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In the sediments of seagrass meadows, allochthonous carbon sources can account for 50–90% of sediment organic carbon (SOC), in which non-seagrass carbon is derived from external organic matter advected into the meadow's sediments or trapped by the seagrass canopy. Identifying the SOC origin is essential to accurately estimate the climate change mitigation potential of seagrass ecosystems, yet the ratio of allochthonous to autochthonous SOC in South African seagrass populations has not been investigated. In this study, we measured the SOC and carbon isotope ratio (δ13C) in Zostera capensis seagrass meadows in the Berg River and Breede River estuaries and applied Bayesian mixing models to disentangle the SOC contributory sources. Sediment organic carbon differed not only between estuaries, but also showed variability within each estuary, with autochthonous carbon accounting for between ∼35% (SD 0.23) and ∼42.3% (SD 0.18) of total meadow SOC. Other sources of SOC included macroalgae, salt marsh and seagrass species. Our work highlights the importance of accounting for allochthonous carbon in disentangling the drivers of high variability of carbon stocks in estuarine environments and contributes to improving the accuracy of South African seagrass carbon stock estimates. [ABSTRACT FROM AUTHOR]

Estuaries along with their saltmarshes are extremely relevant areas to what ecosystems conservation is concerned. Not only do they provide unique conditions to house numerous species but can also play an important role in pollution mitigation. This study aimed to evaluate the role of saltmarsh plants in metals retention in the long term, using a previously monitored estuary as a case study (Lima river estuary). Seasonal sampling campaigns were carried out in 2022 to determine the metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations in vegetated and non-vegetated sediments, as well as in saltmarsh plants at three sites within the estuarine area, Canogem, Salinas and Srª das Areias. Results showed saltmarsh plants, despite some seasonal variability, are concentrating metals in their rhizosediments (ratio metal in vegetated sediment / metal in non-vegetated sediment >1) and in their roots, namely Cd, Cu and Zn (ratio metal in plant roots / metal in non-vegetated sediment >1). This role seems to be maintained in the long term, with plant metal retention levels similar in 2009 and 2022, indicating plants are probably contributing to remove metals from the surface water. However, this feature seems to be decreasing in one of the sites, Srª das Areias, that shows signs of degradation. Thus, saltmarsh plants have the potential to retain metals in estuarine areas, contributing to reduce metals present in the aquatic environment and preventing them from spreading through the estuarine area, from reaching coastal areas and eventually from reaching underlying aquifers. Protection of this environment is mandatory and the promotion of re-vegetation of non-vegetated estuarine areas is needed so that the saltmarsh works as a nature-based solution that prevents and/or recovers impacted environments, in order that saltmarshes can continue to deliver their multiple co-benefits.

Seagrass habitats provide structural complexity in coastal estuarine and marine environments, which offer fish optimal foraging grounds and refuge from predation. However, seagrasses are some of the most threatened ecosystems globally, with anthropogenic activities such as population growth and environmental degradation leading to the fragmentation, thinning, and loss of these habitats. Rhabdosargus holubi is one of only a few vegetation‐associated marine fish species in South African estuaries. Although field studies have shown a strong association with seagrass over other aquatic vegetation for the juveniles of this species, habitat choice has never been empirically tested. Here, we used artificial vegetation units to test habitat choice (different structural complexities) for this species. We also tested whether habitat choice is influenced by a predatory threat, with fish preferentially selecting dense habitat in the presence of a predator and whether this effect may be more apparent in smaller individuals. We found that R. holubi significantly prefer greater structural complexity over less complex habitats, in both the absence and presence of a predator and for both small and large juveniles, showing that R. holubi actively choose more complex structures and are attracted to the structure per se irrespective of the threat of predation. This study highlights the importance of dense seagrass as nursery areas for this species and demonstrates how the loss of these habitats could impact the nursery function of estuaries. [ABSTRACT FROM AUTHOR]

• Spartina maritima spikelets with non-exerted stamens increase with increasing air temperature • Fruit set decreases with increasing air temperature and sediment anoxia • Caryopsis resorption increases with temperature warming in female phase • Caryopsis resorption increases with tidal amplitude in male phase • Global warming severely limits sexual reproduction of threatened S. maritima Sexual reproduction, a critical life history process in plants, can be altered by heat stress derived from global warming. Sexual reproduction increases genetic diversity, and the ability of plants to respond to environmental changes and dispersal. The capacity for these responses is especially relevant as plants are exposed to rising environmental stress levels imposed by climate change. We investigated the influence of environmental factors that impose physiological stress that may affect the fruit set of Spartina maritima , the sole native African and European cordgrass species. To achieve our objective, we acquired locally recorded air temperatures and tidal amplitude projections. Within population sites, we measured sedimentary conditions (pH, redox potential and electrical conductivity), and the phenological stage of S. maritima inflorescences, spikelets with non-exserted stamens and caryopses produced throughout its 10-week flowering period. Fruit set decreased as flowering period advanced, and as air temperatures and the proportion of spikelets with non-exserted stamens increased. Fruit set decreased with increased sediment anoxia. The proportion of reabsorbed caryopses increased with high air temperatures during the female phase of the inflorescence, and with higher tidal amplitudes during the male phase. These environmental stress factors could terminate caryopsis development that had commenced. Our results point to a severe potential impact of global warming on the reproductive process of native S. maritima. Mitigation of global warming will be essential to maintain population persistence and support conservation and recovery of this halophyte that provides important ecosystem services in salt marshes. [ABSTRACT FROM AUTHOR]

