Big Question Why Are Biogeochemical Cycles Essential to Long-Term Life on Earth 2
A biogeochemical cycle is the complete path a chemical takes through the Earths four major reservoirs
hydrosphere (oceans rivers lakes groundwaters and glaciers)
lithosphere (rocks and soils)
biosphere (plants and animals).
Chemicals enter storage compartments - sinks
Amount that moves between compartments is the flux
net sink - when input exceeds output
net source - if output exceeds input.
5 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
6 Geological Cycle
The formation and change of Earth materials through physical chemical and biological processes
7 The Tectonic Cycle
Lithosphere is comprised of several plates floating on denser material
Plates move slowly relative to each other plate tectonics
Divergent plate boundaries occur at spreading ocean ridges
Convergent plate boundaries occur when plates collide
Plate movements change the location of continents and alter atmospheric and ocean circulation patterns
Plate boundaries are geologically active producing volcanoes and earthquakes
10 Hydrologic Cycle
97 of water is stored in oceans 2 in glaciers and ice caps 1 as freshwater on land or atmosphere
Drainage basins or watersheds are the area contributing runoff to a stream or river
Vary in size from a hectare to millions of square miles (e.g. Mississipi River drainage basin)
Human impacts include dam construction irrigation stormwater runoff
12 Rock Cycle
Igneous rocks form from molten material such as lava. Broken down by physical and chemical weathering
Sedimentary rocks form from accumulation of weathered material in depositional basins
Metamorphic rocks are formed from sedimentary rocks exposed to heat pressure or chemically active fluids
14 Rock Cycle 15 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.
16 Annual Calcium Cycle in a Forest Ecosystem
Soluble in water and easily lost through runoff
17 Annual Sulfur Cycle In a Forest Ecosystem
Includes gaseous forms (sulfur dioxide and hydrogen sulfide) and cycles much faster than calcium
18 Carbon Cycle
Carbon is vital for life but is not abundant
Enters biological cycles through photosynthesis to produce organic forms of carbon
19 Carbon Cycle in a Pond 20
Large inorganic carbon reservoir in oceans
Dissolved CO2 is converted to carbonate and bicarbonate
Transferred from land by rivers and wind
21 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
22 Global Carbon Cycle 23 Global Carbon Cycle 24
Case of the missing carbon!
Analysis shows contribution of 8 .5 bill. tons into the atmosphere but less than ½ stays therewhere does it go
7 billion from fossil fuels and 1.5 billion from deforestation
25 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.
26 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.
27 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.
28 Case of the missing carbon!
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
29 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
30 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
When organisms die denitrifying bacteria convert organic nitrogen to ammonia nitrate or molecular nitrogen
32 Global Nitrogen Cycle 33 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
34 Global Phosphorus Cycle 35 Phosphate Mining
Impact on landscape by open-pit mining
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