The oceans of the world have probably become increasingly acidic in the last 1
Ocean acidification occurs when CO2 from the atmosphere is absorbed by seawater with more acidic water lower pH. About one third of the CO2 released by the combustion of coal, oil and gas is dissolved in the oceans. Since the beginning of the Industrial Age, the ocean has absorbed about 525 billion tonnes of CO2, or about 22 million tonnes per day.
Over the past 22 million years, researchers have reconstructed the acidity of the oceans and the atmospheric CO2 chemistry of the fossil shells of tiny marine creatures that once lived near the surface of the ocean. They were able to submit their new records of pH and CO2 levels in the context of the range of future CO2 emission scenarios recognized by the Intergovernmental Panel on Climate Change (IPCC).
The current pH is probably already lower than ever In the last two million years, and in a "business-as-usual" scenario, where CO2 is emitted at the same rate as today, atmospheric CO2 would be absorbed into the atmosphere By the year 2100, the average pH of the ocean will be less than 7.8 by 2100, compared to about 400 parts per day today, compared to a current pH of about 8.1. This is significant because the pH scale is logarithmic, meaning that a drop of 0.1 pH units represents a 25% increase in acidity.
These values of atmospheric CO2 and ocean acidity have not been known since the mid-Miocene Climate Optimum when global temperatures were about 3 ° C warmer than they are today due to the Earth's natural geological cycle.
Scientists are increasingly finding evidence of negative effects. For example, fish lose their sense of smell due to increasingly acidic oceans, new research from the University of Exeter in the UK shows. Fish use their sense of smell to find food, secure habitats, avoid predators, recognize each other and find suitable spawning grounds. A reduction in their ability to smell may therefore jeopardize these essential functions for their survival. The study provides evidence that economically important species, such as sea bass, are affected by elevated levels of CO2 and make fish susceptible because they impair their ability to detect odors.
A study by the Australian Marine and Antarctic Research Institute has highlighted the challenges that scientists, governments and communities face in the face of ocean acidification. These researchers have found that surface ocean pH has fallen 10 times faster in the past few centuries than in the last 300 million years. The economic costs of coral reefs, wild fishing and aquaculture are expected to be more than $ 300 billion a year.
In some parts of the world, such as Chile and the US West Coast, some fisheries are already adapting ocean acidification to partnerships between scientists, industry and government. Other global impacts probably require similar cooperation and action at the international level, say the researchers. An important question for scientists and policymakers is whether people should try to mitigate the acidification of the oceans by changing the chemistry of the oceans or by simply adapting communities.