True Mangrove Research Articles

The True Mangroves of Bintuni Bay, Indonesia with Special Notes on the Existence of Amyema mackayensis (Blakely) Danser and Brownlowia argentata Kurz

This research aimed to identify true mangroves in the ecotone area of Bintuni Bay, West Papua, Indonesia. It applied a plotless transect sampling method to identify two true mangroves previously unknown to the area, namely Amyema mackayensis and Brownlowia Argentina. The presence of the species in Bintuni Bay extended its distribution to the northern area of Indonesian New Guinea. With the addition of these two new records, Bintuni Bay hosted 30 species of true mangroves.

Genome-Wide Identification of Pentatricopeptide Repeat (PPR) Gene Family and Multi-Omics Analysis Provide New Insights Into the Albinism Mechanism of Kandelia obovata Propagule Leaves.

Pentatricopeptide repeat (PPR) gene family constitutes one of the largest gene families in plants, which mainly participate in RNA editing and RNA splicing of organellar RNAs, thereby affecting the organellar development. Recently, some evidence elucidated the important roles of PPR proteins in the albino process of plant leaves. However, the functions of PPR genes in the woody mangrove species have not been investigated. In this study, using a typical true mangrove Kandelia obovata, we systematically identified 298 PPR genes and characterized their general features and physicochemical properties, including evolutionary relationships, the subcellular localization, PPR motif type, the number of introns and PPR motifs, and isoelectric point,and so forth. Furthermore, we combined genome-wide association studies (GWAS) and transcriptome analysis to identify the genetic architecture and potential PPR genes associated with propagule leaves colour variations of K. obovata. As a result, we prioritized 16 PPR genes related to the albino phenotype using different strategies, including differentially expressed genes analysis and genetic diversity analysis. Further analysis discovered two genes of interest, namely Maker00002998 (PLS-type) and Maker00003187 (P-type), which were differentially expressed genes and causal genes detected by GWAS analysis. Moreover, we successfully predicted downstream target chloroplast genes (rps14, rpoC1and rpoC2) bound by Maker00002998 PPR proteins. The experimental verification of RNA editing sites of rps14, rpoC1,and rpoC2 in our previous studyand the verification of interaction between Maker00002998 and rps14 transcript using in vitro RNApull-down assays revealed that Maker00002998 PPR protein might be involved in the post-transcriptional process of chloroplast genes. Our result provides new insights into the roles of PPR genes in the albinism mechanism of K. obovata propagule leaves.

Germplasm Resource Status and Seed Adaptability of Nypa fruticans Wurmb, an Endangered Species in China

Nypa fruticans, commonly known as the Nipa palm, belongs to the true mangrove plants of the Arecaceae family. In China, it is naturally distributed only on Hainan Island and designated as a second-class National Key Protected Wild Plants List. Field research and indoor simulation experiments were systematically employed to study the resource status of N. fruticans and the adaptation of seed germination to environmental factors. The results showed that: (1) Four natural populations of N. fruticans, approximately 9319 trees within a total area of 3.96 hm2, were distributed in Haikou, Wenchang, Qionghai, and Wanning on Hainan Island. Only the Wanning population was developed in small patches, while other populations were scattered sporadically. (2) A total of 23 mangrove species belonged to 19 genera in 13 families, which were recorded in all study sites, of which 18 were true mangroves and 5 were semi-mangrove species. The vertical structures of 4 N. fruticans communities exhibited the consistent pattern, characterized by distinct layers including the tree, shrub, and herb layers. However, notable differences in species composition and dominant species were observed among the layers of each community. (3) The population dynamics of N. fruticans in Haikou, Qionghai, and Wanning were declining, while the population in Wenchang was growing. (4) Seed germination of N. fruticans was not resistant to strong light and required some shade treatment with an optimal light intensity of 60%. The suitable salinity range for seed germination was 0‰ to 10‰. With the increase of salinity, the germination rate and seedling rate showed an increasing and then decreasing trend with maximum values of 63.3% and 50.0% at 5‰, which showed the sensitivity of seed germination to salinity, with low salinity promoting germination whereas high salinity inhibiting germination. Around 8 h/d of flooding time was most suitable for the seed germination, and 10 h/d was a critical flooding time. This study provides a theoretical basis for population recovery, resource utilization, and other further research of N. fruticans.

