Halimione Portulacoides Research Articles

Effect of sea purslane (Halimione portulacoides) as feed additive on larval rearing of red tilapia (Oreochromis aureus × Oreochromis mossambicus)

Effect of sea purslane (Halimione portulacoides) as feed additive on larval rearing of red tilapia (Oreochromis aureus × Oreochromis mossambicus)

Redox Homeostasis Disclosed in the Saltmarsh Plant Halimione portulacoides upon Short Waterborne Exposure to Inorganic Mercury.

The saltmarsh plant Halimione portulacoides was shortly exposed to realistic levels of inorganic mercury (iHg) with the aim of investigating the adaptative processes of the roots and leaves regarding redox homeostasis, physiology, and Hg accumulation. Plants were collected at a contaminated (CONT) and a reference (REF) site to address the interference of contamination backgrounds. The influence of major abiotic variables (i.e., temperature and light) was also examined. Total Hg levels, antioxidant enzymes, lipid peroxidation (LPO), and photosynthetic activity were analyzed after 2 and 4 h of exposure. A poor accumulation of Hg in the roots was noticed, and no translocation to the stems and leaves was found, but plants from the CONT site seemed more prone to iHg uptake (in winter). Despite this, antioxidant modulation in the roots and leaves was found, disclosing, in winter, higher thresholds for the induction of enzymatic antioxidants in CONT leaves compared to REF plants, denoting that the former are better prepared to cope with iHg redox pressure. Consistently, CONT leaves exposed to iHg had remarkably lower LPO levels. Exposure did not impair photosynthetic activity, pinpointing H. portulacoides' ability to cope with iHg toxicity under very-short-term exposure. Biochemical changes were noticed before enhancements in accumulation, reinforcing the relevance of these responses in precociously signaling iHg toxicity.

Phytoremediation of chloride from marine dredged sediments: A new model based on a natural vegetation recolonization

Phytoremediation is a type of bioremediation process that involves the use of plants to remove or degrade contaminants from soil, water, or air. In most of the observed phytoremediation models, plants are introduced and planted on a polluted site to take up, absorb, or transform contaminants. This study aims to explore a new mixed phytoremediation approach that involves natural recolonization of a contaminated substrate, by identifying the species growing naturally, their bioaccumulation capacity, and by modeling annual mowing cycles of their aerial parts. This approach aims to evaluate the phytoremediation potential of such a model. Both natural and human interventions are involved in this approach, which is referred to as a mixed phytoremediation process. The study focuses on chloride phytoremediation from a chloride-rich and regulated substrate that is marine dredged sediments abandoned for 12 years and recolonized for 4 years. The sediments are colonized by a Suaeda vera dominated vegetation and possess heterogeneity in lixiviate chloride and conductivity. The study found that despite Suaeda vera is the well adapted species for this environment, it is not an effective species for phytoremediation as it has low bioaccumulation and translocation rates (9.3 and 2.6 respectively), and disturbs chloride leaching below in the substrate. Other identified species, such as Salicornia sp., Suaeda maritima, and Halimione portulacoides, have better phytoaccumulation (respectively 39.8, 40.1, 34.8) and translocation rates (respectively 7.0, 4.5, 5.6) and can successfully remediate the sediment in 2–9 years. The following species have been found to bioaccumulate chloride in aboveground biomass at the following rates: Salicornia sp. (181 g/kg DW), Suaeda maritima (160 g/kg DW), Sarcocornia perennis (150 g/kg DW), Halimione portulacoides (111 g/kg DW) and Suaeda vera (40 g/kg DW).

Molecular Characterization of Dehydrin in Azraq Saltbush among Related Atriplex Species

Atriplex spp. (saltbush) is known to survive extremely harsh environmental stresses such as salinity and drought. It mitigates such conditions based on specialized physiological and biochemical characteristics. Dehydrin genes (DHNs) are considered major players in this adaptation. In this study, a novel DHN gene from Azrak (Jordan) saltbush was characterized along with other Atriplex species from diverse habitats. Intronless DHN-expressed sequence tags (495-761 bp) were successfully cloned and sequenced. Saltbush dehydrins contain one S-segment followed by three K-segments: an arrangement called SK3-type. Two substantial insertions were detected including three copies of the K2-segemnet in A. canescens. New motif variants other than the six-serine standard were evident in the S-segment. AhaDHN1 (A. halimus) has a cysteine residue (SSCSSS), while AgaDHN1 (A. gardneri var. utahensis) has an isoleucine residue (SISSSS). In contrast to the conserved K1-segment, both the K2- and K3-segment showed several substitutions, particularly in AnuDHN1 (A. nummularia). In addition, a parsimony phylogenetic tree based on homologs from related genera was constructed. The phylogenetic tree resolved DHNs for all of the investigated Atriplex species in a superclade with an 85% bootstrap value. Nonetheless, the DHN isolated from Azraq saltbush was uniquely subclustred with a related genera Halimione portulacoides. The characterized DHNs revealed tremendous diversification among the Atriplex species, which opens a new venue for their functional analysis.

