Habitat- and lifestyle-dependent structural and functional characteristics of viruses in mangrove wetlands of different functional zonings.

Mangrove wetlands, as one of the natural ecosystems with the most ecological services, have garnered widespread attention about their microbial driven biogeochemical cycling. Urbanization have led to different spatial patterns of environmental conditions and microbial communities in mangroves. However, viruses, as the pivotal drivers of biogeochemical cycling in mangroves, remain inadequately explored in terms of how their ecological potential and complex interactions with host respond to functional zonings. To address this knowledge gap, we conducted a comprehensive investigation on the structural and functional properties of temperate and lytic viruses in mangrove wetlands from different functional zonings by jointly using high-throughput sequencing, prokaryotic and viral metagenomics. Multiple environmental factors were found to significantly influence the taxonomic and functional composition, as well as lysogen-lysis decision-making of mangrove viruses. Furthermore, enriched auxiliary metabolic genes (AMGs) involved in methane, nitrogen and sulfur metabolism, and heavy metal resistance were unveiled in mangrove viruses, whose community composition was closely related to lifestyle and host. The virus-host pairs with different lifestyles were also discovered to react to environmental changes in different ways, which provided an empirical evidence for how virus and bacteria dynamics were specific to viral lifestyles in nature. This study expands our comprehension of the intricate interactions among virus, prokaryotic host and the environment in mangrove wetlands from multiple perspectives, including viral lifestyles, virus-host interactions, and habitat dependence. Importantly, it provides a new ecological perspective on how mangrove viruses are adapted to the stress posed by urbanization.

Isolation and genomics of ten novel Shewanella species from mangrove wetland.

Mangrove bacteria largely compose the microbial community of the coastal ecosystem and are directly associated with nutrient cycling. In the present study, 12 Gram-negative and motile strains were isolated from a mangrove wetland in Zhangzhou, China. Pairwise comparisons (based on 16S rRNA gene sequences) and phylogenetic analysis indicated that these 12 strains belong to the genus Shewanella. The 16S rRNA gene sequence similarities among the 12 Shewanella strains and their related type strains ranged from 98.8 to 99.8 %, but they still could not be considered as known species. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between the 12 strains and their related type strains were below the cut-off values (ANI 95-96% and dDDH 70 %) for prokaryotic species delineation. The DNA G+C contents of the present study strains ranged from 44.4 to 53.8 %. The predominant menaquinone present in all strains was MK-7. The present study strains (except FJAT-53532T) also contained ubiquinones (Q-8 and Q-7). The polar lipid phosphatidylglycerol and fatty acid iso-C15 : 0 was noticed in all strains. Based on phenotypic, chemotaxonomic, phylogenetic and genomic comparisons, we propose that these 12 strains represent 10 novel species within the genus Shewanella, with the names Shewanella psychrotolerans sp. nov. (FJAT-53749T=GDMCC 1.2398T=KCTC 82649T), Shewanella zhangzhouensis sp. nov. (FJAT-52072T=MCCC 1K05363T=KCTC 82447T), Shewanella rhizosphaerae sp. nov. (FJAT-53764T=GDMCC 1.2349T=KCTC 82648T), Shewanella mesophila sp. nov. (FJAT-53870T=GDMCC 1.2346T= KCTC 82640T), Shewanella halotolerans sp. nov. (FJAT-53555T=GDMCC 1.2344T=KCTC 82645T), Shewanella aegiceratis sp. nov. (FJAT-53532T=GDMCC 1.2343T=KCTC 82644T), Shewanella alkalitolerans sp. nov. (FJAT-54031T=GDMCC 1.2347T=KCTC 82642T), Shewanella spartinae sp. nov. (FJAT-53681T=GDMCC 1.2345T=KCTC 82641T), Shewanella acanthi sp. nov. (FJAT-51860T=GDMCC 1.2342T=KCTC 82650T) and Shewanella mangrovisoli sp. nov. (FJAT-51754T=GDMCC 1.2341T= KCTC 82647T).

