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Tall monocots with long, linear leaves have lower canopy light attenuation than plants with horizontal leaves, yet little is known about their light acclimation and sun-shade responses. The genus Typha, common in nutrient-rich wetlands, is highly productive with dense canopies of such leaves. The objective of this study was therefore to investigate photosynthetic acclimation and pigment content in linear leaves of Typha latifolia L. in response to light availability. This was done in a growth experiment with two light intensities and in the field. In the laboratory, T. latifolia exhibited typical morphological, anatomical and gas exchange sun-shade responses. Net photosynthesis rates in high light were very high for a C3 plant (>40 mmol CO2 m-2 s-1) in both laboratory and field studies, and this was associated with stomatal conductances that were correspondingly high (maximum values >1.0 mol H2O m-2 s-1). The size of the xanthophyll (violaxanthin, antheraxanthin and zeaxanthin; VAZ) pool was also among the top 0.5% of all species. In the field, T. latifolia was able to maintain high net photosynthetic rates (26-41 mmol CO2 m-2 s-1) throughout its canopy and could avoid photoinhibition through high investment in the VAZ pool (0.7-1.3 mmol g-1 DW total VAZ pigments). This pattern of acclimation is likely to be adaptive, explaining why this species is so successful and dominant in high-light, high-nutrient wetland environments. [ABSTRACT FROM AUTHOR]

Hybrid Napier grass ( Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakchong1) is a candidate species for use as a bio-energy crop in plant-based water treatment systems due to its high growth and biomass production rate, ease of propagation and harvesting, and the quality of the biomass. We conducted a 2 × 3 factorial mesocosm experiment with two levels of inorganic N (100 μM and 1000 μM) and 3 water levels (0, 10 and 20 cm depth) and monitored the plant responses in terms of growth and biomass allocation, root morphology and leaf pigment concentrations to assess how hybrid Napier grass responds to a combination of flooding and high N concentrations. Under non-flooded but saturated soil conditions, hybrid Napier grass grew well at both N concentrations, but the tissue contents of minerals and nutrients were higher when plants grew at high N concentration. At 20 cm water depth and at the low N concentration, hybrid Napier grass acclimated to the flooded conditions by producing 2.5 times longer adventitious roots from the stem nodes and containing 3 times more lysigeneous aerenchyma compared to the plants grown at non-flooded conditions. At the high N concentration, hybrid Napier grass was not able to acclimate to the flooded conditions and had chlorotic leaves and reduced growth. Hybrid Napier grass can grow both under water-saturated and flooded soil conditions (up to 20 cm water depth) while maintaining high biomass production. If N concentrations are moderate (<1000 μM), hybrid Napier grass is therefore suitable for use in integrated plant-based water treatment and bio-energy crop production systems. [ABSTRACT FROM AUTHOR]

Background and aims: Aerenchymatous plants can affect methane (CH) emissions from wetland soils differently, and there is a need to understand specifically under which conditions plants enhance or attenuate CH emissions. Methods: We used a mesocosm set-up to assess the interactive effect of three water table positions (0 cm, −10 cm and −20 cm) and the presence or absence of Juncus effusus L on in vitro soil methanogenesis and methane emissions. Results: Soil methanogenesis and CH emission rates were significantly affected by water table position and vegetation, and the effect of vegetation depended on the water table position. At high water tables (−10 cm and 0 cm) soil methanogenesis and CH emissions were high and not significantly affected by vegetation, whereas at the low water table (−20 cm), methanogenesis and CH emission rates were lower in unvegetated soils than in soils with J. effusus. Conclusions: Methane emissions from organic wetland soils at low water tables may be enhanced by J. effusus because of increased methanogenesis and because CH enters the roots in the deeper anaerobic layers and are transported through the aerenchymatous tissue of the plants to the atmosphere bypassing the methanotrophic upper layers of the soils. [ABSTRACT FROM AUTHOR]

Plant cultivars with high biomass production may have a high potential for being used in integrated water treatment and plant production system. The highly productive hybrid Napier grass cultivar, Pennisetum purpureum × Pennisetum americanum cv. Pakchong1, may be a candidate species for being used in such systems. We studied the effects of inorganic nitrogen form (NH 4 + , NH 4 NO 3 or NO 3 − ) on growth, morphology, N uptake, water content and mineral allocation in this species under hydroponic conditions at equimolar concentrations (500 μmol N L −1 ). Generally, the N-form significantly affected growth, biomass allocation and tissue nutrient and mineral composition of the plants. The hybrid Napier grass grew better on NH 4 + compared to NO 3 − , and the plants supplied with NH 4 + contained three times more chlorophylls than plants supplied with NO 3 − alone or NO 3 − combined with NH 4 + . The morphology of the plants was, however, not affected by N source, except for the shoot to root ratio, which was lower in NH 4 + -fed plants. The relative water content of the leaves was lowest in the NH 4 + -fed plants, but the transpiration rate was not affected, indicating that NH 4 + nutrition and the associated low tissue concentration of K had negative effects on the water use efficiency of the plants. The study suggests that this hybrid Napier grass cultivar may be a new candidate species for use in integrated water treatment and plant production systems. [ABSTRACT FROM AUTHOR]

The largest Phragmites reed field in the world, with a historical area of approximately 1000 km 2 , is located in the Liaohe Delta in northeastern China. The Phragmites wetlands are extensively managed to maximize the production of reed biomass for the paper industry. Based on satellite remote sensing we estimated that the total area of the Phragmites wetlands has decreased from 857 km 2 in 2003 to 786 km 2 in 2009 to accommodate oil field infrastructure and societal developments. However, at the same time the production of Phragmites biomass used for the production of reed pulp has increased to 400,000 metric tons per year. This paper describes the great efforts that have been made to increase the Phragmites yields for the paper industry, including (1) diversion of freshwater from rivers to the Phragmites fields, (2) management of the water table, (3) harvesting and burning for pest control, and (4) seawater irrigation to rehabilitate Phragmites fields infested with weeds. The paper industry has facilitated the conservation of the Phragmites wetlands and their associated ecosystem services. Besides being a source for fiber, the wetlands provide important habitat for wildlife, sequester carbon, and create job opportunities and economic income for the local people. [ABSTRACT FROM AUTHOR]

In the Mississippi River Delta, the common wetland grass, Phragmites australis, displays high genetic diversity, as several genetically distinct populations are co-occurring. Differences in salinity tolerance may be an important factor determining these populations' distribution in the delta. Our study investigated the salt tolerance of four genotypes exposed to 0, 10, 20, 30, and 40 ppt salinity. The growth rate, biomass, and the light-saturated photosynthetic rate were stimulated at 10 ppt salinity and inhibited at salinities higher than 20 ppt, compared to controls. Increased concentrations of Cl and Na were found in the roots and older leaves of plants exposed to high salinities. Salt tolerance levels differed between genotypes. High salinity tolerance was mainly achieved by reduced water uptake and vacuole compartmentalization of toxic ions. The most tolerant genotype sustained biomass and photosynthesis even at 40 ppt, whereas the most sensitive genotype did not survive salinities higher than 20 ppt. Our findings show that the observed occurrence of different genotypes in the Mississippi River Delta is correlated to genetically determined differences in salinity tolerance. Further investigations are needed to better understand the role that salinity tolerance plays in the invasion of certain introduced P. australis genotypes. [ABSTRACT FROM AUTHOR]

The feasibility of using planted biofilters for purification of recirculated aquaculture water in the Mekong Delta of Vietnam was assessed. The plant trenches were able to clean tilapia aquaculture water and to maintain good water quality in the fish tanks without renewal of the water. NH4-N was removed efficiently in the plant trenches, particularly in the trenches with Canna glauca L., probably because of plant uptake and nitrification-denitrification. Plant uptake constituted 6% of N and 7% of P in the input feed. Approximately 1.0 m3 of water was needed per kg of fish produced, and 370, 97 and 2842 g fresh aboveground biomass of Ipomoea aquatica Forssk. , Lactuca sativa L. and C. glauca, respectively, were produced. The leafy vegetables provide some extra income besides fish products, whereas C. glauca provides nice flowers and contributes to a significant nutrient removal with annual uptake rates of 725 kg N and 234 kg P ha−1 year−1. This research demonstrates that integrated recirculating aquaculture-hydroponics (aquaponics) systems provide significant water savings and nutrient recycling as compared with traditional fish ponds. [ABSTRACT FROM AUTHOR]

