Sandy Substrate Research Articles

Influence of ABA-metabolizing bacteria on the growth and aba content in wheat plants and soil in dense planting

The influence of abscisic acid (ABA)-metabolizing bacterial strains of the genera Pseudomonas and Arthrobacter on the hormone content in the shoots and roots of wheat plants, as well as in a sandy substrate during dense planting, has been studied. The ability of bacteria to reduce the ABA content in the growing environments and in plants, albeit to varying degrees, was discovered already 10 days after inoculation. At the same time, most of the studied strains were characterized by decrease of ABA in shoots, and suppression of ABA in the roots was observed less frequently. The simultaneous decrease in the hormone in the shoots and in the sandy substrate, which manifested itself under the influence of strains P. plecoglossicida 2.4-D, P. frederiksbergensis IB Ta10m, P. veronii IB K11-1, was accompanied by a maximum increase of wheat weight plants as compared to non-inoculated plants. The studied bacteria to varying degrees stimulated the accumulation of shoot and root mass, as well as leaf area, which could probably be associated with their different ability to synthesize other hormones, such as IAA, and/or influence the hormonal system of the plant itself. The prospects of using ABA-destructor bacteria for the development of agricultural biological products that can mitigate the negative effects of thickened crops and increase resistance to other abiotic factors are discussed.

Bargibant’s pygmy seahorse Hippocampus bargibanti in Taiwan Bank: hidden biodiversity of Taiwan Strait

During a scientific expedition in the Taiwan Bank in the southern Taiwan Strait in 2021, five pygmy seahorses, measuring between 18.1 mm and 28.3 mm in standard length, were inadvertently collected along with Muricella sea fans. Morphometric measurements of these pygmy seahorse specimens coincided with the previous data on H. bargibanti, but they had a proportionally greater head depth and snout length. Genetically, DNA marker analysis of partial mitochondrial COI sequences confirmed that our specimens belonged to the same lineage as H. bargibanti, with a p-distance of 0.54% among populations. This discovery enhances our knowledge of the limited biodiversity in the Taiwan Bank, which includes a complex geomorphology of both reef banks and sandy substrates, and highlights the importance of strict laws prohibiting fishing with inadequate gear, invasive or illegal fishing, and sand dredging to protect unexplored coral reef biodiversity in the area.

Within-lake isolation and reproductive strategy of Stuckenia pectinata (L.) Börner at Lake Naivasha (Kenya): About water level fluctuations and alien species

Submerged aquatic plants with mixed reproduction mode may show enhanced clonal growth explained by environmental conditions. For Stuckenia pectinata (L.) Börner this has been linked to within-lake factors, both biotic (tuber predation, herbivory, periphyton shading) and abiotic (hydrological connectivity, sediment type). We investigated the S. pectinata population from Lake Naivasha, where submerged aquatic plants tolerated strong historical water level fluctuations until introduced crayfish, shading by floating exotic weeds and increased turbidity nearly eradicated them, although some stands now rebounded in various lake areas. Using 13 nuclear microsatellite loci, we analyzed genetic diversity and structure of S. pectinata subpopulations along the southeastern shoreline of the main lake and inside Crescent Island Crater, a peripheral lake basin enclosed within the rim of an extinct volcano. Results revealed a predominantly sexual reproductive strategy with limited clonal expansion in the main lake contrasting with pronounced clonal growth in the crater basin. Each subpopulation experienced recent bottlenecks. Crater basin subpopulations exhibited the strongest divergence, lower clonal diversity and larger-sized clones. We explain this differentiation by the exposed crater rim acting as barrier, isolating the crater basin from the main lake during recent decades when low water levels prevailed, accompanied with less negative impact from alien species than in the main lake. Clonal extension occurred on steep-sloping hard sandy substrates, that likely prompted local reproductive adaptations. Genetic diversity, clonal structure and connectivity patterns are discussed in the light of the specific history and features of Lake Naivasha.

