BIOGEOCHEMICAL CYCLES

What are Biogeochemical Cycles? Bio – life Geo – Earth - literally “life-earth-chemical” cycle - also called nutrient cycles

Biogeochemical Cycles cont’d natural processes that recycle nutrients from the non-living environment to living organisms, then back to the non-living environment A nutrient is a substance an organism needs to live, grow or reproduce e.g., carbon, oxygen and nitrogen

Biogeochemical Cycles Macronutrients - nutrients needed in large amounts - make up > 95% of all organism’s mass - e.g., C, N, P, K, H, O Micronutrients - the 30+ elements required by organisms in small amounts - e.g., iron, zinc

Carbon Cycle Carbon (C) - basic building block of carbohydrates, fats, proteins and nucleic acids (such as DNA) - the main source of C for organisms is CO2 from the atmosphere or dissolved in surface water

Carbon Cycle cont’d The 3 largest reservoirs of C are : 1. earth’s rocks 2. fossil fuels 3. ocean beds

Carbon Cycle cont’d Atmosphere (CO2) Diffusion Photosynthesis Respiration, Decomposition Combustion Plants Animals Consumption Burial and compaction Oceans Fossil fuels Limestone

CARBON CYCLE Atmosphere 750 Vegetation 610 Soils 1580

Carbon Cycle cont’d Two ways that humans have disturbed the cycle: Forest & brush clearing 2. Burning fossil fuels and wood

Carbon Cycle cont’d These activities have resulted in an increase in the level of carbon dioxide in the atmosphere. 0.036% of the atmosphere is carbon dioxide gas Increases in the level of carbon dioxide linked to global warming

Nitrogen Cycle Nitrogen - organisms need N to make proteins, DNA and other nitrogen compounds - nitrogen gas, N2,makes up 78% of atmospheric volume - N2 cannot be used directly by plants or animals

Nitrogen Cycle cont’d Ways Humans Intervene in N Cycle: 1. Adding excess nitrate and ammonia to aquatic ecosystems in agricultural runoff and discharge of municipal sewage. Leads to eutrophication. 2. Emitting large quantities of nitric oxide when fuel is burned. Leads to acid rain.

Phosphorus Cycle is the movement of P through water, earth’s crust and living organisms P, mainly in the form of phosphates, is an essential plant & animal nutrient P is found is essential to bones, teeth & plant and animal cell membranes

Upliftment of the ocean floor Phosphorus Cycle Phosphate rocks Fertilizer Erosion Upliftment of the ocean floor Aquatic plants Aquatic animals Ocean Floor

Phosphorus Cycle cont’d 2 chief ways humans intervene with the P cycle: Mining large quantities of phosphate rock to produce commercial inorganic fertilisers and detergents - Phosphorus is a non-renewable resource and inefficient use may lead to shortage in the future and global food problems. (ScienceDaily, 2010)

Phosphorus Cycle cont’d Adding excess phosphate to aquatic ecosystems in runoff or animal wastes from cropland, sewage discharge & livestock feedlots - Excess phosphorus leads to growth of algae which blocks waterways. In extreme cases death of the algae results in oxygen deficiency and fish kills.

Hydrologic Cycle describes the movement of H2O between oceans and land masses collects, purifies and distributes Earth’s fixed supply of water organisms are made up primarily of H2O

The Water Cycle Source: http://web.ccsd.k12.wy.us/Science/04/0202watrcycl.html

The Water Cycle CONDENSATION AQUIFER

Hydrologic Cycle cont’d 2 main ways humans interfere in H2O cycle: Withdrawing large quantities of fresh water Clearing vegetation from land for agriculture, mining, roads, construction, etc.