Biogeochemical Cycling PDF

Biogeochemical Cycling Prepared by: Yves Paul M. Montero Nutrient Cycling is the movement of essential elements between organisms and their environment. This process happens in biogeochemical cycles. These cycles have two parts: 1.Reservoir Pool: A large, slow-moving part in the e...

Biogeochemical Cycling Prepared by: Yves Paul M. Montero Nutrient Cycling is the movement of essential elements between organisms and their environment. This process happens in biogeochemical cycles. These cycles have two parts: 1.Reservoir Pool: A large, slow-moving part in the environment. 2.Labile Pool: A smaller, active part that moves quickly between organisms and their environment. Two main types of cycles: 1.Gaseous: The reservoir is in the air or water. 2.Sedimentary: The reservoir is in the Earth's crust.  Use of fertilizer Pollution  Nitrogen Cycle Nitrogen supply – limits rate of primary production Largest reservoir – atmosphere; N2 Stages of Nitrogen Cycle: N fixation, N assimilation, ammonification, nitrification, and denitrification Nitrogen fixers: 1. the cyanobacteria, or blue-green algae, of freshwater, marine, and soil environments 2. Certain free-living soil bacteria 3. bacteria associated with the roots of leguminous plants 4. actinomycetes bacteria, associated with other species of woody plants. Nitrogen fixation Key Players free-living or symbiont with plants (forming root nodules) Rhizobium, Bradyrhizobium, and Azotobacter Cyanobacteria – aquatic and terrestrial Process of Nitrogen fixation 1. Nitrogen Reduction: Enzyme Involvement: The process is catalyzed by the enzyme nitrogenase. ATP Hydrolysis: Nitrogenase requires a significant amount of ATP to power the reaction. Reduction Steps: The enzyme reduces N₂ to NH₃ in a series of steps, involving the transfer of electrons and protons. 2. Ammonia Incorporation: Amino Acid Synthesis: The newly formed NH₃ is quickly incorporated into amino acids. Glutamine Synthetase: The enzyme glutamine synthetase catalyzes the reaction between NH₃ and glutamate to form glutamine. Other Amino Acids: Glutamine can then be used to synthesize other amino acids, such as asparagine and alanine. 1. Nitrogen Fixation: N₂ is converted into ammonia (NH₃) by nitrogen-fixing bacteria 2. Nitrification: NH3 is oxidized to nitrite (NO₂) and then nitrate (NO₃) by nitrifying bacteria 3. Assimilation: Plants absorb nitrate 4. Ammonification: decomposer bacteria break down organic nitrogen compounds, releasing ammonia. 5. Denitrification: Denitrifying bacteria convert nitrate back into atmospheric nitrogen.  Nitrogen pollution - excessive nitrogen have harmful effects on ecosystems and human health. Human activities - primary source of nitrogen pollution; fertilizer, legume crops, fossil fuel burning These inputs often escape into soils and waterways Natural ecosystems are adapted to low-nutrient conditions. Excess nitrogen can favor "weedy" species, leading to reduced biodiversity. Nitrogen enrichment - negative consequences for human health. Excess nitrogen in drinking water, food, and air can pose various health risks. Phosphorus cycle 1. Phosphate Extraction- extracted from phosphate rock mines. 2. Fertilizer Production: Phosphate rock is processed into fertilizers 3. Plant Uptake: Plants absorb phosphate from the soil 4. Runoff: Excess phosphate from fertilizers 5. Erosion: erosion of phosphate-rich rocks. 6. Dissolution: Phosphate rocks can dissolve in water, releasing phosphate ions. 7. Uptake by Aquatic Organisms: Aquatic plants, algae, and other photosynthetic organisms absorb dissolved phosphate. 8. Organic Decomposition: When plants and animals die, decomposers break down their organic matter, releasing phosphate back into the soil. 9. Marine Sedimentation: In aquatic environments, phosphate can accumulate in sediments over time. Sulfur Cycle Sulfur Emissions: released into the atmosphere through the burning of fossil fuels, smelting of ores, and volcanic activity. Atmospheric Deposition: Sulfur compounds in the atmosphere can be deposited to the Earth's surface through dry deposition or wet deposition Sulfates in Soil and Water: Sulfates (SO₄²⁻) can accumulate in soil and water, affecting soil fertility and water quality. Plant Uptake: Plants absorb sulfate from the soil Organic Decomposition: decomposers break down organic matter, releasing organic sulfur. Sedimentation: Sulfur can be deposited in sediments, especially in marine environments. Reduction to Sulfides: In anaerobic conditions, microorganisms can reduce sulfate to sulfide (S²⁻) Oxidation of Sulfides: Iron sulfides can be oxidized back to sulfate by weathering or microbial processes. Carbon Cycle Photosynthesis Respiration Organic Decomposition Ocean-Atmosphere Exchange Sedimentation Fossil Fuel Formation Combustion Volcanic Activity Hydrologic Cycle 1. Evaporation 2. Transpiration 3. Condensation 4. Precipitation 5. Infiltration 6. Percolation 7. Surface Runoff 8. Groundwater Outflow 9. Ocean Storage  P/R < 1 P/R > 1 Import P/R < 1  The Flood Pulse Concept (Junk et al., 1989) Pulsing of the river discharge is the major force controlling biota in river floodplains Lateral exchange between floodplain and river channel, and nutrient recycling within floodplain have more direct impact on biota Agents are plants, nutrients, detritus, and sediments Watch the Video Ecological corridor of Qian'an, a city in China Yanweizhou River, China Kamo River, Kyoto Watershed Biogeochemistry