Presented on 20/11/2012

1. Presented by
Shashi Shekhar Singh
SES,JNU,New Delhi

2.  Identify and describe the flow of nutrients
in each biogeochemical cycle
 Explain the impact that humans have on
the biogeochemical cycles

3.  An ecosystem survives
by a combination of
energy flow and matter
recycling.

4. Nutrient Cycles: Global Recycling
Global Cycles recycle nutrients through the earth’s air,
land, water, and living organisms.
Nutrients are the elements and compounds that
organisms need to live, grow, and reproduce.
Biogeochemical cycles move these substances through air,
water, soil, rock and living organisms.

5. Biogeochemical cycles are cycling of chemical
elements or nutrients from the abiotic environment
to organism and then back to the abiotic
environment.
The pathway by which chemical circulate through
ecosystem involve both living (biotic) and nonliving
(geological) components.
Involvedorganism (bio), environmental geology (geo)
& chemical changes (chemical)

6. Most important are:
 The water cycle
 The carbon cycle
 The phosphorus cycle
 The Sulfur cycle
 The nitrogen cycle
 The circulation of chemicals in these biogeochemical cycles and
interactions between cycles are critical for the maintenance of
terrestrial, freshwater and marine ecosystems. Global climate
change, temperature, precipitation and ecosystem stability are all
dependent upon biogeochemical cycles

7. There are strong forces of attraction between molecules of
water
Water exists as a liquid over a wide temperature range
Liquid water changes temperature slowly
It takes a large amount of energy for water to evaporate
Liquid water can dissolve a variety of compounds
Water expands when it freezes.

8. Water Cycle
Rain clouds
Condensation
Transpiration Evaporation
Precipitation Transpiration
to land from plants
Precipitation Precipitation
Evaporation
Surface runoff from land Evaporation
Runoff from ocean Precipitation
(rapid)
to ocean
Infiltration and Surface
Percolation runoff
(rapid)
Groundwater movement (slow)
Ocean storage

9. We alter the water cycle by:
Withdrawing large amounts of freshwater.
Clearing vegetation and eroding soils.
Polluting surface and underground water.
Contributing to climate change.

11.  Mining Fossil Fuels
 Clearing Vegetation:
www.pewclimate.org/ images/figure4.gif

12. Phosphorous Cycle
mining Fertilizer
excretion Guano
agriculture
uptake by weathering uptake by
autotrophs autotrophs
Marine Dissolved leaching, runoff Dissolved Land
Food in Ocean in Soil Water, Food
Webs Water Lakes, Rivers Webs
death, death,
decomposition decomposition
sedimentation settling out weathering
uplifting over
geologic time
Marine Sediments Rocks

13.  We remove large amounts of phosphate from the earth to
make fertilizer.
 We reduce phosphorous in tropical soils by clearing
forests.
 We add excess phosphates to aquatic systems from runoff
of animal wastes and fertilizers.

14. Sulfur Cycle
Sulfur Water Acidic fog and
Sulfuric acid precipitation
trioxide
Ammonia Ammonium
Oxygen sulfate
Sulfur dioxide Hydrogen sulfide
Plants
Dimethyl Volcano
sulfide Industries
Animals
Ocean
Sulfate salts
Metallic Decaying matter Sulfur
sulfide
deposits
Hydrogen sulfide

15. We add sulfur dioxide to the atmosphere by:
Burning coal and oil
Refining sulfur containing petroleum
Convert sulfur-containing metallic ores into free metals such as
copper, lead, and zinc releasing sulfur dioxide into the environment

16. Nitrogen Cycle
Legume nodule bacteria needs 10g of glucose to fix 1g of nitrogen whereas
free living bacteria require 100g of glucose to fix same amount (Odum 1983)

17. We alter the nitrogen cycle by:
Adding gases that contribute to acid rain (Smil, 2000)
Adding nitrous oxide to the atmosphere through farming practices
(Vitousek et al., 1997)
which can warm the atmosphere and deplete ozone (Chapin et al.
2002).
Contaminating ground water from nitrate ions in inorganic fertilizers
Releasing nitrogen into the troposphere through deforestation.

18. Effects of Human Activities on the
Nitrogen Cycle
 Ecosystem processes can increase with nitrogen
fertilization,but anthropogenic input can also result in nitrogen
saturation, which weakens productivity and can kill plants
(Vitousek et al., 1997) → algae blooms
 Decreases in biodiversity both over land and in the ocean can
result if higher nitrogen availability increases nitrogen-
demanding species (Aerts and Berendse 1988)
 NH3 in the atmosphere has tripled as the result of human
activities. It acts as an aerosol, decreasing air quality and
clinging on to water droplets (acid rain).

19. Thank You