Abstract: We studied the phenotypic plasticity of physiological and growth traits in two distinct clones of common reed (Phragmites australis (Cav.) Trin. Ex Steud.). Replicates of a clone from Denmark (DK clone) belonging to the European temperate P. australis and a clone from Algeria (ALG clone) belonging to the African-Mediterranean gene pool of P. australis were grown in phytotrons in a factorial block design at 15°C or 25°C daytime temperature and high or low fertilization level. Plant growth, tissue nutrient concentrations, photosynthetic pigments and photosynthetic characteristics were measured. Phenotypic plasticity was quantified for the measured traits as plasticity indices in relation to temperature and fertilization. The plasticity index was calculated as the difference between the maximum and the minimum mean value divided by the maximum mean value of a parameter within a treatment. The functional significance of the plasticity and its contribution to plant fitness was assessed by correlation of the plant traits to plant biomass as a proxy for fitness. The DK clone responded much more to temperature than the ALG clone, which responded more to fertilization, and both clones responded to high fertilization with lower allocation of biomass to roots and rhizomes. The ALG clone had a higher nutrient demand due to its large and fast biomass development. Hence, for most traits, the calculated plasticity indices for fertilization were highest for the ALG clone, especially within photosynthetic parameters and pigments, and the plasticity indices for temperature were highest for the DK clone, especially within growth parameters. In both clones, photosynthetic pigments, biomass allocation to leaf blades and rhizomes, the shoot:root ratio as well as leaf and shoot production rates were highly correlated to fitness. These traits also had a relatively high degree of plasticity, indicating a functional significance of plasticity, but several traits that showed high plasticity did not correlate with fitness (e.g. P max). We conclude that the responses of the two contrasting P. australis genotypes to temperature and fertilization are genetically determined and related to the climatic conditions at the site of their origin. Although phenotypic plasticity per se is not a precondition for plant fitness, the genetically determined differences in the degree of phenotypic plasticity of distinct P. australis genotypes to temperature and nutrient availability affect fitness and may influence how the genotypes will respond to global environmental change. [Copyright &y& Elsevier]

Abstract: We compared photosynthetic gas exchange, the photosynthesis–leaf nitrogen (N) relationship, and growth response to nutrient enrichment in the invasive wetland grass Glyceria maxima (Hartman) Holmburg with two native New Zealand Carex sedges (C. virgata Boott and C. secta Boott), to explore the ecophysiological traits contributing to invasive behaviour. The photosynthesis–nitrogen relationship was uniform across all three species, and the maximum light-saturated rate of photosynthesis expressed on a leaf area basis (A max a) did not differ significantly between species. However, specific leaf area (SLA) in G. maxima (17±6m2 kg−1) was 1.3 times that of the sedges, leading to 1.4 times higher maximum rates of photosynthesis (350–400nmolCO2 g−1 dry masss−1) expressed on a leaf mass basis (A max m) when N supply was unlimited, compared to the sedges (<300nmolCO2 g−1 dry masss−1). Analysis of Covariance (ANCOVA) revealed significant positive relationships between leaf N content and chlorophyll a:b ratios, stomatal conductance (g s ), dark respiration rate (R d ), and the photosynthetic light saturation point (I k ) in G. maxima, but not in the sedges. ANCOVA also identified that, compared to G. maxima, the sedges had 2.4 times higher intrinsic water use efficiency (A/g s : range 20–70 cf. 8–30μmolCO2 mol−1 H2O) and 1.6 times higher nitrogen use efficiency (NUE: 25–30 cf. 20–23gdry massg−1 N) under excess N supply. Relative growth rates (RGR) were not significantly higher in G. maxima than the sedges, but correlations between leaf N, gas exchange parameters (A max a, A max m, R d and g s ) and RGR were all highly significant in G. maxima, whereas they were weak or absent in the sedges. Allocation of biomass (root:shoot ratio, leaf mass ratio, root mass ratio), plant N and P content, and allocation of N to leaves all showed significantly greater phenotypic plasticity and stronger correlation to final biomass in G. maxima than in the sedges. We therefore conclude that photosynthesis and growth rates are not intrinsically higher in this invader than in the native species with which it competes, but that its success under nutrient enrichment is a consequence of greater physiological responsiveness and growth plasticity, and stronger integration between gas exchange and growth, coupled with indifference to resource wastage (i.e. low WUE and NUE) at high nutrient supply. The poorer performance of G. maxima than the sedges under low nutrient supply supports the importance of nutrient management, especially N, as a strategy to minimise the invasive behaviour of fast-growing herbaceous species in wetlands. [Copyright &y& Elsevier]

Abstract: High phenotypic plasticity has been hypothesized to affect the invasiveness of plants, as high plasticity may enlarge the breath of environments in which the plants can survive and reproduce. Here we compare the phenotypic plasticity of invasive and non-invasive populations of the same species in response to growth temperature. Populations of the submerged macrophyte Ceratophyllum demersum from New Zealand, where the species is introduced and invasive, and from Denmark, where the species is native and non-invasive, were grown in a common garden setup at temperatures of 12, 18, 25 and 35°C. We hypothesized that the phenotypic plasticity in fitness-related traits like growth and photosynthesis were higher in the invasive than in the non-invasive population. The invasive population acclimated to elevated temperatures through increased rates of photosynthesis (range: P amb: 8–452μmolO2 g−1 DMh−1) and relative growth rates (range: 0.01–0.05d−1) and associated regulations in the photosynthetic machinery. The non-invasive population had a lower acclimation potential (range: P amb: 43–173μmolO2 g−1 DMh−1; RGR: 0.01–0.03d−1), but was better at acclimating to cooler conditions by regulation of the light-harvesting complex. Hence, the invasive population of C. demersum from New Zealand had higher phenotypic plasticity in response to temperature than the non-invasive Danish population. This might be the result of genetic evolution since its introduction to New Zealand five decades ago, but further studies are needed to test this hypothesis. The study also indicate, that the global increase in temperature may exacerbate the problems experienced with the invasive C. demersum in New Zealand, as the performance and fitness of this population appear to be favoured at elevated temperatures. [Copyright &y& Elsevier]

Abstract: This study assesses the growth and morphological responses, nitrogen uptake and nutrient allocation in four aquatic macrophytes when supplied with different inorganic nitrogen treatments (1) NH4 +, (2) NO3 −, or (3) both NH4 + and NO3 −. Two free-floating species (Salvinia cucullata Roxb. ex Bory and Ipomoea aquatica Forssk.) and two emergent species (Cyperus involucratus Rottb. and Vetiveria zizanioides (L.) Nash ex Small) were grown with these N treatments at equimolar concentrations (500μM). Overall, the plants responded well to NH4 +. Growth as RGR was highest in S. cucullata (0.12±0.003d−1) followed by I. aquatica (0.035±0.002d−1), C. involucratus (0.03±0.002d−1) and V. zizanioides (0.02±0.003d−1). The NH4 + uptake rate was significantly higher than the NO3 − uptake rate. The free-floating species had higher nitrogen uptake rates than the emergent species. The N-uptake rate differed between plant species and seemed to be correlated to growth rate. All species had a high NO3 − uptake rate when supplied with only NO3 −. It seems that the NO3 − transporters in the plasma membrane of the root cells and nitrate reductase activity were induced by external NO3 −. Tissue mineral contents varied with species and tissue, but differences between treatments were generally small. We conclude, that the free-floating S. cucullata and I. aquatica are good candidate species for use in constructed wetland systems to remove N from polluted water. The rooted emergent plants can be used in subsurface flow constructed wetland systems as they grow well on any form of nitrogen and as they can develop a deep and dense root system. [Copyright &y& Elsevier]

Abstract: In 2007, a constructed wetland system was implemented on the tourist island of Koh Phi Phi in Southern Thailand. This paper presents the process of planning, designing and implementing the system and discusses the performance and operational issues 3 years after implementation. The system is an international lighthouse project showing the potential for aesthetical integration of constructed wetland systems in the built environment. The system comprises a wastewater collection system for the main business and hotel area of the island, a pumping station and a pressure pipe system to the treatment facility, a multi-stage constructed wetland system, and a system for reuse of treated wastewater. The treatment chains consist of vertical-flow, horizontal subsurface flow and free water surface flow units. Because the treatment system is located at the centre of the island, surrounded by resorts, restaurants and shops, the systems are designed with terrains as scenic landscaping. The wastewater is treated to meet the Thai effluent standards for total suspended solids and nitrogen, but because of inadequate pre-treatment and removal of oil and grease prior to the system, the standards for oil and grease and BOD are not met. A number of challenges during construction and operation have caused problems with clogging of the vertical flow constructed wetlands and given rise to odour problems. Safeguards were prepared, but not effectively activated, mainly because no key-person or key-authority took responsibility for managing the system. [Copyright &y& Elsevier]