A baseline study of polycyclic aromatic hydrocarbons distribution, source and ecological risk in Zhanjiang mangrove wetlands, South China.

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants and pose a severe threat to human health. Here, 38 surface sediment samples collected from the Gaoqiao mangrove wetland in Zhanjiang, south China, were analyzed to determine 16 Environmental Protection Agency (EPA) priority PAHs. Total PAHs concentrations ranged from 33.5 µg/kg to 404.8 µg/kg with an average of 147.7 ± 77.7 µg/kg, inferring a moderate pollution level. Three and four-ring compounds dominated the PAHs composition patterns. Significant positive correlations were observed between the PAHs and the physicochemical properties of the sediments. According to the characteristic molecular ratio method, PAHs in sediments were mainly derived from combustion sources, including the incomplete combustion of liquid fossil fuels, grass, wood, and coal. The result based on the PMF model indicates that the primary combustion sources of PAHs are coal combustion, diesel-powered vehicles, biomass combustion and gasoline-powered vehicles, with a share of 39.01%, 25.21%, 12.72% and 10.48%, respectively. The petrogenic source contributes 12.58% PAHs to the sediments. The mean effects range median quotient (m-ERM-Q) and toxic equivalent method (TEQ) indicate a low comprehensive ecological risk of PAHs in the study area. Still, the evaluation results of effects range low (ERL) suggest that PAHs in the sediment would occasionally have adverse biological effects. Therefore, this situation demands attention and calls for protection strategies in the processes of urbanization and industrialization in south China.

Isolation of Thalassobius mangrovi sp. nov., a novel bacterium in the family Rhodobacteraceae, from marine mangrove sediment.

A Gram-stain-negative, strictly aerobic and oval-shaped bacterial strain with a flagellum, designated GS-10T, was isolated from mangrove wetland sediment. GS-10T grew at 20-40 °C (optimum, 37 °C), in the pH range of 5.0-11.0 (optimum, 6.0-8.0) and under various NaCl concentrations from 1 to 11 % (w/v) (optimum, 5-6 %). The respiratory quinone was ubiquinone-10, and the predominant polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The major fatty acids (>10 % of the total fatty acids) were summed feature 4 (C17 : 1iso I/anteiso B) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The G+C content of the genomic DNA was 63.71 %. On the basis of the results from comparative analysis of the 16S rRNA gene sequence, GS-10T represents a member of the family Rhodobacteraceae and had the highest sequence similarity to Thalassobius gelatinovorus CECT 4357T (97.47 %), followed by Lutimaribacter pacificus W11-2BT (97.03 %), Marivita cryptomonadis CL-SK44T (96.83 %), Thalassobius autumnalis CECT 5118T (96.75 %) and Thalassobius mediterraneus CECT 5383T (96.68 %). Phylogenetic trees based on 16S rRNA gene sequences, multilocus sequence analysis (MLSA) and whole genome sequences revealed that GS-10T clustered with species within the genus Thalassobius. The average nucleotide identity (ANI) and the average amino acid identity (AAI) values were calculated from complete genome sequences and indicated that GS-10T represented a novel species of the genus Thalassobius, and the name Thalassobius mangrovi sp. nov. is proposed for this species. The type strain of Thalassobius mangrovi is GS-10T (=MCCC 1K03624T=KCTC 82131T).

Streptomyces qinzhouensis sp. nov., a mangrove soil actinobacterium.

