Air Pollution: Killing Life Under Water

The ocean is a vital resource, covering 70% of the Earth's surface and driving global systems that make the planet habitable for humans. Oceans provide key natural resources, including food, materials, and energy, and act as the planet's greatest carbon sink, absorbing about 30% of the carbon dioxide produced by humans. However, marine pollution, largely from land-based sources, is reaching alarming levels, with over 17 million metric tons of plastic clogging the ocean in 2021. This pollution has severe consequences for marine life and ecosystems, threatening their survival and disrupting the food web. Eutrophication, acidification, ocean warming, and overfishing further contribute to the deteriorating health of our oceans. To protect life below water, swift and coordinated global action is imperative, including increasing funding for ocean science, intensifying conservation efforts, and addressing the impacts of human-induced pressures.

Eutrophication, acidification, warming, and pollution are worsening ocean health

Eutrophication, acidification, warming, and pollution are all worsening ocean health, with far-reaching consequences for marine life, human health, and the global economy.

Eutrophication is a process that begins with an overabundance of nutrients, such as fertilizers and sewage, entering estuaries and coastal waters. This excess of nutrients causes a chain reaction, starting with an explosion of algae growth, which blocks sunlight and leads to the death of other plants. As the plants and algae eventually die and decompose, they produce large amounts of carbon dioxide, lowering the pH of seawater—a process known as ocean acidification. Acidification slows the growth of fish and shellfish and can even prevent shell formation in certain mollusks, leading to reduced catches for fisheries and more expensive seafood. Eutrophication has had significant economic impacts, with commercial shellfisheries losing millions of dollars annually and facing the threat of losing vital seagrass beds.

Ocean acidification is a global threat that is fundamentally changing the chemistry of the world's oceans. The oceans absorb carbon dioxide from the atmosphere, which helps regulate atmospheric concentrations but has detrimental effects on ocean life, particularly shellfish and other organisms that rely on calcium carbonate structures. Ocean acidification weakens coral structures and makes it difficult for shellfish to build and maintain their shells. This process also creates conditions that are favorable for harmful algal blooms, which can produce toxins that sicken fish and marine mammals and harm humans who consume contaminated seafood.

Ocean warming is another critical issue, with about 90% of global warming occurring in the ocean. This warming leads to thermal expansion, contributing to rising sea levels, and has already resulted in the most recent decade being the ocean's warmest since the 1800s. Ocean warming also contributes to the accelerated melting of Earth's major ice sheets and the intensification of hurricanes.

Pollution of the oceans is widespread and worsening, with more than 80% arising from land-based sources. It is a complex mixture of toxic metals, plastics, petroleum, industrial wastes, pesticides, fertilizers, pharmaceuticals, and sewage. Ocean pollution has severe impacts on human health, as it expands the geographic range of marine pathogens and introduces land-based microorganisms into the oceans. It is also responsible for enormous economic losses, with the shellfish industry being particularly vulnerable to the effects of pollution and acidification.

Marine pollution is reaching extreme levels, with an average of 13,000 plastic pieces per sq km

Marine pollution is a pressing issue, with plastic waste reaching every corner of the world's oceans. The average amount of plastic pollution is staggering, with an estimated 13,000 plastic pieces per square kilometre. This figure is based on data collected from 2007 to 2013 across all five subtropical gyres and extensive coastal regions, including the North Pacific, North Atlantic, South Pacific, South Atlantic, Indian Ocean, Bay of Bengal, Australian coasts, and the Mediterranean Sea.

The sources of this pollution are varied, but Asia is the leading contributor, with China alone accounting for 2.4 million metric tons of mismanaged plastic waste. The top ten emitters of oceanic plastic pollution are China, Indonesia, the Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh. These countries contribute to 90% of the plastic that ends up in the world's oceans, primarily through rivers such as the Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and Mekong.

The impact of this pollution is devastating for marine life. It is estimated that over 400,000 marine mammals, including an estimated 100,000 sea turtles and other marine mammals, perish annually due to plastic pollution in the oceans. Marine organisms become entangled in discarded fishing equipment, such as ghost nets, and other plastic packaging materials, causing severe lacerations and ulcers. Additionally, the ingestion of plastic debris has been observed in at least 267 different animal species, causing internal harm.

The incineration of plastic products further exacerbates the problem by releasing toxins and black carbon into the air, which are then consumed by ocean waters. This contributes to climate change and affects the ecosystems within the oceans. Plastic pollution also affects humans, as consuming fish that contain these toxins can lead to an increase in cancer, immune disorders, and birth defects.

Overall, the extreme levels of marine pollution, with an average of 13,000 plastic pieces per square kilometre, pose a significant threat to marine life, ecosystems, and human health. Addressing this issue requires global efforts to reduce plastic waste and improve waste management practices.

Overfishing has led to the depletion of over one-third of global fish stocks

Oceans are the planet's life support system, providing water, food, and regulating the weather. However, human activities have severely impacted marine ecosystems through pollution and overfishing. One of the significant concerns is the depletion of global fish stocks due to overfishing, which has led to the endangerment of various marine species and disrupted the livelihoods of millions dependent on marine resources.

