Water Pollution: Marine Life Under Threat

Water pollution is a pressing global issue, with pollution reaching every corner of the world. It is a problem that is largely caused by humans, with 80% of ocean pollution originating on land. Marine life is suffering from the effects of oil spills, plastic waste, chemical contamination, and nutrient pollution. Oil spills, for example, can suffocate marine animals by clogging their gills, while plastic waste is often mistaken for food and can cause suffocation, starvation, and drowning. Chemical contamination, such as heavy metals and pesticides, can cause deformities, reproductive issues, and even death in aquatic organisms. Nutrient pollution, caused by an excess of nitrogen and phosphorus, leads to oxygen depletion in the water, creating dead zones devoid of life. With marine ecosystems under threat, it is clear that water pollution has detrimental effects on marine life.

Oil spills

The effects of any oil spill depend on where it is spilled, where it goes, and what animals, plants, and people it affects. Most oils float, so creatures most affected by oil spills are animals found on the sea surface or shorelines, such as sea otters and seabirds. Seabirds are harmed and killed in greater numbers than other creatures during oil spills. They are affected when oil gets into their feathers, impairing their ability to fly or feed their young, and reducing their ability to maintain body temperature, which can lead to death by hypothermia. Dehydration and exhaustion are other causes of death for oiled seabirds.

Marine mammals, such as bottlenose dolphins, also spend a lot of time near the surface of the water, putting them at high risk during oil spills. They can be exposed to oil through breathing it in, eating oiled food, or swimming through it, all of which can lead to devastating health issues.

Oil can also smother some small species of fish or invertebrates, and kill fish eggs, and impair growth in young fish. Oil spills can also ignite or explode, and kill animals or plants that they touch. They are also dangerous to humans who breathe their fumes or get them on their skin.

Eelgrass meadows in the tidal zone are generally directly exposed to oil and die off in the first year of an oil spill. After the initial mortality in the first year, long-term effects of eelgrass are mixed.

Plastic pollution

Another consequence of plastic pollution is entanglement, which can cause loss of limbs, strangulation, and suffocation. Marine animals can become entangled in plastic bags, discarded fishing nets, and other plastic debris. This can lead to immobility, inability to feed, and, ultimately, death.

The breakdown of plastics into micro and nano particles has also led to their proliferation throughout the food web. Plastics have been found in fish and other organisms, indicating the presence of plastic pollutants in the human food chain. Furthermore, floating plastic debris has been shown to transport invasive marine species and accumulate pollutants, spreading them through ocean currents.

The impact of plastic pollution on marine life is widespread and severe, threatening the health and survival of numerous species. Addressing this issue requires a combination of improved waste management practices, reduced plastic production, and the adoption of strong national plans and compliance mechanisms to tackle plastic pollution effectively.

Eutrophication

Ocean acidification has detrimental effects on marine life, particularly shellfish and coral, as it impairs their ability to build shells. It can also impact the nervous systems of certain marine species, such as sharks and clownfish. Additionally, the decomposition of the excess algae and plant matter leads to a significant depletion of dissolved oxygen in the water, creating "dead zones" where waters are essentially devoid of life. These dead zones are characterized by hypoxic or anoxic conditions, meaning they lack sufficient oxygen to support most organisms.

The presence of eutrophication and dead zones has far-reaching consequences for marine ecosystems. For example, bivalve mollusk populations, including oysters, clams, and scallops, are impacted, as they play a crucial role in naturally reducing nutrient levels through their filter-feeding activities. Eutrophication also affects fisheries, as the reduced oxygen levels and impaired growth of shellfish and fish result in smaller harvests and more expensive seafood.

Furthermore, eutrophication can have indirect effects on other species within the ecosystem. As primary producers like plants and algae die off, the entire food chain is disrupted, leading to a reduction in food sources for higher trophic levels. This can result in population declines or even local extinctions of species that rely on these food sources. Additionally, the increased nutrient load that characterizes eutrophication can originate from human activities, such as improper waste disposal and runoff from farms and factories, highlighting the impact of human actions on the environment.

To address the issue of eutrophication, it is essential to focus on implementing sound agricultural and waste management practices. By reducing the input of excess nutrients into aquatic ecosystems, we can help mitigate the occurrence of eutrophication and its subsequent effects on marine life.

Marine debris

Injury and Death

Habitat Degradation

Non-native species may hitchhike on marine debris, travelling from one region to another. If these introduced species become invasive, they can severely impact an ecosystem by depleting food sources or destroying habitats.

Oxygen Depletion

As excess debris in the ocean degrades over time, it consumes oxygen, leading to a reduction in oxygen levels in the water. This depletion can result in the creation of "dead zones," where marine life struggles to survive due to the lack of oxygen.

Ingestion of Plastic

Marine animals often mistake plastic debris for food, leading to the ingestion of toxic substances. Plastic debris can accumulate in the digestive systems of marine organisms, impacting their health and potentially causing death. This issue is not limited to marine life, as birds, such as albatross, have also been found with plastic debris in their stomachs, passed on from their parents while feeding their chicks.

Chemical contamination

Marine life is facing an unprecedented threat from chemical contamination, a form of nutrient pollution caused by human activities. The use of fertilisers on farms, for example, leads to the runoff of chemicals into waterways that eventually flow into the ocean. This increases the concentration of chemicals such as nitrogen and phosphorus in the coastal ocean, promoting the growth of harmful algal blooms.

Algal blooms have severe consequences for marine life. Firstly, they reduce oxygen levels in the water, leading to eutrophication, a process by which marine plants and animals are suffocated, creating \"dead zones\" devoid of life. Certain algal blooms also produce neurotoxins that are harmful to a range of wildlife, from whales to sea turtles.

The excess nitrogen and phosphorus in seawater, caused by agricultural runoff, also contribute to oxygen depletion, creating more dead zones where marine life struggles to survive. This depletion is exacerbated by the breakdown of plastics in the ocean, which consumes oxygen.

Moreover, chemicals and heavy metals from industrial and municipal wastewater contaminate waterways, posing direct threats to aquatic life. These toxins reduce the lifespan and reproductive abilities of organisms and accumulate in the food chain as predators consume prey. For instance, tuna and other large fish have been found to contain high levels of toxins such as mercury.

The impact of chemical contamination extends beyond marine ecosystems, eventually reaching humans. Small organisms that ingest toxins are eaten by larger predators, including seafood that ends up on our plates. The accumulation of these toxins in human tissue can lead to long-term health issues, cancer, and birth defects.

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