A novel Streptomyces strain (SSL-25T) was isolated from mangrove soil sampled at QinzhouBay, PR China. The isolate was observed to be Gram-stain-positive and to form greyish-white aerial mycelia that differentiated into straight spore chains with smooth-surfaced spores on International Streptomyces Project 2 medium. The cell-wall peptidoglycan was determined to contain ll-diaminopimelicacid. The cell-wall sugars were glucose and mannose. The predominant menaquinones were MK-9 (H6), MK-9 (H8) and MK-9 (H4). The major polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and several unidentified phospholipids. The predominant cellular fatty acids were C16:0, iso-C16:0 and summed feature 3 (C16:1ω7c/C16:1ω6c). The genome size of strain SSL-25T was 8.1 Mbp with a G+C content of 71.5 mol%. Phylogenetic analysis indicated that strain SSL-25T is closely related to Streptomyces tsukubensis NRRL 18488T (99.4 % sequence similarity). However, the digital DNA-DNA hybridization (39.8 %) and average nucleotide identity (91.3 %) values between them showed that it represents a distinct species. Furthermore, the results of morphological, physiological and biochemical tests allowed further phenotypic differentiation of strain SSL-25T from S. tsukubensis NRRL 18488T. Therefore, based on these results, it is concluded that strain SSL-25T represents a novel Streptomyces species, for which the name Streptomyces qinzhouensis sp. nov. is proposed. The type strain is SSL-25T (=CICC 11054T=JCM33585T).

Marisediminitalea mangrovi gen. nov., sp. nov., isolated from marine mangrove sediment, and reclassification of Aestuariibacter aggregatus as Marisediminitalea aggregata comb. nov.

Strain GS-14T was isolated from a mangrove sediment sample collected at Beilun Estuary National Nature Reserve, Guangxi Province, PR China. Cells were Gram-stain-negative, strictly aerobic and rod-shaped with a polar flagellum. Optimal growth occurred in the presence of 3-6 % (w/v) NaCl, at pH 6-8 and at a temperature of 37 °C. The predominant polar lipids were phosphatidylglycerol and phosphatidylethanolamine. Ubiquinone 8 (Q-8) was the sole respiratory quinone. The major fatty acids (>10 % of the total fatty acids) were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The DNA G+C content was 47.6 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain GS-14T had the highest sequence similarity to Aestuariibacter aggregatus WH169T (96.63 %), Aliiglaciecola coringensis AK49T (96.56 %) and Alteromonas lipolytica JW12T (96.22 %). In addition, the OrthoANIu value and dDDH values calculated from the genomes of strain GS-14T and A. aggregatus WH169T were 79.5 and 21.9 %, respectively. Based on the polyphasic taxonomic results, strain GS-14T is considered to represent a novel species in a new genus, for which the name Marisediminitalea mangrovi gen. nov., sp. nov. is proposed. The type strain of Marisediminitalea mangrovi is GS-14T (=KCTC 72401T=MCCC 1K03622T). Because Aestuariibacter aggregatus WH169T clustered with strain GS-14T in the phylogenetic trees and was clearly separated from the two species within the genus Aestuariibacter, it is reclassified as a member of the genus Marisediminitalea as Marisediminitalea aggregata comb. nov. (type strain WH169T=CGMCC 1.8995T=LMG 25283T). The type species of the genus Marisediminitalea is Marisediminitalea aggregata gen. nov., comb. nov.

Thalassotalea mangrovi sp. nov., a bacterium isolated from marine mangrove sediment.

A novel Gram-stain-negative, strictly aerobic bacterium that has a rod-like shape with a single polar flagellum in the exponential phase of growth and a spherical or ovoid shape without a flagellum in the stationary phase was isolated from a mangrove wetland sediment sample collected at Beilun Estuary National Nature Reserve, Guangxi Province, PR China and designated strain ZS-4T. This strain grew optimally at pH 6.0-8.0, at a temperature of 37 °C and in the presence of 3-4 % (w/v) NaCl. Its polar lipid profile included phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid and two uncharacterized lipids. Ubiquinone 8 (Q-8) was the sole respiratory quinone and the cellular fatty acids were dominated by C17 : 1ω8c and C16 : 0. A phylogenetic analysis based on the 16S rRNA gene sequence showed that strain ZS-4T exhibited its highest similarities to the type strains Thalassotalea litorea HMF4135T (97.8 %) and Thalassotalea ponticola GJSW-36T (95.9 %). A whole genome-level comparison of strain ZS-4T with T. litorea MCCC 1K03283T revealed an average nucleotide identity value of 75.6 % and a calculated DNA-DNA hybridization value of 19.6 %. In addition, the genomic DNA G+C content of strain ZS-4T was 45.9 mol%. Thus, based on analyses of its morphology, physiology, fatty acid composition and 16S rRNA gene sequence, strain ZS-4T should be considered a novel species of the genus Thalassotalea, with the proposed name Thalassotaleamangrovi sp. nov. The type strain is ZS-4T (=KCTC 72399T=MCCC 1K03630T).

