Abby, Maggie, Maddy
Nitrogen and Phosphorus Cycles
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The atmosphere is 78% Nitrogen
Steps in the Nitrogen Cycle:
1. Nitrogen fixation- conversion of gaseous nitrogen into ammonia (NH3). Nitrogen
is being fixed (by nitrogen fixing bacteria, eg. Cyanobacteria) into a form
organisms can use
2. Nitrification- conversion of ammonia (NH3) into nitrate (NO3). Soil bacteria
converts ammonia into nitrite, soil oxidized nitrite into nitrate
3. Assimilation- plant roots absorb nitrate (NO3), ammonia (NH3), or ammonium
(NH4) and incorporate the nitrogen from those into plant proteins or nucleic acids
4. Ammonification- conversion of biological nitrogen (from animal waste or dead
organisms) into ammonia (NH3)
5. Denitrification- reduction of nitrate (NO3) into gaseous nitrogen. Denitrifying
bacteria reverse the action of nitrogen fixing bacteria, returning N2 into the
atmosphere
Phosphorus cycle has no gas phase
Generally found as phosphate ions (PO34) or hydrogen phosphate ions (HPO42)
 Slowly released from terrestrial rocks by acid rain/ weathering
 Dissolves into soil and is taken in by plants
Oceans
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About 71% of the Earth’s surface is oceans. More than half of that is below 10,000 feet
deep. The average salt content of seawater is about3.5%
Oceanic evaporation is the primary source for precipitation.
Ocean temperatures affect climate and wind patterns
About 250,000 marine life forms are known, many more organisms are still to be
discovered.
Oceans are divided into specific zones:
 Aphotic- Where less than 1% of sunlight penetrates.
 Benthic- The deepest part of the ocean where you can find organisms.
 Neritic- Starts at the low tide mark and ends at the edge of the continental
shelf. It has a relatively shallow depth, the deepest being 650 feet. Its
water is well- oxygenated, there is low water pressure, and there is
available light for photosynthesis. Its temperature and salinity levels are
relatively stable. There is a high biodiversity. This zone is also known as
the sub littoral or photic zones.
 Oceanic- The region of open sea beyond the edge of the continental shelf.
It includes 65% of the ocean’s open water.
 Pelagic- All open ocean regions.
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 Photic (Euphotic)- The depth of the water that is exposed to sufficient
sunlight for photosynthesis to occur. It is biologically diverse.
The ocean conveyor belt moves cold, salty, deep-sea water from higher to lower latitudes.
The Atlantic Ocean gets its cold, deep water from the Arctic Ocean. The Pacific Ocean
and the Indian Ocean get their cold, deep water from the water surrounding Antarctica.
The ocean’s currents are affected by wind from the atmosphere.
El Nino changes the direction of winds and causes temperature changes throughout the
Pacific Ocean
Human sewage contaminates seafood and increases the threat to public health.
Offshore mining and oil drilling pollute the neritic province with oil and other
contaminates.
Global Warming
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Sunlight is reflected back by greenhouse gases that absorb and trap infrared radiation.
Greenhouse gases emitted are CO2 (82%), CH4, N2O, and CFCs.
CO2 levels are so high due to deforestation and internal combustion engines
The capacity of various gases to affect the balance of energy is called their radioactive
force.
Impacts:
 Changes in Weather Patterns (higher temperature, increased rainfall)
 Displacement of people and property loss along coastal areas
 Increased amount of forest fires
 Rising sea level (due to glacier melting)
 Health effects  increase of heat related deaths, increased cases of waterborne
diseases such as malaria and cholera
 Loss of biodiversity
 Release of methane from hydrates into coastal sediments
Large deposits of methane into ocean
Thawing of permafrost also releases methane
Reduce Climate change by making more efficient cars, rely more on renewable energy
sources, and slow the rapid process of deforestation
Ozone
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Ozone is formed O2 + UltraViolet radiation (HV)  O+O, O+ O2 = O3
Ozone is found in the stratosphere
Thinning of ozone is due mainly to CFCs (chlorine reacts with ozone, breaking it apart)
CFCs are found in refrigerators, aerosols, and cleaning solvents. Released into the
atmosphere
Bromine is more effective in stratospheric ozone depletion, while chlorine is more
abundant
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Effects:
 Increases in skin cancer and skin damage
 Increases in cataracts of the eye
 Reduction in crop production
 Reduction in photo plankton growth, cumulative effects on food webs
 Increases in mutations, UV radiation causes changes in DNA structure
 Cooling of the stratosphere
 Reduction in the body’s immune system
 Climatic Change