Shallow Ponds Research Articles

INVESTIGATING THE MICROBIOTA OF SOLAR SALTERN OF MULUND, MUMBAI, INDIA

Solar salterns, located in tropical and subtropical areas worldwide, are artificial shallow ponds for the production ofhalite (NaCl) from seawater. They are often built as multipond systems. Multi-pond solar salterns have been widespreadenvironments for studies on halophilic microorganisms. In the present study Archaeal and bacterial diversity of thesalterns located at Mulund (19°10’12’’N, 72°57’18’’E), Mumbai was investigated. Three Halophiles were isolated fromthe brine samples collected. All isolated archaea were shown intensely orange pigmentation. These salt tolerantorganisms were characterized using morphological, biochemical and 16S rRNA analysis. Phylogenetic analysis of thesesequences revealed a range of identities to several group of bacteria. The clones fell into major lineages theActinobacteria and firmicutes. Presence of industrially important carotenoids producing halophiles were also recorded.

A Third Pond on the Mauna Kea Summit Plateau

Few ponds are found in the permeable volcanic landscape of Hawaii. After Hurricane Lane passed close to Hawaii Island in August 2018, causing record rainfalls, a pond temporarily emerged on the Mauna Kea summit plateau that had never been reported before. We characterize the pond using satellite observations and electrical resistivity tomography. The shallow pond is located on glacial till 3,594 m a.s.l., and was visible for less than 1 week. The geophysical survey, carried out 10 months after the pond's appearance and disappearance, revealed a layer of low electrical resistivity at depths of about 1–3 m below the surface, which, based on laboratory analysis, likely represents a perennial body of water well protected from evaporation. The existence of a third pond, in addition to Lake Waiau and Pu‘upōhaku Pond, in the previously glaciated area suggests perching layers are not uncommon. Montmorillonite, a 3-layer shrink-swell clay that can help to perch water, was identified in the Lake Waiau area. Mineral analysis on surface samples of the third pond did not reveal such a clay mineral.

Mechanisms shaping the gypsum stromatolite-like structures in the Salar de Llamara (Atacama Desert, Chile)

The explanation of the origin of microbialites and specifically stromatolitic structures is a problem of high relevance for decoding past sedimentary environments and deciphering the biogenicity of the oldest plausible remnants of life. We have investigated the morphogenesis of gypsum stromatolite-like structures currently growing in shallow ponds (puquíos) in the Salar de Llamara (Atacama Desert, Northern Chile). The crystal size, aspect ratio, and orientation distributions of gypsum crystals within the structures have been quantified and show indications for episodic nucleation and competitive growth of millimetric to centimetric selenite crystals into a radial, branched, and loosely cemented aggregate. The morphogenetical process is explained by the existence of a stable vertical salinity gradient in the ponds. Due to the non-linear dependency of gypsum solubility as a function of sodium chloride concentration, the salinity gradient produces undersaturated solutions, which dissolve gypsum crystals. This dissolution happens at a certain depth, narrowing the lower part of the structures, and producing their stromatolite-like morphology. We have tested this novel mechanism experimentally, simulating the effective dissolution of gypsum crystals in stratified ponds, thus providing a purely abiotic mechanism for these stromatolite-like structures.

Fine-Scale Assessment of Greenhouse Gases Fluxes from a Boreal Peatland Pond

Ponds are abundant in the boreal peatland landscape, which are potential hotspots for greenhouse gas (GHG) emissions. However, compared to large lakes, ponds are difficult to identify by satellite, and they have not been adequately studied. Here, we observed methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) fluxes in the growing season at three sites along the water table gradient from the pelagic zone, littoral zone and bog across a shallow pond in a boreal peatland landscape in Northeastern China. The results showed that the littoral zone, dominated by herb Carex, was the hotspot for CH4 emissions. CH4 fluxes in littoral zone averaged 78.98 ± 19.00 mg m−2 h−1. The adjacent bog was a weak source of CH4 emissions, with an average flux of 0.07 ± 0.05 mg m−2 h−1. Within the pond, CH4 was mainly emitted through ebullition, accounting for 88.56% of the total CH4 fluxes, and the ebullition fluxes were negatively correlated with dissolved oxygen (DO). CO2 fluxes were highest in the pelagic zone, with an average of 419.76 ± 47.25 mg m−2 h−1. Wind and strong sediment respiration were key factors that led to the high fluxes. The observed three sites were all atmospheric N2O sinks ranging from −0.92 to −10.90 μg m−2 h−1. This study highlights the spatial variation in greenhouse gas fluxes from the pond and its adjacent bog, ignoring the ecotone area may underestimate CH4 fluxes. Although ponds are a hotspot for CH4 and CO2 emissions, they can also be a sink for N2O, which provides a reference for the quantification of global pond GHG fluxes. Therefore, finer-scale in situ observations are necessary to better understand the feedback of permafrost peatland ponds to global warming.

