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Distributed in different elevations of the intertidal zone, mangrove plants suffer different periods of flooding, and with varied adaptability to waterlogging from the physiological structure to the metabolic mechanism. Associated with species distribution, transcriptome sequencing was performed to explore the interspecific differences of molecular response mechanisms among Avicennia marina, Aegiceras corniculatum, and Bruguiera gymnorrhiza under waterlogging stress. Results showed that the counts of differentially expressed genes (DEGs) in A. Marina were the highest after stress, followed by Ae. corniculatum and B. gymnorrhiza. It was found that the functions of genes with high differential expression folds (more than eight folds) in the three plants could be classified into four categories: structural regulation, transport, biosynthesis, and protection. It was also found that A. Marina has strong regulation ability in the metabolic process, which can guarantee energy supply and maintain active biosynthesis under waterlogging conditions. In addition, A. Marina was activated in the ethylene synthesis pathway to promote aerenchyma formation and to avoid root tissue hypoxia. Being different from A. Marina and B. gymnorrhiza, Ae. corniculatum down-regulated the XET, SAMS, and ACCO genes, which were involved in the cell wall regulation or ethylene formation that might indicate a different adaptive mechanism. Alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH) were cloned from A. Marina, Ae. corniculatum, and B. gymnorrhiza. The cloned genes were named as AmADH, AmLDH, AcADH, AcLDH, BgADH, and BgLDH, respectively. qRT-PCR detection verified that LDHs and ADHs were involved in the response of mangrove plants to waterlogging stress, and interspecific difference was observed. The expressions of AcADH and AcLDH were the most prominent. Combined with transcriptome, it was considered that Ae. corniculatum was more dependent on the expression of AcADH and AcLDH that might compensate the weakness of cell wall regulation, whereas A. Marina was more dependent on the regulation of cell structure reversely.

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.

The importance of mangroves in blue carbon storage has been widely reported. However, the potential contribution of microbial extracellular polymeric substances (EPS) to the carbon pool is still poorly understood in mangrove ecosystems. Thus, a natural mangrove reserve located in Gaoqiao was chosen to investigate the linkage between microbial EPS and sediment organic carbon. Sequential resin extraction, Fourier transform infrared spectroscopy (FTIR), and 16S high-throughput sequencing were employed to determine the variations in EPS and bacterial taxa in different mangrove communities. Both EPS and EPS-C increased significantly with mangrove zonation from seaward to landward, irrespective of the EPS subfractions (colloidal and bound EPS) and components (extracellular protein and polysaccharide). Moreover, both EPS and EPS-C were found to be positively correlated with soil organic carbon. The present data further showed that EPS-C accounted for 1.84~10.69% of TOC in surface sediments. Multiple functional groups (e.g., O-H, N-H, and C=O), which may provide ligands for particle adsorption and complexation, were identified by FTIR. Consistent with the ascend of EPS with mangrove zonation from seaward to landward, the highest transmittance intensity for all functional groups was consistently exhibited in EPS isolated from landward Rhizophoraceae forest. In addition, the present data also indicated an interesting positive linkage between EPS and the abundance of some specific bacterial taxa, such as Rhizobiales, Corynebacteriales, and Gaiellales. In summary, this study claims the importance of EPS in the carbon pool in mangrove ecosystems. The present study may provide a better understanding of the functions of mangroves in carbon stocks.

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.

Phytoplankton closely connects with the hydrodynamics and biogeochemical environment of the ocean. While research focusing on both the physiochemical factors and hydrodynamics regulating phytoplankton has already been conducted, the coupling mechanism between mesoscale eddies and the vertical distribution of phyto plankton in the South China Sea (SCS) is still not well understood. Here, phytoplankton was studied under one weak-cold and two warm eddies along the 18°N transect in the SCS. The results show that the vertical distribution of chlorophyll (chl-a) presented a similar pattern at all four sampling stations. The mixed layer is less than 50 m. It is the same as the meridional salinity gradients that may be distinguished above a depth of 60 m. The subsurface chlorophyll maximum at the edge of a warm (WI) and cold eddy (CI) at E413 and E411 was shallower than that at the edge of a warm eddy (WII) at E407 and E409, indicating that temperature and salinity may be the important driving factors. On the whole, mesoscale eddies had a significant influence on the vertical pattern of chl-a in the SCS during the study period.

