Mangrove Avicennia Marina Research Articles

Carbohydrate accumulation patterns in mangrove and halophytic plant species under seasonal variation

This study investigates the impact of carbohydrate accumulation in mangrove and halophytic plants on their response to abiotic stress. Using soil analysis and FT-IR spectroscopy, key species (Sueda nudiflora, Aeluropus lagopoides, Avicennia marina) were examined for seasonal changes in sugar content (reducing sugars, total soluble sugars, starch). The elevated carbohydrate levels may serve as an indication of the plant’s ability to adapt to different environmental conditions throughout the year. This accumulation enables plants to adapt to variations in their environment, assuring their survival and functionality during periods of environmental fluctuation. Halophytic plants’ sugar content peaked during the monsoon, suggesting biotic adaptations. The mangrove Avicennia marina had year-round sugar levels. PCA and Hierarchical Cluster Analysis revealed sugar accumulation trends across species and seasons. Partial Least Squares (PLS) analysis revealed correlations between soil characteristics and sugar content, suggesting plant-microbe interactions. K-means clustering and correlation analysis of FT-IR data revealed sugar composition and resource allocation trade-offs. These findings shed light on the role of carbohydrate metabolism in enabling coastal plants to endure stress. Gaining insight into these mechanisms can enhance sustainable agriculture in challenging environments and shed light on plant adaptations to evolving environmental conditions, especially biotic interactions.

Trehalose along with ABA promotes the salt tolerance of Avicennia marina by regulating Na+ transport.

Mangroves grow in tropical/subtropical intertidal habitats with extremely high salt tolerance. Trehalose and trehalose-6-phosphate (T6P) have an alleviating function against abiotic stress. However, the roles of trehalose in the salt tolerance of salt-secreting mangrove Avicennia marina is not documented. Here, we found that trehalose was significantly accumulated in A. marina under salt treatment. Furthermore, exogenous trehalose can enhance salt tolerance by promoting the Na+ efflux from leaf salt gland and root to reduce the Na+ content in root and leaf. Subsequently, eighteen trehalose-6-phosphate synthase (AmTPS) and 11 trehalose-6-phosphate phosphatase (AmTPP) genes were identified from A. marina genome. Abscisic acid (ABA) responsive elements were predicted in AmTPS and AmTPP promoters by cis-acting elements analysis. We further identified AmTPS9A, as an important positive regulator, that increased the salt tolerance of AmTPS9A-overexpressing Arabidopsis thaliana by altering the expressions of ion transport genes and mediating Na+ efflux from the roots of transgenic A. thaliana under NaCl treatments. In addition, we also found that ABA could promote the accumulation of trehalose, and the application of exogenous trehalose significantly promoted the biosynthesis of ABA in both roots and leaves of A. marina. Ultimately, we confirmed that AmABF2 directly binds to the AmTPS9A promoter in vitro and in vivo. Taken together, we speculated that there was a positive feedback loop between trehalose and ABA in regulating the salt tolerance of A. marina. These findings provide new understanding to the salt tolerance of A. marina in adapting to high saline environment at trehalose and ABA aspects.

Salinity affects C/N ratio through differential responses of carbon and nitrogen metabolism in mangrove Avicennia marina leaves revealed by combined analysis of transcriptome and metabolome

Salinity affects C/N ratio through differential responses of carbon and nitrogen metabolism in mangrove Avicennia marina leaves revealed by combined analysis of transcriptome and metabolome

Antibacterial activities and molecular identification of endophytic fungi isolated from mangrove Avicennia marina

