Ocean Acidification

• The Earth exists in Harmony between plants and animals.
• Plants breath’ in CO2 and ‘exhale’ O2
• Animals breathe in O2 and exhale CO2

• When the Earth first formed the atmosphere was 25-50% carbon dioxide (CO2)
• Plants emerged and converted the planet to an atmosphere of O2
• All the CO2 created snowball Earth

• Animals emerged and reconverted the atmosphere back to mainly CO2
• Earth cycled between ‘tropical Earth’ and ‘ice ages’ till we reached a happy balance called the Holocene 11,000 years ago (we are in this now)
• Humans have now started to alter the harmony between plants and animals

• Carbon Dioxide is the most important greenhouse gas, but there are others
• Just like we saw in Earth’s cycles, more CO2 means higher temperatures
• CO2 dissolves in the ocean like the fizz in a can of soda
• CO2 reacts with water molecules producing carbonic acid
• CO2 reacts with water molecules producing carbonic acid
• The more acid in something the more acidic
• Therefore more CO2 ends up making the ocean more acidic
• Higher acidity = lowering the pH (the oceans pH specifically)
• Since the Industrial Revolution, the pH of the ocean’s surface has dropped from 8.21 to 8.10

What the heck is pH?

• pH of saltwater should be about 8.2 and freshwater is typically 6.5
• pH of water is 7
• When the pH is too acidic or too basic it interferes with the necessary chemical reactions
• There is a lot more to it, but we don’t need to get into that

• pH is a scale of how acidic or basic something is
• 0 is a super strong acid, 7 is neutral, and 14 is the strongest base
• Acid has lots of H+ (hydrogen ion)
• Base or alkaline has lots of -OH (hydroxide ion) or they want a H+

• CO2 is normally in the atmosphere/air
• CO2 dissolves in the ocean like the fizz in a can of soda
• When CO2 is absorbed by seawater, a series of chemical reactions occur resulting in the increased concentration of hydrogen ions (H+)
• Remember the hydrogen ions (H+) = more acidic

What Does Carbon Dioxide Have to Do With Acidification?

• CO2 reacts with water molecules producing carbonic acid (H2CO3) a weak acid that breaks down (chemically called dissociates) into hydrogen ions (H+) and bicarbonate ions (HCO3–) and therefore lowering the oceans pH (raising its acidity)
• Think about if I threw stickers on the tables. Some would take the stickers, some would not, some would put the stickers on and then put them back….same is true of CO2

• Since the Industrial Revolution, the pH of the ocean’s surface has dropped from 8.21 to 8.10
• This is 30% increase in acidity (pH scale is not logarithmic)

Effects on Zooplankton

• Zooplankton as a major link in the marine food chain
• There are two major zooplankton that build shells of CaCO3
• Their shells (and layers of dead shells) fall to the ocean floor and neutralize a lot of excess acid in the ocean
• The pteropod or ‘sea butterfly’ is a tiny sea snail about the size of  small pea. 
• They are critical in the marine food web being eaten by everything from krill to whales.
• They have already been in severe levels in the Southern Ocean

Effects of Coral Reefs

Impact of Fish

• The extra carbonic acid in the water is absorbed into the fishes blood resulting in acidosis
• Acidosis (in humans) result in rapid, shallow breathing, confusion, fatigue, headaches, sleepiness, lack of appetite, jaundice, and increased heart rate. 
• Fish have been seen not avoiding noisy predators, decreased swimming speed, confusion finding their home, and grow larger otoliths (responsible for balance), and decrease in smell