Sea-level rise is a significant threat to salt marshes. However, these habitats can respond by increasing their relative elevation, or by migrating into adjacent areas. Here we provide the first report on surface elevation change for salt marsh at the Knysna Estuary, South Africa, and predict the responses of these habitats to sea-level rise using the Sea-Level Affecting Marshes Model (SLAMM). Recent (2018) surface elevation measurements at lower intertidal salt marsh sites were compared with those from 2009–2011. The long-term (1960–2017) relative sea-level rise (RSLR) was estimated as 2.19 mm y−1 and only two of the seven sites assessed are keeping pace with this RSLR. The SLAMM, which was applied to a focus area near Thesen's Island, predicted up to 40% loss of upper intertidal salt marsh by 2100, because development in the adjacent area prevents habitat migration. Currently, salt marsh habitats cover a total of 667 ha, and artificial structures are present along 20.7 km of the perimeter. Protecting areas for salt marsh migration should be a conservation priority, because this estuary supports the third largest area of intertidal salt marsh in the country. Monitoring the responses of coastal wetlands should be prioritised so that natural capital contributes towards future resilience. [ABSTRACT FROM AUTHOR]

The phenolic content of Spartina maritima was investigated using chromatographic and spectroscopic techniques. Aqueous methanolic extracts were prepared from plant collected in different seasons in the Bay of Arcachon (French Atlantic coast). High performance liquid chromatography (HPLC) with diode array detection (DAD) coupled with mass spectrometry allowed identification of four major phenolics in the aerial tissue, all belonging to the C-glycosidic-flavonoid class. They were isolated from the crude extracts, and their structures were assigned to isovitexin, isoscoparin and their respective 2″-O-glucosides on the basis of NMR, mass and UV spectroscopies. The seasonal variation of the flavonoid content was quantified over the period January 2013 to May 2015. The total concentration found ranged from 1.73 to 4.60 mg g−1 dry wt for isovitexin derivatives, and 0.88–2.66 mg g−1 dry wt for isoscoparin derivatives. The phenolic content of the rhizomes was very low and mainly dominated by coumaric acid (0.03–0.08 mg g−1), along with ferulic acid (≤0.06 mg g−1). The lack of significant concentrations of flavonoids in the rhizome contrasts with the aerial tissue. This work constitutes the first phenolic profiling of S. maritima and should provide a foundation for further studies, considering the reported biological activities of C-glycosidic flavonoids, and the lack of knowledge of the phenolic chemistry of the genus Spartina. [ABSTRACT FROM AUTHOR]

Questions: Invasiveness depends in part on the ability of exotic species to either exclude native dominants or to fill an empty niche. Comparisons of niches and effects of closely related native and invasive species enable the investigation of this topic. Does Spartina anglica invade European salt marshes through competitive exclusion of the native Spartina maritima or due to the occurrence of an empty ecological niche in highly anoxic conditions? Study Site: The Arcachon Bay (France). Methods: At three intertidal levels, we quantified competitive response and effect abilities of the two species through a cross‐transplantation removal experiment. We also compared the biomass, root/shoot ratio, productivity and environmental conditions (elevation, salinity, redox potential and soil moisture) of salt marsh communities dominated by the exotic Spartina anglica or the native Spartina maritima at three intertidal levels. Results: Both established species showed similar biotic resistance to the invasion of the other species, but the exotic showed important intraspecific facilitation for growth. Species had similar niches and total biomass along a gradient of anoxic conditions, but the exotic had a much higher root/shoot ratio and productivity than the native. Owing to its rhizome density, the exotic showed high ability to increase sediment oxygenation, likely to explain its important intraspecific facilitation. Conclusions: Our results showed that the invasion success of S. anglica cannot be explained by the competitive exclusion of the native or by its ability to fill an empty niche along a gradient of anoxia. Its behaviour as a self‐facilitator invasive engineer very likely explains its rapid spread in the Bay and biotic resistance to the colonization of other congeneric species when established in dense patches. Additionally, we suggest that physical disturbance in marsh communities dominated by the native S. maritima may disrupt its biotic resistance against the invasion of S. anglica. With a cross‐transplantation removal experiment, we have assessed the competitive effects and responses of two Spartina species in a European salt marsh. We showed that the native Spartina maritima had a strong biotic resistance to the invasion of Spartina anglica. However, once installed, the exotic Spartina anglica exhibited a self‐facilitating behaviour and strong competitive ability that favoured its spread. [ABSTRACT FROM AUTHOR]

The present study aims to unravel ecophysiological mechanisms underlying plant-microbe interactions under natural abiotic stress conditions, specifically heavy metal pollution. Effect of plant growth promoting rhizobacteria (PGPR) bioaugmentation on Spartina maritima in vivo root respiration and oxidative stress was investigated. This autochthonous plant is a heavy metal hyperaccumulator cordgrass growing in one of the most polluted estuaries in the world. The association with native PGPR is being studied with a view to their biotechnological potential in environmental decontamination. As a novelty, the oxygen-isotope fractionation technique was used to study the in vivo activities of cytochrome oxidase (COX) and alternative oxidase (AOX) pathways. Inoculated plants showed decreased antioxidant enzymatic activities and in vivo root respiration rates. The reduction in respiratory carbon consumption and the stress alleviation may explain the increments observed in S. maritima root biomass and metal rhizoaccumulation after inoculation. For the first time, plant carbon balance and PGPR are interrelated to explain the effect of rhizobacteria under abiotic stress.

