Meghan Hodges
Dolphins are fascinating creatures that have captured the human imagination for centuries. However, these intelligent and social mammals face a grave threat in the form of pollution. From oil spills to plastic waste, and noise to chemical runoff, human activities are having a devastating impact on dolphin populations worldwide. With their habitats degraded and their health at risk, it is clear that urgent action is needed to protect these beloved creatures and ensure their survival for future generations. In this article, we will explore the various ways in which pollution hurts dolphins and discuss potential solutions to mitigate these harmful effects.
| Characteristics | Values |
|---|---|
| Noise pollution | Interrupts normal behaviour, drives dolphins away from important areas, and can cause injury or death |
| Marine debris | Plastic waste blocks dolphins' breathing passages and stomachs, causing death |
| Toxins | Toxins enter the marine environment through land-based runoff, air pollution, and ocean dumping, and accumulate in dolphins' bodies, causing cancerous tumours, weakening their immune systems, and disrupting reproduction |
| PCBs | PCBs are toxic chemicals that build up in dolphins' fatty tissue (blubber) and are released into their bodies when they break down this tissue for energy, leading to potential fatalities |
| Habitat loss | Human activities such as industrial development and pollution contribute to the degradation of dolphins' habitats |
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What You'll Learn
- Noise pollution: Caused by ships, oil exploration, military exercises, and coastal development
- Toxins in the water: From plastics, industrial chemicals, and microscopic particulates
- Toxins in prey: Toxins accumulate in smaller organisms, which are eaten by dolphins
- Entanglement: Dolphins are ensnared and drowned by plastic waste and abandoned fishing gear
- Habitat loss: Pollution degrades dolphin habitats, threatening their survival
Noise pollution: Caused by ships, oil exploration, military exercises, and coastal development
Dolphins are highly sensitive to sound and rely on it for feeding, socializing, and navigation. Noise pollution from ships, oil exploration, military exercises, and coastal development can cause hearing loss or even death in dolphins.
Shipping noise can cause stress in dolphins, leading to lower fertility, poor immune system function, and growth suppression. The constant noise from ships can also mask the natural sounds that dolphins use to communicate and navigate, disrupting their behaviour and ability to find food and mates.
In Hong Kong, for example, the Chinese white dolphin population has declined by over 80% in 15 years due to "severe human disturbance." The subtropical sea surrounding Hong Kong is a busy shipping lane with constant freight ship traffic, high-speed ferries, and coastal development. The noise from these activities has likely contributed to the decline of the Chinese white dolphin population.
Oil exploration activities, such as the use of seismic air guns for surveying, can also harm dolphins. A study found that narwhals exposed to seismic air guns immediately began diving to escape the noise, putting their health at risk.
Military sonar and seismic guns used in exercises can reach volumes of over 200 decibels, louder than a rocket taking off. These loud noises have been linked to whale strandings and decompression sickness, which occurs when animals surface too quickly. While dolphins may not be killed directly by the sound waves, the impact on their behaviour and health can be significant.
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Toxins in the water: From plastics, industrial chemicals, and microscopic particulates
Dolphins are highly intelligent and social mammals that play a vital role in maintaining the delicate balance of marine ecosystems. However, human activities have introduced various contaminants into their aquatic habitats, posing significant threats to their health and survival. One of the most pressing issues is the presence of toxins in the water, stemming from plastics, industrial chemicals, and microscopic particulates.
Plastics are a pervasive form of pollution in our oceans, with an estimated 170 trillion bits of microplastics in the oceans alone. Dolphins, like other marine creatures, often mistake plastic for food, leading to fatal blockages in their breathing passages and stomachs. Plastic pollution also entangles dolphins, causing them to drown. Furthermore, microplastics have been detected in the exhaled breath of dolphins, indicating inhalation of these tiny particles. While the long-term effects on dolphins' lungs are still unknown, there are concerns about potential lung inflammation, tissue damage, and even cancer risks, similar to the impacts seen in humans exposed to microplastics.
