Biomass (ecology)

{{Main|Ecological pyramid}}

File:Ecological Pyramid.svg illustrates how much energy is needed as it flows upward to support the next trophic level. Only about 10% of the energy transferred between each trophic level is converted to biomass.]]

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.

File:Terrestrial biomass.svg

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.

Changes in plant species in the terrestrial ecosystem can result in changes in the biomass of soil decomposer communities.{{Cite journal |last1=Spehn |first1=Eva M. |last2=Joshi |first2=Jasmin |last3=Schmid |first3=Bernhard |last4=Alphei |first4=Jörn |last5=Körner |first5=Christian |date=2000 |title=

Plant diversity effects on soil heterotrophic activity in experimental grassland ecosystems |url=http://link.springer.com/10.1023/A:1004891807664 |journal=Plant and Soil |volume=224 |issue=2 |pages=217–230 |doi=10.1023/A:1004891807664|s2cid=25639544 }} Biomass in C₃ and C₄ plant species can change in response to altered concentrations of CO₂.{{Cite journal |last1=He |first1=Jin-Sheng |last2=Bazzaz |first2=Fakhri A. |last3=Schmid |first3=Bernhard |date=2002 |title=Interactive Effects of Diversity, Nutrients and Elevated CO2 on Experimental Plant Communities |url=https://www.jstor.org/stable/3547655 |journal=Oikos |volume=97 |issue=3 |pages=337–348 |doi=10.1034/j.1600-0706.2002.970304.x |jstor=3547655 |bibcode=2002Oikos..97..337H |issn=0030-1299}} C₃ plant species have been observed to increase in biomass in response to increasing concentrations of CO₂ of up to 900 ppm.{{cite journal | last1=Drag | first1=David W | last2=Slattery | first2=Rebecca | last3=Siebers | first3=Matthew | last4=DeLucia | first4=Evan H | last5=Ort | first5=Donald R | last6=Bernacchi | first6=Carl J | title=Soybean photosynthetic and biomass responses to carbon dioxide concentrations ranging from pre-industrial to the distant future | journal=Journal of Experimental Botany | publisher=Oxford University Press (OUP) | volume=71 | issue=12 | date=2020-03-12 | issn=0022-0957 | doi=10.1093/jxb/eraa133 | pages=3690–3700| pmid=32170296 | pmc=7475242 }}

{{marine food chain}}

{{see also|Marine life}}

Ocean or marine 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

File:Arctic food web.svg showing a network of food chains}}]]

File:Numbers Pyramid.svgs
Compared to terrestrial biomass pyramids, aquatic pyramids are inverted at the base}}]]

File:Prochlorococcus marinus (cropped).jpg, an influential bacterium}}]]

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 zooplankton that range in size from a few micrometers in diameter in the case of protistan microzooplankton to macroscopic gelatinous and crustacean 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.

A fourth trophic level can consist 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 a 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 which are r-strategists that grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, terrestrial primary producers, such as forests, are K-strategists that grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production.

Among the phytoplankton at the base of the marine food web are members from a phylum of bacteria called cyanobacteria. Marine cyanobacteria include the smallest known photosynthetic organisms. The smallest of all, Prochlorococcus, is just 0.5 to 0.8 micrometres across.{{cite journal | vauthors = Kettler GC, Martiny AC, Huang K, Zucker J, Coleman ML, Rodrigue S, Chen F, Lapidus A, Ferriera S, Johnson J, Steglich C, Church GM, Richardson P, Chisholm SW | title = Patterns and implications of gene gain and loss in the evolution of Prochlorococcus | journal = PLOS Genetics | volume = 3 | issue = 12 | pages = e231 | date = December 2007 | pmid = 18159947 | pmc = 2151091 | doi = 10.1371/journal.pgen.0030231 | doi-access = free }} In terms of individual numbers, Prochlorococcus is possibly the most plentiful species on Earth: a single millilitre of surface seawater can contain 100,000 cells or more. Worldwide, there are estimated to be several octillion (10²⁷) individuals.{{Cite APOD |date=27 September 2006 |title=Earth from Saturn }} Prochlorococcus is ubiquitous between 40°N and 40°S and dominates in the oligotrophic (nutrient poor) regions of the oceans.{{cite journal | vauthors = Partensky F, Hess WR, Vaulot D | title = Prochlorococcus, a marine photosynthetic prokaryote of global significance | journal = Microbiology and Molecular Biology Reviews | volume = 63 | issue = 1 | pages = 106–127 | date = March 1999 | pmid = 10066832 | pmc = 98958 | doi = 10.1128/MMBR.63.1.106-127.1999 }} 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.{{cite web|url=https://www.npr.org/templates/story/story.php?storyId=91448837|title=The Most Important Microbe You've Never Heard Of|website=npr.org|access-date=3 April 2018|archive-date=19 October 2023|archive-url=https://web.archive.org/web/20231019060753/http://www.npr.org/templates/story/story.php?storyId=91448837|url-status=live}}

Bacteria and archaea are both classified as prokaryotes, and their biomass is commonly estimated together. The global biomass of prokaryotes is estimated at 30 billion tonnes C, dominated by bacteria.

