Salt Pans Research Articles

Towards global mapping of salt pans and salt playas using Landsat imagery: a case study of western United States

ABSTRACT Monitoring salt pans is important for agricultural management in arid/semi-arid regions because salt pans can negatively affect human life, wildlife, ecology, and cause accelerated desertification, cropland loss, and economic downturn. Spectral salt pan indices based on remotely-sensed data from previous studies vary by location and may not be readily applicable to another location due to the spatial heterogeneity of salt components across the continental surface. Using Landsat-8 imagery and climate datasets, this study aims to develop a mapping scheme which effectively delineates the maximum salt pan/playa extents under various spectral conditions for different geographic locations. Calibrated by a spectral training pool sampled from eight major salt pan/playa sites in the world, this mapping scheme first implements a conservative spectral index to highlight potential salt-covered regions, from which salt pans/playas are further extracted by a support vector machine (SVM). Quality assurance/quality control (QA/QC) with assistance of auxiliary datasets and high-resolution images was performed to reduce commission errors and refine the results. The mapping scheme was applied to the endorheic regions of the western United States with a total area of approximately 700,000 km2, of which 1.6% was mapped as salt pans. Quality assessments show reasonable reliability of the mapping result for most regions, with the producer’s accuracy, user’s accuracy, and kappa coefficient exceeding 90%. The mapped spatial details reveal that salt pans are distributed fairly evenly across the arid western United States, with areas positively correlated to the sizes of the endorheic basins. Given these results, we foresee potential applicability of the developed scheme to map salt pans/playas across Earth’s continental surface. Our spectral training pool and produced salt pan/playa extents are available through https://doi.pangaea.de/10.1594/PANGAEA.913152.

Geothermal Salt Factory (GSF) Design in Parangwedang Geothermal, Bantul, Special Region of Yogyakarta

Indonesia has the largest geothermal energy potential in the world with potential value ±28 GWe, but the potential of geothermal low enthalpy is still not utilized properly. On the other hand, improvement in the salt industry needs to be done because the salt industry in Indonesia has not been able to meet domestic salt demand. Domestic salt supply deficit is caused by the salt industry in Indonesia just relies on salt traditional farmers who are very dependent on the sunlight and the absence of a modern and sustainable salt-making industry. Therefore, the authors made a salt factory design using low enthalpy geothermal by utilizing Parangwedang geothermal as a heat source energy. Parangwedang geothermal is located in the Special Region of Yogyakarta with existence manifestation as a hot spring. Based on previous research, the potential of Parangwedang geothermal was 10 MWe. The reservoir rock may have a temperature range 115 °C and the hot spring fluid temperature 43 °C. The hot spring distance from the seashore is 403 meters with elevation reach 8 meters. The method used in this study is literature study and data collection in the field. Literature data is obtained from various sources and then compiled and grouped for the design of the salt factory that utilizes low enthalpy geothermal energy. This factory system will involve two pumps, one of which will drain the hot water from the Parangwedang hot spring and the other will drain the water from the ocean to the salt production pan. A boiling tank and condenser are used to boil the sea. Hot water from the boiling tank is used for drying the salt brine and brine is dried in the salt pan. In the result, the authors calculated factory production capacity, the GSF production capacity is ±14 tons salt each year.

Rediscovery of the enigmatic Andean frog Telmatobius halli Noble (Anura: Telmatobiidae), re-description of the tadpole and comments on new adult's characters, type locality and conservation status.

We report the rediscovery of Telmatobius halli (Hall's water frog), which had not been found since its description (over 80 years) since its type locality was not clearly established. "Aguas Calientes" near Ollagüe is hypothesized as the original type locality where Frank Gregory Hall collected the type material in 1935. The tadpole is re-described, and new data on the external and internal morphology of adults is provided. These new morphological data are compared with Telmatobius spp. inhabiting geographically close to T. halli in Chile and Bolivia. In addition, comments on its ecology, conservation, and taxonomic status in relation with other Telmatobius spp. inhabiting nearby areas in Ascotán and Carcote salt pans are provided. No evidence of Batrachochytrium dendrobatidis and Ranavirus infection was found in T. halli and a sympatric amphibian species. Our work supports the validity of T. halli and suggests this species should be considered as Data Deficient in the IUCN Red List assessment until taxonomic issues are resolved.

