Warming of the Mediterranean Sea hampers the resistance of corals and mollusks to ocean acidification

Aug 29, 2011
Mediterranean gorgonians. Credit: Aldo Ferrucci

Some calcifiers (mussels, gastropods and corals) protect their shell or skeleton from the corrosive effects of increasing ocean acidification. They can therefore resist some of the damaging effects of increasing ocean acidity generated by the release of carbon dioxide (CO2) in the atmosphere through human activities. This resistance is diminished when organisms are exposed to extended period of elevated temperature (28.5°C). This is a result of an international study, co-lead by Jean-Pierre Gattuso, research scientist at Laboratoire d'océanographie de Villefranche, published in the journal Nature Climate Change. These results suggest that the ongoing and future warming of the Mediterranean combined with the rise of its acidity will increase the frequency of mass-mortality events.

The oceans absorb about one fourth of the (CO2) released by the use of fossil fuel and changes in land use. This amounts to 1 million tons CO2 every hour and leads to large changes in the chemistry of seawater, including an increase in its acidity. This acidification threatens calcifying , those that build shells and skeletons, such as mollusks and corals.

In this study, lead by R. Rodolfo-Metalpa, scientists relocated corals, and around the island of Ischia (Gulf of Naples, Italy) where seawater is naturally acidified by CO2 vents linked to the volcanic activity of Vesuvio. The use of a radioactive tracer demonstrated that these organisms are able to produce limestone at the level of acidity expected for 2100 (pH of 7.8 versus 8.1 today), sometimes at even a higher rate. The tissues and organic layers covering the shells and skeletons play a major role to protect them from the corrosive action of high-acidity seawater. However, the areas of shells and skeletons that are not protected by tissues or organic layers are vulnerable and more prone to dissolution. The higher the acidity, the faster dissolution is. The scientists have shown that this capacity to resist is much lower when the organisms are subject to an extended period of elevated temperature (28.5°C). At this temperature, mortality is increasing with increasing acidity.

Some Mediterranean invertebrates already live at their upper limit of temperature tolerance and have already experienced mass-mortality events. The combined effect of warming and increased acidity will likely increase the frequency of these events in the future.

Explore further: Priorities for research on pharmaceutical and personal care products in the environment

More information: R. Rodolfo-Metalpa, et al. 2011. Coral and mollusc resistance to ocean acidification adversely affected by warming. Nature Climate Change.

add to favorites email to friend print save as pdf

Related Stories

Ocean acidification threatens cold-water coral ecosystems

Apr 03, 2006

Corals don't only occur in warm, sun-drenched, tropical seas; some species are found at depths of three miles or more in cold, dark waters throughout the world's oceans. Some cold-water coral reefs are home to more than 1,300 ...

Limiting ocean acidification under global change

Aug 20, 2010

Emissions of carbon dioxide are causing ocean acidification as well as global warming. Scientists have previously used computer simulations to quantify how curbing of carbon dioxide emissions would mitigate climate impacts. ...

Recommended for you

Implications for the fate of green fertilizers

19 hours ago

The use of green fertilizers is a practice that has been around since humans first began growing food, but researchers are warning that modern techniques for the creation of these fertilizers could have implications ...

User comments : 0