Maximizing blue carbon stocks through saltmarsh restoration

Political discourse around coastal wetland restoration and blue carbon management strategies has increased in the past decade, yet carbon storage has neither been a reason for restoration, nor a criterion to measure the success of current saltmarsh restoration schemes in the UK. To maximise climate change mitigation through saltmarsh restoration, knowledge on the key drivers of carbon stock variability is required. We use restored saltmarshes of similar age, paired with adjacent natural marshes as references, to identify drivers of carbon stocks following managed realignment within an estuary in southeastern England. From surficial soil cores (top 30 cm), we measured carbon stock alongside environmental characteristics. Carbon stock between natural and restored sites were similar after ~ 30 years when restored sites were above mean high water neap (MHWN) tidal levels. Elevated marsh platforms likely provide suitable conditions for the development of mature plant communities associated with greater capture and production of organic carbon. The restored site at Tollesbury (Essex, UK) had a 2-fold lower carbon stock than other restored sites in the estuary. We attribute this to the site’s low position in the tidal frame, below MHWN tidal levels, coupled with low sediment supply and the dominance of pioneer plant communities. As blue carbon is anticipated to become an important facet of saltmarsh restoration, we recommend that sites above MHWN tidal levels are selected for managed realignment or that preference is given to coastlines with a high sediment supply that may rapidly elevate realignment sites above MHWN. Alternatively, elevation could be artificially raised prior to realignment. Restoration schemes aiming to maximise climate change mitigation should also encourage the establishment of key plant species (e.g., Atriplex portulacoides in our study) to enhance carbon stocks. However, the overall goal of restoration ought to be carefully considered as trade-offs in ecosystem services may ensue if restoration for climate change mitigation alone is pursued.

Comparison of Digestion Methods Using Atomic Absorption Spectrometry for the Determination of Metal Levels in Plants

Trace metal elements (TMEs) are among the most important types of pollutants in the environment. Therefore, a precise determination of these contaminants in several environmental components is required for the safety assurance of living organisms. Spectroscopic analysis is an efficient technique employed to detect and determine TME contents in numerous samples. Hence, to achieve reliable and accurate results when using spectroscopic analysis, samples should be carefully prepared. In the present study, the comparison of eight digestion methods of five vegetal samples was carried out to quantify Cd, Mn, Al and Mg contents using the atomic absorption spectroscopy technique. According to the extraction techniques used in this study, results showed an outstanding difference in TME levels determined in the same vegetal sample. The results obtained indicated that the highest Mn concentrations were recorded when using the mixture of HNO3-HClO4 in the studied species: atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279 compared to all other methods. Regarding the extraction of Cd, our results showed that heated extraction using different acids (HNO3-H2SO4-HClO4, HCl-HNO3, HNO3-HClO4, HNO3-H2SO4, HNO3-HCl-HClO4 and HNO3-HCl-H2SO4) was the most efficient in atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279. Similarly, these heated acid digestion techniques (efficient for Cd) showed the highest levels of Al in atriplex portulacoides and arthrocnemum indicum. However, for the Mg extraction, our results revealed that the effectiveness of the method used depended on the plant species studied. Regarding these findings, the efficiency of metal quantification by AAS depends on the digestion procedure, the metallic ion to determine and the plant species.

