Ocean Pollution: Impacting Seafood, Our Health And Planet

Ocean pollution is a complex mixture of toxins that directly affects human and ecosystem health. It is a growing problem that is caused by human activities, with more than 80% of ocean pollution coming from land-based sources. The toxins enter the human body mainly through the consumption of contaminated seafood.

The toxins in the ocean include mercury, plastic waste, manufactured chemicals, petroleum wastes, agricultural runoff, and biological threats, like harmful algal blooms. These toxins can cause a wide range of health issues, such as cardiovascular disease, developmental and neurobehavioral disorders, metabolic disease, immune dysfunction, endocrine disruption, and cancers.

The key to preventing ocean pollution is to target the most important pollution sources through laws, policies, technology, and enforcement actions. Banning coal combustion and single-use plastics, controlling coastal pollution, and expanding marine protected areas are some of the recommended actions.

Mercury pollution: Mercury is released from coal combustion and small-scale gold mining. It can cause brain damage and increase the risk of cardiovascular disease and dementia

Ocean pollution has contaminated seafood, with far-reaching consequences for both marine life and humans. One of the most pressing issues is mercury pollution, which is released from coal combustion and small-scale gold mining operations. Mercury is a potent neurotoxin that poses significant risks to human health, including brain damage and an increased likelihood of cardiovascular disease and dementia.

Small-scale gold mining, also known as artisanal mining, has been a common practice since the California Gold Rush of the mid-1800s and continues today in places like Peru. This process involves using mercury to extract gold from sediment pumped from riverbeds. The mercury binds to the gold, forming an amalgam that is then burned off, releasing mercury vapour into the atmosphere. This vapour can travel long distances and eventually settles onto land or water through rainfall or dust particles.

The released mercury ends up in the environment in two primary forms. Firstly, tailings, or waste material, can directly contaminate nearby land and aquatic ecosystems. Secondly, mercury vapour released during the burning process enters the atmosphere. Once in the environment, microbes convert mercury into methylmercury, a more toxic form that accumulates in fish and other organisms, leading to dangerous concentrations in animals higher on the food chain, including humans.

Methylmercury, a neurotoxin, can cause severe central nervous system damage, resulting in sensory and motor deficits, as well as behavioural impairments. Consuming fish with high mercury levels can lead to mercury toxicity in humans, causing chronic fatigue, dizziness, and loss of appetite. More alarmingly, mercury toxicity can lead to cognitive decline and increase the risk of Alzheimer's disease, cardiovascular disease, and dementia.

The impact of mercury pollution on seafood and, consequently, human health, underscores the urgency of addressing ocean pollution. While coal combustion and small-scale gold mining are significant contributors to mercury pollution, it is essential to recognise that mercury can also enter the ocean through industrial runoff and coal power plant wastewater. The complex and far-reaching effects of mercury pollution on seafood highlight the need for stricter regulations and a more sustainable approach to human activities that impact our oceans.

Plastic pollution: Plastic waste kills marine life and breaks down into toxic microplastics that can be ingested by humans

Plastic pollution is one of the most significant contributors to ocean pollution. Plastic waste in the ocean kills marine life and breaks down into toxic microplastics that can be ingested by humans through seafood consumption.

Plastic waste in the ocean takes hundreds or even thousands of years to degrade. During this time, it can entangle and trap marine animals, leading to starvation, injury, and increased vulnerability to predators. Discarded fishing nets can also smother and break coral reefs, disrupting their healthy growth. As plastic waste breaks down into smaller pieces, it becomes increasingly difficult to retrieve from the ocean.

Microplastics, or plastic particles smaller than 5mm, are often consumed by marine animals, mistaking them for food. These microplastics can adsorb toxins, which then transfer to the fatty tissues of the organisms that ingest them. This process is known as bioaccumulation and can result in toxic chemical concentrations in the bodies of marine organisms higher up the food chain, such as apex predators.

When humans consume seafood contaminated with microplastics, they are exposed to these toxic chemicals. While the health effects of microplastics in humans are still being studied, there is evidence to suggest that they can cause oxidative stress, inflammatory responses, DNA damage, and cytotoxicity. The impact of microplastics on human health is a growing concern, especially considering the nutritional importance of seafood consumption.

To address the issue of plastic pollution in the ocean, it is essential to focus on prevention and proper waste management. This includes reducing plastic leakage into the environment, making plastics less toxic, and promoting reuse, repurposing, and recycling. Beach cleanup programs and extended producer responsibility initiatives are also important steps towards mitigating the impact of plastic pollution on marine life and human health.