Abstract: Luronium natans (L.) Raf. (Floating Water-plantain) is an endangered amphibious freshwater species endemic to Europe. We examined the plasticity in carbon acquisition and photosynthesis in L. natans to assess if lack of plasticity could contribute to explain the low competitive ability of the species. The plasticity of photosynthesis in submerged leaves towards inorganic carbon availability was examined and the photosynthesis of submerged, floating and aerial leaves was contrasted. L. natans was shown to be plastic in inorganic carbon uptake, as it was able to effectively acclimate to changed concentrations of free-CO2. The photosynthetic apparatus was down-regulated in plants grown at high CO2. Chlorophyll concentration, Rubisco activity and maximum photosynthesis were significantly lower in submerged leaves of plants grown at high CO2 (200μM free-CO2) compared to plants grown at low CO2 (18μM free-CO2). Furthermore, bicarbonate utilization was down-regulated in response to high CO2. Carbon acquisition of submerged, floating and aerial leaves of L. natans differed significantly. The aerial leaves were superior in photosynthesising in air and, surprisingly, the floating leaves had the highest rates of photosynthesis in water. The study did not support the hypothesis that the low competitive ability of L. natans is caused by inefficient photosynthesis or a lack of plasticity in photosynthesis. However, the somewhat low photosynthetic performance of the submerged leaves may be a contributing factor. [Copyright &y& Elsevier]

Abstract: The effects of inorganic nitrogen (N) source (NH4 +, NO3 − or both) on growth, biomass allocation, photosynthesis, N uptake rate, nitrate reductase activity and mineral composition of Canna indica were studied in hydroponic culture. The relative growth rates (0.05–0.06gg−1 d−1), biomass allocation and plant morphology of C. indica were indifferent to N nutrition. However, NH4 + fed plants had higher concentrations of N in the tissues, lower concentrations of mineral cations and higher contents of chlorophylls in the leaves compared to NO3 − fed plants suggesting a slight advantage of NH4 + nutrition. The NO3 − fed plants had lower light-saturated rates of photosynthesis (22.5μmolm−2 s−1) than NH4 + and NH4 +/NO3 − fed plants (24.4–25.6μmolm−2 s−1) when expressed per unit leaf area, but similar rates when expressed on a chlorophyll basis. Maximum uptake rates (V max) of NO3 − did not differ between treatments (24–35μmolNg−1 rootDWh−1), but V max for NH4 + was highest in NH4 + fed plants (81μmolNg−1 rootDWh−1), intermediate in the NH4NO3 fed plants (52μmolNg−1 rootDWh−1), and lowest in the NO3 − fed plants (28μmolNg−1 rootDWh−1). Nitrate reductase activity (NRA) was highest in leaves and was induced by NO3 − in the culture solutions corresponding to the pattern seen in fast growing terrestrial species. Plants fed with only NO3 − had high NRA (22 and 8μmolNO2 − g−1 DWh−1 in leaves and roots, respectively) whereas NRA in NH4 + fed plants was close to zero. Plants supplied with both forms of N had intermediate NRA suggesting that C. indica takes up and assimilate NO3 − in the presence of NH4 +. Our results show that C. indica is relatively indifferent to inorganic N source, which together with its high growth rate contributes to explain the occurrence of this species in flooded wetland soils as well as on terrestrial soils. Furthermore, it is concluded that C. indica is suitable for use in different types of constructed wetlands. [Copyright &y& Elsevier]

Background: Cattail (Typha domingensis) has been spreading in phosphorus (P) enriched areas of the oligotrophic Florida Everglades at the expense of sawgrass (Cladium mariscus spp. jamaicense). Abundant evidence in the literature explains how the opportunistic features of Typha might lead to a complete dominance in P-enriched areas. Less clear is how Typha can grow and acquire P at extremely low P levels, which prevail in the unimpacted areas of the Everglades. Results: Apparent P uptake kinetics were measured for intact plants of Cladium and Typha acclimated to low and high P at two levels of oxygen in hydroponic culture. The saturated rate of P uptake was higher in Typha than in Cladium and higher in low-P acclimated plants than in high-P acclimated plants. The affinity for P uptake was twofold higher in Typha than in Cladium, and two- to three-fold higher for low-P acclimated plants compared to high- P acclimated plants. As Cladium had a greater proportion of its biomass allocated to roots, the overall uptake capacity of the two species at high P did not differ. At low P availability, Typha increased biomass allocation to roots more than Cladium. Both species also adjusted their P uptake kinetics, but Typha more so than Cladium. The adjustment of the P uptake system and increased biomass allocation to roots resulted in a five-fold higher uptake per plant for Cladium and a ten-fold higher uptake for Typha. Conclusions: Both Cladium and Typha adjust P uptake kinetics in relation to plant demand when P availability is high. When P concentrations are low, however, Typha adjusts P uptake kinetics and also increases allocation to roots more so than Cladium, thereby improving both efficiency and capacity of P uptake. Cladium has less need to adjust P uptake kinetics because it is already efficient at acquiring P from peat soils (e.g., through secretion of phosphatases, symbiosis with arbuscular mycorrhizal fungi, nutrient conservation growth traits). Thus, although Cladium and Typha have qualitatively similar strategies to improve P-uptake efficiency and capacity under low Pconditions, Typha shows a quantitatively greater response, possibly due to a lesser expression of these mechanisms than Cladium. This difference between the two species helps to explain why an opportunistic species such as Typha is able to grow side by side with Cladium in the P-deficient Everglades. [ABSTRACT FROM AUTHOR]

Abstract: Preference for NH4 + or NO3 − nutrition by the perennial legume Sesbania sesban (L.) Merr. was assessed by supplying plants with NH4 + and NO3 − alone or mixed at equal concentrations (0.5mM) in hydroponic culture. In addition, growth responses of S. sesban to NH4 + and NO3 − nutrition and the effects on root nodulation and nutrient and mineral composition of the plant tissues were evaluated in a hydroponic setup at a range of external concentration of NH4 + and NO3 − (0, 0.1, 0.2, 0.5, 2 and 5mM). Seedlings of S. sesban grew equally well when supplied with either NH4 + or NO3 − alone or mixed and had high relative growth rates (RGRs) ranging between 0.19 and 0.21d−1. When larger plants of S. sesban were supplied with NH4 + or NO3 − alone, the RGRs and shoot elongation rates were not affected by the external concentration of inorganic N. At external N concentrations up to 0.5mM nodulation occurred and contributed to the N nutrition through fixation of gaseous N2 from the atmosphere. For both NH4 + and NO3 −-fed plants the N concentration in the plant tissues, particularly water-extractable NO3 −, increased at high supply concentrations, and concentrations of mineral cations generally decreased. It is concluded that S. sesban can grow without an external inorganic N supply by fixing atmospheric N2 gas via root nodules. Also, S. sesban grows well on both NH4 + and NO3 − as the external N source and the plant can tolerate relatively high concentrations of NH4 +. This wide ecological amplitude concerning N nutrition makes S. sesban very useful as a N2-fixing fallow crop in N deficient areas and also a candidate species for use in constructed wetland systems for the treatment of NH4 + rich waters. [Copyright &y& Elsevier]

Abstract: The effects of NaCl salinity on growth, morphology and photosynthesis of Salvinia natans (L.) All. were investigated by growing plants in a growth chamber at NaCl concentrations of 0, 50, 100 and 150mM. The relative growth rates were high (ca. 0.3d−1) at salinities up to 50mM and decreased to less than 0.2d−1 at higher salinities, but plants produced smaller and thicker leaves and had shorter stems and roots, probably imposed by the osmotic stress and lowered turgor pressure restricting cell expansion. Na+ concentrations in the plant tissue only increased three-fold, but uptake of K+ was reduced, resulting in very high Na+/K+ ratios at high salinities, indicating that S. natans lacks mechanisms to maintain ionic homeostasis in the cells. The contents of proline in the plant tissue increased at high salinity, but concentrations were very low (<0.1μmolg−1 FW), indicating a limited capacity of S. natans to synthesize proline as a compatible compound. The potential photochemical efficiency of PSII (F v/F m) of S. natans remained unchanged at 50mM NaCl but was reduced at higher salinities, and the photosynthetic capacity (ETRmax) was significantly reduced at 50mM NaCl and higher. It is concluded that S. natans is a salt-sensitive species lacking physiological measures to cope with exposure to high NaCl salinity. At low salinities salts are taken up and accumulate in old leaves, and high growth rates are maintained because new leaves are produced at a higher rate than for plants not exposed to salt. [Copyright &y& Elsevier]

