Transcript Magnesium, Calcium, and Phosphorus Cycle

Unit 4 –
Nutrient
Cycles in
marine
ecosystems
Magnesium,
Calcium, and
Phosphorus
Cycle
Magnesium:
• Used to
make
chlorophyll
Ca Cycle:
• Ca present in ocean as Ca2+ (calcium
ions)
• From weathering/erosion of rocks;
brought to ocean from runoff of
rivers
• Used by marine organisms to:
– Make corals
– Make shells (mussels, clams, scallops,
etc)—CaCO3
– Make bone—CaCO3
• Fall to seabed when organisms die
• Forms limestone (AKA Calcium
Carbonate CaCO3)/chalk
Calcium Cycle:
= CaCO3
**“Quick lime” = calcium
oxide
**Slaking: mix w/ H2O
The Phosphorous Cycle
• Biological uses: used to make DNA and bone
• Very slow process
• Found only in sedimentary rocks and water
(not in atmosphere)
• Released as rocks erode
• Travels through food chain
• Released by decomposition
The Phosphorus Cycle
Phosphorus occurs only in very minute amounts in the
atmosphere.
The main reservoirs of phosphorus are rock (especially
the mineral apatite) and natural phosphate deposits, from
which the element is released by weathering, leaching,
erosion, and mining for agricultural use.
Some of the phosphorus passes through terrestrial and
aquatic ecosystems as organic phosphorus from plants to
grazers, predators, and parasites. It is returned to the
ecosystem by excretion, death and decay.
In terrestrial ecosystems, organic phosphates are reduced
by bacteria to inorganic phosphates.
The Phosphorus Cycle
The global phosphorus cycle is unique among the major
biogeochemical cycles in having no significant atmospheric
component
Human impacts on the global phosphorus cycle
• Phosphorus fertilizers used in agriculture are derived from
phosphate rock. Most of the phosphate fertilizer combines with
calcium, iron, and ammonium in soil to form insoluble salts and little
escapes in runoff.
• Part of the phosphorus used as fertilizer is removed in crops,
transported far from the point of application and eventually released
as waste in the processing and consumption of food.
• Phosphorus is concentrated in wastes from food processing plants,
feedlots, and sewage plants.
• Most of the phosphorus enrichment of aquatic ecosystems comes
from sewage disposal plants.
• Overenrichment or eutrophication of freshwater ecosystems (where
phosphorus is usually limiting) even more of a problem with
phosphorus than with nitrogen.
• The Phosphorus Cycle
The phosphorus cycle in terrestrial and aquatic ecosystems.
Crash Course: Nitrogen & Phosphorus
http://youtu.be/leHy-Y_8nRs