Abstract. Mulyani Y, Wulandari AP, Sinaga SE, Safriansyah W, Azhari A, Purbaya S, Abdullah FF, Farabi K, Shiono Y, Supratman U. 2023. Antibacterial activities and molecular identification of endophytic fungi isolated from mangrove Avicennia marina. Biodiversitas 24: 6923-6933. This research explored the antibacterial potential of endophytic fungi from the Avicennia marina's (Forssk.) Vierh leaves, stem bark, and root, located in Blanakan, Subang District, West Java. The screening process for antibacterial activity potential was conducted using the Kirby Bauer disk diffusion method. Subsequently, the molecular screening results of the most promising fungi species were identified using Internal Transcribed Spacer (ITS) markers. The results revealed the isolation of 30 fungal isolates. Among these, seven endophytic fungi exhibited significant antibacterial activity against Staphylococcus aureus ATCC 29213 and Vibrio harveyi ATCC 5339, with inhibition zones ranging from 7.88±1.52 to 23.60±0.77 mm. Through molecular identification, 7 endophytic fungi were identified, including Penicillium chrysogenum, Cladosporium anthropophilum, Trichosporon asahii, Cladosporium sphaerospermum, Fusarium verticillioides, Meyerozyma carpophila, and Penicillium steckii. Notably, C. anthropophilum exhibited the highest inhibition zones against S. aureus and V. harveyi measuring 23.60±0.77 and 21.80±0.26 mm, and showed (Minimum Inhibitory Concentration) MIC values of 15.625±0.98 and 31.25±0.39 ?g/mL, respectively. In this study, endophytic fungi isolated from different parts of A. marina exhibited promising antibacterial activity, with Cladosporium anthropophilum from the stem bark showing the highest potency against S. aureus and V. harveyi, suggesting their potential as a source of antibacterial agents. To the best of our knowledge, this is the inaugural study uncovering the isolation and antibacterial potential of endophytic fungi from the genera Cladosporium, Trichosporon, Fusarium, and Meyerozyma. These fungi were extracted from the bark, leaves, and roots of A. marina, situated within the unique mangrove ecosystem of Blanakan Sub-district, Subang District, West Java, Indonesia.

Combined metabolome and transcriptome analysis reveals a critical role of lignin biosynthesis and lignification in stem-like pneumatophore development of the mangrove Avicennia marina.

Transcriptional and metabolic regulation of lignin biosynthesis and lignification plays crucial roles in Avicennia marina pneumatophore development, facilitating its adaptation to coastal habitats. Avicennia marina is a pioneer mangrove species in coastal wetland. To cope with the periodic intertidal flooding and hypoxia environment, this species has developed a complex and extensive root system, with its most unique feature being a pneumatophore with a distinct above- and below-ground morphology and vascular structure. However, the characteristics of pneumatophore lignification remain unknown. Studies comparing the anatomy among above-ground pneumatophore, below-ground pneumatophore, and feeding root have suggested that vascular structure development in the pneumatophore is more like the development of a stem than of a root. Metabolome and transcriptome analysis illustrated that the accumulation of syringyl (S) and guaiacyl (G) units in the pneumatophore plays a critical role in lignification of the stem-like structure. Fourteen differentially accumulated metabolites (DAMs) and 10 differentially expressed genes involved in the lignin biosynthesis pathway were targeted. To identify genes significantly associated with lignification, we analyzed the correlation between 14 genes and 8 metabolites and further built a co-expression network between 10 transcription factors (TFs), including 5 for each of MYB and NAC, and 23 enzyme-coding genes involved in lignin biosynthesis. 4-Coumarate-CoA ligase, shikimate/quinate hydroxycinnamoyl transferase, cinnamyl alcohol dehydrogenase, caffeic acid 3-O-methyltransferase, phenylalanine ammonia-lyase, and peroxidase were identified to be strongly correlated with these TFs. Finally, we examined 9 key candidate genes through quantitative real-time PCR to validate the reliability of transcriptome data. Together, our metabolome and transcriptome findings reveal that lignin biosynthesis and lignification regulate pneumatophore development in the mangrove species A. marina and facilitate its adaptation to coastal habitats.

Bark water uptake through lenticels increases stem hydration and contributes to stem swelling.

Foliar water uptake can recharge water storage tissue and enable greater hydration than through access to soil water alone; however, few studies have explored the role of the bark in facilitating water uptake. We investigated pathways and dynamics of bark water uptake (BWU) in stems of the mangrove Avicennia marina. We provide novel evidence that specific entry points control dynamics of water uptake through the outer bark surface. Furthermore, using a fluorescent symplastic tracer dye we provide the first evidence that lenticels on the outer bark surface facilitate BWU, thus increasing stem water content by up to 3.7%. X-ray micro-computed tomography showed that BWU was sufficient to cause measurable swelling of stem tissue layers increasing whole stem cross-sectional area by 0.83 mm2 or 2.8%, implicating it as a contributor to the diel patterns of water storage recharge that buffer xylem water potential and maintain hydration of living tissue.