The estimates for the global biomass of prokaryotes had changed significantly over recent decades, as more data became available. A much-cited study from 1998 collected data on abundances (number of cells) of bacteria and archaea in different natural environments, and estimated their total biomass at 350 to 550 billion tonnes C. This vast amount is similar to the biomass of carbon in all plants. The vast majority of bacteria and archaea were estimated to be in sediments deep below the seafloor or in the deep terrestrial biosphere (in deep continental aquifers). However, updated measurements reported in a 2012 study reduced the calculated prokaryotic biomass in deep subseafloor sediments from the original ≈300 billion tonnes C to ≈4 billion tonnes C (range 1.5–22 billion tonnes). This update originates from much lower estimates of both the prokaryotic abundance and their average weight.

A census published in PNAS in May 2018 estimated global bacterial biomass at ≈70 billion tonnes C, of which ≈60 billion tonnes are in the terrestrial deep subsurface. It also estimated the global biomass of archaea at ≈7 billion tonnes C. A later study by the Deep Carbon Observatory published in 2018 reported a much larger dataset of measurements, and updated the total biomass estimate in the deep terrestrial biosphere. It used this new knowledge and previous estimates to update the global biomass of bacteria and archaea to 23–31 billion tonnes C.{{Cite journal |last1=Magnabosco |first1=C. |last2=Lin |first2=L.-H. |last3=Dong |first3=H. |last4=Bomberg |first4=M. |last5=Ghiorse |first5=W. |last6=Stan-Lotter |first6=H. |last7=Pedersen |first7=K. |last8=Kieft |first8=T. L. |last9=van Heerden |first9=E. |last10=Onstott |first10=T. C. |date=24 September 2018 |title=The biomass and biodiversity of the continental subsurface |url=https://www.nature.com/articles/s41561-018-0221-6 |journal=Nature Geoscience |language=en |volume=11 |issue=10 |pages=707–717 |doi=10.1038/s41561-018-0221-6 |bibcode=2018NatGe..11..707M |s2cid=133768246 |issn=1752-0908 |archive-date=15 January 2023 |access-date=10 July 2023 |archive-url=https://web.archive.org/web/20230115092808/https://www.nature.com/articles/s41561-018-0221-6 |url-status=live }} Roughly 70% of the global biomass was estimated to be found in the deep subsurface.{{Cite web |last=Observatory |first=Deep Carbon |title=Life in deep Earth totals 15 to 23 billion tons of carbon—hundreds of times more than humans |url=https://phys.org/news/2018-12-life-deep-earth-totals-billion.html |access-date=2023-07-24 |website=phys.org |language=en}} The estimated number of prokaryotic cells globally was estimated to be 11–15 × 10²⁹. With this information, the authors of the May 2018 PNAS article revised their estimate for the global biomass of prokaryotes to ≈30 billion tonnes C,{{Cite journal |last1=Bar-On |first1=Yinon M. |last2=Milo |first2=Ron |date=21 February 2019 |title=Towards a quantitative view of the global ubiquity of biofilms |url=https://www.nature.com/articles/s41579-019-0162-0 |journal=Nature Reviews Microbiology |language=en |volume=17 |issue=4 |pages=199–200 |doi=10.1038/s41579-019-0162-0 |pmid=30792541 |s2cid=67789580 |issn=1740-1534 |archive-date=10 July 2023 |access-date=10 July 2023 |archive-url=https://web.archive.org/web/20230710122853/https://www.nature.com/articles/s41579-019-0162-0 |url-status=live }} similar to the Deep Carbon Observatory estimate.

These estimates convert global abundance of prokaryotes into global biomass using average cellular biomass figures that are based on limited data. Recent estimates used an average cellular biomass of about 20–30 femtogram carbon (fgC) per cell in the subsurface and terrestrial habitats.{{Cite journal |last1=Griebler |first1=Christian |last2=Mindl |first2=Birgit |last3=Slezak |first3=Doris |last4=Geiger-Kaiser |first4=Margot |date=2002-06-26 |title=Distribution patterns of attached and suspended bacteria in pristine and contaminated shallow aquifers studied with an in situ sediment exposure microcosm |url=https://www.int-res.com/abstracts/ame/v28/n2/p117-129/ |journal=Aquatic Microbial Ecology |language=en |volume=28 |issue=2 |pages=117–129 |doi=10.3354/ame028117 |issn=0948-3055 |doi-access=free |archive-date=10 July 2023 |access-date=10 July 2023 |archive-url=https://web.archive.org/web/20230710141755/https://www.int-res.com/abstracts/ame/v28/n2/p117-129/ |url-status=live }}