Dublin’s saltmarshes contain climate-relevant carbon pools

Wetland ecosystems, particularly coastal vegetated ecosystems, play a vital role in climate mitigation and adaptation. Coastal vegetated habitats (including coastal wetlands such as seagrass meadows, saltmarshes, and mangroves) are some of the most efficient ecosystems for storing carbon on a per hectare basis, retaining organic carbon for centuries to millennia. We conducted carbon stock assessments, to a depth of 1 m, across four young saltmarsh sites and the adjacent mudflats in Dublin, Ireland. Soil cores and vegetation samples were taken across each site in order to analyze the carbon content of each carbon pool. The carbon density of Dublin’s saltmarshes was 112.1 ± 10.1 Mg Corg ha−1. The dominant plant species were Spartina anglica, Plantago maritima, and Atriplex portulacoides. The soil carbon pool of these saltmarshes contributes 87% to the total carbon stock, with living plant biomass contributing the remaining 13%. Saltmarshes are important ecosystems for climate mitigation and can provide nature-based solutions to reduce net carbon emissions; however, their degradation will lead to the loss of climate-relevant carbon pools.

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.

Litter decomposition of three halophytes in a Mediterranean salt marsh: Relevance of litter quality, microbial activity and microhabitat.

Studies of litter decomposition in salt marshes have been mainly focused on the measurement of decomposition rates, being litter quality, the type of microbial decomposers and their extracellular enzyme activity, rarely considered. Moreover, most of these studies have been conducted in Poaceae and Cyperaceae species, being scarce the literature on Chenopodiaceae species, which are abundant in Mediterranean salt marshes. Here we analyse the litter decomposition process of two Chenopodiaceae (Sarcocornia fruticosa and Halimione portulacoides) and one Poaceae (Elytrigia atherica) species, belonging S. fruticosa to a halophilous scrub habitat and the other two to a salt meadow habitat of a Mediterranean salt marsh. For each species, we analysed litter decomposition rates, litter quality, fungal and bacterial biomass and potential extracellular enzymes activities. In order to embrace the spatial heterogeneity, two zones were considered within each habitat. Litter of E. atherica decomposed 7- and 13-fold slower than those of S. fruticosa and H. portulacoides, respectively, suggesting that this species is the one that would favour most the carbon sequestration into the soil. The different decomposition rates would be explained by the higher initial lignin and cellulose content of E. atherica rather than by the initial carbon and nitrogen content and C/N ratio. Moreover, enzyme efficiency, compared to enzyme activity, better contributes to explain the different decomposition rates observed. Bacteria dominated throughout the litter decomposition process regardless the species, but fungi increased their relevance in the later stages, when the relative lignin litter content increased. Litter decomposition was affected by microhabitat spatial differences, although the responses depended on the species. Hence, flooding (in the habitat of S. fruticosa) or soil texture (in the habitat of E. atherica and H. portulacoides) might have modulated the decomposition process, being H. portulacoides the most sensitive species to the spatial differences of the salt meadow habitat.

Halimione portulacoides biomass - a sustainable feedstock for bioenergy production from an integrated water-energy-food system

In view of a water-energy-food (WEF) nexus strategy, the present work assessed the bioenergy production potential of Halimione portulacoides used for the phytoremediation of nutrient-rich simulated wastewater from saltwater-based integrated multi-trophic aquaculture (IMTA). Specimens of this halophyte plant were grown in hydroponics under four different nutrient treatments with distinct nitrogen (N) and phosphorous (P) concentrations. Ultimate and proximate analysis, calorific value and thermogravimetric analysis coupled to mass spectrometry were used to assess the bioenergy potential of the non-edible biomass of the plants, namely the canes (C) and roots (R), and of commercial pellets (CP), which were used as benchmark. R and, especially, CP had higher carbon but lower oxygen content and larger volatiles but lower ashes than C. The higher heating values (HHV) of C (16–17 MJ kg−1) and R (17–18 MJ kg−1) were the same order as those of conventional energy crops and CP (20 MJ kg−1). Although mass loss and associated gaseous emissions during temperature programmed pyrolysis occurred mainly between 250 and 650 °C for all biomasses, they took place at slightly higher temperatures for C > CP > R. In any case, the integrated gaseous emissions during the pyrolysis of C, R, and CP were very similar and included H2, CH4, CO, and CO2 (syngas main constituents). Biomass production of C was affected by the nutrients load of the applied treatments, but this was not the case for R. Also, the nutrients treatments had no detectable effects on the biomasses’ ultimate or proximate analysis, HHV, thermal decomposition or resultant gaseous emissions. Thermal properties and behaviour of C and R were very similar to those of CP, showing their potential for bioenergy production and revealing that a WEF nexus strategy can be implemented in IMTA by energetic valorization of non-edible biomass of H. portulacoides used for water phytoremediation.