Salt-marsh soils are soils characterized by non-permanent hydric saturation that, depending on factors like duration of submersion periods, are dominated by different salt-tolerant plant species. The composition of microbial communities is an essential component in trophic dynamics and biogeochemical processes in salt marshes, and determines the level of enzymatic activities, which catalyze the conversion of complex molecules into simpler ones. Despite of this, the enzymatic activities in marsh-soils has not yet been investigated. The aim of this study was to analyze the enzymatic activities in two soil profiles of marsh-soils under different water saturation level and dominated by different plant species [Juncus maritimus Lam and Spartina maritima (Curtis) Fernald (Sp)]. In both soils, the enzymatic activities were much lower than the levels typically found in terrestrial ecosystems. The enzymatic activities were measured both in air-dried and in re-moistened and incubated soil samples. In air-dried samples, the enzymatic activities were higher in Juncus than in Spartina soil and tended to decrease with depth, being sharper the decrease in Juncus than in Spartina soil. Re-moistened and pre-incubated soils showed a general increase in all the enzymatic activities and throughout the whole soil profile, especially in Spartina soils. Hydrolase activities showed a strong and positive relationship with organic matter content both in air-dried and in re-moistened soil samples, higher in these latter. In general, oxidoreductase activities only showed this relationship in re-moistened soil samples. More studies, preferably using freshly collected soil samples, are needed to understand the relationship between enzymatic activities and these environmental conditions.

The present study aims to unravel ecophysiological mechanisms underlying plant-microbe interactions under natural abiotic stress conditions, specifically heavy metal pollution. Effect of plant growth promoting rhizobacteria (PGPR) bioaugmentation on Spartina maritima in vivo root respiration and oxidative stress was investigated. This autochthonous plant is a heavy metal hyperaccumulator cordgrass growing in one of the most polluted estuaries in the world. The association with native PGPR is being studied with a view to their biotechnological potential in environmental decontamination. As a novelty, the oxygen-isotope fractionation technique was used to study the in vivo activities of cytochrome oxidase (COX) and alternative oxidase (AOX) pathways. Inoculated plants showed decreased antioxidant enzymatic activities and in vivo root respiration rates. The reduction in respiratory carbon consumption and the stress alleviation may explain the increments observed in S. maritima root biomass and metal rhizoaccumulation after inoculation. For the first time, plant carbon balance and PGPR are interrelated to explain the effect of rhizobacteria under abiotic stress. [ABSTRACT FROM AUTHOR]

Non-native Spartina spp. have invaded many coastal saltmarshes worldwide. Introduced Spartina may cause problems like displacement of native vegetation and hybridisation with native species, leading to changes to relevant ecosystem services and saltmarsh geomorphology. Here we report the extensive and so far overlooked replacement of the native Spartina maritima by non-native S. anglica and S. townsendii along 400 km of the coast of the north-western Adriatic Sea (Mediterranean Sea). We analysed the distribution of both native and non-native Spartina spp. along the six main saltmarsh areas in the region, and produced maps of their presence by using a combination of genetic tools, morphological analysis and geotagged photographs, complemented with field observations. We also reviewed historical herbaria from the region to explore when the first non-native introductions could have occured. We found that S. anglica and S. townsendii are unexpectedly widespread, having established along the whole study region, in one lagoon totally replacing the local native species. Its introduction happened virtually unnoticed, and misidentified herbarium specimens date back as early as 1987. We discuss the ecological implications of this overlooked extensive replacement, and the need for a comprehensive assessment of the status of the saltmarshes in this region, both to protect the few remaining patches of the native S. maritima and control the spread of the non-native species across the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

An early assessment of biological invasions is important for initiating conservation strategies. Instrumental progress in high spatial resolution (HSR) multispectral satellite sensors greatly facilitates ecosystems’ monitoring capability at an increasingly smaller scale. However, species detection is still challenging in environments characterized by a high variability of vegetation mixing along with other elements, such as water, sediment, and biofilm. In this study, we explore the potential of Pléiades HSR multispectral images to detect and monitor changes in the salt marshes of the Bay of Arcachon (SW France), after the invasion of Spartina anglica. Due to the small size of Spartina patches, the spatial and temporal monitoring of Spartina species focuses on the analysis of five multispectral images at a spatial resolution of 2 m, acquired at the study site between 2013 and 2017. To distinguish between the different types of vegetation, various techniques for land use classification were evaluated. A description and interpretation of the results are based on a set of ground truth data, including field reflectance, a drone flight, historical aerial photographs, GNSS and photographic surveys. A preliminary qualitative analysis of NDVI maps showed that a multi-temporal approach, taking into account a delayed development of species, could be successfully used to discriminate Spartina species (sp.). Then, supervised and unsupervised classifications, used for the identification of Spartina sp., were evaluated. The performance of the species identification was highly dependent on the degree of environmental noise present in the image, which is season-dependent. The accurate identification of the native Spartina was higher than 75%, a result strongly affected by intra-patch variability and, specifically, by the presence of areas with a low vegetation density. Further, for the invasive Spartina anglica, when using a supervised classifier, rather than an unsupervised one, the accuracy of the classification increases from 10% to 90%. However, both algorithms highly overestimate the areas assigned to this species. Finally, the results highlight that the identification of the invasive species is highly dependent both on the seasonal presence of itinerant biological features and the size of vegetation patches. Further, we believe that the results could be strongly improved by a coupled approach, which combines spectral and spatial information, i.e., pattern-recognition techniques.