Abstract: The ability of Salvinia natans (L.) All. to tolerate growth in oxic, hypoxic and anoxic nutrient solutions when supplied with either NH4 + or NO3 − were studied in the laboratory to test the hypothesis that inorganic N-source affects the response of the plants to O2 deprivation. The relative growth rate (RGR) was significantly reduced in the anoxic treatment, but in the hypoxic treatment RGR was only slightly affected. The NH4 + fed plants generally had a higher shoot to root ratio than the NO3 − fed plants, and highest in the anoxic treatment. Plants had more roots and larger leaves when supplied with NH4 + as compared with NO3 −, particularly in the oxic treatment, and root length was most affected by O2 deprivation for NO3 − fed plants. Cell walls in the endodermis, the bundle sheath and the cortex adjacent to endodermis developed thickened sclerenchymatous walls when deprived of O2, and more so in plants supplied with NO3 −. Plants lost chlorophylls, had lower rates of photosynthetic electron transport (ETRmax) and lower quantum yields (Fv/Fm ratios) when grown in anoxic solutions, and the negative effects were mildest for NO3 − fed plants suggesting that NO3 − may be used as an alternative e−-acceptor in non-cyclic electron transport in the chloroplasts. Overall S. natans grew best on NH4 +, but it also grew well on NO3 −, and the O2 stress symptoms differed somewhat between NH4 + fed and NO3 − fed plants. However, because N-form itself significantly influenced morphology and cell metabolism, it was impossible to conclusively identify the role of N-form for the O2 stress reactions. S. natans is not well-adapted to grow in O2 deficient waters and will not tolerate completely anoxic conditions as will prevail in waters receiving high loadings of organic pollutants such as livestock wastewater. [Copyright &y& Elsevier]

Abstract: Many plants develop toxicity symptoms and have reduced growth rates when supplied with ammonium (NH4 +) as the only source of inorganic nitrogen. In the present study, the growth, morphology, NH4 + uptake kinetics and mineral concentrations in the tissues of the free-floating aquatic plant Salvinia natans (water fern) supplied exclusively with NH4 +–N at concentrations of 0.25–15mM were investigated. S. natans grew well, with relative growth rates of c. 0.25gg−1 d−1 at external NH4 + concentrations up to 5mM, but at higher levels growth was suppressed and the plants had small leaves and short roots with stunted growth. The high-affinity transport system (HATS) that mediate NH4 + uptake at dilute NH4 + levels was downregulated at high NH4 + concentrations with lower velocities of maximum uptake (V max) and higher half-saturation constants (K 1/2). High NH4 + levels also barely affected the concentrations of mineral cations and anions in the plant tissue. It is concluded that S. natans can be characterized as NH4 +-tolerant in line with a number of other species of wetland plants as growth was unaffected at NH4 + concentrations as high as 5mM and as symptoms of toxicity at higher concentrations were relatively mild. Depolarization of the plasma membrane to the equilibrium potential for NH4 + at high external concentrations may be a mechanism used by the plant to avoid excessive futile transmembrane cycling. S. natans is tolerant to the high NH4 + levels that prevail in domestic and agricultural wastewaters, and the inherent high growth rate and the ease of biomass harvesting make S. natans a primary candidate for use in constructed wetland systems for the treatment of various types of nitrogen-rich wastewaters. [Copyright &y& Elsevier]

Abstract: In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO3 −, NH4 +, or both at equimolar concentrations (500μM). Plants supplied with only NO3 − had lower growth rates (0.17±0.01gg−1 d−1), shorter roots, smaller leaves with less chlorophyll than plants supplied with NH4 + alone or in combination with NO3 − (RGR=0.28±0.01gg−1 d−1). Ammonium was the preferred form of N taken up. The maximal rate of NH4 + uptake (V max) was 6–14 times higher than the maximal uptake rate of NO3 − and the minimum concentration for uptake (C min) was lower for NH4 + than for NO3 −. Plants supplied with NO3 − had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO3 − was primarily reduced in the roots, but NRA levels were generally low (<4μmolNO2 − g−1 DWh−1). Under natural growth conditions NH4 + is probably the main N source for S. natans, but plants probably also exploit NO3 − when NH4 + concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH4 + levels in the water, even though the uptake capacity for NO3 − is reduced under these conditions. [Copyright &y& Elsevier]

Abstract: Official guidelines for the on-site treatment of domestic sewage have recently been published by the Danish Ministry of Environment as a consequence of new treatment requirements for single houses and dwellings in rural areas. This paper summarises the guidelines for vertical constructed wetland systems (planted filter beds) that will fulfil demands of 95% removal of BOD and 90% nitrification. The system can be extended with chemical precipitation of phosphorus with aluminium polychloride in the sedimentation tank to meet requirements of 90% phosphorus removal. The necessary surface area of the filter bed is 3.2m2/person equivalent and the effective filter depth is 1.0m. The filter medium must be filtersand with a d 10 between 0.25 and 1.2mm, a d 60 between 1 and 4mm, and a uniformity coefficient (U = d 60/d 10) less than 3.5. The sewage is, after sedimentation, pulse-loaded onto the surface of the bed using pumping and a network of distribution pipes. The drainage layer in the bottom of the bed is passively aerated through vertical pipes extending into the atmosphere in order to improve oxygen transfer to the bed medium. Half of the nitrified effluent from the filter is recirculated to the first chamber of the sedimentation tank or to the pumping well in order to enhance denitrification and to stabilise the treatment performance of the system. A phosphorus removal system is installed in the sedimentation tank using a small dosing pump. The mixing of chemicals is obtained by a simple airlift pump, which also circulates water in the sedimentation tank. The vertical flow constructed wetland system is an attractive alternative to the common practice of soil infiltration and provides efficient treatment of sewage for discharge into the aquatic environment. [Copyright &y& Elsevier]

It is widely documented that vertical flow constructed wetlands are efficient for producing well nitrified effluent. However, because the treated effluent is oxygen saturated and has a low availability of carbon, the removal of total nitrogen is limited. We hypothesize that by recycling the fully nitrified effluent to the pretreatment unit and the sedimentation tank (where conditions are favorable for denitrification) the removal of total nitrogen from the wastewater can be enhanced. In order to assess the effects of recycling volumes, we monitored the nitrogen removal in an experimental vertical flow constructed wetland, consisting of a 2 m³ sedimentation tank, two vertical flow beds of 10 and 5 m², and the necessary pumping equipment and controllers to manage the loading and recycling volumes. The system was loaded with approximately 0.5 m³ d&sup-1;, and the recycling volumes evaluated were equal to the loading rate (100% recycling), as well as twice (200%) and three times (300%) the loading. The system produced a fully nitrified effluent independent of recycling rate. However, recycling increased removal of total-N in the system from ca. 1% removal when there was no recycling to 52%, 66%, and 68% removal with 100, 200, and 300% recycling, respectively. The optimal recycling rate seems to be 100-200%. At lower recycling rates, the removal of total-N was poor, and at higher recycling rates, the system became hydraulically overloaded, compromising both the denitrification capacity of the sedimentation tank and the nitrification capacity of the vertical bed. [ABSTRACT FROM AUTHOR]

The NH4+ and NO3– uptake kinetics by Typha latifolia L. were studied after prolonged hydroponics growth at constant pH 3.5, 5.0, 6.5 or 7.0 and with NH4+ or NO3– as the sole N‐source. In addition, the effects of pH and N source on H+ extrusion and adenine nucleotide content were examined. Typha latifolia was able to grow with both N sources at near neutral pH levels, but the plants had higher relative growth rates, higher tissue concentrations of the major nutrients, higher contents of adenine nucleotides, and higher affinity for uptake of inorganic nitrogen when grown on NH4+. Growth almost completely stopped at pH 3.5, irrespective of N source, probably as a consequence of pH effects on plasma membrane integrity and H+ influx into the root cells. Tissue concentrations of the major nutrients and adenine nucleotides were severely reduced at low pH, and the uptake capacity for inorganic nitrogen was low, and more so for NO3–‐fed than for NH4+‐fed plants. The maximum uptake rate, Vmax, was highest for NH4+ at pH 6.5 (30.9 µmol h–1 g–1 root dry weight) and for NO3– at pH 5.0 (31.7 µmol h–1 g–1 root dry weight), and less than 10% of these values at pH 3.5. The affinity for uptake as estimated by the half saturation constant, K½, was lowest at low pH for NH4+ and at high pH for NO3–. The changes in Vmax and K½ were thus consistent with the theory of increasing competition between cations and H+ at low pH and between anions and OH– at high pH. Cmin was independent of pH, but slightly higher for NO3– than for NH4+ (Cmin(NH4+) ∼ 0.8 mmol m–3; Cmin(NO3–) ∼ 2.8 mmol m–3). The growth inhibition at low pH was probably due to a reduced nutrient uptake and a consequential limitation of growth by nutrient stress. Typha latifolia seems to be well adapted to growth in wetland soils where NH4+ is the prevailing nitrogen compound, but very low pH levels around the roots are very stressful for the plant. The common occurrence of T. latifolia in very acidic areas is probably only possible because of the plant’s ability to modify pH‐conditions in the rhizosphere. [ABSTRACT FROM PUBLISHER]

Compares the efficiency of aquaculture, constructed wetlands and wastewater treatment systems in water pollution control. Ecological engineering; Life-cycle assessment; Living machine technology.