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.

Although the low temperature is a critical growth constraint on plants, the physiological mechanism remains unclear, especially in mangrove plants. Hence, the morphological characteristics of five mangrove plants (Bruguiera gymnorrhiza, Rhizophora stylosa, Aegiceras corniculatum, Avicennia marina, and Kandelia obovata) were compared under chilling stress. The contents of hydrogen peroxide (H2O2), malondialdehyde (MDA), and proline were tested. Activities of reactive oxygen species (ROS)-scavenging enzyme [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] were also measured after chilling stress. It was concluded that K. obovata can well tolerate chilling stress, and B. gymnorrhiza suffered the most severe chilling damage. Leaf-morphology observation exhibited that K. obovata and A. corniculatum can sustain chilling stress, while B. gymnorrhiza wilted and A. marina turned brown. The content of H2O2 increased at first and subsequently decreased in all plants. MDA increased instantaneously in B. gymnorrhiza and R. stylosa but changed slowly in K. obovata and A. corniculatum. The high content of proline accumulated in B. gymnorrhiza and K. obovata. The activities of the SOD, POD, and CAT increased at first and then decreased in all mangrove species. The antioxidants maintained high activity in K. obovata while decreasing earliest in A. marina exposed to the long-term chilling stress. Principal component analysis (PCA) indicated that high antioxidant enzyme activities play key roles in chilling tolerance for mangrove plants. The longer-term chilling tolerance of K. obovata may be related to the high antioxidant enzyme activities and proline accumulation. Lower H2O2 and MDA contents strengthen the anti-chilling ability of A. corniculatum. Further investigation on the molecular mechanisms will facilitate the understanding of the anti-chilling ability of mangrove plants.

Chitinases are considered to act as defense proteins when plants are exposed to heavy metal stresses. Typical class III chitinase genes were cloned from Kandelia obovate, Bruguiera gymnorrhiza, and Rhizophora stylosa by using RT-PCR and RACE and named KoCHI III, BgCHI III, and RsCHI III. Bioinformatics analysis revealed that the three genes encoding proteins were all typical class III chitinases with the characteristic catalytic structure belonging to the family GH18 and located outside the cell. In addition, there are heavy metal binding sites in the three-dimensional spatial structure of the type III chitinase gene. Phylogenetic tree analysis indicated that CHI had the closest relationship with chitinase in Rhizophora apiculata. In mangrove plants, the balance of the oxidative system in the body is disrupted under heavy metal stress, resulting in increased H2O2 content. Real-time PCR illustrated that the expression level under heavy metal stress was significantly higher than that in the control group. Expression levels of CHI III were higher in K. obovate than in B. gymnorrhiza and R. stylosa. With the increase in heavy metal stress time, the expression level increased continuously. These results suggest that chitinase plays an important role in improving the heavy metal tolerance of mangrove plants.

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.

Distributions of Coomassie Blue stainable particles (CSP), the sources and transports, as well as their implications for nitrogen biogeochemical cycles in the Pearl River estuary (PRE) were investigated during two cruises in August 2016 and January 2017. CSPcolor concentrations (CSP concentration determined spectrophotometrically) were 73.7–685.3 μg BSA eq L–1 [μg Bovine serum albumin (BSA) equivalent liter–1] in August 2016 and 100.6–396.4 μg BSA eq L–1 in January 2017, respectively. CSP concentrations were high in low-salinity waters (a (Chl a) concentration except for the turbid mixing zone, suggesting that autochthonous phytoplankton production served as the primary source of CSP in the PRE. The concentrations of nitrogen (N) as CSP in the PRE were comparable to the nitrogen content of particulate hydrolysable amino acids (PHAA). Pictures of CSP taken by microscopy and the correlation between composition of PHAA and the ratio of Chl a/CSPcolor showed that CSP were relatively degraded due to delivery of old terrestrial protein to river section and extensive microbial degradation during mixing at the upper and middle parts of the estuary, whereas CSP in lower estuary appeared to be more labile due to higher fresh algal production. The contribution of CSP nitrogen (CSP-N) to the particulate nitrogen (PN) pool was 34.98% in summer and 30.8% in winter. The conservative estimate of CSP-N input flux in the Pearl River Delta was about 6 × 106 mol N d–1. These results suggested that CSP was a significant pool of organic nitrogen in the PRE. The study of CSP composition in terms of nitrogen provides new insight into the roles of CSP on nitrogen biogeochemical processes in the turbid and productive estuarine system.

