Biomass 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. [3] 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 some applications, biomass is measured as the mass of organically bound carbon (C) that is present.
In 2018, Bar-On et al. estimated the total live biomass on Earth at about 550 billion (5.5×1011) tonnes C, [1] most of it in plants. In 1998 Field et.al. estimated the total annual net primary production of biomass at just over 100 billion tonnes C/yr. [4] The total live biomass of bacteria was once thought to be about the same as plants, [5] but recent studies suggest it is significantly less. [1] [6] [7] [8] [9] The total number of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at (5.3±3.6)×1037, and weighs 50 billion tonnes. [10] [11] Anthropogenic mass (human-made material) is expected to exceed all living biomass on earth at around the year 2020. [12]
An ecological pyramid is a graphical representation that shows, for a given ecosystem, the relationship between biomass or biological productivity and trophic levels.
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 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. [13] Biomass in C3 and C4 plant species can change in response to altered concentrations of CO2. [14] C3 plant species have been observed to increase in biomass in response to increasing concentrations of CO2 of up to 900 ppm. [15]
marine food chain (typical) |
---|
Sun |
↓ |
phytoplankton |
↓ |
herbivorous zooplankton |
↓ |
carnivorous zooplankton |
↓ |
filter feeder |
↓ |
predatory vertebrate |
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
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. [16] 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. [17] Prochlorococcus is ubiquitous between 40°N and 40°S and dominates in the oligotrophic (nutrient poor) regions of the oceans. [18] 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. [19]
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, [20] dominated by bacteria. [1]
Geographic location | Number of cells (× 1029) | Billion tonnes of carbon |
---|---|---|
Open ocean | ||
Ocean subsurface | 5 [20] | 10 [20] |
Terrestrial soil | 3 [1] | 8 [1] |
Terrestrial subsurface | 2 to 6 [20] | 4 to 12 [20] |
Total | 11 to 15 [20] | 23 to 31 [20] |
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 [5] 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. [1] [5] 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 [6] 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. [1] 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. [20] Roughly 70% of the global biomass was estimated to be found in the deep subsurface. [7] [21] The estimated number of prokaryotic cells globally was estimated to be 11–15 × 1029. [20] With this information, the authors of the May 2018 PNAS article [1] revised their estimate for the global biomass of prokaryotes to ≈30 billion tonnes C, [22] similar to the Deep Carbon Observatory estimate. [20]
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. [1] [20] [23]
External image | |
---|---|
Visualizing the biomass of life |
The total global biomass has been estimated at 550 billion tonnes C. [24] [1] A breakdown of the global biomass is given by kingdom in the table below, based on a 2018 study by Bar-On et. al. [1]
Kingdom | Global biomass in billion tonnes of carbon | Global dry biomass in billion tonnes | Global wet biomass in billion tonnes | Image |
---|---|---|---|---|
450 [1] | 900 | 2700 | ||
60 | 200 | |||
12 [1] | 24 | 80 | ||
4 [1] | 8 | 25 | ||
2 [1] | 4 | 13 | ||
Total | 500 | 1000 | 3000 |
Animals represent less than 0.5% of the total biomass on Earth, with about 2 billion tonnes C in total. Most animal biomass is found in the oceans, where arthropods, such as copepods, account for about 1 billion tonnes C and fish for another 0.7 billion tonnes C. [1] Roughly half of the biomass of fish in the world are mesopelagic, such as lanternfish, [25] spending most of the day in the deep, dark waters. [26] Marine mammals such as whales and dolphins account for about 0.006 billion tonnes C. [27] Land animals account for about 500 million tonnes C, or about 20% of the biomass of animals on Earth. [1] Terrestrial arthropods account for about 150 million tonnes C, most of which is found in the topsoil. [28] Land mammals account for about 180 million tonnes C, most of which are humans (about 80 million tonnes C) and domesticated mammals (about 90 million tonnes C). Wild terrestrial mammals account for only about 3 million tonnes C, less than 2% of the total mammalian biomass on land. [27]
