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Background Mangroves plants, an important wetland system in the intertidal shores, play a vital role in estuarine ecosystems. However, there is a lack of a very effective method for extracting protein from mangrove plants for proteomic analysis. Here, we evaluated the efficiency of three different protein extraction methods for proteomic analysis of total proteins obtained from mangrove plant Kandelia obovata leaves. Results The protein yield of the phenol-based (Phe-B) method (4.47 mg/g) was significantly higher than the yields of the traditional phenol (Phe) method (2.38 mg/g) and trichloroacetic acid-acetone (TCA-A) method (1.15 mg/g). The Phe-B method produced better two-dimensional electrophoresis (2-DE) protein patterns with high reproducibility regarding the number, abundance and coverage of protein spots. The 2-DE gels showed that 847, 650 and 213 unique protein spots were separated from the total K. obovata leaf proteins extracted by the Phe-B, Phe and TCA-A methods, respectively. Fourteen pairs of protein spots were randomly selected from 2-DE gels of Phe- and Phe-B- extracted proteins for identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF-MS) technique, and the results of three pairs were consistent. Further, oxygen evolving enhancer protein and elongation factor Tu could be observed in the 2-DE gels of Phe and Phe-B methods, but could only be detected in the results of the Phe-B methods, showing that Phe-B method might be the optimized choice for proteomic analysis. Conclusion Our data provides an improved Phe-B method for protein extraction of K. obovata and other mangrove plant tissues which is rich in polysaccharides and polyphenols. This study might be expected to be used for proteomic analysis in other recalcitrant plants.

In this study, Illumina MiSeq sequencing of the 16 S rRNA gene was used to describe the bacterial communities in the South China Sea (SCS) during the southwest monsoon period. We targeted different regions in the SCS and showed that bacterial community was driven by the effects of the river, upwelling, and mesoscale eddy through changing the environmental factors (salinity, temperature, and nutrients). Distinct bacterial communities were observed among different chemical conditions, especially between the estuary and the open sea. The abundance of Burkholderiales, Frankiales, Flavobacteriales, and Rhodobacterales dominated the estuary and its adjacent waters. Bacteria in cyclonic eddy were dominated by Methylophilales and Pseudomonadales, whereas Prochlorococcus, SAR11 clade, and Oceanospirillales had relatively high abundance in the anticyclonic eddy. Overall, the abundance of specific phylotypes significantly varied among samples with different chemical conditions. Chemical conditions probably act as a driver that shapes and controls the diversity of bacteria in the SCS. This study suggests that the interaction between microbial and environmental conditions needs to be further considered to fully understand the diversity and function of marine microbes.

Seagrass meadows have seriously deteriorated in recent years. Seagrass associated phytate-mineralizing rhizobacteria potentially have functions related to seagrass nutrition, health and sustainable growth. The β-propeller phytases (BPPs) are the only phytase family in aquatic environments, but there are few studies on the BPP community structure of seagrass. In this study, clone libraries and quantitative PCR (qPCR) assays were used to compare the diversity and abundances of the BPP communities of Halodule endl, Halophila ovalis and Thalassia hemprichii in Xisha and Sanya, and to investigate the distribution characteristics of BPP genes in the rhizosphere sediment, which provedes insight into species specialty from phytic mineralization in subtropical and tropical seagrass ecosystems. The highest diversity of BPP genes was found for Thalassia hemprichii in Sanya Bay. Thalassia hemprichii in Sanya had higher abundances of BPPs, which were linked to Gammaproteobacteria. The BPP community diversity and OTUs of Thalassia hemprichii in Sanya were much higher than those of Thalassia hemprichii on Yongxing Island and Stone Island. The seagrass BPP communities had higher diversity and evenness from sampling sites with more human activity. The qPCR results showed that the abundance of phytate acid-degradating bacteria was approximately three times larger in Thalassia hemprichii rhizosphere sediment samples than in Halodule endl and Halophila ovalis rhizosphere sediment samples. This study highlighted that the diversity and abundances of bacteria genetically encoding BPP in the rhizosphere of Thalassia hemprichii were clearly higher than those of Halodule endl and Halophila ovalis. Further study of microbial phosphorus cycling will provide new insights into seagrass meadow ecosystems.

