Carbon Cycle (11-12)

Question 1

What is the carbon cycle?

Answer 1

the movement of the element carbon through abiotic and biotic reservoirs on the planet.

Question 2

What is a reservoir?

Answer 2

A source of stored carbon.

Question 3

What is a linkage?

Answer 3

Process linking two reservoir of carbon.

Question 4

What is a source and a sink?

Answer 4

Source: a reservoir which releases more carbon than it receives through linkages.

Sink: A reservoir which receives more carbon than it releases through linkages.

Question 5

What os the inorganic carbon cycle?

Answer 5

The cycling of carbon between the ocean, rocks, and the atmosphere.

Takes place on the order of millions of years. Existed before there was biological life on the planet.

In the modern carbon cycle: interacts with the organic processes of the carbon cycle.

Question 6

What are the reservoirs and linkages of the inorganic carbon cycle?

Answer 6

Reservoirs: oceans, atmospheres, rocks.

Linkages: volcanism, solubility pump, chemical weathering, subduction.

Question 7

What is volcanism? What role does it play in the carbon cycle?

Answer 7

Melting of rocks as a result of intense heat from the interior of the planet. Melted rocks and gasses rise towards the surface, ultimately reaching the crust and emerging into the atmosphere.

Chemical composition of rocks undergoing melting will produce different by-products.
- carbonate rocks release CO2 when broken down
- CO2 gas is released along with heat and melted minerals during volcanic activity.

Question 8

What is a solubility pump? What role does it play in the carbon cycle?

Answer 8

The direct exchange of carbon between the atmosphere and the ocean.

CO2 enters and leaves the ocean.

CO2 is soluble in water.
- where the ocean touches the atmosphere, CO2 will dissolve in water
- reacts with water to produce a revers able reaction involving carbonic acid, bicarbonate ions, carbonate ions, and H+.

Question 9

What is chemical weathering? What role does it play in the carbon cycle?

Answer 9

The chemical breakdown of minerals: it can release elements, ions, and molecules. Products of chemical weathering depend on the initial chemical make-up of the mineral being weathered.

Chemical weathering can release ions that are part of the carbon cycle.

Question 10

What are the steps of chemical weathering and its role in the carbon cycle?

Answer 10

1. CO2 reacts with H2O atmosphere and forms carbonic acid, a weak acid.
2. Carbonic acid falls with rainwater and reacts with exposed sedimentary rocks.
   - results in production of calcium ions band bicarbonate ions.
3. Rainfall washes bicarbonate ions and calcium ions into the ocean.
   - where carbon ions have also been produced as a result of the solubility pump.
   - the solubility pump and chemical weathering act together.
4. In the ocean, calcium ions and carbonate ions combine in solution to form calcium carbonate (limestone).
5. Calcium carbonate is used for shell formation - they make it.
6. Calcium carbonate settles on the ocean floor.
   - as animals with shells die and settle.
   - overtime naturally as calcium carbonate suspended in the ocean settles on the sea floor.
7. Forms mineral deposit of calcium carbonate - carbonate rocks.

Question 11

What is subduction? What is its role in the carbon cycle?

Answer 11

When one tectonic plate is pushed under another. The plate being sub ducted eventually melts as a result of the heat in the interior of the planet.
- minerals and organic matter within the tectonic plate melt and join layers of the mantle.

Carbonate rocks from ocean deposits melt during subduction and converts to CO2 gasses (and other elements).

Question 12

What is the formula for residence time?

Answer 12

Reservoir volume / flow rate

Question 13

Are the natural linkages of the natural carbon cycle long term or short term?

Answer 13

Short term with the exception of fossil fuels (takes place over long geological time).

Question 14

What are the reservoirs and linkages to the natural carbon cycle?

Answer 14

Reservoirs: life (organic molecules), photosynthesis, decomposition, cellular respiration, fossil fuels, biological pump, calcium carbonate life.

Anthropogenic linkages and reservoirs.

Question 15

What is photosynthesis? What is its role in the organic carbon cycle?

Answer 15

The process where thermal energy is used to convert atmospheric CO2 into sugars and oxygen.
- primary producers providing energy for higher trophic levels in the food chain.

Role in carbon cycle: the photosynthesis linkage removes atmospheric carbon dioxide (used as energy or building blocks for other organic molecules).

Question 16

What is respiration? What is its role in the organic carbon cycle?

Answer 16

Cellular respiration: the conversion of sugars to biological energy (ATP).

All aerobic life respires.
- Heterotrophs fuel cellular respiration through sugars consumed from primary producers.
- Plants fuel cellular respiration through the sugars produced from photosynthesis.

As sugars are converted to energy (ATP) - gaseous CO2 is released as a by-product.
- gaseous CO2 is released to the atmosphere as a waste product.

Question 17

What is decomposition? What is its role in the organic carbon cycle?

Answer 17

Decomposition: the breakdown of complex organic molecules into simpler molecules through the action of living things.

