Biological productivity of water bodies
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Biological productivity of water bodies



Biological productivity of water bodies

Biological productivity of water bodies



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  • In the present discussion we shall look first at primary production and then show this influences secondary production in water bodies.

Biological productivity of water bodies Biological productivity of water bodies Presentation Transcript

  • BIOLOGICAL PRODUCTIVITY OF WATER BODIES Jitendra Kumar Depat. Fisheries Resource Management) College of Fisheries, Mangalore
  • Introduction • Biological productivity as an index of water quality and production potential of cultured organism needs prime consideration for site selection. • Productivity quantitative in terms of qualitative and • Before we enter into a discussion on productivity, it would be helpful to look at the concepts of the ecosystem, habitat and ecological niche, and food cycle in water bodies, including food chain and trophic structure.
  • What is an ecosystem? • An ecosystem is formed by the interactions between all living and non-living things • Ecosystem is the basic functional unit of ecology in which include both living and non-living things • Eco= Environment • System = Regularly interacting and interdependent components forming a unified whole • Ecosystem = an ecological system; = a community and its physical environment treated together as a functional system
  • Components of an Ecosystem ABIOTIC COMPONENTS Sunlight Temperature Precipitation Water or moisture Soil or water chemistry etc. BIOTIC COMPONENTS Primary producers Herbivores Carnivores Omnivores Detritivores etc.
  • Habitat and ecological niche Habitat and niche • “the place Habitat = Address or home of an organism Niche = Occupation of an organism in its where it lives”, community • whereas the ecological niche • Term coined by Elton in 1927.
  • Food cycle in water bodies The transfer of food energy from the plants through a series of organisms is referred to as the “food chain”.
  • • The term “productivity” is always used in this context to mean „rate of production‟ or „rate of energy flow‟. • Gross production (PG) • Net production (PN) • Secondary productivities (P2 - P5)
  • Concept of productivity • The biological productivity of aquatic systems, as of land, has been at several levels. • Primary productivity • Gross • Net primary productivity • Secondary – various trophic levels
  • • Basic or primary productivity – rate at which energy is stored by photosynthetic activity of producer organisms – (chlorophyll bearing organisms, mainly plants and phytoplankton) – In the form of organic substances which can be used as food substances.
  • • Gross primary productivity –The total rate of photosynthesis including organic matter used up in respiration during the measurement period –(also known as total photosynthesis or total assimilation).
  • • Net primary productivity –The rate of storage of energy as food matter i.e. excluding the energy dissipated as respiration by plants –(also referred to as “apparent” photosynthesis or net assimilation).
  • • Secondary productivity –The rates of energy storage at trophic levels of consumers and decomposers are referred to as “secondary productivities”;
  • Measurement of productivity Harvest method • This is the simplest and measuring the productivity of a water body such as fish pond by harvest at the end of the season. • The productivity given is secondary productivity and indicates net productivity and also quite often fish production given is in net weight giving productivity value.
  • Oxygen measurement method • Primary productivity can be measured from the amount of oxygen consumed by a volume of water in a fixed period of time • White and dark bottles • (bottle painted dark so light would not enter) • Do (dissolved oxygen) measurement • BOD
  • Diel method • Estimates of primary productivity can also be made from diel changes in oxygen, considering the day as the light bottle and night as the dark bottle. • The increase in DO in the day time is net primary production and the decrease in the night is half the diel respiration. • This can be added on to the day-time gain to obtain daily gross photosynthesis. • This volume should normally be corrected for the loss or gain in oxygen due to concentration gradient over the day.
  • C14 method • The most accurate method for determining productivity is the method of using radioactive carbon (C14) added as carbonate. • Labelled carbonate is added into a bottle containing water with the phytoplankton and other organisms and after a short period of time the plankton is separated • dried and planchetted and the radioactive carbon fixed can be measured from the radioactive counts made. • The productivity measured thus is net primary productivity as the carbon fixed in the tissues only are measured here.
  • References • • • l-productivity • • urrent/lectures/kling/ecosystem/ecosystem.html • •