Identification and Analysis of the Nutrition Value of Black Teripang (Holothuriaedulis) and Sand Teripang (Holothuria Scabra) In the Waitiu Flow of Lewolema District

Indonesia is a country with a large area of ​​water, with enormous potential for marine biodiversity which is useful as food, pharmaceuticals and cosmetics. There are several marine biota that produce secondary metabolites that are beneficial to humans, including microorganisms, blue green algae, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs and sea cucumbers (echinoderms). Sea cucumbers are marine animals classified in the phylum Echinodermata, class Holothuroidea. This animal lives on sandy substrates or can be found in coral ecosystems. Sea cucumbers have complete and quite high nutritional content, but the existence of sea cucumbers with a high population in East Flores Regency has not been utilized properly. This study aims to identify and analyze the nutritional content of Sand Sea Cucumber (Holothuria Scabra) and Black Sea Cucumber (Holothuria Edulis). Identification is based on morphology and body color and spicules of the dorsal integument tissue, while the analysis of nutritional value includes water content and ash content using the gravimetric method, protein content using the Kjeldahl method, fat content using the Soxhlet method and carbohydrate content using the by difference method. The results of the study showed that the nutritional content of Sand Sea Cucumber (Holothuria Scabra) was 5.472% water content, 51.056% ash content, 27.072% protein content, 1.449% fat content and 20.424% carbohydrate content, while the nutritional content of Black Sea Cucumber (Holothuria Edulis) was 6.214% water content, 18.864% ash content, 51.636% protein content, 0.659% fat content and 28.841% carbohydrate content.

Bits and fragments: documenting an unreported coral genus Heterocyathus Milne Edwards & Haime, 1848 from northwestern Bay of Bengal (Odisha coast) and a call for further assessment

The collection of a dead specimen of the coral Heterocyathus cf. sulcatus on a sandy beach in southern Odisha highlights the importance of exploring offshore waters along this coast. The specimen was identified based on prominent taxonomic characters and association with coral boring worm. This genus was previously known to occur along the eastern coast of India, from the Gulf of Mannar/Palk Bay and off the Chennai coast. The presence of rocky offshore outcrops and a sandy substratum in the vicinity suggests that the specimen likely originated from that location.

Exploring soil pedogenesis through frequency-dependent magnetic susceptibility in varied lithological environments

AbstractThe use of percent frequency-dependent magnetic susceptibility (χfd%) is well-established for detecting superparamagnetic (SP) components in fine-grained soils and sediments. This study employs χfd% as a direct indicator of pedogenetic processes in soils from the Moroccan Rif region. Three soil transects (T1, T2, and T3), each comprising four soil cores with depths reaching 100 to 120 cm, were sampled from distinct lithological formations within an area subject to moderate to intense erosion. A total of 272 soil samples were collected and analyzed using MS2 Bartington Instruments, providing values to calculate χfd% and identify ultrafine ferrimagnetic minerals (SP, < 0.03 μm). In Quaternary fluvial terraces (T1) soils, approximately 60% of the samples indicate a mixture of SP, multidomain (MD), and Single Stable Domain (SSD) magnetic grains, while 30% contained coarser MD grains. Only 10% of the samples exhibit predominantly superparamagnetic (SP) grains. Soils on marly substrates (T2) showed 90% of samples with a combination of SP, MD, and SSD, and just 10% had SP grains. In contrast, soils from Villafranchian sandy deposits displayed χfd% values exceeding 10% in over 50% of samples, indicating that almost all iron components consist of SP grains. Physico-chemical analyses of the soils in profiles T1, T2, and T3 reveal distinct characteristics, including variations in clay content, organic matter, nutrient levels, and proportions of free and total iron. These results are important for understanding soil evolution and pedogenesis, with profiles T1 and T3 showing advanced development marked by high mineral iron, clay, and organic matter content. In contrast, profile T2 reflects a weak stage, influencing nutrient availability and contributing to overall soil dynamics in the respective profiles. The results of this study suggest that magnetic susceptibilities in these samples primarily originate from pedogenetic sources, revealing significantly advanced pedogenesis compared to T1 and T2 soils. The findings of this study align with previous research on soil erosion and degradation in the region, demonstrating that soils developed on terraces and marly substrates are more degraded and less stable than those on sandy substrates. This study underscores the utility of magnetic susceptibility as a rapid and effective indicator for initial soil assessment and gauging the degree of pedogenesis.

