Nutrient CyclesWater, Carbon, Phosphorus,

Nitrogen and Sulfur

Water Cycle Collects, purifies and distributes earth’s supply of water

Driven by evaporation (from oceans, lakes, rivers and soil), precipitation (rain, snow, sleet, dew), and transpiration (from surfaces of plants and soil)

Reservoirs (sinks): groundwater/aquifers, ocean, ice and snow (glaciers), lakes and reservoirs

Humans influence cycle by:• Increased surface runoff• Taking too much groundwater out• Water pollution

Carbon Cylce Building block for organic compounds necessary for life

Key component in atmosphere—greenhouse gases and temperature regulation

Driven by photosynthesis and cell respiration

Reservoirs (sinks): atmosphere, plants, animals, fossil fuels, dissolved in ocean, limestone and ocean sediments

Human Impacts (releasing CO2 into atmosphere):• Driving cars• Deforestation• Burning fossil fuels• Burning forests

Nitrogen Cycle Component of proteins, vitamins and nucleic acids

Cannot be absorbed directly by plants and animals (N2)—rely on nitrogen fixing bacteria

Reservoirs (sinks): atmosphere, ocean sediments, soil (ammonia and nitrates), plants and animals

Human Impacts:• Runoff from fertilizers and decomposition (water, soil)• Burning fuel and fertilizers (atmosphere)• Remove from soils with agriculture and irrigation

Phosphorus Cycle Circulates through water and soil, does not

include the atmosphere

Very slow cycle. Component of nucleic acids and ATP/ADP, bones and teeth

Reservoirs (sinks): phosphate salts in rock and ocean sediments; plants and animals

Human Impacts: • Runoff from mining waste, sewage and fertilizer• Erosion of rock

Sulfur Cycle Used to produce proteins

Stored in underground rocks and minerals, and sulfate salts in ocean sediments

Hydrogen sulfide gas released to atmosphere through volcanoes and decomposers

Reservoirs (sinks): atmosphere, plants, animals, rock and soils, ocean sediments

Human Impacts: • release sulfur dioxide through burning of fossil fuels and refining coal• Mining • Acid rain from fossil fuel burning