Ephemeral Salt Lakes Research Articles

A GRASS GIS Scripting Framework for Monitoring Changes in the Ephemeral Salt Lakes of Chotts Melrhir and Merouane, Algeria

Automated classification of satellite images is a challenging task that enables the use of remote sensing data for environmental modeling of Earth’s landscapes. In this document, we implement a GRASS GIS-based framework for discriminating land cover types to identify changes in the endorheic basins of the ephemeral salt lakes Chott Melrhir and Chott Merouane, Algeria; we employ embedded algorithms for image processing. This study presents a dataset of the nine Landsat 8–9 OLI/TIRS satellite images obtained from the USGS for a 9-year period, from 2014 to 2022. The images were analyzed to detect changes in water levels in ephemeral lakes that experience temporal fluctuations; these lakes are dry most of the time and are fed with water during rainy periods. The unsupervised classification of images was performed using GRASS GIS algorithms through several modules: ‘i.cluster’ was used to generate image classes; ‘i.maxlik’ was used for classification using the maximal likelihood discriminant analysis, and auxiliary modules, such as ‘i.group’, ‘r.support’, ‘r.import’, etc., were used. This document includes technical descriptions of the scripts used for image processing with detailed comments on the functionalities of the GRASS GIS modules. The results include the identified variations in the ephemeral salt lakes within the Algerian part of the Sahara over a 9-year period (2014–2022), using a time series of Landsat OLI/TIRS multispectral images that were classified using GRASS GIS. The main strengths of the GRASS GIS framework are the high speed, accuracy, and effectiveness of the programming codes for image processing in environmental monitoring. The presented GitHub repository, which contains scripts used for the satellite image analysis, serves as a reference for the interpretation of remote sensing data for the environmental monitoring of arid and semi-arid areas of Africa.

Abiotic Perspectives?

I want to begin with an image of the vast ephemeral salt lake called Wilkinkarra/Lake Mackay, sitting in Pintupi Country in the remote Western Desert of Western Australia. This was a key site for my early research into ways to reimagine abiotic perspectives—to work with a ‘geologic’ using creative methods of site responsive artworks. I document these explorations of place as a means to explore my attempts and struggles to unpack complexities in the colonial settler spatiotemporal imaginary of the environment in the Anthropocene. My art practice is informed by the concept of uncritical “White Geology” as identified by the inhuman geographer, Kathryn Yusoff. In particular, the Eurocentric sociohistorical entanglements that help maintain a hierarchical outlook regarding the perception of abiotic matter. In September 2020, following my introduction to this approach at Ngā Tūtaki – Encounter/s, I completed three experimental site responsive artworks on a field trip to the Jack Hills in Wajarri Yamaji Country, in the Murchison district of Western Australia. This creative focus piece discusses secular pilgrimage and presents my durational performance art from that project.

Microbial Communities in Sediments From Four Mildly Acidic Ephemeral Salt Lakes in the Yilgarn Craton (Australia) - Terrestrial Analogs to Ancient Mars.

The Yilgarn Craton in Australia has a large number of naturally occurring shallow ephemeral lakes underlain by a dendritic system of paleodrainage channels. Processes like evaporation, flooding, erosion, as well as inflow of saline, often acidic and ion-rich groundwater contribute to the (dynamic) nature of the lakes and the composition of the sediments. The region has previously been described as an analog environment for early Mars due to its geological and geophysical similarities. Here, we investigated sediment samples of four lake environments aimed at getting a fundamental understanding of the native microbial communities and the mineralogical and (bio)chemical composition of the sediments they are associated with. The dominant mineral phases in the sediments were quartz, feldspars and amphiboles, while halite and gypsum were the only evaporites detected. Element analysis revealed a rich and complex image, in which silicon, iron, and aluminum were the dominant ions, but relative high concentrations of trace elements such as strontium, chromium, zirconium, and barium were also found. The concentrations of organic carbon, nitrogen, and phosphorus were generally low. 16S amplicon sequencing on the Illumina platform showed the presence of diverse microbial communities in all four lake environments. We found that most of the communities were dominated by extremely halophilic Archaea of the Halobacteriaceae family. The dynamic nature of these lakes appears to influence the biological, biochemical, and geological components of the ecosystem to a large effect. Inter- and intra-lake variations in the distributions of microbial communities were significant, and could only to a minor degree be explained by underlying environmental conditions. The communities are likely significantly influenced by small scale local effects caused by variations in geological settings and dynamic interactions caused by aeolian transport and flooding and evaporation events.

Dust storms and ephemeral lakes

In drylands, both dust storms and ephemeral salt lakes (playas) are common. Observations using remote sensing and ground studies have shown that these playas can be major sources of saline dust storms. Some basins have recently become desiccated as a result of water abstraction by humans, and these have become significant sources of dust. The timing and amounts of dust emissions depends on such factors as rainfall and drought events, the availability of sediment, and the nature of surface crust materials.

