Abundance and nutrient limiting growth rate of heterotrophic bacterio-plankton in Himalayan foot hill Lake Phewa, Nepal

We examined heterotrophic bacterial abundance, chlorophyll- a concentration and resources limiting bacterial growth from October 2004 to August 2005 in Lake Phewa. The lake has a large watershed that covers ≈435 ha of water surface surrounded by ≈23-time large catchment area that might receive up to 4850 mm annual precipitation. During the study, bacterial abundance ranged from 3.2 to 9.9 × 10⁶ cells mL^?1, and chlorophyll- a varied from 2 to 32 μg L^?1. Bacterial abundance and chlorophyll- a weakly correlated ( r  = 0.40, n  = 77, P  < 0.1) in the lake. Experiments on resources, glucose (C), nitrogen (N), phosphorus (P) alone and in combination (CNP) limiting bacterial growth rate, were examined using dilution bioassays. Experimental bottles enriched with resources and controls without enrichment (in triplicate) were incubated in situ for 48 h at collection depth. Results showed that C, N and P in combination significantly (at 5% level) stimulated bacterial growth rate. Bioassays with single resource additions showed P as main nutrient limiting bacterial growth comparing with C and N, implying that rainfall received in the catchment might convey adequate resources causing increased P deficiency for bacterial growth in Himalayan foot hill Lake Phewa.