A new freshwater amphipod (Amphipoda, Gammaridae), Gammarus tumaf sp. nov. from the Gökgöl Cave, Türkiye

A new amphipod species belonging to the genus Gammarus is described from the Gökgöl Cave, Zonguldak Province, Türkiye. The newly-identified species is relatively small (13 mm) and is a member of the Gammarus pulex-group by the presence of numerous long setae along the posterior margins of pereopods 3 and 4. The specimens were sampled from a shallow pond located in the dark zone (about 1 km inside the entrance) of the cave. Minute eyes, setose (both peduncle and flagellar segments) second antenna, slightly swollen flagellar segments of the second antenna, setose pereopods 3 and 4 and relatively short endopod/exopod ratio of the third uropod are the character combination of the newly-identified species in addition to lacking body pigmentation. The molecular phylogeny, based on the concatenated dataset (28S+COI, 1495 bp) indicated that the new species was resolved from the other Gammarus species by high bootstrap (NJ: 100, ML: 100). In addition to Gammarus tumafsp. nov., mtDNA COI and nuclear DNA 28S gene data of Gammarus baysaliÖzbek et al., 2013 were recorded for the first time. The newly-identified species was well-differentiated from the genetically closest species, G. baysali, with genetic distance of 12.22% and 0.55% for the COI and 28S genes, respectively. Detailed descriptions and drawings of the extremities of the holotype male were given and the morphology of the newly-identified species is compared with its relatives.

A STOCHASTIC PROGRAMMING APPROACH FOR SOLAR SALT PRODUCTION PROCESS OPTIMISATION

The solar salt mining process involves collecting salt water from the sea and trapping it in an interlinked network of shallow ponds where the sun evaporates most of the water. As soon as the brine reaches its saturation point, salt crystallisation occurs. Several factors influence this mining process, each with a degree of variability that results in a risk factor owing to uncertainty. This study proposes a two-stage stochastic programming model, called ‘a recourse model’, that maximises salt crystallisation while providing solutions that are hedges against uncertainty. First, the theoretical background on optimisation theory is provided, followed by an overview of the mining processes. Second, the recourse model is verified and validated using historical data and comparing the results with its deterministic counterpart. The main contribution of this study is the formulation of the recourse model and the value that this approach adds when dealing with uncertainty in any decision-making process.

Геоэкологическая характеристика водного объекта без названия, расположенного вблизи рекультивированного полигона твердых коммунальных отходов Калининградской области

The article presents the results of a study of one of the artificial reservoirs in Kaliningrad – a pond w / n with coordinates 54°69ʹ90ʺ N, 20°36ʹ46ʺ E. (hereinafter – the pond), located 0,4 km south of the reclaimed municipal solid waste landfill (hereinafter – the MSW landfill) in the settlement named after A. Kosmodemyansky (Kaliningrad) and 0,6 km from the water area of the Vistula Bay, which is a reservoir of the highest category, which is both amateur and industrial fishing. Through the pond, since the formation of the MSW landfill in 1978, there has been a surface runoff of water containing leachate from the waste dump. After landfill reclamation, the pond is studied for the state of its biota, the chemical composition of water and bottom sediments. The objectives of this study include assessing the degree of impact on the aquatic ecosystems of the MSW landfill by studying the relief features of the pond basin, determining and comprehensively analyzing the obtained morphometric indicators that have a significant impact on the appearance and development of the reservoir, its hydrological regime, the distribution of physicochemical parameters in the thickness water and the current ecological state. In 2021, a bathymetric survey was carried out using a Lowrance HDS-16 echo sounder-chartplotter, during which information about the current depth and geographic coordinates of the studied bottom area was jointly recorded in real time. For the first time, maps of the relief of the bottom of the pond in 2D and 3D format were built. Investigated the drainage basin of the pond. During the subsequent analysis of the obtained results, the main morphometric parameters of the pond were determined. According to the results of calculations, the pond can be attributed to shallow ponds of medium size, with a water surface area of 0,035 km2 and an average depth of 1.8 m. The outlines of its coastline are close to a square.