Shallow groundwater flow and inverted fresh/saline-water interface in a hypersaline endorheic basin (Great Basin, USA)

Pilot Valley is an 828-km2 arid-region endorheic basin in western USA. Bounding mountain ranges rise as much as 1,900 m above the nearly flat 379-km2 playa floor. Up to 3.8 m of Pleistocene Lake Bonneville mud and thin oolitic sand layers form the surface layer of the basin floor. Groundwater conditions were evaluated using data from shallow monitoring wells and borings, springs, infiltrometer measurements, slug and dilution tests, geophysical transects, and precision elevation surveys. Alluvial fan groundwater discharges at fan/playa interface springs and underflows to the shallow basin sediments along the western side of the basin; the groundwater only underflows along the eastern side. Precision surveying established a Lake Bonneville shore-line break in slope as the cause of the spring discharges. Tectonic tilting causes groundwater to flow from east to west and to the topographic low. Monthly measured and pressure transducer data established seasonal pressure responses and upward groundwater gradients. All basin groundwater is lost to evapotranspiration at the topographic low, where a thin salt pan has developed. Groundwater evolves from fresh to hypersaline near the alluvial fan/playa interface where there is an inverted salinity gradient and a groundwater pressure ridge. The pressure ridge and inverted salinity interface are due to: (1) osmotic pressure established between the oolitic sand of high hydraulic conductivity and the overlying low-hydraulic-conductivity lake mud at the fan/playa interface, and (2) the collision between fresh groundwater flow driven by a steep hydraulic head and hypersaline groundwater flow driven by a nearly flat hydraulic head.

Morphological impacts of the Chilean megathrust earthquake Mw 8.8 on coastal wetlands of high conservation value

The subduction earthquake Mw = 8.8 on February 27th, 2010 which affected Chile's south-central coast (37°S) produced a co-seismic uplift of ~1.4 m in coastal Tubul-Raqui wetland area, with abrupt morphological changes. In order to determine the magnitude of the changes, in this area of high conservation value, salt marsh morphological features were identified and quantified by mapping the changing extent of the coverage of morphological features before (2009) and after (2011–2012) the tectonic disturbance. Rectified satellite images of seven study sites were created for the three years using Google Earth images and processed in ArcGIS. The results indicate a total decline of 31.7% in the area of the morphological features and the emergence of 1.25 km2 of dried area; salt pans and tidal creeks were severely affected, with more than 90% loss. In contrast, there was a slight recovery of the Tubul and Raqui main river channel (12%) and the tidal channels (8.5%) between 2011 and 2012, mainly in the area near the river mouth. The salt marsh (cover by Spartina densiflora) showed slight variation after the co-seismic uplift (14.6%), demonstrating high tolerance in the face of high-impact natural disturbances. The changes and later evolution may be explained mostly by the action of the seismic cycle in subduction zones. Continuing to monitor state of the recovery of the salt marsh and other similar environments may help to understand the true role that the seismic cycle plays in the dynamics of coastal ecosystems, as well as its incidence in the recovery process.

Lithium and Brine Geochemistry in the Salars of the Southern Puna, Andean Plateau of Argentina

Abstract The Andean plateau is a small region of South America extending between northwest Argentina, southwest Bolivia, and northern Chile. It concentrates the largest global resources of lithium brines in its numerous salars. Of these, the giant salars in Bolivia and Chile have been relatively well studied; however, only little is known about the smaller but numerous salars in the Argentine Puna region. In this article, we present the results of the first regional-scale reconnaissance exploration of the 12 major salars situated in the southern part of the Puna plateau (24°S–26°30’S). Hydrochemical data indicate that the shallowest brines are characterized by highly variable Li concentrations, with mean Li grades ranging between 57 and 570 mg L−1, and mean Li/Mg ratios from 0.01 to 1.24. A survey of the brine chemistry of the salars across the Puna plateau, including its northern part, has revealed the absence of a geographical pattern in Li+ grade distribution. However, a comparison among mean Li+ grades, Li+/Mg2+ ratios, and the sizes of all salars allows an estimation of their Li mining potential. Specifically, the salt pan of Arizaro represents the highest potential, mainly due to its size; Antofalla-Botijuelas has a large surface and promising Li/Mg ratios for Li recovery via brine evaporation, though its elongated shape is a constraint; and Pastos Grandes, Pozuelos, and Rincón have encouraging Li grades, interesting salar sizes, and relatively easy access. Olaroz, Cauchari, and Hombre Muerto contain the highest Li+ grades in brines of the Argentine Puna and embody the most interesting perspectives of the Argentine plateau in a regional context. Salar sizes could be related to maximum Li+ grade of brines. Larger salars would then be expected to contain brines with higher Li+ grades than smaller ones, which could be considered as a useful criterion for surveys of brine-type deposits.

