Salt Lake Environment Research Articles

Salt-adapted moulds and yeasts: Potentials in industrial and environmental biotechnology

Abstract Salt-adapted fungi are well-known inhabitants of hypersaline environments such as saltern, brine, estuary, salt lake, and marine environment, characterized by a high salt tolerance. Halophilic and halotolerant fungi have evolved with various special adaptive mechanisms, enable them to survive in elevated salt conditions. In most cases, these organisms are able to adapt extreme environmental conditions of temperature, pH, and ultraviolet radiation. Due to their successful thrive in high saline condition and combination of other harsh conditions, have been considered to be a paramount in the search for novel strains with industrial and environment biotechnological potentials. Salt adapted fungi possess a remarkable genetic reservoir, will culminate in the development of robust industrial organisms. Thus, in this review an approach has been made to concisely elucidate the biodiversity and eco-physiology of salt-adapted/salt-tolerant yeasts and filamentous fungi, their mechanism of adaptation in the hypersaline environment, as well as their biotechnological potentials.

Comparison of Extremely Halophilic Archaea Isolated from Three Salt Lakes in China

There’re many kinds of extremely halophilic archaea living in salt lakes all over the world and the ecological environment of lakes can affect their archaeal species. To illustrate the relationships between archaeal species and salt lake environment, we isolated and cultured 25 extremely halophilic archaeal strains from three salt lakes in China (Gou Salt Lake, Huama Salt Lake and Yuncheng Salt Lake). According to the 16S rRNA gene sequence analysis and the construction of Neighbor-Joining phylogenetic trees, the isolates were closely related to each other. The most dominant archaea was genus halorubrum (88.0%), followed by genus haloarcula (8.0%) and a small amount of genus halovivax (4.0%). Yuncheng salt lake (YC) had the most abundant number of species. Through the study of the basic information of the three sampling sites, we considered the species of extremely halophilic archaea were related to their living natural conditions of brine. Warm weather and high mineralization degree are likely to be functional components to enrich the species diversity.

Microbial community structure and diversity within hypersaline Keke Salt Lake environments.

Keke Salt Lake is located in the Qaidamu Basin of China. It is a unique magnesium sulfate-subtype hypersaline lake that exhibits a halite domain ecosystem, yet its microbial diversity has remained unstudied. Here, the microbial community structure and diversity was investigated via high-throughput sequencing of the V3-V5 regions of 16S rRNA genes. A high diversity of operational taxonomic units was detected for Bacteria and Archaea (734 and 747, respectively), comprising 21 phyla, 43 classes, and 201 genera of Bacteria and 4 phyla, 4 classes, and 39 genera of Archaea. Salt-saturated samples were dominated by the bacterial genera Bacillus (51.52%-58.35% relative abundance), Lactococcus (9.52%-10.51%), and Oceanobacillus (8.82%-9.88%) within the Firmicutes phylum (74.81%-80.99%), contrasting with other hypersaline lakes. The dominant Archaea belonged to the Halobacteriaceae family, and in particular, the genera (with an abundance of >10% of communities) Halonotius, Halorubellus, Halapricum, Halorubrum, and Natronomonas. Additionally, we report the presence of Nanohaloarchaeota and Woesearchaeota in Qinghai-Tibet Plateau lakes, which has not been previously documented. Total salinity (especially Mg2+, Cl-, Na+, and K+) mostly correlated with taxonomic distribution across samples. These results expand our understanding of microbial resource utilization within hypersaline lakes and the potential adaptations of dominant microorganisms that allow them to inhabit such environments.

Insights of Phage-Host Interaction in Hypersaline Ecosystem through Metagenomics Analyses.

