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The influence of different environmental stresses, including salinity (5-35‰), tidal cycle (6/6, 12/12 and 24/24 h of high/low tidal regimes) and nutrient addition (1-6 times background nitrogen and phosphorus content) on Bruguiera gymnorrhiza and Aegiceras corniculatum grown in sediment contaminated with spent lubricating oil (7.5 L m(-2)) were investigated. The oil-treated 1-year-old mangrove seedlings subject to low (5‰) and high (35‰) salinity had significantly more reduction in growth, more release of superoxide radical (O2·-) and higher activity of superoxide dismutase (SOD) than those subject to moderate salinity (15‰). Extended flooding (24/24 h of high/low tidal regime) enhanced O2·- release and malondialdehyde (MDA) content in both oil-treated species but had little negative effects on biomass production (P>0.05) except the stem of A. corniculatum (P=0.012). The addition of nutrients had no beneficial or even posed harmful effects on the growth and cellular responses of the oil-treated seedlings., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The growth of four mangrove species seedlings, namely Bruguiera gymnorrhiza, Kandelia obovata, Aegiceras corniculatum and Acanthus ilicifolius in sediments contaminated by spent lubricating oil, even at the lowest oil dose (2.5 L m(-2)), showed different degrees of sub-lethal damages. All the seedlings of K. obovata and A. corniculatum were killed at 10 L m(-2) oil, while the lethal oil dose was 15 L m(-2) for A. ilicifolius seedlings. B. gymnorrhiza was the most tolerant species to oil pollution, which could survive under the highest oil dose treatment (15 L m(-2)). Biochemical responses including superoxide radical (O(2)(-)) release, superoxide dismutase (SOD) activity and malonyldialdehyde (MDA) content in both leaves and roots of the oil-treated seedlings were increased significantly with oil dose, and presented a positive relationship with leaf and root biomass., (Copyright © 2010 Elsevier Inc. All rights reserved.)

One new dimeric diterpenoid, 8(14)-enyl-pimar-2'(3')-en-4'(18')-en-15'(16')-endolabr- 16,15,2',3'-oxoan-16-one (1) and five known terpenoids: Tagalsin C (2), Tagalsin I (3), lup-20(29)-ene-3β,28-diol (4), 3-oxolup-20(29)-en-28-oic acid (5) and 28-hydroxylup- 20(29)-en-3-one (6) were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative stereochemistry were elucidated by means of extensive NMR, IR and MS analysis. The antifouling activity against larval settlement of the barnacle Balanus albicostatus were evaluated using capsaicin as a positive control. All these terpenoids exhibited antifouling activity against cyprid larvae of the barnacle without significant toxicity. The structure-activity relationship results demonstrated that the order of antifouling activity was diterpenoid (Compound 2) > triterpenoid (Compounds 4, 5 and 6) > dimeric diterpenoid (Compounds 1 and 3). The functional groups on the C-28 position of lupane triterpenoid significantly affect the antifouling activity. The diterpenoid dimmer with two identical diterpenoid subunits might display more potent antifouling activity than one with two different diterpenoid subunits. The stability test showed that Compounds 2, 4, 5 and 6 remained stable over 2-month exposure under filtered seawater.

The temporal responses of peroxidase (POD), superoxide dismutase (SOD), total polyphenols (TP), extractable condensed tannins (ECT) to different levels of lead (Pb) or manganese (Mn) stress, as well as the metal accumulation, in seedlings of Kandelia obovata were investigated. Both stress time and stress intensity had significant effects with significant accumulation of Pb and Mn in roots at Day 1. Pb and Mn showed no significant effects on root or leaf TP and ECT at Day 1. Prolonged exposure to metals caused significant drops of root TP and ECT but increased in leaves at Days 7 and 49. POD activities decreased in both roots and leaves at Day 1, while POD and SOD both increased under moderate levels of Pb and Mn at Day 7. The present study showed that antioxidative enzyme activities were more sensitive indicators to Pb or Mn stresses than phenolic compounds., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Iron (Fe) plaque formed on mangrove root increased with wastewater discharge, but the extent was species-specific. For Bruguiera gymnorrhiza, Fe plaque concentration was 0.80 mg g(-1) root d.wt at Day 0 and increased to 4.59, 6.84 and 7.52 mg g(-1) at Day 75 in the fresh water control (FW), synthetic wastewater with pollutant concentrations five times of municipal sewage (5SW) and double of 5SW (10SW) treatments, respectively; the respective increases in Excoecaria agallocha were from 0.70 to 2.37, 10.73 and 13.21 mg g(-1). For Acanthus ilicifolius, similar increase was found in 5SW, but all of the plants were dead in 10SW at Day 75. The concentrations of heavy metals and phosphorus immobilized were positively correlated with the amounts of Fe plaque formed, but the regression coefficients varied among species. The performance of mangrove plants in wastewater treatments was related to the Fe plaque formed and its immobilized wastewater-borne pollutants., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Estuaries are important sites for mercury (Hg) methylation, with sulfate-reducing bacteria (SRB) thought to be the main Hg methylators. Distributions of total mercury (THg) and methylmercury (MeHg) in mangrove sediment and sediment core from Jiulong River Estuary Provincial Mangrove Reserve, China were determined and the possible mechanisms of Hg methylation and their controlling factors in mangrove sediments were investigated. Microbiological and geochemical parameters were also determined. Results showed that SRB constitute a small fraction of total bacteria (TB) in both surface sediments and the profile of sediments. The content of THg, MeHg, TB, and SRB were (350 +/- 150) ng/g, (0.47 +/- 0.11) ng/g, (1.4 x10(11) +/- 4.1 x 10(9)) cfu/g dry weight (dw), and (5.0 x 10(6) +/- 2.7 x 10(6)) cfu/g dw in surficial sediments, respectively, and (240 +/- 24) ng/g, (0.30 +/- 0.15) ng/g, (1.9 x 10(11) +/- 4.2 x 10(10)) cfu/g dw, and (1.3 x 10(6) +/- 2.0 x 10(6)) cfu/g dw in sediment core, respectively. Results showed that THg, MeHg, TB, MeHg/THg, salinity and total sulfur (TS) increased with depth, but total organic matter (TOM), SRB, and pH decreased with depth. Concentrations of MeHg in sediments showed significant positive correlation with THg, salinity, TS, and MeHg/THg, and significant negative correlation with SRB, TOM, and pH. It was concluded that other microbes, rather than SRB, may also act as main Hg methylators in mangrove sediments.

