“You’re going to have an ocean acidification effect on top of the respiration effect and that is likely to increase the rates of nighttime dissolution,” Kwiatkowski said. As a result, tide pools will start each night more acidic than they already are, leading to deeper dissolution of shells and skeletons in the nocturnal hours. And as humans pump more and more CO 2 and other greenhouse gases into the atmosphere, the ocean’s pH is expected to drop even more. In the past century, greenhouse gas emissions have already increased the acidity of the ocean by 30%. Real Effects of Ocean AcidificationĪs humans pump more and more carbon dioxide and other greenhouse gases into the atmosphere, the ocean’s pH is expected to drop even more.īeyond identifying a handy natural laboratory for studying ocean acidification and its effects, the new findings also forebode worsening nighttime stress to come for tide pool inhabitants. Many of the photosynthesizing organisms also calcify, Kwiatkowski noted, so he speculates that perhaps the extra energy provided by photosynthesis makes them less sensitive to the availability of aragonite and therefore more resilient against any daytime dissolution. On the flip side, at night, when acidity rose again, these organisms were much more sensitive to the availability of aragonite, and their shells and skeletons began to dissolve. The researchers found that during the day when water pH was less acidic, the calcifying organisms grew more, even when the availability of aragonite was relatively low. When this number is low, calcium carbonate already incorporated into sea creatures’ bodies dissolves back into the water. A high saturation state value means there is enough aragonite available for the organisms to use. The team specifically looked at how the aragonite saturation state-a number that tells scientists how much aragonite (a form of calcium carbonate) is available for creatures to use-affected tide pool creatures at different times of the day. The tide pools studied by Kwiatkowski and his colleagues host skeleton builders such as coralline algae and shell builders such as mussels and limpets as well as noncalicifying organisms such as sea grass and red, brown, and green algae.įrom the chemistry of the water, the researchers gleaned information about the growth and dissolution of the calcium-rich frameworks of the inhabitants. A more acidic ocean can interfere with this shell- or skeleton-building process. Corals, for instance, use calcium carbonate to make skeletons, whereas other creatures, including snails, clams, and mussels, create shells. To create crystals of calcium carbonate, many sea creatures collect calcium ions and carbonate ions from seawater.
When the ocean absorbs CO 2, the molecule reacts with water to form carbonic acid, which builds up and threatens marine organisms that have shells or skeletons made from the compound calcium carbonate. The oceans are acidifying worldwide from people pumping vast quantities of CO 2 into the air. “As the communities respire, they produce CO 2, which lowers the pH in a very similar way to what we would expect to happen on decadal and centennial time scales due to climate change,” said Kwiatkowski, the lead author on the new paper. But the researchers realized that this microcosm of life offered a highly accelerated analogue of the global phenomenon of ocean acidification. The kinds of “breathing” taking place and their effects on water chemistry weren’t entirely new information. The researchers realized that this microcosm of life offered a highly accelerated analogue of the global phenomenon of ocean acidification.
After sunset, that process stops, and other organisms continue to respire by taking up oxygen and releasing CO 2-similar to the way humans breathe-dropping the pH and acidifying the water, Kwiatkowski said. In a paper published earlier this month in Scientific Reports, the researchers describe the pattern as an influence of two different types of “breathing” that alternately dominate tide pool chemistry: When the Sun shines during the day, photosynthesizing organisms such as algae take up carbon dioxide (CO 2) and release oxygen, which raises the pH of the tide pool.
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