Seals And Water Pollution: Understanding The Impact

Seals are intelligent, strong, and playful creatures that are suffering from human acts and wastefulness. Water pollution, in particular, poses a significant threat to their health and survival. From ingesting plastic to entanglement in marine debris, seals are inadvertently paying the price for human negligence and the growing issue of plastic pollution in our oceans. With plastic waste tightening around their necks, flippers, or mouths, seals face a gruesome fate, and the problem is only worsening with each passing year.

Seals are affected by plastic ingestion

Seals are naturally playful and curious creatures, and their natural habitats are increasingly becoming littered with plastic waste. This waste comes from two sources: land-based pollution, such as plastic blown into the sea from a littered beach or washed into the sea by stormwater, and ocean-based pollution, which comes from garbage disposed of at sea by ships and abandoned and lost fishing gear (also called ghost gear).

Seals often end up playing with plastic rubbish and ocean pollution, such as fishing lines, fishing nets, packing straps, and plastic bags. Once entangled in this plastic waste, seals are unable to free themselves. As they grow, the plastic waste tightens around their necks, flippers, or mouths, leading to a painful death. All seal entanglements are caused by negligent human behaviour.

Microplastics are another major issue. These tiny pieces of plastic, which come from larger plastics that have degraded over time, are often ingested by seals due to their small size. Plastic contains toxic chemicals, which can increase the chance of disease and affect reproduction. After ingesting microplastics, seals may suffer for months or years before they die.

In 2014, it was estimated that there were 15 to 51 trillion microplastic particles floating in the world's oceans, weighing between 93,000 and 236,000 tonnes. This plastic waste is a global crisis, with plastic expected to outweigh all the fish in the sea by 2050. It is essential that we address the issue of plastic pollution to protect seals and other marine life.

Seals are at risk of bioaccumulation

For example, a 2005 study found that harbor seals in South Puget Sound were seven times more contaminated than those in Canada's Georgia Strait. High levels of contaminants, such as PCBs and PBDEs, have been detected in seal tissues. These toxins are passed from generation to generation through the milk of mothers to their offspring. Seals are also vulnerable to parasitic infections, low body weight, and viruses due to compromised immune systems caused by contaminants.

Bioaccumulation of pollutants in seals can have long-term effects on seal populations. For instance, a study on the eastern Pacific stock of northern fur seals found that exposure to persistent organic pollutants (POPs) may be a contributing factor to population declines since 1980. Additionally, a study on grey seals from the Faroe Islands found high concentrations of heavy metals such as Cd, Cu, Hg, and Se in their liver, kidney, and muscle tissues.

The bioaccumulation of toxins in seals is a concerning issue that can have detrimental effects on both individual seals and seal populations as a whole. It is important to address and mitigate the sources of pollution to protect the health and well-being of these marine mammals.

Seals are vulnerable to entanglement in man-made debris

Seals are naturally playful and curious animals, and their natural habitats are increasingly encroached upon by human activity. As a result, they are vulnerable to entanglement in man-made debris, which can lead to injury and death. This issue is particularly prevalent in areas with a high volume of fishing activity, such as the Western Cape coastline in South Africa, where seals often play with plastic rubbish and ocean pollution, such as fishing lines, nets, packing straps, and plastic bags.

The plastic waste that entangles seals can come from land-based pollution, such as plastic blown into the sea from littered beaches or washed into the sea by stormwater. It can also come from ocean-based pollution, including garbage disposed of at sea by ships and abandoned, lost, or discarded fishing gear, also known as ghost gear. Ghost gear makes up an estimated 10% of plastic waste in our oceans and continues to catch seals and other marine animals.

Once entangled, seals are unable to free themselves, and as they grow, the plastic waste tightens around their necks, flippers, or mouths, leading to a slow and painful death. All seal entanglements are caused by negligent human behaviour.

Efforts to clean up marine debris and disentangle seals have been successful in some areas. For example, a large-scale, multi-agency program in the Northwestern Hawaiian Islands removed hundreds of metric tons of plastic debris and led to a 71% decline in seal entanglement rates at Pearl and Hermes Reef. However, marine debris continues to accumulate, and the cleanup and disentanglement efforts must be ongoing.

The problem of seal entanglement in man-made debris is a pressing issue that requires a twofold solution. Firstly, illegal and industrial fishing fleets must be held accountable for emptying our oceans and filling them with ghost gear. Secondly, corporations must stop producing single-use plastics and provide reusable alternatives to reduce the amount of plastic pollution entering our oceans.

Seals absorb and retain pollutants

Seals are affected by water pollution in various ways, and one of the most pressing issues is plastic pollution. Seals are susceptible to entanglement in plastic debris, such as fishing lines, nets, packing straps, and plastic bags. Once entangled, they cannot free themselves, and as they grow, the plastic tightens, leading to a slow and painful death. This issue is particularly prevalent on the Western Cape coastline, where a large population of Cape Fur Seals competes with the fishing industry for the same resources.

Another significant concern is the ingestion of microplastics. Seals are apex predators, and while they do not directly consume microplastics, they ingest them through the consumption of contaminated fish. Microplastics are tiny plastic particles smaller than 5mm in size, and they can have toxic effects on seals. Bioaccumulation, or the gradual accumulation of substances within an organism, occurs when the rate of absorption is faster than the rate of elimination. This results in a high concentration of microplastics in the bodies of seals, which can be fatal.

In addition to microplastics, seals are also affected by larger plastic debris. They are naturally playful and curious creatures, and they often interact with plastic rubbish that ends up in the ocean. This includes discarded plastic items such as plastic bags and balloons, which seals may mistake for food. When ingested, these plastics can cause blockages and internal injuries, leading to health complications and even death.

Furthermore, seals are also affected by chemical pollutants in the water. Their thick layers of blubber absorb and retain pollutants, including contaminants such as PCBs (polychlorinated biphenyls) and PBDEs (flame retardants). These toxins are stored in their blubber and can pass from generation to generation through the milk of mothers to their offspring. Exposure to these pollutants can cause physical abnormalities, behavioural changes, impaired reproduction, and immune disorders in seals.

The impact of water pollution on seals is a pressing issue, and it is important to address the root causes of this problem. Reducing plastic consumption, improving waste management, and holding industries accountable for their plastic waste are crucial steps towards protecting seal populations and preserving the health of our marine ecosystems.

Seal pups are highly contaminated with toxins

Seals are considered a sentinel species, indicating the health of the marine environment. Harbour seals, in particular, are affected by pollution because they do not migrate but live year-round in the same region. Their thick layers of blubber absorb and retain pollutants from industrial waterways.

The Southern Resident orcas are among the most contaminated marine mammals in the world. Contaminants are stored in the blubber of marine mammals at the top of the food chain, such as dolphins, seals, and orcas. These toxins have been shown to cause physical abnormalities, impair the development of motor activities and cognition, cause behavioural changes, impair reproduction, and cause immune disorders in marine mammals.

In addition to chemical pollution, seal pups are also at risk of entanglement in plastic debris. Seals are playful and curious animals and often end up playing with plastic rubbish and ocean pollution, such as fishing lines, nets, packing straps, and plastic bags. Once entangled, they cannot free themselves, and as they grow, the plastic waste tightens, leading to a gruesome death.

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