Molecular mechanism of vivipary as revealed by the genomes of viviparous mangroves and non-viviparous relatives

Vivipary is a prominent feature of mangroves, allowing seeds to complete germination while attached to the mother plant, and equips propagules to endure and flourish in challenging coastal intertidal wetlands. However, vivipary-associated genetic mechanisms remain largely elusive. Genomes of two viviparous mangrove species and a non-viviparous inland relative were sequenced and assembled at the chromosome level. Comparative genomic analyses between viviparous and non-viviparous genomes revealed that DELAY OF GERMINATION 1 (DOG1) family genes (DFGs), the proteins from which are crucial for seed dormancy, germination, and reserve accumulation, are either lost or dysfunctional in the entire lineage of true viviparous mangroves but are present and functional in their inland, non-viviparous relatives. Transcriptome dynamics at key stages of vivipary further highlighted the roles of phytohormonal homeostasis, proteins stored in mature seeds, and proanthocyanidins in vivipary under conditions lacking DFGs. Population genomic analyses elucidate dynamics of syntenic regions surrounding the missing DFGs. Our findings demonstrated the genetic foundation of constitutive vivipary in Rhizophoraceae mangroves.

Diversity Species and Structure of Mangrove Vegetation in Conservation Forest and Angke Nature Park North Jakarta

Mangrove is important life support ecosystems in coastal and marine areas that have bio-ecological and socio-economic functions. Mangroves are found in tidal areas that have the ability to grow in salty waters and have a role as a barrier to abrasion. Mangrove plants have special adaptability to the environment such as adaptation to low oxygen levels, high salinity and less stable soils. Indonesia has the largest mangrove ecosystem and the highest biodiversity in the world. This study aims to determine the index of diversity and structure of mangrove communities in Hutan Lindung Angke-Kapuk (HLAK) and Taman Wisata Angke (TWA) Angke-Kapuk which is divided into 11 points. The research was carried out on November 15 to 30, 2021 using purposive sampling techniques based on the representation element, which took 5% of the total area and the shape of a square plot with a size of 50x50 meters. The results showed that 11 family, 12 genus and 15 species of mangroves were found, the type was divided into 8 species of true mangroves and 7 species of mangroves followed. The extinction rate of mangrove species in HLAK and TWA Angke-Kapuk amounted to 1.25. The level of type similarity between research points in the HL Angke-Kapuk and TWA Angke Kapuk areas in 2020 and 2021, showed a slight change in the level of type similarity at each point. The dominant type of seedling and sapling tree level is the Avicennia marina type. Mangrove diversity index (H’) in the area of HLAK and TWA Angke Kapuk is 1.6.

Mangrove Species Diversity and Its Use as Medicinal Plant by Coastal Communities of Lampung Timur Indonesia

Coastal communities have empirically utilized and proven the medicinal properties of mangrove plants. The objective of the study was to determine the species diversity of mangrove plants and their use as herbal medicine on the coast of Lampung Timur, Sumatra, Indonesia. Mangrove plant diversity was obtained through vegetation analysis and diversity index calculation. The use of mangroves as medicine was obtained through interviews and descriptive comparative analysis. The study revealed that the mangrove forest located on Lampung Timur Coastal comprises 22 species from 12 families. Out of these 22 species, 12 are true mangroves, and the remaining 10 are mangrove associates. Among the 12 true mangroves, the majority (10 species) are major mangroves, while the other two are minor. The diversity index of the Lampung Timur mangrove forest is categorized as moderate (H'= 1.9580). The use of mangrove plants as herbal medicine persists in the Lampung Timur Coastal community. Among the users of mangrove herbal medicine, the majority (55.71%) are from the older generation. Additionally, 64% of users are male, 57.37% are categorized as low-income, and 60.12% identify as Javanese based on ethnicity. The community uses various plant species for medicinal purposes. Avicennia marina is used as an antiseptic, anti-histamine, and source of vitamins. Acanthus ilicifolius is used as an anti-rheumatism and muscle ache medicine/analgesic. Rhizophora apiculata is used as an antipyretic, R. mucronata is used to increase stamina/vitality, and Soneratia caseolaris is used as an anti-cholesterol and anti-oxidant.

