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

Plants

OceansFossil fuels

Atmosphere(CO2)

Animals

Respiration, Decomposition

Photosynthesis

ConsumptionCom

bu

stio

n

Diffusion

Limestone

Burial and compaction

Atmosphere 750

Vegetation 610

Soils 1580

CARBON CYCLE

Carbon Cycle cont’d

Two ways that humans have disturbed the cycle:

1. 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

Aquatic plants Aquatic animals

Ocean Floor

Upliftment of the ocean

floor

Phosphorus Cycle

Fertilizer

Phosphate rocks

Erosion

Phosphorus Cycle cont’d

2 chief ways humans intervene with the P cycle:

1. 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)

2. 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.

Phosphorus Cycle cont’d

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:

1. Withdrawing large quantities of fresh water

2. Clearing vegetation from land for agriculture, mining, roads, construction, etc.