A fiber-optic fluorimetry for in situ simultaneous determination of fluorine (Flu), phenanthrene (Phe) and fluoranthene (Fla) adsorbed on the leaf surfaces of Kandelia candel (Kc) seedlings was developed. Experimental results showed that the linear ranges for determination of Flu, Phe and Fla adsorbed on Kc leaves were 35-700, 5-900 and 2-450 ng/spot, respectively. The detection limits for Flu, Phe and Fla were 9.11, 1.65 and 0.90 ng/spot and with the relative standard deviations less than 10.32%, 7.56% and 4.29% (n=9), respectively. The recovery results for Flu, Phe and Fla adsorbed on Kc leaves were 83.0-91.2, 78.5-88.5 and 91.5-107.3%, respectively. Under the laboratory experimental conditions, the photolysis processes of Flu, Phe and Fla individual and in mixtures adsorbed on the leaf surfaces of living Kc seedlings were studied. Results showed that the photolysis of Flu, Phe and Fla individual and in mixtures adsorbed on the leaf surfaces of Kc seedlings followed first-order kinetics with photolysis rates in the order of Flu>Fla>Phe on the Kc leaves. An antagonistic effect was found when the three polycyclic aromatic hydrocarbons (PAHs) were co-adsorbed on living Kc seedlings. The experimental results also indicated that photolysis was the main transformation pathway for Flu, Phe and Fla both individual and in mixtures adsorbed on Kc leaves, whereas disappearance of the adsorbed Flu, Phe and Fla as a result of volatilization and leaf absorption could be negligible during the experimental period., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In this study, we investigated the microbial degradation of the phthalate esters (PAEs) dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), and change in microbial communities in mangrove sediment collected from 5 sampling sites along the Tanshui River in Taiwan. Aerobic degradation half-lives (t(1/2)) of DBP and DEHP ranged from 1.6 to 2.9 d and 5.0 to 8.3d, respectively. The addition of yeast extract (5mg/L), hydrogen peroxide (1mg/L), brij 35 (91 μM), humic acid (0.5 g/L), cellulose (0.96 mg/L), and sodium chloride (1%) enhanced PAE aerobic degradation. Sediment samples were separated into fractions with various particle size ranges from 0.1-0.45 to 500-2000 μm. Sediment fractions with smaller particle sizes demonstrated higher PAE biodegradation rates. Of the microorganism strains isolated from the mangrove sediment, strains J2, J4, and J8 (all identified as Bacillus sp.) expressed the best biodegrading ability. Our results showed that Bacillus sp. was the dominant bacteria in the process of PAE aerobic degradation in the mangrove sediments., (Copyright © 2010 Elsevier B.V. All rights reserved.)

We present here the Mangrove Transcriptome Database (MTDB), an integrated, web-based platform providing transcript information from all 28 mangrove species for which information is available. Sequences are annotated, and when possible, GO clustered and assigned to KEGG pathways, making MTDB a valuable resource for approaching mangrove or other extremophile biology from the transcriptomic level. As one example outlining the potential of MTDB, we highlight the analysis of mangrove microRNA (miRNA) precursor sequences, miRNA target sites, and their conservation and divergence compared with model plants. MTDB is available at http://mangrove.illinois.edu .

Three mesocosm experiments were performed in an outdoor facility to quantify the responses of five mangrove species grown from seedling to sapling stage to increasing rates of dissolved iron supply. Stem extension and biomass of mangroves were measured in the first two experiments, and in the third experiment, rates of microbial iron reduction were measured in relation to stem extension of two mangrove species. In all experiments, mangrove growth was enhanced by increasing iron supply, although some species showed iron toxicity at the higher supply rates. In the first two experiments, stem extension rates of Rhizophora apiculata, Bruguiera gymnorrhiza, and Xylocarpus moluccensis best fit Gaussian curves with maximal growth at supply rates of 50-60 mmol Fe x m(-2) x d(-1), whereas growth of Avicennia marina and Ceriops tagal increased to the highest rate (100 mmol Fe x m(-2) x d(-1)) of iron supply. Changes in leaf chlorophyll concentrations and iron content of roots mirrored the growth responses. In the third experiment, rates of microbial iron reduction were greater with R. apiculata and A. marina than in controls without plants; for both species, there was a positive relationship between stem extension and iron reduction. The rates of iron reduction and rates of iron supplied to the plants were well within the range of interstitial iron concentrations and rates of iron reduction found in the natural mangrove soils from which the seedlings were obtained. The responses of these species show that mangroves growing from seedling to sapling stage have a strong nutritional requirement for iron, and that there is a close relationship between plant roots and the activities of iron-reducing bacteria. These results suggest that mangrove growth may be limited in some natural forests by the rate at which iron is solubilized by iron-reducing bacteria. Such biogeochemical conditions have significant implications for successful recruitment, establishment, and early growth of mangroves.

Mangrove sediment, influenced by tidal cycles, switches between low-oxygen and non-oxygen conditions, and iron is abundant in it. Polycyclic aromatic hydrocarbon (PAH) contamination often occurs in mangrove wetlands. In the present paper, the effects of iron [Fe(III)] amendment on the biodegradation of four mixed PAHs, namely fluorene (Fl), phenanthrene (Phe), fluoranthene (Flua) and pyrene (Pyr), in mangrove sediment slurries, with and without the inoculation of the enriched PAH-degrading bacterial consortia, under low-oxygen (2 + or - 0.3% O(2)) and non-oxygen (0% O(2)) conditions were investigated. Under both oxygen conditions and for all four PAHs, the highest PAHs biodegradation was observed in the groups with the inoculation of the enriched PAH-degrading consortia, while the groups without the inoculum and without Fe(III) amendment had the lowest biodegradation. However, the amendment of Fe(III) did not show any significant improvement on the biodegradation of all the four mixed PAHs., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Survival, growth, aboveground biomass accumulation, sediment surface elevation dynamics and nitrogen accumulation in sediments were studied in experimental treatments planted with four different densities (6.96, 3.26, 1.93 and 0.95 seedlings m(-2)) of the mangrove Rhizophora mucronata in Puttalam Lagoon, Sri Lanka. Measurements were taken over a period of 1,171 days and were compared with those from unplanted controls. Trees at the lowest density showed significantly reduced survival, whilst measures of individual tree growth did not differ among treatments. Rates of surface sediment accretion (means ± SE) were 13.0 (±1.3), 10.5 (±0.9), 8.4 (±0.3), 6.9 (±0.5) and 5.7 (±0.3) mm year(-1) at planting densities of 6.96, 3.26, 1.93, 0.95, and 0 (unplanted control) seedlings m(-2), respectively, showing highly significant differences among treatments. Mean (±SE) rates of surface elevation change were much lower than rates of accretion at 2.8 (±0.2), 1.6 (±0.1), 1.1 (±0.2), 0.6 (±0.2) and -0.3 (±0.1) mm year(-1) for 6.96, 3.26, 1.93, 0.95, and 0 seedlings m(-2), respectively. All planted treatments accumulated greater nitrogen concentrations in the sediment compared to the unplanted control. Sediment %N was significantly different among densities which suggests one potential causal mechanism for the facilitatory effects observed: high densities of plants potentially contribute to the accretion of greater amounts of nutrient rich sediment. While this potential process needs further research, this study demonstrated how higher densities of mangroves enhance rates of sediment accretion and surface elevation processes that may be crucial in mangrove ecosystem adaptation to sea-level rise. There was no evidence that increasing plant density evoked a trade-off with growth and survival of the planted trees. Rather, facilitatory effects enhanced survival at high densities, suggesting that managers may be able to take advantage of high plantation densities to help mitigate sea-level rise effects by encouraging positive sediment surface elevation.

