L11 Carbon Cycle Flashcards
What is sequestration
Release of carbon dioxide from stores
Where is the most global carbon
What is the issue with this
In the crust below the land and ocean
It is locked up and cannot be used
Atmospheric reservoir is low but more useful as…
Cycling is very quick
How is atmospheric carbon dioxide determined
Balance between fixation and release by biogenic action
How much carbon does burning of fossil fuels add anually
6 * 10^15
How much carbon is fixed by autotrophy each year
10^17 gC
How much carbon is taken up by oceans
47%
How much of the extra carbon produced currently remians in the atmosphere
A tenth
What risk is assocated with oceans absorbing more carbon
Acidification
What does it mean for the ocean to be saturated
It can’t take up / absorb any more carbon
What has been the change in pH since the industrial revolution (both pH and *)
Preindustrial pH 8.2, currently pH 8.0
PH scale is logarithmic so this is 30* increase in acidity
How does carbon dioxide effect pH
Carbon dioxide mixes with water = carbonic acid
Dissociates to bicarbonate and hydrogen
Dissociates further to carbonate and 2H+
What organisms will be effected by changes in calcium carbonate concentrations
Coral reef, bivalves, coccoliths
What types of calcium carbonate are more vulnerable to increasing acidity
Amophorous and high magnesium
How much carbon is stored in vegetation
60%
The amount captured in terrestrial reservoirs (trees) can be impacted by:
Tree type
Environmental conditions (warmer = more turnover)
Limiting nutrients
How much carbon dioxide specifically from fossil fuels is sequested by terrestrial plants
10-20%
How much carbon is sequestered in plant roots and mycorrhizal fungi
70%
If hetertrophs stopped existing, how long could photoautotrophs survive
300 years then run out of carbon
What are the 3 main processes in biogenic carbon cycling
Reduction of carbon
Aerobic oxidation of carbon
Anaerobic respiration and fermentation
Give examples of photoautotrophs
Cyanobacteria
Algae
Diatoms
Describe where an oxic habitat would form in terms of photoautotrophy and heterotrophy
Where action of photoautotrophy exceeds that of heterotrophy e.g. Marine photic zone
What environments can C cycling occur with no oxygen present
Sub-surface rock
Aquatic sils and sediments
Waterlogged soil
Animal guts
Microenvironments
Is anaerobic biomass accumulation faster or slower than under aerobic conditions and why
Slower
Because anaerobic resperiation is less efficient - terminal electron acceptor oxygen yields more energy therefore most biomass created
Do anaerobic conditions favpur full or partial breakdown of organic matter
Partial
What is radiative forcing
Amount of sun’s energy retained on earth compared with how much is lost to space
How much carbon is stored in permafrost compared to the atmosphere
2 times
Describe runaway climate change in terms of permafrost
Melting of permafrost causes warming which causes more permafrost to melt - viscous cycle
What is the electron donor and terminal electron acceptor in methanogenesis
Hydrogen is electron donor
Carbon dioxide is terminal electron acceptor
What is the role of cofactors in methanogrnrsis
Carry carbons from carbon diocide, removing oxygen at each step to form water
What carries out the proton motive force in methanogenesis and why
Sodium channels rather than proton pumps as the hydrogen is needed to produce water
What microbes do methanogens form a close physical association with
Sulphur reducing bacteria
What is the sulphate-methane transition zone and what environments will it be found in
The point where the products of suphate reduction meets regions of methane produciton, can be cm or metres thick
Found in all anoxic environments
What products of methanotrophic archaeon are scaveneged by SRB and what are they used for
Hydrogen or other unknown intermediates which are used as electron donors
What is usually limiting in methane oxidation
Sulphate
What utilises methane in fresh water and soil habitats
Gamma and alpha proteobacteria
What is produced by prteobacteria utilising methane
Use monooxygenase enzyes to convert methane into formaldehyde and biomass