Agricultural pollution: Agricultural runoff can cause harmful algal blooms, which produce toxins that can cause neurological damage and death

Agricultural pollution is a significant contributor to ocean pollution, with far-reaching consequences for aquatic ecosystems and human health. One of the main issues is agricultural runoff, which can lead to harmful algal blooms (HABs). These blooms are characterised by a sudden and excessive accumulation of microalgae, particularly cyanobacteria, which produce toxins that are dangerous to both humans and aquatic life.

Agricultural runoff often contains high levels of nutrients such as nitrogen and phosphorus, which act as fertilisers and promote the growth of algae and bacteria. When these excess nutrients enter waterways, they cause a process called eutrophication, leading to an overgrowth of algae. This, in turn, results in the depletion of oxygen in the water, creating "dead zones" where nothing can survive.

The toxins produced by HABs can have severe impacts on human health. They can cause a range of health issues, including mild skin rashes, throat irritation, gastroenteritis, neurological damage, and even death. Cooking or boiling contaminated seafood does not destroy these toxins, and they can accumulate in the human body over time. Populations that rely heavily on seafood are at particular risk of long-term health effects from frequent, low-level exposures to HAB toxins.

The economic impacts of HABs are also significant. Fisheries and recreational areas may be forced to close or reduce operations, resulting in substantial revenue losses. Additionally, the costs of water quality monitoring, management, and treatment can be high.

To mitigate the risks associated with HABs, a multifaceted approach is necessary. This includes implementing better farming practices, such as adopting regenerative farming techniques that improve soil health and reduce nutrient-packed runoff. It is also crucial to improve water treatment and filtration technologies to remove HAB organisms and their toxins from water sources effectively.

Overall, agricultural pollution, and specifically agricultural runoff, has severe ecological, economic, and public health consequences. Addressing this issue requires a comprehensive and sustainable approach that balances the needs of agricultural productivity with the protection of the environment and public health.

Sewage: Sewage can increase the frequency of harmful algal blooms and spread life-threatening infections

Sewage can enter the ocean through runoff from cities and industrial buildings, and it can increase the frequency of harmful algal blooms. Sewage contains nutrients such as nitrogen and phosphorus, which can cause an overgrowth of algae, triggering an event called an algal bloom. These blooms can produce toxins that are harmful to both people and animals.

Sewage can also spread life-threatening infections. Seafood can become contaminated with pathogens when sewage is discharged into the water where the seafood is harvested. Contamination can also occur during the handling, processing, or preparation of seafood.

Some of the pathogens that can be spread through sewage include:

• Vibrio organisms
• Salmonellae
• Shigella species
• Clostridium botulinum
• Staphylococcus aureus
• Hepatitis A virus
• Norwalk and Norwalk-like viruses
• Non-A, non-B hepatitis virus

Climate change: Warmer sea temperatures can increase the number of marine microbes that can cause disease

Warmer sea temperatures can increase the number of marine microbes that can cause disease.

Marine microbes, such as bacteria, are responsible for many crucial biogeochemical functions, including fixing carbon and nitrogen, recycling nutrients and dissolved organic matter, and degrading biomass. Climate change has led to a steady increase in ocean temperatures, and this has a direct impact on the distribution and growth of marine microbes.

Research has shown that warmer seawater temperatures universally favour slower-growing bacterial taxa. This is because higher temperatures increase the relative abundance of slower-growing bacteria with low ribosomal RNA (rRNA) gene operon copy numbers. This relationship between temperature and the abundance of slower-growing bacteria holds across seasons, latitudes, and depths.

The impact of temperature on bacterial communities is particularly significant because bacteria are a vital part of the marine food web. They are the primary decomposers of organic matter, and their activity affects the availability of nutrients for other organisms in the ecosystem. Additionally, bacteria are a food source for other microorganisms, including protists and larger zooplankton.

The increase in slower-growing bacteria due to warmer temperatures can have both positive and negative effects on the marine ecosystem. On the one hand, slower-growing bacteria tend to be more efficient, which can lead to increased degradation of organic matter and improved nutrient cycling. On the other hand, some slower-growing bacteria may be pathogens that can cause disease in humans and other marine organisms.

One example of a marine bacterium that can cause disease is Vibrio. Vibrio bacteria are naturally present in marine environments and tend to flourish in higher concentrations during warmer seasons. They can cause illnesses in humans, ranging from mild cramps and nausea to severe infections that can lead to death. The increase in Vibrio bacteria due to rising sea temperatures has been linked to a rise in Vibrio-related illnesses along the US Atlantic Coast and in Northern Europe.

In summary, climate change and warmer sea temperatures can have significant impacts on the distribution and abundance of marine microbes, including potential increases in disease-causing microbes. These changes can have both ecological and human health implications, highlighting the importance of understanding and mitigating the effects of climate change on our oceans.

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