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.

Proline is one of the most important compatible osmolyte in cells, which accumulates in response to various stresses, including salt, water deficit, heavy metal, pathogen infection and extreme temperature. In this study, a growth chamber was employed to simulate heat environment for Avicennia marina seedlings. We detected some physiological indices in the leaves of A. marina at 40 °C, including the activity of delta-1-pyrroline-5-carboxylate synthase (P5CS), the content of free proline and soluble protein, transpiration rate and membrane permeability, and discussed the relationship between these five indices and heat resistant ability. And then a P5CS gene was cloned from A. marina using homologous cloning and rapid amplification of cDNA ends methods. It was designated as AmP5CS, encoding a protein that contained a feedback inhibition site of proline, proA, proB, conserved Leu zipper, GSA-DH domain and other functional domains of P5CS protein in high plants. Expression analysis of AmP5CS gene indicated it was involved in heat stress response. It is the first time that P5CS from A. marina has been cloned and the findings laid the foundation of figuring out heat resistant mechanisms and relieving heat damage, which is significant during global warming.

Summary A coupled three-dimensional physical model and a nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model were applied to simulate the summer coastal upwelling system over the continental shelf of northern South China Sea (NSCS) and its impact on hydrographic conditions and ecosystem. The simulated results were comprehensively validated against field and satellite measurements. The model results show that the near shore ecosystem of NSCS has significant responses to the summer coastal upwelling system. The Shantou Coast to the Nanri Islands of Fujian province (YD) and the east of the Leizhou Peninsula (QD) are two main regions affected by NSCS summer coast upwelling. During summer, these two coastal areas are characterized by nearshore cold and high salinity upwelling current. Further, the summer coastal upwelling serves as a perfect nutrient pump, which lifts up and advects nutrient-rich current from deep to surface, from inner shelf to about 30 km outer shelf. This nutrient source reaches its maximum in the middle of July and then begins to decrease. However, the maximum phytoplankton and chlorophyll a do not coincide with the maximum nutrients and delay for about 10 days. Because of the intensive seasonal thermocline and the complicated current transporting through Qiongzhou strait, the ecological responding of QD is less pronounced than YD. This study has a better understanding of the physically modulated ecological responses to the NSCS summer coastal upwelling system.

Cyanobacterial community diversity in the sediment of the Pearl River Estuary in China was evaluated in this study by denaturing gradient gel electrophoresis (DGGE) during the wet and dry seasons. Nucleotide sequences obtained from DGGE bands were classified into five cyanobacterial clusters, including Synechococcus, Cyanobium, Chroococcus, Prochlorales and Tolypothrix. Synechococcus was identified as the dominant cyanobacterial group in the sediment samples; its distribution varied from the inner estuary to the outer estuary, with a wide range of salinity adaptation. Observed patterns of cyanobacterial communities changed markedly between sampling sites and seasons, suggesting that most cyanobacteria were not delivered via fresh water. Canonical correspondence analysis was conducted to determine the relationship between environmental variables and bacterial community structures during the dry season. The results suggested that the cyanobacterial community was significantly influenced by pH, salinity, PO4-P and NO3-N in sediments. La diversidad de la comunidad de cianobacterias en el sedimento del estuario del río Perla en China fue evaluada en este estudio por electroforesis en gel de gradiente desnaturalizante (DGGE) durante las estaciones húmeda y seca. Las secuencias de nucleótidos obtenidas de bandas DGGE se clasificaron en cinco grupos de cianobacterias, incluyendo Synechococcus, Cyanobium, Chroococcus, Prochlorales y Tolypothrix. Synechococcus fue identificado como el grupo dominante de cianobacterias en las muestras de sedimento, su distribución varió desde la parte interna del estuario hasta la externa, con un amplio rango de adaptación a la salinidad. Los patrones observados de las comunidades de cianobacterias cambiaron marcadamente entre diferentes sitios de muestreo en diferentes estaciones del año y sugirió que la mayoría de las cianobacterias no provenían a través del agua dulce. Se realizó un análisis de correspondencia canónica (CCA) para determinar la relación entre variables ambientales y estructuras de las comunidades bacterianas durante la estación seca. Los resultados sugirieron que las distintas comunidades de cianobacterias estaban significativamente influenciadas por el pH, salinidad, PO4-P y NO3-N en los sedimentos.