Morphology and Phylogeny of Four New Vorticella Species (Ciliophora: Peritrichia) from Coastal Waters of Southern China.

Four new species of Vorticella, V. parachiangi sp. n., V. scapiformis sp. n., V. sphaeroidalis sp. n., and V. paralima sp. n., were isolated from coastal brackish waters of southern China. Their morphology, infraciliature, and silverline system were investigated based on observations of specimens both in vivo and following silver staining. Vorticella parachiangi sp. n. is distinguished by: a J-shaped macronucleus; a single dorsally located contractile vacuole; a two-rowed infundibular polykinetid 3, in which row 1 is shorter than row 2; 21-31 silverlines between peristome and aboral trochal band, 6-11 between aboral trochal band and scopula. Vorticella scapiformis sp. n. is characterized by its conspicuously thin and irregularly edged peristomial lip; a J-shaped macronucleus; a single, ventrally located contractile vacuole; row 1 of the infundibular polykinetid 3 proximally shortened; 18-25 silverlines between peristome and aboral trochal band, 8-12 between aboral trochal band and scopula. Vorticella sphaeroidalis sp. n. can be identified by its small, sub-spherical zooid; a C-shaped macronucleus; a ventrally located contractile vacuole; an aboral trochal band adjacent to the scopula; 16-18 silverlines between persitome and aboral trochal band, two between aboral trochal band and scopula. Vorticella paralima sp. n. can be identified by its ovoidal zooid; a J-shaped macronucleus; a dorsally positioned contractile vacuole; rows 1 and 2 of the infundibular polykinetid 3 proximally shortened; 26-35 silverlines from peristome to aboral trochal band, and 7-13 from aboral trochal band to scopula. The SSU rDNA genes of these four species were sequenced and their phylogeny was analyzed.

Vertical Distribution of Bathyarchaeotal Communities in Mangrove Wetlands Suggests Distinct Niche Preference of Bathyarchaeota Subgroup 6.

Bathyarchaeota is a diverse, abundant, and widespread archaeal phylum that may play an important role in global carbon cycling. The vertical distribution of Bathyarchaeota and environmental impact on bathyarchaeotal community in deep-sea and lake sediments are known; however, little information is available on Bathyarchaeota in eutrophic and brackish environments, such as mangrove wetlands. In the current study, we investigated the bathyarchaeotal community in the mangrove ecosystem of Futian Nature Reserve, Shenzhen. By slicing the profile into 2-cm layers from the surface to bottom, 110 sediment samples were obtained from three mangrove and three mud flat profiles. High-throughput sequencing of archaeal 16S rRNA genes, quantification of bathyarchaeotal 16S rRNA genes with optimized quantitative primers, and the ensuing statistical analyses revealed the vertical distribution of Bathyarchaeota in the mangrove ecosystem, indicating that Bathyarchaeota was the dominant archaeal phylum therein, with Bathyarchaeota subgroups 6, 8, 15, and 17 as the most abundant subgroups. The abundance of Bathyarchaeota was higher in the mangrove than in the mud flat and other oligotrophic or freshwater habitats. Total organic carbon (TOC) and nitric oxide were significantly correlated with the abundance of Bathyarchaeota, and pH was the major factor shaping the community composition. Further, the data suggested that Bathyarchaeota subgroup 6 preferentially dwelled in slightly acidic, high TOC, and subsurface environments, indicating a potentially distinct role in the global geochemical cycle. These findings expand the knowledge of the distribution and niche preference of Bathyarchaeota, emphasizing the need for continuous characterization of bathyarchaeotal subgroups.

