Biogeochemical Cycles

Ecosystem defined: a community of organisms and it’s corresponding abiotic environment through which matter cycles and energy flows Wide variation in ecosystems Boarders can be well defined or vague Can be natural or artificial, managed or wild Wide range in scale Common to all ecosystems: energy flow and cycling of matter

Reservoir chemicals for long periods of time in one place and are generally abiotic Example: coal deposits

Exchange Pools chemicals are held for only short periods of time and are generally biotic Example: plants and animals (which temporarily use carbon in their systems and then release back into the air)

Biogeochemical Cycle circuit or pathway by which a chemical element or molecule moves through both biotic ("bio-") and abiotic ("geo-") compartments of an ecosystem. In effect, the element is recycled

BIO Biology. Life. Living things. These cycles all play a role in the lives of living things. The cycles might limit the organisms of Earth or they might happen along side, changing the environment

GEO Earth. Rocks. Land. This refers to the non-living processes at work. Oxygen cycles through many systems. It's in you and plants for the 'bio' part of the cycle. Oxygen might also wind up in rocks. The 'geo' part of its cycle.

Chemical Molecules. Reactions. Atoms. All cycles include these small pathways. Complete molecules are not always passed from one point to the next. Sometimes chemical reactions take place that changes the molecules and locations of the atoms. Think about oxidation as an example of the 'chemical' part of these pathways.

What are the main cycles? In a gas cycle elements move through the atmosphere. Main reservoirs are the atmosphere and the ocean. In a sedimentary cycle elements move from land to water to sediment. Main reservoirs are the soil and sedimentary rocks.

What are the Biogeochemical Cycles of interest to Ecology? Carbon Cycle (gas) Nitrogen Cycle (gas) Oxygen Cycle (gas) Phosphorous Cycle (sedimentary) Sulfur Cycle (sedimentary) Hydrogen Cycle (gas) Water Cycle Mercury Cycle (new one) human caused cycle of atrazine (new one)

What does it need? It always involves equilibrium states: a balance in the cycling of the element between compartments. However, overall balance may involve compartments distributed on a global scale.

What sustains life on Earth?

Secrets to Survival An ecosystem survives by a combination of energy flow and matter recycling

Matter cycling in ecosystems Nutrient Cycles: Global Recycling Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.

Oxygen Cycle

THE CARBON CYCLE

What Is Carbon? An element The basis of life of earth Found in rocks, oceans, atmosphere

Carbon Cycle The same carbon atoms are used repeatedly on earth. They cycle between the earth and the atmosphere.

Plants Use Carbon Dioxide Plants pull carbon dioxide from the atmosphere and use it to make food –— photosynthesis. The carbon becomes part of the plant (stored food).

Animals Eat Plants When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies.

Plants and Animal Die When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere. Some are not decomposed fully and end up in deposits underground (oil, coal, etc.).

Carbon Slowly Returns to Atmosphere Carbon in rocks and underground deposits is released very slowly into the atmosphere. This process takes many years.

Cycle – Repeats Over and Over and Over and Over … 42% CO2 returned by plants, 46% by decomposers, animals by12%

Carbon Cycle Diagram Carbon in Atmosphere Plants use carbon to make food Animals eat plants and take in carbon Plants and animals die Decomposers break down dead things, releasing carbon to atmosphere and soil Bodies not decomposed — after many years, become part of oil or coal deposits Fossil fuels are burned; carbon is returned to atmosphere Carbon slowly released from these substances returns to atmosphere

Carbon in Oceans Additional carbon is stored in the ocean. Many animals pull carbon from water to use in shells, etc. Animals die and carbon substances are deposited at the bottom of the ocean. Oceans contain earth’s largest store of carbon.

The Carbon Cycle

Human Impact Fossil fuels release carbon stores very slowly Burning anything releases more carbon into atmosphere — especially fossil fuels Increased carbon dioxide in atmosphere increases global warming Fewer plants mean less CO2 removed from atmosphere

What We Need to Do Burn less, especially fossil fuels Promote plant life, especially trees

Nitrogen Cycle

Nitrogen Cycle

Effects of Increased Nitrogen 1. Loss of soil nutrients (calcium, potassium) Acidification of rivers and lakes (fertilizers and combustion of coal). Increases nitrogen oxides in the atmosphere (greenhouse gas—global warming). (reduce ozone—increasing UV penetration).

Effects of Increased Nitrogen 4. Aids in spreading weeds into nitrogen poor areas (+Eutrophication of lakes, ponds, streams). 5. Increasing nitrogen increases carbon fixation (linked to carbon cycle). 6. Increasing acidification increases weathering (increases rate of phosphorous cycle).

Phosphorus Cycle

Phosphorus Cycle

Diagram of Phosphorus Cycle

Sulphur Cycle

Sulphur Cycle

Sulphur Cycle

Biogeochemical Cycle = Recycling All the chemicals, nutrients, or elements — such as carbon, nitrogen, oxygen, phosphorus — used in ecosystems by living organisms operate on a closed system

Gaia Hypothosis Some have proposed that the earth’s various forms of life control or at least influence its chemical cycles and other earth-sustaining processes. The strong Gaia hypothesis: life controls the earth’s life-sustaining processes. The weak Gaia hypothesis: life influences the earth’s life-sustaining processes.

Conclusions In contrast to energy, which moves in one direction through the ecosystem, materials are continually recycled from the abiotic environment to organisms, and back to the abiotic environment. Changes in one of the biogeochemical cycles usually influences the other biogeochemical cycles.