Pichavaram Mangrove Forest Research Articles

A Data‐Driven Approach to Assess the Impact of Climate Change on a Tropical Mangrove in India

AbstractAs a potential carbon sink, mangroves play an important role in climate mitigation. India houses several major global mangrove patches, which remain vulnerable to climate change. The ecosystem‐atmosphere CO2 exchange is most accurately measured by the eddy covariance method, whereas satellites provide the biophysical parameters for a wider area. In the present study, the Sentinel‐2 satellite data is used to map the land cover types in the Pichavaram mangrove forest and identify two major dominant species (Rhizophora spp. and Avicennia marina), which indicated more than 95% classification accuracy. We used 2 years (2017 and 2018) of in situ gross primary productivity (GPP) and leaf area index (LAI) measurements and rectified the Moderate Resolution Imaging Spectroradiometer (MODIS) GPP and LAI products from 2010 to 2018. The modified MODIS GPP and LAI products were used to develop machine learning models, that is, Random Forest (RF) and Extreme Gradient Boosting (XGBoost) to study the climate influence on mangrove productivity. The RF model (R2 = 0.85 and root mean square error (RMSE) = 0.2) outperformed the XGBoost model (R2 = 0.75 and RMSE = 0.26) and was used to project the impact of climate change on the mangrove GPP for two extreme climate change scenarios, namely SSP1‐1.26 and SSP5‐8.5. The GPP increases and decreases in future during wet and dry periods, respectively. Overall, the projected GPP indicated a reduction of 3.73%–20.3% from 2050 to 2060 and of 4.82%–28.15% from 2090 to 2100, compared to its current average (from 2010 to 2018).

Understanding the impact of climate-induced sea level rise on groundwater inundation in a low-lying coastal area: A numerical simulation in Southeast India

Global warming has led to rising sea levels, severely threatening coastal areas, particularly in low-elevation coastal zones. The groundwater in coastal aquifers of lower elevation is susceptible to groundwater inundation (GWI), an emerging hidden long-term hazard earlier to marine inundation. The inundation is mainly due to the hydraulic connection between sea level and shallow unconfined aquifers, resulting in groundwater upsurging towards the ground surface. To understand the potential impact of sea level rise (SLR) induced GWI on low-lying coasts, a transient state model was simulated and predicted in the Cuddalore regions of South India under 0.3 m, 0.6 m, and 1 m SLR scenarios. The simulation reveals that the aerial extent of groundwater rise (GWR) was 331.9 km2, 566.2 km2, and 650.8 km2 for 0.3 m, 0.6 m, and 1 m SLR scenarios, respectively. About 50% of the response was observed in the northern and central parts of the study area within a 5 km buffer, which is attributed to the deeper groundwater table. In contrast, the southern region exhibited a 10% decline in response due to shallow groundwater discharge to drainage, which dampened the shoaling effect. The present-day shallow groundwater tables in the southern region are more vulnerable to GWI from rising sea levels. Specifically, a 0.3 m SLR could inundate 14.9 km2. In comparison, a 1 m SLR could inundate 40.5 km2 of the area, including the Pichavaram mangrove forest, agricultural land, municipal structures, and the other regions that flooding could threaten. These inundations could have potential impacts, such as wetland loss, agricultural flooding, deteriorating water quality, and infrastructural damage. The present study provides valuable insights into the subsurface hydrodynamic and exposure impacts of sea rise-induced inundations. This can aid coastal engineers, policymakers, and decision-makers to plan appropriate mitigation measures.

Computational Fluid Dynamics Analysis of 3D Wind Flow around Rhizophora Mangrove Tree and Drag Force Acting on the Wall of the Tree

Many natural disasters, such as cyclones, typhoons, mudslides, and tsunamis, are currently plaguing the world. These tragedies, which have destroyed the coastal settlements, claim a great number of lives each year. The characteristics and structure of the Mangrove tree have the significant impact on protecting the coast from heavy wind, floods, mudslides, and other kinds of natural disasters. This research work investigates how Mangroves can protect the area near the coast from a fluid dynamics point of view. Complex real world problems require intelligent systems that combine knowledge and techniques. Hence Computational Fluid Dynamics (CFD) technique namely the finite volume method is employed as a tool in this study. In this research, a model Rhizophora Mangrove tree from Pichavaram Mangrove forest, Tamilnadu, India is generated using Ansys Workbench design modeler. A computational domain is created around this tree to reduce the boundary effect. Grid-independent research was carried out using various mesh sizes to determine the best grid resolution for the analysis. An unstructured triangular mesh was generated for the simulation. The focus of this study is to determine the 3D flow around the tree in order to determine the wind velocity, as well as the coefficient of drag and drag force on the wall tree. This research helps to give a clear understanding of wind flow around the 3D Rhizophora Mangrove tree. The velocity profile, pressure distribution, drag force, and drag coefficient around the tree are captured, analysed, and presented in detail. The results show that the Rhizophora mangrove trees can significantly reduce the flow velocity of the wind and will be able to safeguard the coast and communities nearby from natural disasters.

