Lakes hypersaline

In order to be successful in finding a biocatalyst that is adapted to the required process conditions, one could sample at a site where similar conditions apply. As such sampling sites with low biodiversity, but high selection pressure such as hypersaline ponds, acidic or alkaline lakes, deserts, hot springs or sites polluted with chemicals are particularly useful. 

Fulvic acid was isolated in Big Soda Lake above and below the chem-ocline, which occurs at 34-m depth. Water near the lake surface has moderate salinity and is oxygenated, whereas water below the chemocline is hypersaline and anoxic (17). In spite of these environmental differences the chemical character of the fulvic acid from above or below the chemocline did not vary, as determined by elemental analyses and NMR spectrometry. 

Not all measures of salinity convey the same degree of salinity. For example, compare Orca Basin, the Great Salt Lake, the Dead Sea, and Basque Lake (Table 5.1). All four of these waters contain about the same salinity % [25.1-26.4% salt (wt/wt)]. Note, however, that Basque Lake has a much more favorable (for life) aw (0.919) compared with Orca Basin (0.774), Great Salt Lake (0.776), and, especially, the Dead Sea (0.690). The impact of salts on life depends on the anions and cations and their charges and molecular weight. Bacterial sulfate reduction occurs with salt concentrations up to 24% (Oren 1988), but chloride salt solutions at such concentrations deals much more harshly with life. Only the most halophilic organisms can live in the Dead Sea (Table 4.2). The Dead Sea was called dead because it was only in 1936 that life forms (e.g., bacteria, algae, yeast) were first isolated from this hypersaline water (Ventosa et al. 1999). 

The other major reactant in Equation 1 is sulfate (SO42 ). Sulfate concentrations are highly variable in lake waters, from 3 x 10 5 mol/L in soft-water lakes in crystalline-rock drainage basins to 1.6 mol/L in hypersaline lakes (2.). In productive, freshwater lakes, sulfate reduction typically goes nearly to completion (5.). As sulfate concentrations increase, amounts of organic matter eventually become insufficient for complete sulfate reduction to occur. This is the case in "normal" marine sediment where a linear relation between total reduced sulfur and organic-carbon concentrations is observed. Sea-water sulfate concentration is 0.028 mol/L and the ratio of total reduced sulfur to organic-carbon concentrations (often referred to as S/C) in marine sediment is 0.33 ( ). ... 

There are, however, some problems in the direct application of such a ratio. First, relative high abundances of A7-sterols have been reported in Lake Kinneret, a normal marine salinity environment (39). Hence, A -sterols are obviously not restricted to organisms living in hypersaline environments. The relative abundance of A7- (and a8 14)-) sterols in hypersaline environments may be due to the absence of grazing zooplankton in these environments. In normal marine salinity environments A7- and A8(14)-sterols are selectively metabolised in the guts of zooplankton resulting in a selective preservation of A5-sterols in zooplankton fecal pellets, which are transported rapidly to the sediment (40,41). 

Highly saline environments are not only directly associated with present seas and oceans, but also with former seas which have led to salt deposition. These are generally hypersaline environments and may include salt lakes such as the Dead Sea, where salt concentrations may reach 4-5 M NaCl (Buchalo et al., 1998), together with salt pans and flats. In many cases, these are dominated by other ions such as potassium, magnesium, calcium, sulphate, carbonate and bicarbonate, as well as sodium and chloride. Flowers et al. (1986) estimated that about 10% of global land area was occupied by soils too saline for the growth of non-halophiles. 

The Halobacteriaceae, commonly referred to as the halobacteria, are a family of extremely halophilic archaebacteria [113]. As in other archaebacteria, their membranes contain ether-linked lipids. The primary lipids present are diphytanyl phospholipids [113]. Their cell walls are also unique in structure and lack muramic acid. There are several species of halobacteria that vary considerably in their physiological characteristics. The halobacteria are unicellular rods or cocci. More recently flat, square and box-shaped cells have been described. Halobacteria are found growing in salterns or natural salt lakes and on the surface of salted fish. They often form dense planktonic blooms and can form massive accumulations on solid substrates. They may be involved in mat communities in hypersaline environments. 

Kelts K. and Shahrabi M. (1986) Holocene sedimentology of hypersaline Lake Urmia, Northwestern Iran. Paleogeogr. Paleoclimatol. Paleoecol. 54, 105—130. 

