Salt Marsh Halophytes Research Articles

Sub-lethal effects of metal(loid) contamination on the halophyte Sarcocornia quinqueflora with links to plant photosynthetic performance and biomass – A field study

Two saltmarsh locations within Lake Macquarie, NSW, Australia were selected to investigate the uptake and partitioning of metal(loid)s Cu, Zn, As, Se, Cd and Pb in the Australian saltmarsh halophyte, Sarcocornia quinqueflora and the associated sub-lethal effects of metal(loid)s on plant health, including photosynthetic performance, biomass, and productivity. Metal(loid)s primarily accumulated to roots (BCF > 1). Barriers to transport were observed at the root to non-photosynthetic stem transition (TF < 1) for all metal(loid)s, suggesting this species is suitable for phytostabilisation. Sediment and plant tissue metal(loid) concentrations were significantly correlated with photosynthetic performance and plant biomass. As such, the action of sediment and tissue metal(loid)s on photosynthetic performance and the subsequent effect on biomass of S.quinqueflora appear to be suitable targets for molecular analyses to further elucidate mechanisms responsible for the observed adverse effects and the development of adverse outcome pathways.

Biotic versus abiotic factors shaping culturable root endosymbionts of the saltmarsh halophyte, Batis maritima and implications for plant stress tolerance

Biotic versus abiotic factors shaping culturable root endosymbionts of the saltmarsh halophyte, Batis maritima and implications for plant stress tolerance

Upregulation of antioxidant enzymes contribute to the elevated tolerance of Juncus acutus offspring from metal contaminated environments

Long-term environmental exposure to metals e.g. zinc (Zn), may allow saltmarsh halophytes to develop metal tolerance to improve the chance of survival of their progeny in future metal-contaminated scenarios. Juncus acutus seeds were collected from mature parents (F0) inhabiting a legacy Zn-contaminated location (Cockle Creek) and an uncontaminated reference location (Swansea) of Lake Macquarie, NSW, Australia. Seeds (J. acutus) were exposed to Zn (0.00 mM (control), 0.01 mM (effective concentration, EC10) and 0.74 mM (EC50)) and resultant germinants (F1) were allowed to grow until 15 days. Seedling growth parameters i.e. biomass, root length and 1st leaf length, and seedling biochemical responses i.e. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) antioxidant enzyme activity and lipid peroxidation products, malondialdehyde (MDA), were examined in order to assess if enzymes may be implicated in conferring tolerance to the offspring of metal-exposed parents. Control locations exhibited significantly greater declines in biomass and root length with Zn dose compared to seed from contaminated locations, suggesting F1 offspring from contaminated parents were conferred tolerance to Zn. Furthermore, significant upregulation of CAT and GPx enzymes were evident in the seedlings derived from parents of contaminated locations. These are the antioxidative enzymes responsible for minimizing metal-induced oxidative stress, and may, in part, be responsible for increasing seedling fitness and observed tolerance.

Hybrid engineering incorporating salt marsh terraces into sea wall repair maintains their defence function and creates new habitats

Sea walls are widely-used engineered structures designed to protect low lying land from flooding. Rising sea levels and coastal erosion threatens sea wall integrity and requires maintenance and repair. As an alternative to conventional repairs, a hybrid engineering design incorporating sediment-filled terraces to allow the development of salt marsh has been trialled to protect sea walls in the Colne-Blackwater Estuary complex, Essex. U.K. Over a 10 year period, three different trajectories of development were measured. Salt marsh halophytes colonised 7 out of 15 terraces, with % plant cover ranging between 5% and 170%. Halophyte species richness on terraces ranged from 1 to 8 species (average = 1.7 per 4 m2), compared to existing salt marsh adjacent to the repairs (max. species richness 9, average 6.85), with positive significant relationships between % halophyte cover and halophyte richness and between % halophyte cover and sediment water content (19–51% on terraces). Organic carbon content was significantly lower on the terraces compared to existing salt marsh (7–19 % AFDW on terraces, 17–24% in marsh sediments). A sediment shear strength of 30 kPa was optimal for % plant cover on terraces. The height of the terraces relative to tidal inundation was a key determinant of successful halophyte colonisation. A second trajectory (3 of 15 terraces) resulted in development of macro- and microalgal mats, up to 100 % cover. Both these trajectories resulted in up to 25 cm of vertical sediment accretion. Shell banks formed on 2 terraces. Seven terraces were subject to erosion, associated with desiccation and absence, or loss, of halophyte cover. Eroding terraces showed both surface lowering (20–30 cm) and massive sediment failure (blocks >50 cm deep falling away). After a decade, protection of the sea wall was still provided by 14 of the 15 terraces, with only one having to be rebuilt. Utilising a nature-based approach incorporating sea wall terraces resulted in the formation of three types of linear habitat (salt marsh, microbial mats, shell banks) providing some ecosystem services that would not have existed if a conventional hard-engineered repair had been used.