Industrial chemicals, such as PolyChlorinated Biphenyls (PCBs), have been detected in high concentrations in the blubber of dolphins. PCBs were once widely used in building materials but are now banned globally due to their toxic effects. Dolphins store these chemicals in their fatty tissues, and when they break down this blubber for energy, a flood of toxic PCBs is released into their bodies. Unfortunately, dolphins lack the necessary enzymes to effectively break down and eliminate these dangerous chemicals, leading to a buildup over time.
Another form of water toxin is the result of sewage and fertilizer runoff, which feeds the growth of algae. While algae produce toxins, they also deplete the water of oxygen, endangering aquatic life, including dolphins. Additionally, certain chemicals like DDT and PCBs are known to cause widespread sterility, cancers, and genetic abnormalities in populations of land animals. These toxins have the potential to severely impact dolphin populations as well.
The complex interplay of these various toxins in the water creates a challenging environment for dolphins to navigate. As top predators with long life spans, dolphins serve as sentinel species, providing valuable insights into the impacts of pollutants on marine ecosystems and offering warnings about potential risks to human health. Addressing plastic pollution, reducing industrial chemical usage, and mitigating sewage and fertilizer runoff are crucial steps in protecting dolphins and preserving the delicate balance of marine life.
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Toxins in prey: Toxins accumulate in smaller organisms, which are eaten by dolphins
Dolphins are affected by toxins that accumulate in their prey. These toxins enter the marine environment through land-based runoff, air pollution, and ocean dumping. Toxins can settle at the seafloor and are ingested by organisms that live or feed on bottom sediments. As these toxins are not digested, they accumulate within the animals that ingest them and become more concentrated as they move up the food chain. This process, known as biomagnification, results in higher-level predators like dolphins having greater exposure to toxic materials.
One example of this is the accumulation of mercury in the marine food chain. Mercury settles at the seafloor and is ingested by organisms living or feeding on the sediments. As mercury is not digested, it accumulates in the organisms and becomes more concentrated as it moves up the food chain. Seabirds that consume fish are at a higher risk of mercury poisoning compared to those that primarily eat clams, as clams filter and accumulate lower concentrations of mercury from the seawater.
Another example is the presence of potent toxins produced by phytoplankton (a type of microscopic algae). While these toxins do not seem to harm small creatures like zooplankton, they can quickly accumulate through the food web as each consumer takes in more of the toxin. This process, known as bioaccumulation, has been observed in organisms such as krill, mussels, and fish, which retain the toxins from phytoplankton in their bodies. As dolphins feed on these organisms, they ingest the accumulated toxins, which can have detrimental effects on their health.
Additionally, dolphins are vulnerable to the toxic effects of chemicals such as polychlorinated biphenyls (PCBs), which are introduced into the marine environment through human activities. PCBs accumulate in the fatty tissue (blubber) of dolphins as they consume contaminated fish or mammals. When dolphins break down their blubber for energy during stressful periods, such as food scarcity, a flood of toxic PCBs is released into their bodies. Dolphins are particularly susceptible to the harmful effects of PCBs due to their limited ability to produce the enzymes needed to break down these chemicals.
The accumulation of toxins in prey items has significant consequences for dolphins. Not only does it impact their health, but it can also affect their reproductive success and survival. High levels of toxins can cause reproductive failure, cysts, cancer, and genetic abnormalities in dolphins. The transfer of toxins from mothers to their first-born calves can be fatal, as evident in the case of Lulu, an orca that stranded on the Isle of Tiree with PCB levels 20 times the safe limit.
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Entanglement: Dolphins are ensnared and drowned by plastic waste and abandoned fishing gear
Dolphins are highly intelligent and friendly aquatic mammals that are closely related to small whales and porpoises. They are, unfortunately, one of the species most endangered by plastic pollution. The primary threat to dolphins comes from plastic waste and abandoned fishing gear in the ocean, which they can easily get entangled in, leading to injury or death.