Temporal evolution of the Fogo Volcano magma storage system (Cape Verde Archipelago): a fluid inclusions perspective

The architecture of the magma storage system underneath Fogo Volcano (Cape Verde Archipelago) is characterised using novel fluid inclusion results from fifteen basanites, spanning the last 120 thousand years of volcanic activity, and encompassing a major flank collapse event at ∼73 ka. Fluid inclusions, hosted in olivine and clinopyroxene, are made of pure CO2, and based on their textural characteristics, are distinguished in early (Type I) and late (Type II) stage. Inclusions homogenize to a liquid phase in the 2.8 to 30.8 °C temperature range. Densities values, recalculated assuming an original 10% H2O content at the time of trapping, range from 543 to 952 kg·m−3, and correspond to entrapment or re-equilibration pressure ranges of 500–595 MPa, 700–740 MPa, and 245–610 MPa respectively for pre-collapse, early post-collapse, and Holocene/historical eruptions. These entrapment pressures are interpreted as reflecting the existence of two main magma accumulation zones at ∼25 km and ∼ 13–21 km depth, and a zone of fluid inclusion re-equilibration at 9–12 km depth. There is evidence of a complex temporal evolution of the magma system. Historical eruptions, and especially the three most recent ones (occurred in 1951, 1995 and 2014–25), bring fluid inclusion evidence for transient, pre-eruptive shallow (9–17 km depth) magma ponding. Early post-collapse (60 ka) volcanics, in contrast, document fast magma transport from ∼25 km, and suggest a reconfiguration of the magma system after the Monte Amarelo collapse event.

Asymmetric Male Mating Success in Lek-Breeding Rhinella arenarum.

Mate choice is the attempt of an individual to gain higher reproductive fitness by preferring to mate with some individuals and not with others. We studied the role of mate choice in the mating system of the neotropical toad Rhinella arenarum by assessing male reproductive tactics for mate acquisition and the contribution of female choice for pair formation. In a shallow pond in central Argentina, we estimated male mating success and the corresponding reproductive tactics by focal observation. The variation of phenotypic and genotypic traits (size and shape, longevity, vocalization features, heterozygosity) was related to the observed mating success in 110 males. The phonotactic response of 21 reproductive females to conspecific advertisement call features was tested in arena experiments. Mating success was limited to 32 males, pair formation was size-assortative. The dominant reproductive tactics were advertising from call positions near suitable breeding sites and pre-mating fights with intruding males, whereas the interception of amplectant pairs and the displacement of mated males were never observed. Female phonotaxis was directed to conspecific choruses but complex and simple call structures were not distinguished. We conclude that the mating system is a lek combining pre-mating fights among males and female choice of slightly smaller males. Fights interfere with female choice, undermining size-assortative mating. This is a unique system in the R. marina species group, in which interception behavior dominates reproduction.

Testing a novel sonar‐based approach for measuring water depth and monitoring sediment storage in beaver ponds