Most of the global biomass is found on land, with only 5 to 10 billion tonnes C found in the oceans. [24] On land, there is about 1,000 times more plant biomass (phytomass) than animal biomass (zoomass). [29] About 18% of this plant biomass is eaten by the land animals. [30] However, marine animals eat most of the marine autotrophs, and the biomass of marine animals is greater than that of marine autotrophs. [1] [30]
According to a 2020 study published in Nature , human-made materials, or anthropogenic mass, outweigh all living biomass on earth, with plastic alone exceeding the mass of all land and marine animals combined. [31] [12] [32]
name | number of species | date of estimate | individual count | mean living mass of individual | percent biomass (dried) | global dry biomass in million tonnes | global wet (fresh) biomass in million tonnes | |
---|---|---|---|---|---|---|---|---|
Terrestrial | 1 | November 2022 | 8 billion [33] | 40% [35] | 160 | 400 [27] | ||
2005 | 4.63 billion adults | 287 [36] | ||||||
1 | 2021 | 1.5 billion [37] | 300 kg | 30% | 125 | 416 [27] | ||
1 | 2021 | 1.3 billion [37] | 30 kg | 30% | 12 | 39 [27] | ||
1 | 2021 | 1.1 billion [37] | 30 kg | 30% | 10 | 32 [27] | ||
1 | 2021 | 26 billion | 0.9 kg for broilers, 1.8 kg for layers [38] | 30% | 8 [1] | 25 | ||
15,700 [39] | 2022 | 22.8% [40] | 10–100 [39] | 40–450 | ||||
7,000–30,000 [41] | 2016 | 10 mg (dry weight) [42] | 10–25% [43] | 400 [1] | 1,600 | |||
2022 | 2 mg [40] | 27% [40] | 440 [45] | |||||
2019 | 4.4×1020 [46] | 20% [40] | 60 | 300 [46] | ||||
Marine | 1 | Pre-whaling | 340,000 | 40% [48] | 36 | |||
2023 | 50,000 [27] | 60,000 kg | 40% [48] | 1.2 | 3 [27] | |||
>20,000 [49] | 2022 | 30% [50] | 3,000 | 9,000 [26] | ||||
1 | 2008 | 0.486 g [51] | 379 (in peak season) [51] | |||||
13,000 | 10−6–10−9 kg | |||||||
? | 2003 | 1,000 [52] |
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. [4] 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.
Terrestrial freshwater ecosystems generate about 1.5% of the global net primary production. [53]
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 | [2] | 5.7 | [54] | |
Tropical rainforests | 2,000 | [55] | 8 | 16 | |
Coral reefs | 2,000 | [2] | 0.28 | [56] | 0.56 |
Algal beds | 2,000 | [2] | |||
River estuaries | 1,800 | [2] | |||
Temperate forests | 1,250 | [2] | 19 | 24 | |
Cultivated lands | 650 | [2] [57] | 17 | 11 | |
Tundras | 140 | [2] [57] | 11.5–29.8 | [58] [59] | |
Open ocean | 125 | [2] [57] | 311 | 39 | |
Deserts | 3 | [57] | 50 | 0.15 |
The biosphere, also called the ecosphere, is the worldwide sum of all ecosystems. It can also be termed the zone of life on Earth. The biosphere is virtually a closed system with regard to matter, with minimal inputs and outputs. Regarding energy, it is an open system, with photosynthesis capturing solar energy at a rate of around 100 terawatts. By the most general biophysiological definition, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, cryosphere, hydrosphere, and atmosphere. The biosphere is postulated to have evolved, beginning with a process of biopoiesis or biogenesis, at least some 3.5 billion years ago.
The carbon cycle is that part of the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of Earth. Other major biogeochemical cycles include the nitrogen cycle and the water cycle. Carbon is the main component of biological compounds as well as a major component of many rocks such as limestone. The carbon cycle comprises a sequence of events that are key to making Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration (storage) to and release from carbon sinks.
Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words φυτόν, meaning 'plant', and πλαγκτός, meaning 'wanderer' or 'drifter'.
Zooplankton are the heterotrophic component of the planktonic community, having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean, or by currents in seas, lakes or rivers.
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.
The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).
The mesopelagiczone, also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the depths of this zone are between approximately 200 to 1,000 meters below the ocean surface.
Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, plants, algae, fungi, protists, single-celled microorganisms and associated viruses living in the saline water of marine habitats, either the sea water of marginal seas and oceans, or the brackish water of coastal wetlands, lagoons, estuaries and inland seas. As of 2023, more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. Marine life is studied scientifically in both marine biology and in biological oceanography.