Decolorization of Textile Dye by Halophilic Exiguobacterium sp.VK1: Biomass and Exopolysaccharide (EPS) Enhancement for Bioremediation of Malachite Green

AbstractThe salt pan soil screened for the exopolysaccharides (EPS) producing organisms for the decolourization textile dyes. The isolate was characterized and confirmed as Exiguobacterium sp. VK1 by 16S rRNA analysis. The enhanced production of EPS was obtained with the minimal medium which was supplemented with various carbon sources, and cassava peel which has shown a 5.9 fold increase in the EPS (7704.71 mg/L) production. Exiguobacterium sp. VK1 removed Malachite Green (MG) dye (684.38 mg/g) with the maximum biosorption capacity of 79.1% at pH 6 and 40°C. With the increased EPS production, by supplementing the cassava peel, the MG dye adsorption also increased up to 97.61%, when decolorized within 30 min by Exiguobacterium sp. VK1. It was found that Pseudo Second‐order kinetics and Freundlich isotherm is the best fit for the equilibrium adsorption process of MG dye by Exiguobacterium sp. VK1. The thermodynamic properties such as activation energy (12.993 kJ/mol), change in enthalpy (10.501 kJ/mol), change in entropy ‐254.07 J/(mol K) and change in Gibbs energy (84.945‐90.026 kJ/mol) were investigated by Arrhenius and Eyring equation using Pseudo‐second‐order kinetic model. The result revealed that the adsorption process was thermodynamically feasible.

Layered mound, inverted channels and polygonal fractures from the Makgadikgadi pan (Botswana): Possible analogues for Martian aqueous morphologies

Layered mounds and inverted channels with polygonal fractures from the Ntwetwe Pan in the Makgadikgadi Basin (central Botswana) have been herein investigated. These morphologies are from an evaporitic basin (the Makgadikgadi Basin) that is the remnant of an ancient Pleistocene lake and is currently part of the world’s largest evaporitic system.The mounds in the Ntwetwe Pan are characterized by a layered structure and low relief (max. 5 m above the pan floor) and can be in excess of 2 ​km wide. The mounds consist mainly of loose (non-lithified) sand and silt with high moisture contents, even during the dry season. Geophysical investigations have shown that groundwater processes, particularly those related to the capillary fringe that rises and conveys moisture through the mounds, are factors that make mound sediments resistant to wind erosion.The inverted channels, identified in the southern part of the Ntwetwe Pan, are characterized by gentle reliefs and depressions, which depend upon the distribution of calcretes and indurated sediments. Large scale (up to 100 ​m wide) polygonal fractures localized at the front of the channels, disappear at the transition with the present-day pan floor.We consider that these particular mounds, within the Ntwetwe Pan, are remnants of the strandline of the paleo-Makgadikgadi Lake, and that the inverted channels represent distributary channels of a relict fan delta, formed by an ephemeral river, most likely the paleo-Boteti River, during a Lake Paleo-Makgadikgadi highstand stage. We consider that large scale (up to 100 ​m wide) polygonal fractures, located on the channel-mouth lobes, represent large-scale desiccation cracks formed by rapid water evaporation from delta deposits.The results of this investigation highlight the importance of the paleo-drainage system and its interactions with the water table and wind-deflation as main geomorphological factors within salt pan environments. The mounds in the Makgadikgadi pans also show strong geomorphic similarities to spring mounds on the surface of Mars, localized in equatorial layered deposits (ELDs). These ELDs mounds are considered to result from cyclical groundwater upwelling, evaporation and wind deflation. The geological processes that resulted in the formation of mounds within the Makgadikgadi pans may, therefore, help to explain how similar layered deposits formed on Mars and confirm existing theories.

