A4 - Biogeochemical Cycles

Biogeochemical Cycles

• Biogeochemical cycles are the cyclical movement of chemical elements and compounds between biotic and abiotic components of ecosystems.
• Chemicals are constantly recycled in ecosystems.
• Water plays a key role in biogeochemical cycles due to its chemical and physical properties, notably its ability to act as a universal solvent and its hydrogen bonding.
• Key cycles include carbon, oxygen, nitrogen, phosphorus, and sulfur.

Necessity of Cycles

• Limited matter in ecosystems necessitates constant recycling of chemicals.
• Essential nutrients are obtained from the recycling of matter through both biotic and abiotic components.
• The main biogeochemical cycles are oxygen, carbon, nitrogen, sulfur, and phosphorus cycles.

The Carbon Cycle

• Carbon cycles rapidly and slowly.
• Rapid cycling involves processes like photosynthesis, respiration, combustion, and ocean uptake.
• Slow cycling includes processes like weathering and the formation and decomposition of fossil fuels.
• Carbon sinks like trees, fossil fuels, oceans, and limestone rock store carbon for long periods.

Human Impacts on the Carbon Cycle

• Mining fossil fuels increases atmospheric carbon dioxide (CO2).
• Deforestation increases CO2.
• The greenhouse effect traps heat from the sun.
• Increased atmospheric CO2 causes global warming.
• Global warming increases the average temperature on Earth.
• Increased CO2 levels in oceans cause ocean acidification.

The Nitrogen Cycle

• Nitrogen (N2) makes up 78.1% of Earth's atmosphere.
• Organisms need nitrogen to produce proteins and DNA.
• Atmospheric nitrogen cannot be used directly by organisms.
• Nitrogen fixation converts atmospheric nitrogen into ammonia (NH3), which can be used by plants.
• Plants convert ammonia into nitrates.
• Animals obtain nitrogen by eating plants or other animals.
• Excess nitrates are converted back into atmospheric nitrogen by denitrification.

The Phosphorus Cycle

• Phosphorus is essential for bones, teeth, and cellular materials like DNA and ATP.
• Does not cycle in the atmosphere, mostly found in soil and water.
• Phosphorus is stored in rocks and released through weathering and erosion .
• Key part of the phosphorus cycle is percolation and leaching, affecting water cycles.

The Sulfur Cycle

• Sulfur is found in rocks, coal, and oil.
• Volcanic activity, geologic uplift, and burning fossil fuels release sulfur dioxide (SO2).
• Sulfates are returned to Earth through acid precipitation.
• Bacteria enable plants to use sulfates.
• Decomposition returns sulfur to soil.
• Some sulfur is redeposited in rocks.

Acid Decomposition

• Acid deposition (also called acid rain) occurs when sulfur released into the atmosphere reacts with water to form sulfuric or sulfurous acid.
• This can alter pH and leach nutrients from soil.
• Human activities release significantly more sulfur than natural processes.

Eutrophication

• Eutrophication is excessive nutrient (especially phosphorus) input into a body of water.
• It leads to algal blooms, reducing light penetration and oxygen levels.
• Dead organisms cause the release of more nutrients and organic materials, which further depletes oxygen.
• This results in the death of aquatic organisms (hypoxia).
• Decomposers then proliferate, reducing oxygen levels even further.

Energy and Matter Transfer

• Energy is involved in every step of biogeochemical cycles.
• Water and energy link biogeochemical cycles through ecological interactions.

Explore the major biogeochemical cycles that govern the movement of chemical elements within ecosystems. This quiz covers essential cycles such as carbon, nitrogen, and water, highlighting their processes and importance in recycling nutrients. Test your knowledge on how these cycles contribute to the ecological balance.