1. 2.2 - Nutrient Cycles in Ecosystems Nutrients are chemicals required for growth and other life processes. –Nutrients move through the biosphere in nutrient cycles, or exchanges. modes of movement: –biotic processes (ie. decomposition) –abiotic processes (ie. run-off)

2. 2.2 - Nutrient Cycles in Ecosystems Nutrients often accumulate in areas called stores. –Without interference, generally the amount of nutrients flowing into a store equals the amount of nutrients flowing out.

3. 2.2 - Nutrient Cycles in Ecosystems Human activities can upset the natural balance of nutrient cycles. –The following activities can increase the levels of nutrients faster than the stores can absorb them: land clearing agriculture urban expansion mining industry motorized transportation –Excess nutrients in the biosphere can have unexpected and significant consequences.

4. 2.2 - Nutrient Cycles in Ecosystems There are 5 chemical elements required for life: 1.carbon 2.hydrogen 3.oxygen 4.nitrogen 5.phosphorous - cycles in from sedimentary rock cycle between living organisms and the atmosphere

5. Nutrient Cycles: The Carbon Cycle Carbon atoms are a fundamental unit in cells of all living things, and C is an essential part of life- sustaining chemical processes. Carbon can be stored in many different locations. –Short-term storage: in aquatic & terrestrial organisms in CO 2 in the atmosphere as dissolved CO 2 in top layers of the ocean

6. Nutrient Cycles: The Carbon Cycle Longer-term storage: –in middle and lower ocean layers as dissolved CO 2 –in coal, oil and gas deposits in land and ocean sediments the largest long-term carbon stores are found in sedimentary rock & marine sediments http://idw-online.de/pages/en/news264572

7. Nutrient Cycles: The Carbon Cycle Sedimentation is the process that contributes to the formation of sedimentary rock, trapping many long- term stores of carbon.

8. Nutrient Cycles: The Carbon Cycle Layers of soil and decomposing organic matter become buried on land and under the oceans. –under great pressure & over many years, rock forms, and coal, oil & gas form Layers of shells / coral are deposited in sediments on the ocean floor, forming carbonate rocks like limestone over long periods of time. carbon stores = “carbon sinks”

9. Nutrient Cycles: The Carbon Cycle Carbon is cycled through ecosystems in a variety of ways. 1.Photosynthesis: chem. rxn. that transforms solar energy into chemical energy energy from the sun allows CO 2 and H 2 O to react in chloroplasts of plants carbohydrates & oxygen gas are produced

10. Nutrient Cycles: The Carbon Cycle Photosynthesis also occurs in… –cyanobacteria, phytoplankton & algae in oceans

11. Nutrient Cycles: The Carbon Cycle 2. Cellular respiration: –energy released is used for growth, repair and other life processes –CO 2 released back into atmosphere –both consumers & producers perform cellular respiration

12. Nutrient Cycles: The Carbon Cycle 3. Decomposition: decomposers break down large quantities of cellulose cellulose is a carbohydrate that most other organisms cannot break down

13. Nutrient Cycles: The Carbon Cycle 4.Ocean Processes – ocean mixing –CO 2 dissolves in cold, northern waters –cold water sinks –ocean currents flow to the tropics –the water warms & rises –some CO 2 is released –currents carry water back to polar areas

14. Ocean Mixing

15. Nutrient Cycles: The Carbon Cycle 5. Eruptions and fires: volcanic eruptions can release CO 2 via subduction & melting of sedimentary rock forest fires can release CO 2 http://www.brainpop.com/science/earthsystem/carboncycle/ http://www.brainpop.com/science/earthsystem/carboncycle/

16. Nutrient Cycles: The Carbon Cycle

17. Nutrient Cycles: The Carbon Cycle & Human Activities Since the start of the Industrial Revolution (160 years ago), CO 2 levels have increased by 30% from the increased burning of fossil fuels. –The increase in CO 2 levels in the previous 160 000 years was 1% - 3%. –Carbon is being removed from long-term storage more quickly than it naturally would, as we mine coal, and drill for oil and gas. –CO 2 is a greenhouse gas, which traps heat in Earth’s atmosphere.

18. Nutrient Cycles: The Carbon Cycle How does clearing land for agriculture and urban development impact the carbon cycle? See page 77

19. Nutrient Cycles: The Carbon Cycle Clearing land for agriculture and urban development reduces the number of plants that can absorb and convert CO 2. –Vegetation on farmed land does not remove as much CO 2 as natural vegetation does.

20. Nutrient Cycles - The Nitrogen Cycle Nitrogen is very important in the structure of DNA and proteins. In animals, proteins are vital for muscle function (N is found in all amino acids, therefore is made into all proteins) In plants, nitrogen is important for growth. N is a component of chlorophyll molecules (chlorophyll a - C 55 H 72 O 5 N 4 Mg – is the most commonly found form of chlorophyll in terrestrial plants), therefore is essential for photosynthesis

21. Nutrient Cycles - The Nitrogen Cycle The largest store of nitrogen is in the atmosphere in the form of N 2 (gas)  a form that is unusable by most organisms. Approximately 78% of the Earth’s atmosphere is N 2 gas. Nitrogen is also stored in oceans, and as organic matter in soil. Smaller nitrogen stores are found in terrestrial ecosystems and waterways.