Mangroves and their Associates in Metal-Rich Soils in Candelaria, Zambales Province, Philippines

The Philippines, an archipelagic nation in Southeast Asia, has a coastline of over 18,000 km. and hosts at least 50 % of the world’s 65 mangrove species. Mangrove ecosystems are vital in mitigating heavy metal pollution; however, their resilience is compromised in environments with excessive heavy metal contamination. The diversity of true mangrove species and their associates in San Vicente River, Candelaria, Zambales, Philippines was determined. With respect to the physico-chemical composition of the water and sediments. Twenty species of true mangroves were recorded belonging to 11 different families indicating moderate diversity, and 11 mangrove-associated species observed from 10 families. Acanthus ebracteatus was the most abundant species, while Osbornia octodonta was the rarest, found only in Station 1 with only 2 individuals. Sediment samples showed heavy metal concentrations exceeding limits for chromium, iron, nickel and copper. The study highlights the impact of heavy metal contamination on mangrove diversity and soil health, disseminating conservation and remediation efforts for mangrove ecosystem in polluted environments.

Geospatial Biodiversity Assessment of Lagadlarin Mangrove Forest in Lobo, Batangas, Philippines for Sustainable Ecotourism

Sustainable management of mangrove forests for ecotourism requires knowledge on geospatial biodiversity to ensure that the rehabilitation and conservation interventions are appropriate to its ecological condition. This study aims to assess the floristic diversity of the species in the Lagadlarin Mangrove Forest, Lobo, Batangas, Philippines, and integrate the geospatial analysis using a geographic information system as a basis for the sustainable conservation and management of mangroves for ecotourism. The assessment was conducted through a systematic nested quadrat sampling technique by establishing 20 quadrats measuring 10 x 10 m. The area has a very low species diversity based on Shannon-Weiner’s Index (1.82) and Margalef’s Richness Index (0.87). In terms of the species distribution and abundance, the area measured high on Pielou’s Evenness Index (0.61) and Simpson’s Dominance Index (0.78). There are 16 true mangrove species documented in the area, one vulnerable and two near-threatened species. The species that were found dominating the area based on the computed Importance Value are Avicennia marina ssp. rumphiana (89.20%), A. marina ssp. marina (32.85%), Excoecaria agallocha (23.92%), and Acacia farnesiana (21.86%), an invasive species. The enrichment and rehabilitation zones were determined based on the geospatial analysis of the distribution of species diversity for sustainable management of mangrove ecotourism.

Inventarisasi tumbuhan mangrove di Hutan Lindung Tanjung Prapat Muda, Kecamatan Batu Ampar, Kalimantan Barat

Each mangrove ecosystem is diversed which constituted of different vegetations. This also apply for the mangrove area in the Tanjung Prapat Muda Protected Forest, Tanjung Harapan Village, Batu Ampar District. A study of an inventory of mangrove plants was carried out to identify species make up the Tanjung Prapat Muda Protected Forest area. Data collection is conducted alongside the lanes which created by applying the combination of transect and grid lines (transect-plots design). There are 3 lanes with each line consist of 10 plots placed in a zig-zag (right-left) manner. Each plot had sub-plots of different sizes starting from the levels of seedlings (2×2 m), saplings (5×5 m), poles (10×10 m), and trees (20×20 m). Identification was carried out in the field and laboratory. Any unidentified species in the field is documented as herbarium to help identification in the laboratory later. The results shows that there are 7 mangrove species. Five of them are major mangroves (true mangroves), 1 is minor mangrove, and the other 1 are classified as associated mangroves. All the 7 species of plants are belong to 3 families: the Rhizophoraceae, Pteridaceae, and Moraceae families. Five species belong to Rhizophoraceae, namely Rhizophora apiculata, Rhizophora mucronata, Bruguiera gymnorrhiza, Bruguiera parviflora, and Ceriops tagal. The Pteridaceae family consists of one species, namely Acrostichum speciosum, while the Moraceae family only consists of one species, namely Ficus retusa.

