Dolphin Danger: Understanding Pollution's Impact

Dolphins are beloved creatures, adored for their playful, friendly, intelligent, and social nature. However, pollution poses a significant threat to their survival. From oil spills to plastic ingestion, noise pollution to chemical contaminants, human activities are having a detrimental impact on dolphin populations. Dolphins, as top predators, are particularly vulnerable to the effects of pollution, with toxins accumulating in their bodies and disrupting their health, reproduction, and ecosystems. With pollution affecting every square mile of the ocean and around 40% of marine ecosystems, urgent action is needed to protect these beloved creatures.

Noise pollution impacts communication and navigation

Dolphins are highly intelligent marine mammals that rely heavily on their sophisticated echolocation system for communication and navigation. Unfortunately, human activities have led to increasing levels of noise pollution in the oceans, posing significant threats to dolphins and disrupting their natural behaviours.

One of the main sources of underwater noise pollution is commercial vessels, recreational boats, and military exercises. The noise from these activities can lead to a phenomenon known as "masking," where the ambient noise in the water overwhelms the sounds emitted by dolphins. This interference negatively impacts their ability to detect prey, communicate with their pod members, and navigate their surroundings effectively.

The impact of noise pollution on dolphin communication was highlighted in a study published in the journal Current Biology. Researchers observed two dolphins, Delta and Reese, and found that as underwater noise levels increased, the dolphins had to raise their volume and lengthen their calls to communicate. Despite these adaptations, the dolphins experienced decreased success in coordinating with each other.

In addition to communication, noise pollution also affects dolphin navigation. Dolphins use echolocation to navigate through the ocean and locate prey. Excessive noise can alter their perception of the surrounding habitat, leading them into dangerous areas or away from critical feeding grounds. This disorientation can have detrimental effects on their health and survival.

Furthermore, prolonged exposure to noise pollution can cause chronic stress, decreased reproductive success, and increased vulnerability to predation in dolphin populations. It is crucial to address underwater noise pollution to ensure the well-being and conservation of these magnificent creatures. Implementing measures such as reducing ship speeds, using quieter marine equipment, and establishing marine protected areas can help mitigate the harmful effects of noise pollution on dolphins.

Oil spills and chemical pollutants cause respiratory ailments and immune dysfunction

Oil spills and chemical pollutants have been shown to cause respiratory ailments and immune system dysfunction in dolphins. The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 is a prime example of this. Researchers estimate that the local dolphin population has lost over 50% of its members in the decade since the spill. The dolphins inhaled contaminated air, causing respiratory issues and impairing their immune systems. This has led to long-term increases in mortality, failed pregnancies, and a higher risk of other diseases and infections.

Oil spills can also contaminate the water and the fish that dolphins eat. Dolphins may inhale volatile toxic chemicals evaporating from the surface of the oil or ingest the oil directly. High doses can adversely affect the nervous system. Oil spills can also kill off smaller animals, such as shrimp, that are part of a dolphin's diet.

In addition to oil, chemical pollutants such as PCBs (polychlorinated biphenyls) and DDTs (trichloroethane) are toxic to dolphins. These chemicals can enter a dolphin's body when it ingests contaminated fish or other organisms. Instead of eliminating these toxins, dolphins store them in their fatty tissues or blubber, and even in their breast milk. This can impair the reproductive systems of male and female dolphins and cause birth defects in calves.

Furthermore, chemical pollutants can affect the health of dolphins by disrupting their endocrine, reproductive, and immune systems. These pollutants can also impact brain development and the nervous system. Dolphins are particularly vulnerable to the toxic effects of these chemicals due to their inability to detoxify organic pollutants effectively.

Plastic ingestion causes fatal tears and blockages

Dolphins are beloved creatures, adored for their playful and friendly nature, as well as their high intelligence and sociability. Unfortunately, plastic ingestion is one of the most significant threats to dolphins, causing fatal tears and blockages, leading to illness, disease, and even starvation.