Endophyte fungi from Agarwood and Mangrove and their applications

Mangroves are woody trees or shrubs salt marsh halophytes that encompass over 75% of the tropical coastline on the planet. Mangroves are characterized by their sophisticated morphological and physiological adaptations as well as their rich synthesis of biologically active secondary metabolites. They also contribute in decreasing CO2 levels in the atmosphere through photosynthesis. On the other hand, agarwood, is an aromatic perfumed precious heartwood of diseased timber of Aquilaria and Gyrinops trees that is used centuries ago till now as incense in religious ceremonies, raw material in the perfume industry and as a medicine. Agarwood formation is usually induced by wounding trunks and branches of Aquilaria trees. Production of natural agarwood resin is inefficient and don’t meet global demand, so different methods have been applied to stimulate biological agarwood induction, and using endophytic fungi is one of the methods. Hence, this review highlights the importance of endophytic fungi in mangroves and agarwood, their existence and some of their important biological activities.

A biochemical and lipidomic approach to perceive Halimione portulacoides (L.) response to mercury: An environmental perspective

The impact of hazardous materials, such as Hg, on life is far from being understood and due to the high number of polluted sites it has generated great concern. A biochemical and lipidomic approach was used to assess the effects of Hg on the saltmarsh halophyte Halimione portulacoides. Plants were collected at two sites of a Hg contaminated saltmarsh. Hg accumulation and distribution in the plant, biochemical parameters (antioxidant and metabolic) and lipid profiles were determined and compared between plant organs and sites (s1 and s2). Hg did not induce antioxidant enzyme activity. Lipid profiles changed under Hg exposure, especially in leaves, decreasing the unsaturation level, the membrane fluidity and stability, and evidencing that membrane lipid remodeling influences plant tolerance to Hg. This knowledge can help select the most appropriate methodologies for the restoration of Hg polluted hotspots, curtailing a serious environmental problem threatening saltmarshes.

Saltmarsh Halophytes in Mannar Landscape, Sri Lanka

Saltmarsh Halophytes in Mannar Landscape, Sri Lanka

A Plant Endophytic Bacterium Priestia megaterium StrainBP-R2 Isolated from the Halophyte Bolboschoenus planiculmis Enhances Plant Growth under Salt and Drought Stresses.

Global warming and climate change have contributed to the rise of weather extremes. Severe drought and soil salinization increase because of rising temperatures. Economically important crop production and plant growth and development are hindered when facing various abiotic stresses. Plant endophytic bacteria live inside host plants without causing visible harm and can be isolated from surface-sterilized plant tissues. Using plant endophytic bacteria to stimulate plant growth and increase environmental stress tolerance has become an alternative approach besides using the traditional breeding and genetically modifying approaches to select or create new crop types resistant to different environmental stresses. The plant endophytic bacterium, Priestia megaterium (previously known as Bacillus megaterium) strain BP-R2, was isolated from the surface-sterilized root tissues of the salt marsh halophyte Bolboschoenus planiculmis. The bacteria strain BP-R2 showed high tolerance to different sodium chloride (NaCl) concentrations and produced the auxin plant hormone, indole acetic acid (IAA), under various tested growth conditions. Inoculation of Arabidopsis and pak choi (Brassica rapa L. R. Chinensis Group) plants with the strain BP-R2 greatly enhanced different growth parameters of the host plants under normal and salt and drought stress conditions compared to that of the mock-inoculated plants. Furthermore, the hydrogen peroxide (H2O2) content, electrolyte leakage (EL), and malondialdehyde (MDA) concentration accumulated less in the BP-R2-inoculated plants than in the mock-inoculated control plants under salt and drought stresses. In summary, the plant endophytic bacterium strain BP-R2 increased host plant growth and stress tolerance to salt and drought conditions.

