Ocean ecosystems, coral bleaching, and fishing industry.
"Over Earth’s history, ocean life has recovered from numerous sudden extinction episodes by adaptation and evolution of new species, but the time scales for extinction and re-population are millions of years, not a few hundred years. Human-driven ocean acidification is affecting the ocean far faster than the Earth’s natural recovery pace can accommodate. Today’s rate of acidification is 10 times faster than anything experienced since the demise of the dinosaurs 65 million years ago."
As Earth's oceans warm and become more acidic, ocean creatures including pteropods are undergoing severe stress. They are harbingers of change. It's possible by 2050 that they might not be able to make a shell any more and if we lose these organisms the impact on the food chain will be catastrophic.
"Knowledge of the oceans is more than a matter of curiosity. Our very survival may hinge upon it.” President John F. Kennedy, Jr., March 1961 message to Congress.