Biomass (ecology)

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Apart from bacteria, the total global live biomass has been estimated as 560 billion tonnes C,[1] most of which is found in forests.[2]
Shallow aquatic environments, such as wetlands, estuaries and coral reefs, can be as productive as forests, generating similar amounts of new biomass each year on a given area.[3]

Biomass, in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals.[4] The mass can be expressed as the average mass per unit area, or as the total mass in the community.

How biomass is measured depends on why it is being measured. Sometimes, the biomass is regarded as the natural mass of organisms in situ, just as they are. For example, in a salmon fishery, the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water. In other contexts, biomass can be measured in terms of the dried organic mass, so perhaps only 30% of the actual weight might count, the rest being water. For other purposes, only biological tissues count, and teeth, bones and shells are excluded.

In stricter scientific applications, biomass is measured as the mass of organically bound carbon (C) that is present. Apart from bacteria, the total live biomass on earth is about 560 billion tonnes C,[1] and the total annual primary production of biomass is just over 100 billion tonnes C/yr.[5] However, the total live biomass of bacteria may exceed that of plants and animals.[6][7]

Ecological pyramids[edit]

Main article: Ecological pyramid
An ecological pyramid.

An ecological pyramid is a graphical representation that shows, for a given ecosystem, the relationship between biomass or biological productivity and trophic levels.

  • A biomass pyramid shows the amount of biomass at each trophic level.
  • A productivity pyramid shows the production or turn-over in biomass at each trophic level.

An ecological pyramid provides a snapshot in time of an ecological community.

The bottom of the pyramid represents the primary producers (autotrophs). The primary producers take energy from the environment in the form of sunlight or inorganic chemicals and use it to create energy-rich molecules such as carbohydrates. This mechanism is called primary production. The pyramid then proceeds through the various trophic levels to the apex predators at the top.

When energy is transferred from one trophic level to the next, typically only ten percent is used to build new biomass. The remaining ninety percent goes to metabolic processes or is dissipated as heat. This energy loss means that productivity pyramids are never inverted, and generally limits food chains to about six levels. However, in oceans, biomass pyramids can be wholly or partially inverted, with more biomass at higher levels.

Terrestrial biomass[edit]

Terrestrial biomass generally decreases markedly at each higher trophic level (plants, herbivores, carnivores). Examples of terrestrial producers are grasses, trees and shrubs. These have a much higher biomass than the animals that consume them, such as deer, zebras and insects. The level with the least biomass are the highest predators in the food chain, such as foxes and eagles.

In a temperate grassland, grasses and other plants are the primary producers at the bottom of the pyramid. Then come the primary consumers, such as grasshoppers, voles and bison, followed by the secondary consumers, shrews, hawks and small cats. Finally the tertiary consumers, large cats and wolves. The biomass pyramid decreases markedly at each higher level.

Ocean biomass[edit]


The marine food chain

Bluefin-big.jpg  predatory fish

Herring2.jpg  filter feeders

predatory zooplankton

zooplankton

phytoplankton

 

Ocean biomass, in a reversal of terrestrial biomass, can increase at higher trophic levels. In the ocean, the food chain typically starts with phytoplankton, and follows the course:

Phytoplankton → zooplankton → predatory zooplankton → filter feeders → predatory fish

Phytoplankton are the main primary producers at the bottom of the marine food chain. Phytoplankton use photosynthesis to convert inorganic carbon into protoplasm. They are then consumed by microscopic animals called zooplankton.

Zooplankton comprise the second level in the food chain, and includes small crustaceans, such as copepods and krill, and the larva of fish, squid, lobsters and crabs.

In turn, small zooplankton are consumed by both larger predatory zooplankters, such as krill, and by forage fish, which are small schooling filter feeding fish. This makes up the third level in the food chain.

An ocean food web showing a network of food chains

The fourth trophic level consists of predatory fish, marine mammals and seabirds that consume forage fish. Examples are swordfish, seals and gannets.

Apex predators, such as orcas, which can consume seals, and shortfin mako sharks, which can consume swordfish, make up the fifth trophic level. Baleen whales can consume zooplankton and krill directly, leading to a food chain with only three or four trophic levels.

Marine environments can have inverted biomass pyramids. In particular, the biomass of consumers (copepods, krill, shrimp, forage fish) is larger than the biomass of primary producers. This happens because the ocean's primary producers are tiny phytoplankton that grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, terrestrial primary producers grow and reproduce slowly.

