Phytoplankton primary production, chlorophyll‐a and nutrient concentrations in the water column of mountainous Lake Phewa, Nepal

Abstract

The seasonal patterns of phytoplankton primary production, chlorophyll-a concentration, cell number and several other limnological variables in Lake Phewa, located in the active monsoon zone in Central Himalaya, Nepal, were studied for a year beginning in April 2001. During the study period, the gross primary production and chlorophyll-a concentrations were relatively low during the monsoon season. The phytoplankton cell number, represented by 24 genera, also fluctuated seasonally, but tended to increase in the pre-and post-monsoon period. These results suggest that the monsoon plays a crucial role in the primary production and phytoplankton dynamics for Lake Phewa. Among the phytoplankton species, Microcystis aeruginosa, a representative species for eutrophic lakes, was the dominant phytoplankton. At the same time, however, it is clear that the lake is not yet heavily eutrophic. The present study suggests that the exchange of lake water during the monsoon season contributes to maintaining the health of the lake against further degradation. Nevertheless, the silt carried in the monsoon rain run-off from the lake's catchment area suggests increasingly serious degradation problems for this small mountainous lake.

Spatial and seasonal variations in phytoplankton community structure in alkaline–saline Lake Nakuru, Kenya

“…Furthermore, their standing crops exhibit variations that depend on several factors, including: (i) the supply of major nutrients (mainly phosphorus and nitrogen); (ii) light availability; (iii) grazing by zooplankton; (iv) water mixing regimes; and (v) basin morphometry (Reynolds et al . 2001; Gurung et al . 2006).…”

Influência da sazonalidade em lagoas de estabilização

“…Segundo Gurung et al (2006), durante os períodos de intensa precipitação o TDH é menor, e consequentemente, ha maior escoamento da água e aumento na diluição dos nutrientes, como é percebível nos resultados apresentados. Entretanto, no módulo A o TDH foi maior no período chuvoso devido ao aumento da profundidade.…”

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

“…2005; Wetzel & Tuchman 2005). Lake Phewa has a small volume relative to its catchment area, and the monsoon‐dominated climate can deliver up to 4846 mm of rainfall per year (Paudel & Thapa 2001; Gurung et al. 2006), causing lake water to be exchanged many times during summer (Ferro 1981/1982; Lohman et al.…”

“…During the monsoon, phytoplankton in Lake Phewa can be reduced by silt‐laden inflows that dilute lake water and reduce available light (Davis et al. 1998; Gurung et al. 2006).…”