Role of saltmarsh systems in estuarine trapping of microplastics

Saltmarshes are important natural ecosystems along many temperate (and other) coastlines. They stabilize sediments and act as biofilters for a range of industrial pollutants and, potentially, microplastics. Accumulation of microplastics along estuarine coastlines may be enhanced by the presence of saltmarsh species, as they offer better particle trapping efficiency than adjacent intertidal mudflats under prevailing flood and ebb tidal currents. However, the trapping efficiency of entire saltmarsh systems under varying flow conditions has not been widely assessed. While the effects of saltmarsh systems on water flow, and on sediment transport and trapping, have been relatively well studied, little is known about the contributions of saltmarsh halophytes, resident organisms and the associated saltmarsh sediments to the trapping of microplastics. To address this, a series of flume experiments were undertaken to examine transport and accumulation of Bakelite particles (~ 500 µm) and PVC nurdles (~ 5 mm) as model plastics in sub-sampled saltmarsh and intertidal mudflat monoliths. The results showed that saltmarsh systems influenced the hydrodynamics within and above the canopy, enhancing turbulence and shear stresses. With increasing flow velocities (≤ 0.51 m s−1), negligible quantities (2 times 10−4 mg L−1) of sediments and Bakelite particles were eroded and resuspended. The algal biogenic roughness from the mudflat, and the vegetative roughness from the Spartina plants on the saltmarsh, inhibited the transportation of the microplastics within the tested systems. Resident burrowing crabs (Carcinus maenas) promoted the burial, release and transport of microplastics. The results of this study provide evidence of the contributory roles of saltmarsh systems in the sequestration of microplastics and sediment stabilization. Estuarine saltmarsh systems can act as sinks for microplastics with enhanced burial from burrowing crabs under favourable flow conditions.

Metal(oid)s accumulation (Hg and As) and their biochemical effects in Halimione portulacoides (Ria de Aveiro, Portugal)

For decades, mercury (Hg) and arsenic (As) were discharged into the Aveiro Lagoon. This study was designed to assess the natural attenuation process evolution by: (1) evaluating Hg and As concentration in sediments and in Halimione portulacoides, and assess the long-term evolution of a historically contaminated salt-marsh system; (2) evaluating the stress levels imposed by Hg and As, and the mechanisms triggered to squash oxidative damage. Concentrations of Hg and As in sediments varied considerably between sampling locations. H. portulacoides did not bioconcentrate Hg and As, restricted translocation to aerial biomass and immobilized contaminants in cell walls. The ions that reached the cytosol induced oxidative stress, restrained by antioxidant mechanisms, especially SOD and CAT activity. Results show that after 25 years of natural attenuation, contamination decreased in the sediment, but remains above non-contaminated systems and continues to induce toxicity in the saltmarsh halophyte community, evidencing the persistent effect of Hg and As contamination.

Temporal and spatial patterns of airborne pollen dispersal in six salt marsh halophytes

Pollination is a key process in the life cycle of most plant species, but very little is known about airborne pollen dispersal in salt marsh anemophilous halophytes. We analyzed the temporal and spatial dynamics of airborne pollen dispersal, using portable volumetric pollen traps, for six anemophilous Chenopodiaceae halophytic species in tidal salt marshes. In addition, we studied the effects of air temperature and wind speed on airborne pollen dispersal. Our study shows high levels of temporal and spatial constraint on airborne pollen dispersal. We recorded the lowest airborne pollen concentrations at air temperatures lower than 22 °C and wind speeds higher than 6 m s−1. These environmental conditions set up a narrow temporal pollination window during morning hours. We also recorded severe spatial limitation for pollen dispersal in three of the six halophytes studied, which presented airborne pollen concentrations that were 9 to 53 times smaller only 5 m away from source populations than within those populations. These results show that even related species colonizing the same ecosystem may show contrasted airborne pollen spatial dispersal dynamics that depend on several environmental factors. This should be taken into account for estimates of vegetation composition based on pollen production in aerobiological and paleopalinological studies. The restricted airborne pollen dispersal recorded would promote geitonogamy and limit interpopulation genetic exchange to the dispersal of their hydrochorous fruits.

