Halophilic Species Research Articles

Diatoms from the Holocene sediments of lakes Pustoye and Chernoe (Nizhny Novgorod region)

The diatom analysis of the Holocene sediments of Pustoye and Chernoe lakes revealed 37 taxa of diatoms of two classes, five orders, eighteen families and twenty-five genera with a low degree of similarity of species composition (39%) and differences in the ecological priorities of the diatoms according to the leading abiotic factors – salinity and pH. Lake Chernoe is characterized by a greater number of species (26), the presence of halophilic species, as well as the prevalence of indicators of alkaline reaction of the environment. A feature of Lake Pustoye is the complete absence of halophilic forms and the predominance of species that prefer an acidic water reaction. A greater number of planktonic species was characteristic of Lake Chernoe due to the greater depths of this karst reservoir. According to the geographical location in these lakes, arcto-alpine species are noted.

Salinisation reduces biodiversity in neighbouring freshwater patches in experimental metacommunities

Abstract Aquatic ecosystems are biodiversity hot spots across many landscapes; therefore, the degradation of these habitats can lead to decreases in biodiversity across multiple scales. Salinisation is a global issue that threatens freshwater ecosystems by reducing water quality and local biodiversity. The effects of salinity on local processes have been studied extensively; however, the effects of salinisation or similar environmental stressors within a metacommunity (a dispersal network of several distinct communities) have not been explored. We tested how the spatial heterogeneity and the environmental contrast between freshwater and saline habitat patches influenced cladoceran biodiversity and species composition at local and regional scales in a metacommunity mesocosm experiment. We defined spatial heterogeneity as the proportion of freshwater to saltwater patches within the metacommunity, ranging from a freshwater‐dominated metacommunity to a saltwater‐dominated metacommunity. Environmental contrast was defined as the environmental distance between habitat patches along the salinity gradient in which low‐contrast metacommunities consisted of freshwater and low‐salinity patches and high‐contrast metacommunities consisted of freshwater and high‐salinity patches. We hypothesised that the α‐richness of freshwater patches and metacommunity γ‐richness would decrease as freshwater patches became less abundant along the spatial heterogeneity gradient in both low‐ and high‐contrast metacommunities, because there would be fewer freshwater patches that could serve as source populations for declining populations. We hypothesised that low‐contrast metacommunities would support more species across the spatial heterogeneity gradient than high‐contrast metacommunities, because, via dispersal, low‐salinity patches can support halotolerant freshwater species that can mitigate population declines in neighbouring freshwater patches, whereas` high‐salinity patches will mostly support halophilic species, providing fewer potential colonisers to freshwater patches. We found that α‐richness of freshwater mesocosms and metacommunity γ‐richness declined in saline‐dominated metacommunities regardless of the environmental contrast between the freshwater and saline mesocosms. We found that environmental contrast influenced freshwater and saline community composition in low‐contrast metacommunities by increasing the abundances of species that could tolerate low‐salinity environments through dispersal, whereas freshwater and high‐salinity communities showed limited interactions through dispersal. Freshwater mesocosms had a disproportionate effect on the local and regional biodiversity in these experimental metacommunities, indicating that habitat identity may be more important than habitat diversity for maintaining biodiversity in some metacommunities. This study further emphasises the importance in maintaining multiple species‐rich habitat patches across landscapes, particularly those experiencing landscape‐wide habitat degradation.

Comparative Genomics and Phylogenomic Analysis of the Genus Salinivibrio.