DIVERSITY OF MANGROVES AND ASSOCIATED PLANTS IN MANDANGISIAO ESTUARY, MISAMIS ORIENTAL, PHILIPPINES

The study aimed to assess the diversity status of mangroves and associates. Four transect lines were established perpendicular to the shoreline, ranging from 20 to 100 meters based on mangrove stand size. Along these transects, three 10 m × 10 m quadrat plots were set up to evaluate mangrove trees, and within each quadrat, a 2 m × 2 m regeneration plot was established. The study calculated the di-versity indices, such as relative frequency, relative density, and relative dominance to determine the species im-portance value. A total of four mangrove species and two associated plants were identified, representing three mangrove families and three genera, as well as three plant families and three genera for associated plants. The record-ed species included Avicennia marina, Nypa fruticans, Rhizophora mucronata, Sonneratia caseolaris, Acanthus ebrac-teatus, and Acrostichum speciosum. The overall diversity value of the mangroves and associated plants was 0.87, indi-cating relatively low species richness. The true mangroves, Rhizophora mucronata exhibited the highest values for relative density (68.07%), while Nypa fruticans is the highest in terms of relative dominance (42.20%). Both have the same highest value in relative frequency (32.43%). All in all, the highest species importance value for true mangroves is Rhizophora mucronata with 126.23%. In associated plants, highest value of relative density and relative frequency belongs to Acanthus ebracteatus with 58% and 60%, respectively. Subsequently, the highest species importance value for associated plants is 118% for Acanthus ebracteatus. The study concluded that the Mandangisiao Estuary in Jasaan, Misamis Oriental has a limited species diversity, contrary to the initial hypothesis. Furthermore, the mangrove forest in the estuary faces potential threats from garbage dumping, tree cutting, boat mooring, and human encroachment, despite all the recorded species having a Least Concern conservation status.

PENGELOLAAN VEGETASI DI KAWASAN EKOWISATA MANGROVE PERANCAK, JEMBRANA

Perancak mangrove forest is one of the important supporters for mangrove ecotourism in perancak as an ecosystem that functions ecologically, economically and socially as an effort to preserve the beach in a sustainable manner. This research aims to determine the level of diversity of mangrove vegetation types in the perancak coastal area and conduct mangrove management efforts through vegetation analysis and soil analysis. Sampling carriedout on true mangroves and associated mangroves using purposive sampling technique. The method of flora sampling was carried out by quadrant method by calculating the important value index, diversity index and type distribution pattern. True mangroves consist of 13 species and 1367 individuals, dominated by rhyzophora stylosa, with a total importance index (indeks nilai penting)= 299.86 % (classified as sestable), diversity index 1.1192 and distribution pattern = 0.548 (vegetation is stable and uniform). Associate mangroves consists of 13 types and 649 individuals, dominated by the type Terminalia cattapa. Important index =297.892 %, diversity index = 0.9438 and type distribution pattern = 0.73 i.e vegetation that grows is classified as uniform. Analysis results for the 5 soil samples for total n, p and k elements available and organic c, all support mangrove growth. the development of true mangroves and associations is the main supporting factor for the development of tourism areas in the perancak jembrana ecotourism area which is now developing into a beach park developed by the people of Perancak village. Keywords: Perancak; Mangrove Diversity; Management; Soil Analysis

Novel species, morpho‐molecular identification and pathogenicity of Allophoma (Didymellacaeae) causing leaf spots of true mangroves and mangrove associates in Thailand

AbstractTrue mangroves and mangrove associates are salt‐tolerant trees and shrubs that serve a critical role in preserving the ecological balance of tropical and subtropical estuarine environments. However, they are not immune to the damage caused by fungal pathogens. In this study, leaves exhibiting leaf spot symptoms were gathered from mangrove estuary and forests in Prachuap Khiri Khan, Thailand. Through morphological and multilocus phylogenetic analyses (LSU, ITS, RPB2 and TUB2) along with genealogical concordance phylogenetic species recognition, we identified Allophoma acanthi sp. nov. from Acanthus ilicifolius. Additionally, A. minor was identified as the causative agent of leaf spots in true mangrove and mangrove associate species, namely, Acanthus ilicifolius, Combretum sp., Hibiscus tiliaceus, Intsia bijuga, Lumnitzera racemosa and Sonneratia alba. We also provide evidence to support the synonymization of A. thunbergiae with A. minor. All eight isolates of Allophoma species in this study demonstrated pathogenicity to their original hosts with varied virulence, confirming Koch's postulates. Our findings contribute to the understanding of fungal pathogens affecting true mangroves and mangrove associates.