Industrially significant biomolecules from recently discovered haloalkaliphiles, inhabitants of the coastal mangrove vegetation in Bordi, India

The coastal Arabian Sea area near Bordi, Maharashtra, India is one of the natural places for mangrove vegetation. This sampling site has been explored for the first time, and to the best of our knowledge, no other researchers have conducted scientific research on the same site prior to this. Water samples from the rhizosphere of the mangrove Avicennia marina were collected and physicochemical examination revealed that the water samples were of saline-alkaline quality. The haloalkaliphiles were isolated by using different microbiological media and characterized by polyphasic approach. Further, the isolates were identified by 16 S rRNA partial gene sequencing and MEGA version 11, a public domain was used for the evolutionary studies. The production of industrially important hydrolytic enzymes amylase, lipase, and protease were optimized in submerged fermentation media using efficient isolates via the OVAT approach, and the enzymes were found to be alkali and salt stable. The carotenoid producer, Planococcus plakortidis BMS5, was deposited at N.C.M.R., Pune, India under accession number MCC5186. The synthesis of carotenoids by Planococcus plakortidis BMS5 was carefully investigated. Thin layer chromatography, UV–VIS spectroscopy, and GC-MS were used to characterise the carotenoids. The hydrolytic enzymes produced by the efficient isolates exhibited great activity and stability over a wide pH (7−12) and temperature (20–50 oC) range. Furthermore, at 10–15% salt, the hydrolytic enzymes were the most stable. The carotenoids produced by haloalkaliphiles were discovered to have antioxidant characteristics and could be exploited in the food and pharmaceutical industries. The haloalkaliphiles' hydrolytic enzymes have the potential to be used in the development of new medicinal formulations. Overall, this study illustrates the potential of employing microbes from extreme environments to produce useful bioactive chemicals with a variety of applications in diverse industries.

Inventory of cadmium-transporter genes in the root of mangrove plant Avicennia marina under cadmium stress

Mangrove Avicennia marina has the importantly potential for cadmium (Cd) pollution remediation in coastal wetlands. Unfortunately, the molecular mechanisms and transporter members for Cd uptake by the roots of A. marina are not well documented. In this study, photosynthetic and phenotypic analysis indicated that A. marina is particularly tolerant to Cd. The content and flux analysis indicated that Cd is mainly retained in the roots, with greater Cd influx in fine roots than that in coarse roots, and higher Cd influx in the root meristem zone as well. Using transcriptomic analysis, a total of 5238 differentially expressed genes were identified between the Cd treatment and control group. Moreover, we found that 54 genes were responsible for inorganic ion transport. Among these genes, AmHMA2, AmIRT1, and AmPCR2 were localized in the plasma membrane and AmZIP1 was localized in both plasma membrane and cytoplasm. All above gene encoding transporters showed significant Cd transport activities using function assay in yeast cells. In addition, the overexpression of AmZIP1 or AmPCR2 in Arabidopsis improved the Cd tolerance of transgenic plants. This is particularly significant as it provides insight into the molecular mechanism for Cd uptake by the roots of mangrove plants and a theoretical basis for coastal wetland phytoremediation.

Evaluation of the Antibacterial Activities of Mangrove Honeybee Propolis Extract and the Identification of Transpeptidase and Transglycosylase as Targets for New Antibiotics Using Molecular Docking.

Developing new antibiotics is a critical area of research that grows as a result of the increasing problem of antibiotic resistance. Scientists search for new antibiotics by screening natural sources such as soil, plants, and marine environments. One of the iconic plants in the marine environment is the mangrove, which is a source of honeybee propolis. Propolis collected from the grey mangrove Avicennia marina on Tarout Island, the Eastern Province of Saudi Arabia, was used to evaluate antibacterial activities against three pathogenic bacteria: gram-negative Enterobacter cloacae (RCMB 001(1) ATCC® 23355TM), gram-positive methicillin-resistant Staphylococcus aureus (clinical isolate), and Streptococcus mutans Clark (RCMB 017(1) ATCC® 25175TM). The results indicate the effectiveness of the methanolic extract of such propolis. The chemical composition of this extract was analyzed using LC-MS, and four compounds were identified (alginic acid, carrageenan, fucoxanthin, cycloeudesmol). Their modes of action were evaluated against bacterial cell walls. Bacterial transpeptidase and transglycosylase on the surface are basic for cell divider amalgamation, and numerous antimicrobials have been created to target these compounds. Molecular docking was employed to predict the interactions of four compounds and S. aureus to predict interaction. Alginic acid was found to be the best interaction with a score of -7.44 Kcal/mol with distance ranges between 2.86 and 3.64 and RMSD refined below 2 Å. Carrageenan with -6.64 Kcal/mol and a distance of 3.05 and 2.87 came second. Then, fucoxanthin with -6.57 Kcal/mol and a distance of 1.4. Finally, cycloeudesmol with a score of -4.6 Kcal/mol and a distance of 2.87 showed the least activity. The first three compounds interacted effectively and could form very promising chemicals that could be used one day against pathogenic bacteria in the future.

