Plastic Pollution's Impact On Coral Reefs: A Deadly Threat

Coral reefs are among the most endangered habitats on Earth, and plastic pollution is a significant contributor to this. Plastics are produced on a massive scale worldwide and degrade slowly, breaking down into microplastics—tiny, invisible particles that can cause severe harm to corals. The presence of plastic significantly increases the likelihood of disease in corals, blocking sunlight and oxygen and providing a pathway for harmful pathogens to enter. The ingestion of plastic by corals can also lead to a false sense of fullness, resulting in reduced feeding on nutritious food. With plastic waste accumulating in oceans and the associated dangers it poses to corals, urgent action is required to reduce plastic pollution and protect these vital ecosystems.

Plastic increases the chance of coral disease

Plastic pollution is a pressing issue for coral reefs, which are already vulnerable to climate change and other human activities. Research has shown that plastic significantly increases the likelihood of coral disease. When corals come into contact with plastic, the risk of disease rises from 4% to 89%. This drastic increase is influenced by several factors, which are discussed below.

Firstly, plastic debris can stress coral through light deprivation. Coral relies on light for survival, and plastic can block sunlight from reaching it. This creates low-light and low-oxygen conditions, which are ideal for microbes that cause diseases such as black band disease, resulting in complete tissue degradation.

Secondly, plastic can abrade and tear the surface of the coral, creating openings for pathogens to enter and cause infection. The presence of plastic provides a foothold for these pathogens to invade and colonise, promoting the growth and spread of harmful microorganisms.

Thirdly, plastic can carry and transport harmful pathogens into coral reefs. The plastic itself can become contaminated with bacteria, fungi, and other disease-causing organisms. When corals ingest or come into contact with this plastic, they are exposed to these pathogens, increasing the risk of infection.

Finally, plastic can impact the coral's ability to feed and grow. Corals may ingest microplastics, which can block their digestive tracts and create a false sense of fullness, leading to malnutrition and reduced growth.

The combination of these factors contributes to the increased likelihood of coral disease when plastic is present. The impact of plastic pollution on coral reefs underlines the urgent need to reduce plastic waste and improve waste management practices to protect these valuable and vulnerable ecosystems.

Plastic promotes the growth of harmful pathogens

Plastic pollution is a major threat to coral reefs, and one of the ways in which it does so is by promoting the growth of harmful pathogens.

Firstly, plastic waste can block sunlight and oxygen from reaching the coral. Sunlight and oxygen are both crucial for the survival of coral reefs. When plastic settles on coral, it creates low-light and low-oxygen conditions, which are ideal for the growth of harmful microbes. For example, these conditions are conducive to the growth of microbes that cause black band disease, which results in complete tissue degradation.

Secondly, plastic can carry harmful pathogens and transport them into coral reefs, thereby promoting the growth and spread of disease. The abrasiveness of plastic creates cuts and openings on the surface of corals, providing an entry point for infections. The protective skeleton of the coral is torn, leaving the coral vulnerable to infections from pathogens in the surrounding environment. Furthermore, the slow regrowth of coral tissue means that the coral remains vulnerable for an extended period.

Thirdly, plastic waste can serve as a vector for diseases to flourish. Certain pathogens, such as the bacteria that trigger outbreaks of white syndrome, are known to colonize plastic surfaces. Thus, plastic can act as a carrier for pathogens, facilitating their entry into coral reefs and increasing the risk of disease outbreaks.

The presence of plastic in coral reefs not only promotes the growth of harmful pathogens but also deprives corals of essential sunlight and oxygen, creating conditions that favor the proliferation of disease-causing microorganisms. The abrasiveness of plastic further exacerbates the problem by creating wounds that provide an entry point for infections. The combination of these factors significantly increases the vulnerability of coral reefs to diseases and infections.

Plastic breaks down into microplastics that enter our food chain

Plastic pollution is a pressing issue for coral reefs, and the breakdown of plastic waste into microplastics exacerbates the problem. Microplastics, measuring less than 5mm, are the result of the degradation of larger plastic items, facilitated by sunlight and heat. This process causes chemical reactions in the plastic, leading to the disintegration of its large polymer molecules.

These microplastics are hazardous to coral reefs and the wider marine ecosystem. They permeate the water column, rather than floating on the surface, and are often consumed by fish and other marine organisms, including corals. The ingestion of microplastics by corals may be intentional, as they can be attracted to the chemical compounds in the plastic. This behaviour can have detrimental consequences, as the plastics can induce a false sense of fullness, leading to reduced feeding on nutritious food sources and subsequent negative impacts on growth and survival.

