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A deteriorated water quality is closely associated with disease outbreaks in aquaculture, where microorganisms play indispensable roles in improving water quality and aquatic animals’ health. Mangrove is known to be a natural water quality filter and microbiological buffer of pathogen and prebiotics. However, it is unclear how and to what extent Rhizophora apiculata plantation is of benefits to the gut microbiota and growth over mud crab (Scylla paramamosain) aging. To address these concerns, we explored the bacterial communities in mud crab gut and rearing water at 45, 114, and 132 days after incubation, roughly corresponding to juvenile, pre-adult, and adult stages of mud crab. Results showed that 1-year R. apiculata plantation slightly increased the body weight of mud crab and improved water quality to a certain extent. Both bacterioplankton and gut bacterial communities were highly temporal dynamic, while the two communities were significantly distinct (ANOSIM r = 0.90, P = 0.0001). Relative abundances of dominant taxa in water and gut significantly varied between the plantation and the control conditions over mud crab aging. R. apiculata plantation promoted the stability of gut microbiota, as evidenced by more diverse core species. Furthermore, R. apiculata plantation led to the dominance of Verrucomicrobiae species in water and probiotic Bacteroidetes and Lactobacillales taxa in gut. A structural equation model revealed that water variables directly constrained gut microbiota, which in turn affected the body weight of mud crab (r = 0.52, P < 0.001). In addition, functional pathways facilitating immunity and lipid metabolism significantly increased in mud crab gut under the plantation, while those involved in infectious diseases exhibited the opposing trend. These findings greatly expand our understanding of the R. apiculata plantation effects on water quality, gut microbiota, and growth feature of mud crab. Overall, R. apiculata plantation is beneficial for mud crab growth and health.Key Points• A short-term R. apiculata plantation could potentially improve water quality.• Bacterioplankton is more sensitive than mud crab gut microbiota in response to R. apiculata plantation.• R. apiculata plantation enhances mud crab resistance against pathogen invasion.• R. apiculata plantation alters mud crab gut microbiota, which in turn promotes their body weight.

Silver nanoparticles (AgNPs) have recently gained interest in the medical field because of their biological features. The present study aimed at screening Rhizophora apiculata secondary metabolites, quantifying their flavonoids and total phenolics content, green synthesis and characterization of R. apiculata silver nanoparticles. In addition, an assessment of in vitro cytotoxic, antioxidant, anti-inflammatory and wound healing activity of R. apiculata and its synthesized AgNPs was carried out. The powdered plant material (leaves) was subjected to Soxhlet extraction to obtain R. apiculata aqueous extract. The R. apiculata extract was used as a reducing agent in synthesizing AgNPs from silver nitrate. The synthesized AgNPs were characterized by UV-Vis, SEM-EDX, XRD, FTIR, particle size analyzer and zeta potential. Further aqueous leaf extract of R. apiculata and AgNPs was subjected for in vitro antioxidant, anti-inflammatory, wound healing and cytotoxic activity against A375 (Skin cancer), A549 (Lung cancer), and KB-3-1 (Oral cancer) cell lines. All experiments were repeated three times (n = 3), and the results were given as the mean ± SEM. The flavonoids and total phenolics content in R. apiculata extract were 44.18 ± 0.086 mg/g of quercetin and 53.24 ± 0.028 mg/g of gallic acid, respectively. SEM analysis revealed R. apiculata AgNPs with diameters ranging from 35 to 100 nm. XRD confirmed that the synthesized silver nanoparticles were crystalline in nature. The cytotoxicity cell viability assay revealed that the AgNPs were less toxic (IC50 105.5 µg/mL) compared to the R. apiculata extract (IC50 47.47 µg/mL) against the non-cancerous fibroblast L929 cell line. Antioxidant, anti-inflammatory, and cytotoxicity tests revealed that AgNPs had significantly more activity than the plant extract. The AgNPs inhibited protein denaturation by a mean percentage of 71.65%, which was equivalent to the standard anti-inflammatory medication diclofenac (94.24%). The AgNPs showed considerable cytotoxic effect, and the percentage of cell viability against skin cancer, lung cancer, and oral cancer cell lines was 31.84%, 56.09% and 22.59%, respectively. R. apiculata AgNPs demonstrated stronger cell migration and percentage of wound closure (82.79%) compared to the plant extract (75.23%). The overall results revealed that R. apiculata AgNPs exhibited potential antioxidant, anti-inflammatory, wound healing, and cytotoxic properties. In future, R. apiculata should be further explored to unmask its therapeutic potential and the mechanistic pathways of AgNPs should be studied in detail in in vivo animal models.