Bacteriophages, as the most abundant biological entities on Earth, place significant predation pressure on their hosts. This pressure plays a critical role in the evolution, diversity, and abundance of bacteria. In addition, phages modulate the genetic diversity of prokaryotic communities through the transfer of auxiliary metabolic genes. Various studies have been conducted in diverse ecosystems to understand phage-host interactions and their effects on prokaryote metabolism and community composition. However, hypersaline environments remain among the least studied ecosystems and the interaction between the phages and prokaryotes in these habitats is poorly understood. This study begins to fill this knowledge gap by analyzing bacteriophage-host interactions in the Great Salt Lake, the largest prehistoric hypersaline lake in the Western Hemisphere. Our metagenomics analyses allowed us to comprehensively identify the bacterial and phage communities with Proteobacteria, Firmicutes, and Bacteroidetes as the most dominant bacterial species and Siphoviridae, Myoviridae, and Podoviridae as the most dominant viral families found in the metagenomic sequences. We also characterized interactions between the phage and prokaryotic communities of Great Salt Lake and determined how these interactions possibly influence the community diversity, structure, and biogeochemical cycles. In addition, presence of prophages and their interaction with the prokaryotic host was studied and showed the possibility of prophage induction and subsequent infection of prokaryotic community present in the Great Salt Lake environment under different environmental stress factors. We found that carbon cycle was the most susceptible nutrient cycling pathways to prophage induction in the presence of environmental stresses. This study gives an enhanced snapshot of phage and prokaryote abundance and diversity as well as their interactions in a hypersaline complex ecosystem, which can pave the way for further research studies.

Biogenic processes or terrigenous inputs? Permanent water bodies of the Northern Ponds in the Lake MacLeod basin of Western Australia

The saline wetlands of the Northern Ponds, Lake MacLeod, contravene general classifications for salt lakes because, despite enduring high levels of evaporation, they contain permanently inundated ponds that are continually supplied with seawater by a seepage face from the Indian Ocean. The present study investigated the physical, sediment and chemical characteristics of these ponds, using sonar, flow-rate measurements, microscopy and inductively coupled plasma–mass spectrometry to understand the role of biogenic and terrigenous inputs on the benthic habitats. The chemical composition of the water bodies did not differ significantly from the seawater feedstock, which facilitates biogenic sediment accumulation. The largest permanent water body differs from the other ponds in physical and chemical structure, in that, possibly because of its size, it is dominated by terrigenous inputs, which result in higher nutrient concentrations and non-biogenic sediments. The Northern Ponds represent a system where the hydrology permits the establishment of permanent wetlands in an arid environment. Because of the constant supply of seawater, the ponds have a blend of habitat characteristics from marine and other inland salt-lake environments. The present study showed that a ‘marine-like’ state can override more typical characteristics of inland water bodies where discharge rates are high and water-residence times are low.

How salt lakes affect atmospheric new particle formation: A case study in Western Australia

New particle formation was studied above salt lakes in-situ using a mobile aerosol chamber set up above the salt crust and organic-enriched layers of seven different salt lakes in Western Australia. This unique setup made it possible to explore the influence of salt lake emissions on atmospheric new particle formation, and to identify interactions of aqueous-phase and gas-phase chemistry. New particle formation was typically observed at enhanced air temperatures and enhanced solar irradiance. Volatile organic compounds were released from the salt lake surfaces, probably from a soil layer enriched in organic compounds from decomposed leaf litter, and accumulated in the chamber air. After oxidation of these organic precursor gases, the reaction products contributed to new particle formation with observed growth rates from 2.7 to 25.4nmh−1. The presence of ferrous and ferric iron and a drop of pH values in the salt lake water just before new particle formation events indicated that organic compounds were also oxidized in the aqueous phase, affecting the new particle formation process in the atmosphere. The contribution of aqueous-phase chemistry to new particle formation is assumed, as a mixture of hundreds of oxidized organic compounds was characterized with several analytical techniques. This chemically diverse composition of the organic aerosol fraction contained sulfur- and nitrogen-containing organic compounds, and halogenated organic compounds. Coarse mode particles were analyzed using electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Ultra-high resolution mass spectrometry was applied to analyze filter samples. A targeted mass spectral analysis revealed the formation of organosulfates from monoterpene precursors and two known tracers for secondary organic aerosol formation from atmospheric oxidation of 1,8-cineole, which indicates that a complex interplay of aqueous-phase and gas-phase oxidation of monoterpenes contributes to new particle formation in the investigated salt lake environment.

Effect of manganese oxide minerals and complexes on gold mobilization and speciation