The community structure of recent ostracods in the Burullus lagoon, Egypt

This work concentrates on the recent ostracod community from the bottom sediments of Burullus lagoon (BuL), Egypt. It aims to identify the impacts of the environmental factors such salinity, substrate and pH on the ostracod community. Only four ostracod species are identified, Cyprideis torosa, Leptocythere castanea, Loxoconcha elliptica and Cypridopsis vidua. The results reflect the abundance of a sole tolerant species, C. torosa (79.59–100 %, with an average of 94.18 %), in all sites. Actually, this conclusion reflects the dominance of unfavorable conditions for increasing the biodiversity in the lagoon. Moreover, the associated benthic foraminiferal assemblage suffers from the rarity of species and the abundance of one tolerant species, Ammonia tepida. Therfore, there is an urgent need to understand the environmental conditions in the BuL. The measured low salinities are suitable for the survival of only brackish ostracod species. Moreover, the distribution and structure of the ostracod assemblage are mainly controlled by the type of bottom sediments. Actually, as the content of sand increases, particularly at sites near the connection to the sea, low numbers of individuals are recorded, whereas the number of living species increases in muddy substrate. Furthermore, the sites with sandy substrate display thick-walled carapaces, while the others with muddy substrate possess thin-walled carapaces. Also, the occurrence of Cypridopsis vidua is restricted only to the muddy substrate. In terms of the hydraulic conditions, the highest abundance of living species is recorded in the southern part, where the quiet conditions prevail. The lagoon water is alkaline, so pH has no observed effects on the ostracod community. Accordingly, salinity, sediment types and hydraulic conditions play the major role in controlling the abundabce, diversity and distribution of ostracods in the study area. Geographically, the identified ostracod species are broadly distributed in the brackish lagoons of the Mediterranean region.

Microbial mediated hardening of a Central Mediterranean upper shelf seafloor during the MIS 5.5; a possible post global warming scenario?

Higher sea level and sea surface temperature than at present have been inferred for the Last Interglacial (MIS 5.5, 135–116 ka), making it a good analogue for modeling the climate response of the environment to global warming in the near future. With the aim of predicting the possible evolution of some central Mediterranean shallow sandy seabeds, a MIS 5.5 biocalcarenite was investigated (Gulf of Taranto, Italy). Limited post-depositional diagenesis affected this deposit, which represents an infralittoral sandy seabed, with local vegetation and relatively high energy conditions. Medium-coarse sand sized bioclasts, with a negligible quantity of siliciclastic, compose the sediment that also hosts large shells of mollusks. Micritic cements are widespread, often in continuum with the micritized part of the shells, showing non-isopachous aphanitic and filamentous rims, aphanitic micro-mounds, vacuolar peloidal menisci, and aphanitic pore-filling matrix. All these cements consist of submicrometer anhedral or nanospheroidal crystals of low-Mg calcite, mixed with a smaller amount of irregular plate-like crystals of saponite. Micritic cements are also rich in mineralized filamentous, tubular, and subspherical bacterial bodies. This highlights the occurrence of an epilithic and endolithic microbial community forming a biofilm that stabilized the mobile sediment as consequence of the microbial mediated early cement precipitation. This led the synsedimentary hardening of some parts the mobile sandy substrate, the settlement of sessile taxa - such as Spondylus gaederopus, oysters, serpulids and barnacles, together with endofaunal organisms. Early micritic cementation is common in modern tropical climate, whereas is substantially absent in the modern Mediterranean. Consequently, its presence in the MIS 5.5 deposit confirms warmer sea water temperature compared to today (estimated at ca +2 °C) and suggests that similar hardening of mobile substrates may occur in the near future as a response to global warming.