Objective: To identify Aspergillus awamori strain F12 isolated from rhizospheric soil of Rhizophora stylosa Griff and to characterize antibacterial compounds from the ethyl acetate extracts of its fermentation broth., Methods: Strain F12 was identified based on its morphological characters and internal transcribed spacer (ITS) sequence. Its secondary metabolites were purified by chromatography, and elucidated by mass spectroscopy, H-NMR, 13C-NMR and physicochemical characters. The antibacterial activities of these compounds were tested against Staphyloccocus aureus and Bacillus subtilis., Results: Strain F12 was identified as Aspergillus awamori. Three compounds, including 1,4-dimethoxybenzene (1), emodin (2) and 3, 6-dibenzylpiperazine-2, 5-dione (3), were purified and elucidated from the ethyl acetate extracts of fermentation broth, among which compound 1 was first reported for the genus of Aspergillus. Compound 2 suppressed the growth of Staphyloccocus aureus and Bacillus subtilis with MIC values of 16 microg/mL and 32 microg/mL respectively, while the other two compounds have no effects on these bacteria., Conclusion: Aspergillus awamori strain F12 isolated from rhizospheric soil of Rhizophora stylosa Griff can produce 1, 4-dimethoxybenzene and emodin, among which the latter can suppress the growth of bacteria apparently.

Plant is an important role in biogeochemical cycle of Hg. The aim of this study is to ascertain Hg accumulation in several kinds of mangrove plants, and to discuss relationship among Hg concentrations in mangrove plants and different Hg speciation in sediments. Contents of total mercury (THg) in mangrove plants and sediments were determined. Hg speciation was determined with a modified Tessier's method. Contents of THg of the mangrove plants were in the range of 817.5-3 197.6 ng/g. In detail, Hg concentration was (1 579.4 +/- 1 326.8) ng/g in Kandelia candel, (2 115.1 +/- 1 892.3) ng/g in Aegiceras corniculatum, (2 159.3 +/- 1 678.7) ng/g in Avicennia marina, (2 566.5 +/- 821.6) ng/g in Bruguiera gymnorrhiza, (2 104.3 +/- 1 661.8) ng/g in Excoecaria agallocha, (3 197.6 +/- 2 782.8) ng/g in Sonneratia apetala, (817.5 +/- 632.3) ng/g in Acanthus ilicifolius, (1 801.8 +/- 1 255.4) ng/g in Rhizophora. stylosa, respectively. There are obvious interspecific variation, and organic variation in THg contents of mangrove plants, which is closely related to environment and physiological characteristics of mangrove plants. Enrichment of THg in mangrove plants was inhomogeneous, following the order of Sonneratia apetala > Bruguiera gymnorrhiza > Avicennia marina > Aegiceras corniculatum > Excoecaria agallocha > Rhizophora stylosa > Kandelia candel > Acanthus ilicifolius. Mercury exists mainly in volatile form in most mangrove wetlands, but mainly in the form of residue in sediments from Shenzhen mangrove wetlands. Significantly positive correlations were found among Hg concentrations in leaves and stems of Sonneratia apetala and volatile Hg, exchangeable Hg of sediments. Significantly positive correlations were also found among Hg concentrations in leaves of Excoecaria agallocha and volatile Hg, exchangeable Hg of sediments. But, there is no significant correlation between Hg concentrations of most mangrove plants and different Hg speciation in sediments. It showed that plants assimilate Hg from different sources, such as water, sediment and air, and that Hg assimilated by plants could transfer among different plant organics.

Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55-65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6-8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression.

Root anatomy, radial oxygen loss (ROL) and zinc (Zn) uptake and tolerance in mangrove plants were investigated using seedlings of Aegiceras corniculatum, Bruguiera gymnorrhiza and Rhizophora stylosa. The results revealed that B. gymnorrhiza, which possessed the 'tightest barrier' in ROL spatial patterns among the three species studied, took up the least Zn and showed the highest Zn tolerance. Furthermore, zinc significantly decreased the ROL of all three plants by inhibition of root permeability, which included an obvious thickening of outer cortex and significant increases of lignification in cell walls. The results of SEM X-ray microanalysis further confirmed that such an inducible, low permeability of roots was likely an adaptive strategy to metal stress by direct prevention of excessive Zn entering into the root. The present study proposes new evidence of structural adaptive strategy on metal tolerance by mangrove seedlings., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Effects of wastewater discharge on radial oxygen loss (ROL), formation of iron (Fe) plaque on root surface, and their correlations in Bruguiera gymnorrhiza (L.) Poir and Excoecaria agallocha L. were investigated. ROL along a lateral root increased more rapidly in control than that in strong wastewater (with pollutant concentrations ten times of that in municipal sewage, 10NW) treatment, but less Fe plaque was formed in control for both plants. For B. gymnorrhiza receiving 10NW, Fe plaque formation was more at basal and mature zones than at root tip, while opposite trend was shown in E. agallocha. At day 0, the correlation between ROL and Fe plaque was insignificant, but negative and positive correlations were found in 10NW and control, respectively, at day 105, suggesting that more ROL was induced leading to more Fe plaque. However, excess Fe plaque also served as a 'barrier' to prevent excessive ROL in 10NW plants., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

The metabolic fate of [carbonyl-14C]nicotinamide was surveyed in leaf disks of seven mangrove species, Bruguiera gymnorrhiza, Rhizophora stylosa, Kandeliaobovata, Sonneratia alba, Pemphis acidula, Lumnitzera racemosa and Avicennia marina, with and without 250 mM NaCl. Uptake of [14C]nicotinamide by leaf disks was stimulated by 250 mM NaCl in K. candel, R. stylosa, A. marina and L. racemosa. [Carbonyl-14C]nicotinamide was converted to nicotinic acid and was utilised for the synthesis of nucleotides and nicotinic acid conjugates. Formation of nicotinic acid by the deaminase reaction was rapid; there was little accumulation of nicotinamide in the disks 3h after administration. Radioactivity from [carbonyl-14C]nicotinamide was incorporated into pyridine nucleotides (mainly NAD and NADP) in all mangrove leaves, and the rates varied from 2% (in L. racemosa) to 15% (S. alba) of the total radioactivity taken up. NaCl generally reduced nicotinic acid salvage for NAD and NADP. In all mangrove leaf disks, the most heavily labelled compounds (up to 70% of total radioactivity) were trigonelline (N-methylnicotinic acid) and/or nicotinic acid N-glucoside. Trigonelline was formed in all mangrove plants, but N-glucoside synthesis was found only in leaves of A. marina and K. obovata. In A. marina, incorporation of radioactivity into N-glucoside (51%) was much greater than incorporation into trigonelline (2%). In general, NaCl stimulates the synthesis of these pyridine conjugates. The rate of decarboxylation of nicotinic acid in roots of A. marina seedlings was much greater than for the corresponding reaction observed in leaves., (2009 Elsevier Ltd. All rights reserved.)

