Biogeochemical cycles are nature's way of recycling essential elements. These cycles, including water, carbon, nitrogen, phosphorus, and sulfur, move materials through ecosystems. They're crucial for life, connecting living and non-living parts of our planet.

Human activities have a big impact on these cycles. We're changing the balance of elements in the environment through pollution, deforestation, and fossil fuel use. This affects everything from climate to ocean health, showing how interconnected these cycles really are.

Water, Carbon, and Nutrient Cycles

Key processes of biogeochemical cycles

• Water cycle
  • Evaporation: liquid water transforms into water vapor (oceans, lakes)
  • Transpiration: water evaporates from plant leaves (forests, crops)
  • Condensation: water vapor cools and forms clouds (atmosphere)
  • Precipitation: water falls back to Earth as rain, snow, or hail (storms)
  • Infiltration: water soaks into the ground and becomes groundwater (soil)
  • Runoff: water flows over land into bodies of water (rivers, streams)
• Carbon cycle
  • Photosynthesis: plants use sunlight to convert CO2 into organic compounds (glucose)
  • Respiration: organisms release CO2 through cellular respiration (animals, plants)
  • Decomposition: dead organisms are broken down by decomposers, releasing CO2 (soil)
  • Fossil fuel combustion: burning of fossil fuels releases CO2 into the atmosphere (coal, oil)
  • Carbon sequestration: CO2 is stored in biomass, soils, and oceans (forests, grasslands)
• Nitrogen cycle
  • Nitrogen fixation: N2 is converted into usable forms by bacteria or lightning (legumes, soil)
  • Nitrification: bacteria convert ammonia to nitrites and nitrates (soil)
  • Assimilation: plants absorb nitrates and incorporate nitrogen into biomass (roots)
  • Ammonification: decomposers convert organic nitrogen to ammonia (dead organisms)
  • Denitrification: bacteria convert nitrates back to N2 (anaerobic conditions)
• Phosphorus cycle
  • Weathering: phosphorus is released from rocks and minerals (erosion)
  • Assimilation: plants absorb phosphates and incorporate them into biomass (roots)
  • Decomposition: dead organisms release phosphorus back into the environment (soil)
  • Sedimentation: phosphorus settles into sediments in aquatic ecosystems (lakes, oceans)
• Sulfur cycle
  • Weathering: sulfur is released from rocks and minerals (erosion)
  • Assimilation: plants absorb sulfates and incorporate them into biomass (roots)
  • Decomposition: dead organisms release sulfur back into the environment (soil)
  • Sulfur reduction: bacteria convert sulfates to hydrogen sulfide (anaerobic conditions)
  • Sulfur oxidation: bacteria convert hydrogen sulfide back to sulfates (aerobic conditions)

Human impacts on biogeochemical cycles

• Anthropogenic CO2 emissions
  • Fossil fuel combustion and deforestation increase atmospheric CO2 (industry, agriculture)
  • Enhanced greenhouse effect leads to global warming and climate change (sea level rise)
  • Ocean acidification due to increased CO2 absorption affects marine life (coral reefs)
• Nitrogen and phosphorus pollution
  • Agricultural runoff and sewage discharge increase nutrient levels in water bodies (fertilizers)
  • Eutrophication: excess nutrients cause algal blooms and oxygen depletion (dead zones)
  • Biodiversity loss and ecosystem degradation due to eutrophication (fish kills)
• Acid rain
  • Burning of fossil fuels releases sulfur and nitrogen oxides (power plants)
  • Oxides react with water in the atmosphere to form acidic compounds (sulfuric acid)
  • Acid rain damages forests, aquatic ecosystems, and infrastructure (buildings)
• Groundwater depletion
  • Overextraction of groundwater for irrigation and consumption (agriculture)
  • Lowered water tables and reduced water availability (droughts)
  • Saltwater intrusion in coastal aquifers due to groundwater depletion (seawater)

Interconnections and Ecosystem Functioning

Interconnections between biogeochemical cycles

• Nutrient availability
  • Nitrogen and phosphorus cycles provide essential nutrients for plant growth (fertilizers)
  • Limited availability of these nutrients can restrict primary production (plant growth)
• Carbon and nutrient coupling
  • Photosynthesis in the carbon cycle requires nitrogen and phosphorus (enzymes)
  • Decomposition releases nutrients back into the environment, fueling the cycles (bacteria)
• Water cycle and nutrient transport
  • Water cycle facilitates the movement of nutrients through ecosystems (rivers)
  • Runoff and groundwater flow transport nutrients between land and water (erosion)
• Ecosystem productivity
  • Balanced biogeochemical cycles support healthy, productive ecosystems (forests)
  • Disruptions to cycles can lead to reduced productivity and ecosystem degradation (desertification)
• Climate regulation
  • Carbon cycle plays a crucial role in regulating Earth's climate (greenhouse effect)
  • Imbalances in the cycle, such as increased CO2 emissions, can affect global climate patterns (global warming)

Components of the Biogeosphere

• Biosphere: the part of Earth where life exists, including all living organisms (biotic factors)
• Lithosphere: the solid outer layer of Earth, including rocks and soil (abiotic factors)
• Hydrosphere: all water on Earth's surface, including oceans, lakes, and rivers
• Atmosphere: the layer of gases surrounding Earth, crucial for supporting life