Halogenated organic pollutants in sediments and organisms from mangrove wetlands of the Jiulong River Estuary, South China.

Eighteen sediments and four biota species were collected from mangrove wetlands of the Jiulong River Estuary (JRE) in South China to investigate the distribution of dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), dechlorane plus (DP) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE). Concentrations of ΣDDTs, ΣPCBs, ΣPBDEs, DBDPE, DP, and BTBPE in mangrove sediments ranged from 21 to 84, 0.52-2.5, 9.0-66, 5.1-32, 0.05-0.14, and 0.03-0.25 ng/g dry weight, respectively. Levels of ΣDDTs, ΣPCBs, ΣPBDEs, DBDPE and DP in mangrove biota ranged from 950 to 30000, 56-400, 8.0-35, nd-20 and 0.44-3.1 ng/g lipid weight, respectively. DDTs were the predominant halogenated organic pollutants (HOPs) in mangrove sediments from the JRE, while PBDEs were the major HOPs in mangrove sediments from the Pearl River Estuary (PRE), suggesting that sediments in JRE and PRE had different sources of HOPs. The dominance of DDTs was found in both mangrove sediments and biota from the JRE, indicating that HOPs in JRE environment mainly come from agricultural sources. The biota-sediment accumulation factors for DDTs and PCBs were significantly higher than those of PBDEs, DBDPE and DP, suggesting high bioavailability of DDTs and PCBs in mangrove biota. Trophic magnification factors for DDTs, PCBs, PBDEs, and DP were 10.5, 3.00, 2.66 and 1.23, respectively, indicating their potential of biomagnification in mangrove food webs.

Molecular and stable isotopic evidence for the occurrence of nitrite-dependent anaerobic methane-oxidizing bacteria in the mangrove sediment of Zhangjiang Estuary, China.

Nitrite-dependent anaerobic methane oxidation (n-damo), which is mediated by "Candidatus Methylomirabilis oxyfera-like" bacteria, is unique in linking the carbon and nitrogen cycles. However, the niche and activity of n-damo bacteria in the mangrove ecosystem have not been confirmed. Here, we report the occurrence of the n-damo process in the mangrove wetland of the Zhangjiang Estuary, China. The widespread occurrence of n-damo bacteria in mangrove wetland was confirmed using real-time quantitative polymerase chain reaction (qPCR) assay, which showed that the abundance of Methylomirabilis oxyfera-like bacterial 16S rRNA and pmoA genes ranged from 2.43 × 106 to 2.09 × 107 and 2.07 × 106 to 3.38 × 107copies per gram of dry soil in the examined sediment cores. The highest amount of targeting genes was all detected in the upper layer (0-20 cm). Phylogenetic analyses of n-damo bacterial 16S rRNA and pmoA genes illustrated the depth-specific distribution and high diversity of n-damo bacteria in the mangrove wetland. Stable isotope experiments further confirmed the occurrence of n-damo in the examined mangrove sediments, and the potential n-damo rates ranged from 25.93 to 704.08 nmol CO2 per gram of dry soil per day at different depths of the sediment cores, with the n-damo being more active in the upper layer of the mangrove sediments. These results illustrate the existence of active M. oxyfera-like bacteria and indicate that the n-damo process is a previously overlooked microbial methane sink in the mangrove wetlands.

Anthropogenic protection alters the microbiome in intertidal mangrove wetlands in Hainan Island.