AbstractWidely available ‘fish‐finder’ echo‐sounding devices are beginning to be used in bathymetric studies to estimate geomorphic change. To date, however, there have been no applications in shallow and complex wetlands, where changes in sediment storage are notoriously dynamic in time and difficult to describe accurately in space. Therefore, in this study, we tested the performance of an ‘off‐the‐shelf’ fish‐finder for mapping bathymetry in a shallow beaver pond. We tested fish‐finder sonar depth readings against a traditional‐sounding lead‐line method across 21 paired Sampling Points with a minimum depth of 0.31 m and a mean of 0.65 m. Spatial accuracy of the unit was also tested against a differentially corrected Global Navigation Satellite System (GNSS) receiver. Measured depths to pond bottom from the fish‐finder were on average within 5%, although significantly 0.015 m (SD = 0.034) less than those obtained by the lead‐line method. Spatial accuracy, however, varied greatly compared to the corrected GNSS receiver readings, with a mean discrepancy of 2.7 m (SD = 1.5) but up to 6.2 m. Given the close match of depth readings between the two methods, we conclude that sonar is a suitable, cost‐effective, and less‐intrusive method than existing techniques, even in moderately vegetated shallow waterbodies. Methods do need to be adopted to account for poor spatial precision with ‘off‐the‐shelf’ fish‐finder models, but this can be rectified with survey design or using a secondary GNSS. Application of this technology will allow rapid one‐off surveys or repeated monitoring of depth, bedform and sediment accumulation in otherwise hard‐to‐access or disturbance‐sensitive wetlands, such as beaver ponds and water treatment or flow attenuation wetlands.

Nonlinear effects of environmental drivers shape macroinvertebrate biodiversity in an agricultural pondscape.

Agriculture is a leading cause of biodiversity loss and significantly impacts freshwater biodiversity through many stressors acting locally and on the landscape scale. The individual effects of these numerous stressors are often difficult to disentangle and quantify, as they might have nonlinear impacts on biodiversity. Within agroecosystems, ponds are biodiversity hotspots providing habitat for many freshwater species and resting or feeding places for terrestrial organisms. Ponds are strongly influenced by their terrestrial surroundings, and understanding the determinants of biodiversity in agricultural landscapes remains difficult but crucial for improving conservation policies and actions. We aimed to identify the main effects of environmental and spatial variables on α-, β-, and γ-diversities of macroinvertebrate communities inhabiting ponds (n=42) in an agricultural landscape in the Northeast Germany, and to quantify the respective roles of taxonomic turnover and nestedness in the pondscape. We disentangled the nonlinear effects of a wide range of environmental and spatial variables on macroinvertebrate α- and β-biodiversity. Our results show that α-diversity is impaired by eutrophication (phosphate and nitrogen) and that overshaded ponds support impoverished macroinvertebrate biota. The share of arable land in the ponds' surroundings decreases β-diversity (i.e., dissimilarity in community), while β-diversity is higher in shallower ponds. Moreover, we found that β-diversity is mainly driven by taxonomic turnover and that ponds embedded in arable fields support local and regional diversity. Our findings highlight the importance of such ponds for supporting biodiversity, identify the main stressors related to human activities (eutrophication), and emphasize the need for a large number of ponds in the landscape to conserve biodiversity. Small freshwater systems in agricultural landscapes challenge us to compromise between human demands and nature conservation worldwide. Identifying and quantifying the effects of environmental variables on biodiversity inhabiting those ecosystems can help address threats impacting freshwater life with more effective management of pondscapes.

Studi Literatur : Pengaruh Suhu terhadap Ikan Nila (Oreochromis niloticus)

Tilapia is one example of fish that is successfully cultivated in the world. Tilapia can live in deep and wide waters as well as in narrow and shallow ponds, and can live in rivers. The main environmental and management factors that affect the survival and growth of fish are dissolved oxygen levels, temperature, pH, feeding rate, and others. This study aims to determine the effect of temperature on tilapia (Orechromis niloticus). The method used in this research is a literature study (systematic review) by analyzing several scientific articles that are relevant to the study being discussed. The results of this study are known that temperature is very influential on several aspects of life, namely the level of survival, appetite, level of stability of the body for disease, growth rate, fish movement, viscosity and blood flow, oxygen consumption, leukocyte count, glucose level. in the blood, the number of erythrocytes, the number of platelets, the reaction of changing ammonium to ammonia, seed maintenance, tilapia weight, spermatogenesis stage in male individuals, hemoglobin concentration, feminization and masculinization of gonads, gastric evacuation rate, number of egg production, swimming speed, metabolic rate, response to feeding, the level of infertility in female fish, tilapia seed weight, fish stress level, the mechanism for determining the number of sex ratios, ovarian structure, and testicular structure. The conclusion of this study is that temperature greatly influences the life of tilapia (Oreochromis niloticus).

