Opinion: Ocean acidification is an indisputable problem

Oceans are like giant vacuum cleaners. They absorb carbon dioxide emitted from burning fossil fuels and help clean the air. This has a beneficial effect on the Earth’s atmosphere and climate.

But the effects on the oceans and on the species that inhabit them are far less positive because, in the process, oceans are becoming more acidic. As a result, many of the micro-organisms at the bottom of the marine food chain are endangered and may become extinct, with far-reaching consequences for all.

Moreover, because the speed at which the ocean absorbs CO2 varies with the depth of water, it is difficult to envisage what the long-term effects of our current output will be on the oceans. (The creation of a balance between the percentage of CO2 in the air and in the top 1,000 metres of water in the ocean occurs within the space of a year. But, below this level, the same process will take 1,000 years, as the gas-containing water slowly sinks).

This process has recently come to be recognized as the “other problem” created by human-related carbon dioxide emissions. Swedish chemist Svate Arrhenius first predicted more than 100 years ago that ocean acidification would occur, and since that time, ocean acidification has increased by about 30 per cent.

It is hardly surprising. The levels of carbon dioxide in the atmosphere have drastically increased from pre-industrial levels of 280 parts per million to our current level of 403 ppm. The present concentration is the highest we have had during the last 650,000 years and possibly the last 20 million years.

According to the Intergovernmental Panel on Climate Change, if the current rate of carbon dioxide emissions is maintained, the levels of atmospheric carbon dioxide may reach 800 ppm by 2100, which would cause an increase of 150 per cent in ocean acidity compared with the pre-industrial level.

The effects of this increasing acidification are already being seen. The growth of coral around the world is already slowing down, which is important because it is a major marine ecosystem that acts as hatchery and host for fish of all kinds. There are also changes being seen in the size of populations of such mollusks as clams, oysters and scallops, both farmed and in the wild.

Ocean acidification can also affect the reproductive health and survival rates of fish larvae and their juveniles. Ultimately, it will result in the modification or eventual collapse of this food chain as we know it. This means that the larger fish species and marine mammals on which many around the world depend for food and recreation (think of whale watching) may also become extinct.

The oceans have already absorbed approximately 25 per cent of the anthropogenic carbon emissions since the beginning of the industrial era. Eventually, they will remove 90 per cent of the CO2 in the atmosphere, but it will take hundreds of thousands of years for the oceans to absorb the existing CO2 in the air and achieve an equilibrium with it.

But though things appears desperate, a number of solutions are possible. Apart from drastically cutting back on carbon emissions to the atmosphere, new carbon capture and sequestration technologies could be applied to reduce the carbon dioxide concentration in the atmosphere and its transfer to the oceans.

Indeed, if we are able to limit or even decrease the levels of carbon dioxide in the air, we may be able to reduce and possibly reverse the process of ocean acidification in the short-term. But because the oceans take about 1,000 years to catch up with what is going on in the atmosphere (provided the carbon dioxide content of the atmosphere no longer increases), we need to deal with this right now.

Alfonso Mucci, Montreal Gazette, 21 June 2015. Article.

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