Bacterial assemblage in Mediterranean salt marshes: Disentangling the relative importance of seasonality, zonation and halophytes

Salt marshes gather a high diversity of prokaryotes across their environmental gradients. Most of this diversity and the factors determining their community assemblage are unknown. We massively sequenced a portion of the 16S gene to characterize the diversity of prokaryotes in soils from a salt marsh in Río Piedras, Southern Spain. We sampled in the four seasons, and in five plots dominated by a different halophyte (Spartina maritima, S. densiflora, Salicornia ramosissima, Arthrocaulon macrostachyum and Atriplex portulacoides) growing under different environmental conditions and representing different stages in the marsh ecological succession. Soil was sampled in their rhizosphere and adjacent bulk soil. We report the effects of different factors explaining prokaryotic beta diversity in the marsh: zonation (50 %), seasonality (14 %), and halophyte rhizosphere (7 %). Proteobacteria and Bacteroidota were the most abundant phyla. Firmicutes had a peak in winter and Desulfobacterota with other bacteria involved in sulfur cycling were abundant in the low marsh plots from S. maritima. Alpha diversity was highest in spring and decreased in winter. We detected a marked phylogenetic turnover between seasons and in rhizospheric soil respect to adjacent bulk soil for most pairwise comparisons. The effect of halophyte on its rhizosphere was species-specific, being S. maritima the species with more differentiated taxa between rhizosphere versus surrounding bulk soil. Our work highlights how the complex interaction between marsh zonation, seasonality and rhizosphere, onsets processes structuring bacterial community assemblage in salt marsh soils.

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.

Bioaugmentation Improves Phytoprotection in Halimione portulacoides Exposed to Mild Salt Stress: Perspectives for Salinity Tolerance Improvement.

Plant growth-promoting rhizobacteria (PGPR) can promote plant growth through mechanisms such as mineral phosphates solubilization, biological N2 fixation and siderophores and phytohormones production. The present work aims to evaluate the physiological fitness improvement by PGPR in Halimione portulacoides under mild and severe salt stress. PGPR-inoculated plants showed improved energy use efficiencies, namely in terms of the trapped and electron transport energy fluxes, and reduced energy dissipation. Allied to this, under mild stress, inoculated plants exhibited a significant reduction of the Na and Cl root concentrations, accompanied by a significant increase in K and Ca leaf content. This ion profile reshaping was intrinsically connected with an increased leaf proline content in inoculated plants. Moreover, bioaugmented plants showed an increased photoprotection ability, through lutein and zeaxanthin leaf concentration increase, allowing plants to cope with potentially photoinhibition conditions. Reduced Na leaf uptake in inoculated plants, apparently reduced the oxidative stress degree as observed by the superoxide dismutase and peroxidase activity reduction. Additionally, a reduced lipid peroxidation degree was observed in inoculated plants, while compared to their non-inoculated counterparts. These results, point out an important role of bioaugmentation in promoting plant fitness and improving salt tolerance, with a great potential for applications in biosaline agriculture and salinized soil restoration.

Assessment of Extraction Methods of Trace Metallic Elements in Plants: Approval of a Common Method

The question of trace metal elements (TME) is still relevant and causes several environmental problems. Moreover, the digestion methods of TME have a significant impact on ecosystems. Sample preparation is an important step of any analytical procedure. In fact, defining the levels of TME in vegetal tissues requires various steps: drying samples, crushing, extraction, and dosage. The use of chemical extraction solutions can be put into question. Other than their lack of specificity, they are susceptible to provoking the redistribution and/or re-fixation of a part of the metallic ions between the various vegetal components. Our study aims to test the procedures of extraction that are specific for the metals Cu, Zn, Fe, Ca, Cr and Ba. Our results show an outstanding difference in the levels of TME derived from the same vegetal sample, according to the various techniques of extraction. In fact, cold extraction by nitric acid diluted at 10% is the most efficient way to put the ions of Cu, Zn, Fe and Ca into a solution. Meanwhile, the use of heated extraction using different acid digestion approaches is the most efficient for Cr and Ba solubilization from Atriplex portulacoides, Arthrocnemum indicum, Olea europaea BCR-62, Ulva lactuca and Ulva lactuca BCR-279.