In the genomic era phylogenetic relationship among prokaryotes can be inferred from the core orthologous genes (OGs) or proteins in order to elucidate their evolutionary history and current taxonomy should benefits of that. The genus Salinivibrio belongs to the family Vibrionaceae and currently includes only five halophilic species, in spite the fact that new strains are very frequently isolated from hypersaline environments. Species belonging to this genus have undergone several reclassifications and, moreover, there are many strains of Salinivibrio with available genomes which have not been affiliated to the existing species or have been wrongly designated. Therefore, a phylogenetic study using the available genomic information is necessary to clarify the relationships of existing strains within this genus and to review their taxonomic affiliation. For that purpose, we have also sequenced the first complete genome of a Salinivibrio species, Salinivibrio kushneri AL184T, which was employed as a reference to order the contigs of the draft genomes of the type strains of the current species of this genus, as well as to perform a comparative analysis with all the other available Salinivibrio sp. genomes. The genome of S. kushneri AL184T was assembled in two circular chromosomes (with sizes of 2.84 Mb and 0.60 Mb, respectively), as typically occurs in members of the family Vibrionaceae, with nine complete ribosomal operons, which might explain the fast growing rate of salinivibrios cultured under laboratory conditions. Synteny analysis among the type strains of the genus revealed a high level of genomic conservation in both chromosomes, which allow us to hypothesize a slow speciation process or homogenization events taking place in this group of microorganisms to be tested experimentally in the future. Phylogenomic and orthologous average nucleotide identity (OrthoANI)/average amino acid identity (AAI) analyses also evidenced the elevated level of genetic relatedness within members of this genus and allowed to group all the Salinivibrio strains with available genomes in seven separated species. Genome-scale attribute study of the salinivibrios identified traits related to polar flagellum, facultatively anaerobic growth and osmotic response, in accordance to the phenotypic features described for species of this genus.

Correction to: Aspergillus loretoensis, a single isolate from marine sediment of Loreto Bay, Baja California Sur, México resulting as a new obligate halophile species.

In the original publication the Figs.3 and 4 are published inappropriately. The correct version of Figs.3 and 4 is provided in this correction.

Marine Fungi: Biotechnological Perspectives from Deep-Hypersaline Anoxic Basins

Deep-sea hypersaline anoxic basins (DHABs) are one of the most hostile environments on Earth. Even though DHABs have hypersaline conditions, anoxia and high hydrostatic pressure, they host incredible microbial biodiversity. Among eukaryotes inhabiting these systems, recent studies demonstrated that fungi are a quantitatively relevant component. Here, fungi can benefit from the accumulation of large amounts of organic material. Marine fungi are also known to produce bioactive molecules. In particular, halophilic and halotolerant fungi are a reservoir of enzymes and secondary metabolites with valuable applications in industrial, pharmaceutical, and environmental biotechnology. Here we report that among the fungal taxa identified from the Mediterranean and Red Sea DHABs, halotolerant halophilic species belonging to the genera Aspergillus and Penicillium can be used or screened for enzymes and bioactive molecules. Fungi living in DHABs can extend our knowledge about the limits of life, and the discovery of new species and molecules from these environments can have high biotechnological potential.

Aspergillus loretoensis, a single isolate from marine sediment of Loreto Bay, Baja California Sur, México resulting as a new obligate halophile species

An obligate halophile fungal was isolated from 275m deep marine sediments and is characterized here for the first time. Its optimal growth was at 15% NaCl even though it was able to grow at 25% and is incapable of growth with no NaCl. Based on its morphological characteristics as conidia chain production in a single phialide, the fungal is related to the genus Aspergillus, subgenus Polypaecilum. Phylogenetic molecular analysis using several markers (ITS1-2; RPB1; RPB2; Cct8; TSR1; CaM; BenA) places the fungal isolate closer to Aspergillus salinarus and A. baarnensis. However, its morphological and molecular differences establish it as a new species, Aspergillus loretoensis sp. nov.