Floristic diversity of mangroves and mangrove associate species of Kali River Estuary, Karwar, Karnataka, India

This study assessed the mangrove flora of the Kali River estuary, Uttara Kannada district, Karnataka. Fourteen true mangrove species belonging to eight families and 11 genera were documented from four locations: Devbagh, Mavinhole, Kalimatha Island, and Halgejoog. The mangrove species show a discontinuous distribution pattern in the Kali River estuary. The highest IVI in true mangroves was recorded for Avicennia officinalis at Devbagh, Acanthus ilicifolius at Mavinhole, Sonneratia caseolaris (after Oryza coarctata) at Kalimatha Island, and S. caseolaris (after Derris trifoliata) at Halgejoog. Of the four sites, Devbagh has the highest Shannon-Wiener diversity index, and with regard to species composition, Devbagh and Kalimatha Island are the most similar sites. Kalimatha island has the most well-preserved mangrove community.

Mangrove forest composition, diversity, and disturbances in Carcar City and Sibonga Municipality, Southern Cebu Island, Philippines

Abstract. Lillo EP, Malaki AB, Alcazar SMT, Chavez MLM, Rosales R, Tomol CJ, Pantinople EM, Redoblado BR, Margate MA, Diaz JL, Isabelo JL, Cagara BNR, Abrigana M, Mago JE, Cañarijo III DM, Sanchez IRG, Obando ME, Belañizo J, Beceril R, Carreon J, Diaz GGG, Gonzaga CFO, Davirao CR, Revillas MJS, Lim JM, Lillo EP. 2024. Mangrove forest composition, diversity, and disturbances in Carcar City and Sibonga Municipality, Southern Cebu Island, Philippines. Biodiversitas 25: 2035-2043. Mangrove forests are one of the world’s most vulnerable tropical ecosystems. The study assessed the mangrove forest composition, diversity, and disturbances in Sibonga Municipality and Carcar City, Cebu Island, Philippines, as a basis for its conservation planning. A transect line was established for a minimum length of 1000 m and a maximum of 2000 m (seaward, middleward, and landward), at an interval of 100 meters. A 10 × 10 m quadrant was established within the transect line at 250 m intervals resulted in a total of 108 plots. Disturbances and threats in two sampling sites were evaluated through direct field observations and interview, and analyzed using the Beynen and Townsend disturbance index. The study identified 22 true mangrove species categorized into 11 families and 14 genera with Excoecaria agallocha L., Sonneratia alba Sm., Rhizophora apiculata Blume, and Avicennia marina (Forssk.) Vierh dominating both sites. The endangered Pemphis acidula J.R.Forst. & G.Forst. was recorded in Sibonga. Aside from low diversity, both sites exhibited a high disturbance index due to illegal activities such as cutting, charcoal production, and land conversion. Such disturbances affects biodiversity and threatens coastal community. Urgent local government action is needed to preserve these ecosystems, emphasizing awareness and community involvement for long-term survival.

A re-evaluation of the tidal sorting hypothesis of mangrove zonation: propagule specific gravity matters

There is much controversy surrounding factors that affect the distribution of mangrove plants across the intertidal gradient. It was previously hypothesized that mangrove zonation was attributed to tidal sorting (TSH) of its propagules according to size (weight) or differential ability of propagules to establish in deep water. However, observational and experimental evidence have provided little support for the actual mechanism(s) of mangrove zonation. In general, species distribution pattern is the consequence of propagule dispersal. The specific gravity of water-borne mangrove propagules may affect their buoyancy, with inherent links to dispersal, thereby potentially influencing tree zonation. Propagule specific gravity can influence the distribution of mangroves in the context of global change, particularly in response to changes in seawater salinity. In this study, we measured the specific gravity and weight of 35 mangrove species propagules. There was no correlation between the weight of the propagule and its specific gravity. The specific gravity of propagules of true mangrove species was significantly greater than that of semi-mangrove. The results of the correlation between propagule specific gravity and the relative surface elevation of field distribution support the hypothesis that propagules are subject to tidal sorting and are not related to weight but to specific gravity. This newfound understanding of mangrove dispersal and distribution is critical in the context of mangrove protection and restoration, especially in projecting the effects of anthropogenic activities and global change on mangrove communities.