The effects of a mixture of heavy metals (Pb, Zn and Cu) on growth, radial oxygen loss (ROL) and the spatial pattern of ROL were investigated in mangrove seedlings of three species: Aegiceras corniculatum, Avicennia marina and Bruguiera gymnorrhiza. Heavy metals inhibited the growth of seedlings and led to decreased ROL and changes in the "tight" barrier spatial pattern of ROL. There was a significant positive correlation between the amount of ROL from the roots of seedlings and metal tolerance. The species with the highest ROL amount, B. gymnorrhiza, were also the most tolerant to heavy metals. The "tight" barrier spatial ROL pattern was also related to metal tolerance in the seedlings. Therefore, we conclude that both ROL amount and "tight" barrier spatial ROL pattern in the roots of the mangrove seedlings play an important role in resistance to heavy metal toxicity.

The study aimed at investigating the effects of sewage loadings on the behaviour of two fiddler crabs species maintained in a system of experimental mesocosms, built in a mangrove area in Tanzania and inundated with different seawater/sewage mixtures. Our results show that sewage loads led to a modification of the overall activity budget of the crab community as a result of increased hypertrophic conditions (high COD, increased chlorophyll-a concentrations). During their activity period, crabs inside contaminated mesocosms seemed to satisfy their feeding demand faster than those of the control cells, spending a significant longer time in other activities like courtship and territorial defence. Apart from being a good biological indication of ecosystem eutrophication, such a reduced foraging activity by fiddler crabs also depresses their sediment bioturbation activity, important factor for the health of mangrove systems, suggesting practical implications regarding the efficiency of mangrove-based wetlands for treatment of domestic sewage.

The halophytic Kandelia candel and Bruguiera gymnorrhiza are ideal model for studying the molecular mechanisms of salinity tolerance in mangrove plants. The correlation between mRNA expression of four oxidosqualene cyclase (OSC) genes namely, KcMS multifunctional terpenoid synthase and KcCAS cyloartenol synthase (K. candel), BgbAS beta-amyrin synthase and BgLUS lupeol synthase (B. gymnorrhiza) and salt concentration was examined. mRNA level of KcMS was increased with salt concentration in both roots and leaves of K. candel. Similarly, salt stress increased the mRNA levels of BgLUS and BgbAS in the root of B. gymnorrhiza. This result suggests that the function of terpenoids in root is associated with the salt stress. In contrast to these observations, the mRNA level of KcCAS was not modulated by salt stress in the roots, and decreased in the leaves. These results therefore suggest that the terpenoids but not phytosterols play an important role to cope with the salt stress in mangrove root. The content and proportion of beta-amyrin and lupeol increased with salinity in the root of K. candel and B. gymnorrhiza, providing additional evidence for the protective role of terpenoids. However, beta-amyrin and lupeol in B. gymnorrhiza leaves decreased with salt concentration, suggesting that the physiological significance for the terpenoids in the leaf may differ from that for the root.

In this paper, we aimed to assess the roles of metallothioneins (MTs) in heavy metal tolerance by analyzing the expression level of BgMT2 in leaves of Bruguiera gymnorrhiza in response to heavy metals. Eight-month-old B. gymnorrhiza seedlings were exposed to different concentrations of zinc (Zn), copper (Cu) or lead (Pb) for 1, 3 and 7 d. A Real-time quantitative PCR protocol was developed to directly evaluate the expression of BgMT2, using 18S rRNA as a reference gene. Real-time quantitative PCR analysis demonstrated BgMT2 mRNA expression was regulated by Zn, Cu and Pb, but the regulation pattern was different for the three metals tested. Significant increase in the transcript level of BgMT2 was also found in response to Zn, Cu and Pb in some experimental conditions. Our results confirm that BgMT2 gene is involved in the regulation of Zn, Cu and Pb in B. gymnorrhiza leaves.

The accumulative partitioning of Pb and Cu in the Rhizophora apiculata was studied randomly in the Setiu mangrove forest, Terengganu. Samples of leaves, barks and roots were collected randomly from the selected studied species. Sediments between the roots of the sampled mangrove plants were also collected. The results from analysis for Rhizophora apiculata shows that the concentration of Pb and Cu were accumulated higher in root tissue compared to bark and leaf tissue but lower than surrounding sediment level. The average concentration of Cu for Rhizophora apiculata in leaf, bark, root and sediment was 2.73, 3.94, 5.21 and 9.42 mg I(-1), respectively. Meanwhile, the average concentration of Pb in leaf, bark, root and sediment was 1.43, 1.38, 2.05 and 11.66 mg l(-1), respectively. Results of concentration factors (CF) show that the overall the concentration of Pb and Cu were accumulated much higher in roots system of Rhizophora apiculata.

Rhizophora mangle L. trees of Biscayne National Park (Florida, USA) have two distinct growth forms: tall trees (5-10 m) growing along the coast and dwarf trees (1 m or less) growing in the adjacent inland zone. Sharp decreases in salinity and thus increases in soil water potential from surface soil to about a depth of 1 m were found at the dwarf mangrove site but not at the tall mangrove site. Consistent with our prediction, hydraulic redistribution detected by reverse sap flow in shallow prop roots was observed during nighttime, early morning and late afternoon in dwarf trees, but not in tall trees. In addition, hydraulic redistribution was observed throughout the 24-h period during a low temperature spell. Dwarf trees had significantly lower sapwood-specific hydraulic conductivity, smaller stem vessel diameter, lower leaf area to sapwood area ratio (LA/SA), smaller leaf size and higher leaf mass per area. Leaves of dwarf trees had lower CO(2) assimilation rate and lower stomatal conductance compared to tall trees. Leaf water potentials at midday were more negative in tall trees that are consistent with their substantially higher stomatal conductance and LA/SA. The substantially lower water transport efficiency and the more conservative water use of dwarf trees may be due to a combination of factors such as high salinity in the surface soil, particularly during dry periods, and substantial reverse sap flow in shallow roots that make upper soil layers with high salinity a competing sink of water to the transpiring leaves. There may also be a benefit for the dwarf trees in having hydraulic redistribution because the reverse flow and the release of water to upper soil layers should lead to dilution of the high salinity in the rhizosphere and thus relieve its potential harm to dwarf R. mangle trees.

