Biogeochemical Cycles

Biogeochemical Cycle

Continuous recycling of elements between living organisms and the environment through biological and chemical processes.

Oxidation-Reduction Potential

Measure of the tendency of molecules to donate or accept electrons, expressed in millivolts relative to the standard hydrogen electrode.

Mineralization

Conversion of organic matter into inorganic compounds through microbial decomposition.

Immobilization

Conversion of inorganic nutrients into microbial biomass, temporarily removing them from biogeochemical cycling.

Carbon Cycle

Biogeochemical cycle involving the movement and transformation of carbon between living organisms and the environment.

Reduced Inorganic Carbon

Inorganic carbon compound in a reduced state, such as methane (CH₄).

Oxidized Inorganic Carbon

Inorganic carbon compound in an oxidized state, such as carbon dioxide (CO₂) or carbon monoxide (CO).

Carbon Fixation

Process by which inorganic carbon is converted into organic compounds by autotrophic organisms.

Methanogenesis

Production of methane by methanogenic archaea under anaerobic conditions.

Methanogen

Archaeon that produces methane during anaerobic metabolism.

Methane Oxidation

Conversion of methane into carbon dioxide by methanotrophic microorganisms.

Methanotroph

Microorganism that uses methane as its carbon and energy source.

Oxygenic Photosynthesis

Photosynthetic process that fixes carbon dioxide using water as the electron donor while releasing oxygen.

Respiration

Metabolic process that oxidizes organic compounds and releases carbon dioxide while generating energy.

Fermentation

Anaerobic metabolic process that partially oxidizes organic compounds without using an electron transport chain.

Humus

Stable organic matter in soil that resists decomposition for long periods.

Lignin

Complex plant polymer degraded primarily by fungi and a few bacteria.

Nitrogen Cycle

Biogeochemical cycle involving the transformation of nitrogen between different chemical forms.

Nitrogen Fixation

Reduction of atmospheric nitrogen gas (N₂) into ammonia (NH₃).

Ammonification

Conversion of organic nitrogen into ammonium (NH₄⁺) during decomposition.

Nitrification

Oxidation of ammonium to nitrite and then nitrate.

Comammox Bacterium

Bacterium capable of complete oxidation of ammonia to nitrate.

Assimilation

Incorporation of inorganic nitrogen into microbial or plant biomass.

Denitrification

Reduction of nitrate to gaseous nitrogen during anaerobic respiration.

Anammox

Anaerobic oxidation of ammonium using nitrite as the terminal electron acceptor to produce nitrogen gas.

Phosphorus Cycle

Biogeochemical cycle involving the movement of phosphorus, primarily as phosphate, through the environment and living organisms.

Sulfur Cycle

Biogeochemical cycle involving the movement and transformation of sulfur compounds.

Iron Cycle

Biogeochemical cycle involving oxidation and reduction of iron compounds.

Manganese Cycle

Biogeochemical cycle involving oxidation and reduction of manganese compounds.

Mercury Cycle

Biogeochemical cycle involving the transformation and movement of mercury in the environment.

Global Climate Change

Long-term alteration of Earth's climate associated with changes in greenhouse gas concentrations.

Greenhouse Gas

Atmospheric gas that traps heat and contributes to the greenhouse effect.

Eutrophication

Nutrient enrichment of aquatic ecosystems that promotes excessive algal growth.

Bioremediation

Use of microorganisms to remove or detoxify environmental contaminants.

Biofragmentation

Initial stage of biodegradation in which extracellular enzymes break large organic molecules into smaller compounds.

Bioassimilation

Stage of biodegradation in which microorganisms take up and incorporate smaller organic molecules into biomass.

Oil Bioremediation

Microbial degradation of petroleum hydrocarbons in contaminated environments.

Plastic Bioremediation

Microbial degradation of synthetic plastic polymers.

Crude Oil

Complex mixture of naturally occurring hydrocarbons.

Hydrocarbon

Organic compound composed entirely of carbon and hydrogen atoms.

Amorphous Region

Less ordered region of a plastic polymer that is more susceptible to microbial degradation.

Crystalline Region

Highly ordered region of a plastic polymer that is more resistant to microbial degradation.