Plastic ingestion can cause severe internal damage to dolphins, including fatal tears in their digestive systems. The sharp edges of ingested plastic can cut and tear the delicate tissues of a dolphin's stomach and intestines, leading to internal bleeding and infection. These injuries can be life-threatening, causing severe pain and discomfort, and often requiring immediate veterinary attention.

Blockages are another serious consequence of plastic ingestion in dolphins. Plastic debris, such as bags, nets, and other discarded fishing gear, can become lodged in a dolphin's throat, stomach, or intestines, obstructing their digestive tract. This blockage prevents food from passing through the digestive system, leading to a condition known as gastric impaction. As a result, dolphins can experience severe abdominal pain, nausea, and vomiting. In some cases, the blockage may even require surgical intervention to save the dolphin's life.

The impact of plastic ingestion on dolphins goes beyond physical injuries. When dolphins ingest plastic, they often experience a false sense of fullness, leading to malnutrition and starvation. Additionally, the ingested plastic can release toxic chemicals into the dolphin's body, causing various health issues, including reproductive problems and increased vulnerability to diseases.

Moreover, plastic in the ocean can absorb and release toxic chemicals, such as persistent organic pollutants (POPs). These toxins can bioaccumulate in the bodies of dolphins, leading to biomagnification in predator species like dolphins. As a result, dolphins may suffer from impaired immune systems, leaving them more susceptible to diseases and infections.

The threat of plastic ingestion highlights the urgent need for global efforts to reduce plastic pollution in our oceans. By addressing this issue, we can help protect dolphins and other marine life from the devastating consequences of plastic ingestion, ensuring their health and longevity in their natural habitats.

Toxins bioaccumulate and biomagnify in the body

In the case of dolphins, bioaccumulation occurs when they ingest contaminated fish or simpler organisms such as plankton or algae. The toxins from these sources are stored in the fatty tissues, or blubber, of the dolphin, and can also be passed on to their calves through their milk. These toxins can impair the reproductive systems of male and female dolphins and cause birth defects in their offspring. They can also make dolphins more susceptible to diseases and infections, such as pneumonia and skin infections.

Biomagnification occurs when larger predators, such as dolphins, consume contaminated prey. As the toxins move up the food chain, their concentration increases. This means that apex predators like dolphins are at risk of having potentially fatal levels of toxins in their bodies. For example, PCBs (polychlorinated biphenyls) are toxic chemicals that can cause sterility and reproductive problems in dolphins. Despite a global ban on PCBs in 2004, they still leak into the environment and accumulate in the bodies of dolphins, impacting their populations.

The impact of bioaccumulation and biomagnification on dolphins is a serious issue. The toxins that build up in their bodies can affect their health, reproduction, and survival. It also highlights the importance of addressing pollution and its sources to mitigate the harm caused to dolphins and other marine life.

Entrapment by discarded fishing gear

Dolphins can become entangled in this discarded fishing gear, restricting their movement, ability to fish, and even their escape from predators. Entanglement can lead to cuts, skin sores, infection, and death. It is one of the leading causes of anthropogenic dolphin deaths and injuries in wild dolphin populations.

The problem of ghost fishing gear is not limited to a specific region but is seen around the world, including in the UK and the northwest Atlantic Ocean. In the UK, entanglement is the single most common cause of death for cetaceans, with harbour porpoises and common dolphins being the worst-affected species. A study from 2012 examining 1,762 cases of dead or injured whales in the northwest Atlantic Ocean between 1970 and 2009 also found that entanglement was the primary cause of death, affecting six endangered or specially concerning species.

The impact of entanglement can be devastating for dolphins. It can cause them to starve or drown, and even if they survive, heavy ropes can leave lacerations or slice off their flukes. The ropes can also get caught in their baleen, restricting their movements or pinning their mouths shut.

Conservation efforts are crucial to address this issue and protect dolphin populations. Organisations such as the Scottish Entanglement Alliance are working to better understand the scale and impact of the issue and find solutions to minimise the risk of entanglement.

Frequently asked questions