To identify key proteins in the regulation of salt tolerance in the mangrove plant Bruguiera gymnorhiza, proteome analysis of samples grown under conditions of salt stress was performed. Comparative two-dimensional electrophoresis revealed that two, three and one protein were differentially expressed in the main root, lateral root and leaf, respectively, in response to salt stress. Among these, three proteins were identified by internal peptide sequence analysis: fructose-1,6-bisphosphate (FBP) aldolase and a novel protein in the main root, and osmotin in the lateral root. These results suggest that FBP aldolase and osmotin play roles in salt tolerance mechanisms common to both glycophytes and mangrove plants. Osmotin was abundant at early time points following salt treatment and seems to play a role in initial osmotic adaptation in lateral roots of B. gymnorhiza under salt stress, but does not contribute towards adaptation to prolonged or continuous exposure to salt stress. The amounts of these proteins were not correlated with those of the respective mRNAs, as determined by microarray analysis. A novel salt-responsive protein, not previously detected by expressed sequence tag analysis or transcriptome analysis, was also identified in this proteomic approach, and may provide insight into the salt tolerance mechanism of the mangrove plant. This is the first report of proteome analysis with detailed analysis of main and lateral roots of mangrove plants under salt stress conditions.

This paper presents data on the bioconcentration of heavy metals found in 10 plant species that occur in mangroves and inland ecosystems of India. The average concentration of mercury in the mangrove plants (0.068 microg g(-1)) was 11.3 times that of the inland plants (0.006 microg g(-1); p<0.05). The average concentration of lead in the mangrove plants (19.23 microg g(-1)) was 1.7 times that of the inland plants (11.38 microg g(-1); p<0.05). The mean bioconcentration factors for lead in mangrove plants (2.40 +/- 0.75) were higher than that the inland plants (1.42 +/- 0.15). The factor analysis accounted for 21.55% of the total variance showed accumulation of mercury and lead confirming the polluted nature.

Based on the investigation of biomass and the measurement of CO2 and CH4 fluxes, the CO2 exchanges between mangrove- and shoal wetland ecosystems and atmosphere in Guangzhou were studied, and the CO2 absorption capability of the wetlands vegetation net productivity as well as the carbon sink function of the wetlands under different waterlogged conditions (perennial, intermittent, and no water-logging) was analyzed. As for mangrove wetland ecosystem, its vegetation net productivity absorbed 33.74 t x hm(-2) x a(-1) of CO2, and soil emitted 12.26 t x hm(-2) x a(-1) of CO2 (including the greenhouse effect amount of CH4 converted into that of CO2,) illustrating that mangrove wetland had a 21.48 t x hm(-2) x a(-1) net absorption of CO2, being a strong carbon sink. For shoal wetland ecosystem, its vegetation net productivity absorbed 8.54 t x hm(-2) x a(-1) of CO2, and soil emitted 5.88 t x hm(-2) x a(-1) of CO2 and 0.19 t x hm(-2) x a(-1) of CH4. If converting into carbon, the wetland absorbed 2.33 t C x hm(-2) x a(-1), and soil emitted 1.74 t C x hm(-2) x a(-1) (including the carbon in CH4), illustrating that shoal wetland fixed 0.59 t C x hm(-2) x a(-1), being a weak carbon sink. If the greenhouse effect amount of CH4 was converted into that of CO2, the soil emitted 9.78 t x hm(-2) x a(-1) of CO2, which was 1.24 t x hm(-2) x a(-1) more than the absorption. As a result, shoal wetland was a weak carbon source. Between the two test greenhouse gases, CH4 was the main one emitted under perennial water-logging, while CO2 was that under no water-logging. Moreover, the wetland under perennial water-logging had the strongest carbon sink function, while that under no water-logging was in adverse.

The speciation distribution of cadmium (Cd) in mangrove (Kandelia candel (L.) Druce) rhizosphere sediment was investigated after different contents of Cd being loaded. The study results indicated that root induced changes of Cd bioavailability in the rhizosphere. Exchangeable and carbonate bound Cd in the rhizosphere sediments were lower than these in the bulk sediments, whilst an increase in Fe-Mn oxides bound and O.M/sulfide bound fractions occurred in the rhizosphere sediment. Increased levels of Cd in sediments resulted in higher Cd concentrations in mangrove plants, and the order of accumulation was: roots > hypocotyls > stems and leaves.

Two hypotheses have been proposed to explain increases in plant nitrogen (N) and phosphorus (P) concentrations with latitude: (i) geochemical limitation to P availability in the tropics and (ii) temperature driven variation in growth rate, where greater growth rates (requiring greater nutrient levels) are needed to complete growth and reproduction within shorter growing seasons in temperate than tropical climates. These two hypotheses were assessed in one forest type, intertidal mangroves, using fertilized plots at sites between latitudes 36 masculine S and 27 masculine N. The N and P concentrations in mangrove leaf tissue increased with latitude, but there were no trends in N : P ratios. Growth rates of trees, adjusted for average minimum temperature showed a significant increase with latitude supporting the Growth Rate Hypothesis. However, support for the Geochemical Hypothesis was also strong; both photosynthetic P use efficiency and nutrient resorption efficiency decreased with increasing latitude, indicating that P was less limiting to metabolism at the higher latitudes. Our study supports the hypothesis that historically low P availability in the tropics has been an important selective pressure shaping the evolution of plant traits.

The carbon (C) concentration and flux, as dissolved organic carbon (DOC), particulate organic carbon (POC) and macrodetritus (MD), were quantified through 4 tidal cycles in a mangrove tidal creek in Southeastern Brazil. DOC was the major fraction of the total C concentration, accounting for 68 and 61% of the total C concentration during ebb and flood periods respectively. Concentrations of DOC (Ebb = 3.41 +/- 0.57 mgC.L-1 and Flood = 3.55 +/- 0.76 mgC.L-1) and POC (Ebb = 1.73 +/- 0.99 mgC.L-1 and Flood = 1.28 +/- 0.45 mgC.L-1) were relatively similar during the four tidal cycles. Macrodetritus presented a wide variation with concentration peaks probably related to external forces, such as winds, which enrich the ebb flow with leaf litter. DOC and POC fluxes depended primarily on tidal and net water fluxes, whereas MD fluxes were not. The magnitude of the DOC and POC fluxes varied with the area flooded at high tide, but not the MD fluxes. DOC was the major form of carbon export to Sepetiba Bay. During the four tidal cycles, the forest exported a total of 1.2 kg of organic carbon per ha, mostly as DOC (60%), followed by POC (22%) and MD (18%).

An analysis of the molecular diversity of N(2) fixers and denitrifiers associated with mangrove roots was performed using terminal restriction length polymorphism (T-RFLP) of nifH (N(2) fixation) and nirS and nirK (denitrification), and the compositions and structures of these communities among three sites were compared. The number of operational taxonomic units (OTU) for nifH was higher than that for nirK or nirS at all three sites. Site 3, which had the highest organic matter and sand content in the rhizosphere sediment, as well as the lowest pore water oxygen concentration, had the highest nifH diversity. Principal component analysis of biogeochemical parameters identified soil texture, organic matter content, pore water oxygen concentration, and salinity as the main variables that differentiated the sites. Nonmetric multidimensional scaling (MDS) analyses of the T-RFLP data using the Bray-Curtis coefficient, group analyses, and pairwise comparisons between the sites clearly separated the OTU of site 3 from those of sites 1 and 2. For nirS, there were statistically significant differences in the composition of OTU among the sites, but the variability was less than for nifH. OTU defined on the basis of nirK were highly similar, and the three sites were not clearly separated on the basis of these sequences. The phylogenetic trees of nifH, nirK, and nirS showed that most of the cloned sequences were more similar to sequences from the rhizosphere isolates than to those from known strains or from other environments.