(Bio)geochemical processes mediate the dispersion and re-concentration of gold (Au) in Earth surface environments. The fundamental mechanisms underlying the mobilization of Au in surface environments and the chemical speciation of mobile Au remain largely unexplored. For more than half a century authors have argued that highly reactive manganese (Mn) oxides are involved in oxidizing, and hence mobilizing, Au in waters, soils and sediments. However, no systematic study has assessed the mechanisms of Au oxidation under conditions occurring in natural environments. Therefore, this paper explores the links between Mn-oxides and the oxidation/mobilization of Au under acidic to circum-neutral conditions. Using a newly developed high performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS) method, a range of Au(I/III)-complexes occurring in aqueous solution were directly quantified. We show that the oxidation of Au(I) to Au(III) with birnessite occurs in acidic environments, and that the rapid release of Au(III) sorbed (on Mn- or Fe-minerals) via influx of neutral waters transfers Au(III) into solution, making it mobile and transportable. This provides a viable pathway for explaining the occurrence of mobile Au(III)-complexes under neutral to alkaline conditions, as was reported from a Western Australian salt lake environment. In addition, we show that the [(bpy)2MnIII(μ-O)2MnIV(bpy)2]3− complex (bpy=2,2′-bipyridyl), a useful model compound for the interaction of Au with bioorganic Mn in natural systems, mediates the formation of soluble Au(III)-complexes from metallic Au and from Au(I)-complexes under oxic and anoxic conditions. In conclusion, this study shows that reactive Mn-oxide minerals are important drivers of Au mobilization, and further suggests that natural organometallic compounds play an important role for the mobilization of Au in Earth surface environments.

Thermolytic degradation of methylmethionine and implications for its role in DMS and MeCl formation in hypersaline environments

Environmental context Methyl chloride and dimethyl sulfide are important atmospheric trace gases, but their biogeochemical contributions to the atmosphere are not fully understood. The amino acid derivative methyl methionine has been hypothesised to be a precursor of these two atmospheric gases, especially in drying salt-lake environments. We found methyl chloride and dimethyl sulfide in salt crystals and soil samples of hypersaline lakes, suggesting that a thermal decay of methyl methionine could be one of the formation mechanisms responsible. Abstract Volatile organic halocarbons (VOXs) and volatile organosulfur compounds (VOSCs) play an important role in the chemical processes of the lower atmosphere. However, biogeochemical release mechanisms from terrestrial environments are complex and the current knowledge of the origin and fluxes of these compounds is incomplete. This study presents data from worldwide sampling campaigns to hypersaline salt lakes to investigate terrestrial sources for atmospheric VOXs and VOSCs. The hypothesis was tested if methionine or methylmethionine could potentially serve as a precursor for methyl chloride and dimethyl sulfide formation in salt-lake environments. Next to methyl chloride, emissions from hypersaline soil samples incubated in headspace vials showed an array of VOSCs including dimethylsulfide and dimethyldisulfide. Additionally, methyl chloride and dimethyl sulfide were released from fluid inclusions of halite crystals after grinding and purge-and-trap headspace gas chromatography–mass spectrometry analysis. An abiotic mechanism for their formation is conceivable owing to the fast response of emission on heating freeze-dried samples at 40°C. Furthermore, the compounds trapped in fluid inclusions of halite crystals correspond to those compounds originally formed in the immediately subjacent soils. Based on the thermolytic degradation of methylmethionine, the activation energies for methyl chloride and dimethyl sulfide are calculated from their Arrhenius plots. Additionally, structurally related substances were analysed and a degradation mechanism is postulated. Results indicate that thermolytic processes could play an important role in salt-lake environments on desiccation.

Atmospheric Corrosion Behavior of Pre-strained Aluminum Alloys LY12 and LC4 in Salt Lake Environment in Western China

Atmospheric corrosion behavior of U-bended aluminum alloy plates of LY12 and LC4with/without Al cladding was investigated by field exposure in salt lake environment in Western China for 2 a. Then their surface and cross-sectional morphology was examined by metalloscope and SEM. The results showed that the corrosion behavior of the Al clad alloys LY12 and LC4 was mainly pitting corrosion within the cladding and no pits penertrating the cladding could be observed after 2 a exposure. For the bare alloys LY12 and LC4, severe stress corrosion cracking(SCC) was observed in the test. Both tensile- and compressive- stress could lead to SCC in for LY12, while only tensile stress could induce SCC for LC4 during the exposure. Exfoliation corrosion(EFC) of LY12 and LC4 occurred under compressive stress but not under tensile stress.

