A study published in The Journal of Experimental Biology examines how warmer temperatures and ocean acidification affect the biology of porcelain crabs.

Porcelain crabs live on the rocky shorelines that border the Indian and Pacific oceans. The crabs are used to varying climatic conditions – coastlines’ intertidal zones can shift in temperature by 20°C over six hours, and ocean acidity is affected by seasons and time of day. However, this variation is naturally gradual and gives the animals time to adjust. To test how the crabs react to higher air temperatures and greater acidity, scientists put them in controlled environmental conditions and studied them over a two and a half week period.

Porcelain crab on carpet anemone (Image: Nick Hobgo)

Porcelain crab on carpet anemone (Image: Nick Hobgo)

At the end of the testing phase, crabs that were exposed to higher temperatures and higher acidity had a 25 percent lower metabolic rate than ones in lower acidity/lower temperature conditions. While the porcelain crabs were able to cope with the extreme condition, they were forced to redistribute their energy to make themselves more thermally tolerant. This, in turn, left them without enough energy to grow or reproduce.

“Intertidal zone organisms may be able to withstand increased warming and acidification,” the report concludes, “but with performance effects that could lead to reduced ecological resilience.”

As a food source for fish, birds and other crabs, the reduction in porcelain crab numbers would have an impact on the rest of the intertidal food chain.

Previous studies have also examined how climate change impacts marine ecosystems. A January 2012 report in the journal Marine Science found that “population-level shifts are occurring because of physiological intolerance to new environments, altered dispersal patterns, and changes in species interactions.”

Species distributions, it concluded, were strongly linked to climate, and the “aggregated effects [of climate change] may modify energy and material flows as well as biogeochemical cycles, eventually impacting the overall ecosystem functioning and services upon which people and societies depend.”

The 2014 Greenhouse Gas Bulletin released by the World Meteorological Association asserts that oceans are currently acidifying at their fastest rate in 300 million years. This is caused by an increased absorption of atmospheric carbon dioxide, which turns seawater into carbonic acid. Combined with ocean warming, ocean acidification has been linked to an increase in coral bleaching and fish die-offs.

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