1. Carbon, Nitrogen and Phosphorus cycles
Nutrient Cycles
Carbon, Nitrogen and Phosphorus cycles

2. Nutrients
Nutrients are chemicals that are required for plant and animal growth and other life processes
Nutrients are accumulated for short or long periods of time in Earth’s atmosphere, oceans and land masses
Scientists refer to these accumulations as STORES
Biotic and abiotic processes can cause nutrients to flow in and out of stores  this continuous flow of nutrients are called nutrient cycles

3. Nutrient Cycles
There are 5 chemical elements (nutrients) that limit the amount of life possible in an ecosystem:
Carbon
Hydrogen
Oxygen
Nitrogen
These four are cycled between living organisms and the atmosphere
Phosphorus
Enters the environment from sedimentary rock

4. Carbon Cycle
All living things contain billions of carbon atoms in their cells
Carbon is an essential component in the chemical reactions that sustain life, such as cellular respiration

5. Where Carbon is stored Short term carbon stores include:
Vegetation on land
Plants in oceans
Land-based and marine animals
Decaying organic matter in soil
In the atmosphere as carbon dioxide (CO2)
In the top layers of the ocean in its dissolved form

6. Where Carbon is Stored Long term carbon stores include:
In the middle and deep layers of the ocean as dissolved CO2
Coal deposits
Oil and gas deposits
Coal, oil and gas are fossil fuels that are formed from dead plants and animals
Marine sediments and sedimentary rock
This is the largest long-term carbon store

7. Sedimentation
Sedimentation = the process that contributes to the formation of sedimentary rock
Soil particles and decaying and dead organic matter accumulate in layers on the ground/bottom of the ocean and are turned into rock by slow geological processes over a long period of time

8. How Carbon is cycled
There are several ways in which carbon is cycled through ecosystems, including:
Photosynthesis
Cellular respiration
Decomposition
Ocean processes
Natural events
Volcanoes
Large-scale forest fires

9. Photosynthesis
Photosynthesis is a chemical reaction that converts solar energy into chemical energy
During photosynthesis, carbon (in the
form of CO2 in the atmosphere) enters
through the plants and reacts with water
in the presence of sunlight to produce
carbohydrates and oxygen
Energy + 6 CO2 + 6 H2O  C6H12O6 + 6 O2

10. Cellular Respiration
Cellular respiration is the process in which both plants and animals release CO2 back into the atmosphere by converting carbohydrates and oxygen into CO2 and water
During cellular respiration, energy is released within the cells of organisms and can be used for growth, repair and reproduction.
CO2 gas is released as a waste product
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy

11. Decomposition
Decomposition is the breaking down of dead organic matter
Decomposers, such as bacteria and
fungi, convert organic molecules (such
As cellulose) back into CO2, which is
released into the atmosphere

12. Ocean Currents
CO2 dissolves in cold ocean waters found at high latitudes
The cold water sinks and moves slowly in deep water currents towards the tropics
In the warm tropics, the water rises as it warms and mixes with the middle and top layers of the ocean
At the surface, some CO2 is released to the tropical atmosphere while the ocean currents move the warmed water back towards the polar areas

13. Natural Events Some carbon dioxide is released from volcanoes
Some carbon dioxide is slowly released from decomposing trees
Some carbon dioxide is rapidly released during forest fires

14. Human Activities and Carbon
Human activities that impact the carbon cycle include:
Industry
Motorized transportation
Land clearing
Agriculture
Urban expansion
Since the Industrial Revolution (1850s) the amount of CO2 in the atmosphere has increased by 30%
It only increased ~ 3% during the previous 160,000 years!

15. Global Warming
Human activities that involve burning fossil fuels have reintroduced carbon into the cycle that was removed from it long ago
So much carbon is released so quickly that the natural carbon cycle can no longer move all of it into stores
CO2 that is stored in the atmosphere (because it has no where else to go) is a greenhouse gas, which contributes to global warming 

16. Global Warming
Clearing land for agriculture and the expansion of cities reduces the total amount of carbon taken from the atmosphere by plants during photosynthesis
Farmed plants do remove some carbon from the atmosphere through photosynthesis, but not as much as natural vegetation does

17. Nitrogen Cycle
Nitrogen is an important component of DNA and proteins, which are essential for the life processes that take place inside cells
Nitrogen is essential for muscle function in animals and for growth in plants

18. Where Nitrogen is Stored
The largest store of nitrogen is in the atmosphere as nitrogen gas (N2)
Other major stores of nitrogen include oceans and organic matter in soil
Smaller stores include living organisms, lakes and marshes

19. How Nitrogen is Cycled
Most organisms cannot use nitrogen in the form of N2, so much of the nitrogen cycle involves processes that make nitrogen available to plants and animals
Some of these processes include:
Nitrogen fixation = when nitrogen gas (N2) is converted into compounds that contain either nitrate (NO3) or ammonium (NH4)
Nitrogen fixation occurs in 3 ways:
In the atmosphere
In the soil
In water bodies

