A gathering of shells

When inspiration is in short supply you can do worse than bring out the seashells!

"Ocean acidification is often referred to as osteoporosis of the oceans because as acidity rises, shell building creatures such as lobster, oyster, crab, shrimp, and coral are unable to extract the calcium carbonate from the water that they need to build their shells and are thus unable to survive."

 Philippe Cousteau, Jr.