The breakdown of complex organic molecules releases atmospheric CO2 through cellular respiration.

Some carbon is deposited in the soils as humus (organic component of soil - composed of partially decomposed organic molecules).

Question 18

What are fossil fuels?

Answer 18

Reservoirs of concentrated carbon formed in the ancient geological past from the remains of plant and animal life which did not fully decompose.

Fossil fuels represent long term organic carbon storage in the crust and can be returned to the atmosphere through natural processes.

Question 19

Describe fossil fuel formation.

Answer 19

Over long geological timescales:

1. Dead organic matter buried by sedimentation before it can be fully decomposed.
2. Increasing build-up of sediments - increasing weight compressing organic matter, moves organic matter deeper within the crust (increasing heat exposure).
3. Increased compression and heat - removes trapped water and gases, transforms larger carbon molecules to smaller ones. More and more sediments can be deposited overtime.
4. What remains is concentrated carbon with a minority of other elements.

Question 20

What is a biological pump? What is its role in the organic carbon cycle?

Answer 20

Cycle of photosynthesis, cellular respiration, decomposition, and fossil fuel formation that takes place in marine habitats.

Photosynthetic marine life: primary producers utilize CO2 for photosynthesis
Marine animals: release CO2 during cellular respiration + decomposition (possible fossil fuel formation).

Question 21

Explain the role of marine life and calcium carbonate in the natural carbon cycle?

Answer 21

Shell-forming marine life actively builds calcium carbonate during shell formation.
- dissolved carbon dioxide and Ca2+ present in the ocean as a result of chemical weathering and the solubility pump

Thick mineral deposits of calcium carbonate build up overtime.

Most remain buried in ocean environments.
- tectonic plate movements can bring calcium carbonate deposits onto land.

Question 22

Explain the movement of carbon in the ocean.

Answer 22

Carbon moves between surface waters and deep waters through:

1. Natural upwelling and down welling of dissolved CO2.
2. Movement of living organisms between surface and deeper waters.

Question 23

Why are there seasonal fluctuations of carbon?

Answer 23

Spring - Summer
Plant life engages in growth
- photosynthesis rat increases, takes up atmospheric CO2
- atmospheric CO2 may be fixed in a long term organic structures (wood)

Fall-Winter
Plant growth slows down and ultimately stops (plants become dormant).
- processes involving cellular respiration become the primary process involving CO2 (decomposition of fallen leaves, animal respiration).

Question 24

Explain the global seasonal fluctuations of carbon?

Answer 24

Plant growth is not equal in all regions of the globe.

Seasonal changes in atmospheric CO2 are greatest in the northern Hemisphere. There are very little fluctuations near the equator.

Question 25

What are major anthropogenic linages in the natural carbon cycle?

Answer 25

1. Burning of fossil fuels for energy.
2. Changing land use.
   - removing established vegetation.
   - modifying existing rates of photosynthesis, respiration, and decomposition.
3. Creating concrete from limestone.

Question 26

Which existing natural reservoirs are experiencing an increase in the input of CO2 as a result of increase of atmospheric CO2?

Answer 26

1. Ocean acidification
2. The Greening Hypothesis

Question 27

Explain ocean acidification.

Answer 27

Ocean acidification is the increasing acidity (H+ ions) in the ocean.

Atmospheric CO2 concentrations effect ocean pH as a result of the solubility of CO2 in the water.
- more C2O2 in the atmosphere = more CO2 dissolved in the oceans
- the ocean is a sink for carbon

Question 28

How does ocean acidic action affect shell formation?

Answer 28

Marine life uses Ca2+ and CO32- to build calcium carbonate for their shells.

Increasing H+ concentration in marine environments binds with available CO32- in solution, which results in HCO3-.

This removes the reservoir of dissolved CO32- for the formation of calcium carbonate.

H+ has a higher affinity for CO32- than does Ca2+.
- at high concentrations of H+, existing caCO3 can break down
- existing calcium carbonate shells dissolve at low pH

Question 29

What is the Greening Hypothesis

Answer 29

CO2 is a fertilizer (not a pollutant) that, when increased, will be absorbed by the biosphere and sit adulte greater plant productivity and expand forests.

Question 30

Why is the Greening Hypothesis not accurate?

Answer 30

Greenhouse conditions are not representative of real world conditions.

In the real world, elevated CO2 can I pat nutrient cycles and microbial communities.
- increased growth can modify the limiting nutrient.
- soil microbes decide what happens to the CO2 - they send it to the roots as opposed to creating more biomass
- plants feed the carbon to symbiotic fungi

Adding climate stressors can modify relationships between atmospheric CO2 and plant growth
- example: droughts

Nutrient profiles of plants can be changed
- junk food effect

Question 31

What is the junk food effect?

Answer 31

Increased sugar production in plants results in decrease in production of other organic molecules and reduction in mineral uptake.