Pollution's Impact: Warmer Oceans And A Changing Climate

The ocean is a pivotal force of nature, covering 70-71% of the Earth's surface and making up 95% of the space available to life. It is a life-support system for the planet, regulating the climate and driving weather patterns. The ocean absorbs excess heat and energy from the Earth's atmosphere, and as a result, ocean temperatures are rising. This is largely due to the absorption of greenhouse gases, with the ocean absorbing about 90% of the heat generated by rising emissions. This has a direct impact on marine biodiversity, with coral reefs, for example, being damaged by warmer waters. Marine heatwaves have also become more frequent and intense, causing coral bleaching. Additionally, the ocean's absorption of carbon dioxide leads to ocean acidification, which further threatens marine life.

Ocean Acidification

The pH scale runs from 0 to 14, with 7 being neutral. The pH of the ocean is usually slightly basic, with an average of 8.1 to 8.2. However, due to the absorption of excess CO2, the ocean's pH has decreased to around 8.1, representing a 26% to 30% increase in acidity. This change in pH is significant because the pH scale is logarithmic, meaning a small change in pH represents a much larger change in acidity or basicity.

• Their shells and skeletons may dissolve more easily as the ocean becomes more corrosive with decreasing pH.
• When CO2 dissolves in seawater, the water chemistry changes, resulting in fewer carbonate ions available. These ions are essential building blocks for shells and skeletons, and their reduced availability directly impacts the survival of these organisms.

The impact of ocean acidification on corals is of great concern. Corals produce massive calcium carbonate structures called reefs, which provide habitat for many marine animals, including commercially important fish and shellfish species. Additionally, coral reefs are vital sources of food and medicine, protection from storms, and a focus of eco-tourism. Studies have shown that acidification impairs the ability of some calcifying plankton to build and maintain their shells, and increased larval mortality rates have been observed in several commercially important fish and shellfish species.

The rate of ocean acidification is accelerating, and scientists are working to understand its potential impacts on marine ecosystems and how these impacts may cascade through the marine food chain.

Coral Bleaching

Climate change is the leading cause of coral bleaching, with a warming planet leading to a warming ocean. Even a slight increase in water temperature, as little as 2 degrees Fahrenheit, can trigger coral bleaching. The increase in ocean temperatures causes stress in corals, leading them to expel the zooxanthellae. If the temperature remains high, the corals will not allow the algae to return, and they will eventually die. This process of coral bleaching has far-reaching consequences, as coral reefs are some of the most biodiverse ecosystems on the planet, supporting thousands of marine species.

Pollution is another significant contributor to coral bleaching. Land-based sources of pollution, such as coastal development, deforestation, agricultural runoff, and oil and chemical spills, can have detrimental effects on coral reefs. These pollutants can impede coral growth and reproduction, disrupt ecological functions, and cause disease and mortality in sensitive species. Additionally, increased nutrient levels from agricultural and residential fertiliser use, sewage discharges, and animal waste can lead to excessive algae growth, blocking sunlight and consuming oxygen needed by the corals for respiration.

The impacts of coral bleaching extend beyond the ecological realm and have significant economic implications as well. Coral reefs provide natural protection for coastal communities, acting as barriers that absorb the force of waves and storms. Without these natural defences, communities become more vulnerable to the impacts of climate change, such as sea-level rise and intensified storms. Additionally, reef tourism generates billions of dollars in revenue and supports thousands of jobs, all of which are jeopardised by the loss of vibrant marine ecosystems due to coral bleaching.

To address coral bleaching, it is crucial to tackle the root cause: climate change. This requires global, comprehensive, and immediate action to reduce carbon emissions. By transitioning to renewable energy sources, stopping deforestation, and implementing climate-smart policies, we can help protect coral reefs for future generations. Additionally, local actions such as reducing stormwater runoff, avoiding herbicides and pesticides, and supporting conservation efforts can also play a vital role in preserving these fragile ecosystems.