Nutritional valuation and food safety of endemic mediterranean halophytes species cultivated in abandoned salt pans under a natural irrigation scheme

Recent global changes have contributed to water scarcity and land degradation, urging for the development of alternative solutions in agriculture. Halophytes biosaline agriculture has been viewed in the past decades as a potential alternative to traditional agriculture practices in degraded lands and salinized soils. Abandoned salt pans provide ideal areas for halophyte cultivation, such as Halimione portulacoides (sea purslane), Sarcocornia fruticosa (shrubby swampfire), Atriplex halimus (sea orache), Beta maritima (sea beet), Inula crithmoides (golden samphire) and Suaeda vera (shrubby seablite). The use of a natural irrigation scheme with estuarine water for food production is a rather novel practice in the Mediterranean area. In the present work, we evaluate the nutritional value of these six halophytes cultivated in abandoned salt pans, irrigated with natural estuarine water. The halophytes produced under this cultivation scheme resulted in vegetable products with a high nutritional value. These edible halophyte presented low sugar content and high protein, omega-3 fatty acids and β-cryptoxanthin contents, together with a valuable source of highly concentrated phenolic and flavonoid anti-oxidant molecules. Moreover, these halophytes provide several mineral elements which are normally scarce in modern human diets (e.g. iodine and selenium), and very low concentrations, below the maximum thresholds, of carcinogenic elements. When compared to traditional vegetables, such as spinach, halophytes presented a high nutritional value, reinforcing the application of these cultivation schemes as means to attain highly nutritive alternative vegetable sources for a healthier human diet.

Halophyte Plants Cultured in Aquaponics Hold the Same Potential for Valorization as Wild Conspecifics from Donor Sites

Halophytes have gradually been introduced in marine integrated multi-trophic aquaculture (IMTA) systems due to their capacity to bioremediate nutrient-rich marine effluents and their potential use for human consumption due to their content of omega-3 and omega-6 fatty acids (FA). To foster the valorization of halophytes produced using an IMTA framework for human consumption, it is important that culture conditions keep or enhance their FA profile, when compared to that displayed by conspecifics in the wild. The main objective of the present study was to compare the FA profiles of three halophyte species (Halimione portulacoides, Salicornia ramosissima and Sarcocornia perennis) cultured in aquaponics coupled to an IMTA system with that of wild conspecifics retrieved from donor sites. The FA profiles were compared considering different plant organs (edible parts and roots) and sampling dates (spring, summer and autumn). Results show that the FA profiles of specimens cultured in aquaponics were significantly different from that of wild conspecifics, displaying a high content of omega-3 FAs in edible parts, particularly during summer, and mostly in the form of α-linolenic acid (ALA, 18:3n-3). In more detail, for the specimens cultured in aquaponics, ALA concentration in the edible parts of each species ranged from 5.10 to 7.11 μg mg−1 DW in H. portulacoides, from 5.66 to 9.19 μg mg−1 DW in S. ramosissima and from 5.49 to 7.20 μg mg−1 DW in S. perennis. Concerning the omega-6 linoleic acid (LA, 18:2n-6) identified in edible parts, the concentrations ranged from 2.25 to 2.46 μg mg−1 DW in H. portulacoides, from 3.26 to 4.84 μg mg−1 DW in S. ramosissima, and from 2.17 to 3.06 μg mg−1 DW in S. perennis. The nutritional quality was assessed through the ratio of PUFA/SFA, for both wild and cultured plants, and revealed values well above the threshold (0.45), the threshold value indicative of good nutritional quality. Overall, the culture conditions tested in the present work reinforce the potential of aquaponics coupled to marine IMTA to produce high-quality halophytes suitable for human consumption.

Sea Purslane as an Emerging Food Crop: Nutritional and Biological Studies

Halophyte plants are highly adapted to salt marsh ecosystems due to their physiological and ecological characteristics. Halimione portulacoides (L.) Aellen is one abundant halophyte shrub that belongs to a Chenopodiaceae family and Caryophyllales order and is found on sandy or muddy coastlines and salt marshes. In this study, the leaves of sea purslane (H. portulacoides) grown in Figueira da Foz (Portugal) were characterized at nutritional and mineral concentration. Moreover, different methanolic extracts were obtained from the leaves, and the antioxidant activity was assessed by several methods. From a nutritional point of view, this halophyte plant may be considered a good source of dietary fiber, protein, natural minerals such as calcium, magnesium, manganese, copper, and potassium. The primary sugar found in leaves of sea purslane is maltose, followed by sucrose, glucose, and fructose. Finally, leaves showed a high content of phenolic compounds and considerable antioxidant activity. The novel products butter and pasta enriched with powder dried leaves of H. portulacoides revealed the plant’s potential to be used as a salt substitute and a good alternative to enhance the sensory characteristics of products, with additional health benefits. The nutritional characteristics and the phytochemical value highlight H. portulacoides as a potential candidate crop in saline agriculture and to be used as a new vegetable, especially as a premium food in the novel “salty veggies” market or as a kitchen salt substitute.