There is an exception with cyanobacteria. Marine cyanobacteria are the smallest known photosynthetic organisms; the smallest of all, Prochlorococcus, is just 0.5 to 0.8 micrometres across.[8] Prochlorococcus is possibly the most plentiful species on Earth: a single millilitre of surface seawater may contain 100,000 cells or more. Worldwide, there are estimated to be several octillion (~1027) individuals.[9] Prochlorococcus is ubiquitous between 40°N and 40°S and dominates in the oligotrophic (nutrient poor) regions of the oceans.[10] The bacterium accounts for an estimated 20% of the oxygen in the Earth's atmosphere, and forms part of the base of the ocean food chain.[11]

Bacterial biomass[edit]

There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. In all, it has been estimated that there are about five million trillion trillion, or 5 × 1030 (5 nonillion) bacteria on Earth with a total biomass equaling that of plants.[12] Some researchers believe that the total biomass of bacteria exceeds that of all plants and animals.[6][7]

Global biomass[edit]

Estimates for the global biomass of species and higher level groups are not always consistent across the literature. Apart from bacteria, the total global biomass has been estimated at about 560 billion tonnes C.[1] Most of this biomass is found on land, with only 5 to 10 billion tonnes C found in the oceans.[1] On land, there is about 1,000 times more plant biomass (phytomass) than animal biomass (zoomass). About 18% of this plant biomass is eaten by the land animals.[13] However, in the ocean, the animal biomass is nearly 30 times larger than the plant biomass.[14] Most ocean plant biomass is eaten by the ocean animals.[13]

name number of species date of estimate individual count mean living weight of individual percent biomass (dried) total number of carbon atoms global dry biomass in million tonnes global wet (fresh) biomass in million tonnes
Terrestrial
1
2012[15]
7.0 billion
50 kg
(incl children)
30%
3.5 x 1036 [16]
105
350
2005
4.63 billion
62 kg
(excl children)[17]
287[17]
1
1.3 billion[18]
400 kg
30%
156
520
2
2002
1.75 billion[19]
60 kg
30%
31.5
105
1
24 billion
2 kg
30%
14.4
48
12,649[20]
107 - 108 billion [21]
3 x 10−6kg
(0.003 grams)
30%
10–100
30-300
>2,800
1996
445[22]
Marine
1
Pre-whaling
340,000
40%[24]
4.7 x 1035[25]
36
2001
4700
40%[24]
0.5
>10,000
2009
800-2,000[26]
1
1924–2004
7.8 x 1014
0.486 g
379[27]
13,000
10-6 - 10−9 kg
1x1037 [28]
?
2003
1,000[29]
Global
Prokaryotes
(bacteria)
?
1998
4–6 x 1030 cells[12]
1.76-2.76 x 1040 [12]
350,000-550,000[12]

Humans comprise about 100 million tonnes of the Earth's dry biomass,[30] domesticated animals about 700 million tonnes, and crops about 2 billion tonnes.[citation needed] The most successful animal species, in terms of biomass, may well be Antarctic krill, Euphausia superba, with a fresh biomass approaching 500 million tonnes,[27][31][32] although domestic cattle may also reach these immense figures.[citation needed] However, as a group, the small aquatic crustaceans called copepods may form the largest animal biomass on earth.[33] A 2009 paper in Science estimates, for the first time, the total world fish biomass as somewhere between 0.8 and 2.0 billion tonnes.[34][35] It has been estimated that about 1% of the global biomass is due to phytoplankton,[36] and a staggering 25% is due to fungi.[37][38]

Global rate of production[edit]

Globally, terrestrial and oceanic habitats produce a similar amount of new biomass each year (56.4 billion tonnes C terrestrial and 48.5 billion tonnes C oceanic).

Net primary production is the rate at which new biomass is generated, mainly due to photosynthesis. Global primary production can be estimated from satellite observations. Satellites scan the normalised difference vegetation index (NDVI) over terrestrial habitats, and scan sea-surface chlorophyll levels over oceans. This results in 56.4 billion tonnes C/yr (53.8%), for terrestrial primary production, and 48.5 billion tonnes C/yr for oceanic primary production.[5] Thus, the total photoautotrophic primary production for the Earth is about 104.9 billion tonnes C/yr. This translates to about 426 gC/m²/yr for land production (excluding areas with permanent ice cover), and 140 gC/m²/yr for the oceans.