Overfishing occurs when vessels catch fish at a rate faster than stocks can replenish. The practice has severe ecological and economic repercussions. It disrupts the marine food web, leading to the loss of other important marine life, including vulnerable species like sea turtles, corals, and even some endangered species. The impact extends beyond the marine environment, as billions of people worldwide rely on fish as a primary source of protein.

In 2017, one-third (34%) of assessed global fish stocks were overfished, according to the Food and Agriculture Organization of the United Nations. This issue is closely tied to bycatch, the unintended capture of non-target species, resulting in the needless loss of billions of fish and hundreds of thousands of sea turtles, cetaceans, and marine mammals. Overfishing also has detrimental effects on shark populations, with more than one-third of sharks, rays, and chimaeras now at risk of extinction.

The decline in fish stocks is evident in historical data. For example, records from Eastern Canada show that the cod catch peaked in 1968 before collapsing and leading to a dramatic decline. Similarly, bottom trawling, a dominant fishing method in some regions, has seen a significant reduction in Europe and Japan due to concerns about wild fish stock depletion. While these regions have witnessed a decrease, bottom trawling has intensified in China and India since the 1980s, contributing to the overall depletion of global fish stocks.

To address overfishing, various measures have been implemented, including the ban on bottom trawling in deeper water below 800 meters by the European Commission in 2016. Additionally, organizations like the WWF are working with stakeholders to reform fisheries management, focusing on sustainable practices that conserve ecosystems and sustain livelihoods. However, with the continued increase in demand for seafood, it is essential to address the root causes of overfishing and implement effective conservation measures to protect marine life and the livelihoods of those dependent on the fishing industry.

Oceans absorb about 30% of carbon dioxide produced by humans

Oceans play a crucial role in mitigating the impact of human-induced carbon dioxide emissions by absorbing approximately 30% of the carbon dioxide (CO2) released into the atmosphere. This absorption is driven by a massive carbon pump, which has a significant impact on the global climate and food production. The ocean holds 60 times more carbon than the atmosphere, and its role as a carbon sink helps to offset emissions in the global carbon budget.

The absorption of carbon dioxide by the oceans has far-reaching consequences for marine life and the Earth's climate. When CO2 dissolves into seawater, it triggers a series of chemical reactions, leading to an increase in hydrogen ion concentration. This results in a decrease in the ocean's pH level, making the water more acidic. This process, known as ocean acidification, has already impacted many ocean species, particularly those that rely on calcium and carbonate from seawater to build shells and skeletons, such as oysters and corals.

The intricate dynamics of the marine carbon cycle are not yet fully understood. Recent research has highlighted the potential significance of zooplankton, tiny animals near the base of the ocean food chain, in modelling this cycle accurately. Differences in assumptions about the abundance and behaviour of zooplankton and phytoplankton across models contribute to uncertainties in predicting the precise impact of the marine carbon cycle on the global climate.

It is worth noting that the capacity of the ocean as a carbon sink is not static. The size of the ocean carbon sink has changed in the past, and even minor alterations can significantly influence the Earth's climate. For instance, a slight increase in atmospheric CO2 due to human activities like burning fossil fuels and deforestation can lead to a corresponding rise in the amount of carbon dioxide absorbed by the ocean, further intensifying ocean acidification.

While the ocean's absorption of carbon dioxide helps to temporarily缓 alleviate the effects of human emissions, it is not a long-term solution. The increasing acidity of the ocean threatens the delicate balance of marine ecosystems, and the potential consequences for the planet and human civilization are profound. Addressing the root causes of carbon dioxide emissions and transitioning to more sustainable practices are imperative to safeguard the health of the oceans and the planet as a whole.

Oceans provide key natural resources, including food, medicines, and biofuels

Oceans are a vital source of key natural resources that support human life, including food, medicines, and biofuels.

Food

Oceans provide a significant source of food for human consumption. Fish, in particular, are a major food resource, with various species such as cod, herring, menhaden, and pollock being commonly consumed. However, the availability of fish in the oceans fluctuates due to natural causes and human activities, leading to concerns about overfishing and the need for sustainable fisheries management. Additionally, a portion of the fish caught are used for purposes other than direct consumption, such as fishmeal, fish oil, and fish paste, further highlighting the importance of responsible ocean resource utilization.

Medicines

The ocean is a promising source of novel medicines. Marine invertebrates, including sponges, tunicates, and some molluscs, produce a diverse range of substances with potential medicinal applications. For example, Ecteinascidin, extracted from tunicates, is being tested for the treatment of breast and ovarian cancers. As the demand for new medicines increases, researchers are turning to the ocean, as marine invertebrates have shown to produce more antibiotic, anti-cancer, and anti-inflammatory substances than terrestrial organisms.

Biofuels

Marine biofuels are an essential component of reducing emissions in the maritime transport sector, which accounts for about 3% of global carbon dioxide emissions. These biofuels are produced using various feedstocks and technologies, resulting in energy-dense fuels that can power large vessels on global voyages. With a lower carbon footprint than petroleum-based fuels, marine biofuels can help lower emissions and promote energy security. Organizations like the U.S. Department of Energy's Bioenergy Technologies Office (BETO) actively support research and development in this area, aiming to reduce emissions and build a stable economy for the production and use of marine biofuels.

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