In ecology, the term productivity refers to the rate of generation of biomass in an ecosystem, usually expressed in units of mass per volume (unit surface) per unit of time, such as grams per square metre per day (g m−2 d−1). The unit of mass can relate to dry matter or to the mass of generated carbon. The productivity of autotrophs, such as plants, is called primary productivity, while the productivity of heterotrophs, such as animals, is called secondary productivity.[1]

Primary production

Main article: Primary production

Primary production is the synthesis of organic material from inorganic molecules. Primary production in most ecosystems is dominated by the process of photosynthesis, In which organisms synthesize organic molecules from sunlight, H2O, and CO2. Primary production is sometimes broken down into Net Primary Production (NPP) and Gross Primary Production (GPP). Gross primary production measures all carbon assimilated into organic molecules by primary producers. Net primary production measures the organic molecules by primary producers. Net primary production also measures the amount of carbon assimilated into organic molecules by primary producers, but does not include organic molecules that are then broken down again by these organism for biological processes such as cellular respiration.

Primary Producers

Photoautotrophs

Organisms that rely on light energy to fix carbon, and thus participate in primary production, are referred to as photoautotrophs.

Photoautotrophs exists across the tree of life. Many bacterial taxa are known to be photoautotrophic such as cyanobacteria and some proteobacteria.[2] Eukaryotic organisms gained the ability to participate in photosynthesis through the development of plastids derived from endosymbiotic relationships.[3] Archaeplastida, which includes red algae, green algae, and plants, have evolved chloroplasts originating from an ancient endosymbiotic relationship with an α-Proteobacteria.[4] The rest of the eukaryotic photoautotrophic organisms are within the SAR clade (Comprising Stramenopila, Alveolata, and Rhizaria). Organisms in the SAR clade that developed plastids did so through a secondary or a tertiary endosymbiotic relationships with green algae and/or red algae.[5] The SAR clade includes many aquatic and marine primary producers such as Kelp, Diatoms, and Dinoflagellates.[5]

Lithoautotrophs

The other process of primary production is lithoautotrophy. Lithoautotrophs use reduced chemical compounds such as hydrogen gas, hydrogen sulfide, methane, or ferrous ion to fix carbon and participate in primary production. Lithoautotrophic organisms are prokaryotic and are represented by members of both the bacterial and archaeal domains.[6] Lithoautotrophy is the only form of primary production possible in ecosystems without light such as ground-water ecosystems,[7] hydrothermal vent ecosystems,[8] soil ecosystems,[9] and cave ecosystems.[10]

Secondary production

Secondary production is the generation of biomass of heterotrophic (consumer) organisms in a system. This is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food. Secondary production is sometimes defined to only include consumption of primary producers by herbivorous consumers[11] (with tertiary production referring to carnivorous consumers),[12] but is more commonly defined to include all biomass generation by heterotrophs.[1]

Organisms responsible for secondary production include animals, protists, fungi and many bacteria.[citation needed]

Secondary production can be estimated through a number of different methods including increment summation, removal summation, the instantaneous growth method and the Allen curve method.[13] The choice between these methods will depend on the assumptions of each and the ecosystem under study. For instance, whether cohorts should be distinguished, whether linear mortality can be assumed and whether population growth is exponential.[citation needed]

See also

References

  1. ^ a b Allaby, Michael, ed. (2006) [1994]. A Dictionary of Ecology (Third ed.). Oxford, UK: Oxford University Press. ISBN 978-0-19-860905-6. Retrieved 2009-12-03.
  2. ^ Tang, Kuo-Hsiang; Tang, Yinjie J.; Blankenship, Robert Eugene (2011). "Carbon Metabolic Pathways in Phototrophic Bacteria and Their Broader Evolutionary Implications". Frontiers in Microbiology. 2: 165. doi:10.3389/fmicb.2011.00165. PMC 3149686. PMID 21866228.
  3. ^ Margulis, L. (1968-09-06). "Evolutionary criteria in thallophytes: a radical alternative". Science. 161 (3845): 1020–1022. Bibcode:1968Sci...161.1020M. doi:10.1126/science.161.3845.1020. PMID 17812802. S2CID 21929905.
  4. ^ Ford Doolittle, W (1998-12-01). "You are what you eat: a gene transfer ratchet could account for bacterial genes in eukaryotic nuclear genomes". Trends in Genetics. 14 (8): 307–311. doi:10.1016/S0168-9525(98)01494-2. PMID 9724962.
  5. ^ a b Grattepanche, Jean-David; Walker, Laura M.; Ott, Brittany M.; Paim Pinto, Daniela L.; Delwiche, Charles F.; Lane, Christopher E.; Katz, Laura A. (2018). "Microbial Diversity in the Eukaryotic SAR Clade: Illuminating the Darkness Between Morphology and Molecular Data". BioEssays. 40 (4): e1700198. doi:10.1002/bies.201700198. PMID 29512175. S2CID 3731086.
  6. ^ Lazar, Cassandre Sara; Stoll, Wenke; Lehmann, Robert; Herrmann, Martina; Schwab, Valérie F.; Akob, Denise M.; Nawaz, Ali; Wubet, Tesfaye; Buscot, François (2017-06-13). "Archaeal Diversity and CO2 Fixers in Carbonate-/Siliciclastic-Rock Groundwater Ecosystems". Archaea. 2017: 1–13. doi:10.1155/2017/2136287. PMC 5485487. PMID 28694737.
  7. ^ Griebler, C.; Lueders, T. (2009). "Microbial biodiversity in groundwater ecosystems". Freshwater Biology. 54 (4): 649–677. doi:10.1111/j.1365-2427.2008.02013.x.
  8. ^ Sievert, Stefan; Vetriani, Costantino (2012-03-01). "Chemoautotrophy at Deep-Sea Vents: Past, Present, and Future". Oceanography. 25 (1): 218–233. doi:10.5670/oceanog.2012.21.
  9. ^ Drake, Henrik; Ivarsson, Magnus (2018-01-01). "The role of anaerobic fungi in fundamental biogeochemical cycles in the deep biosphere". Fungal Biology Reviews. 32 (1): 20–25. doi:10.1016/j.fbr.2017.10.001.
  10. ^ Galassi, Diana M. P.; Fiasca, Barbara; Di Lorenzo, Tiziana; Montanari, Alessandro; Porfirio, Silvano; Fattorini, Simone (2017-03-01). "Groundwater biodiversity in a chemoautotrophic cave ecosystem: how geochemistry regulates microcrustacean community structure". Aquatic Ecology. 51 (1): 75–90. doi:10.1007/s10452-016-9599-7. S2CID 41641625.
  11. ^ "Definition of term: "Secondary production"". The Glossary Table. FishBase. Retrieved 2009-12-03.
  12. ^ "Definition of term: "Tertiary production"". The Glossary Table. FishBase. Retrieved 2009-12-03.
  13. ^ Allen, K.R. (1951). "The Horokiwi Stream: A study of a trout population". New Zealand Marine Department Fisheries Bulletin. 10: 1–238.