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Images: Ocean Acidification: A Risky Shell Game

Justin Ries, a former postdoctoral scholar at Woods Hole Oceanographic Institution, grew 18 species of shell-building marine organisms in tanks under air containing different concentrations of carbon dioxide—from the level in today's atmosphere, to higher levels predicted for the future, to extremely high levels. He and colleagues found that not all species responded the same way to higher carbon dioxide levels in seawater and the higher aciditiy it generates. Some species deteriorated, but surprisingly, some thrived. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

Ries and WHOI colleagues Anne Cohen and Dan McCorkle kept conchs (Strombus alatus) in seawater under different levels of atmospheric carbon dioxide (CO2) to see how their shells were affected by the increased ocean acidity caused by elevated CO2. On the left, a conch from seawater under today's CO2 levels (400 parts per million, or ppm) has a normal shell, with normal bumpy protuberances. The conch on the right, reared under very high CO2 conditions (2,850 ppm), has a shell that has begun to deteriorate, its protuberances dissolved away in the more acidic seawater. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

At the microscopic level, blocks of calcium carbonate crystals in conch shells can dissolve away in more acidic conditions caused by high carbon dioxide (CO2). The conch on the right, reared under CO2 levels in today's atmosphere, produced a shell with orderly blocks of crystals, while the conch on the left, grown under 2,850 ppm CO2 conditions, produced irregular, disordered blocks with etched surfaces. (Micrograph by Justin Ries, Woods Hole Oceanographic Institution)

Justin Ries holds two tropical pencil urchins (Eucidaris tribuloides) reared under different levels of atmospheric carbon dioxide (CO2). The urchin on the right, grown in seawater under today's air conditions (400 ppm), is healthy and has normal spines. The urchin on the left, grown under very high CO2 conditions (2,850 ppm), is substantially damaged by the more acidic conditions. Most of its spines have fallen off, and the remaining ones show a pitted texture under the scanning electron microscope. Weighing the urchins confirmed that they were actually dissolving in the more acidic high CO2 conditions.

(Micrograph below by Justin Ries, WHOI, and photo by Tom Kelindinst, WHOI)

Most of the spines of an urchin grown under the highest CO2 conditions fell off, and, under a scanning electron microscope, the remaining ones (left) show a pitted texture. On the right are spines of an urchin grown under current conditions. (Micrograph by Justin Ries, Woods Hole Oceanographic Institution)

Among organisms the scientists grew under varied levels of CO2 were commercially important species such as American lobster (Homarus americanus). In a surprising result, the lobster on the right, grown under a very high level of CO2 (2,850 ppm, or 10 times pre-industrial levels) grew a larger, heavier shell than the lobster on the left, grown under today's CO2 level (400 ppm). (Photo courtesy of Justin Ries, University of North Carolina)

Blue crabs (Callinectes sapidus) grown for two months under today's CO2 levels of 400 ppm (left) and under very high CO2levels of 2,850 (right). This species showed an unexpected response to CO2 level—the crab grown under the highest level (representing ten times the level of CO2 in the pre-industrial atmosphere) grew a heavier, larger shell. (Photos courtesy of Justin Ries, University of North Carolina)