Intertidal mangrove wetlands are of great economic and ecological importance. The regular influence of tides has led to the microbial communities in these wetlands differing significantly from those in other habitats. In this study, we investigated the microbiomes of the two largest mangrove wetlands in Hainan Island, China, which have different levels of anthropogenic protection. Soil samples were collected from the root zone of 13 mangrove species. The microbial composition, including key functional groups, was assessed using Illumina sequencing. Bioinformatics analysis showed that there was a significant difference in the microbiomes between the protected Bamen Bay and the unprotected Dongzhai Bay. The overall microbiome was assigned into 78 phyla and Proteobacteria was the most abundant phylum at both sites. In the protected wetland, there were fewer marine-related microbial communities, such as sulfate-reducing bacteria, and more terrestrial-related communities, such as Verrucomicrobia methanotrophs. We also observed distinct microbial compositions among the different mangrove species at the protected site. Our data suggest that the different microbiomes of the two mangrove wetlands are the result of a complex interaction of the different environmental variables at the two sites.

Partitioning of PAHs in pore water from mangrove wetlands in Shantou, China.

To investigate the trend of selected polycyclic aromatic hydrocarbons (PAHs) partitioning, fifteen pore water samples collected from the sediments of three mangrove wetlands were analyzed, and the partition coefficients and the partition model for the PAHs were determined by the correlation between K(oc) and octanol-water partition coefficient (K(ow)). The results revealed that the mean Kp values in inner mangrove wetlands were between 143 and 1031 L /Kg; the particulate organic carbon (POC) could strongly adsorb low-ring PAHs; the PAHs partitioning was on a obvious trend transported to particle phase. We suggest that the classic equilibrium model of organic carbon normalized (K(p)=K(oc)f(oc)) may be used to predict the trend of the selected PAHs partitioning.

The morphology of three Loxophyllum species (Ciliophora, Pleurostomatida) from southern China, L. lembum sp. n., L. vesiculosum sp. n. and L. perihoplophorum Buddenbrock, 1920, with notes on the molecular phylogeny of Loxophyllum.

Two new pleurostomatid ciliates, Loxophyllum lembum sp. n., L. vesiculosum sp. n., and the poorly known L. perihoplophorum Buddenbrock, 1920, isolated from brackish waters in coastal regions of southern China, are described following observations of live cells and protargol-impregnated specimens. Loxophyllum lembum sp. n. is distinguished by a combination of characters including two macronuclear nodules, 6-9 contractile vacuoles along the ventral margin, 11-14 right and 6-8 left kineties and the presence of cortical granules. Loxophyllum vesiculosum sp. n. differs from its congeners mainly by the unique distribution of contractile vacuoles, several of which lie along the dorsal margin and one on the ventral margin, and 15-21 right and 6-8 left kineties. Loxophyllum perihoplophorum is characterized by its large cell size (350-450 µm long in vivo), 3-5 contractile vacuoles along the dorsal margin in the posterior region of the body, and 19-23 right and 7-9 left kineties. An improved diagnosis of L. perihoplophorum is provided. The SSU rDNA sequence of L. perihoplophorum is reported for the first time and its molecular phylogeny is analyzed. Maximum likelihood and Bayesian inference analyses of SSU rDNA sequence data recover the monophyly both of the order Pleurostomatida and of the genus Loxophyllum.

Integrated effects of bioturbation, warming and sea-level rise on mobility of sulfide and metalloids in sediment porewater of mangrove wetlands.

Global warming and sea-level rise exert profound impacts on coastal mangrove ecosystems, where widespread benthic crabs change sediment properties and regulate material cycles. How crab bioturbation perturbs the mobilities of bioavailable arsenic (As), antimony (Sb) and sulfide in sediment-water systems and their variability in response to temperature and sea-level rise is still unknown. By combining field monitoring and laboratory experiments, we found that As was mobilized under sulfidic conditions while Sb was mobilized under oxic conditions in mangrove sediments. Crab burrowing greatly enhanced oxidizing conditions, resulting in enhanced Sb mobilization and release but As sequestration by iron/manganese oxides. In control experiments with non-bioturbation, the more sulfidic conditions triggered the contrasting situation of As remobilization and release but Sb precipitation and burial. Moreover, the bioturbated sediments were highly heterogeneous for spatial distributions of labile sulfide, As and Sb as presented by 2-D high-resolution imaging and Moran's Index (patchy at the <1 cm scale). Warming stimulated stronger burrowing activities, which led to more oxic conditions and further Sb mobilization and As sequestration, whilst sea-level rise did the opposite via suppressing crab burrowing activity. This work highlights that global climate changes have the potential to significantly alter element cycles in coastal mangrove wetlands by regulating benthic bioturbation and redox chemistry.