Mangrove endophytic fungi can produce impressive quantities of metabolites with promising antioxidant activities that may be useful to humans as novel physiological agents. In this study, we investigated the phylogenetic diversity and antioxidant potential of 46 fungal endophytes derived from the mangrove species Rhizophora stylosa and R. mucronata from the South China Sea. The fungal isolates were identified using a combination of morphological characteristics and phylogenetic analysis of the internal transcribed spacer (ITS) sequences. Seventeen genera belonging to 8 taxonomic orders of Ascomycota were discovered, specifically, Botryosphaeriales, Capnodiales, Diaporthales, Eurotiales, Glomerellales, Hypocreales, Pleosporales, and Xylariales. The most abundant fungal orders included Xylariales (35.49%) and Diaporthales (27.61%), which were predominantly represented by the culturable species Pestalotiopsis sp. (34.54%) and Diaporthe sp. (18.62%). The stems showed more frequent colonization and species diversity than the roots, leaves, hypocotyls, and flower tissues of the host plant. The antioxidant activities of all the isolated fungal extracts on four different culture media were assessed using improved 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) methods. A relatively high proportion (84.8%) of the isolates displayed antioxidant capacity (%RSA > 50%). Further research also provided the first evidence that HQD-6 could produce flufuran as a significant radical scavenger with IC50 values of 34.85±1.56 and 9.75±0.58 μg/mL, respectively. Our findings suggest that the utilization of a biotope such as that of the endophytic fungal community thriving on the mangrove plants R. stylosa and R. mucronata may be suitable for use as a sustainable resource for natural antioxidants.

Mangroves are plants that can tolerate salinity equivalent to that present in seawater. In the present study, we have attempted to isolate the genes upregulated at the early stage of salt stress response in Rhizophora apiculata Blume, a true mangrove, through suppression subtractive hybridization technique. Several genes were isolated, which were then classified to nine functional categories, viz. metabolism, protein degradation and folding, secondary metabolism, cell rescue and defence, transport facilitation, signal transduction, transcription and ranslation, photosynthesis and unclassified genes of unknown function. The expression patterns of 12 of the genes thus obtained were studied at 6, 12 and 24 h time points of salinity stress using real-time PCR. Most genes were found to be upregulated under salt stress and showed maximum upregulation at the 6 h time point. Two of the genes studied were downregulated after 6 h, implying that the pattern of gene expression varies with time of application of stress. The genes thus isolated may be used to confer the trait of salt tolerance to non-tolerant genotypes, which can ultimately prove beneficial for crop improvement programmes

Leaf litter and its breakdown products represent an important input of organic matter and nutrients to mangrove sediments and adjacent coastal ecosystems. It is commonly assumed that old-grown stands with mature trees contribute more to the permanent sediment organic matter pool than younger stands. However, neither are interspecific differences in leaf decay rates taken into account in this assumption nor is our understanding of the underlying mechanisms or drivers of differences in leaf chemistry sufficient. This study examines the influence of different plant species and ontogenetic stage on the microbial decay of mangrove leaf litter. A litterbag experiment was conducted in the Matang Mangrove Forest Reserve, Malaysia, to monitor leaf litter mass loss, and changes in leaf litter chemistry and microbial enzyme activity. Four mangrove species of different morphologies were selected, namely the trees Rhizophora apiculata and Bruguiera parviflora, the fern Acrostichum aureum and the shrub Acanthus ilicifolius. Decay rates of mangrove leaf litter decreased from A. ilicifolius to R. apiculata to B. parviflora to A. aureum. Leaf litter mass, total phenolic content, protein precipitation capacity and phenol oxidase activity were found to decline rapidly during the early stage of decay. Leaf litter from immature plants differed from that of mature plants in total phenolic content, phenolic signature, protein precipitating capacity and protease activity. For R. apiculata, but not of the other species, leaf litter from immature plants decayed faster than the litter of mature plants. The findings of this study advance our understanding of the organic matter dynamics in mangrove stands of different compositions and ages and will, thus, prove useful in mangrove forest management.

The ability of mangroves in taking up and storing heavy metal (HM) helps in reducing HM pollution. However, HMs likewise adversely affect the growth of mangroves. We assess the effects of the long-term soil HMs enrichment on the growth of Rhizophora apiculata forest in the Can Gio Mangrove Forest (Southern Vietnam) in different environmental conditions of soil salinity, ground elevation, and tree density based on a novel set of measured data. These data were analyzed and were used to calibrate and validate for a tree growth model with influencing factors salinity, elevation, tree density, and heavy metals content. Three scenario simulations were performed to predict the mangrove dynamics under different levels of heavy metal pollution in combined environmental conditions of salinity and elevation. Simulation results show the decline of total forest biomass from 1,750,000 tons (baseline scenario with no HM pollution) down to 850,000 tons and 350,000 tons for the current HM pollution and double HM pollution scenarios, respectively. Both data analysis and simulations have shown that although mangroves can assist in reducing HM pollution, the quality and health of this ecosystem will be severely affected if the environment is excessively polluted. In addition, a data-and-model driven management tool is devised for the sustainable management of the mangrove environmental resources.