Ultraviolet (UV) radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization's measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Environmental pollution from industrialization, urbanization and agriculture is a serious issue facing all countries during economic development. The Pearl River Delta in Southern China offers a unique case for study and documentation on the ecosystem changes during the fast economic development and urbanization over the past 40 years. This collection of papers from a conference on marine coastal pollution and ecotoxicology held in Guangzhou of China provide the current status on the environmental and ecological processes from the intensive urbanization and development. The research information available from this special issue can be used for both a comparison over time and with other locations and countries, and, in addition, for policy making to serve the long-term sustainable development of the region and the world.

Mangrove wetlands possess four important characteristics as one of the unique marine ecosystems, and are found in the intertidal coastal regions of the tropics and subtropics in the world, mainly between latitudes 25° N and 25° S. The total area of the global mangrove forest is about 1.7 million hectares, spanning over 118 countries and territories. Mangroves play an important ecological role and functioning as a tropical coastal ecosystem with a total net primary productivity as high as 2000 g C·m−2·a−1. Mangrove ecosystems serve a key role in the maintenance and protection for tropical and subtropical marine biodiversity and a very important function in the global biogeochemical processes and climate change. Mangrove wetlands, situated between the terrestrial land and the oceans, are sensitive ecosystems not only to the physical environmental changes also to anthropogenic processes from urbanization and economic development. A rich diversity and communities of flora, fauna, and microorganisms is associated with the mangrove ecosystems and they include both visible organisms and non-visible ones of fungi, bacteria and archaea. These microorganisms play an important ecological role and function in the cycling of nutrients. Mangroves are typical marine ecosystems that are closely associated with the global climate change and can play a positive role. The survival and distribution of mangroves, to serve as an important ecological barrier along the coast, have also been affected by anthropogenic activities and global climate change. The present article reviews the impacts for global climate change on mangroves in terms of global warming, sea-level rising, atmospheric CO2 concentration increasing and extreme weather. It also touches onto the important microbial geochemical processes that are linked to climate change. Archaea are also given attention due to the recent findings on their ubiquity in mangrove and their potential ecological function. The global climate change will bring great challenges and opportunities to research, maintain and development of mangroves in the future.

A cruise was commissioned in the summer of 2009 to evaluate water quality in the Pearl River Estuary (PRE). Chemometrics such as Principal Component Analysis (PCA), Cluster analysis (CA) and Self-Organizing Map (SOM) were employed to identify anthropogenic and natural influences on estuary water quality. The scores of stations in the surface layer in the first principal component (PC1) were related to NH4-N, PO4-P, NO2-N, NO3-N, TP, and Chlorophyll a while salinity, turbidity, and SiO3-Si in the second principal component (PC2). Similarly, the scores of stations in the bottom layers in PC1 were related to PO4-P, NO2-N, NO3-N, and TP, while salinity, Chlorophyll a, NH4-N, and SiO3-Si in PC2. Results of the PCA identified the spatial distribution of the surface and bottom water quality, namely the Guangzhou urban reach, Middle reach, and Lower reach of the estuary. Both cluster analysis and PCA produced the similar results. Self-organizing map delineated the Guangzhou urban reach of the Pearl River that was mainly influenced by human activities. The middle and lower reaches of the PRE were mainly influenced by the waters in the South China Sea. The information extracted by PCA, CA, and SOM would be very useful to regional agencies in developing a strategy to carry out scientific plans for resource use based on marine system functions.