Additionally, microplastics can block the digestive tracts of corals and cause internal damage. They also act as magnets for oily pollutants and toxic chemicals, which are then transferred to the corals and other marine life. These toxins can accumulate in the corals, further jeopardising their growth, reproduction, and survival. The toxins are then passed up the food chain, including to humans, through a process called biomagnification.

The impact of microplastics extends beyond the coral reefs themselves. They can harm oxygen-producing bacteria, such as Prochlorococcus, which are vital for the production of oxygen in the ocean. Research has shown that exposure to plastic leachate, or "tea", can result in significant population losses and reduced photosynthesis rates in these bacteria.

The breakdown of plastic into microplastics is a critical issue that affects not only coral reefs but also the wider marine environment and the food chain that sustains human life. Addressing this issue requires a multifaceted approach, including reducing plastic usage, improving recycling practices, implementing legislation to limit harmful chemical additives, and investing in chemical removal technologies to restore ocean health.

Plastic waste makes corals more vulnerable to potentially fatal diseases

Plastic waste is a serious threat to coral reefs, making them more susceptible to fatal diseases. A study by Cornell University in Ithaca, New York, found that the likelihood of disease on coral reefs impacted by plastic pollution was significantly higher than on those that were plastic-free. The study surveyed over 150 reefs across the Asia-Pacific region, examining the health of more than 124,000 corals. It was discovered that reefs free from plastic waste had only a 4% chance of being diseased, while those impacted by pollution were at an 89% risk.

Plastic pollution can make corals more vulnerable to disease in several ways. Firstly, plastic debris can physically damage corals by abrading and tearing their delicate tissues, creating openings for pathogens to invade. This damage can also cause infections, further compromising coral health. Secondly, plastic can block sunlight from reaching the corals, creating low-light and low-oxygen conditions that are ideal for the growth of harmful microbes. The presence of plastic provides an ideal environment for these disease-causing organisms to flourish, increasing the risk of coral disease.

Additionally, plastic waste can act as a vector for pathogens, carrying and transporting harmful microorganisms into coral reefs. The low-light and low-oxygen conditions created by plastic settlement, along with the physical damage caused by hard plastic debris, provide the perfect environment for microbes to thrive. This combination of factors increases the likelihood of disease outbreaks in coral reefs impacted by plastic pollution.

The impact of plastic pollution on coral health is not limited to physical damage. Plastic debris can also leach toxic chemicals, further compromising coral health. These toxins can accumulate in corals, affecting their growth, reproduction, and survival. The presence of plastic provides a means for these toxic chemicals to enter the coral ecosystem, exacerbating the negative effects of plastic pollution on coral reefs.

The study by Cornell University also found that certain types of coral, such as staghorn and branching corals, were more susceptible to the effects of plastic pollution. These structurally complex corals were found to be eight times more likely to become entangled in plastic waste. This is particularly concerning as these corals provide essential habitats and refuges for juvenile marine life, and their loss could have far-reaching consequences for the diversity and health of marine ecosystems.

Plastic blocks sunlight from reaching coral

Coral reefs are in danger due to plastic pollution, which is causing them to sicken and die. A four-year study of 159 reefs in the Pacific Ocean found that reefs in Australia, Thailand, Indonesia, and Myanmar were heavely contaminated with plastic. The plastic clings to the coral, abrading and tearing open the coral's skin, allowing infections to start.

Drew Harvell, a senior author at Cornell University, notes that plastic can harm coral in at least two ways. The first is through abrasion, and the second is by blocking sunlight from reaching the coral.

Sunlight is essential for coral health. Corals have a symbiotic relationship with algae called zooxanthellae; the corals provide habitat for the zooxanthellae, and the zooxanthellae provide nutrition through photosynthesis. By blocking sunlight, plastic hampers the ability of zooxanthellae to photosynthesize, thereby reducing the availability of nutrients for the coral. This, in turn, can lead to coral bleaching, a condition that further increases the susceptibility of corals to disease.

The risk of disease in corals in contact with plastic increases significantly, with studies showing an increase from 4% to 89% when corals are draped in plastic. The more structurally complex and spikey the coral species, the more likely they are to be affected by plastic.

The impact of plastic pollution on coral reefs underlines the urgent need for effective plastic waste management to protect these valuable ecosystems and the biodiversity they support.

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