Distribution of С4 Plants of the Chenopodiaceae Family According to the Salinization Profile of the Kyzylkum Desert

The peculiarities of the prevalence of C4 species in the relief of the Kyzylkum Desert were revealed based on botanical and geographical descriptions. In the lowlands (0–50 m above sea level), a predominance of C3 halophytes was found, while halophytes with C4 photosynthesis began to predominate at medium elevations (50–200 m above sea level). Above 200 m above sea level, a sharp decline in the contribution of halophilic flora to the biodiversity of native vegetation was detected. Thus, the penetration of halophytes above 200 m is limited by the presence of C4 photosynthesis as an adaptive characteristic to soil desalinization. A decrease in the succulence of leaf morphology in edificatory perennial plants of the Kyzylkum Desert (tamarix, saxaul, and camel thorn) was noted with a decrease in soil salinization. In the summer dry period, C4 photosynthesis provides a competitive advantage over C3 halophytes for survival on desalinated soils of elevated parts of the terrain desiccated during the summer. It was concluded that the acquisition of C4 photosynthesis by halophilic species is an adaptation of the photosynthesis of halophilic flora to seasonal desalinization and drying of the soil of the elevated parts of the Kyzylkum Desert.

ANTIOXIDANT ACTIVITY OF HALOPHILA OVALIS AND HALOPHILA BECCARII (HYDROCHARITACEAE): TWO IMPORTANT SEAGRASS SPECIES OF CHILIKA LAGOON, INDIA

Objective: The present study was undertaken to evaluate the total phenolic and flavonoid content and the antioxidant property of two important seagrass species namely, Halophila ovalis and Halophila beccarii occurring in Chilika lagoon, Odisha, India.
 Methods: Total Phenolic Content (TPC) of the extracts of Halophila species was determined by Folin-Ciocalteu method with little modifications and the total flavonoid content (TFC) was measured by aluminum chloride colorimetric assay. The antioxidant activity of different extracts was investigated by DPPH and ABTS radical scavenging activity. IC50 values were calculated for the DPPH and ABTS methods.
 Result: The study revealed that the methanol extract of H. ovalis has greater antioxidant activity than H. beccarii. Methanol extract of both the species (H. ovalis and H. beccarii) was found to possess high phenolic content at value of 70.25 mg GAE/g of extract and 48.53 mg GAE/g of extract respectively. Similarly flavonoid contents was found highest in methanol extract for both H. ovalis (76.82 mg quercetin equivalent/ g of extract) and H. beccarii (64.28 mg quercetin equivalent/ g of extract). The antioxidant activity of different extracts of these two species were evaluated using DPPH and ABTS radical assay. The methanol extract of both H. ovalis and H. beccarii showed high radical scavenging activity with IC50 values of 37.77 μg/ml and 52.25 μg/ml for DPPH and 25.62 μg/ml and 45.45 μg/ml for ABTS respectively.
 Conclusion: The study revealed the potential of the Halophila species as natural sources of antioxidants having considerable commercial importance.

Structural Variables Of Macrozoobenthos During Stabilization And Increase Of The Small Aral Seas Level (1996-2008)

The purpose of this work was to study the macrozoobenthos of the Small Aral Sea in the period from 1996 to 2008, which was characterized by stabilization and then by a steady increase in the water level and decrease in water salinity. Samples of macrozoobenthos were taken in the Small Aral Sea using a grid of 20 stations. During the study period, the average salinity of water varied from 6.3% to 19.0%. 10 taxa were identified in the benthic community. The average annual abundance of macrozoobenthos was 1962 species/m2, with its biomass at 83.3 g/m2. Quantitative variables of the community were primarily formed by polychaete Hediste diversicolor, mollusks Abra ovata, Caspiohydrobia sp. and Cerastoderma isthmicum. During the period of study, abundance and biomass of macrozoobenthos decreased by an order of magnitude from 4274 to 641 species/m2 and from 206.0 to 20.6 g/m2 , respectively. The average values of the Shannon index - 1.20 bits/specimen and 0.92 bits/mg, were characteristic of a low diversity of benthic cenosis. Evidently, the water salinity had a positive effect on the long-term dynamics of macrozoobenthos biomass. The observed decrease in the quantitative variables of macrozoobenthos during desalination of the Small Aral Sea is not only due to the deterioration of hydrochemical conditions for marine and halophilic species, but also to the increased pressure on the benthic fauna caused by fish.