Variation of glomalin-metal binding capacity in 1 m soil profiles from mangrove forests to mudflat and affected factor analysis.

Glomalin-related soil protein (GRSP) plays an important role in soil metal sequestration in coastal wetlands. Additionally, it can release dissolved organic matter (GDOM) in water-soaked condition. The purpose of this study was to clarify the variation of GRSP's heavy metal immobilisation capacity at soil profiles of coastal wetland, and explore the compositional characteristics of GDOM and its influence on the heavy metals' environmental behaviour. The results indicated that the metal immobilisation capacity of GRSP decreased with increasing burial depth. The contributions of GRSP to soil Cr, As, and Pb were higher in both mangrove soils (K. obovata and A. marina forests) than in the mudflat. Oxygen-containing functional groups of GRSP (CO, -COO-, etc.) played a positive role in heavy metals accumulation. Redundancy analysis (RDA) showed that high soil pH was not conducive to the enrichment of heavy metals by GRSP. Besides, the concentrations of GRSP-Fe showed a significant positive correlation with the concentrations of other metals (Cu, As, and Pb) in GRSP. It is speculated that the Fe minerals in GRSP contributed the enrichment of heavy metals. Based on PARAFAC modelling, four fluorescent components of GDOM were identified, including three humic-like fluorescent components and one tyrosine-like fluorescent component. The contributions of GDOM to GRSP-bound heavy metals fluctuated between 4.05 % and 88.80 %, which could enhance the fluidity of heavy metals in water and weaken the soil heavy metal immobilisation capacity of GRSP. High salinity exerted an inhibitory effect on the heavy metal content of the GDOM. This study comprehensively explored the potential of GRSP to immobilise heavy metals in wetland soils and highlighted the potential heavy metal risks associated with the GDOM component in water, which could contribute to the multidimensional assessment and control of heavy metal pollution in coastal wetlands.

Sediment mercury concentration of a subtropical mangrove wetland responded to Hong Kong-Shenzhen industrial development since the 1960s.

Mercury (Hg) in coastal wetlands is of great concern due to its acute toxicity. We measured the total Hg content (THg) from a 210Pb-dated sediment core obtained from the Futian mangrove wetland in Shenzhen Bay, South China to explore the historical variation and possible sources. Our results extend the sediment THg record back to 1960 and reveal three distinct intervals. Interval I (1960-1974) has low and increasing THg values, averaging 83.0 µg/kg; Interval II (1975-1984) witnesses a remarkably increase, peaking in 1980 (261.6 µg/kg) then remaining elevated; Interval III (1985-2014) shows a steady reduction, averaging 118.4 µg/kg. The good correlation among THg, TOC, and Hg/TOC, and the downstream decrease in monitoring sediment THg consistently suggest that the bulk THg are mainly sourced from the Shenzhen River discharge. The different timing in industrial development attributes the elevated THg concentrations during 1975-1984 to Hong Kong industrial sewage pollution.

Key factors influencing pollution of heavy metals and phenolic compounds in mangrove sediments, South China.