Phytochelatins (PCs) and monothiols and their relation with trace element concentrations were studied in three plant species from two Portuguese salt marshes. Belowground tissues showed always higher element concentrations, while enhanced values of monothiols were found in aboveground biomass. Glutathione was usually the most abundant monothiol. The concentration of total PCs was higher in leaves or stems than in roots of Halimione portulacoides and Sarcocornia perennis , while in Spartina maritima the highest concentrations were reported in large roots. PC 2 was synthesized by all tissues and species and was higher in large roots of S. maritima . PC 4 and PC 5 were in high levels in small roots of S. maritima . PC 2 was positively correlated with As, Zn and Pb. Although being the first evidence of PCs and monothiols in these species under natural conditions, our results do not point to a simple relationship with elements concentrations, suggesting a complex mechanism involved. [ABSTRACT FROM AUTHOR]

The present work aimed to evaluate the capacity of constructed wetlands (CWs) to remove three emerging organic contaminants with different physicochemical properties: caffeine (CAF), oxybenzone (MBPh), and triclosan (TCS). The simulated CWs were set up with a matrix of light expanded clay aggregates (LECA) and planted with Spartina maritima, a salt marsh plant. Controlled experiments were carried out in microcosms using deionized water and wastewater collected at a wastewater treatment plant (WWTP), with different contaminant mass ranges, for 3, 7, and 14 days. The effects of variables were tested isolatedly and together (LECA and/or S. maritima). The presence of LECA and/or S. maritima has shown higher removal (around 61-97%) of lipophilic compounds (MBPh and TCS) than the hydrophilic compound (CAF; around 19-85%). This was attributed to the fact that hydrophilic compounds are dissolved in the water column, whereas the lipophilic ones suffer sorption processes promoting their removal by plant roots and/or LECA. In the control (only wastewater), a decrease in the three contaminant levels was observed. Adsorption and bio/rhizoremediation are the strongest hypothesis to explain the decrease in contaminants in the tested conditions. [ABSTRACT FROM AUTHOR]

Endophytic bacterial population was isolated from Spartina maritima tissues, a heavy metal bioaccumulator cordgrass growing in the estuaries of Tinto, Odiel and Piedras River (south west Spain), one of the most polluted areas in the world. Strains were identified and ability to tolerate salt and heavy metals along with plant growth promoting and enzymatic properties were analysed. A high proportion of these bacteria were resistant towards one or several heavy metals and metalloids including As, Cu and Zn, the most abundant in plant tissues and soil. These strains also exhibited multiple enzymatic properties as amylase, cellulase, chitinase, protease and lipase, as well as plant growth promoting properties, including nitrogen fixation, phosphates solubilisation and production of indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The best performing strains (Micrococcus yunnanensis SMJ12, Vibrio sagamiensis SMJ18 and Salinicola peritrichatus SMJ30) were selected and tested as a consortium by inoculating S. maritima wild plantlets in greenhouse conditions along with wild polluted soil. After 30 days, bacterial inoculation improved plant photosynthetic traits and favoured intrinsic water use efficiency. However, far from stimulating plant metal uptake, endophytic inoculation lessened metal accumulation in above and belowground tissues. These results suggest that inoculation of S. maritima with indigenous metal-resistant endophytes could mean a useful approach in order to accelerate both adaption and growth of this indigenous cordgrass in polluted estuaries in restorative operations, but may not be suitable for rhizoaccumulation purposes.

Soil bacterial community dynamics was assessed in some of the most polluted estuaries by heavy metals of the world. The influence of seasons, heavy metal pollution, and Spartina maritima rhizosphere throughout an entire year were compared in Tinto, Odiel, and Piedras salt marshes from Huelva, Spain. The less contaminated estuary showed the highest bacterial biodiversity, especially in rhizosphere, which was deeply affected by seasonal changes. On the contrary, bacterial diversity in the most polluted salt marsh was lower and neither plant roots nor seasons had a marked effect on their annual dynamics. This work provided evidence that soil bacterial communities in south western Spain estuarine sediments were not completely related to the plant species they inhabit with, but to environmental conditions, prioritizing pollution levels. These results may be considered for conducting planned restoration strategies using native plant growth promoting rhizobacteria together with heavy metal hyperaccumulator S. maritima to preserve these endangered ecosystems. [ABSTRACT FROM AUTHOR]

The aim of our work was the isolation and characterization of bacteria from the rhizosphere of Spartina maritima in the metal contaminated Odiel estuary (Huelva, SW Spain). From 25 strains, 84 % were identified as gram-positive, particularly Staphylococcus and Bacillus. Gram-negative bacteria were represented by Pantoea and Salmonella. Salt and heavy metal tolerance, metal bioabsorption, plant growth promoting (PGP) properties, and biofilm formation were investigated in the bacterial collection. Despite the higher abundance of gram-positive bacteria, gram-negative isolates displayed higher tolerance toward metal(loid)s (As, Cu, Zn, and Pb) and greater metal biosorption, as deduced from ICP-OES and SEM-EDX analyses. Besides, they exhibited better PGP properties, which were retained in the presence of metals and the ability to form biofilms. Gram-negative strains Pantoea agglomerans RSO6 and RSO7, together with gram-positive Bacillus aryabhattai RSO25, were selected for a bacterial consortium aimed to inoculate S. maritima plants in metal polluted estuaries for phytoremediation purposes. [ABSTRACT FROM AUTHOR]

