Rising CO2 emissions in the atmosphere due to the burning of fossil fuels is causing ocean acidification. Ocean dwelling organisms, many of which we eat and depend on, will be negatively affected because forming carbonate (i.e. shells) will become much more difficult. A new study from the north Pacific provides evidence that the oceans are becoming more acidic on a large scale.

Graph showing the increase in both atmospheric and dissoved ocean CO2, and decrease of ocean pH (increase in acidity). Source: Doney et al.

The results of a 15-year long study in the north Pacific Ocean provides evidence that the planet’s oceans are becoming more acidic due to increasing CO2 emissions in the atmosphere. The study, just published in Geophysical Research Letters, compared the pH of seawater samples taken along a transect between Oahu, Hawaii and Kodiak, Alaska on two expeditions in 1991 and 2006. The results show that average pH has decreased by 0.023 in the top 800 m of the ocean. While that may not sound like a lot, this decrease in pH corresponds to a roughly 6% increase in ocean acidity.

An increase in the concentration of CO2 in the atmosphere increases the partial pressure of CO2, causing an imbalance between the dissolved CO2 in the oceans and the atmosphere. The oceans consequently absorb CO2, which creates carbonic acid in the water. In other words, by burning lots of stuff (coal, gas, wood) here on land, we are changing the chemistry of the earth’s oceans.

What does this mean? Since the beginning of the industrial revolution, the oceans have become 30% more acidic. This increase in acidity is happening at a rate 100 times faster than what marine organisms have experienced in the last 20 million years. 65 million years ago, ocean acidification was linked to mass extinctions of marine organisms that use calcium carbonate. Also at that time, coral reefs disappeared and were not seen again in the geological record for millions of years.

Marine organisms such as this reef-dwelling Napoleon Wrasse could be affected by rising ocean acidity

Any marine organism that builds a shell or skeleton is being impacted by rising acidity. Higher concentrations of carbonic acid make it more difficult for these organisms to form calcium carbonate. Many of these creatures make up the basis for marine food webs, meaning that if they start to die off because they can’t build shells, fish and other species higher up the food chain could be without a food source. The multi-billion dollar commercial fishing industry, not to mention artisanal fisheries that millions of people rely on for protein, could fall apart.

Oysters in the half shell – get em while you can!

Sources:

Ocean Acidification: A Critical Emerging Problem for the Ocean Sciences By S.C. Doney, W.M. Balch, V.J. Fabry, and R.A. Feely

Direct observations of basin-wide acidification of the North Pacific Ocean By R.H. Byrne, S. Mecking, R.A. Feely, and X. Liu.

Pacific’s rising acid levels threatening marine life By S. Doughton, Seattle Times