20. Nitrogen Fixation - Atmosphere
Nitrogen fixation in the atmosphere occurs when lightning converts N2 into NO3 compounds
This NO3 then enters terrestrial and aquatic ecosystems through the rain

21. Nitrogen Fixation - Soil
Nitrogen fixation in the soil occurs when nitrogen-fixing bacteria that lives in the root nodules of legumes and other plants converts N2 into NH4 during decomposition
The plants supply the bacteria with food (sugars) and the bacteria supply the host with nitrogen needed for growth

22. Nitrogen Fixation - Water
Nitrogen fixation in water bodies occurs when certain species of cyanobacteria fix N2 into NH4
Nitrogen-fixing cyanobacteria make the nitrogen compounds available to plants in the surface waters of oceans, wetlands and lakes

23. Nitrification and Uptake
Nitrification is when NH4 is converted into NO3
This occurs in two steps:
Certain species of nitrifying bacteria in the soil convert NH4 into NO2 (nitrite)
Different species of nitrifying bacteria in the soil then convert the NO2 into NO3 (nitrate)
Once nitrate is available in the soil it can enter plant roots and eventually be incorporated into plant proteins
When these plants are consumed by herbivores and omnivores, they incorporate nitrogen into the proteins in their tissues

24. How Nitrogen is Returned
Nitrogen is returned to the atmosphere in a process called DENITRIFICATION
In a series of chemical reactions, denitrifying bacteria convert nitrate (NO3) back into nitrogen gas (N2)
Nitrogen is also returned to the atmosphere as ammonia (NH3) in volcanic ash, nitrogen oxide and nitrogen dioxide

25. How N is removed from Ecosystems
NO3 and NH4 that are not taken up by plants mix with rainwater and are washed from the soil into ground water and streams
This unused nitrogen may settle to ocean, lake or river bottoms in sediments
Eventually these sediments will form rock and the nitrogen will be trapped until centuries of weathering releases it back into the water

26. Human Activities and Nitrogen
Human activities have doubled the available nitrogen in the biosphere in the past 50 years
Millions of tonnes of nitrogen are added in the form of NO and NO2 as a result of fossil fuel combustion
Clearing forests and grasslands by burning also releases trapped nitrogen into the atmosphere
These compounds eventually return to terrestrial and aquatic ecosystems as acid rain (HNO3) 
Chemical fertilizers that fix N2 into nitrogen compounds that crops can use are used in agriculture
The excess nitrogen that is not used can escape back into the atmosphere or can be washed or leached (leak out of) from the soil and end up in water systems
This can can lead to algae blooms, which deprive other aquatic plants of sunlight and oxygen, causing death

27. Algae Blooms

28. Phosphorus Cycle
Phosphorus is essential for a variety of life processes in plants and animals
In plants, phosphorus contributes to root development, stem strength and seed production
In humans, a large amount of phosphorus is found in bones

29. Where Phosphorus is Stored
Phosphorus is NOT stored in the atmosphere as a gas  it is trapped in phosphate (PO4, HPO4, and H2PO4)
This phosphate is found in phosphate rocks and in the sediments of ocean floors

30. Where Phosphorus comes from
Weathering (the process of breaking down rock into smaller fragments) releases phosphate into the soil
Chemical weathering is when a chemical reaction causes phosphate rocks to break down and release phosphate into the soil
This can be caused by ACID RAIN or from the chemicals released by lichens

31. Weathering and Erosion
Physical weathering is when processes, such as wind, rain, and freezing, release particles of rock and phosphate into the soil

32. How Phosphorus is Cycled
On land, plants take up phosphate
through their roots and animals
obtain phosphate by eating the plants
Decomposers break down animal
waste and dead organisms, returning
the phosphorus to the soil to become
available to the producers again
In aquatic ecosystems, phosphate enters as
a result of erosion, leaching, and run-off
Water plants take up some dissolved
phosphate and pass it through the
aquatic food chain

33. How Phosphorus is Cycled
Most phosphate in run-off settles on lake and ocean bottoms
This sediment will eventually form sedimentary rock, and the phosphorus will remain trapped for millions of years
Only when layers of rock become exposed will the phosphorus become available again when the cycle of weathering begins again

34. Human Activities and Phosphorus
Phosphate rock is mined primarily to make commercial fertilizers and detergents
Commercial fertilizers, phosphate-containing detergents, animal waste from large-scale livestock farming, some industrial waste, and untreated human sewage all enter the waterways through run-off and leaching
Clearing of forests by the slash-and-burn method releases the phosphates contained in the trees in the form of ash, which accumulates in the soil and leaches into run off and settles on ocean bottoms and eventually becomes locked up as sedimentary rock

35. Human Activities & the P Cycle
Slash-and-burn causes phosphate
to leach from the ash and run off
into the water supply to settle on
the bottom of water bodies where
it becomes unavailable to organisms
Fertilizers, detergents, manure, waste and sewage contributes additional phosphate to the phosphorus cycle, unbalancing it
Too much phosphorus can negatively affect species that are sensitive to an overload of this nutrient – this can lead to animal death (example: overload of phosphorus in the water can lead to toxic levels in fish that kills them)