Marine Life: Pollution's Impact And Devastating Effects

Marine life is incredibly vulnerable to the harmful effects of pollution. The ocean is constantly exposed to a variety of pollutants, including industrial, agricultural, and residential waste, particles, noise, excess carbon dioxide, and invasive organisms. These pollutants can have detrimental effects on the health and survival of marine organisms, from coral and shellfish to fish and marine mammals. One of the significant impacts of pollution is ocean acidification, caused by the absorption of airborne carbon dioxide by seawater, leading to reduced seawater pH and potential harm to many marine organisms. Additionally, pollution can cause coral bleaching and disease, decreased coral reproductive health and skeletal integrity, and a loss of biodiversity. Marine debris, such as plastic pollution, poses a severe threat to marine life, leading to entanglement, suffocation, and ingestion of harmful substances. The accumulation of contaminants in the food chain further exacerbates the problem, with potential toxic effects on both marine life and humans who consume seafood. Addressing marine pollution is crucial for the health and sustainability of marine ecosystems and requires a combination of international laws, policies, and individual efforts to reduce pollution and protect our oceans.

Plastic pollution

Ingestion

Marine animals of all sizes, from tiny seahorses to whales, mistake plastic for food. This is because plastic bags can resemble squid or jellyfish, and plastic pellets can sit on the surface of the water and be mistaken for food by seabirds and other marine species. As a result, ingestion of plastic can lead to suffocation, starvation, and toxic contamination. Microplastics, in particular, are easily consumed by marine life because they are invisible to the naked eye. They can also absorb toxins, which can then be transferred to the fatty tissues of the organisms that ingest them.

Entanglement

Large items of plastic, such as discarded fishing nets and six-pack rings, can trap and entangle marine animals, leading to starvation, injury, and increased vulnerability to predators. Discarded fishing nets can also smother and break coral reefs, preventing healthy growth.

Other Effects

Solutions

To address plastic pollution, it is important to focus on prevention and proper waste management. This includes reducing plastic use, recycling, and reusing plastics, as well as increasing awareness about the issue.

Chemical pollution

Marine pollution is caused by a combination of chemicals and trash, with the majority of waste coming from land-based activities. Chemical pollution, in particular, has detrimental effects on marine life and ecosystems.

Oil and Chemical Spills

Oil and chemical spills are a significant source of marine pollution, with long-lasting impacts on the environment and marine organisms. Oil spills are highly toxic to marine life and are extremely challenging to clean up. Polycyclic aromatic hydrocarbons (PAHs), for instance, persist in the marine environment for years and are harmful to marine creatures.

Atmospheric Pollution

The atmosphere is another pathway for chemical pollution to reach the oceans. Air pollution carries various substances, such as carbon dioxide, nitrogen, and sulfur, into the ocean. Atmospheric pollution contributes to ocean acidification, which reduces seawater pH and negatively affects marine organisms. The increasing levels of carbon dioxide in the atmosphere due to climate change further exacerbate this issue.

Nutrient Pollution

Nutrient pollution, primarily from agricultural runoff, can lead to harmful algal blooms. Excessive growth of algae can smother and damage sensitive coral reefs, reducing biodiversity and coral health. Additionally, the decomposition of algal blooms consumes oxygen in coastal waters, creating hypoxic conditions that are detrimental to marine life.

Toxins

Toxic chemicals, such as pesticides, heavy metals, and persistent organic pollutants like PCBs and DDT, can enter marine ecosystems and accumulate in the food chain. These toxins can cause mutations, diseases, and reproductive issues in marine organisms, posing a threat to their health and survival.

Emerging Contaminants

Contaminants of Emerging Concern (CECs) are pollutants found in water bodies that may have ecological and human health impacts but are often unregulated. These include agricultural chemicals, runoff from urban areas, household products, and pharmaceuticals. CECs are increasingly detected in treated wastewater and can build up in the tissues of marine life, potentially causing harm.

Noise Pollution

Underwater noise pollution, mainly from shipping and industrial activities, disrupts the natural behaviours of marine organisms, especially those that rely on sound for communication and navigation, such as whales and dolphins. It can lead to altered migration routes, impaired communication, and stress-related behavioural changes in these species.

Eutrophication

Harmful algal blooms

Excessive plant and algal growth can lead to the formation of dense blooms of noxious, foul-smelling phytoplankton. These blooms can reduce water clarity and harm water quality, limit light penetration, and lower the success of predators that rely on light to catch prey. Certain types of algae can also produce toxins that affect human and animal health, causing mortalities of fish, birds, marine mammals, and even humans through the consumption of contaminated fisheries.

Ocean acidification

As the excess algae and plant matter eventually decompose, they produce large amounts of carbon dioxide, which lowers the pH of seawater—a process known as ocean acidification. Acidification slows the growth of fish and shellfish and can prevent shell formation in bivalve mollusks, reducing the catch for commercial and recreational fisheries.

Hypoxia and dead zones

The decomposition of algae and plant matter also consumes oxygen, creating hypoxic or anoxic "dead zones" that lack sufficient oxygen to support most organisms. These environments can trigger coral bleaching events, leading to increased damage and decreased recovery capacity of corals. Fish and other mobile marine species either die or leave the area in search of oxygenated waters.

Food web disruption

Economic impacts

Noise pollution

Anthropogenic noise, caused by human activities such as shipping, seismic surveys, explosions, construction, and sonar devices, has made the ocean a loud and chaotic environment, which is extremely damaging to marine life. Marine mammals such as whales, dolphins, and porpoises are particularly vulnerable to noise pollution, as they depend heavily on sound for various purposes.

The impacts of noise pollution on marine life are species-specific and depend on factors such as the intensity and frequency of the noise, as well as the distance from the noise source. While some studies have found little to no impact of certain types of noise on some species, the overall understanding of noise pollution's effects is still limited, and further research is needed.

Light pollution

ALAN interferes with the natural light cues that marine organisms have evolved to adapt to over millions of years. These cues include natural light intensity and patterns, such as the light from the moon and stars, and the daily and seasonal cycles of light and dark. Many marine organisms rely on these cues for essential activities such as feeding, schooling, migration, reproduction, and camouflage.

For example, zooplankton, which play a crucial role in aquatic food chains, typically migrate vertically in the water column during the day to avoid surface predators and feed on phytoplankton at night. ALAN disrupts this behaviour by illuminating the environment at night, leading to a decrease in the number of zooplankton individuals migrating and a proliferation of microalgae on the water surface. This, in turn, can have far-reaching consequences for aquatic ecosystems, including changes in prey-predator relationships and impacts on food chains and water quality.

Another example of the effects of ALAN is the impact on sea turtles. Adult female sea turtles avoid laying their eggs on lit beaches, and the lights from coastal cities confuse and disorientate newly hatched turtles, leading them away from the ocean and towards their deaths.

ALAN also affects coral reefs. Corals release sperm and eggs based on the light cycle of the moon, and ALAN can trigger corals to spawn at unideal times, reducing reproductive success.

To minimise the impacts of ALAN on marine life, it is essential to reduce excess lighting. This can be achieved by:

• Reducing the number of lights and the intensity of lighting.
• Reducing lighting during dawn and dusk, when many biological processes occur.
• Installing limited-angle lights or shielding lights to prevent light spillage.
• Using red light, which attenuates faster in water and is less detectable by marine organisms.
• Implementing "Lights Out" campaigns, where lights are turned off at night to benefit migratory birds and marine life.
• Creating Dark Sky Reserves, which help preserve natural light cycles.

Frequently asked questions