Coral reef ecosystems usually distribute in oligotrophic tropical and subtropical marine environments, but they possess great biodiversity and high productivity. It may attribute to its efficient internal nutrient cycle system. However, the knowledge of functional microbial community structure is still limited. In this study, both functional gene array (Geochip 5.0) and nifH Illumina sequencing were used to profile the overall functional genes and diazotrophic communities associated with coral Porites pukoensis. More than 7500 microbial functional genes were detected from archaea, bacteria, and fungi. Most of these genes are related to the transformation of carbon, nitrogen, sulfur, and phosphorus, providing evidence that microbes in the coral holobiont play important roles in the biogeochemical cycle of coral reef ecosystems. Our results indicated a high diversity of diazotrophs associated with corals. The dominant diazotrophic groups were related to phyla Alphaproteobacteria, Deltaproteobacteria, Cyanobacteria, and Gammaproteobacteria. And the dominant diazotrophic communities were divided into four clusters. They were affiliated with nifH sequences from genera Zymomonas, Halorhodospira, Leptolyngbya, Trichormus, and Desulfovibrio, indicating these groups may play a more important role in the nitrogen-fixing process in the coral holobiont. This study revealed functional gene diversity and suggested the roles they played in the biogeochemical cycling of the coral holobiont.

The present study aimed to explore the possible functions of radial oxygen loss (ROL) on mangrove nutrition. A field survey was conducted to explore the relations among ROL, root anatomy and leaf N in different mangrove species along a continuous tidal gradient. Three mangroves with different ROL (Avicennia marina [A. marina], Kandelia obovata and Rhizophora stylosa) were then selected to further explore the dynamics of N at the root-soil interface. The results showed that seaward pioneer mangrove species such as A. marina appeared to exhibit higher leaf N despite growing under poorer nutrient conditions. Greater leaf N in pioneer mangroves coincided with their special root structure (e.g., high porosity together with a thin lignified/suberized exodermis) and powerful ROL. An interesting positive relation was observed between ROL and leaf N in mangroves. Moreover, rhizo-box data further showed that soil nitrification was also strongly correlated with ROL. A. marina, which had the highest ROL among the three mangrove species studied, consistently possessed the highest levels of NO3−, nitrification and ammonia-oxidizing bacteria and archaea gene copies in the rhizosphere. Besides, both NO3− and NH4+ influxes were found to be higher in the roots of A. marina when compared to those of K. obovata and R. stylosa. In summary, greater N acquisition by pioneer mangroves such as A. marina was strongly correlated with ROL which would regulate N transformation and translocation at the root-soil interface. The implications of this study may be significant in mangrove nutrition and the mechanisms involved in mangrove zonation.

A two-dimensional flow model coupled with a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model was applied to simulate the thermal discharge of two nuclear power plants near Daya Bay of South China Sea, and their impact on hydrodynamic conditions and ecosystem. The results show that the thermal discharge influence area of neap tide is much larger than spring tide, and the high and mid temperature rise area in winter is much larger than that in summer. More importantly, the present data further confirmed that the Daya Bay ecosystem has significant responses to the thermal discharge in nutrients, phytoplankton and zooplankton. In winter and early spring, the thermal discharge facilitates the growth of phytoplankton and their abundance often peak in March and April. In summer, the thermal discharge inhibits the growth of phytoplankton and their abundance keep at a low level from June to August. Although the abundance of zooplankton changed with phytoplankton, the characteristic of seasonal variation of zooplankton do not coincide with the phytoplankton, but are lagged in time, by nearly one month. Moreover, the concentration of nutrients and chlorophyll a were compared between thermal discharge and the nearby aquaculture, which has shown that the aquaculture contributed more to the eutrophication.

