First results on bathymetry and limnology of high-altitude lakes in the Gokyo Valley, Sagarmatha (Everest) National Park, Nepal

Abstract

The aim of this study was to investigate for the first time the morphology, physical and chemical characteristics of three high-altitude lakes in the Gokyo Valley, Everest National Park, Nepal. The moraine-dammed glacial lakes were studied for three seasons to create baseline data. The second, third, and fourth lakes in the Gokyo Valley are deeper than previously assumed. The vertical profiles of temperature and dissolved oxygen indicated that the thermocline zone varied between 10 and 20 m below the surface during the post-monsoon season. Although most of the analyzed metal concentrations were below the level recommended by the WHO for safe drinking water, lead (Pb) and cadmium (Cd) levels exceeded the limits in some of the samples. This has created great concern for human health. The probable route of these two pollutants is monsoon precipitation that carries industrial pollutants along its route. The sedimentation rates of Gokyo Lakes range from 0.069 to 0.089 cm per annum, which is within the limits of other high-altitude lakes. The present findings created a baseline database for some of the remote high-altitude lakes in Nepal that can be used for lake management and for assessing future changes in lake characteristics in the Himalayan region.

Selective predisposition of Nile tilapia (<i>Oreochromis niloticus</i> L.) to bacterial and parasitic infection- evidence from the crater lakes Babogaya and Hora-Arsedi, Ethiopia

“…The clinograde dissolved oxygen profile indicated oxygen depletion in greater depths, with saturation values constantly lower than 7% below 5 m in Hora and 8.5 % below 7 m in Babogaya (Figure 2), which is usual for eutrophic systems (Talling and Lemoalle, 1998). Such DO profiles have been also noted from other explosion crater lakes located in Cameroon, Uganda, Nepal and the United States (Melack, 1978;Kling, 1988;Sharma, 2012;Degefu et al, 2014a) and usually reflect extended stratification and high biological oxygen demand (BOD) by decomposition of sinking labile organic matter and respiration of organisms in deeper waters (Baxter et al, 1965;Löffler, 1972;Kebede and Belay, 1994;Haberyan et al, 1995). Consequently, sulfide content which was below the detection limit throughout the water column reached 8 mg L -1 at the bottom and at least during complete mixing, which lead to high biological oxygen demand during aerobic breakdown of reduced sulphides and nutrient upwelling which is not the case during this event.…”

Estimating the volume of Alpine glacial lakes

“…Some of these outliers are related to apparently unusual situations (compared to lakes upon which empirical relationships have been based). Specifically, Ngozumpa 4 is an ice-marginal moraine-dammed lake that is reported by Sharma et al (2012) to have a deep crevice at its base, giving it an unusually deep bed; Laguna Safuna Alta has a complex history of lake level change, involving modification by engineering works, and a suspected increase in moraine dam permeability as a consequence of an earthquake in 1970 (Hubbard et al, 2005), although it is not clear why it should be unusually deep. Quitacocha and Gelhaipuco lakes are both moraine-dammed and their volumes are underestimated by empirical relationships.…”

At the edge and on the top: molecular identification and ecology of Daphnia dentifera and D. longispina in high-altitude Asian lakes

“…longispina in lakes in the Himalayan Khumbu region was conducted using the statistical software R (R Development Core Team, 2012). Data from 20 lakes in this region were collected from several publications (Manca et al, 1994(Manca et al, , 1998Tartari et al, 1998;Lacoul & Freedman, 2005;Sommaruga & Casamayor, 2009;Sommaruga, 2010;Sharma et al, 2012). Variables collected were the presence/absence of the D. gr.…”

“…longispina in the harsh environment of the Himalaya range. Therefore, we collected and analyzed published data for lakes in the Khumbu region in northeastern Nepal (Manca et al, 1994(Manca et al, , 1998Tartari et al, 1998;Lacoul & Freedman, 2005;Sommaruga & Casamayor, 2009;Sommaruga, 2010;Sharma et al, 2012). These lakes are situated between 4,700 and 5,500 m a.s.l., are fishless, and are often inhabited by either nonpigmented D. gr.…”