The accumulation and distribution of arsenic species and selected metals in the saltmarsh halophyte, spiny rush (Juncus acutus)

This study examined the accumulation of As species, Se, Cu, Zn, Cd and Pb in the halophyte Juncus acutus, collected from three anthropogenically impacted estuaries in NSW, Australia. As concentration ranged from 4 to 22 μg/g at Georges River, 2–16 μg/g at Lake Macquarie and 6 μg/g at Hunter Estuary. Inorganic As was accumulated mainly in roots with low translocation to culm with a greater abundance of AsV. However, AsIII (TF = 0.32) showed greater mobility from the roots to shoots than AsV (TF = 0.04), indicating a higher quantity of AsIII specific transporter assemblages in the plasmalemma of the endodermis or cytoplasmic reduction of AsV to AsIII in culms. Metal(loid)s, including As (90%), were predominantly in root tissues and very limited translocation to culm, indicating the species is a useful phytostabiliser. As and all other metal(loid)s in roots were correlated with sediment loads (p < 0.05, R2 = 0.10–0.52), indicating the species would be an accumulative bioindicator.

Elemental localisation and a reduced glutathione redox state protect seeds of the halophyte Suaeda maritima from salinity during over-wintering and germination

Saltmarshes are increasingly at risk from sea level rise through climate change. Their vegetation is comprised of halophytes, salt-tolerant plants, that naturally regenerate from seed, yet the combination of functional traits associated with salinity tolerance in seeds is still poorly characterised. Combining approaches in scanning electron microscopy, energy-dispersive spectrometry, biochemistry and physiology, we focussed on elucidating two mechanisms that are commonly utilised by adult halophyte plants: (1) ion accumulation and elemental localisation, and (2) enhanced antioxidant capacity to protect against oxidative stress, in seeds of the saltmarsh halophyte Suaeda maritima during over-wintering and germination.Freshly collected seeds were dormant, and required 19 weeks of submergence in artificial sea water (ASW) at 5 °C, mimicking over-wintering in the field, to release dormancy. Fresh and pre-treated seeds had an abundance of Na+ and Cl−, as well as the reactive oxygen species H2O2 and glutathione disulphide (i.e., oxidised glutathione). This was accompanied by a large pool of reduced glutathione and the low molecular weight thiols cysteine, cysteinyl-glycine and γ-glutamyl-cysteinyl, suggesting a potentiated antioxidant system in preparation for germination. During germination in ASW, the glutathione and thiol redox state was highly reduced, with no consistent production of H2O2. Na and Cl localised in the seed testa and tegmen, while Mg and K were concentrated in the embryo, and Ca and S had a broad distribution across the seed. Small differences in seed moisture content, measured to indicate the extent of osmotic adjustment, did not account for a higher maximum threshold to germination of 2.22 times the concentration of ASW compared to 1.76 times ASW-equivalents for iso-osmotic solutions of polyethylene glycol (PEG). Moreover, the halotime constant (θHalo) was higher (i.e., slower germination) in the presence of ASW than PEG, suggesting that slower germination may give more time to initiate tolerance mechanisms in response to salinity that promote germination. Seeds of S. maritima appear to utilise seawater ions to their benefit during germination in salinity, using elemental localisation to protect the embryo from potential toxicity of Na and Cl, while maintaining a highly reduced cellular redox state.