The ability of diffusive gas transport and pressurized, convective flow to satisfy internal oxygen demands was examined for an aquatic sedge, Eleocharis sphacelata R. Br.. Resistances to convention and diffusion through the plant were quantified form anatomical studies of the airspace dimensions, and these were used in mathematical models to calculate the fluxes required to satisfy oxygen demands measured in the tissue. The greatest resistance to diffusion in the underwater tissue was the submerged culm between the waterline and sediment surface (1560 Ms m-3 per m culm length). Resistances of the nodal intercalary meristem (52 Ms m-3) and rhizome internode (34 Ms m-3) were minor. In contrast resistances to convection were low in the culms (38 MPa s m-3 per m culm length), and higher in the nodal meristems (93 MPa s m-3). The rhizome internodes had large cortical canals with a low convective resistance (0.75 MPa s m-3), and a parallel spongy pith with a very high resistance (518 MPa s m-3) that is probably short-circuited by convection. The resistance of the submerged culm mean s that diffusion is inadequate to satisfy oxygen demands in plants growing in > 10 cm of water, and that convective oxygen influx as low as 2.8 × 10-8 mol s-1 per culm (equivalent to a gas flow rate of 3 μl s -1 per culm) could satisfy the entire oxygen demand of the underwater issue; this value is well below actual rates. At this flow rate, the spongy pith in the rhizome would also remain aerobic; it has a low resistance to diffusion (73 Ms m-3) and could receive sufficient oxygen by diffusion from the node. The data agree well with previous empirical measurements of convection in this species and show that diffusion and convection are both important processes for it aeration. [ABSTRACT FROM AUTHOR]

During the last two decades the multiple functions and values of wetlands have been recognized not only by the scientists and managers working with wetlands, but also by the public. The ability of wetlands to transform and store organic matter has been exploited in constructed wetlands. This paper summarizes the state-of-the-art of the uses of constructed wetlands in water pollution control by reviewing the basics of the technology, the historical development, and the performance expectations with focus on the use of free water surface and subsurface flow constructed wetlands for municipal wastewater treatment. Performance data from a total of 104 subsurface flow systems and 70 free water surface flow systems are reviewed. The present state of knowledge is sufficient to apply constructed wetlands as a tool for improving water quality. The potential applications range from secondary treatment of municipal and various types of industrial wastewaters to polishing of tertiary treated waters and diffuse pollution. In many situations constructed wetlands is the only appropriate technology available. The treatment capacity of subsurface flow systems can be improved by selecting vertical flow systems with intermittent loading, by proper media selection, and by recycling of the wastewater. Further research is needed to help define and optimize engineering design criteria and the long-term performance capabilities and operational problems. [ABSTRACT FROM AUTHOR]

Anaerobic digester effluent contains high concentrations of nutrients and other contaminants and has low dissolved oxygen. While there is increased interest nowadays in using constructed wetlands to treat wastewater, the ability of the wetland plants to grow in these stressful conditions is scantily investigated. Hence, this research investigated the growth performance of two tropical wetland species (Cyperus involucratus and Thalia geniculata) in anaerobic digester effluent and assessed their potential for treating the wastewater. Both C. involucratus and T. geniculata grew well in the wastewater probably because of aerenchyma development (28% air-space tissue) in the roots and radial oxygen loss from the roots. The pollutant level in the anaerobic digester effluent was significantly reduced with high removals of BOD (96–100%) and COD (69–73%). The remove of nutrients differed between species. T. geniculata had the better removal of PO 4 -P (48%), whereas C. involucratus had the better removal of NH 4 -N (99% in 28 days) and inorganic N (64% in 56 days). The removal of TSS (87–88%), EC (36–38%) and TDS (51–54%) in the systems were not significantly different between the two species. The study suggests that C. involucratus is a good candidate species for N removal in constructed wetlands whereas T. geniculata is better for removal of P. • Both species acclimated well to high concentrated anaerobic digester effluent. • Aerenchyma formed in roots can supports plants growing under low O 2 condition. • Increase DO in wastewater has significant correlation with number of plant roots. • T. geniculata had better PO 4 -P removal while C. involucratus had higher N removal. • Both species performed well to remove BOD, COD and TSS. [ABSTRACT FROM AUTHOR]

Within‐species genetic diversity is shaped by multiple evolutionary forces within the confines of geography, and has cascading effects on the biodiversity of other taxa and levels. Invasive species are often initially limited in genetic diversity but still respond rapidly to their new range, possibly through 'pre‐adapted' genotypes or multiple sources of genetic diversity, but little is known about how their genetic structure differs from that of native species and how it alters the genetic‐species diversity relationship. Here, we selected a widespread native species Phragmites australis and its co‐occurring invasive competitor Spartina alterniflora as our model plant species. We investigated the genetic structure of P. australis using two chloroplast fragments and ten nuclear microsatellites in 13 populations along the Chinese coastal wetlands. We discovered a distinct geographical differentiation, showing that the northern and southern populations harbored unique genotypes. We also found a significant increase in genetic diversity (allelic richness and expected heterozygosity) from south to north. Combined with previous studies of S. alterniflora, the Mantel tests revealed a significant correlation of genetic distances between P. australis and S. alterniflora even when controlling for geographic distance, suggesting that the invasive species S. alterniflora might exhibit a phylogeographic pattern similar to that of the native species to some extent. Furthermore, our results suggest that the S. alterniflora invasion has altered the relationship between the genetic diversity of the dominant native plant and the associated species richness of soil nematodes. The reason for the alteration of genetic‐species diversity relationship might be that the biological invasion weakens the environmental impact on both levels of biodiversity. Our findings contribute to understanding the latitudinal patterns of intraspecific genetic diversity in widespread species. This work on the genetic diversity analysis of native species also provides significant implications for the invasion stage and ecological consequences of biological invasions. [ABSTRACT FROM AUTHOR]

Background Coastal wetlands are threatened by the increased salinity that may result from sea level rise. Salinity stress alters species zonation patterns through changes in competitive outcome between species differing in salinity tolerance. This study therefore aimed to understand how salinity and light affect two dominant and competing coastal wetland grasses that differ in salt tolerance, height and photosynthetic metabolism. Methods The C4 species Spartina anglica and the C3 species Phragmites australis were grown at five salinity levels (0, 7, 14, 21 and 28 ppt) and two light fluxes (100 % and 50 % of natural daylight) in an outdoor experimental setup for 102 d with full access to nutrients. Key Results Salinity reduced the biomass, height and shoot density of P. australis from 81.7 g dry weight (DW), 0.73 m and 37 shoots per pot at a salinity of 0 ppt to 16.8 gDW, 0.3 m and 14 shoots per pot at a salinity of 28 ppt. Biomass, height and shoot density of S. anglica did not respond or were only slightly reduced at the highest salinity of 28 ppt. High salinity also resulted in a higher tissue concentration of N and P in P. australis. Both species had low ability to acclimate to the lower light flux. Shade acclimation in S. anglica occurred via modest changes in specific leaf area, pigment content and biomass allocation. Conclusions High salinity reduced traits important for light competition and increased the nutrient concentration in P. australis leaf and root biomass, while this was overall unaffected in S. anglica. This is likely to reduce the competitive ability of P. australis over S. anglica for light because at high salinities the former cannot effectively shade the lower-growing S. anglica. Neither species effectively acclimates to shade, which could explain why S. anglica does not occur in the understorey of P. australis at low salinities. [ABSTRACT FROM AUTHOR]

Aims: Coastal salt marshes are productive ecosystems that are highly efficient carbon sinks, but there is uncertainty regarding the interactions among climate warming, plant species, and tidal restriction on C cycling. Methods: Open-top chambers (OTCs) were deployed at two coastal wetlands in Yancheng, China, where native Phragmites australis (Phragmites) and invasive Spartina alterniflora (Spartina) were dominant, respectively. Two study locations were set up in each area based on difference in tidal action. The OTCs achieved an increase of average daytime air temperature of ~ 1.11–1.55 °C. Net ecosystem CO2 exchange (NEE), ecosystem respiration (Reco), CH4 fluxes, aboveground biomass and other abiotic factors were monitored over three years. Results: Warming reduced the magnitude of the radiative balance of native Phragmites, which was determined to still be a consistent C sink. In contrast, warming or tidal flooding presumably transform the Spartina into a weak C source, because either warming-induced high salinity reduced the magnitude of NEE by 19% or flooding increased CH4 emissions by 789%. Remarkably, native Phragmites affected by tidal restrictions appeared to be a consistent C source with the radiative balance of 7.11–9.64 kg CO2-eq m–2 yr–1 because of a reduction in the magnitude of NEE and increase of CH4 fluxes. Conclusions: Tidal restrictions that disconnect the tidal hydrologic connection between the ocean and land may transform coastal wetlands from C sinks to C sources. This transformation may potentially be an even greater threat to coastal carbon sequestration than climate warming or invasive plant species in isolation. [ABSTRACT FROM AUTHOR]