22. Nutrient Cycles - The Nitrogen Cycle Nitrogen is cycled through processes involving plants: 1.Nitrogen fixation 2.Nitrification 3.Uptake

23. Nitrogen Fixation Nitrogen fixation is the conversion of N 2 gas into compounds containing nitrate (NO 3 – ) or ammonium (NH 4 + ) –Both nitrate and ammonium compounds are usable by plants. –Nitrogen fixation occurs in one of three ways…

24. Nitrogen Fixation 1.In the atmosphere - lightning provides the energy for N 2 gas to react with O 2 gas to form nitrate and ammonium ions. –Compounds formed by these ions then enter the soil via precipitation –This only accounts for a small amount of nitrogen fixation.

25. Nitrogen Fixation 2.In the soil - nitrogen-fixing bacteria like Rhizobium in the soil convert N 2 gas into ammonium ions (NH 4 + ) –These bacteria grow on the root nodules of legumes (ie. peas) –The plants provide sugars, while bacteria provide plants with usable nitrogen from the atmospheric nitrogen they took in –A happy, mutualistic relationship!

26. Nitrogen Fixation 3.In the water - some species of cyanobacteria also convert N 2 gas into ammonium during the process of photosynthesis.

27. Nitrogen Fixation

28. Nitrification & Uptake Nitrification occurs when certain soil bacteria convert ammonium into nitrate (NO 3 – ) takes place in 2 stages & involves nitrifying bacteria in soil 1.NH 4 +  nitrite (NO 2 – ) 2.NO 2 –  nitrate (NO 3 – ) each stage is completed by a different type of nitrifying bacteria

29. Nitrification & Uptake Nitrates enter plant roots via uptake –nitrates incorporated into plant proteins –herbivores eat plants & use nitrogen for DNA and protein synthesis

30. Nitrification & Uptake some decomposer bacteria… –take N trapped in proteins & DNA of dead organisms and convert it into NH 4 + –decompose urea from animal waste products & convert it into NH 4 +

31. Denitrification Nitrogen is returned to the atmosphere via denitrification. –denitrifying bacteria in terrestrial & aquatic ecosystems convert nitrates back to N 2 gas –nitrogen (in the form of NH 3, and NO x gases) is also returned to the atmosphere through volcanic eruptions

32. How Nitrogen is Removed from Ecosystems Excess nitrogen dissolves in water, enters the waterways, and washes into lakes and oceans.  Unused nitrogen settles to ocean / lake bottoms as sediment.  Eventually, sediment will become trapped in rocks, and will not be released again until the rocks weather.

33. Human activities can also affect the nitrogen cycle... Due to human activities, the amount of nitrogen in the ecosystem has doubled in the last 50 years. Burning fossil fuels and treating sewage releases NO and NO 2. –Burning (ie. forests, grasslands) also releases nitrogen compounds that increase acid precipitation in the form of nitric acid (HNO 3 ).

34. Human activities can also affect the nitrogen cycle... Agricultural practices often use large amounts of nitrogen-containing fertilizers that fix atmospheric nitrogen into N compounds that crops can use. –excess nitrogen leaches into waterways, promoting huge growth in aquatic algae = eutrophication –algal blooms deprive other aquatic plants of sunlight & O 2 –O 2 is also used up in the decomposition of dead algae –aquatic animals also deprived of oxygen –algal blooms can also produce neurotoxins that poison animals & move through the food web http://www.brainpop.com/science/diversityoflife/algae/

35. Algal Bloom

36. Monoculture humans grow single crops of legumes (ie. peans, soybeans, peas, rice) over large areas these crops fix atmospheric nitrogen, greatly increasing the rate of N-fixation in these areas

37. Match each term on the left with the correct definition on the right.

39. The Phosphorous Cycle Phosphorous is essential for life processes in plants and animals. –P is a part of the ATP molecule (carries energy in living cells) –P promotes root growth, stem strength and seed production –P and Ca are important for strong bones in animals

40. The Phosphorous Cycle P is not stored in the atmosphere. –Instead, it is trapped in phosphates (PO 4 3–, HPO 4 2–, H 2 PO 4 – ) found in rocks and in the sediments on the ocean floor.

41. The Phosphorous Cycle Weathering releases phosphates from rocks –chemical weathering, via acid precipitation or lichens, releases phosphates –physical weathering, where wind, water and freezing release phosphates –Phosphates are absorbed by plants, which are then eaten by animals. –Weathering doesn’t occur until there is geologic uplift, exposing the rock to chemical and physical weathering.

42. The Phosphorous Cycle Humans add excess phosphorous to the environment through mining for fertilizer components. –Extra phosphorous, often along with potassium, then enters the ecosystems faster than methods can replenish the natural stores. Humans can also reduce phosphorous supplies. –Slash-and-burning of forests removes phosphorous from trees, and it is then deposited as ash in waterways.

43. How Changes in Nutrient Cycles Affect Biodiversity Any significant changes to any of these nutrients (C, H, O, N or P) can greatly impact biodiversity. –Carbon cycle changes contribute to climate change and global warming. Slight temperature fluctuations and changes in water levels can drastically change ecosystems. Changes influence every organism in those food webs. –Increased levels of nitrogen can allow certain plant species to out-compete others, decreasing resources for every species in those food webs. –Decreased levels of phosphorous can inhibit the growth of algal species, which are very important producers in many food chains. Take the Section 2.2 Quiz