The present work isolated a CBF/DREB1 gene from mangrove Bruguiera gymnorrhiza (BgCBF1) and compared its expression levels in various tissues under normal condition and cold stress, and in leaves exposed to various environmental stimuli. Results showed that the BgCBF1 deduced protein showed almost 100% similarities to that of AcCBF1 from Aegiceras corniculatum and AmCBF1 from Avicennia marina. Real-time quantitative PCR analysis showed that BgCBF1 gene displayed constitute expression in leaf, stem and root samples of plantlets under normal condition, but with different expression levels and tissue preference. When exposed to cold, BgCBF1 could be rapidly, slightly and transiently induced in all tissues. Furthermore, the BgCBF1 gene in leaves displayed a transient and small induction after salt and drought (PEG) exposure, while exhibited relatively high up-regulated expression after the phytohormone abscisic acid (ABA) treatment. These results suggest that the BgCBF1 gene may participate in the ABA mediated development and protection of plant against cold and drought. Further studies on its promoters and downstream genes will be needed to better understand its functions.

Considered as an essential calcium sensor, the calcium-dependent protein kinase (CDPK) family plays a critical part in terrestrial plants' responses to both biotic and abiotic stresses. In the study, Avicennia marina was proved to have better heat tolerance than other species. A CDPK gene was cloned from mangrove species A. marina using RACE-PCR and designated as AmCDPK. By predicting and analyzing its properties, structures and expression patterns, we found that the amino acid sequence, containing a kinase domain and four EF-hand Ca2+-binding sites, shared high identity with Handroanthus impetiginosus and Sesamum indicum. Quantitative real-time PCR data analysis suggested that AmCDPK demonstrated significant up-regulation under heat stress. It is likely that AmCDPK is a versatile gene involved in various stresses, including dehydration, cold, light, defense and ABA stress responses by analyzing cis-elements. It is the first time that CDPKs from mangroves have been cloned and our results brought evidence to the effect of AmCDPK on heat stress, which is particularly important under the background of global warming.

Daya Bay is facing the influence of human activities and nature changes, which result in phytoplankton adjusting to the changing environment. The data about environmental changes and phytoplankton were obtained from four seasonal cruises in 2013 in the bay. It is helpful to explore seasonal succession of phytoplankton driven by the determining environmental factors in this bay. Temperature is a significant indicator of season change. The limiting factor of phytoplankton growth totally changed from P (PO4-P) limiting during the southwest monsoon to Si (SiO3-Si) limiting during northeast monsoon. The order of diatoms and dinoflagellates was the dominant phytoplankton groups in Daya Bay. The dominant species included chain-forming diatoms (Skeletonema, Pseudo-nitzschia, Thalassionema, Chaetoceros and Rhizosolenia) were found all the year round and filamentous cyanobacteria (Trichodesmium) in spring and autumn. Partial least square regression (PLS) found that salinity, temperature and nutrients were important driving force for phytoplankton seasonal succession.

AimsCu, Pb and Cd are common heavy metals in mangroves. Objective to clone chitinase I gene in mangrove plants and explore the role of chitinase I gene in plants under heavy metal stress. MethodsHomologous cloning and RACE cloning were used to clone chitinase type I gene in mangrove plants, and bioinformatics analysis software was used to analyze and predict gene structure and functional domain. The mRNA expression pattern of chitinase gene in mangrove plants under heavy metal stress was analyzed by real-time quantitative PCR analysis. ResultsAll Four cDNA with a full length of 1092 bp, and an ORF (open reading frame) 831 bp, coding with 276 amino acids, while are differences in the sequences among the four species. Four genes owned signal peptide and were located at vacuole inside the cell. Protein sequence domain analysis indicates that all have the same typical structural characteristics of GH19 chitinase family. The sequence of CHI had high similarity to the protein sequences of Camellia fraternal chitinases. Real-time PCR was used to analyze the expression of CHI under different concentration heavy metal with time of four mangrove species. The gene expression of CHI I was highly induced in the B.gymnorrhiza leaves than other mangrove species. With the increase of heavy metal stress time, the expression level of B.gymnorrhiza increased continuously.ConclusionChitinase was induced under heavy metal in mangrove plants, and chitinase plays an active part in heavy metal tolerance in mangrove plants which was located at vacuole inside the cell.

