Nutrient Cycles in Ecosystems

• Gaseous vs. Sedimentary Cycles
• Examples of Biogeochemical Cycles (e.g., carbon, nitrogen, phosphorus, sulfur, water)
• Importance of specific nutrients for plants and animals (e.g., nitrates, phosphates)
• Unidirectional energy flow through ecosystem
• Limiting Factors for population growth (limits of tolerance for each organism)

• Pollutants follow nutrient pathways
• Biomagnification of toxic chemicals in food chains (e.g., mercury, DDT, radionuclides)
• Level of toxicity
• Degree & duration of exposure (lethal compounds; debilitating compounds)
• Threshold and non-threshold toxicants
• Toxicants that circulate through ecosystems (e.g., metals, PCBs, dioxins, pesticides)
• Pathogens, mutagens, carcinogens, teratogens

 

Gaseous	Denitrifying Bacteria	Hormone Disrupters
Sedimentary	Nitrogen Fixing Bacteria	Toxicity
Nitrates	Nitrogen oxides	Radionuclides
Nitrites	Acid Deposition	Sulfur dioxides
Amino Acids	Carbon Fixation	Pesticides
Ammonia	Methyl Mercury	Sulfates
Phosphates	PCBs	Dioxins