Spartina maritima is an ecosystem engineer that has shown to be useful for phytoremediation purposes. A glasshouse experiment using soil from a metal-contaminated estuary was designed to investigate the effect of a native bacterial consortium , isolated from S. maritima rizhosphere and selected owing to their plant growth promoting properties and multiresistance to heavy metals, on plant growth and metal accumulation. Plants of S. maritima were randomly assigned to three soil bioaugmentation treatments (without inoculation, one inoculation and repeated inoculations) for 30 days. Growth parameters and photosynthetic traits, together with total concentrations of several metals were determined in roots and/or leaves. Bacterial inoculation improved root growth, through a beneficial effect on photosynthetic rate ( A N ) due to its positive impact on functionality of PSII and chlorophyll concentration. Also, favoured intrinsic water use efficiency of S. maritima , through the increment in A N , stomatal conductance and in root-to-shoot ratio. Moreover, this consortium was able to stimulate plant metal uptake specifically in roots, with increases of up to 19% for As, 65% for Cu, 40% for Pb and 29% for Zn. Thus, bioaugmentation of S. maritima with the selected bacterial consortium can be claimed to enhance plant adaptation and metal rhizoaccumulation during marsh restoration programs. [ABSTRACT FROM AUTHOR]

Salt marshes provide environmental conditions that are known to affect metal speciation in sediments. The elevational gradient along the marsh and consequent differential flooding are some of the major factors influencing halophytic species distribution and coverage due to their differential tolerance to salinity and submersion. Different species, in turn, also have distinct influences on the sediment's metal speciation, and its metal accumulation abilities. The present work aimed to evaluate how different halophyte species in two different salt marshes could influence metal partitioning in the sediment at root depth and how that could differ from bare sediments. Metal speciation in sediments around the roots (rhizosediments) of Halimione portulacoides , Sarcocornia fruticosa and Spartina maritima was determined by sequentially extracting operationally defined fractions with solutions of increasing strength and acidity. Rosário salt marsh generally showed higher concentrations of all metals in the rhizosediments. Metal partitioning was primarily related to the type of metal, with the elements' chemistry overriding the environment's influence on fractionation schemes. The most mobile elements were Cd and Zn, with greater availability being found in non-vegetated sediments. Immobilization in rhizosediments was predominantly influenced by the presence of Fe and Mn oxides, as well as organic complexes. In the more mature of both salt marshes, the differences between vegetated and non-vegetated sediments were more evident regarding S. fruticosa , while in the younger system all halophytes presented significantly different metal partitioning when compared to that of mudflats. [ABSTRACT FROM AUTHOR]

The history of many plant lineages is complicated by reticulate evolution with cases of hybridization often followed by genome duplication (allopolyploidy). In such a context, the inference of phylogenetic relationships and biogeographic scenarios based on molecular data is easier using haploid markers like chloroplast genome sequences. Hybridization and polyploidization occurred recurrently in the genus Spartina (Poaceae, Chloridoideae), as illustrated by the recent formation of the invasive allododecaploid S. anglica during the 19th century in Europe. Until now, only a few plastid markers were available to explore the history of this genus and their low variability limited the resolution of species relationships. We sequenced the complete chloroplast genome (plastome) of S. maritima , the native European parent of S. anglica , and compared it to the plastomes of other Poaceae. Our analysis revealed the presence of fast-evolving regions of potential taxonomic, phylogeographic and phylogenetic utility at various levels within the Poaceae family. Using secondary calibrations, we show that the tetraploid and hexaploid lineages of Spartina diverged 6–10 my ago, and that the two parents of the invasive allopolyploid S. anglica separated 2–4 my ago via long distance dispersal of the ancestor of S. maritima over the Atlantic Ocean. Finally, we discuss the meaning of divergence times between chloroplast genomes in the context of reticulate evolution. [ABSTRACT FROM AUTHOR]

Endophytic bacterial population was isolated from Spartina maritima tissues, a heavy metal bioaccumulator cordgrass growing in the estuaries of Tinto, Odiel, and Piedras River (south west Spain), one of the most polluted areas in the world. Strains were identified and ability to tolerate salt and heavy metals along with plant growth promoting and enzymatic properties were analyzed. A high proportion of these bacteria were resistant toward one or several heavy metals and metalloids including As, Cu, and Zn, the most abundant in plant tissues and soil. These strains also exhibited multiple enzymatic properties as amylase, cellulase, chitinase, protease and lipase, as well as plant growth promoting properties, including nitrogen fixation, phosphates solubilization, and production of indole-3-acetic acid (IAA), siderophores and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. The best performing strains (Micrococcus yunnanensis SMJ12, Vibrio sagamiensis SMJ18, and Salinicola peritrichatus SMJ30) were selected and tested as a consortium by inoculating S. maritima wild plantlets in greenhouse conditions along with wild polluted soil. After 30 days, bacterial inoculation improved plant photosynthetic traits and favored intrinsic water use efficiency. However, far from stimulating plant metal uptake, endophytic inoculation lessened metal accumulation in above and belowground tissues. These results suggest that inoculation of S. maritima with indigenous metal-resistant endophytes could mean a useful approach in order to accelerate both adaption and growth of this indigenous cordgrass in polluted estuaries in restorative operations, but may not be suitable for rhizoaccumulation purposes. [ABSTRACT FROM AUTHOR]

