2. • 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).
3. • Chemicals enter storage compartments - sinks
• Amount that moves between compartments is the flux
4. 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
5. Geological Cycle
• The formation and change of Earth materials
through physical, chemical, and biological
processes
6. The Tectonic Cycle
• Lithosphere is comprised of several plates
floating on denser material
• Plates move slowly relative to each other –
plate tectonics
7. • Divergent plate boundaries occur at spreading
ocean ridges
• Convergent plate boundaries occur when
plates collide
8. Biogeochemical Cycles in Ecosytems
• Begins with inputs from reservoirs such as
atmosphere, volcanic ash, stream runoff, ocean
currents, submarine vents
• Chemicals cycle through physical transport
and chemical reactions (e.g. decomposition)
• All ecosystems “leak” chemicals to other
ecosystems.
9. Carbon Cycle
• Carbon is vital for
life but is not
abundant
• Enters biological
cycles through
photosynthesis to
produce organic
forms of carbon
11. • Large inorganic carbon reservoir in oceans
• Dissolved CO2 is converted to carbonate and
bicarbonate
• Transferred from land by rivers and wind
12. Fossil Fuels
• Decomposition of dead organisms may be
prevented by lack of oxygen or low
temperatures
• Burial in sediments over thousands or millions
of years transforms the stored organic carbon
into coal, oil or natural gas
15. 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
16. 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.
17. 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.
18. 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.
19. 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
20. 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
21. 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
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