Unveiling bacterial consortium for xenobiotic biodegradation from Pichavaram mangrove forest soil: a metagenomic approach.

Pichavaram mangrove forest was established as a wetland of International Importance by Article 2.1 in April 2022 by the Ministry of Environment, Forest and Climate Change, India. Even though it is a conserved site, xenobiotic agrochemical leaching on the forest land during monsoon is inevitable. These threaten the microbial diversity in the environment. Xenobiotic degradation is achieved using bacterial consortia already acclimatised to this environment. This study aims to identify the indigenous microbial consortia able to degrade xenobiotic compounds such as fluorobenzoate, furfural, and steroids. Pichavaram mangrove metagenomic dataset was obtained by shotgun sequencing of soil DNA and processed using the automated tool SqueezeMeta. Further, the DIAMOND database provided the taxonomical classification of the microbes in each contig. With reference to the KEGG database, the selected xenobiotic degradation pathways were confirmed in the dataset. Of 1,253,029 total contigs, 1332, 72 and 1262 were involved in fluorobenzoate, furfural and steroid degradation, respectively. This study identified that microbial consortia comprising Marinobacter, Methyloceanibacter and Vibrio natriegens/Gramella sp. can degrade fluorobenzoate. While Afipia, Nitrosopumilus sp., and Phototrophicus methaneseepsis favour the degradation of furfural compound. The steroid degradation pathway possessed a plethora of bacteria belonging to the phylum Proteobacteria.

Seasonal and Spatial Variability of Sediment Characteristics of Pichavaram Mangrove Forest, India

Seasonal and Spatial Variability of Sediment Characteristics of Pichavaram Mangrove Forest, India

Genome Sequence Analysis of Exiguobacterium sp. Strain TBG-PICH-001, Isolated from Pichavaram Mangrove Forest in South India.

ABSTRACTThe draft genome sequence of Exiguobacterium sp. strain TBG-PICH-001, isolated from Pichavaram Mangrove Forest (Tamil Nadu, India), is reported here. Paired-end sequencing technology was used to sequence the genome on the Illumina HiSeq X Ten platform. The genome comprises 3,141,454 bp; it harbors 3,154 genes and has a G+C content of 47.34%.

Augmenting Bioactive Metabolite Synthesis from Streptomyces Species Isolated from Mangrove Sediments through Physio-Chemical Parameters

Actinomycetes were isolated from the sediment samples collected from Pichavaram Mangrove forest in Thandavarayan Sholagan Pet, Chidambaram Taluk, Cuddalore district, Tamilnadu, South India. The actinomycetes were screened for antibacterial (bioactive metabolite) production against Gram positive and Gram negative bacterial organisms. Molecular characterization was performed through 16S rRNA gene amplification to identify the actinomycetes. Standardization of media was done by designing the media at various pH, incubation temperature and sodium chloride concentration and incubation time. It is concluded that four actinomycetes were able to synthesis bioactive metabolite and two actinomycetes (PMA2 and PMA6) were characterized at molecular level as Streptomyces species. They grow better at pH 7.0 and the optimum temperature was found to be 34-37°. PMA2 tolerates up to 5 % sodium chloride concentration, whereas PMA6 tolerates up to 7.5 %. Minimum 7 d of incubation time is necessary for the growth of actinomycetes and concurrently, the antibacterials were peaked from 8th d.

Redescription of Philyra sexangula Alcock, 1896 (Decapoda, Brachyura, Leucosiidae), with description of a new genus and species from the northern Indian Ocean

The identity of Philyra sexangula Alcock, 1896 (Leucosiidae), an inhabitant of mangrove habitats, is clarified. The redescription of the lectotype male and examination of fresh material collected from Pichavaram mangrove forest located in Tamil Nadu State of India revealed that P. sexangula shows significant morphological differences from the generic characters of Philyra sensu stricto. Therefore, a new genus Bellayra gen. nov., is established herewith for the species. In addition, one new species, Bellayra persicum gen. nov., sp. nov., is described based on a syntype male of P. sexangula collected from the Persian Gulf. Furthermore, Philyra taekoae Takeda, 1972 and Philyra nishihirai Takeda and Nakasone, 1991, described from Japan are also transferred to Bellayra gen. nov.

Exploration of Antioxidant Effects of Crude Extract of Mangrove Plant - Avicennia marina

Introduction: Antioxidants are efficient in the prevention of human diseases. Mangroves are high bioactive compounds with good holistic bioactivities including insecticides. Avicennia marina, a mangrove plant which has its origin in South Africa included in the family Acanthaceae.
 Aim: To explore the antioxidant potential of methanolic extract of mangrove plants, Avicennia marina. 
 Materials and Methods: The fresh leaves of Avicennia marina were collected from Pichavaram mangrove forest area. The leaves were washed and then shade dried for 2-3weeks and turned into a fine powder. ​Crude methanolic extract of Avicenna marina was prepared. Total antioxidant activity, DPPH Assay and scavenging activity of hydrogen peroxide were performed and antioxidant potential was assessed using ascorbic acid as standard.
 Results: The scavenging activity increased with increase in concentration of the extract and thus antioxidant activity was dose dependent. The total antioxidant activity was more close to the ascorbic acid equivalence.
 Conclusion: This study concludes that the methanolic extract of Avicenna marina is capable of scavenging a wide range of free radicals for which it can be exploited for the treatment of various free radical mediated diseases. It is evident that mangrove species as a collective are rich sources of antioxidants, phenolics and antimicrobial compounds.

