The Biogeochemical Cycles

© 2003 John Wiley and Sons Publishers

Fig 4.5 Periodic table of the elements.

D. T. Krohne, General Ecology

© 2003 John Wiley and Sons Publishers

Fig 4.6 Idealized diagram of the geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles.

Modified from D. T. Krohne, General Ecology

15%/year

CO2 & CH4

The Carbon Cycle

© 2003 John Wiley and Sons Publishers

Fig 4.14 The Carbon Cycle.

© 2003 John Wiley and Sons Publishers

Fig 4.15 Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction.

© 2003 John Wiley and Sons Publishers

Fig 4.17 Global flux of carbon, 1850-1990.

Modified from D. T. Krohne, General Ecology

50% fertilizer

(Bacteria)

Microbial mediated processes in the nitrogen cycle

Nitrogen fixation

Cyanobacterialive everywhere in the aquatic environment

Nitrogen fixing bacteriain plant root nodules

Microbes fix nitrogen gas into ammonia that is incorporated into plant tissue

Ammonification (Mineralization)

Refers to the breakdown of organic matter in order to release the organically bound nitrogen as inorganic (mineral) nitrogen in the form of ammonia

Decomposition is the biological process that allows for the process

Nitrifying bacteria (Nitrosomonas and Nitrobacter)

Occurs in oxygen poor or anaerobic environments usually deep in the soil or in muddy sediments

NO3- → NO2

- → NO → N2O → N2 gas

The complete denitrification process can be expressed as a redox reaction

2NO3- + 10e- + 12H+ → N2 + 6H2O

Mangrove swamps are areas where denitrification happens

From http://www.epa.gov/maia/html/nitrogen.html

© 2003 John Wiley and Sons Publishers

Fig 4.19 The global nitrogen cycle.

© 2003 John Wiley and Sons Publishers

Critical Thinking Issue – How are Human Activities Affecting the Nitrogen Cycle?

• Increased nitric acid in soil:• Leaching of magnesium and potassium• Increased aluminum levels• Plant root damage• Changes in microbe communities• Fish kills

• Eutrophication of water bodies• Nitrates in drinking water• Global effects on plant based CO2 uptake

Effects of increased use ofnitrogen fertilizer:

D. T. Krohne, General Ecology D. T. Krohne, General Ecology

Modified from D. T. Krohne, General Ecology

Gaseousphase

Phosphorous cycle in water

© 2003 John Wiley and Sons Publishers

Fig 4.20 The global phosphorus cycle.

Ecosystems and the Gaia Hypothesis

Ecosystem defined: a community of organisms and it’s corresponding abiotic environment through which matter cycles and energy flows

• Wide variation in ecosystems• Boarders can be well defined or vague• Can be natural or artificial, managed or wild• Wide range in scale• Common to all ecosystems: energy flow and cycling of matter

Gaia Hypothesis(es)

• Life has greatly affected the planetary environment

• This alteration has allowed life to persist

• The Earth is a “super-organism” - Life controls the environment in a fashion that is equivalent to the way an organism controls its various systems

• Evolution?

Prepare for a quiz on the topic