Whale Health Crisis: Understanding The Impact Of Pollution

Marine pollution is a serious threat to whales and other sea mammals. Whether it is oil spills, marine debris, or industrial pollutants such as PCBs, these contaminants can cause harm and have long-term impacts on whales and their environment. Noise pollution, caused by human activities such as ship traffic, oil and gas exploration, and military exercises, can also lead to whale strandings and even death. Plastic pollution, in particular, has devastating effects, with whales ingesting plastic bags and other plastic items, causing internal injuries and death. Additionally, whales can become entangled in plastic fishing nets and ropes, leading to slow and painful deaths. Addressing these issues requires global efforts to reduce plastic pollution and protect whale habitats.

Plastic ingestion

Whales may ingest plastic by mistaking it for prey. Deep-diving toothed whales, for example, rely on echolocation to find food in the darkness, and plastic debris can sound remarkably similar to their prey, such as squid. In addition, plastic bags floating in the water may visually resemble squid or jellyfish to whales and other marine species.

The impact of plastic ingestion on whales can be devastating. It can cause stomach tissue damage, infection, suffocation, and malnutrition, leading to starvation. A stranded sperm whale in Indonesia was found to have ingested over 13 pounds of plastic, including bags and flip-flops. Another stranded whale had ingested 135 items, mostly plastic bags, which is the highest number recorded for this species.

Even microplastics, tiny plastic particles less than 5mm in size, pose a significant threat to whales. These microplastics can break down into invisible toxic chemical compounds that work their way up the marine food web through biomagnification and bioaccumulation. These compounds can disrupt the development and reproductive health of whales and other marine animals.

The presence of plastic in the ocean is a pressing issue that requires global attention and action. Reducing plastic consumption, especially single-use plastics, is a critical step in mitigating the impact of plastic pollution on whales and other marine life.

Entanglement in plastic

Whales can become entangled in plastic in the ocean, usually in the form of fishing nets and ropes. This can cause surface injuries, but the main danger comes from the extreme energy exerted when trying to move with the burden of debris dragging behind them. This can be lethal.

Entanglement is considered a primary cause of human-induced mortality in many whale species, especially right whales, humpback whales, and gray whales. Smaller whales may drown immediately if the gear is large or heavy, while larger whales are generally not at immediate risk of drowning but face the risk of exhaustion and infection.

Even if whales do not drown, entanglement can hinder their movement, foraging abilities, and ability to avoid predators. It can also increase the risk of being struck by ships.

One of the most damaging types of marine plastic pollution is abandoned, lost, or discarded fishing gear, known as "ghost gear." This gear continues to trap and kill marine life, including whales, even after it is no longer in use.

The problem of entanglement is not limited to whales, but also affects other marine mammals and sea turtles.

Noise pollution

However, human activity has filled the ocean with sound, and because these sounds travel so far, there is nowhere for whales to hide. There are two main ways in which noise pollution impacts whales:

Firstly, short and extremely loud noises can physically harm whales, causing them to go deaf and strand on coastlines. Sources of such noise include sonar and seismic surveys. For example, military sonar can reach volumes of more than 200 decibels, while seismic air guns can reach up to 250 decibels. At this level, the force of the vibrations is enough to kill zooplankton, and while larger animals like whales are not killed directly by the sound waves, they have been linked to whale deaths caused by strandings and decompression sickness.

Secondly, there are noises that are quieter but constant and ever-present, mostly from shipping. This noise fills the ocean, reducing whales' ability to use sound to perform essential life functions such as foraging, finding a mate, communicating, and evading predators. This is known as acoustic masking, and while it doesn't directly harm or kill whales, it could be reducing 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. It is also a silent, insidious problem as it is difficult to quantify the number of whales that have been killed or affected by acoustic masking.

Overall, noise pollution is a significant threat to whales, impacting their behaviour, health, and survival.

Oil spills

During an oil spill, "hazing" methods are used to deter whales from entering the contaminated area. These methods include acoustic deterrent devices, pre-recorded whale calls, Oikomi pipes, boat traffic, helicopters, and fire hoses. However, these techniques are not always effective, and the success of deterring whales depends on the degree to which they are attracted to the area.

If a whale is found with oil on its skin, experienced veterinarians and wildlife rehabilitation specialists are called in to assist. The immediate concerns are skin irritation from oil contact and inhalation of oil vapors, which can lead to pneumonia and other complications. The surface contamination would be cleaned with a mild detergent, and the whale might need to be moved to a location where it can recover and be monitored.

Research by Craig Matkin (2008) suggests that killer whale populations can suffer population-level impacts when exposed to oil. For example, a pod of resident killer whales in Prince William Sound, Alaska, experienced a steady and significant decline in numbers following the Exxon Valdez oil spill in 1989. This provided strong indirect evidence that oil spills can impact whale populations, even if oil is not directly observed on the whales.

Industrial pollutants

PCBs accumulate in the food chain, with the highest concentrations found in top predators like whales. They are stored primarily in the fatty tissue (blubber) of whales, and the levels increase over time as they consume more contaminated fish. When whales undergo stressful events, such as food scarcity, they break down their blubber for energy, releasing a flood of toxic PCBs into their bodies. This release of toxins can have devastating effects on their health, including sterility and even death.

Whales are particularly vulnerable to the toxic effects of PCBs due to their inability to produce certain enzymes that help break down these chemicals. As a result, the PCB burden in whales tends to increase until they reach sexual maturity. While female whales transfer a significant portion of their PCB burden to their first-born calves, male whales continue to accumulate PCBs from their food sources. This transfer of toxins to their offspring can be fatal, as seen in the case of Lulu, an orca that stranded on the Isle of Tiree in Scotland with PCB levels 20 times the safe limit.

In addition to PCBs, whales are also affected by other industrial pollutants such as oil spills and noise pollution. Oil spills can directly impact whales by contaminating their prey, inhalation of fumes, or ingestion of oil. It also kills off smaller creatures like krill, which are a vital food source for whales. Noise pollution, such as that generated by oil exploration and military exercises, can disrupt the normal behaviour of whales, drive them away from essential habitats, and even cause injuries or death.

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