Since the beginning of the Industrial Revolution, ocean surface waters have become about 30% more acidic. Ocean acidification occurs when seawater absorbs carbon dioxide (CO2), a greenhouse gas emitted in large quantities by human activities. As the amount of CO2 in the atmosphere continues to increase, the oceans are becoming more acidic. Such an imbalance causes a terrifying list of changes to oceanic environments, including the bleaching (death) of coral reefs, and the disruption of skeleton and shell development for many ocean creatures. Higher levels of CO2 can also mean an increase in algae and other photosynthetic organisms such as sea grass that, when growing in excess, can create “dead zones” by sucking up all the oxygen that other aquatic organisms need in order to survive. If algae grows unchecked on the surface, the water can appear green (or, in some cases, red), replacing that gorgeous ocean blue with something much more murky and, sometimes, toxic. Learn more about ocean acidification here (there’s a great video at the bottom of the page): https://www.nrdc.org/issues/reduce-ocean-acidification and start reading up on the issue here: http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F.