{{ external media

| headerimage=

| float = right

| width = 240px

| image1 = [https://www.visualcapitalist.com/all-the-biomass-of-earth-in-one-graphic Visualizing the biomass of life]

}}

The total global biomass has been estimated at 550 billion tonnes C.Groombridge B, Jenkins MD (2000) [https://books.google.com/books?id=_kHeAXV5-XwC Global biodiversity: Earth's living resources in the 21st century] p. 11. World Conservation Monitoring Centre, World Conservation Press, Cambridge A breakdown of the global biomass is given by kingdom in the table below, based on a 2018 study by Bar-On et. al.

File:Seawifs global biosphere.jpg

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.{{cite journal | vauthors = Field CB, Behrenfeld MJ, Randerson JT, Falkowski P | title = Primary production of the biosphere: integrating terrestrial and oceanic components | journal = Science | volume = 281 | issue = 5374 | pages = 237–240 | date = July 1998 | pmid = 9657713 | doi = 10.1126/science.281.5374.237 | bibcode = 1998Sci...281..237F | url = http://www.escholarship.org/uc/item/9gm7074q | archive-date = 25 September 2018 | access-date = 7 February 2019 | archive-url = https://web.archive.org/web/20180925215921/https://escholarship.org/uc/item/9gm7074q | url-status = live }} 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 the total annual production, oceanic autotrophs account for only about 0.2% of the total biomass.

Terrestrial freshwater ecosystems generate about 1.5% of the global net primary production.{{cite book| last = Alexander| first = David E. | name-list-style = vanc | title = Encyclopedia of Environmental Science| publisher = Springer| date = 1999| isbn = 978-0-412-74050-3 }}

Some global producers of biomass, in order of productivity rates, are

{{col div|colwidth=30em}}

• {{annotated link|Biomass}}
• {{annotated link|Biomass (energy)}}
• Biomass partitioning
• {{annotated link|Organic matter}}
• {{annotated link|Productivity (ecology)}}
• {{annotated link|Primary nutritional groups}}
• {{annotated link|Population density|Standing stock}}
• Slash-and-burn
• Stubble burning
• {{annotated link|Lake Pohjalampi}} - a biomass manipulation study
• {{annotated link|List of commercially important fish species}}

{{colend}}

{{Reflist}}

{{refbegin}}

• {{cite journal | vauthors = Foley JA, Monfreda C, Ramankutty N, Zaks D | title = Our share of the planetary pie | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 31 | pages = 12585–12586 | date = July 2007 | pmid = 17646656 | pmc = 1937509 | doi = 10.1073/pnas.0705190104 | bibcode = 2007PNAS..10412585F | doi-access = free }}
• {{cite journal|author-link9=Marina Fischer-Kowalski | vauthors = Haberl H, Erb KH, Krausmann F, Gaube V, Bondeau A, Plutzar C, Gingrich S, Lucht W, Fischer-Kowalski M | title = Quantifying and mapping the human appropriation of net primary production in earth's terrestrial ecosystems | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 31 | pages = 12942–12947 | date = July 2007 | pmid = 17616580 | pmc = 1911196 | doi = 10.1073/pnas.0704243104 | bibcode = 2007PNAS..10412942H | doi-access = free }}
• {{cite book | last1 = Purves | first1 = William K | last2 = Orians | first2 = Gordon H | name-list-style = vanc | year = 2007 | title = Life: The Science of Biology | edition = 8th | publisher = W. H. Freeman | isbn = 978-1-4292-0877-2 }}

{{refend}}

{{Wiktionary|biomass}}

• [https://biocubes.net Biocubes: a visualization of biomass and technomass]
• [https://www.vox.com/science-and-health/2018/5/29/17386112/all-life-on-earth-chart-weight-plants-animals-pnas The mass of all life on Earth is staggering — until you consider how much we've lost]
• [http://whyfiles.org/shorties/count_bact.html Counting bacteria] {{Webarchive|url=https://web.archive.org/web/20131212004814/http://whyfiles.org/shorties/count_bact.html |date=12 December 2013 }}
• [https://web.archive.org/web/20081216224504/http://www.marietta.edu/~mcshaffd/lead/trophic.pdf Trophic levels]
• [https://web.archive.org/web/20090204052057/http://www.seaaroundus.org/flash/NorthAtlanticTrends.htm Biomass distributions for high trophic-level fishes in the North Atlantic, 1900–2000]

{{modelling ecosystems}}

{{aquatic ecosystem topics|expanded=none}}

{{DEFAULTSORT:Biomass (Ecology)}}

Category:Ecology terminology

Category:Environmental terminology

Category:Ecological metrics

Category:Ecosystems

Category:Fisheries science