Epiplastic microhabitats for epibenthic organisms: a new inland water frontier for diatoms

Plastic pollution is widespread in each type of ecosystems. However, the colonization events of microorganisms on plastics seem to be neglected in inland waters. Therefore, in this study we analyze the possible colonization on the surface (hereafter epiplastic microhabitats) of two typology of plastic supports by diatom community. Specifically, we located 20 supports in expanded polystyrene and 20 in polyethylene terephthalate both floating and dipped (~ 1 m) in a central Italian shallow water pond, in order to evaluate the diachronic colonization of diatoms from November 2019 to August 2020. Our result showed the tendency in colonizing both epiplastic microhabitats without significant differences in number of species; additionally, depth does not appear to affect the number of species. As regard the temporal colonization, the number of species tends to increase over time from autumn-winter to spring-summer in both types of epiplastic microhabitats and depth. Instead, increase in dominance of some species over time has been demonstrated: only a few species keep a high number of individuals compared to the others; therefore, the number of individuals within the species is not uniformly distributed. These results suggest the tendency of diatom community to colonize plastic supports in lentic waters, and this evidence can be very important because artificial supports can increase the surface available for the settlement of the algae community with an increase of productivity and the colonization of new communities of different taxa. Further studies are mandatory to investigate the possible effects on the epiplastic community and the ecological implications in freshwater environments.

Heat waves rather than continuous warming exacerbate impacts of nutrient loading and herbicides on aquatic ecosystems.

Submerged macrophytes are vital components in shallow aquatic ecosystems, but their abundances have declined globally. Shading by periphyton and phytoplankton/turbidity plays a major role in this decline, and the competing aquatic primary producers are subject to the complex influence of multiple stressors such as increasing temperatures, nutrient loading and herbicides. Their joint impact has rarely been tested and is difficult to predict due to potentially opposing effects on the different primary producers, their interactions and their grazers. Here, we used 48 mesocosms (2500 L) to simulate shallow lakes dominated by two typical submerged macrophytes, bottom-dwelling Vallisneria denseserrulata and canopy-forming Hydrilla verticillata, and associated food web components. We applied a combination of nutrient loading, continuous warming, heat waves and glyphosate-based herbicides to test how these stressors interactively impact the growth of submerged macrophytes, phytoplankton and periphyton as competing primary producers. Warming or heat waves alone did not affect phytoplankton and periphyton abundance, but negatively influenced the biomass of V. denseserrulata. Nutrient loading alone increased phytoplankton biomass and water turbidity and thus negatively affected submerged macrophyte biomass, particularly for V. denseserrulata, by shading. Glyphosate alone did not affect biomass of each primary producer under ambient temperatures. However, heat waves facilitated phytoplankton growth under combined nutrient loading and glyphosate treatments more than continuous warming. As a consequence, H. verticillata biomass was lowest under these conditions indicating the potential of multiple stressors for macrophyte decline. Our study demonstrated that multiple stressors interactively alter the biomass of primary producers and their interactions and can eventually lead to a loss of macrophyte communities and shift to phytoplankton dominance. These results show the risks in shallow lakes and ponds in agricultural landscapes and underline the need for multiple stressor studies as a base for their future management.

Distribution of Glycerol Dialkyl Glycerol Tetraethers (GDGTs) in Carbonate-Type and Sulfate-Type Lacustrine Sediments: Insight into the Influence of Ionic Composition on GDGTs

The distribution of glycerol dialkyl glycerol tetraethers (GDGTs) in carbonate-type and sulfate-type saline lacustrine sediments from the Ordos Plateau in China is investigated to explore the influence of ionic composition on GDGTs. In general, they are relatively small (1.2–6.0 km2 surface area) and shallow ponds (0.05–0.2 m water depth) and even seasonally dry lakes. The results reveal that the concentration of GDGTs has a good positive correlation with the (nCO32− + nHCO3−)/total ions, and the concentration of GDGTs in carbonate-type lake sediments is significantly higher than that in sulfate-type lake sediments. Most GDGT-based indices show no significant differences, and the distributions of GDGTs are similar in the two types of saline lake sediments. The lack of a positive correlation between the content of clay minerals and the concentration of GDGTs may imply that the ability of clay minerals to carry terrigenous organic matter is very limited in arid climates. The branched GDGTS (brGDGTs) in the two saline lake sediments may mainly come from in situ biological production and have low terrestrial inputs. The different weathering level of feldspar minerals in the two types of saline lakes results in the difference in organic matter content, which ultimately affects the concentration of GDGTs.