Distribution, dynamics and mass budget of phosphorus and nitrogen in a red mangrove forest were studied in the Potengi mangrove forest in northern Brazil (lat. 5 degrees 42' and 5 degrees 53'S, long. 35 degrees 5' and 35 degrees 25'W). Tidal hydrology, net primary productivity, leaf litter decomposition rate and standing stock of leaf litter in a red mangrove forest were measured. The results showed that the main reservoir for total P and total N was the sediment with 309 kg ha(-1) and 4619 kg ha(-1) (77% and 95% of the total P and N content in the mangrove forest), respectively, for the two elements. Total P and total N in Rhizophora mangle trees accounted for 145+/-14 kg ha(-1) and 216+/-23 kg ha(-1) (23% and 5% of the total P and N in the mangrove forest). The estimated average export rates for P and N through leaf litter are 0.5 kg ha(-1)yr(-1) and 1.6 kg ha(-1)yr(-1) respectively. Our measurements support previous results in concluding that mangrove forests efficiently retain P and N.

Six short sediment cores were collected from different coastal wetlands of Quanzhou Bay in order to obtain the particle size distribution and median grain size by laser particle size analyzer, and the contents of total organic carbon (TOC), total nitrogen (TN) and total inorganic carbon (TIC) by element analyzer. Analysis results show that sediment in coastal wetlands of Quanzhou Bay can be classified as silt and clayey-silt, and the median grain size varies from 9.2 microm to 18.5 microm. The TIC content in bare flat sediments of Shuitou area is about 0.137%, which is higher than that in coastal wetland covered by Spartina alterniflora (0.014%-0.038%). TIC content decreases when grain size decreases in these sediments. Contents of TOC and TN vary from 0.939% to 2.057% and from 0.163% to 0.260% respectively. Spartina alterniflora has a strong absorption ability of carbon and nitrogen while mangrove has a weak one, and sewage discharge increases the TOC content in the sediments of Shuitou area which is higher than that of Luoyangjiang River estuary. Weak correlations occur between the contents of TOC and TN and median grain size; a typical strong positive relationship is observed between TOC and TN contents; and significant positive relationships of TN content with C/N ratio in Spartina alterniflora wetland and TOC content with C/N ratio in Spartina alterniflora wetland and bare flat are also observed. All these data indicate that the sources of TOC and TN in the coastal wetland sediments of Quanzhou Bay originate from sewage discharge and biogenic production.

Inoculation of azotobacter has significant positive effects on the growth characteristics and pigments in mangrove seedlings of Avicennia marina and Ceriops decandra. The bacterial inoculation significantly increased the root dry biomass at the maximum of 75.8% at 30 gl(-1) salinity in Ceriops decandra. But in Avicennia marina, the shoot dry biomass was increased significantly at the maximum of 56.12% at 30 gl(-1) salinity in general, the Azotobacter beijerinkii improved the growth characteristics better in both species of mangroves preferably at higher salinity levels in A. marina and at a range of salinity in C. decandra. The results recommend this forraising vigorous seedlings under nursery conditions.

A greenhouse experiment was conducted to study the partitioning and removal of Cd and Mn from wastewater using constructed mangrove (Kandelia candel) wetland treatment system. Three different strengths of artificial wastewater passed through the system in fixed quantities. Artificial seawater was used as a control. Three different compositions were natural wastewater concentration (C1), medium wastewater concentration (C5) and concentrated wastewater concentrations (C10). C1 had the characteristics and strength similar to natural municipal wastewater while C5 and C10 contained five and ten times of the nutrients and heavy metals in C1, respectively. Results showed that the major portion of the Cd and Mn entering the simulated wastewater treatment system entered the sediment pool where approximately 88% to 95% of the Cd, and between 63% and 89% of Mn, was retained. The amount of added Cd and Mn in the wastewater found in plants were between 0.16% to 1.1%, and 1.7% to 13.9%, respectively. Within the total plant pool, roots accounted for between 30% and 39% of Cd, and from 0.65% to 7.3% of Mn; leaves contained between 19.9% to 30.5% of Cd, and from 7.8% to 41.0% of Mn; litterfall contained 12.3% to 20.6% of Cd, and from 15.2% to 70.3% of Mn, respectively. The averaged accumulative coefficients concentration in plant tissues/concentration in sediment in plant for Cd and Mn were 1.22 to 2.40 and 0.02 to 0.08, respectively. Assimilated Cd and Mn were stored in non-activity plant zones such as cell wall, supplimentary cells of the lenticel, stone cells, cell gaps in root and stem, etc. Kandelia candel seedlings had a relative high toxicity resistance to the two heavy metals.

The effects of multiple heavy metal stress on the activity of antioxidative enzymes and lipid peroxidation were studied in leaves and roots of two mangrove plants, Kandelia candel and Bruguiera gymnorrhiza, grown under control (10 per thousand NaCl nutrient solution) or five levels of multiple heavy metal stress (10 per thousand NaCl nutrient solution containing different concentration of Pb2+, Cd2+, and Hg2+). Leaves and roots of control and heavy metal-stressed plants were harvested after two months. In leaves of heavy metal-stressed plants superoxide dismutase (SOD) and peroxidase (POD) activities fluctuated in different stress levels compared to the control, while catalase (CAT) activity increased with stress levels in K. candel, but remained unchanged in leaves of B. gymnorrhiza. In comparison with the control, the dynamic tendency of SOD, CAT, and POD activities in roots of heavy metal-stressed plants all ascended, and then declined. The increase in enzyme activities demonstrated that K. candel is more tolerant to heavy metals than B. gymnorrhiza. Lipid peroxidation was enhanced only in leaves of heavy metal-stressed B. gymnorrhiza. These results indicate that in heavy-metal stress antioxidative activities may play an important role in K. candel and B. gymnorrhiza and that cell membrane in leaves and roots of K. candel have greater stability than those of B. gymnorrhiza. For pollution monitoring purposes, POD activity in roots and leaves maybe serve as a biomarker of heavy metal stress in K. candel, while lipid peroxidation maybe serve as biomarker in B. gymnorrhiza.

