Biogeochemical Cycles

1. Biogeochemical Cycles

2. Something to think about… • A handful of elements combine to form the building blocks of all known organisms. • Organisms cannot manufacture these elements and do not “use them up,” so where do essential elements come from?

3. Objectives: • Identify the elements of Life • Identify and describe the flow of elements (“nutrients”) in each biogeochemical cycle. • Explain the impact that humans have on the biogeochemical cycles.

4. Two Secrets of Survival: Energy Flow and Matter Recycling • An ecosystem survives through a combination of energy flow and matter recycling.

6. Unlike the one-way flow of energy, matter is recycled within and between ecosystems. • As matter moves through these cycles, it is never created or destroyed —just changed.

7. Why is it important that matter is recycled? • They are required to build and maintain an organism

8. Elements of Life

9. Essential Elements • 24 elements are required for life • Macronutrients are required in LARGE quantities • carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. • Micronutrients are required in small/medium quantities, or not at all in some organisms • Copper, sodium, iodine

10. How does matter move through the biosphere? • A biogeochemical cycle is the complete path a chemical takes through the Earth’s four major reservoirs: • atmosphere • hydrosphere (oceans, rivers, lakes, groundwaters, and glaciers) • lithosphere (rocks and soils) • biosphere (plants and animals)

11. Chemicals enter storage compartments -sinks

12. Biogeochemical Cycles in Ecosystems • Biological Processes • any and all activities performed by living organisms; includes eating, breathing, “burning” food, and eliminating waste • Geological Processes • include volcanic eruptions, the formation & breakdown of rock, and major movements of matter within and below the surface of the earth • Chemical/ Physical Processes • include the formation of clouds and precipitation, flow of running water, and the action of lightning

13. Hydrologic (Water) Cycle

14. Carbon Cycle • Carbon is vital for life but is not abundant • Enters biological cycles through photosynthesis to produce organic forms of carbon

15. Carbon Cycle in a Pond

16. Fossil Fuels • Lack of oxygen or low temperatures may prevent decomposition of dead organisms • Burial in sediments over thousands or millions of years transforms the stored organic carbon into coal, oil or natural gas

17. Global Carbon Cycle

18. Nitrogen Cycle

19. Nitrogen Cycle • Essential for manufacturing proteins and DNA • Although 80% of atmosphere is molecular nitrogen, it is unreactive and cannot be used directly • Nitrogen fixation converts nitrogen to ammonia or nitrate

20. Nitrogen Fixation • Some organisms have a symbiotic relationship with nitrogen fixing bacteria • Found in root nodules in some plants, or in the stomach of some herbivores • Nitrogen fixation also occurs through lightning and industrial processes

21. Denitrification • When organisms die, denitrifying bacteria convert organic nitrogen to ammonia, nitrate, or molecular nitrogen

22. Nitrogen Cycle

23. Global Phosphorus Cycle

24. Phosphorus Cycle • No gaseous phase • Slow rate of transfer • Released by erosion of exposed rock • Absorbed by plants, algae, and some bacteria • Exported from terrestrial ecosystems by runoff to oceans • May be returned through seabird guano

25. Impact on landscape by open-pit mining Phosphate Mining

26. Sulfur Cycle In a Forest Ecosystem Includes gaseous forms (sulfur dioxide and hydrogen sulfide);cycles much faster than calcium

27. Calcium Cycle in a Forest Ecosystem Soluble in water and easily lost through runoff

28. Remember… • Biogeochemical cycles of matter pass the same atoms and molecules around again and again. • If you interrupt thecycling, how doesthis affect theecosystem?

29. Case of the missing carbon! • Analysis shows contribution of 8 .5 bill. tons into the atmosphere but less than ½ stays there…where does it go? • 7 billion from fossil fuels and 1.5 billion from deforestation

30. Case of the missing carbon! • Appears oceans are acting as carbon sinks as are forests and grasslands. • But which area is more critical, and which one dominates. • Will these blessings last? • If they stop functioning we could face drastic changes even before 2050.

31. Case of the missing carbon! • Global tests of CO2 show less in the north than the south despite larger northern outputs • Why is this the case? • If land plants are doing the work then there should be a corresponding oxygen increase. • If it is dissolving in the oceans then there should be no added oxygen.

32. Case of the missing carbon! • Results (best guess): • Ocean is soaking up 2.4 billion tons globally • Land plants do the most work in the northern hemisphere • Forests literally breath in the carbon but appetite changes dramatically due to season, amount of sunlight, rainfall, and age of forests • Marine organisms undergo photosynthesis as well • So that leaves about 2.9 units unaccounted for between these groups.

33. Case of the missing carbon! • Biggest threats: • Decline in forest growth • Killing of ocean phytoplankton due to rising sea temperatures • Death of forests due to spread of disease and insects • Melting permafrost layer • Land clearing for development and agriculture • Ofcourse continued output of carbon from fossil fuel burning