However, there is a much more significant difference in standing stocks—while accounting for almost half of total annual production, oceanic autotrophs account for only about 0.2% of the total biomass. Autotrophs may have the highest global proportion of biomass, but they are closely rivaled or surpassed by microbes.[39][40]

Terrestrial freshwater ecosystems generate about 1.5% of the global net primary production.[41]

Some global producers of biomass in order of productivity rates are

Producer Biomass productivity
(gC/m²/yr)
Ref Total area
(million km²)
Ref Total production
(billion tonnes C/yr)
Swamps and Marshes 2,500 [3]
Tropical rainforests 2,000 [42] 8 16
Coral reefs 2,000 [3] 0.28 [43] 0.56
Algal beds 2,000 [3]
River estuaries 1,800 [3]
Temperate forests 1,250 [3] 19 24
Cultivated lands 650 [3][44] 17 11
Tundras 140 [3][44]
Open ocean 125 [3][44] 311 39
Deserts 3 [44] 50 0.15

See also[edit]

References[edit]

  1. ^ a b c d Groombridge B, Jenkins MD (2000) Global biodiversity: Earth’s living resources in the 21st century Page 11. World Conservation Monitoring Centre, World Conservation Press, Cambridge
  2. ^ "Biomass". 
  3. ^ a b c d e f g h i Ricklefs, Robert E.; Miller, Gary Leon (2,000). Ecology (4th ed.). Macmillan. p. 192. ISBN 978-0-7167-2829-0. 
  4. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "biomass".
  5. ^ a b Field, C.B.; Behrenfeld, M.J., Randerson, J.T. and Falkowski, P. (1998). "Primary production of the Biosphere: Integrating Terrestrial and Oceanic Components". Science 281 (5374): 237–240. doi:10.1126/science.281.5374.237. PMID 9657713. 
  6. ^ a b C.Michael Hogan. 2010. Bacteria. Encyclopedia of Earth. eds. Sidney Draggan and C.J.Cleveland, National Council for Science and the Environment, Washington DC
  7. ^ a b Gould, Stephen Jay (1996) "Planet of the Bacteria" Washington Post Horizon, 119 (344): H1. Adapted from Full House: The Spread of Excellence From Plato to Darwin. New York: Harmony Books. ISBN 0-517-70394-7{{inconsistent citations}} 
  8. ^ Kettler, Gregory C.; Martiny, Adam C.; Huang, Katherine; Zucker, Jeremy; Coleman, Maureen L.; Rodrigue, Sebastien; Chen, Feng; Lapidus, Alla et al. (December 2007). "Patterns and Implications of Gene Gain and Loss in the Evolution of Prochlorococcus". PLoS Genetics 3 (12): e231. doi:10.1371/journal.pgen.0030231. PMC 2151091. PMID 18159947. 
  9. ^ "DGF". NASA. 
  10. ^ F. Partensky, W. R. Hess & D. Vaulot (1999). "Prochlorococcus, a marine photosynthetic prokaryote of global significance". Microbiology and Molecular Biology Reviews 63 (1): 106–127. PMC 98958. PMID 10066832. 
  11. ^ The Most Important Microbe You've Never Heard Of
  12. ^ a b c d e Whitman WB, Coleman DC, Wiebe WJ (1998). "Prokaryotes: the unseen majority". Proceedings of the National Academy of Sciences of the United States of America 95 (12): 6578–83. doi:10.1073/pnas.95.12.6578. PMC 33863. PMID 9618454. 
  13. ^ a b Hartley, Sue (2010) The 300 Million Years War: Plant Biomass v Herbivores Royal Institution Christmas Lecture.
  14. ^ Darlington, P (1966) http://encyclopedia2.thefreedictionary.com/Terrestrial+Fauna "Biogeografia". Published in The Great Soviet Encyclopedia, 3rd Edition (1970-1979).
  15. ^ US world population clock
  16. ^ Freitas, Robert A. Jr.Nanomedicine 3.1 Human Body Chemical Composition Foresight Institute, 1998
  17. ^ a b Walpole, S.C.; Prieto-Merino, D.; Edwards, P.; Cleland, J.; Stevens, G.; Roberts, I. (2012). "The weight of nations: an estimation of adult human biomass". BMC Public Health 12: 439. doi:10.1186/1471-2458-12-439. PMC 3408371. PMID 22709383. 
  18. ^ Cattle Today. "Breeds of Cattle at CATTLE TODAY". Cattle-today.com. Retrieved 2013-10-15. 
  19. ^ World's Rangelands Deteriorating Under Mounting Pressure Earth Policy Institute 2002
  20. ^ http://osuc.biosci.ohio-state.edu/hymenoptera/tsa.sppcount?the_taxon=Formicidae
  21. ^ Embery, Joan and Lucaire, Ed (1983) Collection of Amazing Animal Facts.