Genome analysis provides insights into crude oil degradation and biosurfactant production by extremely halotolerant Halomonas desertis G11 isolated from Chott El-Djerid salt-lake in Tunisian desert

Here, we report the genomic features and the bioremediation potential of Halomonas desertis G11, a new halophilic species which uses crude oil as a carbon and energy source and displays intrinsic resistance to salt stress conditions (optimum growth at 10% NaCl). G11 genome (3.96 Mb) had a mean GC content of 57.82%, 3622 coding sequences, 480 subsystems and 64 RNA genes. Annotation predicted 38 genes involved in osmotic stress including the biosynthesis of osmoprotectants glycine-betaine, ectoine and osmoregulated periplasmic glucans. Genome analysis revealed also the versatility of the strain for emulsifying crude oil and metabolizing hydrocarbons. The ability of G11 to degrade crude oil components and to secrete a glycolipid biosurfactant with satisfying properties was experimentally confirmed and validated. Our results help to explain the exceptional capacity of G11 to survive at extreme desertic conditions, and highlight the metabolic features of this organism that has biotechnological and ecological potentialities.

Effect of Lead Nitrate on Morphological and Biochemical Parameters of Atriplex Halimus L.

Soil pollution is one of the main environmental stresses due to the effect of various contaminations by heavy metals like lead. The aim of this study is to examine the response of a halophile species Atriplex halimus L. under lead stress. This plant is watered from the germination stage with different concentrations of lead nitrate Pb(NO3)2 1000, 3000, 5000 and 7000 ppm for 100 days. The response of plants is evaluated by an analysis of the growth mass parameters (fresh and dry weight) and biochemical parameters (chlorophyllian pigments, proline and total proteins). The results reveal a growth inhibition of the aerial and root parts by Pb(NO3)2 treatment compared to control. On the other hand, the biochemical response indicates that the amount of chlorophyll pigments reduced by the effect of different treatment of lead. In contrast, proline and total proteins contents increased in leaves and roots of Atriplex halimus L. as a response to stress.

Salt in stools is associated with obesity, gut halophilic microbiota and Akkermansia muciniphila depletion in humans.

High salt intake has been linked to several diseases including obesity and an increased risk of death; however, fecal salinity and the ability of salt to alter the gut microbiota, which was recently identified as an instrumental factor for health and disease, remains poorly explored. We analyzed the fecal samples of 1326 human individuals for salinity by refractometry, 572 for gut microbiota by culturomics, and 164 by 16S rRNA-targeted metagenomics. Geographical origin, age, gender, and obesity were tested as predictors of fecal salinity and halophilic diversity. All halophilic isolates were characterized by taxonogenomics and their genome sequenced. Fecal salinity was associated with obesity independently of geographical origin, gender, and age. The first 2 human-associated halophilic archaeal members were isolated along with 64 distinct halophilic species, including 21 new species and 41 known in the environment but not in humans. No halophiles grow in less than 1.5% salinity. Above this threshold, the richness of the halophilic microbiota was correlated with fecal salinity (r = 0.58, p < 0.0001). 16S metagenomics linked high fecal salinity to decreased diversity (linear regression, p < .035) and a depletion in anti-obesity Akkermansia muciniphila and Bifidobacterium, specifically B. longum and B. adolescentis. Genomics analysis suggested that halophilic microbes are not only transient passengers but may be residents of the human gut. High salt levels are associated with alteration of the gut microbial ecosystem and halophilic microbiota, as discovered during this study. Further studies should clarify if the gut microbiota alterations associated with high salt levels and the human halophilic microbiota could be causally related to human disease, such as obesity.

