What we humans are doing to the oceans is one of the more emotionally challenging topics for me to look at. It’s painful.
And not just because I care about the potential human impacts. I care about all the creatures of the sea and believe, deep down, that having healthy living oceans is very important to the biosphere on numerous levels.
For starters, healthy seas are abundant seas. That means sufficient food for humans and other forms of life. But more importantly, there’s something magic about an ocean teaming with fish, alive with corals, and booming with whale mating songs.
As with everything on land, the ocean’s abundance begins at the bottom of the food chain. Tiny microscopic organisms known as phytoplankton and zooplankton.
And it's this foundation of the ocean food pyramid that's in jeopardy today.
The oceans are facing numerous difficulties including pollution (especially from farm run off), over-fishing, and dragnet methods that ruin innumerable other things besides the targeted catch — but all of that pales in comparison to the problem of ocean acidification.
The process is easy enough to understand. Carbon dioxide in the atmosphere can dissolve into ocean water. The more CO2 in the air, the more that ends up dissolved in the seas. As CO2 in the ocean water rises so too does the formation of carbonic acid — linearly and proportionally — and that acidifies the ocean.
CO2 –> carbonic acid –> Ocean acidification.
The problem with acidifying oceans is that the small creatures on the bottom of the food chain, as well as corals and the more familiar oysters and clams, typically build a house of calcium carbonate to shelter them. As the ocean acidifies, they cannot build their homes. They have a harder time generating energy via metabolic processes, and they become stressed and die off in greater than normal numbers.
(Source)
A recent study concluded that the last time the oceans acidified this quickly, nearly all of the oceanic life forms that we can track via the fossil records went extinct:
The Last Time Oceans Got This Acidic This Fast, 96% of Marine Life Went Extinct
April 9, 2015
The biggest extinction event in planetary history
by lesphelps 
