01 August 2011

Ocean acidification: A looming threat

Stuart Dickinson
A diagram depicting the air - sea exchange of carbon dioxide. Image courtesy Wikipedia.

Because of the increasing quantities of carbon dioxide (CO₂) being pushed into the Earth’s atmosphere, our oceans are slowly becoming more acidic. This newly discovered phenomenon, termed ocean acidification, has been described by experts as the evil twin of global warming and the most important scientific crisis we face today.

An increase in acidity means that many plant and animal species will struggle to build and maintain their skeletons or shells. A far more sinister effect is that this acidity can tamper with the bodily functions of all ocean creatures, interfering with growth or reproduction. 

Oceanographer and environmental scientist Rob Dunbar explains that currently about one-third of carbon dioxide pumped into the atmosphere from burning fossil fuels is dissolved in the oceans.

“Even if you are a hard-bitten global-warming sceptic, and I talk to that community fairly often, you cannot deny the simple physics of CO₂ dissolving in the ocean,” he says. 

Recent studies have proven that, between 1751 and 1994, the pH level on the ocean surface has dropped by just over 0.1 units on the logarithmic scale of pH, meaning that the “acidity”, or H⁺ ion concentration in seawater, has increased by nearly 30% during that time.

According to Wikipedia, projections indicate that by 2100, acidity levels would have risen by nearly 130%. Prior to the industrial age, the pH level of the ocean stood at 8.179. Present levels stand at 8.069, and the level predicted for 2100 is 7.824.

Although most research is still in its infancy, experts suggest the ramifications will be dire if not addressed in the long term. Across the globe, scientists are being mobilised into special research groups to look at every aspect of ocean acidification, and what impact it may have on ocean ecosystems and organisms.

Researchers test how higher quantities of acid in seawater affects the development of ocean crustaceans. Image courtesy Plymouth Marine Laboratory.

Looking at the problem


At the forefront of the acidification threat are the millions of plant and animal species that build their shells using calcium carbonate – a substance that becomes more soluble in acidic fluid.

The main framework of coral reef systems is calcium carbonate, and Dunbar explains that as acid content increases, reef systems will start to melt away, thus resulting in a devastating loss in marine biodiversity.

According to the Scientific American, different tests have been conducted to determine how ocean life fares in water with higher levels of acidity. In one such experiment, a sample of copepod species (small crustaceans, a common form of zooplankton) was exposed to water 0.2 pH below normal. Half of them died within a week.

“The fish we prefer to eat, from tuna to salmon or striped bass, depend on an abundance of specific copepods to support the prey that supports them,” reads the article.

A sensor collects pCO2 and temperature data every hour and transmits it via satellite to a laboratory, where information is utilised in understanding ocean acidification effects on coral reef ecosystems. Image courtesy Wikipedia.

In another study, the larvae of temperate brittle star (a relative of the common sea star) were exposed to water reduced in pH by 0.2 to 0.4 units. Less than 0.1% of the larvae survived for more than eight days, while many showed abnormal development. 

Some species of fish, like the spotted wolffish, have shown “remarkable resilience” to the acid tests conducted, due to their ability to store extra oxygen in their tissue. H⁺ ions hamper the blood’s ability to absorb oxygen from water. But even if species like the spotted wolffish are more resilient to higher levels of acidity, how will they fare if their food sources dwindle? 
Quoted in an article in National Geographic, former chief biodiversity adviser to the World Bank Thomas Lovejoy estimated that the acidity of the oceans will more than double in the next 40 years.

“This rate is 100 times faster than any changes in ocean acidity in the last 20-million years, making it unlikely that marine life can somehow adapt to the changes.”

What can we do?

Despite criticism around the issue and the infancy of scientific research, one thing is clear – ocean acidification is happening, and it’s something we cannot afford to ignore. A difficult task is finding a common understanding between every person affected, from scientists and policy makers to the general public.

A video produced by the Plymouth Marine Laboratory (view below) explains that the ocean acidification community has taken steps in doing this by forming the Reference User Group, where various stakeholders across all spheres gather to share new scientific information and explore ways to disseminate this information as quickly as possible.

Chairperson of the International Acidification Reference User Group Dan Laffoley explains: “Policy is effectively how you get things done. Research is there to inform, but unless politicians are well informed and have the right policies, they are not going to take the right actions.”

Robert Watson, Chief Scientific Adviser in the Department for Environment, Food and Rural Affairs in the United Kingdom. Image courtesy Plymouth Marine Laboratory.

Robert Watson, Chief Scientific Adviser in the Department for Environment, Food and Rural Affairs in the United Kingdom, says headway is being made in the dialogue, but these are very difficult issues to address.

“Carbon dioxide is related to energy, energy is related economic growth. Therefore as we argue that we need to reduce the effect of climate change and/or ocean acidification, we will have to change the way we produce and use energy, and the way we manage our land as well.” 

If you want to start making a difference, however small it may seem, why not start by reducing your CO₂ emission footprint today?

Check out websites like Brave New Climate to find out the best ways of doing so, which include using “green electricity”, using energy- and water-efficient appliances, avoiding using your car wherever possible, recycling, re-use and avoiding “useless purchases”, as well as making your home more energy efficient. 

As one internet user commented on YouTube after watching a video about ocean acidification: “Our descendants will stand forever aghast, condemning this generation for the horrific and wanton destruction of the biosphere” unless we take stock of our actions and their effect on the earth.

Further reading

• Acid test: Can we save our oceans from CO₂?

A world without corals?

Plankton in trouble?


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