Introduction To Ocean Acidification Flashcards
What are the human impacts on ocean biogeochemistry since the industrial revolution?
- Development of new energy systems
- Development of chemistry industry
- Changes in agriculture and land use
What is ocean acidification?
Decrease in pH due to increased CO2
What should average ocean pH be?
8-8.1
What are anthropogenic (predominant cause) sources of atmospheric CO2?
- Burning of fossil fuels
- Deforestation
- Changes in land-use
- Energy & cement production
Atmospheric CO2 concentration post industrial revolution?
over 410ppmv
What is worrying about the rising CO2 concentrations?
The rate/speed at which they are rising e.g. increases that used to take 100,000 years, now only take 225 years.
How much anthropogenic CO2 was released during the industrial revolution?
450 billion metric tons
What did the CO2 monitoring station in Hawaii find?
CO2 increased from 360ppm in 1990 to 410-420 present
What are direct effects of humans on ocean biogeochemistry? (and examples)
Fluxes of material into the oceans e.g. nutrient runoff, increased CO2 from industry
What are indirect effects of humans on ocean biogeochemistry?
Climate change and altered ocean circulation
Atmospheric CO2 concentration for the past 800,000 years (pre-industrial revolution)?
172-290ppmv
Atmospheric CO2 concentration post industrial revolution?
over 410ppmv
What is worrying about the rising CO2 concentartions
The rate/speed at which it is rising
What is the process of ocean acidification?
- 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
What are the global patterns of ocean acidification?
- Changes in pH are not uniform
- Greater changes around the tropics
What are the problems with ocean acidification?
- The disassociation produces lots of protons which lowers pH – increased acidity
- 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
What is the natural buffering pH?
~8-8.1
What does CO2 solubility depend on?
Temperature, salinity & pressure
When is CO2 less soluble?
At warmer temperatures e.g. absorbed less in tropical regions = more saturated in carbonate molecules
When are CaCO3 saturation states higher?
In shallow, warm tropical waters
When are CaCO3 saturation states lower?
In cold, high-latitude regions and at depth
When are the effects of enhanced CO2 going to be more pronounced?
In colder, deeper regions
Why do warm, tropical regions tend to have higher carbonate concentrations?
CO2 is less soluble at warmer temperatures, so less CO2 is absorbed
- Also means greater saturation of carbonate minerals
Where are the effects of enhanced CO2 more pronounced?
In colder, deeper regions
When does calcification occur?
When precipitation of CaCO3 is facilitated by high pH and high carbonate concentration
How is calcification achieved in calcifying organisms?
Through energy-consuming ion transport processes
How much of C02 emissions since the industrial revolution have been released in the last 30 years (as a %)?
50%
How much has ocean pH decreased since the industrial revolution? How much has ocean acidity increased?
0.1pH unit, a 30% increase in acidity
What is the fundamental building block of many marine organisms?
Calcium carbonate
What is dissolving of calcium carbonate determined by?
Saturation state
How does calcium carbonate concentration affect ocean acidification?
Atmospheric CO2 can only be absorbed if enough calcium carbonate dissolves in the water column or sediments
What is the equation for saturation state?
Ω = [Ca2+] [CO32- ]/K’sp
What does it mean if saturation state is over 1?
Supersaturation- conditions are favourable for shell formation
What does it mean if saturation state is below 1?
Under-saturation- Dissolution of calcium carbonate etc.
What are the two main forms of calcium carbonate? Which is more soluble?
Calcite and Aragonite. Aragonite is more soluble.
Creatures with shells made of aragonite or calcite are more likely to be affected by ocean acidification? Why?
Aragonite as it is much more soluble.
In colder polar regions what is the saturation state like?
Lower
What part of the ocean is undersaturated in terms of calcium carbonate, due to pressure?
Deeper ocean waters