Fungal communities associated with early stages of decomposition of Spartina maritima (Curtis) Fernald were assessed in two geographically distinct salt marshes in Portugal by direct observation of fungal sporulating structures. Twenty-three fungal taxa were identified from 390 plant samples, 11 of which were common to both study sites. Natantispora retorquens, Byssothecium obiones, Phaeosphaeria spartinicola, Phoma sp. 1 and Stagonospora sp. were the most frequent fungal taxa in the studied communities. The fungal species Anthostomella spissitecta, Camarosporium roumeguerii, Coniothyrium obiones, Decorospora gaudefroyi, Halosarpheia trullifera, Leptosphaeria marina and Stagonospora haliclysta were recorded for the first time on S. maritima plants; with the exception of C. roumeguerii and L. marina, all of these species were also new records for Portugal. The differences between species composition of the communities associated with S. maritima were attributed to differences in abiotic conditions of the salt marshes. Although the fungal taxa were distributed differently along the host plants, common species to both fungal communities were found on the same relative position, e.g. B. obiones, Lulworthia sp. and N. retorquens occurred on the basal plant portions, Buergenerula spartinae, Dictyosporium pelagicum and Phoma sp. 1 on the middle plant portions and P. spartinicola and Stagonospora sp. on the top plant portions. The distinct vertical distribution patterns reflected species-specific salinity requirements and flooding tolerance, but specially substrate preferences. The most frequent fungi in both communities also exhibited wider distribution ranges and produced a higher number of fruiting structures, suggesting a more active key role in the decay process of S. maritima. [ABSTRACT FROM AUTHOR]

Saltmarshes have been depleted historically, and cumulative stressors threaten their future persistence. We examined experimentally how nutrient availability (high vs. low) affects the responses of Spartina maritima to increased inundation in two mineral soil types (low vs. medium organic). Increased inundation, one of the effects of accelerated sea level rise, had negative effects on most plant growth parameters, but the magnitude varied with soil and nutrient levels, and between plants from different locations. Average differences between inundation treatments were largest at high nutrient conditions in low organic matter soils. We conclude that saltmarsh vegetation would be more drastically affected by increased inundation in low than in medium organic matter soils, and especially in estuaries already under high nutrient availability. This knowledge enhances the prediction of changes at the foreshore of saltmarshes related to sea level rise, and the development of site-specific conservation strategies. [ABSTRACT FROM AUTHOR]

Spartina maritima is a native endangered heavy metal rhizoaccumulator cordgrass naturally growing in southwest coasts of Spain, where is used as a biotool to rehabilitate degraded salt marshes. Fifteen bacterial strains were isolated from the rhizosphere of S . maritima growing in the estuary of the Tinto River, one of the most polluted areas in the world. A high proportion of bacteria were resistant towards several heavy metals. They also exhibited multiple plant growth promoting (PGP) properties, in the absence and the presence of Cu. Bacillus methylotrophicus SMT38, Bacillus aryabhattai SMT48, B . aryabhattai SMT50 and Bacillus licheniformis SMT51 were selected as the best performing strains. In a gnobiotic assay, inoculation of Medicago sativa seeds with the selected isolates induced higher root elongation. The inoculation of S . maritima with these indigenous metal-resistant PGP rhizobacteria could be an efficient method to increase plant adaptation and growth in contaminated estuaries during restoration programs. [ABSTRACT FROM AUTHOR]

Spartina species play an important ecological role on salt marshes. Spartina maritima is an Old-World species distributed along the European and North-African Atlantic coasts. This hexaploid species (2n = 6x = 60, 2C = 3,700 Mb) hybridized with different Spartina species introduced from the American coasts, which resulted in the formation of new invasive hybrids and allopolyploids. Thus, S. maritima raises evolutionary and ecological interests. However, genomic information is dramatically lacking in this genus. In an effort to develop genomic resources, we analysed 40,641 high-quality bacterial artificial chromosome-end sequences (BESs), representing 26.7 Mb of the S. maritima genome. BESs were searched for sequence homology against known databases. A fraction of 16.91 % of the BESs represents known repeats including a majority of long terminal repeat (LTR) retrotransposons (13.67 %). Non-LTR retrotransposons represent 0.75 %, DNA transposons 0.99 %, whereas small RNA, simple repeats and low-complexity sequences account for 1.38 % of the analysed BESs. In addition, 4,285 simple sequence repeats were detected. Using the coding sequence database of Sorghum bicolor, 6,809 BESs found homology accounting for 17.1 % of all BESs. Comparative genomics with related genera reveals that the microsynteny is better conserved with S. bicolor compared to other sequenced Poaceae, where 37.6 % of the paired matching BESs are correctly orientated on the chromosomes. We did not observe large macrosyntenic rearrangements using the mapping strategy employed. However, some regions appeared to have experienced rearrangements when comparing Spartina to Sorghum and to Oryza. This work represents the first overview of S. maritima genome regarding the respective coding and repetitive components. The syntenic relationships with other grass genomes examined here help clarifying evolution in Poaceae, S. maritima being a part of the poorly-known Chloridoideae sub-family. [ABSTRACT FROM AUTHOR]

Spartina species of the mid-low intertidal areas are powerful ecological engineers that are highly valued where they are native. Elsewhere, they overgrow native salt marsh and open intertidal mudflats, diminish biota, increase costs of managing wildlife, and interfere with human uses of estuaries. Huge efforts have been mounted to kill some populations of invading Spartina. All large Spartina invasions are by S. densiflora (2 n = 7 x = 70) or S. alterniflora (2 n = 6 x = 62) or hybrids between the hexaploid species (2 n = 6 x). Hybridization is a recurrent theme in Spartina; the allododecaploid S. anglica (2 n = 12 x = 120) and the hybrid swarm in San Francisco Bay arose through the introductions of S. alterniflora into the range of native Spartina species. The ancient hybrid S. densiflora also hybridized with native Spartina species. Hybridization promotes the evolution of highly invasive populations and hampers control efforts. Whether Spartina, native and not, would protect the shore as sea levels rise depends upon unimpeded areas for upward marsh growth and sufficient sediment, conditions that are often not satisfied. [ABSTRACT FROM AUTHOR]