Cold events had broadly affected the survival and geographic distribution of mangrove plants. Kandelia obovata, has an excellent cold tolerance as a true halophyte and widespread mangrove species. In this study, physiological characters and comparative proteomics of leaves of K. obovata were performed under cold treatment. The physiological analysis showed that K. obovata could alleviate its cold-stress injuries through increasing the levels of antioxidants, the activities of related enzymes, as well as osmotic regulation substances (proline). It was detected 184 differentially expressed protein spots, and of 129 (70.11%) spots were identified. These proteins have been involved in several pathways such as the stress and defense, photosynthesis and photorespiration, signal transduction, transcription factors, protein biosynthesis and degradation, molecular chaperones, ATP synthesis, the tricarboxylic acid (TCA) cycle and primary metabolisms. The protein post-translational modification may be a common phenomenon and plays a key role in cold-response process in K. obovata. According to our precious work, a schematic diagram was drawn for the resistance or adaptation strategy of mangrove plants under cold stress. This study provided valuable information to understand the mechanism of cold tolerance of K. obovata.

This is the first study exploring the effects of persistent Cr(VI) treatment on microbial communities and function as well as the process efficiency of an A2O system. The inhibitory effect was clearly higher at a high Cr(VI) concentration than a low Cr(VI) concentration, and different Cr(VI) concentrations had distinct effects on the microbial communities as well as on the performance efficiency of the system. Functional annotation analysis indicated that Cr(VI) stress inhibited most of the metabolic pathway and functional genes of the microbial communities, especially those involved in the denitrification pathway. Network analysis was used to investigate the co-occurrence patterns between denitrification genes and microbial taxa; the results indicated that microorganisms with functional genes had high diversity and were adversely affected by Cr(VI) exposure. This study is the first to establish a relationship between Cr(VI) stress and microbial communities and function as well as to determine the underlying mechanisms and roles of Cr(VI) in A2O sludge.

Background WRKY transcription factors play key roles in plant development processes and stress response. Kandelia obovata is the most cold-resistant species of mangrove plants, which are the important contributors to coastal marine environment. However, there is little known about the WRKY genes in K. obovata. Results In this study, a WRKY transcription factor gene, named KoWRKY40, was identified from mangrove plant K. obovata. The full-length cDNA of KoWRKY40 gene was 1420 nucleotide bases, which encoded 318 amino acids. The KoWRKY40 protein contained a typical WRKY domain and a C2H2 zinc-finger motif, which were common signatures to group II of WRKY family. The three-dimensional (3D) model of KoWRKY40 was formed by one α-helix and five β-strands. Evolutionary analysis revealed that KoWRKY40 has the closest homology with a WRKY protein from another mangrove plant Bruguiera gymnorhiza. The KoWRKY40 protein was verified to be exclusively located in nucleus of tobacco epidermis cells. Gene expression analysis demonstrated that KoWRKY40 was induced highly in the roots and leaves, but lowly in stems in K. obovata under cold stress. Overexpression of KoWRKY40 in Arabidopsis significantly enhanced the fresh weight, root length, and lateral root number of the transgenic lines under cold stress. KoWRKY40 transgenic Arabidopsis exhibited higher proline content, SOD, POD, and CAT activities, and lower MDA content, and H2O2 content than wild-type Arabidopsis under cold stress condition. Cold stress affected the expression of genes related to proline biosynthesis, antioxidant system, and the ICE-CBF-COR signaling pathway, including AtP5CS1, AtPRODH1, AtMnSOD, AtPOD, AtCAT1, AtCBF1, AtCBF2, AtICE1, AtCOR47 in KoWRKY40 transgenic Arabidopsis plants. Conclusion These results demonstrated that KoWRKY40 conferred cold tolerance in transgenic Arabidopsis by regulating plant growth, osmotic balance, the antioxidant system, and ICE-CBF-COR signaling pathway. The study indicates that KoWRKY40 is an important regulator involved in the cold stress response in plants.

It was studied for the effects of heavy metal stress on the antioxidant activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and lipid peroxidation (MDA) in the leaves of five mangrove plants. The results showed the protein concentrations were significantly higher in B. gymnorrhiza (7.55 mg prot /mL: Cu2+), K. obovata (11.21 mg prot/mL: Cd2+) and R. stylosa (12.51 mg prot/mL: Cd2+) (p

The pressure-state-response (PSR) model was applied to establish a mangrove ecosystem health evaluation system combined with analytical hierarchy process (AHP) in this paper. The mangrove wetlands are divided into five ecological levels: excellent health, good health, health, sub-health and morbidity, which is based on the comprehensive health index (CHI) value. Twelve representative sites were selected for sampling to assess the ecological health condition of mangroves. As a result, the ecological health level of Gaoqiao mangrove area is excellent health; the ecological health level of Taiping mangrove area is good health; the ecological health level of Huguang and Qi'ao mangrove area is health; the ecological health level of Techeng and He'an mangrove area is sub-health; the ecological health level of Huidong mangrove area is morbidity. These results will give some advises for ecological protection and biological resource sustainable development of mangrove ecosystem in China.

