Evaluation of trophic status and its limiting factors in the Renuka Lake of Lesser Himalaya, India.

The present study is to evaluate trophic status and its limiting factors in the Renuka Lake, using surface water samples. The water of the lake is found to be slightly alkaline with pH 8.33-8.70 (avg. 8.61 ± 0.1). The turbidity 4.63-6.62 NTU (avg. 5.48 ± 0.63 NTU) indicated low level of clarity in the lake. The Carlson's index based on the Secchi disc transparency (SD), chlorophyll-a (Chl-a), and total phosphorus (TP) has indicated that the Renuka Lake is turned hyper-eutrophic in status. The correlation coefficient has indicated that most parameters in the lake are contributed by different sources. Factor-1 marked 26.40% variance, which may be due to higher impact of rock weathering than the anthropogenic activities, whereas 18.56% variance shown by factor-2 may be due to natural and anthropogenic activities. However, factor-3 (14.38% variance) inferred that the higher contribution of Chl-a, pH, TDS, NH4+, NO3-, salinity, and SO42- is due to major impacts of the anthropogenic activities. The inverse distance weighting method has indicated spatial interpolation and area of influence of different parameters in the lake. The "nutrient (TP) limited large sized algae" as well as phosphorus is considered as a major limiting factor for increasing productivity and trophic state index. The present study has inferred that the nutrient enrichment should be controlled to restore the Renuka Lake, owing to its social and ecological significances.