins from oil spills are found in both Southern Resident and Bigg's killer whales, indicating a direct impact of human activities on marine life. These toxins, known as polycyclic aromatic hydrocarbons (PAHs), are found in coal, oil, and gasoline and enter the ocean through various sources, including oil spills, burning coal, and forest fires. PAHs have been shown to transfer from mother orcas to their fetuses, highlighting the pervasiveness of this pollution.

The impact of oil spills on killer whale populations can be severe and long-lasting. For example, a pod of resident killer whales in Prince William Sound, Alaska, experienced a significant and steady decline in numbers following the Exxon Valdez oil spill in 1989. This pod has still not reached its pre-spill numbers, demonstrating the lasting effects of oil pollution on killer whale populations.

To protect killer whales during oil spills, various "hazing" methods are employed to deter them from the area. These include acoustic deterrent devices, pre-recorded killer whale calls, Oikomi pipes, boat traffic, helicopters, and fire hoses. Additionally, programs such as the Vessel of Opportunity (VOO) aim to recruit and train whale-watching vessel owners to safely keep orcas from entering areas with major oil spills.

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