Biogeochemical Cycles Nutrients circulate through ecosystems Physical matter

Biogeochemical Cycles

Nutrients circulate through ecosystems • Physical matter is circulated continually in an ecosystem • Nutrient (biogeochemical) cycle = the movement of nutrients through ecosystems – Atmosphere, hydrosphere, lithosphere, and biosphere • 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

Macronutrients • Chemicals organisms need in large numbers to live, grow, and reproduce. • Ex. carbon, oxygen, hydrogen, nitrogen, calcium, and iron.

Micronutrients • These are needed in small or even trace amounts. • Ex. sodium, zinc copper, chlorine, and iodine.

Biosphere Carbon cycle Phosphorus cycle Nitrogen cycle Water cycle Oxygen cycle Heat in the environment Heat Fig. 3 -7, p. 55

CARBON CYCLE

The Carbon Cycle • Short Term Carbon Cycle – Photosynthesis vs. Respiration – Moves carbon though living organisms (Terrestrial and Aquatic Ecosystems) – Carbon can be stored in Biomass • Long Term Carbon Cycle – Carbon stored in the Lithosphere (rocks, fossil fuels, and soil) – Carbon stores in the Oceans – Carbon in the atmosphere as Carbon Dioxide

Effects of Human Activities on Carbon Cycle • We alter the carbon cycle by adding excess CO 2 to the atmosphere through: – Burning fossil fuels. – Clearing vegetation faster than it is replaced. Figure 3 -28

The hydrologic cycle

The Hydrologic Cycle • Water is stored in the environment – Groundwater – Aquiferrs – Rivers and Streams – Lakes and Ponds – Ocean • Water cycles through the environment as: – Evaporatation – Transpiration – Condensation – Precipitation – Intake (seepage)

Groundwater • Aquifers = underground reservoirs of sponge-like regions of rock and soil that hold … – Groundwater = water found underground beneath layers of soil – Water table = the upper limit of groundwater held in an aquifer – Water may be ancient (thousands of years old) • Groundwater becomes exposed to the air where the water table reaches the surface

Human impacts on hydrologic cycle • Damming rivers increases evaporation and infiltration • Altering the surface and vegetation increases runoff and erosion • Spreading water on agricultural fields depletes rivers, lakes and streams • Removing forests and vegetation reduces transpiration and lowers water tables • Emitting pollutants changes the nature of precipitation • The most threatening impact is overdrawing groundwater for drinking, irrigation, and industrial use

The Carbon and Hydrologic Cycle • https: //www. youtube. com/watch? v=2 D 7 h. Zp. IY l. CA&feature=share&list=PL 7 Wxmj. Mi. AYik. N GKPUWe. Zx. BNOh. Ksd 8 Lx. So

Phosphorous Cycle

Question of the Day • The concentration of H+ ions in a solution with a p. H value of 4 is how many times as great as the concentration of H+ ions in a solution with a p. H value of 7? • a. 1 • b. 10 • c. 100 • d. 1, 000 • e. 10, 000

Effects of Human Activities on the Phosphorous Cycle • 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.

Phosphorus • Bacteria are not as important in the phosphorus cycle as in the nitrogen cycle. • Phosphorus is not usually found in the atmosphere or in a gas state only as dust. • The phosphorus cycle is slow and phosphorus is usually found in rock formations and ocean sediments. • Phosphorus is found in fertilizers because most soil is deficient in it and plants need it. • Phosphorus is usually insoluble in water and is not found in most aquatic environments.

Nitrogen Cycle

Effects of Human Activities on the Nitrogen Cycle • We alter the nitrogen cycle by: – Adding gases that contribute to acid rain. – Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. – Contaminating ground water from nitrate ions in inorganic fertilizers. – Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle • Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined. Figure 3 -30

Humans affect the nitrogen cycle • Haber-Bosch process = synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia – Dramatically changed the nitrogen cycle – Humans are fixing as much nitrogen as nature does • Increased emissions of nitrogen-containing greenhouse gases • Calcium and potassium in soil washed out by fertilizers • Acidified water and soils • Moved more nitrogen into plants and terrestrial systems • Reduced biodiversity of plants adapted to low-nitrogen soils • Changed estuaries and coastal ecosystems and fisheries

Human inputs of nitrogen into the environment Fully half of nitrogen entering the environment is of human origin

Nitrogen Fixation • This is the first step of the nitrogen cycle where specialized bacteria convert gaseous nitrogen to ammonia that can be used by plants. This is done by cyanobacteria or bacteria living in the nodules on the root of various plants.

Nitrification • Ammonia is converted to nitrite, then to nitrate Assimilation n. Plant roots absorb ammonium ions and nitrate ions for use in making molecules suc as DNA, amino acids and proteins.

Ammonification • After nitrogen has served its purpose in living organisms, decomposing bacteria convert the nitrogen-rich compounds, wastes, and dead bodies into simpler compounds such as ammonia. Denitrification • Nitrate ions and nitrite ions are converted into nitrous oxide gas and nitrogen gas. This happens when a soil nutrient is reduced and released into the atmosphere as a gas.

The Nitrogen Cycle Mnemonic – Fix. NAAD ANPAN PROCESS Fix – N Fixation PRODUCT Ammonium (NH 3 →NH 4+) Nitrification Assimilation Ammonification Nitrates (NO 2 - → NO 3 -) Proteins Ammonium (NH 3 →NH 4+) Denitrification Nitrogen gas (N 2)

Question of the Day • Which of the following best helps to explain why phosphorus is often a limiting factor in many ecosystems? • a. There is usually a gaseous phase in the phosphorus cycle. • b. Phosphorus cycles very quickly through environments. • c. Under many conditions, phosphorus forms stable insoluble compounds. • d. Phosphate is not readily taken up by plants. • e. There are no anthropogenic sources of phosphorus.

The Sulfur Cycle Figure 3 -32

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.

• https: //www. youtube. com/watch? v=le. Hy. Y_8 n. Rs&feature=share&list=PL 7 Wxmj. Mi. AY ik. NGKPUWe. Zx. BNOh. Ksd 8 Lx. So

Hunting • Over-hunting/hunting of top predators for big game.

Threats to Earth System & Biodiversity

Pollution • CFC’s, CO 2, oil spills.

Habitat Restoration • Trying to rebuild what was ruined.

Reclamation • Returning vegetation to an area that has been mined or disturbed by human use. • This can be done by re-planting, cleaning up pollution, regulations (laws) or any other activity designed to “fix” a destroyed area.

Agriculture • Cut/burn techniques & the loss of habitat.

Abundance of organisms Upper limit of tolerance Few No organisms Population size Lower limit of tolerance No Few organisms Zone of intolerance Low Zone of physiological stress Optimum range Temperature Zone of physiological stress Zone of intolerance High Fig. 3 -11, p. 58