Biogeochemical Cycles

Biogeochemical Cycles describe the flow of essential elements from the environment through living organisms and back into the environment.

Fig 4.5 Periodic table of the elements. © 2003 John Wiley and Sons Publishers

D. T. Krohne, General Ecology

Fig 4.6 Idealized diagram of the geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles. Fig 4.6 Idealized diagram of the geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles. © 2003 John Wiley and Sons Publishers

CO2 & CH4 15%/year Modified from D. T. Krohne, General Ecology

Hydrological Cycle

Hydrological Cycle (water cycle) 1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land 2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water 3. Release – plants transpire, animals breathe and expel liquid wastes

Hydrological Cycle 1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land. 2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water. 3. Release – plants transpire, animals breathe and expel liquid wastes.

Carbon Cycle

Carbon Cycle (carbon is required for building organic compounds) 1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose). 2. Assimilation – plants use CO2 in photosynthesis; animals consume plants. 3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.

Fig 4.15 Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction. Fig 4.15 Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction. © 2003 John Wiley and Sons Publishers

Carbon Cycle 1. Reservoir – atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose). 2. Assimilation – plants use CO2 in photosynthesis; animals consume plants. 3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.

Fig 4.17 Global flux of carbon, 1850-1990. Fig 4.17 Global flux of carbon, 1850-1990. Modified after Woods Hole, “The Missing Carbon Sink, 2000, http://www.whrc.org/science/carbon/carbon.htm, accessed July 5, 2000. © 2003 John Wiley and Sons Publishers

Nitrogen Cycle

50% fertilizer (Bacteria) Modified from D. T. Krohne, General Ecology

Nitrogen Cycle (Nitrogen is required for the manufacture of amino acids and nucleic acids) 1. Reservoir – atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate

Nitrogen Cycle 2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows: Nitrogen Fixation: N2 to NH4+ by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03- by lightning and UV radiation. Nitrification: NH4+ to N02- and N02- to N03- by various nitrifying bacteria.

Nitrogen Cycle 3. Release – Denitrifying bacteria convert N03- back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4+ (ammonification); animals excrete NH4+ (or NH3) urea, or uric acid.

Nitrogen Cycle 1. Reservoir – atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate 2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. 3. Release – Denitrifying bacteria convert N03- back to N2; detrivorous bacteria convert organic compounds back to NH4+ ; animals excrete NH4+, urea, or uric acid.

Effects of increased use of Critical Thinking Issue – How are Human Activities Affecting the Nitrogen Cycle? Effects of increased use of nitrogen fertilizer: 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 Critical Thinking Issue – How are Human Activities Affecting the Nitrogen Cycle? © 2003 John Wiley and Sons Publishers

Phosphorus Cycle

D. T. Krohne, General Ecology D. T. Krohne, General Ecology Gaseous phase Modified from D. T. Krohne, General Ecology

Phosphorus Cycle (Phosphorus is required for the manufacture of ATP and all nucleic acids) 1. Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes 2. Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals 3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

Phosphorus Cycle Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

Effects of Human Activities on the Sulfur Cycle 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.

Acidic fog and precipitation Water Sulfur trioxide Sulfuric acid Acidic fog and precipitation Ammonia Ammonium sulfate Oxygen Sulfur dioxide Hydrogen sulfide Plants Dimethyl sulfide Volcano Industries Animals Ocean Sulfate salts Figure 3.32 Natural capital: simplified model of the sulfur cycle. The movement of sulfur compounds in living organisms is shown in green, blue in aquatic systems, and orange in the atmosphere. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle? Metallic sulfide deposits Decaying matter Sulfur Hydrogen sulfide Fig. 3-32, p. 78

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) This alteration has allowed life to persist 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?

Biogeochemical cycles of other minerals, such as calcium and magnesium, are similar to the phosphorus cycle.