Origin of sandy substrates controlling the distribution of open vegetation ecosystems in Amazonia

Understanding the role of open vegetation, particularly in white-sand ecosystems (WSE) and savannas, is crucial for elucidating their role in Amazonian biotic diversification. These ecosystems predominantly develop on sandy terrains, suggesting that the geological substrate significantly influences the vegetation upon it. Therefore, the interaction between landscape changes and biotic diversification is closely tied to the dynamics and resilience of these sandy substrates. Current WSE and savannas in lowland Amazonia colonized fluvial sediments deposited during the past 120 ka, with marked synchronicity over the last 23 ka, as shown by optically stimulated luminescence (OSL) and radiocarbon ages of such sandy substrates. In contrast, sandy substrates supporting open vegetation in highland areas, unsuitable for Quaternary sand accumulation, would have persisted beyond the Quaternary, as ancient sedimentary rocks in these areas are prone to developing sandy soils. The current distribution of open vegetation ecosystems in lowland Amazonia is coupled with the deposition and erosion of sandy sediments by Quaternary fluvial systems, while weathering sandy substrates in highland areas serve as long-term and resilient refugia beyond the Quaternary. The contrasting spatiotemporal dynamics of landscape changes in lowland and highland areas has implications for biodiversification or extinction events leading to current biogeography patterns in Amazonia.

Observations of avalanche–substrate interactions in the Iymek rock avalanche deposit: A possible causative mechanism

Ubiquitous and complex avalanche–substrate interactions during rock avalanche emplacement have attracted widespread attention in recent years and are regarded as vital processes influencing mobility and damage potential through rapid changes in avalanche mechanical properties. However, the fundamental interaction mechanisms of avalanche mass on substrate and the resultant effect on mobility have yet to be elucidated for natural events. To better understand the mechanics of avalanche–substrate interactions, we present a detailed study on the spectacular synsedimentary deformation structures at the bottom of the gigantic Iymek rock avalanche deposit, including undulose structures, flame structures, mixed textures, clastic dikes, and cracked gravels. The cracked gravels demonstrate that the overriding avalanche mass exited high-energy shearing on the avalanche–substrate interface, where the stress in substrate far exceeded the overburden from the avalanche mass during the avalanche–substrate interaction. Along with high-energy shearing, two different interaction modes with the change of substrate materials are identified, i.e., the Kelvin–Helmholtz instability (KHI) characterized by undulose-to-flame structure transitions, and the Raleigh–Taylor instability (RTI) characterized by the formation of clastic dikes. The KHI is interpreted as a result of the growth of shear instabilities induced by high-energy shearing along the avalanche–substrate interface. The RTI is associated with local liquefaction of the water-bearing sandy substrate and was mainly induced by the high-frequency ground vibrations generated by high-energy shearing. Therefore, we propose that the overriding avalanche mass exited high-energy shearing on the substrate during the avalanche–substrate interaction, which motivated two predominant physical processes of the KHI and RTI along the avalanche–substrate interface. The shear-induced KHI is a potential mechanism of erosion and entrainment in rock avalanches and is responsible for promoting the incorporation of substrate materials into moving avalanche mass. These results not only yield profound insights into the interaction behaviours between rock avalanches and substrates but also provide a fundamental geological prototype to motivate further modelling work to elucidate rock avalanche dynamics.

Natural regeneration of white mangrove (Laguncularia racemosa L.) during the dry season in Ejido La solución in Paraíso, Tabasco, México

Objective: To estimate the natural regeneration and growth in the sapling stage of white mangrove during the dry season. Design/methodology/approach: Measurements of the structural variables of white mangrove, diameter at breast height (DBH), height and crown diameter were made in three sampling plots. A statistical analysis was performed with the data obtained and mean data were obtained from the three sampling plots. Results: DBH data were 0.34, 0.37 and 0.42 m; height 1.34, 1.28 and 1.58 m; and crown 44.18, 38.56 and 39.83 cm, in each sampling plot respectively. Limitations on study/implications: In dry seasons, erosion can expose rocky or sandy substrates that are not suitable for mangrove growth. Findings/conclusions: The white mangrove in its sapling stage during the dry season, presented statistically significant differences in growth between sampling plots using the dasometric variables (DBH, height and crown diameter).