Possibility of cultivation gray mangroves Avaccinnia marina (Forsk.) Vierh. in the Iraqi coasts

A team from Marine Science Centre/ University of Basrah, in cooperation with some regional and local scientific institutions, attempted to cultivate the mangrove Avicennia marina in some Iraqi coastal areas, as part of an experiment that is the first of its kind in the country. A site was chosen to plant these trees in the tidal zone in the Khor Al-Zubair oil port. After six months of seedling growth in the greenhouse, the seedlings were transferred to the test site, and measurements of plant growth indicators were carried out for two years at the test site for the period from April 2019 to April 2021. The maximum height of the plants during the study period was 173.3 cm, while The indicators of vegetative growth and chlorophyll content increased significantly during the study period, which is close to the growth of trees in their natural habitats. The survival rates of seedlings were 44% after 24 months of planting. Most of the results were compared according to the Least Significant Difference test (L.S.D.). At a probability level of 0.05.

Characterization and Expression Analysis of Four Cadmium-Tolerance-Associated Genes of Avicennia marina (Forsk.).

Mangroves colonize the intertidal area of estuaries (e.g., Pichavaram, Payardia, and Mai Po) with remarkable cadmium (Cd) pollution. A study on the mechanism of mangrove plant response to Cd pollution can help to understand the adaptive characteristics of plants under Cd stress. This study explored the roles of peroxidase (PRX), pectate lyase (PL), and phytosulfokine (PSK) genes in cadmium tolerance of mangrove Avicennia marina. Full-length sequences of four genes (i.e., AmPRX1, AmPRX2, AmPL, and AmPSK) associated with metal tolerance were identified with suppression subtractive hybridization and rapid amplification of cDNA ends. These genes showed the characteristic features of the respective protein family, indicating functions similar to other plant proteins. Real-time quantitative PCR analysis demonstrated that cadmium exposure resulted in differences in expression patterns among the tissues. Our findings emphasize the complex regulatory mechanism of these four genes in response to trace metal pollution and reveal their functions in metabolic signaling during the stress response.

Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast.

An enhanced understanding of larval ecology is fundamental to improve the management of locally depleted horseshoe crab populations in Asia. Recent studies in the northern Beibu Gulf, China demonstrated that nesting sites of Asian horseshoe crabs are typically close to their nursery beaches with high-density juveniles distributed around mangrove, seagrass and other structured habitats. A laboratory Y-maze chamber was used to test whether the dispersal of early-stage juvenile tri-spine horseshoe crab Tachypleus tridentatus is facilitated by chemical cues to approach suitable nursery habitats. The juvenile orientation to either side of the chamber containing controlled seawater or another with various vegetation cues, as well as their movement time, the largest distance and displacement were recorded. The juveniles preferred to orient toward seagrass Halophila beccarii cues when the concentration reached 0.5 g l-1, but ceased at 2 g l-1. The results can be interpreted as a shelter-seeking process to get closer to the preferred settlement habitats. However, the juveniles exhibited avoidance behaviors in the presence of mangrove Avicennia marina and invasive saltmarsh cordgrass Spartina alterniflora at 2 g l-1. The juveniles also spent less time moving in the presence of the A. marina cue, as well as reduced displacement in water containing the S. alterniflora cue at 1 and 2 g l-1. These results may explain the absence of juvenile T. tridentatus within densely vegetated areas, which have generally higher organic matter and hydrogen sulfide. Early-stage juvenile T. tridentatus are capable of detecting and responding to habitat chemical cues, which can help guide them to high-quality settlement habitats. Preserving and restoring seagrass beds in the intertidal areas should be prioritized when formulating habitat conservation and management initiatives for the declining horseshoe crab populations.

