Biogeochemical Cycles – Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on biogeochemical cycles.

Biogeochemical cycles

Movement of elements (C, N, P, S, metals) through living organisms and the physical environment, with microbes catalyzing many transformations.

Microbes as producers and consumers

Microbes can be primary producers (photosynthesis/chemosynthesis) and also decomposers/respirers, linking production and consumption in cycles.

Redox chemistry

Electron transfer reactions driving energy flow; microbes catalyze many redox transformations in biogeochemical cycles.

Autotrophy

Organisms that fix CO2 into organic matter, forming the basis of primary production.

Heterotrophy

Organisms that obtain energy by consuming pre-formed organic carbon.

Solar energy to chemical energy

Conversion of light energy into chemical energy via photosynthesis or chemosynthesis.

Mineralization (ammonification)

Breakdown of organic nitrogen to ammonium (NH4+), releasing inorganic N.

Immobilization

Uptake of NH4+/NO3− by microbial biomass, reducing inorganic N availability to plants.

Nitrification

Oxidation of NH4+ to NO2− and then NO3−, performed by ammonia-oxidizing and nitrite-oxidizing microorganisms.

Denitrification

Reduction of nitrate to N2 (via NO2−, NO, and N2O), removing fixed N from ecosystems under anaerobic conditions.

Nitrogen fixation

Conversion of N2 gas to NH3 by nitrogenase; energy-intensive and carried out by free-living or symbiotic microbes.

Anammox

Anaerobic ammonium oxidation: NH4+ + NO2− → N2, carried out by Planctomycetes.

Nitrogen assimilation

Incorporation of inorganic nitrogen into organic molecules by producers.

Nitrate (NO3−)

Soluble inorganic nitrogen form produced by nitrification; taken up by plants.

Ammonium (NH4+)

Inorganic nitrogen form produced by mineralization; substrate for nitrification; taken up by plants.

Phosphorus cycle basics

Phosphorus moves through weathering, uptake, and burial with no significant atmospheric pool.

Mycorrhizal fungi

Fungi that form symbioses with plant roots, extending nutrient uptake (notably phosphorus) and exchanging carbon with plants.

Siderophores

Microbial iron-chelating compounds that solubilize ferric iron and aid uptake in iron-limited environments.

Phosphate mining

Extraction of phosphate rocks to supply phosphorus fertilizer.

Sulfate reduction

Anaerobic reduction of sulfate (SO4^2−) to sulfide (H2S) by SRB, common in sediments.

Sulfur oxidation

Oxidation of reduced sulfur species (e.g., H2S) to sulfate, providing energy for CO2 fixation.

Anoxygenic photosynthesis

Photosynthesis using H2S (or other donors) instead of H2O, at oxic–anoxic interfaces.

Methanogenesis

Methane production by Archaea (methanogens) via acetoclastic or hydrogenotrophic pathways.

Methanotrophy

Microbes that consume methane (CH4), offsetting methane production.

Methane cycle

Processes producing and consuming methane, including wetlands, digestion, and aerobic methane oxidation.

Biological pump

Phytoplankton fixation of C followed by microbial decomposition that exports carbon to sediments.

Global carbon budget sinks

Oceans and terrestrial ecosystems that remove CO2 from the atmosphere; microbial processes influence NEP.

Net ecosystem production (NEP)

Net CO2 uptake of an ecosystem: gross primary production minus ecosystem respiration.

Haber–Bosch process

Industrial fixation of N2 to ammonia; a major human source of reactive nitrogen via fertilizers.

Eutrophication

Nutrient enrichment (N or P) causing algal blooms and oxygen depletion in water bodies.

Acid mine drainage

Acidification and metal release from sulfide mineral oxidation, often linked to mining activities.

Microbial weathering

Microbial respiration produces CO2, forming carbonic acid that accelerates mineral weathering and nutrient release.

Trace metals and microbes (Hg, As)

Toxic metals detoxified by microbes via reduction, methylation, efflux; some cycles involve detoxification and accumulation.

Selenium cycling

Redox transformations of Se between SeO4^2−, Se^0, and Se^2−; microbes mediate transformations with environmental significance.

Arsenic cycling

Interconversions between arsenate (As^5+) and arsenite (As^3+); microbes use these forms as electron acceptors/donors and detoxify accordingly.

Mauna Loa CO2 measurements (Keeling curve)

Long-term record of atmospheric CO2 showing seasonal oscillations and a rising baseline due to fossil fuel use and other sources.