Survival, growth and tag retention of juvenile European eel (Anguilla anguilla L.) with implanted 12 mm passive integrated transponder tags and acoustic tags.

To evaluate the efficiency of tagging juvenile European eels with implanted 12 mm passive integrated transponder (PIT) tags or Eel/Lamprey acoustic transmitters (ELATs), the authors studied tag retention, survival and growth of eels (7-25 g). Experimental eels were obtained from an eel farm, tagged and then released in a series of shallow dug-out ponds with a surface area of c. 200 m2 . Tagged and control eels were distributed evenly, with 50 tagged and 50 control eels in each of four ponds, giving a total of 200 tagged and 200 control eels mixed. After 76 days, the ponds were drained, and eels were sampled and measured. A total of 344 eels (86%) were recaptured, indicating high survival. Tag retention was 99% as only one of the recaptured PIT-tagged eels had lost the tag and none of the ELAT tagged. The results demonstrated that tagging juvenile eels >16 cm with these small tags is indeed feasible. The growth of tagged and control fish was differentiated but generally low in length and negative in mass but did not differ between the three groups.

SEASONAL DYNAMICS OF ENVIRONMENTAL VARIABLES AND ZOOPLANKTON STRUCTURE IN WASTEWATER RESERVOIRS OF THE RIGHT-BANK SORBULAK CANAL SYSTEM

The annual increase in wastewater volumes necessitates comprehensive studies of water bodies subsidized by anthropogenic activities. An example of such reservoirs is Sorbulak and a system of shallow ponds into which pre-treated wastewater from Almaty and its environs is discharged. The published works provide fragmentary data on the hydrochemical and hydrobiological regimes of Sorbulak and ponds. There is no information on the seasonal dynamics of these variables. Our paper, aimed at studying the seasonal dynamics of pollutants and the zooplankton structure, partially fills this gap. Environmental and biological samples were taken in Sorbulak and two ponds by standard methods once a month, from April to September of 2021. The content of nutrients was high, and the heavy metals concentrations, except for copper, were low. The seasonal dynamics of pollutants in reservoirs were determined mainly by their entry from wastewater, with a more negligible contribution of natural factors. Zooplankton was represented by 80 species with an average abundance of 177.3-834.4 thousand ind./m3 and average biomass of 9.6-10.4 g/m3. The values ​​of the Shannon index were 1.98-2.12 bit/ind and 0.88-1.76 bit/mg, the average mass of an individual was 0.0140-0.0853 mg. The seasonal dynamics of zooplankton in the surveyed water bodies were different. The obtained results and comparison with the data of previous studies testified to the instability of the species composition of zooplankton communities both during one year and in individual years. Contradictions between the structure of zooplankton communities and the chemical variables of the studied reservoirs were identified. The results obtained to make a theoretical and practical contribution to understanding the formation of water quality in reservoirs with mixed pollution emphasize the need for further comprehensive studies of reservoirs of this type, and show specific differences between anthropogenic and natural successions of aquatic ecosystems.

Middle Miocene (Serravallian) wetland development on the northwest edge of Europe based on palynological analysis of the uppermost Brassington Formation of Derbyshire, United Kingdom

