PH is the measure of a liquids acidity or alkalinity. The lower the pH, the higher its acidity and the higher the number, the more alkaline it is. The pH of the planet’s oceans was stable at between 1000 and 1800 but has dropped since the Industrial Revolution by one-tenth of a unit. By 2100, the ocean’s pH level is expected to drop by another 0.3 units. When carbon dioxide is absorbed by seawater, it forms carbonic acid, which lowers the ocean’s pH. This makes it harder for corals, plankton and tiny marine snails (pteropds) to make their shells and skeletons.

It is easy for scientists to prove ocean acidification using basic chemistry. Global-warming predictions are based on computer models but ocean acidification can be proved in an aquarium. Experiments show that adding carbon dioxide to sea water slows corals’ growth rates and dissolves pteropods’ shells. When corals in aquariums are exposed to the level of carbon dioxide expected by 2050, they grew half as fast as they do now. If you add to acidification the rise in sea temperatures caused by climate change, it is unlikely that corals will survive to the end of the century.

Acid levels in the world’s oceans are increasing due to the increasing amounts of carbon dioxide produced by the burning of fossil fuels by industry and car exhaust fumes. It was originally predicted that acidification would take place over centuries but it is now apparent that it is taking place over decades.

Ecological Impact

Corals and plankton with chalky shells make up about a third of all marine life and are the basis of the marine food change. The loss of these would mean widespread ecological problems. When Carbon Dioxide levels in the atmosphere reach about 500 parts per million these organisms will no longer be able to use calcium to make their skeletons. At the moment Carbon Dioxide levels are 385 ppm, having risen from 305 ppm in 1960.

Red calcareous algae, which hold the edges of coral reefs together in swift currents, are starting to dissolve. Without these algae, coral reefs may begin to erode.

A quarter of all known marine fish live in coral reefs and coastlines are protected from storms and wave action by coral reefs. Coral reefs also provide economic benefits to the countries that have them by providing fishing grounds and are important to their tourist industry.

Reef building coral is made up of colonies of thousands of tiny polyps. It is the growth of these polyps that creates a reef. Inside each polyp is a microscopic algae, called zooxanthellae, which help it to feed by using the energy of the sun to make sugars. It is these algae which provide the colour of the reef. The relationship between the polyp and zooxanthellae is reliant on not just sunlight but also to water temperature and chemistry. The polyp will eject the algae if conditions are not right causing it to turn white. This is known as coral bleaching. Without the algae, the coral cannot get the food it needs to grow.

Pollutions from agriculture, shipping, sediment caused by deforestation, construction and destructive fishing practices have damaged 60% of the World’s coral reefs. Add climate change to these problems and this could severely weaken the coral’s natural ability to recover from damage. The sea temperature is expected to increase over the next few years and this could create the conditions which cause mass bleaching events. The El Nino event in 1998 caused the loss of 16% of the planet’s coral reefs in one year. This reef has been unable to recover due to other ecosystem changes and stresses that have slowed the growth of the coral.

Pollution, warming seas, human damage and ocean acidification means our beautiful, delicate coral reefs have a bleak outlook for the future. Unless something is done to reduce these environmental changes it is unlikely that their will be any living coral reefs by the end of the century, just dead, white islands of coral being eroded by the movement of the sea. This loss would be a tragedy for future generations.