Seasonal variations of metabolically active bacteria in a hypertrophic lake (Hartbeespoort Dam, South Africa)

✍ Scribed by Richard D. Robarts; Lynne M. Sephton

• Publisher: Springer
• Year: 1988
• Tongue: English
• Weight: 715 KB
• Volume: 160
• Category: Article
• ISSN: 1573-5141
• DOI: 10.1007/bf00015481

✦ Synopsis

The number of metabolically active bacteria was measured with nalidixic acid over two annual cycles at three depths in the epilimnion of hypertrophic Hartbeespoort Dam, South Africa. Concurrent measurements were made of water temperature, DOC, phytoplankton production of dissolved (EDOC) and particulate organic carbon, chlorophyll a and the uptake of glucose (Vma,,). The objective was to determine the dominant factors correlated to the number of metabolically active bacteria and the relationship between active bacterial numbers and heterotrophic activity.

The number of active bacteria was usually highest at the surface and ranged between 0.70 and 6.82 x 106 cells ml-' . The dominant factors correlated to the number of bacteria at the surface were water temperature (r = 0.65, n = 54, p<0.001), primary production (r = 0.53, n = 51, p < 0.001) and EDOC (r = 0.37, n = 45, p = 0.005). Surface Vm,, for glucose ranged between 0.11 and 4.0 ItgC 1-1 h -1 and was positively correlated to the number of active bacteria (r = 0.61, n = 53, p < 0.001). The specific activity index (10-12 gC cell-' h-l) varied between 80 and 2290 at the surface and was most strongly correlated to EDOC (r = 0.70, n = 48, p < 0.001). Relationships between active bacterial numbers, water temperature, phytoplankton activity and glucose uptake were also found at two additional depths within the epilimnion. These data suggest that bacterial populations in nutrient enriched lakes contain a large number of metabolically active cells with high individual activity as a result of enhanced phytoplankton growth.