Isolation and Genetic Characterization of Phenol-Degradating Bacterium from a Salt Lake in Inner Mongolia

Salt lake environments are economically and ecologically important issues. Like any other ecosystems in the world, salt lake ecosystems are facing various kinds of pollutions. However, little information is available on the biodegradation of organic pollutants by halophilic microorganisms in such environments. In the present work we isolated a strain of phenol-degradating bacteria from a salt lake in Inner Mongolia. Sequence of 16S rRNA suggested that the strain belong toPropionibacteriumgenus. The strain can grow with phenol as a sole carbon source under 10% (w/v) salt concentration. PCR amplifications with the primers for multicomponent phenol hydroxylase or catechol 1, 2 dioxygenase gene were applied to genome DNA of the strain, suggesting that phenol might be transformed to catechol by multicomponent phenol hydroxylase and further degradated through ortho-ring cleavage pathway. When the primers for catechol 1, 2 dioxygenase were applied to the DNA obtained from the lake water, at least two types of catechol 1, 2 dioxygenase genes sequences were obtained, suggesting the presence of the bacteria with diverse aromatic compound-degradating genes.

Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lake environment in Western China

Atmospheric corrosion of aluminium alloy 2024-T3 exposed to salt lakes environment for 6years was investigated by weight loss, analysis of morphology and corrosion products. The results showed an increase in the mass loss with a high rate in the first 2years, and tended to stabilise over time. A main crystalline component of corrosion products, [Mg1-xAlx(OH)2]x+Clx-·mH2O, was determined by XRD. Besides pitting and intergranular corrosion, stress corrosion cracks (SCC) were observed in all test periods. According to the analysis, causes for the corrosion behaviour were attributed to the deposition of salts particles (mainly MgCl2·6H2O) and the arid climate.

Resources and eco-environmental protection of salt lakes in China

The Chinese salt lake mega-region is controlled by an arid and semi-arid climate, and modern salt lakes are mainly distributed within areas with mean annual precipitation <500 mm. According to their geomorphological features, structural conditions, and material composition, salt lakes in China can be broadly divided into four regions. The degrees of exploitation and utilization of these salt lakes differ because these four regions have experienced different climatic changes and structural activities and have had their own characteristics of salt lake evolution since the beginning of the Quaternary. The salt lakes in these regions have different scales, economic value, and technical conditions for traffic. Among others, Jarantai (Jartai) Salt Lake and Yuncheng Salt Lake are better in terms of comprehensive utilization and environmental protection, and the potash salt lakes represented by Qarhan are most important in terms of exploitation. At present, there exist many environmental problems in the salt lake regions of China, especially in remote, small and medium-sized basins, where abusive or wasteful mining, low recovery, and mining of a single saline mineral have caused impoverishment and large quantities of byproducts. Furthermore, climatic environmental factors can also cause significant changes of salt lake environment. Since 1987, against the background of global warming, the climate in the northwest salt lake region has turned warm and wet, and lakes have exhibited a tendency for expansion and rise, whereas in the east of the region, the climate has remained in a warm dry stage, lake levels have dropped, and salt lakes have become desertified. With the implementation of the strategy of building an environmentally friendly society in China, increasing attention is being paid to eco-environmental protection. It is suggested that experience and advanced techniques in terms of comprehensive utilization, overall development, and environmental protection of salt lakes at home and abroad be further developed to strengthen observation and monitoring of environmental changes of salt lakes and build an environmentally friendly, great salt lake industry.

Sulfate Attack on Concrete in an Inland Salt Lake Environment

Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe ()-Huaiyang () high-voltage electricity transmission line that is 20 years old and situated in an inland salt lake environment in North China. To analyze the deterioration mechanism that led to this condition, field investigations were carried out and several tests were conducted on the soil and the affected concrete, including XRD (X-ray diffraction), electric probe analysis, and chemical analysis. The results show that the concentration of sulfates is very high (0.39% wt. – 0.67% wt.) in both the surrounding soil and the material around the coarse aggregates inside the concrete. Hence, sulfate attack could be one of the main causes of concrete deterioration. The percentage of sulfates in the surface layer of the concrete was higher than that in the inner layers of the concrete. The sulfates penetrate into the concrete and react with the hydrates of cement to form ettringite (AFt), which leads to increase in the volume and cracking of the concrete.