Seagrasses constitute a significant part of coral reef ecosystems, representing high primary productivity and one of the most important coastal habitats in marine ecosystems. Though seagrasses possess irreplaceable ecological services to the marine environment, taxonomical ambiguity still exists due to similar morphological characters and phenotypic plasticity. As an emerging technology, DNA barcoding can effectively identify cryptic species using a short orthologous DNA region. In this study, we collected samples from five different locations (Daya Bay, Xincun Bay, Sanya Bay, Xisha Islands, and Nansha Islands), and three seagrass species Cymodocea rotundata, Thalassia hemprichii and Halophila ovalis was evaluated. Moreover, ITS, matK and rbcL genes were used as DNA barcodes. The results indicated that single ITS and concatenated ITS/matK/rbcL both conducted better species resolution than single matK and rbcL. Nevertheless, single ITS was more convenient. Furthermore, in all the four topology trees, three species resolved as 3 clusters as well H. ovalis and T. hemprichii grouped as sister clade. In the meantime, differentiation lay in intra-species based on the result of single ITS and three-locus analysis. Within H. ovalis and T. hemprichii separately, individuals from Xisha Islands first group together, then grouped with individuals from Nansha Islands and/or Xincun Bay and/or Sanya Bay and/or Daya Bay, which indicated that geographical distribution influenced population evolution. However, intra-species differentiation did not emerge in the tree of matK or rbcL.

The pollution of polycyclic aromatic hydrocarbons was serious in sediments of the Pearl River estuary, China. A fluorene-degrading bacterium, strain A2-3, was isolated from hydrocarbon contaminated sediment of this estuary and identified as Rhodococcus sp. based on the analyses of 16S rRNA gene sequence and morphology. Rhodococcus sp. A2-3 can take naphthalene, p-Teropheny, fluorene, pyrene, salicylic acid, citric acid, acetic acid, diethyletheranhydrous, methanol or 4,4′-dibromodiphenyl ether as sole carbon source. 100% of 100 mg/L fluorene or 89% of 400 mg/L fluorene was removed in 7 days by strain A2-3 at 30 °C and pH 7.5. The strain A2-3 showed a high degradation efficiency of fluorene when pH values ranged from 5.5 to 8.5. The proposed pathway of fluorene catabolism by strain A2-3 was initially attacked by 3,4 dioxygenation. Our results suggested Rhodococcus sp. A2-3 can degrade PAHs under aerobic conditions and can function in bioremediation, particularly for weakly acid environment.

Mangrove reconstruction is an efficient approach for mangrove conservation and restoration. The present study aimed to explore the effects of mangrove reconstruction on sediment properties and bacterial community. The results showed that mangrove restoration greatly promoted sediment fertility, whereas the improvements were more obvious induced by Kandelia obovata when compared to Avicennia marina. In all the samples, the dominant top5 bacterial group were Proteobacteria (48.31-54.52%), Planctomycetes (5.98-8.48%), Bacteroidetes (4.49-11.14%) and Acidobacteria (5.69-8.16%). As for the differences among the groups, the relative abundance of Chloroflexi was higher in the sediments of K. obovata, while Bacteroidetes was more abundant in A. marina group. Furthermore, the two bacterial genera (Rhodoplanes and Novosphingobium) were more dominant in the sediments of K. obovata, while the sediments of A. marina contained higher abundance of Vibrio and Marinobacterium. Besides, bacterial community was highly correlated with mangrove species and sediment property and nutrient status. The results of this study would provide a better understanding of the ecological benefits of mangroves and highlighted the information on biogeochemical processes driven by mangrove restoration and microorganisms.

