8. Measurement of productivity
Several methods are used in measure of productivity or rate of yield. (see separate Practicals Release on the theme).
Harvest method acting: This is the simplest and measure the productiveness of a water system body such as fish pond by hervest at the end of the season. The productiveness given is secondary productiveness and indicates take-home productivity and also quite a great deal fish production given is in profit weight giving productivity value.
8.1 Oxygen measurement method:
Main productiveness can be measured from the amount of atomic number 8 consumed by a mass of water in a fixed period; water for which productivity is to be observed is enclosed in sealed T. H. White and dark bottles (bottleful painted dark so light would non enter). Do (dissolved oxygen) measurement of water is made at the rootage of the submerging period. The two bottles are then immersed in the water body concerned at the charge from which the water is taken. The phytoplankton and other elements in the water give rise oxygen in the water bottle, but some oxygen disappears due to respiration. The last mentioned is measured from the readings of dark nursing bottle, where only respiration takes place. Thus from the atomic number 8 produced by photosynthesis of enclosed organism (representing a sample of the pee trunk) can be known. Nonetheless this oxygen production indicates nett primary productivity only. From the DO difference of opinion in dark botfle oxygen consumed by the enclosed organisms can make up obtained and when this respiration value is added to the oxygen yield in the whiten bottle, a value for gross basal productivity is obtained.
8.2 Diel method:
Estimates of primary productivity posterior 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 minify in the night is half the diel respiration. This can be added along to the mean solar day-clock time gain to obtain day-to-day gross photosynthesis. This volume should normally be corrected for the loss or gain in oxygen due to concentration gradient over the twenty-four hour period.
8.3 C14 method:
The well-nig close method for decisive productiveness is the method acting of victimization radioactive carbon (C14) added American Samoa carbonate. Labelled carbonate is added into a feeding bottle containing water with the phytoplankton and other organisms and after a short period of meter the plankton is separated, preserved and planchetted and the hot atomic number 6 fixed can embody measured from the radioactive counts made. The productiveness plumbed hence is net primary productivity equally the carbon fixed in the tissues only are measured present.
In selecting a weewe body for aquaculture measure of primary productivity and estimate of potential yield would be of great assistance in planning the culture activity. This would be specially done while evaluating water bodies (natural or adult male-made) for stocking(in extensive finish) and too for cage and envelopment culture.
what are three ways primary productivity can be measured
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