Using macrobenthic community structure and biotic indices to assess the ecological status of Wulan Estuary, Demak, Indonesia

Abstract. Hartati R, Widianingsih W, Zainuri M, Wardianto Y. 2024. Using macrobenthic community structure and biotic indices to assess the ecological status of Wulan Estuary, Demak, Indonesia. Biodiversitas 25: 3073-3087. Estuaries provide critical habitats for species, and they are valued commercially, recreationally, and culturally. They also filter for sediments and pollutants from rivers before entering the ocean, providing cleaner waters for marine biota. This study presents a unique approach to assessing the ecological status of an estuary using microbenthic community structure and biotic indices with a case study of Wulan Estuary, Demak District, Central Java Province, Indonesia. AZTI’s Marine Biotic Index (AMBI) community structure and biotic indices were used to assess ecological quality at eleven stations and determine the marine macrobenthic fauna's sensitivity to disturbances in two periods, i.e. August 2021 and 2022. A distinct spatial and temporal variation was evident in the macrobenthic community structure, where higher species richness and density were observed in 2022, with some species being more dominant in 2022. The trophic structure analysis showed the dominance of deposit-feeding bivalves in the fine sediments during those sampling intervals. These trophic groups, however, were dispersed less uniformly in the sandy substratum. Compared to the previous year, the density of herbivorous grazers and suspension feeders was higher in 2022. It is also shown by AMBI values that Wulan Estuary belonged to the good (slightly disturbed) to the high (undisturbed) condition, along with other biotic indices, which showed an enhanced habitat quality for benthic organisms. This result revealed the comparative ecological quality of related estuary ecosystems in Indonesia.

Investigating the effects of landscape productivity on the spatial ecology of a threatened marsupial inside feral predator exclosures

AbstractLandscape productivity and resource dispersion are key drivers of the movement patterns of many species. In less productive environments, home ranges are generally larger as individuals travel further to access resources. The greater bilby (Macrotis lagotis) has been reintroduced to several feral predator exclosures to reduce their extinction risk. Understanding how landscape productivity and resource dispersion influence bilby space use is critical to enable effective management of populations in exclosures. At two exclosures, we tested three hypotheses: 1. Bilbies would preferentially utilize habitats with sandy substrates (<20% clay content), as they are suitable for digging burrows and foraging pits; 2. Home ranges would be larger at the arid site compared to the semi‐arid site due to lower productivity and patchier distribution of preferred habitats; and 3. Bilbies would travel further each night at the arid site to access preferred habitats. Rainfall was used as an indicator of productivity, and dispersion of preferred habitats as an indicator of resource dispersion. The study was undertaken during average rainfall conditions and under similar bilby population densities at both sites. GPS loggers recorded home ranges and movements of 10 bilbies at the arid site, and 11 bilbies at the semi‐arid site. Seventeen of the 21 bilbies preferentially utilized habitats with sandy substrates, which were less abundant at the arid site. There were no significant differences in home range size or nightly movements between the sites for either sex. We suggest the average rainfall conditions at both sites, and the dietary flexibility of bilbies, supported the maintenance of relatively small and stable home ranges (particularly for females). The effects of landscape productivity and resource dispersion on bilby space use are more likely to be evident during extended periods of below average rainfall. Bilby home range studies during low rainfall conditions (e.g. drought) are required for the effective, long‐term management of exclosure populations.

Mapping marine habitats in a shallow beach-reef environment combining direct methods and hyperspectral remote sensing

Human occupation of coastal strips generates pressures that can trigger severe degradation processes in marine ecosystems and threaten human livelihoods and the sustainability of the socio-ecological system. In this context, monitoring the conservation status of algal and benthic plant communities, as the basis of coastal ecosystems, is essential for the sustainability of coastal environments. The paper presents a bionomic investigation in a shallow water beach-reef coastal system called Las Canteras, in the Canary Islands (Spain). The work aims to generate a high-resolution mapping, according to standardised rules, of the marine habitats of an area with high ecological value showing signs of severe degradation due to anthropogenic pressure. For this purpose, direct observation techniques were combined with hyperspectral remote sensing techniques. The bathymetric, sedimentological and biological data collected were combined to generate detailed mapping of 13 marine habitats according to the Spanish Inventory of Marine Habitats and Species (IEHEM by its initials in Spanish) classification system. Comparison of these results with previous studies since 1960 shows total regression of the most sensitive species of marine habitats in the Canary Islands, such as Cymodocea nodosa, as well as the decline of sandy substrates which are fundamental for maintenance of the local coastal socio-ecological system.