The present study estimated plant biomass in mangrove forests of the Andaman Islands, India. The mean above-ground biomass was 469.20 ± 41.25 Mega-gram/ha (Mg ha−1), while the mean below-ground biomass was 166.78 ± 12.79 Mg ha−1. The total mean biomass of Andaman mangrove forest was 635.98 ± 12.79 Mg ha−1 and its corresponding vegetation carbon stock was 290.26 ± 24.75 Mg C ha−1. Among the 6 forest divisions, Little Andaman recorded the highest mean biomass per unit area (1,081.26 ± 424.67 Mg ha−1) and vegetation carbon stock (494.50 ± 194.56 Mg C ha−1) followed by Middle Andaman, North Andaman, Havelock, South Andaman and Baratang. Among the 25 mangrove species, Rhizophora apiculata was found to contribute the highest biomass (152.78 Mg ha−1) and vegetation carbon stock (69.58 Mg C ha−1) followed by Bruguiera gymnorhiza, and Rhizophora mucronata. High vegetation carbon stock in mangrove forests of the Andaman Island could be attributed to high structural complexity, high precipitation rate (> 300 cm year−1), and comparatively fewer anthropogenic disturbances in the mangrove forest of the Andaman Islands. However, the Andaman Islands are increasingly vulnerable to natural calamities, like sea-level rise and associated soil erosion and increasing frequency of tropical cyclones, which call for immediate attention on preserving the island mangroves to sustain its extraordinary carbon storage capacity.

 Liver plays a vital role in the elimination of xenobiotics that can induce hepatotoxicity in living organisms.Silver nanoparticles have evolved recently as an alternative in various industries and are used for their biomedical applications. is a least studied mangrove-based plant that has been used in the traditional medicine of Southeast Asia for its healing properties. It is a well-known fact that the generation of free radicals has been associated with oxidative stress.   Hence, in this study we used carbon tetrachloride as a hepatotoxin to induce liver damage. The protective effects of silver nanoparticles synthesized using   on hepatotoxin-induced liver damage in experimental mice were assessed.   The results of the assessment indicate that silver nanoparticles were effective in protecting the liver from damages induced by carbon tetrachloride.   Among existing literature, this is the first ever approach for hepatoprotective effect of nanoparticles derived using plant extract from mangrove ecosystem.

Matang Mangrove Forest Reserve (MMFR) in Peninsular Malaysia is under systematic management since 1902 and still considered as the best managed mangrove forest in the world. The present study on silvimetrics assessed the ongoing MMFR forest management, which includes a first thinning after 15 years, a second thinning after 20 years and clear-felling of 30-year old forest blocks, for its efficiency and productivity in comparison to natural mangroves. The estimated tree structural parameters (e.g. density, frequency) from three different-aged mangrove blocks of fifteen (MF15), twenty (MF20), and thirty (MF30) years old indicated that Bruguiera and Excoecaria spp. did not constitute a significant proportion of the vegetation (<5%), and hence the results focused majorly on Rhizophora apiculata. The density of R. apiculata at MF15, MF20 and MF30 was 4,331, 2,753 and 1,767 stems ha(-1), respectively. In relation to ongoing practices of the artificial thinnings at MMFR, the present study suggests that the first thinning could be made earlier to limit the loss of exploitable wood due to natural thinning. In fact, the initial density at MF15 was expected to drop down from 6,726 to 1,858 trees ha(-1) before the first thinning. Therefore the trees likely to qualify for natural thinning, though having a smaller stem diameter, should be exploited for domestic/commercial purposes at an earlier stage. The clear-felling block (MF30) with a maximum stem diameter of 30 cm was estimated to yield 372 t ha(-1) of the above-ground biomass and suggests that the mangrove management based on a 30-year rotation is appropriate for the MMFR. Since Matang is the only iconic site that practicing sustainable wood production, it could be an exemplary to other mangrove locations for their improved management.

Seedlings of two species of mangroves, Bruguiera gymnorrhiza and Rhizophora apiculata , were monitored for 8 years on the Pacific island of Kosrae, Federated States of Micronesia, to determine the effects of canopy cover and hydrogeomorphic zone on long-term survival and growth. Annual rainfall is high with little seasonality. Study plots with seedling subplots were in fringe, riverine, and interior hydrogeomorphic zones along four small rivers. The height of each seedling was measured each year and was designated each time as being under an open, partially closed, or closed canopy. Growth rates of both species were slow, and no seedling that was newly established during the study became a sapling (2 m). Many seedlings stopped growing for long periods of time. Bruguiera seedlings were more numerous than Rhizophora seedlings. They grew faster than Rhizophora seedlings except in riverine zones. Predicted growth rates of Bruguiera were fastest under an open canopy and slowest under a closed canopy, but Rhizophora was not affected by canopy status. Overall mortality rates for the two species were similar, averaging 36% year −1 . El-Niño-Southern Oscillation events did not affect growth or mortality but may have caused some defoliation.