Chemical Pollution's Impact On Coral Reefs

Coral reefs are indispensable ecosystems that support a diverse range of marine life and provide significant economic and environmental value. However, they face an array of threats, including chemical pollution, which jeopardizes their survival. Chemical pollution, originating from land-based sources, poses a significant risk to the health and existence of coral reefs. With the expansion of human populations and development in coastal areas, the increase in land-based pollution has detrimental effects on coral reef ecosystems. This paragraph will explore the impact of chemical pollution on coral reefs and highlight the importance of addressing this issue to protect these vital ecosystems.

Plastic pollution

Coral reefs are already one of the most endangered habitats on Earth due to climate change, but plastic pollution poses a further threat to their survival.

A four-year study by Cornell University found that plastic pollution is killing coral reefs from Thailand to Australia. The study surveyed 159 reefs in the Asia-Pacific region, finding billions of plastic items entangled in the reefs. The likelihood of disease increases from 4% to 89% when corals are in contact with plastic. Plastic debris stresses coral through light deprivation, toxin release, and anoxia, giving pathogens a foothold for invasion.

Plastic can abrade corals, creating openings in their surface that allow infections to start. It can also block sunlight from reaching the coral, which can lead to low-oxygen conditions that allow disease-causing bacteria to thrive. The more spikey the coral species, the more likely they are to snag plastic. Staghorn and branching corals, for example, were found to be eight times more likely to trap plastics.

Coral may also ingest microplastics, which can give them a false sense of fullness, leading to malnutrition. Microplastics can also block the gut and cause internal damage. They can carry pollutants and harmful microorganisms from the seawater and transfer them to the coral.

The impact of plastic pollution on coral reefs underlines the urgent need to reduce plastic production and waste.

Sewage discharge

One of the main issues with sewage is the high levels of nitrogen and phosphorus it contains. These nutrients cause excessive growth of algae, which then smothers coral reefs, blocking sunlight and depleting oxygen levels. This can lead to an imbalance in the entire ecosystem, as well as support the growth of pathogenic microorganisms that can cause disease in corals.

Sewage is also a breeding ground for bacteria, viruses, and other pathogens that can directly make corals sick. In addition, household and industrial chemicals found in sewage can be toxic and negatively impact coral reproduction and growth. These chemicals, such as pesticides, can affect coral reproduction, growth, and other physiological processes. They can also damage the symbiotic relationship between corals and algae, resulting in bleaching.

Furthermore, sewage can contain heavy metals, inorganic nutrients, pathogens, endocrine disruptors, suspended solids, and sediments, all of which can severely impair coral growth and reproduction. These components may also interact with each other to create synergistic effects, such as nutrients facilitating pathogen growth, and exacerbating the impacts of other non-sewage-based stressors.

The effects of sewage discharge on coral reefs highlight the importance of improving wastewater treatment infrastructure and enforcing stricter regulations on wastewater discharges. By investing in proper sewage treatment facilities, the amount of untreated wastewater entering marine environments can be significantly reduced, allowing coral reefs to recover and thrive.

Industrial pollution

One of the most pressing issues is plastic pollution, which is a growing problem for our oceans. Coral reefs are especially vulnerable to plastic debris, which can physically damage their structures, break branches, and impede their growth. Plastic can also act as a vector for pathogens, introducing diseases and contributing to widespread coral decline. Research has shown that coral reefs with plastic debris are 20 times more likely to be diseased than those without.

In addition to plastic pollution, industrial activities contribute to the release of toxic substances, including metals, organic chemicals, and pesticides. These pollutants are often found in industrial discharges, as well as in sunscreens, urban and agricultural runoff, mining activities, and landfill leachate. Pesticides, for example, can negatively impact coral reproduction, growth, and physiological processes. Similarly, herbicides can affect the symbiotic algae that corals depend on, damaging their partnership and resulting in coral bleaching.

Moreover, heavy metals such as mercury and lead, as well as organic chemicals like polychlorinated biphenyls (PCBs), oxybenzone, and dioxin, are suspected of impairing coral reproduction, growth rate, feeding, and defensive responses. These pollutants accumulate in the tissues of marine organisms, leading to long-term health issues and making it more challenging for corals to recover from other environmental stresses.

The impact of industrial pollution on coral reefs underscores the urgent need for stricter regulations on industrial wastewater discharges and better waste management practices. By addressing these issues, we can help protect and preserve these vital ecosystems for future generations.

Climate change

Coral reefs are highly sensitive to changes in their environment. When corals are stressed by higher water temperatures, they expel the symbiotic algae living in their tissues, which are responsible for their colour. This is known as coral bleaching. A spike of 1–2 °C in ocean temperatures sustained over several weeks can lead to bleaching, turning corals white. If corals remain bleached for a prolonged period, they will eventually die.

The Great Barrier Reef in Australia and the Northwestern Hawaiian Islands in the United States have experienced record-breaking bleaching, with devastating effects. The bleaching of the Great Barrier Reef in 2016 and 2017, for instance, killed around 50% of its corals.

Corals also cannot survive the increased frequency of bleaching events caused by global temperature rise. If temperatures continue to rise, bleaching events will increase in intensity and frequency. Scientists estimate that even those events that occur twice per decade can threaten the survival of corals.

The ocean absorbs carbon dioxide from the atmosphere, making it more acidic. This process is known as ocean acidification. The ocean has absorbed about 30% of the carbon generated by humans since the late 18th century, decreasing its pH level. A more acidic ocean means corals struggle to build their skeletons and form coral reefs, which protect coastlines from storms and provide habitats for thousands of marine species.

As water temperatures rise, many marine species are forced to move south to cooler habitats. This shift creates increased competition for food and shelter in cooler waters, threatening the entire ecosystem. For reef communities, the loss of marine life can have a devastating impact on local ecosystems, food sources, and industries such as tourism.

To protect coral reefs from climate change, urgent global action is needed to drastically and rapidly reduce greenhouse gas emissions. It is also important to strengthen key ecosystems like seagrass meadows, mangroves, and wetlands, which help absorb carbon dioxide from the atmosphere and play a key role in combating climate change by storing carbon.

Land-based pollution

Firstly, excess nutrients from agricultural and residential fertiliser use, sewage discharges, and animal waste can lead to eutrophication, causing decreased oxygen levels and enhanced algal growth on reefs. This algal growth can crowd out and smother corals, blocking sunlight and consuming oxygen needed for coral respiration. This can result in an ecosystem imbalance and even support the growth of pathogenic microorganisms, such as bacteria and fungi, that can harm corals.

Secondly, sedimentation from coastal development, deforestation, urban stormwater runoff, and agriculture can smother and bury corals, interfering with their ability to feed, grow, and reproduce. The sediment can also carry harmful pollutants, such as heavy metals and pesticides, further compromising water quality.

Thirdly, toxic substances, including metals, organic chemicals, and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, and landfill runoff, can affect coral reproduction and growth, and defensive responses. Pesticides, for example, can impact coral reproduction and growth, while herbicides can damage the symbiotic relationship between coral and algae, resulting in bleaching.

Finally, plastic pollution, including bags, bottles, fishing gear, and microplastics, is a catastrophic and growing problem for coral reefs. Plastic debris can physically damage and entangle coral structures, providing a vehicle for pathogens and introducing diseases. It also blocks sunlight from reaching the corals, hindering their ability to photosynthesise.

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