Later Pleistocene/Holocene climate conditions of Qinghai–Xizhang Plateau (Tibet) based on carbon and oxygen stable isotopes of Zabuye Lake sediments

We present a time series of carbon and oxygen stable isotope records of the last 30 000 14C years throughout the last glacial–postglacial cycle from western Qinghai–Xizhang (Tibet) Plateau. A 20-m core drilled in the south basin of Zabuye Salt Lake was analyzed for inorganic and organic carbon and total sulfur contents, δ13C and δ18O values of carbonates. Our results indicate that climatic changes have led to a drastic negative shift of stable isotope ratios at the transition between the Last Full Glacial and the postglacial phase during Later Pleistocene times (∼16.2 kyr BP), and a rapid positive shift at the transition from Pleistocene to Holocene (∼10.6 kyr BP). The first shift is marked by the drop of δ18Ocarb values of about 10‰ (from +2 to −8‰) and δ13Ccarb values of about 3‰ (from 5 to 2‰). The second shift which occurred at the transition from Pleistocene to Holocene was of similar magnitude but in the opposite direction. Isotope data, combined with total organic and inorganic carbon contents and the lithological composition of the core, suggest this lake was an alluvial pre-lake environment prior to ca. 28 14C kyr BP. During ca. 28–16.2 14C kyr BP, Zabuye Lake was likely a moderately deep lake with limited outflow. The cool and arid glacial climate led the lake level to drop drastically. Extended residence time overwhelmed the lower temperature and caused a steady increase of δ13Ccarb and δ18Ocarb values and total inorganic carbon content in the sediments. During ca. 16.2–10.6 14C kyr BP, this lake probably overflowed and received abundant recharge from melting glaciers when the deglaciation was in its full speed. A spike of markedly enhanced δ13Ccarb and δ18Ocarb is seen at ∼11.5 kyr BP, probably due to the isotopic effects left behind by the short but severe Younger Dryas (YD) event. After ca. 10.6 14C kyr BP, Zabuye Lake probably closed its surface outflow, due to strong desiccation and drastic climate warming. The Early and Middle Holocene were characterized by unstable climatic conditions with alternating warmer/cooler episodes as indicated by the severe fluctuations of total organic carbon, δ13C and δ18O values. A hypersaline salt lake environment was finally formed at Zabuye after ∼5 14C kyr BP when the mirabilite and halite concentrations steadily increased and became the dominant minerals in the sediments. Severe imbalance of inflow/outflow resulted in the drastic increase of total sulfur, δ13Ccarb and δ18Ocarb values and dominance of halite in the lake since ca. 3.8 kyr BP to present.

Multi-element dispersion within salt-lake environments: case study of the buried Hannan South gold deposit, Western Australia

Prior to mining, the Hannan South deposit contained 0.26 Mt at 4.98 g t −1 Au confined within a weathered, highly saline water-saturated regolith beneath a salt lake. There was no surface expression, although the host rock sub-cropped at 3–4 m depth. The water table seasonally fluctuates between 0 and 10 m depth. The rock is a highly altered and structurally disrupted basalt, now a sulphidic epidote-rich unit. This unit is truncated at 80 m depth within sub-vertically interlayered Archaean felsic sedimentary and intermediate volcanic rocks. No fresh host rock is preserved. There is a sharp sub-horizontal iron redox front at 25–30 m depth between upper and lower saprolite. At this front, Eh conditions are sufficient to oxidize dissolved Fe 2+ from weathered Fe-bearing minerals in the lower saprolite, to Fe 3+ with the production of strong acid solutions (pH 0.5–2). Acid-enhanced weathering forms the upper saprolite as the front descends through the profile. As the pH increases, Fe 3+ precipitates as Fe oxides, mainly goethite, above the front. Primary Au containing 3–5 wt% Ag is hosted within pyrite and accessory sulphide minerals of As, Cu, Co, Pb, Bi, W and Zn in the saprock. The progressive oxidation of the sulphides has released soluble ore-associated elements, including Au as a thiosulphate complex (Au–Ag(S 2 O 3 ) 2 3− ). This complex is metastable and has precipitated fine-grained secondary Au containing 3 wt% Ag around pseudomorphs of the host sulphides. The other elements are widely dispersed but are largely confined to the host rock in the lower saprolite due to limited groundwater flux. Poorly defined acid sulphide and subtle Mn redox fronts within the lower saprolite have little influence on trace element dispersion. Silver is the most strongly depleted. In the upper saprolite, descent of the redox front over time has led to leaching of Au under acid, oxidizing conditions. Gold has probably dissolved as organic or chloride complexes at the front, dispersed laterally down-gradient and precipitated as pure crystals (99.9 wt% Au) in a sub-horizontal supergene enrichment blanket just above the front. Copper, Ag, Co, Pb and Zn are also strongly leached from the acidic saprolite above the iron redox front and are dispersed and depleted with increasing groundwater flux in the upper profile. In comparison, As, Sb, Bi, Mo and W, which form oxyanions, are relatively immobile and are preferentially retained in goethitic zones. These buried multi-element halos hosted by goethite provide near-surface geochemical exploration targets within otherwise barren upper saprolite.