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C gand sediment N content was ca. 1.8 mg N g. The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g) and the lowest in roots (361 ± 4 mg C g). S. maritima also concentrated more N in its leaves (31 ± 1 mg N g) than in other organs. C stock in the restored marshes was 29.6 t C ha; ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha, with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation. [ABSTRACT FROM AUTHOR]

Different characteristics of Spartina maritima found in two distinct salt marshes located in different estuaries were analysed through interpretation of their local hydrodynamic patterns, as well as the impact of sea level rise on physical processes and consequently on plant dynamics and salt marshes stability. These salt marshes are situated in two of the most important Portuguese coastal systems, Tagus estuary (Rosário salt marsh) and Ria de Aveiro lagoon (Barra salt marsh), which are dominated by physical processes that induce strong tidal currents. They were monitored during one year and plant and sediment samples of S. maritima were collected quarterly in order to determine the vegetation coverage, above and belowground biomass, organic matter and sediment moisture. Residual circulation, tidal asymmetry and tidal dissipation were determined from numerical modelling results of the MOHID 2D model that was applied to each coastal system, considering the actual sea level and a sea level rise (SLR) scenario. Results suggest that the different characteristics found for Spartina maritima in the Rosário and the Barra salt marshes may be related with the diverse hydrodynamic conditions identified for each salt marsh. Consequently, the exploration of SLR scenario predictions indicates how these salt marshes could evolve in the future, showing that the important changes in these hydrodynamic parameters under climate change context might induce significant modifications in the salt marshes dynamics and stability. SLR scenario could lead to changes in nutrients and sediments patterns around the salt marshes and thus vegetation coverage percentage would be affected. Additionally, as a consequence of flood duration increase, sediment moisture will increase causing a stress condition to plants. Hence, the ratio below/aboveground biomass might increase, becoming critical to plants survival under conditions of accelerated sea level rise. Accordingly, both SLR and expected changes in vegetation coverage percentage in controlling salt marshes evolution have important implications in their stability and consequently in coastal management. These conditions are unlikely to be unique to these salt marshes and it is suggested that similar analyses are replicated for other tidally dominated systems to improve understanding and characterization of their dynamics and stability under climate change context. [ABSTRACT FROM AUTHOR]

Some plants have high ability to absorb heavy metals in high concentrations. In this study, Spartina maritima was tested in conjunction with low molecular weight organic acids (LMWOA), in order to evaluate the possible use of this plant in phytoremediation processes in salt marshes. Three different LMWOA (citric acid, malic acid and acetic acid) were applied to contaminated intact cores of S. maritima colonized sediment and several heavy metals (Cd, Zn, Pb, Cu, Cr and Ni) were analyzed in sediment and plant parts. Acetic acid application proved to be the most efficient, enhancing greatly the uptake of all metals analyzed. Citric acid also showed good results, while malic acid proved to be very inefficient in most of the cases. The highest enhancement was observed for Cr with a 10-fold increase of the uptake upon application of acetic acid, while improving the Pb uptake proved to be the most difficult, probably due to its low solubility. [ABSTRACT FROM AUTHOR]

Abstract: Future climatic scenarios combine increasing concentrations of atmospheric CO2 and rising sea levels. Spartina maritima is a C4 halophyte that is an important pioneer and ecosystem engineer in salt marshes of the Atlantic coast of southern Europe. A glasshouse experiment investigated the combined effects on its growth and photosynthetic apparatus of approximately doubling CO2 concentration (from 380 to 700μmolmol−1) at a range of salinity (0, 171 and 510mM NaCl). We measured relative growth rates, gas exchange, chlorophyll fluorescence parameters, photosynthetic pigment concentrations, and total ash, Na+, K2+, Ca2+ and N concentrations. Elevated CO2 stimulated growth of S. maritima by c. 65% at all external salinities; this growth enhancement was associated with greater net photosynthetic rate (A) and improved leaf water relations. A increased despite a drop in stomatal conductance in response to 700μmolmol−1 CO2. CO2 and salinity had a marked overall effect on the photochemical (PSII) apparatus and the synthesis of photosynthetic pigments. Φ PSII values at midday decreased significantly with external salinity in plants grown at 380μmolmol−1 CO2; and Fv /Fm and Φ PSII values were higher at 700μmolmol−1 CO2 in presence of NaCl. Plant nutrient concentrations declined under elevated CO2, which can be ascribed to the dilution effect caused by an increase in biomass. The results suggest that the productivity S. maritima and the ecosystem services it provides will increase in likely future climatic scenarios. [ABSTRACT FROM AUTHOR]

Abstract: This study characterizes humic substances (HS) from two soils colonized by Spartina maritima at different physiographical positions in estuarine environments on the north-western coast of the Iberian Peninsula: the Villaviciosa site, a stand close to the main tidal channel, and the Ortigueira site, located in the low salt marsh. Humic and fulvic acids were extracted from the soils and characterized qualitatively by the following spectroscopic techniques: Fourier transform infrared spectroscopy, fluorescence spectroscopy and solid-state 13C nuclear magnetic resonance. The characterized HS showed a predominance of low humified compounds with a high proportion of aliphatic components and a low degree of aromaticity. The HS composition differed substantially between sites. In the Villaviciosa soil, the large amount of nonpolar aliphatic components and the very low degree of aromaticity may indicate a significant contribution of marine organic matter and/or microbial material to the HS. However, in the HS from the Ortigueira soil, the higher proportion of polysaccharides together with the presence of lignin-derived compounds may indicate greater inputs of vascular plant material. The δ 13C isotopic composition of the bulk soils highlights the large input of Spartina maritima debris to the Ortigueira site, whereas in the Villaviciosa site, organic contributions from this C4 vascular plant were not so evident. The results indicate that in these soils colonized by Spartina maritima, physiographical position has an important effect on the composition of soil HS and, therefore, must be considered in the study of organic matter characteristics in such estuarine environments. [Copyright &y& Elsevier]

