Coral Reef Bleaching: Pollution's Devastating Impact

Coral reefs are disappearing fast, with water pollution, overfishing and coastal development taking their toll at a local level. Carbon pollution is the biggest threat to reefs worldwide, with record-breaking marine heatwaves causing mass coral bleaching. When water temperatures rise, corals become stressed and expel the marine algae living inside their tissues, called zooxanthellae. Zooxanthellae provide the coral with food and energy from the sun, allowing them to grow and reproduce. When corals expel this algae, a white skeleton is left behind, which is known as 'coral bleaching'. Herbicides and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and landfill runoff can also damage the partnership between symbiotic algae and coral, resulting in bleaching.

How pathogens from inadequately treated sewage can cause coral disease

Although rare, pathogens from inadequately treated sewage can cause coral disease. Coral disease occurs in healthy ecosystems, but the input of pathogen-containing pollution can exacerbate the frequency and intensity of disease outbreaks.

Bacteria and parasites from faecal contamination can cause disease in corals, especially if they are stressed by other environmental conditions. For example, when water temperatures increase due to climate change, corals become stressed and expel the marine algae living inside their tissues, called zooxanthellae. Zooxanthellae provide the coral with food and energy from the sun through photosynthesis, allowing them to grow and reproduce. When corals expel this algae due to stress, their white skeletons are revealed, and this is known as 'coral bleaching'.

Inadequately treated sewage can also contain toxic substances, including metals, organic chemicals, and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and landfill runoff. These toxic substances can affect coral reproduction, growth, and other physiological processes. For example, herbicides can damage the symbiotic relationship between algae and coral, leading to bleaching.

Additionally, water pollution, overfishing, and coastal development are taking a toll on coral reefs locally, while carbon pollution remains their biggest threat worldwide. Carbon pollution contributes to increased ocean temperatures, which is a primary cause of coral bleaching.

Therefore, pathogens from inadequately treated sewage can cause coral disease by introducing bacteria and parasites that take advantage of corals already stressed by other environmental factors, such as increased water temperatures and pollution.

How toxic substances found in industrial discharges can affect coral reproduction

Coral reefs are disappearing fast, with water pollution, overfishing and coastal development taking their toll at a local level, and carbon pollution threatening reefs worldwide.

Coral bleaching is caused by increased ocean temperatures, which are the result of carbon pollution and climate change. When the water is too hot for too long, the coral becomes stressed and expels the marine algae living inside its tissues, called zooxanthellae. Zooxanthellae provide the coral with food and energy from the sun, allowing them to grow and reproduce. When corals get stressed, they react by expelling this algae, leaving a white skeleton behind. This is known as 'coral bleaching'.

Toxic substances, including metals, organic chemicals and pesticides found in industrial discharges, can affect coral reproduction, growth, and other physiological processes. Herbicides, in particular, can affect the symbiotic algae (plants). This can damage their partnership with coral and result in bleaching.

Pesticides and herbicides are used in agriculture to kill pests and unwanted plants. When these chemicals are applied to crops or fields, they can be washed into nearby water bodies through runoff. From there, they can make their way into the ocean, where they can come into contact with coral reefs. Once in the ocean, these chemicals can be absorbed by corals, disrupting their normal functions and leading to bleaching.

How carbon pollution causes ocean temperatures to increase

The ocean absorbs excess heat and energy from the Earth's system, which is caused by rising greenhouse gas emissions. The ocean has absorbed about 90% of the heat generated by rising emissions. As the ocean warms, this leads to a number of effects, including ice-melting, sea-level rise, marine heatwaves, and ocean acidification.

The ocean has absorbed about 29% of global CO2 emissions since the end of the preindustrial era. In the last decade (from 2008-2017), we’ve dumped about 40 gigatons of emissions of heat-trapping gases each year from the burning of fossil fuels and land-use change.

CO2 concentrations drive rising temperatures and acidification. Projections show that by the end of this century, ocean surface waters could be more than twice as acidic as they were at the end of the last century if we do not reduce our carbon emissions.

Increasing emissions of greenhouse gases into the atmosphere from the burning of fossil fuels are causing changes in the ocean. These changes can alter which species of marine life thrive best in certain areas. For example, many fish have shifted their typical range as water temperatures rise.

How water pollution, overfishing and coastal development are taking their toll on coral reefs

Water pollution, overfishing and coastal development are taking their toll on coral reefs. Coral reefs are disappearing fast, with water pollution, overfishing and coastal development causing damage at a local level, while carbon pollution is the biggest threat to reefs worldwide.

Water pollution is a major contributor to coral reef bleaching. When corals are stressed by heat or pollution, they expel the marine algae living inside their tissues, called zooxanthellae. Zooxanthellae provide the coral with food and energy from the sun through photosynthesis, allowing them to grow and reproduce. When corals expel this algae, their white skeletons are revealed, a process known as 'coral bleaching'.

Coral reefs are also affected by pathogens from inadequately treated sewage, stormwater, and runoff from livestock pens. Although rare, bacteria and parasites from faecal contamination can cause disease in corals, especially if they are already stressed by other environmental conditions. Coral disease occurs in healthy ecosystems, but the input of pathogen-containing pollution can make disease outbreaks more frequent and intense.

Toxic substances, including metals, organic chemicals and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and landfill runoff, can also harm coral reefs. Pesticides can affect coral reproduction, growth, and other physiological processes. Herbicides, in particular, can affect the symbiotic algae (plants) that live inside coral tissues. This can damage their partnership with coral and result in bleaching.

Overfishing can also contribute to coral reef bleaching by removing key species that help to maintain the health of the reef. Additionally, coastal development can damage coral reefs through activities such as dredging and land reclamation, which can destroy reef habitats and increase sedimentation, smothering corals and reducing water quality.

How changes in water quality can cause coral bleaching

Coral reefs are disappearing fast, with water pollution, overfishing and coastal development taking their toll at the local level. Carbon pollution is the biggest threat to coral reefs worldwide.

Coral bleaching is a global crisis, caused by increased ocean temperatures due to carbon pollution and climate change. When the water stays too hot for too long, the coral becomes stressed and expels the marine algae living inside their tissues, called zooxanthellae. Zooxanthellae provide the coral with food and energy from the sun through photosynthesis, allowing them to grow and reproduce. When corals get stressed, from things such as heat or pollution, they react by expelling this algae, leaving a white skeleton behind. This is known as 'coral bleaching'.

Pathogens from inadequately treated sewage, stormwater, and runoff from livestock pens can also cause coral disease, especially if the corals are already stressed by other environmental conditions. Coral disease occurs in healthy ecosystems, but the input of pathogen-containing pollution can exacerbate the frequency and intensity of disease outbreaks.

Toxic substances, including metals, organic chemicals and pesticides found in industrial discharges, sunscreens, urban and agricultural runoff, mining activities, and landfill runoff can also affect coral reproduction, growth, and other physiological processes. Herbicides, in particular, can affect the symbiotic algae (plants). This can damage their partnership with coral and result in bleaching.

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