Edaphic factors controlling the distribution of inland halophytes in an ephemeral salt lake “Sabkha ecosystem” at North African semi-arid lands

This study aims to characterize soil properties and to investigate how these parameters, including soil salinity, are related to zonation and distributional patterns of halophytic plants occurring at edges of the Djendli Sabkha (northeastern Algeria). Soil samples were collected from four stations at Sabkha edges with seven samples for each station. Physicochemical soil parameters were analysed in each vegetation belt of halophytes. Relationships between soil traits were tested to determine spatial variation and their effects on vegetation cover of the principal halophyte species. The influence of pedological factors on the distribution and establishment of halophytes was considered using a redundancy analysis (RDA) and generalized linear models. Positive correlations were found between organic matter, carbon and nitrogen which were negatively correlated with electrical conductivity (EC), pH, gypsum, Na+ and Cl− concentrations. Sharp limits were found between halophyte communities even though there is a gradual change in the physicochemical environment along the gradient centre-to-edge of the Sabkha. RDA showed that edaphic variables that best explained the data were EC, pH, organic matter (OM), carbon and nitrogen contents, Na+ and Cl− concentrations. Sarcocornia fruticosa grew under higher soil salinity (EC=7.2–13.8dS/m) compared to Suaeda fruticosa and Suaeda vermiculata that afford moderate soil salinity, than Atriplex halimus established in soils with low EC values (5.5–7.3dS/m) but with high values of OM, carbon and nitrogen contents and low values of Na+, Cl− and pH. Sarcocornia fruticosa grew in soils characterized with high pH, Na+, Cl− values but relatively low in OM, carbon and nitrogen contents.

Salinity tolerances of three succulent halophytes (Tecticornia spp.) differentially distributed along a salinity gradient.

We evaluated tolerances to salinity (10-2000mM NaCl) in three halophytic succulent Tecticornia species that are differentially distributed along a salinity gradient at an ephemeral salt lake. The three species showed similar relative shoot and root growth rates at 10-1200mM NaCl; at 2000mM NaCl, T. indica subsp. bidens (Nees) K.A.Sheph and P.G.Wilson died, but T. medusa (K.A.Sheph and S.J.van Leeuwen) and T. auriculata (P.G.Wilson) K.A.Sheph and P.G.Wilson survived but showed highly diminished growth rates and were at incipient water stress. The mechanisms of salinity tolerance did not differ among the three species and involved the osmotic adjustment of succulent shoot tissues by the accumulation of Na+, Cl- and the compatible solute glycinebetaine, and the maintenance of high net K+ to Na+ selectivity to the shoot. Growth at extreme salinity was presumably limited by the capacity for vacuolar Na+ and Cl- uptake to provide sufficiently low tissue osmotic potentials for turgor-driven growth. Tissue sugar concentrations were not reduced at high salinity, suggesting that declines in growth would not have been caused by inadequate photosynthesis and substrate limitation compared with plants at low salinity. Equable salt tolerance among the three species up to 1200mM NaCl means that other factors are likely to contribute to species composition at sites with salinities below this level. The lower NaCl tolerance threshold for survival in T. indica suggests that this species would be competitively inferior to T. medusa and T. auriculata in extremely saline soils.

Tolerance of extreme salinity in two stem-succulent halophytes (Tecticornia species).

Communities of Tecticornia on the margins of ephemeral salt lakes in Australia often exhibit species zonation, such as at Hannan Lake (Western Australia) where Tecticornia indica subsp. bidens (Nees) K.A.Sheph. and Paul G.Wilson occupies the less saline dune habitat on lake margins and Tecticornia pergranulata (J.M.Black) K.A.Sheph. and Paul G.Wilson subsp. pergranulata occupies both the dunes and the more saline and moist lake playa. Here we tested the hypothesis that these two species differ in tolerance to extreme salinity. Plants were grown in drained sand cultures with treatments of 10-2000mM NaCl for 85 days. Both species were highly salt tolerant, maintaining growth at treatments of up to 2000mM NaCl, although the death of two replicates of T. indica at 2000mM NaCl suggests this salinity is close to the species tolerance limit. Both Tecticornia species maintained a favourable gradient in tissue water potential via osmotic adjustment as external salinity increased, also with reduced tissue water content at very high external salinity. Regulated accumulation of Na+ and Cl-, maintenance of net K+ to Na+ selectivity, high tissue concentrations of glycinebetaine and presumed cellular solute compartmentation, would have contributed to salt tolerance. The growth rate of T. pergranulata was 11-29% higher than T. indica suggesting, in addition to these moderate differences in salinity tolerance, other factors are likely to contribute to species zonation at salt lakes. The higher water use efficiency of the C4 T. indica compared with the C3 T. pergranulata may provide an advantage in the drier dune habitat on salt lake margins. An additional experiment confirmed the hypothesis that survival of T. pergranulata seedlings is enhanced by the duration of reduced salinity after germination, as would occur following significant rainfall, as older seedlings maintained higher growth rates during subsequent increases in salinity.

Salinity and waterlogging tolerances in three stem-succulent halophytes (Tecticornia species) from the margins of ephemeral salt lakes

Background and aims Tecticornia species are stem-succulent, perennial halophytes (sub-family Salicornioideae; Chenopodiaceae) that inhabit saline areas including the margins of ephemeral salt lakes in Australia. Based on zonation observed at salt lakes, species were hypothesised to differ in tolerances to salinity and/or waterlogging.