Root respiration uses a significant proportion of photosynthetically fixed carbon (C) and is a globally important source of C liberated from soils. Mangroves, which are an important and productive forest resource in many tropical and subtropical countries, sustain a high ratio of root to shoot biomass which may indicate that root respiration is a particularly important component in mangrove forest carbon budgets. Mangroves are often exposed to nutrient pollution from coastal waters. Here we assessed the magnitude of fine root respiration in mangrove forests in Belize and investigated how root respiration is influenced by nutrient additions. Respiration rates of excised fine roots of the mangrove, Rhizophora mangle L., were low (4.01 +/- 0.16 nmol CO(2) g(-1) s(-1)) compared to those measured in temperate tree species at similar temperatures. In an experiment where trees where fertilized with nitrogen (N) or phosphorus (P) in low productivity dwarf forests (1-2 m height) and more productive, taller (4- 7 m height) seaward fringing forests, respiration of fine roots did not vary consistently with fertilization treatments or with forest stature. Fine roots of taller fringe trees had higher concentrations of both N and P compared to dwarf trees. Fertilization with P enhanced fine root P concentrations in both dwarf and fringe trees, but reduced root N concentrations compared to controls. Fertilization with N had no effect on root N or P concentrations. Unlike photosynthetic C gain and growth, which is strongly limited by P availability in dwarf forests at this site, fine root respiration (expressed on a mass basis) was variable, but showed no significant enhancements with nutrient additions. Variation in fine root production and standing biomass are, therefore, likely to be more important factors determining C efflux from mangrove sediments than variations in fine root respiration per unit mass.

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation-light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings.

We measured the voltage between two Ag/AgCl electrodes, one inserted into the seedling of the salt-tolerant plant Bruguiera gymnorrhiza and the other into the vermiculite in which the seedling was potted. Four seedlings were placed in different environments, in saltwater or pure water, with light or alternating light/dark conditions. We have found that (1) the voltage profiles showed periodical oscillatory behavior; (2) seedlings in saltwater showed higher voltage compared to the ones in pure water; (3) in the light environment, the voltage was higher compared to the one in the dark environment; (4) in the dark environment, a voltage wave was hardly observable; and (5) electrodes inserted into the propagule cortex, stem cortex, and petiole showed different voltage wave amplitudes. The voltage profiles will provide an effective way to evaluate the movement of salt water inside the salt-tolerant plant.

Spatial gradients in mangrove tree height in barrier islands of Belize are associated with nutrient deficiency and sustained flooding in the absence of a salinity gradient. While nutrient deficiency is likely to affect many parameters, here we show that addition of phosphorus (P) to dwarf mangroves stimulated increases in diameters of xylem vessels, area of conductive xylem tissue and leaf area index (LAI) of the canopy. These changes in structure were consistent with related changes in function, as addition of P also increased hydraulic conductivity (Ks), stomatal conductance and photosynthetic assimilation rates to the same levels measured in taller trees fringing the seaward margin of the mangrove. Increased xylem vessel size and corresponding enhancements in stem hydraulic conductivity in P fertilized dwarf trees came at the cost of enhanced mid-day loss of hydraulic conductivity and was associated with decreased assimilation rates in the afternoon. Analysis of trait plasticity identifies hydraulic properties of trees as more plastic than those of leaf structural and physiological characteristics, implying that hydraulic properties are key in controlling growth in mangroves. Alleviation of P deficiency, which released trees from hydraulic limitations, reduced the structural and functional distinctions between dwarf and taller fringing tree forms of Rhizophora mangle.

While H2O2 has been implicated in numerous plant environmental responses, normal levels and variabilities are poorly established, and estimates of leaf tissue concentrations span more than three orders of magnitude, even in a single species under similar conditions. Here, leaf tissue H2O2 contents under natural conditions are reported after determining (i) that H2O2 in extracts was stable with time, (ii) that H2O2 added to the extract was recovered quantitatively, and (iii) that the H2O2 calibration curve was unaffected (or quantifiably affected) by the extract. The broad applicability of the protocol and variability in leaf concentrations were demonstrated using tissue collected from several habitats in association with three, more extensive, experiments. The first involved nychthemeral studies of the mangrove, Rhizophora mangle L. Lowest H2O2 levels occurred in the early morning and near sunset, with higher levels both at midday and at night. Second, using five temperate species in Spring, concentrations were compared on a warm, sunny day and a cool, cloudy day. Higher concentrations were found on the warm day for Aesculus glabra Willd., Glechoma hederacea L., Plantago major L., and Viola soraria Willd., while there were no differences in Quercus macrocarpa Michx. Finally, the effects of elevated CO2 and ozone were examined in soybean, Glycine max L. Pioneer 93B15 under Free Air gas Concentration Enrichment (FACE) conditions. Both supplements led to elevated H2O2. Overall, mean leaf, midday, and mid-summer H2O2 concentrations ranged from 0.67 micromol (gFW)(-1) in mangrove to 3.6 micromol (gFW)(-1) in A. glabra Willd. Greatest within-species differences were only 2.5-fold in any of the studies.

Mangrove ecosystems can be either nitrogen (N) or phosphorus (P) limited and are therefore vulnerable to nutrient pollution. Nutrient enrichment with either N or P may have differing effects on ecosystems because of underlying differences in plant physiological responses to these nutrients in either N- or P-limited settings. Using a common mangrove species, Avicennia germinans, in sites where growth was either N or P limited, we investigated differing physiological responses to N and P limitation and fertilization. We tested the hypothesis that water uptake and transport, and hydraulic architecture, were the main processes limiting productivity at the P-limited site, but that this was not the case at the N-limited site. We found that plants at the P-deficient site had lower leaf water potential, stomatal conductance and photosynthetic carbon-assimilation rates, and less conductive xylem, than those at the N-limited site. These differences were greatly reduced with P fertilization at the P-limited site. By contrast, fertilization with N at the N-limited site had little effect on either photosynthetic or hydraulic traits. We conclude that growth in N- and P-limited sites differentially affect the hydraulic pathways of mangroves. Plants experiencing P limitation appear to be water deficient and undergo more pronounced changes in structure and function with relief of nutrient deficiency than those in N-limited ecosystems.

The processing waste of the aerial roots of Rhizophora mangle was used in both its unmodified or mercaptoacetic acid (MAA) modified form for the sorption of Pb2+ from aqueous solution. The biomass rapidly and strongly sorbed Pb2+ at pH 5.0, which indicated chemisorption. A significant increase in Pb2+ sorption resulted from MAA treatment of the biomass, indicating that sorption occurs through an ion-exchange process. From sorption-capacity experiments, the unmodified and modified materials extracted, at pH 5, 31.3 and 85.5 mg of Pb2+ per gram of biomass, respectively, from aqueous solutions. Our studies may contribute to an innovative method for the economical and ecologically save removal and recovery of heavy-atom metal ions from contaminated waters through biosorption.

A di-n-butyl phthalate (DBP)degrading bacterium Rhodococcus ruber was isolated from mangrove soil, and its degrading characteristics were studied. The results showed that the bacterium could grow well on the substrate with DBP as the sole source of carbon and energy, and the DBP of 50 mg x L(-1) could be completely degraded after 48 h. Under aerobic condition, the tentative pathway proposed for DBP degradation was through monoester initially, then phthalic acid, and finally CO2 and H2O.