Investigating the feeding behaviour of brine shrimps

Brine shrimps, Artemia franciscana, appeal to students of all ages and can be easily maintained and reared in a classroom or laboratory. In nature they live in salt lakes feeding on algae, either by filter feeding as they swim or by grazing on the bottom mud. The salt lake environment can be mimicked in a laboratory, and students can learn much from observing shrimps grazing. But what happens to their feeding behaviour if the substrate is above the bottom of the tank? Apparatus is described that enables students to observe shrimps feeding at different levels and to study some influences on their behaviour.

Modern pollen dynamics and surficial sedimentary processes at Lake Tyrrell, semi-arid northwestern Victoria, Australia

Salt (playa) lakes provide an opportunity to obtain long records of vegetational change from arid areas. This paper presents results of a study of modern pollen dynamics at Lake Tyrrell, a large salt lake in semi-arid northwestern Victoria, Australia. Results suggest that the lake receives an airborne pollen flux which broadly reflects the nature of the regional vegetation. Waterborne pollen and pollen carried to the lake by surface wash are of no significance to the overall pollen budget. Pollen are rapidly redistributed across the lake floor and preferentially deposited marginal to the salt crust. Implications of these processes for interpretation of fossil pollen in salt lake environments are discussed.

Monitoring sediment transport systems in a semiarid area using thematic mapper data

Thematic Mapper data, in the form of false color composites and change detection images, have been used to monitor and map four geomorphological process domains in southern Tunisia over a 4-year period. Hillslope, river channel, alluvial fan, and salt lake environments were examined using field surveys, laboratory analysis of sediment samples, and remotely sensed data. An assessment is made of the utility of Thematic Mapper data for geomorphological monitoring of these environments. The detection of large fluvial channels and circular ground water features (aioun) within one large playa have shown the value of using remotely sensed imagery for geomorphological mapping in such environments. As a result of this research it is shown that the traditional model of salt lake development based on the relative solubility of salts may need to be modified to take account of the influence of fluvial transport. Monitoring geomorphological changes in other process domains provided less satisfactory results; largely it is believed because of the almost complete absence of major rainfall events during the study period; however, geomorphological changes due to anthropogenic activity were successfully monitored.

Ooid Fabric and Fracture in the Great Salt Lake and the Geologic Record

ABSTRACT Great Salt Lake ooids consist of a nucleus grain coated by layers of aragonite nannograins and minor impurities. Most nannograins are elongate parallel to their c-axis and individual layers are composed of grains which are tangentially, normally (radially) or randomly oriented with respect to the ooid surface. This orientation may be determined petrographically or with a scanning electron microscope. Evidence from the Great Salt Lake and other ooid-forming environments that relates ooid-forming processes to ooid structure generally falls into three categories: 1) randomly oriented aragonite and organic influences; 2) tangentially oriented aragonite and the role of agitation; and 3) radially oriented aragonite and crystal growth. Living microorganisms play a destructive, not constructive role in ooid growth and are not present in most Great Salt Lake ooids. Organic matter in both marine and Great Salt Lake ooids may play an important role as an adhesive during cortex accretion. Although the general physical conditions of ooid formation are known, detailed knowledge of the mechanism of ooid growth is lacking. Few hypotheses account for the tangential orientation of nannograins in the ooid cortex and those that do evoke a modification of Sorby's snowball hypothesis. Some snowballing of Great Salt Lake ooids is indicated by clays in the ooids, which match the detrital clays in the lake. Radial grains in Great Salt Lake ooids range in length from 1 to 100 microns. They display petrographic relationships that are ambiguous relative to their origin, but a magnesium-rich zone around large radial grains suggests these result from an early reorganization of a precursory material. Large radial grains are interpreted as secondary features, albeit syndepositional. These grains are the result of recrystallization only if the postulated earlier precipitate was calcium carbonate. Ooids with large-scale radial fabric, like those of the Great Salt Lake, are characteristic of hypersaline and freshwater environments. The radial fabric renders Great Salt Lake ooids weaker than tangential Bahamian-type ooids of the same size and shape. This produces broken ooids in Great Salt Lake ooid sands. Syndepositionally broken ooids are associated with several evaporitic ancient oolites but are very rare in normal marine oolites. Broken ooids are considered significant indicators of unusual salinity if they comprise more than 1% of the grains in an oolite.