Dolphins, being apex predators, can mistake plastic products for food items, and end up consuming them. This has painful and harmful consequences for them. Ingesting plastic can cause internal injuries and lead to a range of health issues. Research has shown that about 56% of dolphins worldwide have consumed plastic.
Dolphins can also become entangled in plastic waste, such as plastic bags, fishing nets, and other forms of marine litter. This restricts their movement, making it difficult for them to swim and find food. The added weight and size of the entangled debris can further hinder their ability to navigate and escape. In some cases, the weight of the debris may be too much, causing them to drown.
The impact of plastic pollution on dolphins is not just limited to physical entanglement and ingestion. The presence of plastic in their environment can also lead to a decline in their population size. As dolphins are at the top of many marine food chains, the increase in plastic pollution can disrupt the natural food web and ecosystem balance, resulting in higher death rates among dolphins.
The issue of plastic pollution in the ocean is a direct consequence of human activities and consumer choices. The manufacturing of plastics and the use of single-use plastic products contribute significantly to the pollution of our oceans. It is estimated that only about 3% of plastic waste is recycled, with hundreds of millions of pounds of plastic ending up in the oceans each year.
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Habitat loss: Pollution degrades dolphin habitats, threatening their survival
Dolphins are fascinating creatures that inhabit shallow, estuarine waters near the shore. They are beloved by many, yet their survival is threatened by human activities. One significant threat to dolphins is habitat loss due to pollution, which degrades their environment and endangers their lives.
Pollution introduces contaminants into the ocean, including oil, sewage, litter, chemicals, and plastics. These pollutants have devastating effects on the marine ecosystem and the dolphins that call it home. Dolphins, as top predators, are particularly vulnerable to the accumulation of toxins in their prey. When dolphins consume contaminated fish, the toxins build up in their bodies, leading to health issues and reproductive problems.
One of the most concerning pollutants is PolyChlorinated Biphenyls (PCBs), which were widely used in building materials until a global ban in 2004. PCBs persist in the environment and accumulate in the fatty tissue of dolphins, leading to toxic buildup that can prove fatal. The transfer of PCBs from mother dolphins to their first-born calves is also of significant concern, as it exposes the next generation to high levels of these harmful chemicals.
In addition to chemical pollution, physical debris such as discarded plastics and "ghost nets" (abandoned fishing gear) pose a grave threat to dolphins. Dolphins can mistakenly ingest plastic, leading to blockage of their breathing passages and excruciating deaths. Entanglement in ghost nets is another danger, as dolphins and other marine mammals can become trapped and drown. The presence of these foreign objects in their habitat degrades the quality of the dolphins' environment and puts their survival at risk.
Noise pollution is another often-overlooked form of pollution that degrades dolphin habitats. Human activities such as shipping, military exercises, and industrial practices generate excessive noise that interferes with dolphins' ability to communicate, navigate, and hunt. The constant din can drive dolphins away from areas vital to their survival and even cause hearing loss or death. The impact of noise pollution on dolphin populations is significant, and efforts to reduce it are of utmost importance.
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Frequently asked questions
Dolphins use echolocation to hunt, socialise and navigate. Noise pollution from human activities such as shipping, military exercises, and oil and gas exploration interferes with their normal behaviour, driving them away from areas important to their survival, and can even cause hearing loss or death.
Dolphins often mistake plastic for food, which can block their breathing passages and stomachs, leading to excruciating deaths. Dolphins can also get entangled in plastic waste, such as abandoned fishing gear, which can drown them.
Dolphins are top predators, so they face higher concentrations of toxins that accumulate in their prey. These toxins can affect their health, cause reproductive issues and weaken their immune systems.
Dolphins frequently surface to breathe, so they inhale harmful substances in the air, potentially leading to respiratory issues. Toxins in the water accumulate in smaller organisms, which are then eaten by dolphins.
Ship noise stresses whales and can cause hearing loss or even death. Ship accidents can also cause oil spills, which are particularly harmful to dolphins as they get their insulation from blubber which can be fouled with oil.