Background Low temperature is a major abiotic stress that seriously limits mangrove productivity and distribution. Kandelia obovata is the most cold-resistance specie in mangrove plants, but little is known about the molecular mechanism underlying its resistance to cold. Osmotin is a key protein associated with abiotic and biotic stress response in plants but no information about this gene in K. obovata was reported. Results In this study, a cDNA sequence encoding osmotin, KoOsmotin (GenBank accession no. KP267758), was cloned from mangrove plant K. obovata. The KoOsmotin protein was composed of 221 amino acids and showed a calculated molecular mass of 24.11 kDa with pI 4.92. The KoOsmotin contained sixteen cysteine residues and an N-terminal signal peptide, which were common signatures to most osmotins and pathogenesis-related 5 proteins. The three-dimensional (3D) model of KoOsmotin, contained one α-helix and eleven β-strands, was formed by three characteristic domains. Database comparisons of the KoOsmotin showed the closest identity (55.75%) with the osmotin 34 from Theobroma cacao. The phylogenetic tree also revealed that the KoOsmotin was clustered in the branch of osmotin/OLP (osmotin-like protien). The KoOsmotin protein was proved to be localized to both the plasma membrane and cytoplasm by the subcellular localization analysis. Gene expression showed that the KoOsmotin was induced primarily and highly in the leaves of K. obovata, but less abundantly in stems and roots. The overexpressing of KoOsmotin conferred cold tolerance in Escherichia coli cells. Conclusion As we known, this is the first study to explore the osmotin of K. obovata. Our study provided valuable clues for further exploring the function of KoOsmotin response to stress.

The importance of mangrove was widely reported. However, the potential risks of pollutants (e.g., Hg) accumulated in the mangroves are often ignored. Thus, the present study aimed to explore the distribution and risk of mercury (Hg) in the sediments of mangroves along South China Coast. Results showed that concentrations of total Hg ranged from 0.0815 to 0.6377 mg/kg, with an arithmetic mean value of 0.2503 mg/kg. The contamination index (Pi) showed mild pollution toxicity risks in NS, slight toxicity risks in DZG, QZ, SY, ND, GQ, TLG, and free pollutions in BMW, SJ, ZJK and BLHK. NS, DZG and SY scored the highest values of Igeo among the eleven mangrove regions studied, indicating moderate to heavy pollution inputs in these regions. As for the distribution of Hg in the sediments along tidal gradient, concentrations of Hg in the sediments sharply increased from seaward mudflat to landward mangrove, corresponding with the increases of TOC. In summary, the present data indicated that mangrove ecosystem is efficient in Hg reservoir. However, the potential ecological risks of Hg, especially in some mangrove regions easily affected by human activities, should be noted.

A short term pot trail was employed to evaluate the exposure of mixed heavy metals (Cu, Pb and Zn) on growth, radial oxygen loss (ROL) and root anatomy in Bruguiera gymnorrhiza. The possible function of BgC4H, a cytochrome P450 gene, on root lignification was also discussed. The exposures of mixed Cu, Pb and Zn directly reduce O2 leakage at root surface. The reduced ROL inhibited by heavy metals was mainly ascribed by the changes in root anatomical features, such as decreased root porosity together with increased lignification within the exodermis. BgC4H was found to be up-regulated after 0.5-day metal exposure, and remained higher transcript levels within 3-day metal exposure when compared to control roots. Besides, the inhibited photosynthesis may also result in less oxygen can be transported to the underground roots. In summary, the mangrove B. gymnorrhiza appeared to react to external mixed metal contaminants by developing a lignified and impermeable exodermis, and such a root barrier induced by mixed Cu, Pb and Zn appeared to be an adaptive response to block metal ions enters into the roots.