In this paper, we describe palynological assemblages in the Middle Miocene (Serravallian) Kenslow Member of the Brassington Formation at Bees Nest Pit, near Brassington, Derbyshire, U.K., and infer vegetation types and their palaeoclimate implications. The limited lateral extent of the 1.33 m-thick succession of clay and lignite, and its position surrounding fragments of a large tree trunk, suggests that the succession may have accumulated within a tree throw hole or possibly within a shallow stagnant pond, although aquatic lacustrine palynomorphs have not been identified to confirm this latter hypothesis. The stratigraphical distribution of palynological assemblages, based on 58 samples allows reconstruction of a wetland succession. Two pollen zones were identified using CONISS cluster analysis, and a predominantly warm-temperate and mixed mesophytic forest biome was recognised with Tsuga conifer pollen-types being dominant (<42%) in both pollen zones. Changes in the make-up of this forested wetland were in response to local environmental changes rather than major climatic shifts. Wetland development culminated in the formation of a relatively open shrub and reed-dominated mire which produced the lignite-precursor peat. Applying the Co-existence Approach, Mean Annual Temperature was 15.6–21.7 °C and Mean Annual Precipitation was 703–1682 mm indicating a warm-temperate to subtropical palaeoclimate, and both parameters show no significant change through the section. Findings suggest that, following the Middle Miocene Climatic Optimum, the Serravallian climate of the northwestern margin of Europe remained much wetter than Central Europe, where more arid climates have been reconstructed, and this difference may have been due to the influence of the proto-North Atlantic Current.

Doline pond sediments reveal Late Holocene hydro-geomorphological changes in the highlands of the Pantanal, western Brazil

In the southern highlands of the Upper Paraguay River watershed, hundreds of small and shallow ponds exist, but little is known about their origins or potential to record hydroclimate signals in their sediments. Here, we present a multi-proxy evidence that reveals details about the paleolimnological evolution of these shallow tropical lakes. The available data support the conclusion that pond formation resulted from Late Holocene environmental changes that affected the regional hydro-geomorphology. Biological proxies suggest that two distinct environmental phases shaped the regional landscape. In the older phase, sponge spicules and phytoliths are absent, and the sediment geochemistry suggests that karstification processes within the subsurface helped to facilitate topographic closure and doline formation. Sediments of the younger depositional phase are characterized by abundant grass and palm phytoliths. Sponge spicules are also present in these deposits, including the freshwater species Dosilia pydanieli Volkmer-Ribeiro1992, Metania spinata (Carter, 1881), Radiospongilla amazonensis Volkmer-Ribeiro and Becker Maciel, 1983, and Tubella variabilis Bonetto and Ezcurra de Drago1973. These microfossils, especially D. pydanieli, are suggestive of perennial lentic ecosystems. The elemental geochemistry of the youngest sediments is dominated by Si, P, and S; a positive correlation between microfossil content and wt. % S may reflect a linkage between nearshore plant biomass and offshore organic sedimentation. Our results suggest an aquatic transition favoring the formation of stable doline ponds with abundant supra-littoral vegetation occurred over the last millennium, most likely the result of a wetter climate in this region of midwestern Brazil.

Thermal performance enhancement of basin-type solar still coupled with mini solar pond and shallow solar pond in closed-cycle mode

ABSTRACT Solar desalination is an appropriate and cost-effective technology for water distillation which requires solar energy as a heat source. Based on the previous studies, the effect of basin water depth of solar still coupled with shallow solar pond has not been performed yet. The optimum frequency of external heat supply to solar still during off-sunshine hours has been found missing in literature. The objective of present study is to enhance the nocturnal distillate productivity of solar still and is accomplished by increasing the basin water temperature during off-sunshine hours. The variation in basin water depth of modified solar still on the distiller output is studied. The individual and combined effects of shallow solar pond and mini solar pond integrated to solar still on the performance of still are studied. To achieve this, the solar still coupled with shallow solar pond in closed cycle mode (heat transfer through heat exchanger) and continuous flow mode (8 a.m. to 8 p.m.) are tested at various basin water depth of 4–7 cm. Further, the solar still with optimum basin water depth is integrated with shallow pond in continuous flow mode (8 a.m. to 8 p.m.) and mini pond in two-batch frequency mode (12 a.m. to 2 a.m. and 4 a.m. to 6 a.m.). A total cumulative distillate output of 3.5 kg/m2, 3.08 kg/m2, 3.18 kg/m2 and 2.96 kg/m2 with an enhancement of 2.94%, 14.5%, 20.85% and 16% was obtained for modified solar still (still integrated with shallow pond) with basin water depth of 4 cm, 5 cm, 6 cm and 7 cm respectively as compared to reference solar still. The cumulative productivity of 4.6 kg/m2 was obtained for modified still (still integrated with shallow pond and mini pond) with an enhancement of 43.75% over reference solar still.