Determining the Primary Productivity of the Macrophytes in Tamdil Lake, Mizoram, Northeast India

The present investigation has been carried out for determining the net primary productivity (NPP) of the macrophytes found in Tamdil Lake, Mizoram. Both monthly and daily NPP of the macrophytes were evaluated for a period of two years. The findings clearly indicate that Alternanthera philoxeroides has the highest monthly NPP values (range: 2.18 to 24.42 gm–2 month–1; mean value 18.54 ± 2.12 gm–2 month–1), followed by Echinochloa stagnina (range: 0.91 to 10.94 gm–2 month–1; mean value 7.69 ± 1.97 gm–2 month–1), Eichhornia crassipes (range: 0.63 to 15.93 gm–2 month–1; mean value 12.74 ± 3.14 gm–2 month–1) and Kyllinga tenuifolia (range: 0.20 to 8.61 gm–2 month–1; mean value 7.02 ± 1.95 gm–2 month–1). This was followed progressively by Nymphaea pygmaea helvola with values of 1.08 to 17.11 gm–2 month–1. The monthly NPP of ‘other species’ ranged from 0.38 to 8.01 gm–2 month–1 (mean value 6.06 ± 2.08 gm–2 month–1). The monthly NPP of all the species (combined) reported a range of 0.89 to 119.82 gm–2 month–1 (mean value of 63.50 ± 2.99 gm–2 month–1). For estimation of daily NPP of the macrophytes, Alternanthera philoxeroides reported the peak daily NPP (range: 0.15 to 1.26 gm–2 day–1 with mean value of 0.87 ± 1.39 gm–2 day–1), followed closely by Eichhornia crassipes (range: 0.09 to 0.83 gm–2 day–1; mean value of 0.53 ± 1.42 gm–2 day–1, Nymphaea pygmaea helvola (range: 0.09 to 0.81 gm–2 day–1, mean value of 0.49 ± 2.13 gm–2 day–1), Echinochlo astagnina (range: 0.07 to 0.59 gm–2 day–1 with a mean value of 0.27 ± 0.98 gm–2 day–1. It has been found that the daily NPP of ‘other species’ ranged from 0.03 to 0.47 gm–2 day–1 with a mean value of 0.23 ± 0.92 gm–2 day–1.The daily NPP of all species (combined) ranged from 0.05 to 3.46 gm–2 day–1 with a mean value of 2.47 ± 2.28 gm–2 day–1. The macrophyte NPP varied significantly during the study period. Moderately higher daily NPP values of macrophytes indicates that the lake is approaching towards eutrophic status.