Purpose: Most Pseudomonas spp. are iron (Fe) redox cycling bacteria, which are common in the rhizosphere of wetland plants. The purpose of this work was to investigate the influence of P. sp. SCSWA09, a Fe reducing bacterium isolated from mangrove plant Kandelia obovata, on the development of Fe plaques as well as the accumulation and translocation of heavy metals (HMs) in K. obovata. Methods: A controlled experiment was conducted in a climate chamber using K. obovata as model plants to evaluate the effect of P. sp. SCSWA09 on the development of Fe plaque and the plants' response to HM stress under periodic flooding conditions. Results: The results demonstrated that SCSWA09 had a clear capacity to reduce Fe (III). K. obovata seedlings inoculated with SCSWA09 showed considerably lower levels of Fe plaque production than uninoculated seedlings, notably the amorphous Fe plaque. Periodic flooding accelerated the transformation of amorphous Fe (hydrogen) oxide into crystalline Fe (hydrogen) oxide in Fe plaque, and SCSWA09 inoculation accelerated this process. The buildup of Cr and Cu in K. obovata roots steadily reduced as the flooding period rose, but SCSWA09 inoculation significantly increased Cr translocation to K. obovata leaves. Conclusion: Both SCSWA09 and periodic flooding enhanced the crystallinity of iron (hydr-) oxides in the treatment solution and Fe plaque, which influenced HM absorption and translocation in plants. [ABSTRACT FROM AUTHOR]

The present study examined the effects of three recirculation rates (50%, 200% and 400%) on water quality and biomass growth at low and high fish stocking densities (122 and 220 fish/m 3 ) in aquaponic systems. The system consisted of a Tilapia tank connected to a gravel filter and three hydroponic trenches in series with Ipomoea aquatica , Lactuca sativa and Canna glauca . The RRs influenced most water quality parameters with best water quality at the high RR. At the low RR of 50% mass mortality of fish occurred due to lack of oxygen. The fish growth and survival was excellent in the high RR of 400% at the low fish density of 122 fish/m 3 . The plant trenches were found to be effective in removing potential harmful concentrations of NH 4 -N and NO 2 -N from the recirculating water. For each kg of fish produced in this system approximately 1.0 m 3 water was needed. During a 25-day period about 1 kg of marketable fresh biomass of I. aquatica and 270 g dry weight aboveground biomass of C. glauca was produced. It is concluded that high recirculation rate of the water of 200–400% per day is needed to secure a good growth and a low FCR of Tilapia in aquaponic systems. High recirculation rates also secure a good water quality. The aquaponic system has a very low effluent discharge compared to traditional aquaculture techniques, and it recycles nutrients for plant growth. Hence, aquaponic system is a promising sustainable solution that can be applied on commercial fish pond scale. [ABSTRACT FROM AUTHOR]

The present study examined the effects of three recirculation rates (50%, 200% and 400%) on water quality and biomass growth at low and high fish stocking densities (122 and 220 fish/m 3 ) in aquaponic systems. The system consisted of a Tilapia tank connected to a gravel filter and three hydroponic trenches in series with Ipomoea aquatica , Lactuca sativa and Canna glauca . The RRs influenced most water quality parameters with best water quality at the high RR. At the low RR of 50% mass mortality of fish occurred due to lack of oxygen. The fish growth and survival was excellent in the high RR of 400% at the low fish density of 122 fish/m 3 . The plant trenches were found to be effective in removing potential harmful concentrations of NH 4 -N and NO 2 -N from the recirculating water. For each kg of fish produced in this system approximately 1.0 m 3 water was needed. During a 25-day period about 1 kg of marketable fresh biomass of I. aquatica and 270 g dry weight aboveground biomass of C. glauca was produced. It is concluded that high recirculation rate of the water of 200–400% per day is needed to secure a good growth and a low FCR of Tilapia in aquaponic systems. High recirculation rates also secure a good water quality. The aquaponic system has a very low effluent discharge compared to traditional aquaculture techniques, and it recycles nutrients for plant growth. Hence, aquaponic system is a promising sustainable solution that can be applied on commercial fish pond scale. [ABSTRACT FROM AUTHOR]

Microorganisms, including the bacterial populations living inside plant tissues (endophytes), and vegetation are components of constructed wetland (CW) systems playing pivotal roles in the water treatment process and in the ecosystem establishment. The present study focuses on the assessment of the culturable endophytic bacterial communities of Canna flaccida plants, the dominant plant species in a polycultured CW treating wastewater from a tourism facility. Bacterial endophytes were grouped by random amplified polymorphic DNA and identified by 16S ribosomal RNA gene sequencing. From the bacterial isolates, 103 were considered for phylogenetic analysis, falling in 25 genera within the γ-, β-, α-Proteobacteria , Flavobacteria , Sphingobacteria , Actinobacteria and Bacilli classes. Forty-nine percent of the isolates belonged to the Enterobacteriaceae family, suggesting that the plants in CW systems may act as a sink of potential human pathogenic microorganisms; nevertheless their abundance on the plant tissues was reduced from the inlet (62%) to the outlet zone (38%). High diversity in terms of genera was found in C. flaccida tissues, although the number of genera common to both sampling zones was low, which suggests that the processes occurring within the CW, including the water characteristics gradient from the inlet to the outlet (e.g. total suspended solids, organics and fecal loads), had the ability to shape the diversity of the endophytic communities. [ABSTRACT FROM AUTHOR]

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling. [ABSTRACT FROM AUTHOR]

The use of constructed wetlands (CWs) is a promising approach for the remediation of hydrocarbon-polluted wastewater. The amendments of CWs with nutrients, surfactants, and aeration enhances the removal of pollutants from wastewater. The objective of the present study was to explore the effect of external stimulants, i.e., nutrients, surfactant, and aeration on hydrocarbons degradation potential of CWs. The CWs mesocosms were developed by the vegetation of Phragmites australis and amendments with nutrients (20 mg l−1 N, 2.6 mg l−1 P, and 16.4 mg l−1 K), surfactant Tween 20 (0.2%, v/v), and aeration (7 mg l−1) for the remediation of diesel-spiked water (2%, w/v). The comparative analysis showed that the addition of nutrients, surfactant, and aeration individually enhanced total petroleum hydrocarbons (TPHs) reduction, and maximum TPHs reduction (88.4%) was achieved after 60 days in the mesocosms amended with the combination of nutrients, surfactant, and aeration. Among different individual treatments, the aeration (alone) also played a pivotal role in TPHs reduction (61%). The least (12%) reduction in TPHs was achieved in the mesocosms supplied with surfactant only. This study revealed that the combined application of nutrients, surfactant, and aeration in CWs enhanced its hydrocarbons degradation performance. The biodegradability of crude oil-polluted wastewater is not efficient. It is mainly due to the low bioavailability of hydrocarbons, and less amount of nutrients and dissolved oxygen in the wastewater. This study explores the importance of the amendments of nutrients, surfactant, and aeration on the enhanced performance of constructed wetlands (CWs) for the remediation of hydrocarbon-contaminated water. The application of nutrients, surfactant, and aeration in CWs not only enhanced hydrocarbon degradation and toxicity reduction but also improved plant growth. [ABSTRACT FROM AUTHOR]

Despite growing health concerns and increasing water scarcity, adequate wastewater treatment and reuse remains limited in India. Low-cost, decentralised, and nature-based on-site sanitation systems could play a key role in a circular water approach. This paper evaluates the performance of a Wastewater Fertigated Short Rotation Coppice (wfSRC) system based on willow, poplar, and bamboo species as a potential solution, offering low-cost, efficient water treatment, and high biomass production. Through a full-scale wfSRC pilot plant (250 m3·day−1 municipal wastewater on 6864 m2) established at Aligarh Muslim University, Uttar Pradesh, India, treatment capacities, biomass production rates, and contamination tolerance of different willow, poplar, and bamboo species were investigated. The chemical compositions of incoming wastewater, percolation water, soil, and biomass were monitored regularly. Despite the high load, all plant sections of the wfSRC system showed efficient removal of wastewater-originated pollutants. BOD5 and COD removal efficiencies were up to 99% and 95% respectively. Removal efficiencies for PO4-P reached 93% and for TN 91%. In general, total nitrogen and phosphate loads appear to be the limiting design parameters under the conditions at Aligarh to meet all discharge limits in India. Biomass production was projected to be >225 tDM·ha−1·yr−1 for bamboo, 65 tDM·ha−1·yr−1 for willow, and 206 tDM·ha−1·yr−1 for poplar. The pilot, conducted from March 2022 to June 2023, showcased how these densely planted agroforestry systems can effectively treat wastewater through natural processes such as oxidation, microbial degradation, and plant uptake. The findings demonstrate wfSRC's potential to serve as a nature-based, sustainable approach to wastewater treatment, particularly beneficial for suburban and rural areas in India and similar regions worldwide. This paper also provides recommendations for future implementation of wfSRC systems, emphasizing the need for careful planning regarding plant selection, system design, and operational strategies to maximize treatment efficiency and biomass production. [ABSTRACT FROM AUTHOR]