A significant decrease in the amount of a protein, whose migration in two-dimensional gel electrophoresis corresponds to an apparent molecular mass of 23 kDa and pI = 6.5, was observed in leaves of NaCl-treated Bruguiera parviflora (Roxb.) Wt. & Arn. ex Griff. seedlings. This particular salt-sensitive protein, designated as SSP-23, almost disappeared after 45 days of treatment in 400 mM NaCl as compared to untreated seedlings (0 mM NaCl) where the presence of the protein was significant. A polyclonal antibody raised against the 23-kDa protein was used to determine the subcellular localization of this protein in leaves by cross-reaction with proteins from isolated chloroplasts, mitochondria, peroxisomes and cytosol fractions on Western blots. SSP-23 was confirmed to be localized in the cytosol by immunoblotting. The disappearance of SSP-23 as a result of high NaCl treatment suggests that this protein is salt-sensitive and has a possible role in salt adaptation.

The most remarkable morphological specializations of mangroves are vivipary, salt secretion, and aerial roots. There has been a long debate on whether the complex traits vivipary and secreters have a single origin, the answer to which has profound implications for the mechanism of evolution in mangroves. We took a large and representative sample across mangroves and sequenced the 18S rRNA, rbcL, and matR genes. Together with the outgroups, our data yielded a high resolution phylogeny which allowed us to gain much needed insight into the distributions of the two characters and address their evolutionary origins. For each character, its ancestral state in the phylogeny was estimated by the maximum likelihood method. Overall evidence is in favor of a multiple origin for both vivipary and salt secretion in mangroves.

The polycyclic aromatic hydrocarbons(PAHs) concentrations were determined in the root of three mangrove species (Kandelia candel, Avicennia marina and Bruguiera gymnorrhiza) and their growing environment (sediment) in mangrove wetlands of Jiulong River Estuary, Fujian, China. The total PAHs (16 parent PAHs) in mangrove sediments ranged from 193.44 to 270.53 ng/g dw, with a mean value of 231.76 +/- 31.78 ng/g dw. Compared with other mangrove and coastal marine sediments, the PAHs concentrations of all the sampling areas in this study were at relatively lower level. The total PAHs (13 parent PAHs) values varied from 30.83 to 62.73 ng/g dw in mangrove roots. Benzo[a]pyrene(five-ring), fluoranthene(four-ring) and pyrene(four-ring) dominated in mangrove sediments. Based on ratios of phenathrene/anthracene, fluoranthene/pyrene and fluoranthene/pyrene + fluoranthene, the main possible sources of surface sediment PAHs were identified as grass, wood or coal combustion for mangrove wetlands of Jiulong River Estuary. Naphthalene(two-ring) and phenathrene(three-ring) were the most abundant compounds in mangrove roots. Sediment-to-vegetation bioconcentration factors (BCF(SV) S) were calculated and their relationships with PAHs' physico-chemical properties were investigated. The average BCF(SV) S of PAHs for three mangrove species roots were almost all under the level of 1 except for naphthalene. Good linear relationship between BCF(SV) values for mangrove roots and PAHs water solubility, octanol-water partitioning coefficients was derived in present study. The solubility and the octanol-water partition coefficient were proved to be good predictors for the accumulation of PAHs in mangrove roots, respectively.

The influence of varying levels of salinity (0, 100, 200 and 400 mM) on the activities of nitrate reductase (NR, E.C. 1.6.6.1), acid phosphatase (ACP, E.C. 3.1.3.2), and alkaline phosphatase (ALP, EC 3.1.3.1 ) as well as on nitrate and phosphate uptake and total nitrogen levels in leaves of a true mangrove Bruguiera parviflora was investigated under hydroponic culture conditions. NR activity increased in 100mM NaCl treated plants, whereas it decreased gradually in 200 and 400 mM treated plants, relative to the controls. Decreased activity of NR by NaCl stress was also accompanied by a decrease in total nitrogen level and nitrate uptake. Decreases in NR activity, nitrate (NO3-), and total nitrogen level due to high salinity may be responsible for a decrease in growth and biomass production in this plant. However, salinity caused an increase in both ACP and ALP activity. Activity staining of ACP by native polyacrylamide gel electrophoresis revealed three isoforms: ACP-1, ACP-2, and ACP-3. We observed a preferential enhancement in the ACP-3 isoform by salinity. In order to understand whether the salinity-induced increase in phosphatase activity was due to inhibition in phosphate uptake, we monitored phosphate (Pi) levels in leaves and noted that phosphate levels decreased significantly under salinity. These results suggest that the induction of acid and ALP under salt stress may be due to a phosphorous deficiency.

In order to assess the role of the antioxidative defense system against salt treatment, the activities of some antioxidative enzymes and levels of antioxidants were monitored in a true mangrove, Bruguiera parviflora, subjected to varying levels of NaCl under hydroponic culture. In the leaves of B. parviflora, salt treatment preferentially enhanced the content of H2O2 as well as the activity of ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione reductase (GR), and superoxide dismutase (SOD), whereas it induced the decrease of total ascorbate and glutathione (GSH+GSSG) content as well as catalase (CAT) activity. Analysis of isoforms of antioxidative enzymes by native PAGE and activity staining revealed that leaves of B. parviflora had one isoform each of Mn-SOD and Cu/Zn-SOD and three isoforms of Fe-SOD. Expression of Mn-SOD and Fe-SOD-2 was preferentially elevated by NaCl. Similarly, out of the six isoforms of GPX, the GPX-1, 2, 3 and 6 were enhanced by salt treatment but the levels of GPX-4 and -5 changed minimally as compared to those of a control. Activity staining gel revealed only one prominent isoform of APX and two isoforms of GR (GR-1 and GR-2), all of these isoforms increased upon salt exposure. Four CAT-isoforms were identified, among which the prominent CAT-2 isoform level was maximally reduced, suggesting differential down regulation of CAT isoforms by NaCl. The concentrations of malondialdehyde (MDA), a product of lipid peroxidation, remained unchanged in leaves of the plant treated with different concentrations of NaCl. This suggests that plants are protected against activated oxygen species by the elevated levels of certain antioxidative enzymes, thus avoiding lipid peroxidation during salt exposure. The differential changes in the levels of the isoforms due to NaCl treatment may be useful as markers for recognizing salt tolerance in mangroves.

Two-month-old seedlings of Bruguiera parvifora were treated with varying levels of NaCl (100, 200 and 400 mM) under hydroponic culture. Total proteins were extracted from leaves of control and NaCl treated plants after 7, 14, 30 and 45 d of treatment and analysed by SDS-PAGE. As visualized from SDS-PAGE, the intensity of several protein bands of molecular weight 17, 23, 32, 33 and 34 kDa decreased as a result of NaCl treatment. The degree of decrease of these protein bands seemed to be roughly proportional to the external NaCl concentration. The most obvious change concerned a 23 kDa-polypeptide (SSP-23), which disappeared after 45 d treatment in 400 mM NaCl. Moreover, the SSP-23 protein, which disappeared in B. parviflora under salinity stress, reappeared when these salinized seedlings were desalinized. These observations suggest the possible involvement of these polypeptides for osmotic adjustment under salt stress. NaCl stress also caused an increase in the activity of both acid and alkaline protease. The increasing activity of proteases functions as a signal of salt stress in B. parviflora, which induces the reduction of protein level.