Komunikasi singkat: Keberadaan alga hijau koin, di Pesisir Lhok Bubon, Samatiga, Aceh Barat

This study aims to report the diversity of the Halimeda genus on the West Aceh coast. Data was collected in the Lhok Bubon Coastal intertidal area, Samatiga, West Aceh Aceh Province. Macroalgae samples were collected using the cruising method along the beach with a depth of 1-2 m at low tide. The Halimeda genus found four species, namely Halimeda macroloba, Halimeda macrophysa, Halimeda incrassata, and Halimeda simulans. Halimeda macroloba was found to have a whitish-green talus. Halimeda macrophysa samples have irregular talus branches. Description Halimeda incrassata at the study site is light green, and the holdfast is attached to the sandy substrate to form large sediment clumps. Halimeda simulans were found to be linked to sand, which tends to have a finer texture. The results of this report provide information that Lhok Bubon Beach, West Aceh, has macroalgae potential that needs further study.

Microbial mat-induced microfacies in clastic deposits – An overview

Abstract This contribution reviews microbial microfacies recognisable in vertical sections through modern or fossil mat-overgrown sediment. Microfacies are products of endobenthic or epibenthic microbial mats interacting with sediment dynamics. Laminae of such mats form during sediment dynamic quiescence by organisation of filaments to an interwoven mat fabrics (binding), and biomass enrichment (growth) by cell replication and the production of extracellular polymeric substances (EPS). Vertical sections through mat-covered sediment may show buried stacks of subrecent mat laminae (biolaminites) that rose from alternating periods of mat development and sediment deposition. Mat laminae that drape ripple marks are visible as sinoidal structures in sediment core or sections. If the sediment-stabilising properties of a microbial mat is overcome by currents or waves of high strengths, cm-size mat fragments (mat chips and roll-ups) are ripped off and redeposited. Intrasedimenary gases, trapped beneath mat layers, may cause a high secondary porosity (sponge pore sand) in the sandy substrates. The internal build-up (microfabrics) of mat laminae is investigated under high magnification. Endobenthic microbial mat fabrics include filamentous and coccoid cells forming a network, EPS, and sedimentary grains. The grains derived from interaction of the endobenthic mats with bed load. Epibenthic microbial mat fabrics may include also silt-size particles syndepositionally enriched by baffling and trapping of suspension load. The fabrics of these mats commonly also include oriented sedimentary grains. These grains (now aligned bedding parallel) were dragged upward from the substrate during the development and growth of the mat. Overall, microbial microfacies provide insight into the sedimentation pattern of the (paleo-)environment and into the types of the substrate-colonising microbial mats.

Vigna marina as a Potential Leguminous Cover Crop for High Salinity Soils

The beach bean (Vigna marina) exhibits robust growth in habitats characterised by sandy substrates, limited nutrient availability, and elevated saline levels. The utilisation of V. marina, a potentially beneficial leguminous cover crop, allows for its cultivation in regions characterised by soil salinity, hence facilitating the alleviation of environmental stress and the promotion of nitrogen fixation within the soil. A study assessed the feasibility of V. marina as a leguminous cover crop, in which this legume was cultivated in both coastal and inland soils. Pueraria javanica and Mucuna bracteata, widely recognised as established leguminous cover crops, were used as the control in this experiment. The observations involved were total plant biomass, nitrogenase activity, and leaf chlorophyll content of the host plants. The experiment consisted of five replicates arranged in a randomised complete block design, respectively. The effects of commercialised rhizobial compost on the development of the leguminous plants planted in both plots were also investigated. The results indicated that V. marina flourished in coastal and inland soils with the highest leaf chlorophyll concentration throughout the eight weeks of growth. It showed that V. marina has the potential to outperform the other two established leguminous cover crops when planted in highly salinised soils. The results also showed evidence that V. marina was an excellent potential leguminous cover crop, especially for any agricultural plots of high salinity soils, compared to the other two well-established leguminous cover crops, P. javanica and M. bracteata.