The Effect of Addition of Mangrove Avicennia Marina Extract on The Biofouling Activity to Epoxy Coating

Biofouling is one of the problems related to construction maintenance in industrial developments in the maritime construction sector because biofouling adhesion can affect construction productivity. This problem can be overcome by coating using natural-based paints to reduce the ecological impact that will occur. This study aims to determine the effect of the addition of Avicennia marina mangrove extract as an anti-fouling compound mixed with epoxy paint. This research was conducted by mixing Avicennia marina mangrove extract with epoxy paint. Then the alloy is applied as a coating on the ASTM A36 steel specimen. Furthermore, the test was carried out by immersing the specimen in a solution containing Littorina littorea as a biofouling biota. The average results of the biofouling affixing activity test with the addition of mangrove extract concentrations of 0%, 10%, 20%, and 30% were respectively 24.0 gr, 20.5 gr, 13.5 gr, and 6 gr. This test shows that the more the addition of mangrove extracts, the smaller the adhering activity of biofouling to the specimen.

The impact of inundation and sandstorms on the growth and survival of the mangrove Avicennia marina seedlings in the southern Red Sea

Mangroves occur in tropical and subtropical regions, including harsh arid areas. Little is known about how the environmental conditions of deserts influence the ecology of mangrove seedlings. The seedlings of the mangrove Avicennia marina were examined in situ in a natural stand of the southern Red Sea coast of Saudi Arabia to (1) estimate and compare the growth rate of A. marina between selected microhabitats with different tidal exposures, and (2) examine the influence of sandstorms on the growth and survival of the seedlings. Samplings were conducted in four zones established according to their tidal exposure: low tidal exposure (Z1), medium tidal exposure (Z2), high tidal exposure with numerous burrows (Z3), and high tidal exposure with a few or no burrows (Z4). Vertical growth and mortality of the seedlings and selected environmental variables were quantified. The results show that seedling growth rates differed significantly between the sampling zones, the highest growth being found in the high tidal regions (Z3 followed by Z4) and the lowest growth in Z1. Growth rate followed a significant decreasing pattern over time, coinciding with increasing air temperature and decreasing relative humidity. Sandstorms showed a marked increase in July, leading to massive dust deposition that caused extensive mortality of the seedlings by burial. Our study highlights that seedling growth can be affected by the extent of tidal inundation and that sandstorms act as a natural stressor.

Seasonal Distribution of Benthic Foraminifera Associated with the Marine Sponge Liosina Paradoxa Thiele, 1899 at Sandspit Backwaters, Karachi, Pakistan

ABSTRACT Seasonal diversity and distribution of seven benthic foraminiferal species belonging to six families in association with the marine sponge Liosina paradoxa attached to pneumatophores of the mangrove Avicennia marina were documented at four sampling stations (St1–St4), Sandspit backwaters, Karachi coast during 2013. The calcareous species Ammonia sp. and Quinqueloculina laevigata were recorded at all stations in different seasons whereas the agglutinated species Ammotium cassis and Rotaliammina squamiformis were the most dominant species throughout the study. During the study period, water temperature ranged between 22.5–30.3°C, salinity ranged from 35–40, dissolved oxygen ranged from 0.11–3.45 mg L−1, and pH ranged from 7.15–7.69. The maximum relative abundance (45.65%) of foraminiferal species occurred at St2 from an exposed area while minimum relative abundances (13.04%) were recorded at St3 in sheltered areas. A K-dominance curve showed that highest frequency values in species were observed in the post-monsoon season as compared to the monsoon season. The present study is the first to report the foraminiferal assemblages associated with a marine sponge (Liosina paradoxa) from the mangrove habitat at Sandspit backwaters, Karachi.

