Introduction To Ocean Acidification

Question 1

What are the human impacts on ocean biogeochemistry since the industrial revolution?

Answer 1

1. Development of new energy systems
2. Development of chemistry industry
3. Changes in agriculture and land use

Question 2

What is ocean acidification?

Answer 2

Decrease in pH due to increased CO2

Question 3

What should average ocean pH be?

Answer 3

8-8.1

Question 4

What are anthropogenic (predominant cause) sources of atmospheric CO2?

Answer 4

• Burning of fossil fuels
• Deforestation
• Changes in land-use
• Energy & cement production

Question 5

Atmospheric CO2 concentration post industrial revolution?

Answer 5

over 410ppmv

Question 6

What is worrying about the rising CO2 concentrations?

Answer 6

The rate/speed at which they are rising e.g. increases that used to take 100,000 years, now only take 225 years.

Question 7

How much anthropogenic CO2 was released during the industrial revolution?

Answer 7

450 billion metric tons

Question 8

What did the CO2 monitoring station in Hawaii find?

Answer 8

CO2 increased from 360ppm in 1990 to 410-420 present

Question 9

What are direct effects of humans on ocean biogeochemistry? (and examples)

Answer 9

Fluxes of material into the oceans e.g. nutrient runoff, increased CO2 from industry

Question 10

What are indirect effects of humans on ocean biogeochemistry?

Answer 10

Climate change and altered ocean circulation

Question 11

Atmospheric CO2 concentration for the past 800,000 years (pre-industrial revolution)?

Answer 11

172-290ppmv

Question 12

Atmospheric CO2 concentration post industrial revolution?

Answer 12

over 410ppmv

Question 13

What is worrying about the rising CO2 concentartions

Answer 13

The rate/speed at which it is rising

Question 14

What is the process of ocean acidification?

Answer 14

• CO2 goes from the atmosphere and mixes with the surface water of the ocean
• Then combines with water to form carbonic acid – weak acid that rapidly disassociates to form hydrogen and carbonate ions
• Because surface waters are saturated with carbonate ions they react with the free hydrogen ion to produce more bicarbonate – natural buffering capabilities in oceans – how they stay stable

Question 15

What are the global patterns of ocean acidification?

Answer 15

• Changes in pH are not uniform

- Greater changes around the tropics

Question 16

What are the problems with ocean acidification?

Answer 16

1. The disassociation produces lots of protons which lowers pH – increased acidity
2. Calcium carbonate ions get used by organisms e.g. to produce shells
   - As more CO2 the natural buffer is failing – not enough carbonate ions for other organisms – reduced carbonate concentrations

Question 17

What is the natural buffering pH?

Answer 17

~8-8.1

Question 18

What does CO2 solubility depend on?

Answer 18

Temperature, salinity & pressure

Question 19

When is CO2 less soluble?

Answer 19

At warmer temperatures e.g. absorbed less in tropical regions = more saturated in carbonate molecules

Question 20

When are CaCO3 saturation states higher?

Answer 20

In shallow, warm tropical waters

Question 21

When are CaCO3 saturation states lower?

Answer 21

In cold, high-latitude regions and at depth

Question 22

When are the effects of enhanced CO2 going to be more pronounced?

Answer 22

In colder, deeper regions

Question 23

Why do warm, tropical regions tend to have higher carbonate concentrations?

Answer 23

CO2 is less soluble at warmer temperatures, so less CO2 is absorbed
- Also means greater saturation of carbonate minerals

Question 24

Where are the effects of enhanced CO2 more pronounced?

Answer 24

In colder, deeper regions

Question 25

When does calcification occur?

Answer 25

When precipitation of CaCO3 is facilitated by high pH and high carbonate concentration

Question 26

How is calcification achieved in calcifying organisms?

Answer 26

Through energy-consuming ion transport processes

Question 27

How much of C02 emissions since the industrial revolution have been released in the last 30 years (as a %)?

Answer 27

50%

Question 28

How much has ocean pH decreased since the industrial revolution? How much has ocean acidity increased?

Answer 28

0.1pH unit, a 30% increase in acidity

Question 29

What is the fundamental building block of many marine organisms?

Answer 29

Calcium carbonate

Question 30

What is dissolving of calcium carbonate determined by?

Answer 30

Saturation state

Question 31

How does calcium carbonate concentration affect ocean acidification?

Answer 31

Atmospheric CO2 can only be absorbed if enough calcium carbonate dissolves in the water column or sediments

Question 32

What is the equation for saturation state?

Answer 32

Ω = [Ca2+] [CO32- ]/K’sp

Question 33

What does it mean if saturation state is over 1?

Answer 33

Supersaturation- conditions are favourable for shell formation

Question 34

What does it mean if saturation state is below 1?

Answer 34

Under-saturation- Dissolution of calcium carbonate etc.

Question 35

What are the two main forms of calcium carbonate? Which is more soluble?

Answer 35

Calcite and Aragonite. Aragonite is more soluble.

Question 36

Creatures with shells made of aragonite or calcite are more likely to be affected by ocean acidification? Why?

Answer 36

Aragonite as it is much more soluble.

Question 37

In colder polar regions what is the saturation state like?

Answer 37

Lower

Question 38

What part of the ocean is undersaturated in terms of calcium carbonate, due to pressure?

Answer 38

Deeper ocean waters