A holomictic lake where rain water is the source of mixing and temperature change throughout the year
English: Title: Bulletin of the British Museum (Natural History) Zoology Identifier: bulletinofbritis5556farn (find matches) Year: 1989-90 (1980s) Authors: Farn, Alexander E Subjects: Publisher: London : Butterworths Contributing Library: Natural History Museum Library, London Digitizing Sponsor: Natural History Museum Library, London View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: MONGOLIAN FISHES 181 Text Appearing After Image: Fig. 6 Principal collecting locality Herelen Gol, 60 km downstream of bridge in Kentei Aimak, western bank. (Above opposite) Willow shoots along side channel, (Below opposite) main river in spate and (Above) isolated pond in flood plain. Nuur is shown by the conductivity readings given below (p. 187). In drying pools an evaporate is produced which can be Table 1 Element concentrations (ug/g fresh weight) in salt samples from two sites around shore of isolated water body off Boon Tsagaan Nuur. Element Dist.H.O Al B Ca Cd Co Cr Cu Fe K Mg Mn Na Ni P Pb Si Zn Mo Sr Ba Sample 1 Sample 2 .0234 .0568 .0225 .0062 1.2978 9.9068 .0209 41.4791 1.5461 .0027 .0029 .0021 .0019 .0032 .0033 .0023 .0374 .0171 .0901 .0109 .0151 .0138 .0056 .0000 1.1680 10.1220 157.9320 .0087 62.3513 29.2913 .0004 .0032 .0019 .1881 768.9119 786.2119 .0471 .0441 .0294 .0585 .7424 .3820 .0448 .0038 .0000 .0073 .2946 .1956 .0152 .0116 .0070 .0261 .1197 .4533 .0000 2.2820 .6441 .0012 .0097 .0213 Elemental compositions were determined with an ICAP (inductively coupled argon plasma) spectrophotometer, using dilutions of atomic absorption stocks for standards. several centimetres thick (Fig. 8), it supports a dense growth of salt tolerant Salicornia. Analyses of the evaporate revealed, not unexpectedly, a high concentration of calcium, magnesium, sodium and potassium; the concentrations of these and other elements in samples from two sites are summarised in Table 1. The high levels of these elements may be directly related to intense photosynthesis occurring in the lake (Goldman & Home, 1983), the geological composition of its watershed and the absence of an outlet which will cause the lake to accumulate ions even if it is not contracting. Water clarity was low during August (see Secchi Disc readings given below p. 187). This is due to a massive algal and zooplankton bloom (autochthonous production). No macrophytes were observed along the wave washed littoral zone or even further offshore. The water temperature of this holomictic lake was rela- tively high (see below) but dramatically dropped after a three day storm produced thorough mixing of the lake waters, which were otherwise prone to temporary thermal stratifica- tion. A massive development of zooplankton occurs in Boon Tsagaan Nuur during July and August (pers. obs. and Dulma, 1979: 728 gave average biomass as 2.1 g/m3). The sandy substrate supports a rich fauna of zooplankton including rotifers, larval stoneflies (Plecoptera), dragonflies (Anisoptera) and caddis flies (Trichoptera). Dulma (1979) classified the holo- and dimictic water bodies of the Gobi Valley as oligotrophic lakes. The productivity of saline lakes is often considered to be high (Goldman & Home, 1983: 382), based on a few but nevertheless abundant species. The massive plankton bloom obtained during August, together with the high yield of fishes, suggests greater eutro- phication than normally associated with oligotrophic systems. However, the sudden peak in productivity is short lived and must dramatically drop off to a much lower level during the Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.