1. Biogeochemical Cycles

2. The Basics Biogeochemical cycles are the cycle of matter through ecosystems. In general, we can subdivide the Earth system into: atmosphere (air)hydrosphere (water) lithosphere (land)biosphere (living organisms) By matter we mean: elements (carbon, nitrogen, oxygen) or molecules (water)

3. Key Terms Pools (reservoirs) = where nutrients reside for varying amounts of time Flux = movement of nutrients among pools, which change over time and are influenced by human activities Sources = pools that release more nutrients than they accept Sinks = accept more nutrients than they release

4. The Carbon Cycle

5. Carbon is the main element of all living organisms. It is also found in the atmosphere as carbon dioxide and in the oceans and lithosphere as carbonates. Most of Earth’s carbon is trapped in the lithosphere (so it’s a sink) and little is in the atmosphere The carbon dioxide that is present in the atmosphere plays an important role in regulating the Earth’s temperature.

6. The Path of Carbon Carbon from the air is taken up by plants via photosynthesis and passed to consumers and decomposers through consumption and decomposition. It is then returned to the atmosphere via respiration by producers, consumers and decomposers. Carbon from decomposition can also make its way through the soil and become compressed into rock, forming fossil fuels.

7. The Path of Carbon Carbon dioxide from the atmosphere also dissolves in the oceans and combines with water to form carbonic acid and carbonates. The carbonates get incorporated into the shells of marine invertebrates and then returned to the sediment via decomposition. Volcanic activity then returns the carbon dioxide to the atmosphere. (remember subduction zones (ocean crusts meet continental crusts) The weathering of exposed rocks releases carbonates back into the ocean.

8. Human Influence The combustion of fossil fuels moves carbon from the lithosphere to the atmosphere. Cutting forests and burning fields moves carbon from organisms to the air. Farm and domestic animals release waste methane gas (CH 4 ) through the oxidation of carbon in their food.

9. The Carbon CycleCarbon Cycle

10. The Phosphorus Cycle

11. Phosphorus is a key component of cell membranes, DNA, RNA, ATP and ADP No significant pool of phosphorus exists in the atmosphere Limited mainly to soil and water Nearly all P is in living organisms or in rocks, especially on ocean floor (because the ions do not dissolve well in water).

12. The Path of Phosphorus Most phosphorus is within rocks and is released by weathering into water and soil. Terrestrial plants take up phosphates from the soil and incorporate it into their tissues. Aquatic plants and phytoplankton take up phosphates from the water. Animals then eat the plants and other animals and assimilate it into their tissues.

13. The Path of Phosphorus Animal wastes release phosphates back into the water and soil. Bacterial decomposers convert organic phosphate to inorganic phosphate and return it to the water and soil.

14. Human Influence Excessive use of fertilizers used in agriculture, places phosphorus loads on the terrestrial phosphorus cycle. Runoff containing phosphorus causes eutrophication (algal blooms) of aquatic systems and loss of dissolved oxygen (dead zones/hypoxia) Mining rocks for fertilizer moves phosphorus from the soil to water systems via increased surface erosion and directly from the agricultural runoff. Urban wastewater discharge also releases phosphorus from detergents and waste.

15. The Phosphorus CyclePhosphorus Cycle

16. The Nitrogen Cycle

17. Nitrogen comprises 78% of our atmosphere, and is contained in proteins, DNA and RNA Nitrogen gas not available to living organisms. Nitrogen gas must be fixed to a chemically usable form called nitrates or nitrates.

18. The Path of Nitrogen Nitrogen fixation = Nitrogen gas is combined (fixed) with hydrogen by nitrogen-fixing bacteria to become ammonia (NH 3 ) Nitrification = bacteria then convert ammonia into nitrite (NO 2 ) and nitrate (NO 3 ) ions Assimilation = plants take up the nitrates from the soil and incorporate them into amino acids in their tissues. Animals then eat the plants and incorporate the amino acids into their own tissues.

19. The Path of Nitrogen Ammonification or Mineralization = Decomposers convert the amino acids back into ammonia (NH 3 ) and return it to the soil. Nitrifying bacteria then convert the ammonia back in to nitrates and nitrites. Denitrification = denitrifying bacteria convert nitrates in soil or water to gaseous nitrogen (N 2 ), releasing it back into the atmosphere, thereby completing the cycle.

20. Human Influence Destroying forests and plants removes organic nitrogen from an ecosystem. In contrast commercial fertilizers add too many nitrates to the system. Human wastes from WWTP and untreated sewage into rivers, streams and estuaries adds further nitrogen loads to the aquatic system. Automobiles and power plants emit nitrogen oxide, which reacts with oxygen to form ozone. Ozone is highly reactive and detrimental to living organisms. Nitric oxide compounds (NOx) can combine with oxygen gas to for nitrogen dioxide, which reacts with water to form nitric acid, a form of acid rain.

21. The Nitrogen CycleNitrogen Cycle

22. The Sulfur Cycle

23. Sulfur is an important element for proteins. Mainly found in rocks and soils as sulfate minerals, however does involve an atmospheric component.

24. The Path of Sulfur Hydrogen Sulfide from the air is converted by chemosynthetic bacteria into inorganic sulfates, sulfuric acid, and or elemental sulfur. Atmospheric hydrogen sulfide can also be converted by aquatic photosynthetic bacteria into organic as well as inorganic sulfates. Also in the atmosphere, hydrogen sulfide quickly breaks down into sulfur dioxide, where it combines with water vapor to form acid rain. Volcanic activity also releases atmospheric hydrogen sulfide.

25. The Path of Sulfur Weathering exposes sulfates from rocks into the soil and aquatic systems Plants and other photosynthetic organisms assimilate the sulfates into their tissues. Animals eat the plants and assimilate sulfates into their tissues. Death and decomposition convert organic sulfates into inorganic sulfates.

26. Human Influence Emissions from coal burning power plants dump enormous amounts of hydrogen sulfide and sulfate particles into the atmosphere. Winds and storm systems carry the particles over vast distances creating a global acid rain problem.

28. Nutrient Storehouses Fig. 5–3 Major nonliving & living storehouses of elemental nutrients.

29. The Hydrologic Cycle

30. Hydrologic cycle = summarizes how liquid, gaseous and solid water flows through the environment *Main drivers of this cycle are sun and gravity! –Oceans are the main reservoir Evaporation = water moves from aquatic and land systems to the atmosphere Transpiration = release of water vapor by plants Precipitation = condensation of water vapor as rain or snow Infiltration= water moves through soil and into groundwater storage.

31. Human Influences Depletion of fresh surface and ground water by the draining of lakes, rivers, groundwater and other reservoirs. Through the destruction of forests the levels of evapo-transpiration are reduced as well as increased erosion which reduces seepage into groundwater. Emitting pollutants changes the nature of precipitation.

32. The Water CycleWater Cycle

34. Approximate location of maximum subsidence in the United States identified by research efforts of Dr. Joseph F. Poland (pictured). Signs on pole show approximate altitude of land surface in 1925, 1955, and 1977. The site is in the San Joaquin Valley southwest of Mendota, California.