Diminishing mangrove forest structures in Davao City, Philippines

The decline of mangrove coverage across the Philippines to 50% of its original coverage in present years has, led to significant reductions of ecological functions to fisheries and benefits to man. The mangrove forest in Davao City was assessed for its taxonomic list, Importance Value Index, abundance and distribution of mangrove regenerations, forest structure, and species diversity status. The study was conducted in Barangay Bunawan, Lasang, Panacan, Matina Aplaya, 76-A, and Bago Aplaya. All data were gathered by establishing sampling plots (10m x 10m) using the modified transect-plot method. Overall, a total of 34 mangrove species were listed, of which 21 were identified as true mangroves and 13 as mangrove associates. The 21 mangrove species were very low in species richness (54%). Importance Value Index showed that Avicennia marina, Rhizophora apiculata, and Sonneratia alba, respectively, as dominant mangrove species. The mangrove regenerations were in poor condition (<0.50) while relative abundances of growth stages consisted of mature stands at 46.04%, saplings with 27.78%, and seedlings with 26.18%. General diversity indices obtained a low value on the Shannon-Wiener diversity index (H'=1.42) and an average value on the species evenness index (E=0.61), all indicating stressful and unstable mangrove forests. Thus, the mangrove forest ecosystem has imbalances and eventually, only certain species would survive.

De novo assembly and analysis of Sonneratia ovata genome and population analysis

Mangroves are an important part of coastal and estuarine ecosystems where they serve as nurseries for marine species and prevent coastal erosion. Here we report the genome of Sonneratia ovata, which is a true mangrove that grows in estuarine environments and can tolerate moderate salt exposure. We sequenced the S. ovata genome and assembled it into chromosome-level scaffolds through the use of Hi-C. The genome is 212.3 Mb and contains 12 chromosomes that range in size from 12.2 to 23.2 Mb. Annotation identified 29,829 genes with a BUSCO completeness of 95.9%. We identified salt genes and found copy number expansion of salt genes such as ADP-ribosylation factor 1, and elongation factor 1-alpha. Population analysis identified a low level of genetic variation and a lack of population structure within S. ovata.

Mangrove Biodiversity Conservation and Aquaculture Practices in Sri Lanka: An Overview

The tropical island of Sri Lanka is endowed with a diverse and resourceful coastal area of 1,700 km coastline and 152,000 ha of highly productive 82 lagoons and 93,075ha of 45 estuary ecosystems. Around 33% of the population in coastal areas is engaged in fishing as the main income source, which contributes to around 1.10% of the national GDP. The objective of the review was to provide an overview of the present status of Sri Lankan coastal aquaculture, mangrove coverage, and conservation status. Mangroves are ecologically and economically important ecosystems providing the best nursery grounds for both blackish and marine species, covering only 0.24% of Sri Lanka‘s total land area. In addition, as the most carbon-rich forests in the tropics, mangroves provide a wide range of ecosystem services and biodiversity conservation. Currently, Sri Lankan mangroves are estimated to cover 160 km2 and are distributed mainly in Jaffna, Kalpitiya, Batticaloa, Rekawa, and Trincomalee. Including endangered species such as Sonneratia apetala, Ceriops decandra, and Lumnitzera littorea, there are 21 true mangrove species, and 24 mangrove associate species can be found. However, mangrove ecosystems in Sri Lanka are progressively under threat due to coastal aquaculture practices, especially shrimp farming and development projects. Human settlements, overexploitation, and climatic variables such as coastal flooding, drought, rainfall, salinity changes, increased sea level, and sea surface temperature have significantly influenced coastal aquaculture and substantially damage the mangroves resulting in loss of mangrove biodiversity. Between 1980 and 2005, approximately 25% of mangrove habitats are estimated to have been destroyed. Recently, 1,000-1,200 hectares of mangroves have been established in 23 wetlands in Sri Lanka becoming leader of the mangrove conservation in Commonwealth countries. In conclusion, it is imperative to apply international standards for mangrove-based aquacultural practices, mangrove rehabilitation, and technical and management interventions. 
 Keywords: Biodiversity, Coastal aquaculture, Coastal ecosystems, Mangroves

Assessing the Ecotourism Potential in Sarasalai-Kuruvikkadu and Adjacent Areas in the Jaffna Peninsula, Sri Lanka