Proportions of As(lll) and As(V) are particularly variable in stratified lakes with seasonally variable redox gradients (Kuhn and Sigg, 1993). In the stratified, hypersaline, hyperalkaline Mono Lake (California, USA), As(V) predominates in the upper oxic layer and As(lll) in the reducing layer (Maest et al., 1992 Oremland et al., 2000). Oremland et al. (2000) measured in situ rates of dissimilatory As(V) reduction in the lake and found that this could potentially mineralize 8-14% of the annual pelagic primary productivity during meromixis, a significant amount for a trace element, and —1/3 of the amount of sulfate reduction. Such reduction does not occur in the presence of NO3. In fact, NO3 leads to the rapid, microbial re-oxidation of As(III) to As(V) (Hoeft et al, 2002). Iron(III) acts similarly. 

Dupraz, C., Visscher, P., Baumgartner L.K. Reid, P.R. (2004) Microbe-mineral interactions early carbonate precipitation in a hypersaline lake (Eleuthera Island, Bahamas). Sedimentology 41, 745-765. 

Torfstein, A., Gavrieli, I. Stein, M. (2005) The sources and evolution of sulfur in the hypersaline Lake Lisan (paleo-Dead Sea). Earth and Planetary Science Letters 236, 61-77. 

Alunite-jarosite minerals (and the other secondary sulfates) form, in part, because of evaporative concentration of pore and capillary waters in pyritic materials, and also at depth in saturated tailings (Dubrovsky et al. 1985). They are found in soils beneath acid sulfate evaporation ponds (Peterson et al. 1983), and are also precipitated directly from acid mine waters (cf. Filipek et al. 1987 Alpers et al. 1989). The alunite-jarosite mineral group also occurs in the weathered zones on top of metal sulhde deposits (Scott 1987) and in the sediments of acid hypersaline lakes (Alpers et al. 1992). 

Alpers, C. N., R. O. Rye, D. K. Nordstrom, L. D. White, and B-S. King. 1992. Chemical, crystallographic and stable isotopic properties of alunite and jarosite from acid-hypersaline Australian lakes. Chem. Geol. 96 203-26. 

Brandt KK, Vester F, Jensen AN, Ingvorsen K (2001) Sulfate reduction dynamics and enumeration of sulfate-reducing bacteria in hypersaline sediments of the Great Salt Lake (Utah, USA). Microbial Ecol 41 1-11... 

Anoxic water samples, because they contain little in the way of particles, are far easier than aquifer materials to develop radioassays for the measurement of arsenate reduction. Arsenic speciation quantitatively changes from arsenate to arsenite with vertical transition from the surface oxic waters to the anoxic bottom depths of stratified lakes and fjords (55,56). This also occurs in Mono Lake, California (57), a transiently meromictic, alkaline (pH = 9.8), and hypersaline (salinity = 70-90 g/L) soda lake located in eastern California (Fig. 11). The combined effects of hydrothermal sources coupled with evaporative concentration have resulted in exceptionally high ( 200 fiM) dissolved arsenate concentrations in its surface waters. Haloalkaliphilic arsenate-respiring bacteria have been isolated from the lake sediments (26), and sulfate reduction, achieved with... 

R Ciulla, MR Diaz, BF Taylor, MF Roberts. Organic osmolytes in aerobic bacteria from Mono Lake, an alkaline, moderately hypersaline environment. Appl Environ Microbiol 63 220-226, 1997. 

The water in Waldsea Lake is saline to hypersaline, with an average salinity of the mixolimnion of 25ppt TDS and 70ppt TDS for the monimolimnion. Both water masses are alkaline, strongly dominated by Na" ", and S04 , and satnrated or supersat-... 

One of the most important and comprehensive summaries of the mineralogy of lake sediments is that of Jones Bowser (1978). Although this overview concentrates mainly on the deposits of freshwater lakes, nonetheless, it provides all the essential background information and fundamental concepts necessary for neophytes as well as seasoned veteran paleolimnologists. Smoot Lowenstein (1991), Warren (1989), Sonnenfeld Perthuisot (1989), Sonnenfeld (1984), and Reeves (1968) offer complementary overviews of minerals in saline and hypersaline lacustrine deposits. 

Eugster, H. P., 1980. Lake Magadi, Kenya, and its precursors. In Nissenbaum, A. (ed.) Hypersaline Brines and Evaporitic Environments (Developments in Sedimentology 28). Elsevier, Amsterdam 195-232. 

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