Pemetaan Sebaran Jenis Mangrove Menggunakan Citra Drone dengan Metode Object-Based Image Analysis (OBIA) di Sungai Pisang, Kecamatan Bungus Teluk Kabung, Kota Padang

This research has purpose to find out what types of mangroves and factors affect the distribution of mangroves in Sungai Pisang, Bungus Teluk Kabung District, Padang City. The research method used is quantitative research. The data used is primary data such as drone imagery. The results of this research produced seven types of mangroves and factors the distribution of mangrove types. The types of mangroves found were Rizhophora apiculate, Oncomsperma tigillarium, Ceriops tagal, Bruguiera gymnorhiza, Hibiscus tiliaceus, Acrostichum aureum linn, Sonneratia alba. Meanwhile, there are three factors that influence the distribution of mangroves, namely Substrate, Salinity and Soil Texture. The dominant substrates are muddy and sandy substrates, the lowest salinity is 12ppt and the highest is 30ppt, while the dominant soil textures are clay, clay and sandy.

The outstanding capacity of Prasiola antarctica to thrive in contrasting harsh environments relies on the constitutive protection of thylakoids and on morphological plasticity.

The determination of physiological tolerance ranges of photosynthetic species and of the biochemical mechanisms underneath are fundamental to identify target processes and metabolites that will inspire enhanced plant management and production for the future. In this context, the terrestrial green algae within the genus Prasiola represent ideal models due to their success in harsh environments (polar tundras) and their extraordinary ecological plasticity. Here we focus on the outstanding Prasiola antarctica and compare two natural populations living in very contrasting microenvironments in Antarctica: the dry sandy substrate of a beach and the rocky bed of an ephemeral freshwater stream. Specifically, we assessed their photosynthetic performance at different temperatures, reporting for the first time gnsd values in algae and changes in thylakoid metabolites in response to extreme desiccation. Stream population showed lower α-tocopherol content and thicker cell walls and thus, lower gnsd and photosynthesis. Both populations had high temperatures for optimal photosynthesis (around +20°C) and strong constitutive tolerance to freezing and desiccation. This tolerance seems to be related to the high constitutive levels of xanthophylls and of the cylindrical lipids di- and tri-galactosyldiacylglycerol in thylakoids, very likely related to the effective protection and stability of membranes. Overall, P. antarctica shows a complex battery of constitutive and plastic protective mechanisms that enable it to thrive under harsh conditions and to acclimate to very contrasting microenvironments, respectively. Some of these anatomical and biochemical adaptations may partially limit photosynthesis, but this has a great potential to rise in a context of increasing temperature.

Specific surface area and microstructure of the surface of soil solid substrates of different genesis

The sorption characteristics of sand, peat, the arable layer of Moscow urbanozem and a mixture of these substrates were studied in conjunction with the surface topography of their solid phase, studied by scanning electron microscopy (SEM). The arable layer has the greatest ability to absorb nitrogen, and the peat substrate showed very low values of the sorbed gas. A different picture of the mutual arrangement of substrate sorption isotherms is observed when water vapour is used as a sorbing gas. Peat is distinguished by high values of sorbed moisture in the entire studied range of relative humidity. This leads to differences in the ranking of substrates by specific surface area in descending order of its values. So, the specific surface area by water sorption in the series: peat / arable layer / mixture / sand was: 420 / 72 / 45 / 4 m2/g, respectively. The given surface was ranked according to nitrogen sorption in a different sequence: 8.31 / 2.41 / 1.45 / 0.55 for the series: arable layer, mixture, peat and sand, respectively. The analysis of microstructural characteristics by the SEM method at various magnifications revealed the most developed, rough surface in the arable layer. It turned out to be geometrically the most diverse, even at magnification of ×20 000. The variety and heterogeneity of the relief of the interface of the phases leads to the appearance of hysteresis of the sorption/desorption curves. Its severity in the range of nitrogen vapor concentration in which hysteresis is detected, and in the maximum width of the hysteresis loop, also turned out to be the most significant in the arable layer. The very low nitrogen specific surface of peat, which is close to a sandy substrate, is associated with the presence of organic films draping and leveling the surface of peat particles, which was revealed by analyzing images obtained by scanning electron microscopy. The sorption of water showed their high hydrophilicity, which led to high values of substrate humidity in the entire studied range of relative humidity.