In the joint estuary of the Odiel and Tinto rivers (SW Spain), the invasive Spartina densiflora Brongn. and the native Spartina maritima (Curtis) Fernald are growing over sediments with extreme concentrations of heavy metals. The contents of As, Cu, Fe, Mn, Pb and Zn were determined in sediments, rhizosediments and different tissues of both species, from Odiel and Tinto marshes. S. densiflora showed a higher capability to retain metals around their roots and to control the uptake or transport of metals, mediated by a higher formation of plaques of Fe/Mn (hydro) oxides on the roots. At the Tinto marsh, there were no differences between the metal concentrations of the sediment and those of the rhizosediment, a fact that could be explained by the extremely high concentrations of metals which can pass over a threshold value, altering the properties of root cells and preventing roots from acting as a ‘barrier’ to the uptake or transport of metals. [Copyright &y& Elsevier]

Abstract: Salt marshes are among the most productive ecosystems in the world, performing important ecosystem functions, particularly nutrient recycling. In this study, a comparison is made between Mondego and Tagus estuaries in relation to the role of Spartina maritima in nitrogen retention capacity and cycling. Two mono-specific S. maritima stands per estuary were studied during 1yr (biomass, nitrogen (N) pools, litter production, decomposition rates). Results showed that the oldest Tagus salt marsh population presented higher annual belowground biomass and N productions, and a slower decomposition rate for litter, contributing to the higher N accumulation in the sediment, whereas S. maritima younger marshes had higher aboveground biomass production. Detritus moved by tides represented a huge amount of aboveground production, probably significant when considering the N balance of these salt marshes. Results reinforce the functions of salt marshes as contributing to a reduction of eutrophication in transitional waters, namely through sedimentation processes. [Copyright &y& Elsevier]

Extracellular enzymatic activity (EEA) of five enzymes (peroxidase, phenol oxidase, β-glucosidase, β-N-acetylglucosaminidase and acid phosphatase) was analysed in sediments colonised by Spartina maritima in two salt marshes (Rosário and Pancas) of the Tagus estuary (Portugal) with different characteristics such as sediment parameters and metal contaminant levels. Our aim was a better understanding of the influence of the halophyte on microbial activity in the rhizosphere under different site conditions, and its potential consequences for metal cycling and phytoremediation in salt marshes. Acid phosphatase and β-N-acetylglucosaminidase presented significantly higher EEA in Rosário than in Pancas, whereas the opposite occurred for peroxidase. This was mainly attributed to differences in organic matter between the two sites. A positive correlation between root biomass and EEA of hydrolases (β-glucosidase, β-N-acetylglucosaminidase and acid phosphatase) was found, indicating a possible influence of the halophyte in sediment microbial function. This would potentially affect metal cycling in the rhizosphere through microbial reactions. [Copyright &y& Elsevier]

Total concentrations and fractionation of Cu, Zn and Pb in seven operationally defined phases (exchangeable, carbonates, manganese oxides, organic complexes, amorphous iron oxides, crystalline iron oxides and residual) were determined in sediments colonised by the halophyte species Halimione portulacoides and Spartina maritima in a Tagus estuary salt marsh (Portugal). We aimed to determine whether the speciation of these metals was different in areas colonised by each halophyte. Higher concentrations of Cu, Zn and, in particular Pb, were found in the rhizosphere of S. maritima than in the root sediments of H. portulacoides. Geochemical fractionation of Cu, Zn and Pb in sediments of the salt marsh depended upon the metal, and for Zn and Pb clearly varied with depth and with the colonising species. The higher redox potential observed in sediments colonised by H. portulacoides may in part explain the observed differences in the speciation of Cu, Zn and Pb. [Copyright &y& Elsevier]

The role of salt marshes as nitrogen sink is examined taking into consideration the seasonal variation of above and belowground biomass of Spartina martima and Halimione portulacoides in two marshes from Tagus estuary, Pancas and Corroios, and the degradation rates of belowground litter. Total nitrogen was determined in plant components, decomposing litter and sediment. Biomass was higher in Corroios, the saltier marsh, with 7190 g m−2 y−1 dw of S. maritima and 6593 g m−2 y−1 dw of H. portulacoides and the belowground component contributed to 96% and 90% of total biomass, respectively. In the other marsh, Pancas, belowground biomass contributed to 56% and 76% of total biomass for S. maritima and H. portulacoides, respectively. Litterbag experiment showed that between 25% and 50% of nitrogen is lost within the first month and remained relatively constant in the next four months. Slower decomposition is observed in sediments with higher nitrogen concentration (max. 0.7% N in the saltier marsh). Higher concentrations of N were found in the sediment upper layers. Considering the sediment-root system, most of the nitrogen is stored in the sediment compartment and only about 1–4% of the total N was found in the roots. Considering these results, Tagus salt marshes act as a sink for nitrogen. [ABSTRACT FROM AUTHOR]