The coastal ecosystem in the Daya Bay is sensitive to the environmental changes induced by highly intensive human activities. We obtained and compiled the recent 30 years' field observational data on nutrients and phytoplankton communities to explore the changing ecosystem. Dissolved inorganic nitrogen concentration (DIN) has significantly increased, while phosphate concentration (DIP) dramatically decreased because of costal anthropogenic influence. The limited factors for phytoplankton have changed from nitrogen in the 1980s to phosphate in the mid-1990s. The net-collected phytoplankton communities has the miniaturized trend, while there is drastic increase of Chlorophyll a (Chl- a ) concentration. Even though the diatoms still dominate in phytoplankton community, the dominant species have slightly changed. The alga bloom greatly changed from diatoms dominated to dinoflagellates due to changes of nutrient structure. All these changes on nutrients and phytoplankton communities appear to be closely associated with human activities along the coast of the Daya Bay.

Coastal water quality and trophic status are subject to intensive environmental stress induced by human activities and climate change. Quarterly cruises were conducted to identify environmental characteristics in Daya Bay in 2013. Water quality is spatially and temporally dynamic in the bay. Cluster analysis (CA) groups 12 monitoring stations into two clusters. Cluster I consists of stations (S1, S2, S4-S7, S9, and S12) located in the central, eastern, and southern parts of the bay, representing less polluted regions. Cluster II includes stations (S3, S8, S10, and S11) located in the western and northern parts of the bay, indicating the highly polluted regions receiving a high amount of wastewater and freshwater discharge. Principal component analysis (PCA) identified that water quality experience seasonal change (summer, winter, and spring-autumn seasons) because of two monsoons in the study area. Eutrophication in the bay is graded as high by Assessment of Estuarine Trophic Status (ASSETS).

Upwelling is one of the most important processes in the marine ecosystem and plays an important role in nutrient transport. However, the bacterial community structure and function of upwelling areas in the South China Sea (SCS) have received little attention. This study provides a systematic insight into bacterial diversity and predicted metabolic functions related to upwelling areas using Illumina Miseq sequencing. The results suggest that bacterial communities exhibit different patterns of spatial distribution in different upwelling systems, and provides evidence for phylogenetic taxonomy shaped by ecological preferences. The bacterial community displayed a significant vertical gradient in upwelling systems. Oceanospirillales, Alteromonadales, Sphingomonadales, Flavobacteriales, Rhodobacterales, and Bacillales were dominant in areas of coastal upwelling, while Oceanospirillales, Alteromonadales, Rhodobacterales, and Lactobacillales were also abundant in areas of oceanic upwelling. Whereas, Lactobacillales, Pseudomonadales, and Alteromonadales were dominant in non-upwelling regions and displayed a uniform distribution among different depths. The predicted metagenome showed that functional metabolism shifts were consistent with taxon responses. Most of the gene families were significantly enriched and were more abundant in upwelling than non-upwelling regions, indicating that bacteria could increase their ability for metabolic exchange and nutrient transformation due to the upwelling effect. This study emphasized that upwelling induces a shift in the upwelling-driven microbe and metabolic functions, resulting in obvious impacts on material transformation.

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 A

The surface microlayer (SML) in marine systems is often characterized by an enrichment of biogenic, gel-like particles, such as the polysaccharide-containing transparent exopolymer particles (TEP) and the protein-containing Coomassie stainable particles (CSP). This study investigated the distribution of TEP and CSP, in the SML and underlying water, as well as their bio-physical controlling factors in Daya Bay, an area impacted by warm discharge from two Nuclear power plants (Npp's) and aquaculture during a research cruise in July 2014. The SML had higher proportions of cyanobacteria and of pico-size Chl a contrast to the underlayer water, particularly at the nearest outlet station characterized by higher temperature. Diatoms, dinoflagellates and chlorophyll a were depleted in the SML. Both CSP and TEP abundance and total area were enriched in the SML relative to the underlying water, with enrichment factors (EFs) of 1.5-3.4 for CSP numbers and 1.32-3.2 for TEP numbers. Although TEP and CSP showed highest concentration in the region where high productivity and high nutrient concertation were observed, EFs of gels and of dissolved organic carbon (DOC) and dissolved acidic polysaccharide (> 1 kDa), exhibited higher values near the outlet of the Npp's than in the adjacent waters. The positive relation between EF's of gels and temperature and the enrichment of cyanobacteria in the SML may be indicative of future conditions in a warmer ocean, suggesting potential effects on adjusting phytoplankton community, biogenic element cycling and air-sea exchange processes.