Land and human resources vulnerability to the impact of climate change in ecologically important coastal regions

Climate change induced coastline changes and rising sea levels are likely to create vulnerable impacts on ecosystems, infrastructure, and associated populations the world over. The assessment of long term coastline changes in the past, coupled with the expected changes due to rising sea levels in the future, would aid in comprehending the response of the coastal processes to climate change so as to develop management measures. The coastline variations were delineated by multi dated Landsat satellite images of 45 years using spatial analysis and Digital Shoreline Analysis System. Submergence due to projected sea-level elevation of 50 cm and 100 cm was assessed using Shuttle Radar Topography Mission topographical data using geospatial techniques. The results revealed that the major shore is in the process of erosion at varying rates as well as periods. The highest mean erosion was observed at −6.76 m/yr in 89% of the coast between 1973 and 1988. The mean weighted linear regression rate of shoreline change was −2.39 + 7.05 m /yr from 1973 to 2018, the erosion being 83%. Besides, the sea level rise of 0.6 cm/year is expected to submerge 6983 ha of coastal resources, which includes mangroves, agriculture land, salt pans, and aquaculture farms from 82 villages in 2100. The expected inundation is likely to displace 20% of the human population in the region, including about 50,000 fishers. Government policies need to be developed in a people participatory and transparent mode to protect resources as well as livelihoods of the coastal communities.

Bioprospecting Studies of Halopholic Bacteria – Streptomyces sp. MA05 and Halobacterium sp. MA06

Halophile organisms such as Halobacterium salinarum and halophilic Actinomycetes flourish under the hostile hypersaline condition and are well known for their ability to produce novel bioactive compounds for bioprospecting analysis such as antibacterial, antifungal, anticancer, and enzyme analysis. In this present study, the objective is to isolate two types of halophiles, namely Halobacterium sp. MA06 and Streptomyces sp. MA05 based on their 16SrRNA gene sequencing. The two potential halophiles were isolated from the salt pan of Chennai, India. In order to evaluate enzyme analysis and pigment production of both the organism, optimization of the growth state of both species was performed on complex medium with various additives and different concentrations of sodium chloride and magnesium sulfate. The result showed that Halobacterium sp. MA06 produced orange colored pigment after characterization using GC-MS analysis. For Streptomyces sp. MA06, it was found to produce the enzyme amylase, hence Streptomyces sp. MA06 was subjected to producing the enzyme amylase, and the produced amylase will be characterized. The antimicrobial and anticancer activity was then carried out on the extract of Streptomyces sp. MA05 and the pigment of Halobacterium sp. MA06. In conclusion, the pigment from Halobacterium sp. MA06 and the enzyme amylase from Streptomyces sp. MA05 could be a novel bio-sourced for bioprospecting of bioactive natural products.

Diversity of a bacterial community associated with Cliona lobata Hancock and Gelliodes pumila (Lendenfeld, 1887) sponges on the South-East coast of India

Marine sponges are sources of various bioactive metabolites, including several anticancer drugs, produced mainly by sponge-associated microbes. Palk Bay, on the south-east coast of India, is an understudied, highly disturbed reef environment exposed to various anthropogenic and climatic stresses. In recent years, Palk Bay suffered from pollution due to the dumping of untreated domestic sewage, effluents from coastal aquaculture, tourism, salt pans, cultivation of exotic seaweeds, and geogenic heavy-metal pollution, especially arsenic, mercury, cadmium, and lead. Low microbial-abundant sponge species, such as Gelliodes pumila and Cliona lobata, were found to be ubiquitously present in this reef environment. Triplicate samples of each of these sponge species were subjected to Illumina MiSeq sequencing using V3–V4 region-specific primers. In both C. lobata and G. pumila, there was an overwhelming dominance (98 and 99%) of phylum Candidatus Saccharibacteria and Proteobacteria, respectively. The overall number of operational taxonomic units (OTUs) was 68 (40 and 13 OTUs unique to G. pumila and C. lobata, respectively; 15 shared OTUs). Alphaproteobacteria was the most abundant class in both the sponge species. Unclassified species of phylum Candidatus Saccharibacteria from C. lobata and Chelotivorans composti from G. pumila were the most abundant bacterial species. The predominance of Alphaproteobacteria also revealed the occurrence of various xenobiotic-degrading, surfactant-producing bacterial genera in both the sponge species, indirectly indicating the possible polluted reef status of Palk Bay. Studies on sponge microbiomes at various understudied geographical locations might be helpful in predicting the status of reef environments.

