Estimation of primary productivity of investigated pond (Khutabandh, Dumka) by light and dark bottle method

                                      Smriti Singh

                                 Research Scholar

              S.K.M.University, Dumka (Jharkhand)

             Email ID- smriti22071991@gmail.com
                   My YouTube Channel ID              
             https://www.youtube.com/channel/UCtgeDks-CtWm7LBfE2oXJjQ?view_as=subscriber

Requirements-

• Light and Dark reagent bottle of 250ml
• Conical flask
• Measuring cylinder
• Beaker
• Pipette
• MnSO₄
• Alkaline Iodide
• Conc. H₂SO₄
• Sodium thiosulphate
• Freshly prepared starch solution

Theory-

Primary productivity is the rate of conversion of solar energy to chemical energy through photosynthesis by the producers. It is the amount of carbon fixed in unit time which has been converted into organic material through the process of photosynthesis.

Phytoplankton constitute a major primary producer of a freshwater ecosystem. Primary productivity is the most important biological phenomenon in the aquatic ecosystem where solar energy assimilated by the producer including organic matter used subsequently in respiration is known as Gross Primary Productivity (GPP). Producer while synthesizing organic matter also consume energy obtained from the oxidation of organic matter which is utilized in the Community Respiration (CR).

The amount of organic matter remains stored in producer biomass after respiration is known as Net Primary Productivity (NPP).     

Procedure-

Primary Productivity in aquatic ecosystem may be estimated by Light and Dark bottle method, as prescribed by Gaarder and Gran (1927).

Surface water sample from littoral zone of a perennial pond Khutabandh, Dumka was collected in a set of light and dark reagent bottle (250ml) and incubated in the water on the spot at 10cm below the surface layer of water. It was fixed on a bamboo pole for a period of 4 hours (9:00AM – 1:00PM). Dissolve oxygen contain of initial bottle, light bottle and dark bottle were estimated by Winkler’s Iodometric method prescribed by Welch (1948). The initial value of DO content at the time of incubation was analyzed on the spot where as light and dark bottle value of DO was estimated after incubation hour 9:00AM – 1:00PM.

Analyzed value of DO was depicted in tabular form accordingly GPP, NPP and CR value where derived according to Wood (1975) to recommended the use of following formula to convert DO₂ value (ppm) to its carbon value in gram equivalent.

Calculation-

DO₂ of Initial Bottle (IB)-

Volume of Na₂S₂O₃ consumed during titration of 100ml treated sample = 3.5 ml

DO₂ content in water sample = 3.5 × 2= 7.0ppm

DO₂ of Light Bottle (LB)- 9.7ppm

DO₂ of Dark Bottle (DB)- 5.8ppm

GPP (gC/m³/h) = LB – DB/Time × 0.375/ PQ

Where, PQ= 1.2

                           =  9.7 – 5.8/ 4 × 0.375/1.2

                           = 0.975 × 0.3125

                           = 0.30468 gC/m³/h

NPP (gC/m³/h) = LB – IB/Time × 0.375/ PQ

                            = 9.7 – 7.0/4 × 0.375/1.2

                            = 0.675 × 0.3125

                            = 0.1875 gC/m³/h

CR (gC/m³/h) = IB – DB/Time × 0.375 × RQ

Where, RQ = 1.0

                        = 7.0 – 5.8/4 × 0.375 × 1.0

                        = 0.3 × 0.375 × 1.0

                        = 0.140625 gC/m³/h

P/R = GPP/R

         = 0.30468/0.140625

         = 2.1666

If P/R is greater than 1 then it is said to be autotrophic and if it is less than 1 then it is said to be heterotrophic.

In my calculation, P/R is greater than 1. So, it is autotrophic.