Polyploidization and hybridization are very common in natural plant species, and mixed‐ploidy species provide a unique opportunity to study the effects of evolutionary history, local abundance, and ploidy level on the direction and extent of introgression between intraspecific lineages. First, we delimited two morphologically cryptic lineages of Phragmites australis Trin. ex Steud. in temperate China using 11 nuclear microsatellites and two chloroplast DNA fragments with 225 samples from China as well as 11 samples from Oceania and Europe. Our evidence supported that haplotype O and haplotype P were two relatively independent lineages with low and high ploidy levels, respectively; haplotype M might be ancient and could have undergone a complex evolutionary history. Then we examined the lineage divergence and compared the introgression patterns between two major lineages along geographical and abundance gradients with a large number of samples (n = 1067) collected from China. The sympatric coexistence of two lineages in north and northeast China implies an ongoing or potential introgression between them. Cline analysis showed that the level of genetic admixture were significantly correlated with longitude rather than latitude. Our results also suggested that ploidy level could deeply influence the introgression asymmetry, and the effect of the current local abundance on introgression might be covered by the past coexistence time driven by phylogeographic history. Our study draws a baseline for future research on the ecological and evolutionary consequences of migration and introgression of Chinese P. australis under global change. [ABSTRACT FROM AUTHOR]

Abstract: The knowledge on the performance enhancement of nitrogen and organic matter in the expanded constructed wetlands (CWs) with various new designs, configurations, and technology combinations are still not sufficiently summarized. A comprehensive review is accordingly necessary for better understanding of this state-of-the-art-technology for optimum design and new ideas. Considering that the prevailing redox conditions in CWs have a strong effect on removal mechanisms and highly depend on wetland designs and operations, this paper reviews different operation strategies (recirculation, aeration, tidal operation, flow direction reciprocation, and earthworm integration), innovative designs, and configurations (circular-flow corridor wetlands, towery hybrid CWs, baffled subsurface CWs) for the intensifications of the performance. Some new combinations of CWs with technologies in other field for wastewater treatment, such as microbial fuel cell, are also discussed. To improve biofilm development, the selection and utilization of some specific substrates are summarized. Finally, we review the advances in electron donor supply to enhance low C/N wastewater treatment and in thermal insulation against low temperature to maintain CWs running in the cold areas. This paper aims to provide and inspire some new ideas in the development of intensified CWs mainly for the removal of nitrogen and organic matter. The stability and sustainability of these technologies should be further qualified. [Copyright &y& Elsevier]

The importance of temperature responses of photosynthesis and respiration in determining species distributions was compared in two closely related freshwater macrophytes, Ceratophyllum demersum and C. submersum. The two species differed significantly in response to temperature in the short and long term, despite being collected in the same geographical region, near Aarhus, Denmark., The distribution of C. submersum is narrower globally and does not extend as far north as C. demersum, which is a cosmopolitan species. Results from short-term (within minutes) temperature-response curves and distributional patterns corresponded well with the long-term (weeks) results obtained, but with some important deviations. The long-term responses of the two species to low temperature (12 °C) were more similar than expected. In contrast, high temperature (35 °C), which stimulated photosynthesis in C. submersum in the short term, inhibited photosynthesis in the long term and resulted in lower growth rates of C. submersum, both compared to C. demersum and to growth rates at intermediate temperatures (18 and 25 °C)., The long-term acclimation strategy differed between the two species. Ceratophyllum demersum achieved homeostasis in photosynthesis and respiration rates, and the temperature optimum for photosynthesis changed according to its acclimation temperature. In contrast, C. submersum had a homeostatic response to the ratio of dark respiration to gross photosynthetic capacity and did not change its temperature optimum. Hence, this study highlights key issues that need to be examined carefully to improve models predicting future temperature responses of aquatic plants. [ABSTRACT FROM AUTHOR]

Enhanced sequestration of carbon in ocean sediments is a promising approach to mitigate the adverse effects of climate warming. To assess the capacity of coastal regions to uptake and bury carbon, a wetland restoration project was carried out in the degraded coastal wetlands of the Liaohe Delta between 2011 and 2013. A 13.33-ha degraded salt marsh was selected to create two enhanced carbon sink experimental areas, one dominated by Phragmites australis and the other dominated by Suaeda salsa. Improvements to the wetland matrix, hydrological processes, and vegetation colonization were designed and constructed. Results revealed that after the three-year restoration effort, the biomass of vegetation in the demonstration area was 1.2–4.0 times that of a natural wetland, and the rate of organic carbon sequestration in the sediments was about 60–80% of the rate in a natural salt marsh. We show that restoring vegetation can significantly increase the rate of sedimentation and thus enhance the carbon sequestration capacity of a wetland dominated by S. salsa or P. australis. Carbon sequestration capacity can be restored more rapidly in salt marsh wetlands than in mangrove wetlands, and we argue that restoration of salt marsh wetlands is an urgent task suitable for the application of large-scale ocean carbon sequestration technologies. • A case study on a novel technology for ocean negative ocean emissions was detailed. • Soil organic carbon sequestration rates of restored wetlands were about 60–80% of the rates in natural wetlands after three years. • Restoring vegetation can significantly increase the rate of sedimentation and thus enhance the carbon sequestration in the soils. [ABSTRACT FROM AUTHOR]

[Display omitted] • EWS-pyrochars are a ready-to-integrate opportunity for soil amendment. • Novel 3D-images reveal the char's porosity, structure, thickness-mesh, and Feret-diameter. • High aromaticity: overall sp2 C-atoms at 63 % in pyrochar vs. 43 % in hydrochars. • High P-retention: 92 % in EWS-pyrochars, near-total in hydrochars. • Hydrochars from a 10-hectare willow may sequester 80-tons of carbon and recover 334 kg of P annually. Willows from engineered wetland systems (EWS) offer a sustainable approach to wastewater treatment and biomass production. Our study assesses their potential for nutrient recovery and carbon sequestration using slow pyrolysis (600 °C) and hydrothermal carbonization (250 °C). Here, we propose EWS-pyrochars as a ready-to integrate opportunity for soil amendment, as they exhibit a predominant CO 2 release and the absence of harmful compounds in pyrolysis-chromatograms, indicating higher stability than hydrochars. Using sequential P-extractions, we observed a high bioavailability in the willow-woodchips and a significant P-retention in EWS-chars—up to 92 % in pyrochars and near-complete retention in hydrochars, along with a higher labile-P fraction of 21 % in hydrochars than 5 % in pyrochars. Utilizing X-ray-based techniques, Raman spectroscopy, scanning electron microscopy, and gas physisorption, we characterized the EWS-chars' structures. We revealed innovative 3D-visualizations, which transcend previous literature by providing insights into the chars' internal porosity and quantifying, for the first time, their carbonaceous structural thickness via a meshing algorithm and the mean Feret diameter. EWS-pyrochars exhibit remarkable aromaticity with a higher concentration of overall sp2 C-atoms at 63 % vs. 43 % in hydrochars. Moreover, unlike hydrochars, which depict occluded porosity, EWS-pyrochars exhibited 92 % water storage-like pores. Although hydrochars indicated lower carbonization and thermal stability than pyrochars, their higher carbon retention (55 vs. 41 % in pyrochar) suggest superior annual benefits—on a 10 ha EWS scale—of 80-tons of carbon sequestration and 334 kg of phosphorus recovery versus 60-tons of carbon and 298 kg of phosphorus with pyrochars. Our findings suggest innovative materials for resource recovery, advancing the engineered wetland systems field, shifting their traditional use, and opening the opportunity for future integration into biorefineries. [ABSTRACT FROM AUTHOR]