16s rRNA metagenomic analysis reveals predominance of Crtl and CruF genes in Arabian Sea coast of India

Microbial communities perform crucial biogeochemical cycles in distinct ecosystems. Halophilic microbial communities are enriched in the saline areas. Hence, haloarchaea have been primarily studied in salterns and marine biosystems with the aim to harness haloarcheal carotenoids biosynthesis. In this study, sediment from several distinct biosystems (mangrove, seashore, estuary, river, lake, salt pan and island) across the Arabian coastal region of India were collected and analyzed though 16s rRNA metagenomic and whole genome approach to elucidated the dominant representative genre, haloarcheal diversity, and the prevalence of Crtl and CruF genes. We found that the microbial diversity in mangrove sediment (794 OTUs) was highest and lowest in lake and river (558–560 OTUs). Moreover, the bacterial domain dominated in all biosystems (96.00–99.45%). Top 10 abundant genera were involved in biochemical cycles such as sulfur, methane, ammonia, hydrocarbon degradation, and antibiotics production. The Archaea was mainly composed of Haloarchaea, Methanobacteria, Methanococci, Methanomicrobia and Crenarchaeota. Carotenoid gene, Crtl, was observed in a major portion (abundance 60%; diversity 45%) of microbial community. Interestingly, we found that all species under haloarcheal class that were represented in fresh as well as marine biosystems encodes CruF gene (bacterioruberin carotenoid). Our study demonstrates the high microbial diversity in various ecosystems, enrichment of Crtl gene, and also shows that Crtl and CruF genes are highly abundant in haloarcheal genera. The finding of ecosystems specific Crtl and CruF encoding genera opens up a promising area in bioprospecting the carotenoid derivatives from the wide range of natural biosystems.

Rapid Resource Change and Visitor-Use Management: Social-ecological Connections at the Bonneville Salt Flats.

Parks and protected areas are complex, and managers often need integrated social-ecological science-based information that illuminates the dynamic interactions between the biophysical and social processes. However, modeling and determining social-ecological connections are difficult due to disciplinary paradigms, divergent research questions, and data sets representing different scales. During this investigation, researchers sought to evaluate social-ecological linkages at a large salt pan (Bonneville Salt Flats) in western Utah (US). Specifically, the investigation evaluated how the changing level and location of salt-crust moisture and ponding water influenced visitors' spatial distribution of use and important elements of their experience. The findings indicate that visitors travel more distance, spend more time recreating, and use the Salt Flats in higher densities during dry conditions. However, the results also highlight that importance levels ascribed to specific aspects of the visitor experience remained relatively stable regardless of changes in salt-crust moisture and ponding water. Illuminating such linkages is important because most natural resource issues in society, including resources at the Bonneville Salt Flats, are not solely ecological or social in nature but characterized by deeper enmeshment between the two.

La red de salinas y el comercio de la sal en el estuario del Tinto durante la Edad Moderna: Huelva, San Juan del Puerto, Palos de la Frontera y Moguer

Salt during the Old Regime became one of the instruments for the development of the economy of the towns located around the Tinto river (western Andalusia, Spain) because it was a fundamental product for the preservation of food, the preparation of the supplies and logistics for the ships that left their ports since the time of the discoveries. As a consequence of the demand for this marine resource, there was a network of salt flats destined for regional consumption and the commercial circuits that connected the Atlantic and Mediterranean routes. Precisely, the commercial profitability of the exploitation of the aforementioned product and the tax regime that imposed on it, motivated that the noble lineage (Medina Sidonia, Portocarrero, Saltés and Cifuentes) tried to dominate the ownership of the exploitation of the salt pans since the late Middle Ages despite having originally been a royal prerogative.

