Ocean Pollution: Understanding Its Impact On Animal Life

Marine animals are severely affected by ocean pollution. Every year, billions of pounds of trash and other pollutants enter the ocean, endangering the lives of many marine animals. Marine debris ingestion and entanglement in items like plastic bags, containers, fishing lines, nets, and packing bands directly impact marine life. According to the United Nations, at least 800 species worldwide are affected by marine debris, with plastic accounting for 80% of that litter.

Sea turtles, coral reefs, dolphins, sharks, seabirds, and whales are among the common victims of marine debris. Sea turtles often mistake plastic bags for food, leading to health issues and death. Dolphins, known for their intelligence, can choke on plastic bottles or garbage, mistaking them for fish. Sharks face the dual threat of pollution and overfishing, often getting entangled in gill nets or long lines from fishermen. Seabirds, such as gulls and pelicans, mistake plastics for food and become entangled or suffer internal injuries.

The impact of ocean pollution extends to larger marine mammals like whales, which are found with bellies full of plastic and other debris. Beluga whales, in particular, are considered the most toxic marine animal, with high levels of herbicides, pesticides, and other chemicals in their bodies. Ocean pollution also contributes to the degradation of coral reefs, vital habitats for many sea animals.

Addressing ocean pollution requires local, national, and international efforts to reduce, manage, and clean up marine debris. It is essential to raise awareness, improve waste management, and promote recycling to protect marine life and the health of our oceans.

Plastic ingestion

Sea turtles, for example, often mistake plastic sheeting and plastic bags for their jellyfish prey. A review estimated that 32% of turtles have plastic marine debris in their stomachs. Similarly, a study found that a quarter of fish at markets in California contained plastic in their guts, mostly in the form of plastic microfibers.

Plastics that float, break into small pieces, and are colourful are more likely to attract hungry animals. These plastics can also carry harmful pollutants, which may enter the body of an animal if ingested.

The impact of plastic ingestion on the food web is also significant. Plastics transported by surface currents collect in areas where currents meet, called convergence zones, which attract marine life across the food web. As a result, larger amounts of marine debris collect in these areas, increasing the likelihood of plastic ingestion by animals.

To address this issue, it is essential to understand the sources of marine debris and work towards reducing plastic pollution to protect marine wildlife.

Entanglement in plastic

Entanglement can harm marine animals in several ways. They may drown or starve due to the restriction of movement caused by the entangling gear. The gear can also cut into their flesh, causing physical trauma and infections. Entangled animals may also be unable to avoid vessels, increasing the risk of vessel strikes. Smaller marine animals, like sea turtles, seals, and porpoises, may drown immediately if entangled in large or heavy gear. Even large whales, which can usually pull gear off the ocean floor, face risks of exhaustion and infection.

Entanglement is considered a primary cause of human-induced mortality in many whale species, especially right whales, humpback whales, and gray whales. It is also a significant threat to endangered species, such as Hawaiian monk seals and Pacific loggerhead sea turtles.

Efforts to reduce entanglements include disentanglement operations by trained professionals and the development of gear modifications and management strategies to minimize the risk. Preventing entanglement requires proper disposal of fishing gear and trash, as well as participation in community clean-up efforts to reduce the amount of plastic entering the ocean.

Coral reef degradation

Coral reefs are in decline across the world, with many scientists believing that their very existence may be in jeopardy unless efforts to protect them are intensified. The impacts of these threats disproportionately affect minority, low-income, and indigenous populations that rely on coral reefs for nutrition and coastal protection.

Local Threats to Coral Reefs

Coral reefs are particularly vulnerable to the effects of human activities, both through direct exploitation of reef resources and through indirect impacts from adjacent human activities on land and in the coastal zone. Many of the human activities that degrade coral reefs are woven into the social, cultural, and economic fabric of regional coastal communities.

Physical Damage or Destruction

Coastal development, dredging, quarrying, destructive fishing practices, boat anchors, and recreational misuse can all cause physical damage or destruction to coral reefs.