Astrobiological significance of the sabkha life and environments of southern Tunisia

In high-salinity and water-scarce environments, such as in hot and dry deserts, species develop adaptive strategies that are necessary for living in such harsh conditions. Continental ephemeral salt lakes (sabkhas) with periodic flooding from subsurface groundwater followed by high salt concentrations, such as the ones of the northern Africa Chotts, rank among the geological settings wherein the combined effect of salt concentration and fluctuation of water availability make the environment unstable and can thereafter lead to extreme changes. The present study investigates the continental sabkha environments of southern Tunisia, in which ecological niches (i.e. water and salt precipitates, including halite, gypsum, and dolomite) host microbial life. Halophilic microorganisms can be trapped in the extensive saline crusts of halite and gypsum, which can be regarded as the first step of their delivery to the fossil record. The study of halophiles can provide clues for the understanding of life strategies in extreme terrestrial environments, such as sabkhas, which are potential good terrestrial analogs for evaporite-bearing Martian deposits.

The Importance of the Makgadikgadi Salt Pans in Botswana for Flamingos in Africa

Little is known about the feeding ecology and breeding success of the Lesser Flamingo (Phoeniconaias minor) and Greater Flamingo (Phoenicopterus ruber roseus) on the ephemeral salt lake of the Makgadikgadi, Botswana. Some observations of large numbers of both species have been recorded breeding on the Makgadikgadi salt pans, and it is believed that this site is among the most important breeding sites for both species of flamingo in Africa. This paper addresses the importance of the Makgadikgadi salt pans by revising some of the observations made in the past and also introduces a long-term research project that is currently underway to determine more about the ecology of the pans and the flamingo breeding success at this important site.

Ecology of Coxiella (Mollusca, Gastropoda, Prosobranchia), a snail endemic to Australian salt lakes

Features of the taxonomy, physiology and ecology of Coxiella, a gastropod of Australian salt lakes, are discussed. It is concluded that the present taxonomic basis for species descriptions needs complete revision. The genus is widely distributed in southern Australian ephemeral and permanent salt lakes and is also known from central Australia and northern Queensland. Although an osmoconformer, active specimens have been recorded from lakes with salinities between 6 and 124 g l −1. With gradual acclimation, a population from Lake Tallinga, a South Australian ephemeral salt lake, had LD 50 limits for salinity of 2 and 95.5 g l −1; with direct transfer these limits narrowed to 6 and 83 g l −1. Animals from the same locality were moderately tolerant to high temperatures, desiccation and low oxygen concentrations. The life-cycle seems to involve iteroparous, intermittent reproduction, with rather few resources devoted to reproduction. Survival over the unfavourable season (lake dry or too saline) is as adults. It seems that Coxiella survives in ephemeral salt lakes because its behaviour meliorates environmental extremes and because it has an ecological strategy which can successfully overcome the risk of life in such environments.

Observations of salt particles in the atmosphere in the vicinity of an inland salt lake: Lake Eyre, South Australia

Lake Eyre is an ephemeral salt lake in arid country 400 km from the sea. The contributions to the total atmospheric aerosol sodium from sea-salt and lake-salt were determined close to the lake over a four-day sampling period in May 1984. Measurements at the lake site detected significant salt aerosol of marine origin. No conclusive evidence for significant lake-derived salt aerosol was obtained. Coincidence scintillation spectrometry was used to detect and assign sources to the particles. The salt was identified as marine in origin from the Na/K ratios for single particles greater than 0.4 μm radius and from the similarity of concentration versus mass plots for aerosol at Lake Eyre to plots of marine aerosol over the ocean and at cloud levels in central Queensland, Australia. Back trajectory analyses for air parcels reacing the sampling site during the experiment confirmed that the sampling site was not down wind of the lake and supported the conclusion that despite the proximity of the lake the salt aerosols detected were in fact marine. Over the sampling period the average mass loading of sea-salt in the air at 2 m above ground was 0.55 μg m −3. The estimated 400 million tons of NaCl in the lake is readily accounted for by deposition of sea salt within the lake catchment area, over a relatively short time.

Modern sedimentation and hydrology in Lake Tyrrell, Victoria

Abstract Lake Tyrrell is a large ephemeral salt lake, the level of which is controlled by climate and groundwater. Up to a metre of water fills the basin during the wetter and cooler winter season, but evaporates during the summer, precipitating up to 10 cm of halite. Each year essentially the same pool of ions is redissolved by this annual freshening. The small percentage of gypsum precipated (< 2%) in the surface salt crust reflects the low calcium content of the brine which, in turn, is a function of the negligible net discharge of calcium from the groundwater system. The small influx of fine‐grained clastic sediment to the lake floor comes from surface runoff, wind, and reworking of older sediment from the shoreline. The Lake Tyrrell basin lies in a setting in which three different groundwater types, identified by distinct salinities, interact with surface waters. A refluxing cycle that goes from discharging groundwater at the basin margin, to surface evaporation on the lake floor, to recharge through...