Anatomical Adaptation of Grey Mangrove (Avicennia marina) Leaf in the Pond and Coast Located in Mangunharjo, Semarang, Central Java

Mangrove is a brackish plant that can live in habitats with extreme environmental conditions. For instance, the grey mangrove (Avicennia marina) is a mangrove species that can adapt anatomically in habitats with a wide range of salinity, such as ponds and coasts. This study examines the forms of anatomical adaptation of A. marina by comparing the anatomical structure of A. marina leaves that live in two different habitats, namely pond, and coast in the Mangunharjo area, Semarang, Central Java. The third leaf from the tip of the tree branches was used as samples and taken from three different trees in each habitat. Cross-section prepared microscope slides of the leaves were made using the embedding method and observed using a photomicrograph. The quantitative data were analyzed using the T-test at a 90% confidence level, while the qualitative data were analyzed descriptively. The results showed that different environmental conditions do not cause differences in the anatomy of A. marina leaves, but there are some histological modifications as a form of adaptation. These modifications are differences in the thickness of the cuticle, adaxial epidermis, parenchymal palisade tissue, spongy parenchyma, and the number of xylem cells in one vascular bundle. This research might initiate more advanced studies regarding the correlation between mangroves’ anatomical structure and anatomical adaptation towards diverse environmental conditions. The results of this study are expected to provide information about the anatomical structure of A. marina leaves that live in two habitats with different environmental conditions.

Plant litter composition and stable isotope signatures vary during decomposition in blue carbon ecosystems

The ratio of isotopes of carbon (13C:12C or δ13C) and nitrogen (15N:14N or δ15N) are common indicators of the flow and storage of organic matter in coastal wetland research. Effective use of these indicators requires quantification and understanding of: (1) the variability of isotope signatures of potential organic matter source materials; and (2) the influence of organic matter decomposition on isotopic signatures. While it is well-established that organic matter characteristics change during the decomposition process, there has been little direct quantification of any concurrent shifts in isotope signatures for coastal detritus. In this study, we addressed this by quantifying: (1) shifts in sample composition using solid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy; and (2) shifts in δ13C and δ15N signatures of coastal plant tissues from field litterbag experiments. We observed significant shifts in 13C NMR spectra across the course of deployment for all four plant tissues assessed (leaves of mangrove Avicennia marina; branchlets of supratidal tree Casuarina glauca; leaf wrack and roots/rhizomes of the seagrass Zostera muelleri), driven largely by the preferential loss of labile constituents and concentration of more resistant macromolecules, such as lignin and leaf waxes. While there were shifts in isotope ratios for all species, these varied in direction and magnitude among species, tissue type and isotopes. This included δ13C enrichments of up to 3.1‰ and 2.4‰ in leaves of A. marina, and branchlets of C. glauca, respectively, but δ13C depletions of up to 4.0‰ for Z. muelleri. Shifts in δ15N varied among species and tissue types, with few clear temporal patterns. Partial least squares regression analyses showed that some tissue isotope signatures can be reliably predicted on the basis of sample composition (13C NMR spectra), however, multiple inter- and intra-species variations preclude a simple explanation of isotopic signature shifts on the basis of plant-material molecular shifts alone. Further, we cannot preclude the potential influence of microbe-associated organic matter on sample composition or isotopic signatures. Our findings emphasise the importance of considering decomposition effects on stable isotope signatures in blue carbon ecosystems. Isotope approaches will remain a valuable tool in coastal ecosystem research, but require robust experimental approaches (including appropriate use of decomposed end-members or fractionation correction factors; quantification of microbial organic matter) and quantification of decomposition dynamics for specific plant tissues and environmental settings.

Genetic diversity of mangrove tree species Avicennia marina in eco-geographic regions of Kerala coast, Southern India

The genetic assembly of Avicennia marina (Forsk.) Vierh, Avicenniaceae within and between the three natural mangrove forests of Kerala coast belonging to the districts of Kochi, Kozhikode and Kannur was investigated using Inter Simple Sequence Repeat (ISSR) markers to provide coherent scientific conservation practices. The ten selective ISSR primer combinations of 60 genotypes of Avicennia marina ensured a total of 171 bands of which 84.5% were polymorphic. Gene diversity index H varied from 0.142 Kochi to 0.195 Kozhikode. The mean gene diversity H S was 0.169 and the total gene diversity H T was 0.262 which showed a moderate level of genetic diversity in the studied population. The mangrove Avicennia marina populations showed large genetic difference G ST = 0.3849, indicating that 38% of the total genetic diversity was among the populations and the rest 62% resides within the population. The gene flow estimates Nm = 0.79 shown that natural mangroves of Kerala are in the course of differentiation due to genetic drift. We investigated the genetic distinctiveness of taxonomically confusing species, Avicennia marina and Avicennia officinalis , and resulted in clear demarcation between the two. There is a significant correlation between dendrogram and PCoA designated that extensive distant spreading of seeds between populations of Avicennia marina is comparatively low. The genetic study contributed relatively high diversity and strong differentiation across the three eco-geographic locations. The best remedy to preserve coastal mangrove species like Avicennia marina is to plant the identical species in its respective habitat. Launch, on-site protection zones to safeguard the species and to decrease the impact of human activities would allow its habitats to increase in size through natural regeneration.