Cheese brines from Danish dairies reveal a complex microbiota comprising several halotolerant bacteria and yeasts

The Danish Danbo cheese is a surface ripened semi-hard cheese, which before ripening is submerged in brine for up to 24 h. The brining is required in order to obtain the structural and organoleptic properties of the cheeses. Likewise, the content of NaCl in the cheese will influence especially the surface microbiota being of significant importance for flavour development and prevention of microbial spoilage. Even though the microbiota on cheese surfaces have been studied extensively, limited knowledge is available on the occurrence of microorganisms in cheese brine. The aim of the present study was to investigate by both culture-dependent and -independent techniques the brine microbiota in four Danish dairies producing Danbo cheese. The pH of the brines varied from 5.1 to 5.6 with a dry matter content from 20 to 27% (w/w). The content of lactate varied from 4.1 to 10.8 g/L and free amino acids from 65 to 224 mg/L. Bacteria were isolated on five different media with NaCl contents of 0.85–23.0% (w/v) NaCl. The highest count of 6.3 log CFU/mL was obtained on TSA added 4% (w/v) NaCl. For yeasts, the highest count was 3.7 log CFU/mL on MYGP added 8% (w/v) NaCl. A total of 31 bacterial and eight eukaryotic species were isolated including several halotolerant and/or halophilic species. Among bacteria, counts of ≥6.0 log CFU/mL were obtained for Tetragenococcus muriaticus and Psychrobacter celer, while counts between ≥4.5 and < 6.0 log CFU/mL were obtained for Lactococcus lactis, Staphylococcus equorum, Staphylococcus hominis, Chromohalobacter beijerinckii, Chromohalobacter japonicus and Microbacterium maritypicum. Among yeasts, counts of ≥3.5 log CFU/mL were only obtained for Debaryomyces hansenii. By amplicon-based high-throughput sequencing of 16S rRNA gene and ITS2 regions for bacteria and eukaryotes respectively, brines from the same dairy clustered together indicating the uniqueness of the dairy brine microbiota. To a great extent the results obtained by amplicon sequencing fitted with the culture-dependent technique though each of the two methodologies identified unique genera/species. Dairy brine handling procedures as e.g. microfiltration were found to influence the brine microbiota. The current study proves the occurrence of a specific dairy brine microbiota including several halotolerant and/or halophilic species most likely of sea salt origin. The importance of these species during especially the initial stages of cheese ripening and their influence on cheese quality and safety need to be investigated. Likewise, optimised brine handling procedures and microbial cultures are required to ensure an optimal brine microbiota.

Genome Sequence of the Halophilic Bacterium Kangiella spongicola ATCC BAA-2076T.

The Gram-negative genus Kangiella contains a number of halophilic species that display high levels of iso-branched fatty acids. Kangiella spongicola was isolated from a marine sponge, Chondrilla nucula, from the Florida Keys in the United States. A genome assembly of 2,825,399 bp with a 44.31% G+C content was generated from strain A79T (=ATCC BAA-2076T).

A New Halophilic Heterolobosean Flagellate, Aurem hypersalina gen. n. et sp. n., Closely Related to the Pleurostomum-Tulamoeba Clade: Implications for Adaptive Radiation of Halophilic Eukaryotes.

Halophilic protozoa are independently scattered across the molecular phylogeny of eukaryotes; most of which are assigned to Heterolobosea. Here, we isolated a biflagellate from a hypersaline water of 342‰ salinity. This isolate shared several morphological features with typical halophilic heterolobosean flagellates. In addition, molecular phylogenetic trees of the 18S rRNA gene sequences clearly indicated flagellate is a heterolobosean species closely related to the halophilic Tulamoebidae. However, the flagellate was not accommodated to any described genus. Cells were ovoid-shaped, and no amoebae were observed. The two unequal flagella beat heterodynamically. An ear-like bulge at the margin of a cytostomal groove was observed. Flagellates could grow at 100-200‰ salinity, suggesting an obligately halophilic species. Currently, it appears that the new halophilic Aurem hypersalina forms a strong clade with Tulamoebidae, and is sister to the Tulamoebidae, indicating that this new clade is composed almost entirely of obligate halophilic taxa. Thus, A.hypersalina and the Tulamoebidae clade currently represent a unique adaptive radiation of halophilic eukaryotes.