LED Lighting and High-Density Planting Enhance the Cost-Efficiency of Halimione Portulacoides Extraction Units for Integrated Aquaculture

Halophytes are salt-tolerant plants that can be used to extract dissolved inorganic nutrients from saline aquaculture effluents under a production framework commonly known as Integrated Multi-Trophic Aquaculture (IMTA). Halimione portulacoides (L.) Aellen (common name: sea purslane) is an edible saltmarsh halophyte traditionally consumed by humans living near coastal wetlands and is considered a promising extractive species for IMTA. To better understand its potential for IMTA applications, the present study investigates how artificial lighting and plant density affect its productivity and capacity to extract nitrogen and phosphorous in hydroponic conditions that mimic aquaculture effluents. Plant growth was unaffected by the type of artificial lighting employed—white fluorescent lights vs. blue-white LEDs—but LED systems were more energy-efficient, with a 17% reduction in light energy costs. Considering planting density, high-density units of 220 plants m−2 produced more biomass per unit of area (54.0–56.6 g m−2 day−1) than did low-density units (110 plants m−2; 34.4–37.1 g m−2 day−1) and extracted more dissolved inorganic nitrogen and phosphorus. Overall, H. portulacoides can be easily cultivated hydroponically using nutrient-rich saline effluents, where LEDs can be employed as an alternative to fluorescent lighting and high-density planting can promote higher yields and extraction efficiencies.

Changes in REE fractionation induced by the halophyte plant Halimione portulacoides, from SW European salt marshes

Yttrium and lanthanides (REE) contents were quantified in Rosário's salt marsh (SW Europe) sediments and in the halophyte plant Halimione portulacoides, to evaluate the plant's ability to accumulate these elements as well as the translocation into their aerial organs, and increase the knowledge on the relations between these metals and the salt marsh halophytes plants. Metal sediment contents ranged from 16 to 26 and 16 to 19 mg·kg−1 for Y, and 47–143 and 149–167 mg·kg−1 for ΣREE, in non-colonised and colonised sediment, respectively. These results highlight the role of grain size in the vertical distribution and REE contents in the salt marsh sediments. The deepest layers of the non-colonised sediment showed a marked enrichment of anthropogenic REE, not observed in the colonised sediment. This difference, together with the increased REE content in the roots (2.6–29 and 14–85 mg·kg−1, for Y and ΣREE, respectively) that lead the roots enrichment factors to values above the unit, points to a scavenging and accumulation in belowground organs, depending on the bioavailability rather than the total concentrations. The obtained results also allow to identify preferential layers of REE accumulation in the roots, with greater predominance for Y and MREE. The lower REE contents in aboveground plant parts suggests either low translocation to the upper organs or low retention on these elements in stems and leaves.

Uptake and partitioning of metals in the Australian saltmarsh halophyte, samphire (Sarcocornia quinqueflora)

Little is known regarding potential uptake of metals in Australian saltmarsh flora, thus the current study endeavored to examine patterns of Zn, Cu, Pb and Cd uptake and partitioning in the dominant saltmarsh halophyte, Samphire (Sarcocornia quinqueflora), across three contaminated estuaries in New South Wales, Australia. Average sediment concentrations ranged from 62 to 764 μg/g for Zn, 20–52 μg/g for Cu, 27–311 μg/g for Pb and 0.45–1.90 μg/g for Cd across estuaries. Lake Macquarie was the most contaminated estuary, with the Hunter River estuary and Sydney Olympic Park exhibiting intermediate levels of sediment metal contamination. Bioconcentration factors for metal uptake from sediment to roots were ≥ 1 (except for Cu). Translocation within the plant was low for most metals, with apparent barriers to transport identified at the root: non-photosynthetic stem interface for Zn, Cu, Pb and Cd, and at the non-photosynthetic stem: photosynthetic stem transition for Pb and Cd. All metals accumulated in roots with increasing sediment exposure, and lower soil organic matter predicted greater Pb and Cu uptake to roots. Further, increases in sediment pH predicted greater Cd root accumulation. However, transport was regulated to the non-photosynthetic stem for Zn, and to the PS stem for Zn and Pb. In terms of employing S. quinqueflora as a bioindicator, all root metals, and Pb and Cd in non-photosynthetic stem tissue exhibited relationships with sediment metal loads, though high variability made their predictive ability limited.