The Xisha Islands, located off Sanya, South China Sea, are a group of islands administered by Hainan Province of the People's Republic of China. Due to little human activity, they are well preserved. Such conditions suggest that changes in ecosystem are mostly related to natural behavior. A baseline of water quality was established in May and July, 2012. The results of multivariate analysis showed changes in nutrients as the most significant variable in describing water quality. Hydrologic heterogeneity showed little change, but temporal characteristics presented distinguishable variations. This information may be valuable for socioeconomic development and human health in Xisha island waters.

A subsurface nitrite maximum was observed along one transection near the Xisha Islands in the South China Sea in early September 2009. Possible causes were examined using in situ observed data and remote sensing data. A cold eddy was identified near the Xisha Islands during the periods of study. The Xisha Islands' water receives copious supplies of nutrients through cold eddies. Accumulation of nitrite about 50 m deep reaches 0.49 μmol l−1, and forms and maintains the primary nitrite maximum. The relationship between NO2− and Chl-a is very significant (R2 = 0.5829, p-value(statistical significance) = 0.00). Nitrification processes would result in apparent oxygen utilization (AOU) ranging from 0.22 to 35.88 μM, around 24.60% of the total biological oxygen demand in the water column of under-saturation of dissolved oxygen. This value is very close to the Redfield stoichiometry (32/138 = 23%) of total oxygen consumption associated with organic matter diagenesis. These results may support the hypothesis that phytoplankton and the nitrification process have an important influence on the PNM or 260 maintenance in the euphotic layer. Our results indicate that physical conditions and biological activities near the Xisha Islands play a significant role in regulating biogeochemistry.

In order to increase our understanding of the microbial diversity associated with seagrass Thalassia hemprichii in Xincun Bay, South China Sea, 16S rRNA gene was identified by highthrough sequencing method. Bacteria associated with seagrass T. hemprichii belonged to 37 phyla, 99 classes. The diversity of bacteria associated with seagrass was similar among the geographically linked coastal locations of Xincun Bay. Proteobacteria was the dominant bacteria and the α-proteobacteria had adapted to the seagrass ecological niche. As well, α-proteobacteria and Pseudomonadales were associated microflora in seagrass meadows, but the interaction between the bacteria and plant is needed to further research. Burkholderiales and Verrucomicrobiae indicated the influence of the bay from anthropogenic activities. Further, Cyanobacteria could imply the difference of the nutrient conditions in the sites. γ-proteobacteria, Desulfobacterales and Pirellulales played a role in the cycle of sulfur, organic mineralization and meadow ecosystem, respectively. In addition, the less abundance bacteria species have key functions in the seagrass meadows, but there is lack knowledge of the interaction of the seagrass and less abundance bacteria species. Microbial communities can response to surroundings and play key functions in the biochemical cycle.

Heat shock protein 70 (HSP70), the primary member of the HSPs that play various stress-protective roles in plants. In this study, a hsp70 gene of Kandelia obovata (KoHsp70) was cloned by rapid amplification of cDNA ends (RACE). The full-length of KoHsp70 was 2255 bp, consisting of a 5'-terminal untranslated region (UTR) of 118 bp, a 3'-terminal UTR of 178 bp, and an open reading frame (ORF) of 1959 bp. The ORF (KoHSP70) was predicted to encode a polypeptide of 652 amino acids with a theoretical molecular weight (MW) of 71.40 kDa and a pI of 5.16. The amino acid sequence analysis revealed that the KoHSP70 contained three conserved regions of HSP70 family, a bipartite nuclear localization signal sequences (NLS), an ATP/GTP-binding site motif and a cytoplasmic characteristic motif (EEVD). Homology analysis indicated that KoHSP70 shared 96.0 % identity with the known HSP70 (Gossypium hirsutum). Bioinformatics analysis indicated that the KoHSP70 was hydrophilic and had no signal peptide or transmembrane region. The mRNA expression of KoHsp70 kept relatively stable at first and then increased significantly after 48 h cold stress, and reached the highest level at 168 h after cold treatment. The results indicated that the KoHsp70 was a stress-inducible gene that might play a role in cold stress-protective response and in coping with environmental and biological stresses for K. obovata. This study provided a basis to further study the mechanism of anti-adverseness and expression characteristics under stress conditions of K. obovata.