Refinery and concentration of nutrients from urine with electrodialysis enabled by upstream precipitation and nitrification

Human urine is a valuable resource for nutrient recovery, given its high levels of nitrogen, phosphorus and potassium, but the compositional complexity of urine presents a challenge for an energy-efficient concentration and refinery of nutrients. In this study, a pilot installation combining precipitation, nitrification and electrodialysis (ED), designed for one person equivalent (1.2 Lurine d−1), was continuously operated for ∼7 months. First, NaOH addition yielded calcium and magnesium precipitation, preventing scaling in ED. Second, a moving bed biofilm reactor oxidized organics, preventing downstream biofouling, and yielded complete nitrification on diluted urine (20–40%, i.e. dilution factors 5 and 2.5) at an average loading rate of 215 mg N L−1 d−1. Batch tests demonstrated the halotolerance of the nitrifying community, with nitrification rates not affected up to an electrical conductivity of 40 mS cm−1 and gradually decreasing, yet ongoing, activity up to 96 mS cm−1 at 18% of the maximum rate. Next-generation 16S rRNA gene amplicon sequencing revealed that switching from a synthetic influent to real urine induced a profound shift in microbial community and that the AOB community was dominated by halophilic species closely related to Nitrosomonas aestuarii and Nitrosomonas marina. Third, nitrate, phosphate and potassium in the filtered (0.1 μm) bioreactor effluent were concentrated by factors 4.3, 2.6 and 4.6, respectively, with ED. Doubling the urine concentration from 20% to 40% further increased the ED recovery efficiency by ∼10%. Batch experiments at pH 6, 7 and 8 indicated a more efficient phosphate transport to the concentrate at pH 7. The newly proposed three-stage strategy opens up opportunities for energy- and chemical-efficient nutrient recovery from urine. Precipitation and nitrification enabled the long-term continuous operation of ED on fresh urine requiring minimal maintenance, which has, to the best of our knowledge, never been achieved before.

ADP-Dependent Kinases From the Archaeal Order Methanosarcinales Adapt to Salt by a Non-canonical Evolutionarily Conserved Strategy.

Halophilic organisms inhabit hypersaline environments where the extreme ionic conditions and osmotic pressure have driven the evolution of molecular adaptation mechanisms. Understanding such mechanisms is limited by the common difficulties encountered in cultivating such organisms. Within the Euryarchaeota, for example, only the Halobacteria and the order Methanosarcinales include readily cultivable halophilic species. Furthermore, only the former have been extensively studied in terms of their component proteins. Here, in order to redress this imbalance, we investigate the halophilic adaptation of glycolytic enzymes from the ADP-dependent phosphofructokinase/glucokinase family (ADP-PFK/GK) derived from organisms of the order Methanosarcinales. Structural analysis of proteins from non-halophilic and halophilic Methanosarcinales shows an almost identical composition and distribution of amino acids on both the surface and within the core. However, these differ from those observed in Halobacteria or Eukarya. Proteins from Methanosarcinales display a remarkable increase in surface lysine content and have no reduction to the hydrophobic core, contrary to the features ubiquitously observed in Halobacteria and which are thought to be the main features responsible for their halophilic properties. Biochemical characterization of recombinant ADP-PFK/GK from M. evestigatum (halophilic) and M. mazei (non-halophilic) shows the activity of both these extant enzymes to be only moderately inhibited by salt. Nonetheless, its activity over time is notoriously stabilized by salt. Furthermore, glycine betaine has a protective effect against KCl inhibition and enhances the thermal stability of both enzymes. The resurrection of the last common ancestor of ADP-PFK/GK from Methanosarcinales shows that the ancestral enzyme displays an extremely high salt tolerance and thermal stability. Structure determination of the ancestral protein reveals unique traits such as an increase in the Lys and Glu content at the protein surface and yet no reduction to the volume of the hydrophobic core. Our results suggest that the halophilic character is an ancient trait in the evolution of this protein family and that proteins from Methanosarcinales have adapted to highly saline environments by a non-canonical strategy, different from that currently proposed for Halobacteria. These results open up new avenues for the search and development of novel salt tolerant biocatalysts.