Concentrations of heavy metals (HMs) and phenolic compounds with factors which potentially affected their spatial distribution were investigated in mangrove sediments, South China. Compared to Qi'ao, Futian sediments exhibited higher levels of Pb and nonylphenol (NP), but lower levels of Co and Ni. Seasonal variation showed higher concentrations of Pb, Cr, Co, NP and bisphenol A (BPA), while lower concentration of methylparaben (MP) in wet than dry season. Contaminant levels in sediments collected at different tidal heights showed insignificant variations, except for Zn and NP. MP was found negatively correlated with nearly all HMs and BPA, whereas the latter exhibited positive correlations with each other. Sedimentary total carbon, total nitrogen, C/N and N/P ratios were screened as the most influential factors affecting the distribution of these contaminants. Additionally, both salinity and total phosphate exhibited positive, while both pH and sedimentary particle size registered negative correlation, with one or more contaminants.

Spatial distribution of potentially harmful trace elements and ecological risk assessment in Zhanjiang mangrove wetland, South China.

Global mangrove wetlands face increasing anthropogenic impacts along the coast. The Zhanjiang mangrove wetland is the largest and adjacent to the most developed bay area in China. Surface sediments were collected in different plant transit and used for potentially harmful trace elements (PHTEs) measurement. Mean contents of Hg, Cr, Ni, Cu, Zn, As, Cd and Pb were 0.01 mg/kg, 56.16 mg/kg, 10.06 mg/kg, 9.61 mg/kg, 43.58 mg/kg, 8.76 mg/kg, 0.25 mg/kg, 28.12 mg/kg. Most of the PHTEs were slightly enriched but the Cd pollution is significant, and the potential ecological risk is moderate. The risk of the mangrove wetland is larger than the grassland and the farmland. The PCA and PMF indicate Hg, Ni, Cu, Zn, As, and Pb mainly originated from local anthropogenic activities, Cr originated from the natural geological process, and Cd mainly originated from atmospheric deposition of regional industrial pollution. In view of the impact of surrounding industry and agriculture and the signs of PHTEs pollution, it is necessary to implement the wetland protection law more strictly to truly realize the construction of ecological civilization. This provides a valid reference for the wetland conservation and management in coastal cities.

Influence of bacterial community diversity, functionality, and soil factors on polycyclic aromatic hydrocarbons under various vegetation types in mangrove wetlands.

Polycyclic aromatic hydrocarbons (PAHs) are prevalent organic pollutants in coastal ecosystems, particularly in mangrove wetlands. However, it is still largely unclear how PAHs affect the soil bacterial community under various vegetation types in the Greater Bay Area. Here, we selected soil samples from four sites with different vegetation types (native mangrove forest dominated by Kandelia candel, invasive mangrove forest dominated by Sonneratia apetala, unvegetated mudflat, and riverine runoff outlet) in the Qi'ao and Futian Nature Reserves. We investigated the effects of PAHs on soil bacterial community composition and diversity, function, and co-occurrence via 16S rRNA high-throughput sequencing. PAHs obviously reduced soil bacterial community diversity and richness. Based on PICRUSt 2, PAHs demonstrated positive influences on PAHs degradation metabolism related bacterial genes. Meanwhile, we predicted that riverine runoff outlets can potentially degrade PAHs, may donate to sustain healthy mangrove ecosystem. Also, PAHs and total nitrogen (TN) were crucial factors driving the soil bacterial community in Qi'ao sites, whereas in the Futian sites, PAHs and SOC were more important. PAHs, SOC and TN showed negative effects on specific bacteria abundance. Subsequently, environmental factors and PAHs levels influenced the soil bacterial ecological functions community. Co-occurrence network analysis revealed non-random assembly patterns of the bacterial communities. SBR1031 and A4b were the keystone genera and played a crucial role whgich played an irreplaceable role in PAHs degradation in Qi'ao and Futian sites. PAHs inhibited specific microbial activity and metabolism in native mangrove forest, while affects positively to bacterial community in riverine runoff outlet which might profoundly affect the whole soil quality under various vegetation types. Overall, this study might identify existing health problems and provide insights for enhancing protection and utilization management for mangrove ecosystem in the Greater Bay Area.