Primary production

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The phytoplankton gain energy through photosynthesis and produce biomass

In ecology, the term primary production refers to the production of biomass by producers , i.e. plants , algae , cyanobacteria and other autotrophic bacteria , using light or chemical energy from inorganic substances. The discipline of ecology that deals with biological production is called production biology .

Primary production is partly as gross production again for the respiration of the subject ( respiration used), left the net primary production, which is used for the growth and proliferation of Phytomasse remain (s. U.). About 1% of the solar radiation that reaches the earth is converted into biomass. Primary production forms the basis for the organic carbon cycle .

In oceanology and limnology , the primary production is the production of phytoplankton in the ocean and fresh water, which get their energy through photosynthesis , using nutrients . These small green cells are in turn consumed by the heterotrophic first-order consumers , small animals such as ciliates , copepods and krill . Primary production is the basis of all life in the pelagic , i.e. H. remote area of ​​the oceans.

On the sea ​​floor , the marine Benthal , for example at the Black Smokers on the mid-ocean ridge , there is an ecosystem of its own. Its basis is not photosynthesis, but chemosynthesis , i.e. the generation of energy by breaking down inorganic compounds such as hydrogen sulfide . There, geothermal energy is ultimately the source of all life processes, while in the photosynthesis process this is the energy of the sun.

In terrestrial ecosystems , primary production takes place via photosynthesis by plants , for example the trees in the forest . Primary production through chemosynthesis ( chemotrophy ) does not play a role here.

Productivity is measured in grams of dry weight per square meter per year. The highest primary production takes place in the Wadden Sea and in the tropical rainforests .

Most of the primary production is converted back into inorganic substances by the consumers and destructors . The surplus forms peat and water sludge, from which coal and crude oil arise in geological periods .

Gross primary production and net primary production

As gross primary production (Engl. Gross primary production ) refers to the whole of autotrophic fixed organisms amount of carbon in an ecosystem. This depends on the climate, which in turn has an influence on the photosynthesis rate and the leaf area index . The energy converted through photosynthesis can either be breathed in ( respiration ) or used for growth in the plant .

If one subtracts the respiration of the autotrophic organisms from the gross primary production , one obtains the net primary production (NPP). This represents the entire biomass that was obtained from plants through photosynthesis. This biomass also represents a carbon store in the carbon cycle. In the plant, the carbon is used differently and used differently in different tissues in order to better adapt to the environmental conditions. In nutrient-poor areas, for example, there is an increased allocation of carbon in the roots.

Net primary production is an important ecosystem function . In addition, it is the most basic source of energy for heterotrophic organisms and is strongly linked to the carbon cycle.

Measurement methods

The exact measurement of the NPP is not possible in nature. But methods have been developed that can give good estimates. The net primary production can be estimated by measuring the increase in biomass. However, this method is not very precise and is impractical especially for large and very diverse ecosystems. The measurement of the chlorophyll concentration is mainly used there. Chlorophyll has a characteristic spectral signature that is perceived by satellites. It absorbs light in the red and blue spectral range and reflects infrared radiation more strongly than water or dry soil. An estimate can then be made with this value. A third possibility is the measurement of gross primary production and respiration. The respiration can be determined by means of the changed CO 2 concentration in a closed system.

The calculation of the net primary production is based on the net assimilation rate (NAR), the leaf area index (LAI) and the production period (t): NPP = NAR * LAI * t

Individual evidence

  1. ^ P. Sitte, H. Ziegler, F. Ehrendorfer, A. Bresinsky: Textbook of botany at universities. Founded by E. Strasburger. 33rd edition. Verlag G. Fischer, Stuttgart 1991, ISBN 3-437-20447-5 .
  2. In the current edition of the Strasburgers (37th edition) this information can no longer be found. A significantly different scale is now being considered - a leaf instead of the global biosphere. There it is now said that a leaf can use a maximum of 1–2% of the photosynthetically active radiation for photochemical energy binding (see p. 761).
  3. ^ DM Sigman, MP Hain: The Biological Productivity of the Ocean . (PDF) In: Nature Education Knowledge . 3, No. 6, 2012, pp. 1-16. Retrieved June 1, 2015. "Gross primary production" (GPP) refers to the total rate of organic carbon production by autotrophs, while "respiration" refers to the energy-yielding oxidation of organic carbon back to carbon dioxide. “Net primary production” (NPP) is GPP minus the autotrophs' own rate of respiration; it is thus the rate at which the full metabolism of phytoplankton produces biomass. "Secondary production" (SP) typically refers to the growth rate of heterotrophic biomass. "
  4. ^ ML Cain, WD Bowman, SD Hacker: Ecology. 2nd Edition. Sinauer Assoc., 2011, ISBN 978-0-87893-445-4 .
  6. ^ TM Smith, RL Smith: Ecology. 6th edition. Pearson Studium, 2009, ISBN 978-3-8273-7313-7 .