Marine Heatwaves

The ocean absorbs about 90% of the heat generated by rising emissions, and this has led to a rise in marine heatwaves, which have doubled in frequency and become more intense, extensive, and long-lasting. The majority of these heatwaves took place between 2006 and 2015, causing widespread coral bleaching and reef degradation. In 2021, nearly 60% of the world's ocean surface experienced at least one marine heatwave. These heatwaves are projected to become more frequent and intense, with a predicted increase of 20-50 times in frequency and 10 times in intensity by 2100. The Arctic and tropical regions are expected to be the most affected.

MHWs have far-reaching consequences for marine biodiversity and human societies. They can cause extreme weather events such as tropical storms and hurricanes, and disrupt the water cycle, leading to floods, droughts, and wildfires. They also impact industries such as aquaculture, fisheries, and tourism. For instance, MHWs have been linked to the death or reduced productivity of economically important species like lobster, snow crab, and scallops. Additionally, they can harm invasive alien species to spread, posing a threat to marine food webs.

To address the impacts of MHWs, governments must invest in nature-based solutions and significantly reduce fossil fuel emissions. Developing research capacity, improving prediction and warning systems, and implementing regional measures to build ocean resilience are crucial steps to protect communities and ecosystems from the detrimental effects of MHWs.

Atmospheric Pollution

One of the primary sources of atmospheric pollution affecting the oceans is the burning of fossil fuels. The increased concentration of greenhouse gases, such as carbon dioxide (CO2), in the atmosphere has led to the ocean absorbing about 90% of the excess heat generated by rising emissions. This has resulted in unprecedented cascading effects, including ice melting, sea-level rise, marine heatwaves, and ocean acidification.

Ocean acidification is a significant consequence of atmospheric pollution. As the ocean absorbs airborne CO2, chemical reactions occur, reducing seawater pH. This increased acidity has detrimental effects on marine organisms, such as coral reefs, and can disrupt the entire marine food chain. The pace of ocean acidification is accelerating, causing concern among the scientific community about its potential impacts on marine ecosystems.

In addition to CO2, the atmosphere also carries other pollutants that affect ocean health. Coal combustion, for example, releases mercury into the atmosphere, which eventually finds its way into the ocean. Mercury pollution has been linked to developmental issues and behavioural problems in children whose mothers consumed contaminated seafood during pregnancy. It also increases the risk of heart disease and dementia in adults.

Another significant contributor to atmospheric pollution is plastic waste. Single-use plastics, such as plastic bags and styrofoam containers, are often carried by the wind into the ocean, where they can take hundreds of years to biodegrade. These plastics break down into microplastics, which are ingested by marine organisms and can absorb toxic chemicals. While the full extent of the risks associated with microplastics is still unknown, they are believed to have harmful effects on both marine life and human health.

To address atmospheric pollution and its impact on ocean temperatures and health, global efforts are necessary. Implementing measures to reduce carbon emissions, transitioning to renewable energy sources, and banning single-use plastics are crucial steps towards mitigating the effects of atmospheric pollution on the world's oceans.

Oil Spills

The impact of oil spills goes beyond the immediate aftermath. Research has shown that toxic chemicals from oil spills remain in the ocean for years, sinking to the seafloor and poisoning the sediment. This contamination can affect marine animals throughout their lifecycles, impacting their breeding, reproduction, and growth rates. For example, females affected by oil may lay eggs with thinner shells, making them more vulnerable to breaking. Oil spills also disrupt ecosystems by reducing the availability and quality of food sources for marine life.

One of the most well-known oil spills occurred in April 2010 when the BP oil rig Deepwater Horizon exploded, releasing more than 134,000 barrels of oil into the Gulf of Mexico. This incident had devastating consequences, including the death of marine life and contamination of critical habitats. Another notable example is the Amoco Cadiz oil spill in 1978, which polluted about 321km of the French coast, leading to the death of millions of invertebrates and an estimated 20,000 birds.

The response to oil spills involves multiple strategies, including the use of booms, skimmers, and other tools to contain and remove the oil from the water surface. In some cases, controversial measures such as in situ burning or the use of dispersants may be considered. While natural processes like wind, waves, and microbes can help disperse and break down the oil, human intervention is crucial for effective and timely cleanup.

The effects of oil spills can be long-lasting and, in some cases, irreparable. They pose a significant threat to marine life and ecosystems, highlighting the importance of proper management and upkeep to prevent such disasters.

Frequently asked questions