Ecotourism is environmentally responsible, enlightening travel and visitation to relatively undisturbed natural areas in order to enjoy and appreciate nature (and any accompanying cultural features both past and present) that promotes conservation, has low visitor impact, and provides for beneficially active socio-economic involvement of local populations. Sarasalai Kuruvikkadu and adjacent areas such as Anthanathidal and Kapputhu in the Jaffna District are rich with significant extents of mangroves that are notable for their waterbirds’ diversity. The diversity and abundance of birds and the ecotourism potential of those areas have not been evaluated probably due to the three decades long civil unrest. The objective of the present study was to evaluate the nature-based ecotourism potential of Sarasalai Kuruvikkadu and adjacent areas. Geographic Information System was used as tool for identify the potential status of entire Jaffna District. Suitability analysis was applied and Multi Criteria Decision Method (MCDM) and criteria ranking method were used. Three aspects such as Flamingo sites (13), other birds’ sites (40) and mangroves areas (66) in the district including study areas were considered for suitability analysis. The evaluating process for ecotourism sites were conducted based on criteria viz. species richness (of birds), tourist preferences, proximity to residential areas, proximity to accommodation, distance from roads, scenic beauty and density and distribution. Based on each three analysis, Potentials sites were derived based on priority ranking such high, moderate, and low potential. Through the overall analysis, the study areas, Sarasalai and Anthanathidal come under the high potential areas (> 75%) and Kapputhu represents lower potential (<45%) based on flamingo and other birds aspects but based on mangrove sites’ analysis, both areas represent high potential status and Kapputhu represents lower status. Our recent studies have shown that Sarasalai is home to at least 82 species of waterbirds (Margalef’s Index 6.74) and Anthanathidal represents 47 species (Margalef’s Index 9.23) and Kapputhu 22 species (Margalef’s Index 3.04). In addition to some of mammals, crocodiles and fishes were recorded in the study areas that have a high potential for promoting ecotourism. The areas had a high abundance of flamingos, which are a major Avi-tourist attraction. The study areas have large extents mangroves (896.6 ha) with four true mangrove species, Excoecaria agallocha, Lumnitzera racemosa, Rhizophora mucronate and Aegiceras corniculatum which is a unique ecotone and attraction and sources for ecotourism. Hence these areas have a great nature-based tourism potential. There is also a great potential for the participation of local people for promotion of ecotourism in the Jaffna peninsula, elevating their poverty.
 
 Key words: Sarasalai, Kuruvikadu, Ecotourism potential, Mangroves, Flamingo

Stomatal dynamics are regulated by leaf hydraulic traits and guard cell anatomy in nine true mangrove species

Stomatal regulation is critical for mangroves to survive in the hyper-saline intertidal zone where water stress is severe and water availability is highly fluctuant. However, very little is known about the stomatal sensitivity to vapour pressure deficit (VPD) in mangroves, and its co-ordination with stomatal morphology and leaf hydraulic traits. We measured the stomatal response to a step increase in VPD in situ, stomatal anatomy, leaf hydraulic vulnerability and pressure-volume traits in nine true mangrove species of five families and collected the data of genome size. We aimed to answer two questions: (1) Does stomatal morphology influence stomatal dynamics in response to a high VPD in mangroves? with a consideration of possible influence of genome size on stomatal morphology; and (2) do leaf hydraulic traits influence stomatal sensitivity to VPD in mangroves? We found that the stomata of mangrove plants were highly sensitive to a step rise in VPD and the stomatal responses were directly affected by stomatal anatomy and hydraulic traits. Smaller, denser stomata was correlated with faster stomatal closure at high VPD across the species of Rhizophoraceae, and stomata size negatively and vein density positively correlated with genome size. Less negative leaf osmotic pressure at the full turgor (πo) was related to higher operating steady-state stomatal conductance (gs); and a higher leaf capacitance (Cleaf) and more embolism resistant leaf xylem were associated with slower stomatal responses to an increase in VPD. In addition, stomatal responsiveness to VPD was indirectly affected by leaf morphological traits, which were affected by site salinity and consequently leaf water status. Our results demonstrate that mangroves display a unique relationship between genome size, stomatal size and vein packing, and that stomatal responsiveness to VPD is regulated by leaf hydraulic traits and stomatal morphology. Our work provides a quantitative framework to better understand of stomatal regulation in mangroves in an environment with high salinity and dynamic water availability.