Engineered wetland systems (EWS) are globally recognized as efficient wastewater treatment solutions with the potential for sustainable biomass production. The need arises to understand hydrothermal carbonization's (HTC) potential in nutrient and resource recovery from this biomass. While willows are well-studied in bioenergy, their utility in HTC remains understudied. We investigated the unexplored HTC of EWS-sourced willows. Here, we demonstrate that combining the robust biomass yield of a zero-discharge willow system—56 t DM⋅ha−1 over a three-year rotation—with HTC yields hydrochars, enabling phosphorus recovery (13–52 kg P⋅ha−1) and carbon sequestration (9–17 t C⋅ha−1). In a broader perspective, 10-ha willow systems can sequester about 117-tons of carbon annually, with hydrochars contributing 90-tons and an additional 27-tons attributed to the root system. Moreover, recirculating HTC-process water through hydrochar can increase the recovery to about 130–280-kg of phosphorus annually. We noted HTC-reactivity variations between a natural Salix variant and a wastewater-optimized clone. We used custom-engineered reactors and a two-factor experimental design that varied the HTC temperatures (225, 250, 275, and 300 °C) and reaction times (10, 20, 30, and 60 min), maintaining a 1:10 dry biomass-to-water mass ratio and heating rate at ∼59 °C⋅min−1. Hydrochars show improved fuel properties and energy content—Higher heating value of 22–28 MJ⋅kg−1, aligning closely with mineral coals. These hydrochars also showcased enhanced thermal stability, heightened aromaticity, and increased fixed carbon content (14–45 %). Remarkably, phosphorus densification in hydrochars reached up to 100 % during HTC reactions. Chemical P-extractions indicated a high P-bioavailability in the willow-woodchips and a low potential for phosphorus leaching in hydrochars, with 87 % of total-P extractable using HCL. Our findings offer a preliminary framework for bridging EWS in the domains of hydrothermal processes as an opportunity for future integration in biorefineries. [Display omitted] •Engineered wetland yield up to 31 t DM⋅ha−1⋅a−1 of biomass and efficiently treat wastewater. •TGA suggests hydrochars from a 10-ha willow may sequester 90 t C⋅a−1, with ≥10 % expected error. •High aromaticity and up to 45 % fixed carbon in willow hydrochars. •Remarkable phosphorus densification with near-complete phosphorus retention in willow hydrochars. [ABSTRACT FROM AUTHOR]

Abstract: The effects of inorganic nitrogen (N) nutrition (NH4 +, NO3 − or both) at equimolar (0.5mM) concentration on growth, biomass allocation, mineral element concentration, N-uptake kinetics and nitrate reductase activity were assessed in hydroponically grown Cyperus laevigatus and Phormium tenax. Both species grew well with both NH4 + and NO3 − as the sole N source, but the mean growth rate of C. laevigatus (RGR=0.12d−1) was significantly higher than that of P. tenax (RGR=0.02d−1). However, the RGR of C. laevigatus was higher when supplied with NH4 +, either alone or in combination with NO3 −, than when supplied with NO3 − alone, whereas the RGR of P. tenax was indifferent to nitrogen source. The nitrogen uptake rate of C. laevigatus was generally higher (2–3-fold for NH4 + and 4–14-fold for NO3 −) than that of P. tenax in concert with its higher growth rate. Both species had higher uptake capacity and higher affinity for NH4 + than for NO3 −. The mean maximum uptake velocity (V max) for NH4 + was 99 and 41μmolg−1 root DM h−1 for C. laevigatus and P. tenax, respectively, as opposed to a V max for NO3 − of 24 and 3.4μmolg−1 root DM h−1 for C. laevigatus and P. tenax, respectively. P. tenax had significantly lower affinities for both NH4 + and NO3 − than C. laevigatus indicating that P. tenax are adapted to sites with relatively high N availability, as opposed to C. laevigatus, which via its high-affinity uptake systems can grow at sites with lower N availability. Both shoots and roots of both species had nitrate reductase activity, particularly when plants were fed with NO3 −. P. tenax seemed to be more sensitive to NH4 + nutrition than C. laevigatus since tissue concentrations of mineral elements were lower in roots of plants supplied with NH4 +. Our results suggest that the indifference to N nutrition provides C. laevigatus and P. tenax with the ability to grow well in periodically inundated areas with fluctuating and variable N sources. However, C. laevigatus may be better adapted than P. tenax to grow in permanently inundated soils with high NH4 + concentrations, whereas P. tenax may be better adapted to grow at high NO3 − condition. [Copyright &y& Elsevier]

Aerenchymatous plants can transport methane ( CH4) from the root zone to the atmosphere, bypassing the surface-oxidizing layers of the soil, yet morphological and anatomical factors that govern the transport of methane have rarely been critically tested in manipulative experiments., Here, we investigated the methane transport capacity of hydroponically grown Juncus effusus, in experiments with roots submerged in nutrient solutions sparged with methane (1.16 mmol CH4 l−1). Through a range of manipulations of the above- and below-ground plant parts, we tested the contradictory claims in the literature regarding which sites provide the greatest resistance to gas transport., Root manipulations had the greatest effect on methane transport. Removing root material reduced methane transport significantly, and especially the lateral roots and the root tips were important. Cutting of the shoots, with or without subsequent sealing, did not alter methane transport significantly., We confirm modelling predictions that the limiting factor for methane transport in the tussock forming wetland graminoid, J. effusus, is the amount of permeable root surface, estimated using the proxy measurement of root length. The aerial tissues do not provide any significant resistance to methane transport, and the methane is emitted from the lower 50 mm of the shoots. [ABSTRACT FROM AUTHOR]

• Internal pressurization and convective gas flow, which can aerate wetland plants more efficiently than diffusion, are common in temperate species. Here, we present the first survey of convective flow in a range of tropical plants. • The occurrence of pressurization and convective flow was determined in 20 common wetland plants from the Mekong Delta in Vietnam. The diel variation in pressurization in culms and the convective flow and gas composition from stubbles were examined for Eleocharis dulcis, Phragmites vallatoria and Hymenachne acutigluma, and related to light, humidity and air temperature. • Nine of the 20 species studied were able to build up a static pressure of > 50 Pa, and eight species had convective flow rates higher than 1 ml min)1. There was a clear diel variation, with higher pressures and flows during the day than during the night, when pressures and flows were close to zero. • It is concluded that convective flow through shoots and rhizomes is a common mechanism for below-ground aeration of tropical wetland plants and that plants with convective flow might have a competitive advantage for growth in deep water. [ABSTRACT FROM AUTHOR]

Abstract: Common practice of aquaculture in Vietnam and other countries in South East Asia involves frequent discharge of polluted water into rivers which results in eutrophication and degradation of receiving water bodies. There is therefore a need to develop improved aquaculture systems which have a more efficient use of water and less environmental impact. The aim of this study was to assess the suitability of using constructed wetlands (CWs) for the treatment of fishpond water in a recirculating aquaculture system in the Mekong Delta of Vietnam. Water from a fishpond stocked with Nile tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio) was recirculated through horizontal and vertical flow CWs. The CWs were able to keep a good water quality with DO (>1mg/l−1), BOD (<30mg l−1), TAN (<1mg l−1) and NO2 − (<0.07mg l−1) at acceptable concentrations for growth of the fish. There was a good removal of organic matter measured as oxygen demand with up to 50% removal of BOD and COD in both types of CWs despite the high loading rates and low concentration levels. However, the vertical flow CWs performed better than the horizontal flow CWs as they had higher nitrification rates and higher DO concentrations in the outlets. The ornamental Canna × generalis planted in the CWs grew faster and took up more N and P in the vertical flow CWs. The aquaculture fish had a feed conversion ratio of 1.53 based on feed dry weight, and 31% and 34% of N and P input, respectively, were incorporated into fish biomass. Only minor quantities of phytoplankton algae were removed in the CWs but abundance of toxic algae such as Microcystis was low. It is concluded that particularly vertical flow CWs have great potential for treatment of fishpond water in recirculating aquaculture systems in the tropics as the discharge of polluted water and the associated environmental impact can be significantly reduced. [Copyright &y& Elsevier]

Abstract: Application of low doses of alum to treatment wetlands to reduce elevated outflow winter phosphorus concentrations were tested in mesocosms vegetated with either Typha domingensis, Schoenoplectus californicus, or submerged aquatic vegetation (SAV) (Najas guadalupensis-dominated). Alum was pumped to experimental units at a rate of 0.91g Alm−2 d−1 and water quality monitored for 3months. The alum application significantly improved the outflow water quality and overall the growth of the plants was unaffected by the alum application. Biomass and growth varied between species and through time, but no significant effects of alum application were detected. The concentrations of nutrients and mineral elements in the aboveground tissues differed between species and over time, but only the concentration of Al in plant tissue was increased by alum additions. The concentration of Al was 50-fold higher in alum-treated SAV as compared to the control, and in Typha and Schoenoplectus the concentrations were 4- and 2-fold, higher, respectively. The N/P ratios in the plant tissues were low (<10) suggesting that their growth and biomass was limited by nitrogen. The research suggests that a continuous or seasonal low-dosage alum application to treatment wetlands provides an effective tool to maintain discharge concentrations within permitted values during the inefficient winter treatment times. We suggest that the use of alum should be restricted to treatment wetland areas dominated by emergent vegetation as the effects of the elevated Al concentrations in SAV needs further study. [Copyright &y& Elsevier]