Gelatinous zooplankton are fragile animals that live in the water column in the ocean. Their delicate bodies have no hard parts and are easily damaged or destroyed. Gelatinous zooplankton are often transparent. All jellyfish are gelatinous zooplankton, but not all gelatinous zooplankton are jellyfish. The most commonly encountered organisms include ctenophores, medusae, salps, and Chaetognatha in coastal waters. However, almost all marine phyla, including Annelida, Mollusca and Arthropoda, contain gelatinous species, but many of those odd species live in the open ocean and the deep sea and are less available to the casual ocean observer. Many gelatinous plankters utilize mucous structures in order to filter feed. Gelatinous zooplankton have also been called Gelata.
In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below, which is referred to as the biological pump. Export production is the amount of organic matter produced in the ocean by primary production that is not recycled (remineralised) before it sinks into the aphotic zone. Because of the role of export production in the ocean's biological pump, it is typically measured in units of carbon. The term was coined by explorer William Beebe as observed from his bathysphere. As the origin of marine snow lies in activities within the productive photic zone, the prevalence of marine snow changes with seasonal fluctuations in photosynthetic activity and ocean currents. Marine snow can be an important food source for organisms living in the aphotic zone, particularly for organisms that live very deep in the water column.
In ecology, the term productivity refers to the rate of generation of biomass in an ecosystem, usually expressed in units of mass per volume per unit of time, such as grams per square metre per day. 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.
The Boring Billion, otherwise known as the Mid Proterozoic and Earth's Middle Ages, is an informal geological time period between 1.8 and 0.8 billion years ago (Ga) during the middle Proterozoic eon spanning from the Statherian to the Tonian periods, characterized by more or less tectonic stability, climatic stasis and slow biological evolution. Although it is bordered by two different oxygenation events and two global glacial events, the Boring Billion period itself actually had very low oxygen levels and no geological evidence of glaciations.
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism is any microscopic living organism or virus, which is invisibly small to the unaided human eye without magnification. Microorganisms are very diverse. They can be single-celled or multicellular and include bacteria, archaea, viruses, and most protozoa, as well as some fungi, algae, and animals, such as rotifers and copepods. Many macroscopic animals and plants have microscopic juvenile stages. Some microbiologists also classify viruses as microorganisms, but others consider these as non-living.
This is a collection of lists of organisms by their population. While most of the numbers are estimates, they have been made by the experts in their fields. Species population is a science falling under the purview of population ecology and biogeography. Individuals are counted by census, as carried out for the piping plover; using the transect method, as done for the mountain plover; and beginning in 2012 by satellite, with the emperor penguin being first subject counted in this manner.
Particulate organic matter (POM) is a fraction of total organic matter operationally defined as that which does not pass through a filter pore size that typically ranges in size from 0.053 millimeters (53 μm) to 2 millimeters.
The viral shunt is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms. The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM.
A marine food web is a food web of marine life. At the base of the ocean food web are single-celled algae and other plant-like organisms known as phytoplankton. The second trophic level is occupied by zooplankton which feed off the phytoplankton. Higher order consumers complete the web. There has been increasing recognition in recent years that marine microorganisms.
Marine viruses are defined by their habitat as viruses that are found in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Viruses are small infectious agents that can only replicate inside the living cells of a host organism, because they need the replication machinery of the host to do so. They can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.
Marine prokaryotes are marine bacteria and marine archaea. They are defined by their habitat as prokaryotes that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. All cellular life forms can be divided into prokaryotes and eukaryotes. Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, whereas prokaryotes are the organisms that do not have a nucleus enclosed within a membrane. The three-domain system of classifying life adds another division: the prokaryotes are divided into two domains of life, the microscopic bacteria and the microscopic archaea, while everything else, the eukaryotes, become the third domain.
Cytophagales is an order of non-spore forming, rod-shaped, Gram-negative bacteria that move through a gliding or flexing motion. These chemoorganotrophs are important remineralizers of organic materials into micronutrients. They are widely dispersed in the environment, found in ecosystems including soil, freshwater, seawater and sea ice. Cytophagales is included in the Bacteroidota phylum.
the tundra is a vast and treeless land which covers about 20% of the Earth's surface, circumnavigating the North pole.