Sea snails, like this red turban snail in Monterey Bay National Marine Sanctuary, develop their shells in layers. For many species, these layers are predominantly composed of calcium carbonate, which provides the shelled critters a tough, protective coating. However, the changes in our climate have caused a dramatic shift in ocean chemistry. When we burn fossil fuels like oil and gas, we release carbon dioxide into the atmosphere, some of which is absorbed by the ocean. With more and more carbon dioxide from the atmosphere dissolving into our oceans, the ocean is becoming less basic. This ocean acidification can cause calcium carbonate shells to dissolve, threatening a number of shelled marine organisms like the red turban snail. We're working to understand the effects of ocean acidification in sanctuaries so we can better protect these animals and the ecosystems that depend on them.