The Genus Wallemia-From Contamination of Food to Health Threat.

The fungal genus Wallemia of the order Wallemiales (Wallemiomycotina, Basidiomycota) comprises the most xerotolerant, xerophilic and also halophilic species worldwide. Wallemia spp. are found in various osmotically challenged environments, such as dry, salted, or highly sugared foods, dry feed, hypersaline waters of solar salterns, salt crystals, indoor and outdoor air, and agriculture aerosols. Recently, eight species were recognized for the genus Wallemia, among which four are commonly associated with foods: W. sebi, W. mellicola, W. muriae and W. ichthyophaga. To date, only strains of W. sebi, W. mellicola and W. muriae have been reported to be related to human health problems, as either allergological conditions (e.g., farmer’s lung disease) or rare subcutaneous/cutaneous infections. Therefore, this allergological and infective potential, together with the toxins that the majority of Wallemia spp. produce even under saline conditions, defines these fungi as filamentous food-borne pathogenic fungi.

Karyomorphology and DNA quantification in the marine angiosperm Halophila stipulacea (Forsskål) Ascherson from Mediterranean and Red Seas

Cytogenetic studies for systematic and evolutionary purposes are lacking on marine phanerogams. Halophila stipulacea is a tropical seagrass that invaded the Mediterranean from the Red Sea through the Suez Canal. In this study, we report, for the first time, the karyotype features and genome size of H. stipulacea populations from different localities. Also, an attempt to compare our data with those reported in literature on other Halophila species is discussed. To determine the karyological relationships among taxa, we used basic karyotypic features such as chromosome number, size and symmetry, and position of chromosomal landmarks. To estimate karyotype asymmetry, the Coefficient of Variation of Chromosome Length (CVCL) and the Mean Centromeric Asymmetry (MCA) values were calculated. The estimations of DNA amounts were carried out by Image Cytometry (IC) using the interphase-peak method. All the taxa, including those reported in literature, present a uniform and slightly bimodal karyotype, but significant differences are found in nuclear DNA content among species. Each taxa had a karyotype formula 2n = 18 = 10m + 2sm + 6st. Aneuploidy and polyploidy seemed to not be involved in the speciation of this genus. The conserved karyotype in these taxa suggests the presence of mechanisms selecting for constancy, or against changes, in karyotype number and morphology.

Wetland Plant Diversity in a Coastal Nature Reserve in Italy: Relationships with Salinization and Eutrophication and Implications for Nature Conservation

Wetlands are important centers of biodiversity. Coastal wetlands are subject to anthropogenic threats that can lead to biodiversity loss and consequent negative effects on nature conservation. We investigated relationships between wetland vegetation and habitat conditions in a coastal Nature Reserve in Northern Italy that has undergone seawater intrusion and eutrophication for several decades. The wetland vegetation in the Nature Reserve consisted of nine communities of hygrophytic and helophytic vegetation and five communities of waterplant vegetation. The hygrophytic and helophytic communities were arranged according to a salinity gradient, from salt-free habitats to strongly saline habitats. The saline habitats had high nutrient levels, due to the influx of nitrate-rich saltwater from an adjacent lagoon. The waterplant communities were all typical of freshwater habitats. Water-table depth and concentration of dissolved nutrients in the water were the main factors structuring waterplant vegetation. The main driver of future changes in the wetland vegetation of the Nature Reserve is the ongoing increase in salinity levels which may enhance expansion of halophilic species and communities, thus outcompeting locally rare freshwater species. If nutrient, especially nitrate, load further increases in the next future, this may exert negative effects on wetland species and communities preferring nutrient-poor habitats.