Long term trends and breeding parameters of Gull-billed Tern <em>Gelochelidon nilotica</em> in three Italian coastal sites

Between 2001 and 2018 colonies of Gull-billed Tern were monitored in large wetland complexes of Veneto (lagoon of Venice and the Northern Po Delta) and Sardinia (western and southern) regions. Most of the colonies settled in man-made structures such as islets, levees, dams, located inside fish farms, fish ponds and salt pans. Laying took place around half May until early June (Veneto), with eggs occurring in the nests until half July (Sardinia). Colonies had 3-230 pairs, with several instances of isolated pairs; colonies were mono- or plurispecific, with other Charadriiformes. The number of eggs per clutch was 2.6±0.6 (N=111, 1 SD) in the Venice lagoon, 2.6±0.6 (N=182) in the Po delta, 2.3±0.70 (N=1007) in Sardinia; hatched eggs were 2.2±0.6 (N=111), 2.0±0.7 (N=182) and 1.7±0.67 (N=40) per nest, respectively. The most important cause of breeding failure was due to flooding of nesting sites, due to the rapid increase of water levels inside fish farms and salt pans. During the 2001-2018 years, the Gull-billed Tern nested regularly in Sardinia, whereas in the Po Delta the first nesting occurred in 2001 and in the lagoon of Venice in 2008. The whole population ranged between 34 and 417 pairs until 2017 (223.6±113.4, N=17), with a sudden increase up to almost 1,000 pairs in 2018; the overall trend is of strong increase (p<0.01), with an annual rate of 10.5%.

A hydrogeochemical appraisal and multivariate statistical analysis of seawater intrusion in point calimere wetland, lower Cauvery region, India

Seawater intrusion is a major threat to the water quality in the coastal aquifers. A hydrogeochemical survey was conducted in and around the Point Calimere wetland with an objective to delineating the impact and sources of groundwater salinization. These objectives were met by a combined hydrochemical and multivariate statistical approach. Groundwater samples showed an alkaline nature throughout the area. It was substantiated by the observed positive correlation of TDS with Na, Mg and Cl and a negative correlation with HCO3. Ionic changes during the saline water-freshwater mixing were analyzed. It was detected that the mixing rate of seawater with the fresh groundwater was 31%. A negative e.change was observed for the samples collected near the coast as well as salt pans. The sources of salinity identified through factor analysis exhibited a clear segregation between freshwater and saline water. The presence of Ca and SO4 in the factor 2 shows the dissolution of gypsum minerals. The dendrogram generated through cluster analysis classified the total groundwater samples into two groups which agrees with the results obtained from the hydrochemical and factor analysis. The wells that are near the coast and salt pans, which are grouped under cluster 1, have influence of saline intrusion.

Accuracy and spread of nest search behaviour in the Saharan silver ant, Cataglyphis bombycina, and in the salt pan species, Cataglyphis fortis

Desert ants of the genus Cataglyphis are renowned for their navigation abilities, especially for their beeline homing after meandering foraging excursions reaching several hundreds of meters in length. A spiralling nest search is performed when an ant misses the nest entrance upon completing its homebound travel. We examined the nest search behaviours of two desert ant species dwelling in different habitats—Cataglyphis bombycina living in the dunes of the Sahara and Cataglyphis fortis found in the salt pans of North Africa. The two species show distinct differences in walking behaviour. C. bombycina performs a strict tripod gait with pronounced aerial phases, high stride frequencies, and extremely brief ground contact times. In view of these peculiarities and the yielding sand dune substrate, we hypothesised that homing accuracy, and namely distance measurement by stride integration, should be lower in C. bombycina, compared to the well-studied C. fortis with less specialised walking behaviour. We tested this hypothesis in ants’ homebound runs from a feeding site in a linear channel setup. Surprisingly, the accuracies of nest searches were similar in the two ant species, and search accuracy was also independent of the walking substrate, soft dune sand or a hard floor. The spread of the nest search, by contrast, differed significantly between the two species, C. bombycina exhibiting a larger search spread. This may be interpreted as an increased path integration uncertainty due to the above locomotor specialisations, or as a compensation strategy accounting for the silver ants’ particular environmental and behavioural situation.