Physiological and antioxidant responses of the sabkha biotope halophyte Limonium delicatulum to seasonal changes in environmental conditions

In saline biotopes, different mechanisms may contribute to the tolerance of halophytes to high soil salinity and temperature, drought and other abiotic stresses, but their relative responses and their ecological plasticity for a given species remain unknown. In this study, we examined the responses of the salt marsh halophyte Limonium delicatulum to changing environmental conditions of its natural habitats (Sabkha “El Kalbia”, Tunisia). The specific aim of the work was to check whether statistically significant correlations could be established between particular stress response mechanisms (ion uptake, activation of antioxidant systems) and soil parameters and climatic data associated with environmental stress. The results showed that the salinity of the soil increased during the months of June, July and August (dry period), concomitantly with a strong accumulation of salt ions in the aerial parts of the plant. Moreover, the highest antioxidant capacity of this halophyte (enzymes and antioxidant molecules) was reached during the same period of the year. The remaining periods (corresponding to the rainy season) did not show a significant difference in enzymes activities and level of antioxidants, with a minimum observed in the months of January and February. These results show a remarkable effect of salinity in the natural habitat on the activity of enzymes and antioxidant molecules. Other edaphic and climatic factors could also be involved to increase antioxidant capacity, such as nutrient deficiency, temperature and precipitation.

Zonation and soil factors of salt marsh halophyte communities

The structures and soil factors of Suaeda glauca- Suaeda japonica zonal communities and Phragmites australis-S. japonica zonal communities were studied in salt marshes of west and south coasts of South Korea to provide basic data for coastal wetland conservation and restoration. S. glauca community mean length was 67 m and S. japonica community mean length was 567 m in zonal communities, and P. australis and S. japonica community mean length were 57 m and 191 m in zonal communities. Regarding the electrical conductivity, sodium content, and clay contents in Upnae-ri, Shinan-gun, there were significant differences among zonal communities at significance level of 0.05 for two-sided t test. However, other factors were not significantly different. The results indicate that multiple factors such as electronic conductivity, total nitrogen level, clay, and sodium might play important roles in the formation of zonal plant communities of salt marshes.

Biophysical and Biochemical Markers of Metal/Metalloid-Impacts in Salt Marsh Halophytes and Their Implications

As a major sink, estuarine/salt marsh ecosystem can receive discharges laden with myriads of contaminants including metals/metalloids from man-made activities. Two among the major consequences of metal/metalloid-exposure in estuarine/salt marsh ecosystem flora such as halophytic plants are: (a) the excessive accumulation of light energy that in turn leads to severe impairments in the photosystem II (PS II), and (b) metal/metalloids-accrued elevation in reactive oxygen species (ROS) in cells that causes imbalance in cellular redox homeostasis. On one hand, plants adopt several strategies to dissipate excessive energy hence eventually to avoid damage in the PS II and maintain optimum photosynthesis. On the other hand, components of cellular redox system quickly respond to metal/metalloid exposure, where plants try to maintain a fine-tuning therein and tightly control the level of ROS and its potential consequences. Based on recent reports this paper: (a) overviews in separate sections major insights into and the significance of major biophysical and biochemical markers in metal/metalloid-exposed halophytes; and (b) concludes the paper and highlights major points so far unexplored in the current context. Discussion reflects the need of integrating studies on major biophysical and biochemical markers in order finally to unveil tolerance/resistance mechanisms in halophytes under metal/metalloid exposed conditions.

Phytoextraction of heavy metals by Sesuvium portulacastrum l. a salt marsh halophyte from tannery effluent

ABSTRACTThe present study investigated the sources for remediation of heavy metals and salts from tannery effluent using salt marsh halophyte Sesuvium portulacastrum. From the results observed, in tannery effluent treated soil from 1 kg dry weight of plant sample, Sesuvium portulacastrum accumulated 49.82 mg Cr, 22.10 mg Cd, 35.10 mg Cu and 70.10 mg Zn and from 1 g dry weight of the plant sample, 246.21 mg Na Cl. Cultivation of Sesuvium portulacastrum significantly reduced the EC, pH and SAR levels in tannery effluent and salt treated soil and correspondingly increased in plant sample after 125 days of cultivation. In conclusion, Sesuvium portulacastrum was an efficient in accumulating heavy metals such as Chromium, Cadmium, Copper and Zinc, sodium and chloride maximum through its leaves when compared to stem and root. The finding of these bioacccumulation studies indicates that Sesuvium portulacastrum could be used for phytoremediation of tannery effluent contaminated field.