  22. ^ Sum of [(biomass m^-2)*(area m^2)] from table 3 in Sanderson, M.G. 1996 Biomass of termites and their emissions of methane and carbon dioxide: A global database Global Biochemical Cycles, Vol 10:4 543-557
  23. ^ Pershing, A.J.; Christensen, L.B.; Record, N.R.; Sherwood, G.D.; Stetson, P.B.; Humphries, Stuart (2010). "The Impact of Whaling on the Ocean Carbon Cycle: Why Bigger Was Better". In Humphries, Stuart. PLoS ONE 5 (8): e12444. doi:10.1371/journal.pone.0012444. PMC 2928761. PMID 20865156.  (Table 1)
  24. ^ a b c Jelmert, A.; Oppen-Berntsen, D.O. (1996). "Whaling and Deep-Sea Biodiversity". Conservation Biology 10 (2): 653–654. doi:10.1046/j.1523-1739.1996.10020653.x. 
  25. ^ Assuming half the dry biomass is protein and half fat, with respective carbon contents of 54% and 77%,[24] hence 35.7 x (0.2 x 0.54 + 0.2 x 0.77) = 9.35 Mt carbon, or 9.35e12 / 12.011 * 6.0221415e23 atoms
  26. ^ Wilson RW, Millero FJ, Taylor JR, Walsh PJ, Christensen V, Jennings S and Grosell M (2009) "Contribution of Fish to the Marine Inorganic Carbon Cycle" Science, 323 (5912) 359-362. (This article provides a first estimate of global fish biomass)
  27. ^ a b Atkinson, A.; Siegel, V.; Pakhomov, E.A.; Jessopp, M.J.; Loeb, V. (2009). "A re-appraisal of the total biomass and annual production of Antarctic krill". Deep-Sea Research I 56 (5): 727–740. doi:10.1016/j.dsr.2008.12.007. 
  28. ^ Buitenhuis, E. T., C. Le Quéré, O. Aumont, G. Beaugrand, A. Bunker, A. Hirst, T. Ikeda, T. O'Brien, S. Piontkovski, D. Straile (2006) Biogeochemical fluxes through mesozooplankton. Global Biogeochemical Cycles 20, GB2003, doi:10.1029/2005GB002511
  29. ^ Garcia-Pichel, F; Belnap, J; Neuer, S; Schanz, F (2003). "Estimates of global cyanobacterial biomass and its distribution" (PDF). Algological Studies 109: 213–217. doi:10.1127/1864-1318/2003/0109-0213. 
  30. ^ The world human population was 6.6 billion in January 2008. At an average weight of 100 pounds (30 lbs of biomass), that equals 100 million tonnes.[clarification needed]
  31. ^ a b Nicol, S., Endo, Y. (1997). Fisheries Technical Paper 367: Krill Fisheries of the World. FAO. 
  32. ^ Ross, R. M. and Quetin, L. B. (1988). Euphausia superba: a critical review of annual production. Comp. Biochem. Physiol. 90B, 499-505.
  33. ^ a b Biology of Copepods at Carl von Ossietzky University of Oldenburg
  34. ^ Wilson, RW, Millero, FJ, Taylor, JR, Walsh, PJ, Christensen, V, Jennings, S, Grosell, M (2009). "Contribution of Fish to the Marine Inorganic Carbon Cycle". Science 323 (5912): 359–362. doi:10.1126/science.1157972. PMID 19150840. 
  35. ^ Researcher gives first-ever estimate of worldwide fish biomass and impact on climate change PhysOrg.com, 15 January 2009.
  36. ^ Bidle1 KD and Falkowski PG (2004) "Cell death in planktonic, photosynthetic microorganisms" Nature Reviews: Microbiology, 2: 643–655. doi:10.1038/nrmicro956
  37. ^ Miller JD (1992) "Fungi as contaminants in indoor air" Atmospheric Environment 26 (12): 2163–2172.
  38. ^ Sorenson WG (1999) "Fungal spores: Hazardous to health?" Environ Health Perspect, 107 (Suppl 3): 469–472.
  39. ^ Whitman, W. B.; Coleman, D. C.; Wieb, W. J. (1998). "Prokaryotes: The unseen majority". Proc. Natl. Acad. Sci. USA 95 (12): 6578–6583. doi:10.1073/pnas.95.12.6578. PMC 33863. PMID 9618454. 
  40. ^ Groombridge, B.; Jenkins, M. (2002). World Atlas of Biodiversity: Earth's Living Resources in the 21st Century. World Conservation Monitoring Centre, United Nations Environment Programme. ISBN 0-520-23668-8. PMC 3408371. 
  41. ^ Alexander, David E. (1 May 1999). Encyclopedia of Environmental Science. Springer. ISBN 0-412-74050-8. 
  42. ^ Ricklefs, Robert E.; Miller, Gary Leon (2000). Ecology (4th ed.). Macmillan. p. 197. ISBN 978-0-7167-2829-0. 
  43. ^ Spalding, Mark, Corinna Ravilious, and Edmund Green. 2001. World Atlas of Coral Reefs. Berkeley, CA: University of California Press and UNEP/WCMC.
  44. ^ a b c d Park, Chris C. (2001). The environment: principles and applications (2nd ed.). Routledge. p. 564. ISBN 978-0-415-21770-5. 

Further reading[edit]

External links[edit]