Differential Nutrient Uptake by Saltmarsh Plants Is Modified by Increasing Salinity.

In Southern European estuaries and associated salt marshes, the anthropogenic nutrient inputs, together with longer drought periods, are leading to increasing eutrophication and salinization of these coastal ecosystems. In this study, uptake kinetics of ammonium, nitrate, and phosphate by three common plants in Palmones salt marsh (Southern Spain), Sarcocornia perennis ssp. alpini, Atriplex portulacoides, and Arthrocnemum macrostachyum were measured in hydroponic cultures. We also determined how these uptakes could be modified by increasing salinity, adding NaCl to the incubation medium (from 170 to 1,025 mM). Kinetic parameters are analyzed to understand the competition of the three species for nutrient resources under realistic most frequent concentrations in the salt marsh. These results may also be useful to predict the possible changes in the community composition and distribution if trends in environmental changes persist. Atriplex portulacoides showed the highest Vmax for ammonium, the most abundant nutrient in the salt marsh, while the highest affinity for this nutrient was observed in A. macrostachyum. Maximum uptake rates for nitrate were much lower than for ammonium, without significant differences among species. The highest Vmax value for phosphate was observed in A. macrostachyum, whereas A. portulacoides presented the highest affinity for this nutrient. High salinity drastically affected the physiological response of these species, decreasing nutrient uptake. Sarcocornia perennis ssp. alpini and A. macrostachyum were not affected by salinity up to 510 mM NaCl, whereas A. portulacoides notably decreased its uptake capacity at 427 mM and even withered at 1,025 mM NaCl. At current most frequent concentrations of ammonium and phosphate in the salt marsh, S. perennis ssp. alpini is the most favored species, from the nutritional point of view. However, A. portulacoides could enhance its presence if the increasing ammonium load continues, although a simultaneous salinization would negatively affect its nutritional physiology.

Primary succession in an Atlantic salt marsh: From intertidal flats to mid‐marsh platform in 35 years

Abstract Although salt marsh is a classic example of primary succession, the underlying mechanisms and their time‐scales are poorly understood. As salt marsh succession depends on sediment accretion, the amelioration of abiotic conditions associated with increasing elevation suggests potential explanatory roles for facilitation, competition and the stress‐gradient hypothesis. We present a 35‐year longitudinal study of salt marsh development from intertidal flat to a mid‐marsh platform at Odiel Marshes in south‐western Iberia. Using permanent plots, this work chronicles changes in elevation and marsh morphology, their evolving effects on sediment redox potential and salinity and the colonisation and changing patterns of dominance of halophytic species. Sporadically colonising clumps of the low‐marsh species Spartina maritima trapped sediment to form raised tussocks, which increased in elevation and area. Reduced tidal inundation and locally improved drainage promoted higher redox potentials and allowed colonisation by a sequence of species less tolerant of reducing conditions: Sarcocornia perennis, its hybrid with high‐marsh S. fruticosa, and Atriplex portulacoides. Unlike its centrifugally colonising predecessors, A. portulacoides invaded from the tussock edges. Transplant experiments designed to investigate its late establishment on tussocks showed that seedling survival depended on elevational differences as small as 4 cm. After increasing in elevation by c. 1 m (c. 29 mm/year), coalescence of the tussocks formed a marsh platform at a level corresponding to mean high tides. This supports a theoretical punctuated transition from ‘submergence marsh’ to ‘emergence marsh’, previously postulated for this tidal elevation. Synthesis. The unexpected rapidity of this primary succession highlights the central role of facilitation. Vertical sediment accretion, locally engineered by colonising species, progressively alleviates abiotic stress and allows colonisation by species that are less tolerant of chemically reducing conditions but are ultimately better competitors.

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.