Tidal flooding can directly result in oxygen (O2) shortage, however the functions of root aeration in flooding tolerance and O2 dynamics within mangroves are still poorly understood. Thus, in this study, the correlations among waterlogging tolerance, root porosity and O2 movement within the plants were investigated using two mangrove species (Aegiceras corniculatum and Bruguiera gymnorrhiza) and a semi-mangrove Heritiera littoralis. Based on the present data, the species A. corniculatum and B. gymnorrhiza, which possessed higher root porosity, exhibited higher waterlogging tolerance, while H. littoralis is intolerant. Increased root porosity, leaf stoma, and total ROL were observed in the roots of A. corniculatum and B. gymnorrhiza growing in stagnant solution when compared to respective aerated controls. As for ROL spatial pattern along roots, external anaerobic condition could promote ROL from apical root regions but reduce ROL from basal roots, leading to a ‘tighter barrier’. In summary, the present study indicated that the plants (e.g., A. corniculatum and B. gymnorrhiza) prioritized to ensure O2 diffusion towards root tips under waterlogging by increasing aerenchyma formation and reducing O2 leakage at basal root regions.

Crab is an important benthonic animal in mangrove ecosystem, however, the potential function of crabs on nitrogen (N) transformation in mangrove ecosystems is still poorly understood. The present study aimed to explore the potential effect of crab burrows on nitrification/denitrification within the sediments. The results showed that the presence of crab burrows could directly promote soil nitrification, the regions within more crab burrows appeared to possess higher nitrification. Higher AOA and AOB gene copies were also observed in the sediments surrounding crab burrows than those in the sediments without crab burrow. On the contrary, lower nirS copies, a denitrification related gene, were detected in the sediments surrounding crab burrows. In summary, the present study proposed new evidences of nitrification enhancement deriving by crabs, the presence of crabs might be significant in alleviating nitrification inhibition and benefits the growth of mangroves under tidal flooding.

Sediment quality caused by heavy metals was investigated in the Mirs Bay and Tolo Harbor, Hong Kong, China. Samples were collected in January and July, 2010. One-way analysis of variance showed that sediment quality variables (Fe, Zn, Mn, Pb, V, Cu, Cr, Ba, Ni and As) were significantly different (p

The phytoplankton diversity and community response to physicochemical variables in mangrove zones of Guangdong Province along the South China coast was investigated from October to December, 2017. This study was set to investigate the phytoplankton community structure in the mangrove zone and assess the relationship between the physicochemical variables and phytoplankton species diversity. Physicochemical variables such as water temperature, total dissolve solids (tds), pH, salinity, turbidity, electrical conductivity (EC) and nutrient salts were measured in situ across the 27 stations. A total of 451 species of phytoplankton were identified belonging to 10 groups (Bacillariophta > Cyanophyta > Chlorophyta > Euglenophyta > Dinoflagellate > Eubacteria > Ochrophyta > Crytophyta > Rhodophyta > Charophyta) and quantified to constitute a standing crop of 7.11 × 108 cells dm−3. The principal component analysis (PCA) reveals that reactive nitrate, phosphate, electrical conductive (EC) and turbidity were the best abiotic factors that controlled the phytoplankton community structure in the area. However, Cannon Corresponding Analysis and Pearson correlation have explicitly revealed the impact of reactive nitrate, phosphate, EC and turbidity on the phytoplankton community structure. For instance, the CCA ordination revealed that species richness and evenness were positively influenced by reactive nitrate but negatively affected by EC, turbidity and water temperature. Diatoms were mostly controlled by total dissolved solids (tds) and salinity, whereas Euglena, cyanobacteria and green algae were impacted EC and turbidity, apart from the general contribution of the nutrient salts as delineated by CCA ordination. The Shannon diversity index value exposed different levels of organic pollution across the mangrove zone of which GD37 was the most impacted station.

Salt tolerance and the possible functions of suberization on salt exclusion and secretion were examined in a dominant mangrove plant, Avicennia marina. The results showed that low salinities (10‰ and 20‰) almost has no negative effect on A. marina, however significant growth inhibitions were observed in the seedlings grown in higher salinities (30‰ and 40‰). With the increases of salinity, increased tissue Na+ content and enhanced salt secretion by glands were observed. Obvious suberization thickening were detected both in the exodermis and endodermis of the roots after salt pretreatment when compared to the roots without salt treatment. More importantly, the present data further confirmed that these root apoplastic barriers would directly decrease Na+ loading into xylem. Higher salt tolerance was observed in the seedlings pre-cultivated by salty tide when compared to fresh water cultivated A. marina. In summary, this study suggests a barrier property of suberization in dealing with salt exclusion in mangroves, a moderate salt pre-treatment may benefit plant withstanding high salinity.