Gate operation for habitat-oriented water management at Budai Salt Pan Wetland in Taiwan

Commercial salt pans around the world act as important habitats for waterbirds due to their unique trophic and physical attributes. Today, most commercial salt pans in Taiwan have been decommissioned and many have been designated as protected wetland habitats. Due to the dike and water gate systems controlling water flow in the salt pan wetlands, water management plans are important for habitat maintenance. Despite this, creation and implementation of habitat-oriented water management plans in protected salt pan wetlands is not common practice, especially in areas where flooding is a concern. In order to understand the potential for implementing water management plans for habitat creation in salt pan wetlands located in flood prone regions, this study designed and conducted three water management experiments for Budai Salt Pan Wetland, a wetland of national importance along the southwestern coast of Taiwan. The three experiments were designed to better understand the impacts of allowing water into the wetland during both the end and the beginning of the dry season in Taiwan. The design of each water gate operation was unique, based on the initial hydrologic conditions, and needs of the experiment in order to inform the design of future water management plans for the wetland. The consequent influence of gate operations on water depth, salinity, and immediate bird use of the wetland were analyzed. The experiments show that the water management techniques adopted in the study can allow for the creation of habitat types with varying water depths and salinity while not increasing flood risk to surrounding communities. Because the gate operation experiments were short term, a complete understanding of bird responses was limited. Even so, the responses of waterbird communities to these depth manipulations did indicate the potential of water management to increase foraging opportunities. The methods and findings of this research can inform wetland management and policy throughout Taiwan and the rest of the world.

Dust provenance and its role as a potential fertilizing agent for the Okavango Delta, Botswana

AbstractDust plays a globally important role in supplying biologically essential elements to landscapes underlain by nutrient‐poor substrates. Here we show that dust may play a significant role in sustaining productivity in the vast wetlands of the Okavango Delta in southern Africa, one of the world's richest biodiversity hotspots. Dust accumulates preferentially on tree‐covered islands in the seasonal swamps of the Delta, creating pockets of fine‐grained, nutrient‐rich material within the semi‐arid landscape of the Kalahari Desert. Strontium and neodymium isotopes reveal that this dust likely originates predominantly from the Makgadikgadi salt pans, located 300 km away, and contributes 10–80% of the fine‐grained material present in Okavango island soils. Surface material sourced from the Makgadikgadi Pans contains relatively high amounts of bioavailable phosphorus and iron, potentially influencing Okavango Delta biological productivity. We propose that long‐term ecosystem productivity and nutrient availability in the Okavango may be strongly mediated by regional dust inputs. Understanding the influence of dust deposition on nutrient loads and biogeochemical cycling is thus critical for predicting the response of the Okavango Delta to future changes in climate. We suggest that dust inputs may play a significant role in the supply of nutrients to other large, global wetland systems located in dryland environments. © 2020 John Wiley & Sons, Ltd

Saharan lithium: Brine chemistry of chotts from eastern Algeria

Salt pan brines in desert areas are globally known to be rich sources of lithium. This study reports the results of a regional survey of brine chemistry in chotts (salt pans) conducted along a 550 km long valley in the northeast Algerian Sahara, one of the major desert areas on Earth. A dataset composed of 50 samples, including brine, river, and aquifer, is integrated and discussed in order to study the characteristics of Sahara brines. Brines contain up to 66 mg L−1 of lithium, salinities up to ~400 g L−1, and magnesium concentrations ~690 times greater than that of lithium. The primary source of major ions would occurr by dissolution of ancient evaporites of the substrate by aquifer waters. Near surface lithium concentration of brines in chotts across the study area and in the aquifer Complexe Terminal defines a pattern of increasing values to the north, where maximum values coincide with chotts (Melghir and Merouane) having the largest sizes (up to 1,840 km2) and placed at the lowest altitudes (36 m below sea level). This pattern coincides with the northwards plunging structured substrate. Lithium grades increase consistently with salinity during the concentration through evaporation. However, lithium continues to concentrate beyond evolved brines whether due to the precipitation of lithium-free salts leading to lithium increases in residual brine, and/or by unknown processes supplying additional lithium. Discussed aspects are expected to drive an increasing interest on chotts, which would reveal in the future, as a stimulating opportunity for Algeria and the Saharan region.