Barrier to Gene Flow of Grey Mangrove Avicennia marina Populations in the Malay Peninsula as Revealed From Nuclear Microsatellites and Chloroplast Haplotypes

Contemporary mangrove forest areas took shape historically and their genetic connectivity depends on sea-faring propagules, subsequent settlement, and persistence in suitable environments. Mangrove species world-wide may experience genetic breaks caused by major land barriers or opposing ocean currents influencing their population genetic structure. For Malay Peninsula, several aquatic species showed strong genetic differentiation between East and West coast regions due to the Sunda shelf flooding since the Last Glacial Maximum. In this study genetic diversity and structure of Avicennia marina populations in Malay Peninsula were assessed using nuclear microsatellite markers and chloroplast sequences. Even though all populations showed identical morphological features of A. marina, three evolutionary significant units were obtained with nuclear and cytoplasmic markers. Avicennia marina along a 586 km stretch of the West coast differed strongly from populations along an 80 km stretch of the East coast featuring chloroplast capture of Avicennia alba in an introgressive A. marina. Over and above this expected East-West division, an intra-regional subdivision was detected among A. marina populations in the narrowest region of the Strait of Malacca. The latter genetic break was supported by an amova, structure, and barrier analysis whereas RST > FST indicated an evolutionary signal of long-lasting divergence. Two different haplotypes along the Western coast showed phylogeographic relationship with either a northern or a putative southern lineage, thereby assuming two Avicennia sources facing each other during Holocene occupation with prolonged separation in the Strait of Malacca. Migrate-n model testing supported a northward unidirectional stepping-stone migration route, although with an unclear directionality at the genetic break position, most likely due to weak oceanic currents. Low levels of genetic diversity and southward connectivity was detected for East coast Avicennia populations. We compared the fine-scale spatial genetic structure (FSGS) of Avicennia populations along the exposed coast in the East vs. the sheltered coast in the West. A majority of transects from both coastlines revealed no within-site kinship-based FSGS, although the remoteness of the open sea is important for Avicennia patches to maintain a neighborhood. The results provide new insights for mangrove researchers and managers for future in-depth ecological-genetic-based species conservation efforts in Malay Peninsula.

Effect of Heavy Metal Pollution on Leaf Litter Decomposition of Two Species of Mangroves, Avicennia marina and Rhizophora mucronata

Decomposition of litter is influenced by physicochemical characteristics of the habitat which is affected by pollution. In this study the effect of heavy metals on leaf litter decomposition of two mangrove species, Avicennia marina and Rhizophora mucronata is investigated. An experiment was conducted in which litter bags were half-buried in mangrove soil in earthen pots in a greenhouse in which close to natural conditions were maintained and they were treated with 0, 5 and 10 ppm Ni and Pb as a solution of sea water for 16 weeks. Periodic observations were taken on the dry weight remaining and the four factor ANOVA was performed. All four factors (species, heavy metals, concentrations, time) were found to be significant (P at the most 0.05) while some of the interactions were also significant. Half-life and rate of decomposition, k were calculated on the basis of 12 periodic weight loss observations. The litter decomposition followed an exponential decay curve in all cases. The highest rate of decomposition (0.0155 gDWd-1) and the shortest half life (7.44 days) were found for the control of Avicennia marina. In general, decomposition rate of A. marina was more rapid compared to that of R. mucronata. Whereas, the decomposition in treatments with heavy metals were found to be slower than in the controls, the minimum of which (0.0105 gDWd-1) and the longest half life (18.17 days) were found in Rhizophora mucronata leaves treated with 10 ppm Pb. Lead appears to be more inhibitory to the process of litter decomposition compared to nickel. The two mangrove species responded differentially to the heavy metal concentrations. The influence of heavy metals in the decomposition process is discussed.