Winners(?) and losers

The Great Beyond: Climate change creates shell-size surprise

Nature reports that a new lab study of several types of sea creatures confirms that some actually grow bigger and better shells in lower pH sea water:

Ries and colleagues from Woods Hole Oceanographic Institution grew 18 different species in tanks with differing levels of carbon dioxide. They found seven species had more shell under higher carbon dioxide: crabs, lobsters, shrimp, red and green calcifying algae, limpets and temperate urchins (image top – larger animal grew under higher carbon dioxide).

Another 10 species did worse: oysters, scallops, temperate corals, tube worms, hard and soft clams, conchs, periwinkles, whelks and tropical urchins (image lower – smaller animal grew under higher carbon dioxide). Only one species was unaffected, the humble mussel, they report in Geology.

That Nature link at the top will probably stop working soon, but the press release it is based on is here. The researchers note that this study is pretty preliminary, as the didn't account for nutrient levels. Moreover, the ecological effect of one species building a bigger, stronger shell is not at all clear:

“I wouldn’t make any predictions based on these results. What these results indicate to us is that the organism response to elevated CO2 levels is complex and we now need to go back and study each organism in detail.”

Ries concurs that any possible ramifications are complex. For example, the crab exhibited improved shell-building capacity, and its prey, the clams, showed reduced calcification. “This may initially suggest that crabs could benefit from this shift in predator-pray dynamics. But without shells, clams may not be able to sustain their populations, and this could ultimately impact crabs in a negative way, as well,” Ries said.

In addition, Cohen adds, even though some organisms such as crabs and lobsters appear to benefit under elevated CO2 conditions, the energy they expend in shell building under these conditions “might divert from other important processes such as reproduction or tissue building.”