Pollution

Pollution that originates on land but finds its way into coastal waters can also threaten coral reefs. For example:

• Sedimentation from coastal development, urban stormwater runoff, forestry, and agriculture can smother corals and interfere with their ability to feed, grow, and reproduce.
• Nutrients from agricultural and residential fertilizer use, sewage discharges, and animal waste can lead to the growth of algae that blocks sunlight and consumes oxygen needed by corals for respiration.
• Pathogens from inadequately treated sewage, stormwater, and runoff from livestock pens can cause disease in corals, especially if they are already stressed by other environmental conditions.
• Toxic substances, including metals, organic chemicals, and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and landfill runoff can affect coral reproduction, growth, and other physiological processes.
• Trash and microplastics from improper disposal and stormwater runoff can snag on corals, block sunlight needed for photosynthesis, or be consumed by coral, fish, sea turtles, and other reef animals, blocking their digestive tracts and potentially introducing toxins.

Overfishing

Overfishing can alter food-web structure and cause cascading effects, such as reducing the numbers of grazing fish that keep corals clean of algal overgrowth.

Coral Harvesting

Coral harvesting for the aquarium trade, jewelry, and curios can lead to over-harvesting of specific species, destruction of reef habitat, and reduced biodiversity.

Global Threats to Coral Reefs

Increased ocean temperatures and changing ocean chemistry are the greatest global threats to coral reef ecosystems. These threats are caused by warmer atmospheric temperatures and increasing levels of carbon dioxide dissolved in seawater. As atmospheric temperatures rise, so do seawater temperatures, which can cause corals to expel the microscopic algae that they depend on for food. Without this algae, corals lose their coloration, a condition known as coral bleaching. Severe or prolonged bleaching can kill coral colonies or leave them more vulnerable to other threats such as infectious disease.

Oil spills

Sea turtles, such as the endangered Kemp's ridley turtle, are vulnerable to oil at all stages of life. They can inhale oil fumes and swallow oil when breathing at the ocean surface in or near oil slicks. Fish, including bluefin and yellowfin tuna, are also impacted. Oil damages the gills of fish, making it difficult for them to get enough oxygen. It can also kill fish eggs and impair the growth of young fish.

Following an oil spill, there are specialists and veterinarians trained to deal with oiled wildlife. They know how to clean oil from animals, rehabilitate them, and return them to the environment.

Noise pollution

Ocean noise pollution is a form of environmental pollution caused by human activities that generate unnatural and excessive sound underwater. This includes commercial shipping, oil exploration, seismic surveys, offshore wind turbine installation, and military sonar. Marine animals, which are highly dependent on sound for survival, are extremely vulnerable to this type of pollution.

Effects on Marine Mammals

Marine mammals, such as whales, dolphins, and porpoises, are particularly susceptible to the detrimental effects of noise pollution. They rely on sound for various vital functions, including communication, locating mates and prey, navigating, and defending their territories. Noise pollution interferes with these natural behaviours and can lead to behavioural and physiological changes, hearing loss, injury, and even death.

Very loud noises can cause panic in these animals, leading them to ascend too quickly to escape the sound, resulting in decompression sickness and tissue damage from gas bubble lesions. Naval sonar devices, which operate similarly to echolocation used by whales and dolphins, have been linked to mass stranding events. The loud and disorienting sounds can cause whales and dolphins to become stranded, leading to death or severe injury.

Effects on Other Marine Life

Seismic surveys, which use powerful airguns to map the seafloor, can severely damage the internal organs of giant squid and cause mass strandings. These surveys have also been linked to increased mortality rates in scallops and a reduction in the zooplankton population, which forms the basis of the marine food web.

Addressing Noise Pollution

Despite the significant impacts of ocean noise pollution, there are currently no international legal regulations addressing this issue. However, some local governments and ports have established their own regulations. For example, the Port of Vancouver offers discounts to vessels that voluntarily comply with environmental guidelines to reduce noise pollution.

To effectively address this problem, policies and regulations are needed to reduce propeller noise from ships, mitigate the sounds of sonar equipment, seismic air guns, pile driving, and construction. Quieter technologies, such as 'marine vibroseis' for seismic surveys and alternative methods for pile driving, can also help reduce noise pollution. Additionally, slowing down ships can reduce noise output, as recommended by the International Maritime Organization (IMO).

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