Current Threats to Marine Mammals. By Tim Chin. Current Threats. Pollution Overfishing Entanglement Other. Pollution. Noise Oil Chemical Plastics and Debris The Plastic Sea. Noise Pollution.
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Many cetaceans, such as certain whales and dolphins, rely on sound for communication and locating food. They are adversely affected by human-made noise.
Noise pollution can come from a wide variety of sources, with some of those being ship traffic, seabed drilling, seismic surveys, sonars, oceanographical experiments, recreational activities, and underwater explosions.
Low levels of noise pollution are enough to cause a change of behavior in whales and dolphins. They will generally try to escape from the source of the noise, which can result in them being forced out of their habitat.
Higher levels of noise pollution, such as the sound of underwater explosions, can cause great discomfort and stress. It can even result in physical acoustic trauma in the form of tissue damage to the ears.
Cetaceans affected by high intensity noise pollution, with sonars being an example, are likely to become stranded and die.
Marine mammals suffer from the increasing concentrations of heavy metals, PCBs, dioxins, DDT, and other persistent organic pollutants that are dumped or leaked into the ocean.
Due to the bioaccumulation of chemical pollutants, marine mammals can suffer from a wide array of illnesses and disruptions to their normal body functions. Pesticides and industrial compounds usually have a negative impact on the endocrine, digestive, and nervous systems, which can lead to a decrease in health, growth and development issues, a weakened immune system, and diminished reproductive abilities.
Plastic and other debris can easily trap and get tangled on various marine mammals. This can lead to numerous complications.
Marine mammals sometimes mistake marine debris for food and accidentally ingest it. This can cause a blocking of the digestive tract, choking, internal injuries, and an accumulation of toxic compounds. All of these implications can be fatal.
Due to gyres, the circular currents in the ocean, it is common for plastic and other flotsam to build up in certain areas.
In the Pacific Ocean, between California and Japan, there are two linked patches of garbage which are often referred to as a plastic soup. It is roughly twice the size of the continental US and is a threat to marine mammals.
It is estimated that this plastic sea is the cause of death for over 100,000 marine mammals every year.
When fishing, commercial fisheries often compete for the resource of fish with their natural predators. This can make it more difficult for a population of marine mammals to obtain food.
Overfishing can also cause an imbalance in an aquatic ecosystem by removing one of the links in the food chain. This in turn can result in the decline or displacement of marine mammals which depended on the harvested fish as a food source.
Debris, such as plastic rings and fishing lines, mainly pose a threat to pinnipeds, or walruses and seals.
These marine mammals often become trapped with debris around their necks or heads, which can restrict breathing, eating, and even swimming. Debris can also inflict physical wounds. At the very least, these negative impacts will debilitate their targets.
Once snared, it is a very difficult, if not impossible task for a marine mammal to remove its bindings.
Due to global warming, marine mammals could lose valuable food sources and habitats.
Populations of fish, which are preyed upon by marine mammals, are predicted to move into deeper and cooler water which is farther away from shore. This change is troubling to seals and other pinnipeds that require land in order to reproduce and sleep on.
Migratory whales could also suffer, as they are dependent on finding certain resources at the ends of their migratory routes.
Overall, there are many threats that oppose marine mammals, such as the numerous types of pollution, overfishing, entanglement, ship collisions, and climate change.
However, these threats are not without hope of being remedied, as numerous laws, regulations, and organizations, such as the Marine Mammal Protection Act and the creation of aquatic reserves, are in place to ensure the safety and stability of the marine mammal populations.