Benthic Meiofaunal Diversity in Four Zones of Pichavaram Mangrove Forest, India

ABSTRACTThe community structure of meiofauna was assessed relative to environmental parameters in four zones (non-mangrove, Avicennia zone, mixed zone, and Rhizophora zone) of Pichavaram Mangrove Forest, which is located along the southeast coast of India. Field sampling was carried out from June 2016–May 2017. The meiofaunal data were evaluated using univariate and multivariate statistics. The highest abundance of meiofauna (434 ind/10 cm−2) was recorded in the Rhizophora zone and the lowest (270 ind/10 cm−2) in the non-mangrove zone. A total of 62 species representing four meiofaunal groups were recorded, including 38 species of foraminifera, 12 species of nematodes, seven species of ostracods, and five species of harpacticoids. Diversity (Shannon H′) mostly ranged from 3–4, and was highest (3.86±0.26) in the Avicennia zone and averaged ∼3.3 in the other three zones. The Margalef richness index was ∼6 in the Avicennia and Rhizophora zones and ∼5 in the non-mangrove and mixed zones. The BIO-ENV and CCA analyses identified sediment texture and organic matter as key variables influencing the distribution of meiofauna, while % calcium carbonate, salinity, and sediment pH were also important. Monitoring studies of meiofaunal taxa may help elucidate their roles in coastal blue-carbon cycling and will also contribute to understanding how mangrove-associated habitats influence meiofaunal distributions.

Seasonal Composition and Diversity of Zooplankton in Pichavaram Mangrove Forest, Southeast Coast of India

In the present study, the zooplankton diversity and distribution was studied in relation to seasonal variation of environmental parameters in the Pichavaram mangrove forest. Samples were seasonally collected (i.e., post-monsoon: January-2018 and monsoon: December-2018) from seven stations. A total of 48 zooplankton species belonging to two groups macro-zooplankton and micro-zooplankton were recorded during this study. A total of 48 species of zooplankton belonging to different groups were identified. Copepod was found to be the most dominant group and it contributed more than 50% of the total zooplankton collected in this study. The maximum number of zooplankton species (35) and diversity value (H’) 3.867 was recorded in the stations near coastal zone (P-7) during summer and minimum species number (24) and maximum species richness (d) 7.652 was recorded in stations near to freshwater zone (P-2) during monsoon. The species evenness (J') 0.866 was also recorded maximum at stations near river mouth (P-7). BIO-ENV (Biota-Environmental matching) and CCA results confirmed that the environmental parameters such as Temperature, Salinity, Dissolved Oxygen, Silicate, Chlorophyll, Primary Productivity, Total Biomass and Phaeopigments as the most influencing environmental parameters, which regulates zooplankton assemblage. The results of present study help to develop an understanding on the zooplankton distribution in mangrove forests, which will form a reliable tool in bio-monitoring studies

Seasonal Variations of Small Wading Birds in the Pichavaram Mangrove Forest, India

The Pichavaram Mangrove Forest (PMF) is one of the important wetlands in southern India. The PMF is harboring numerous species of shorebirds seasonally. The current study assessed the population characteristics of small wading birds by using direct count method from 2015 to 2016. In total, 27 species of small wading birds were recorded, in which the Little stint showed highest density 177.24±20.515 (No./ha.) and the Bar-tailed godwit showed lowest density 0.13±0.099 (No./ha.). Indeed the Little stint was only species turned highest density across the three different seasons studied. However, the bar-tailed godwit not recorded during the pre-monsoon and post-monsoon seasons, the Dunlin, Grey plover and Great sand plover not sighted during the post-monsoon season. The density, diversity and species richness of small wading birds showed significant differences among the seasons (P<0.001). The study inferred that the population characteristics of small wading birds are declining when compared to the previous studies. However exhaustive studies are essential to explore the quality of the PMF which is need of the hour since it is supporting various species of shorebirds seasonally.

Probing of heavy metals in the feathers of shorebirds of Central Asian Flyway wintering grounds

The study is intended to deliver the incidence of heavy metals in the feathers of shorebirds from two important Central Asian Flyway (CAF) migratory shorebirds wintering sites such as the Point Calimere Wildlife Sanctuary (PWLS) and Pichavaram Mangrove Forest (PMF), India. Feathers of fifteen species of shorebirds and seven different metals viz., Cu, Cr, Co, Pb, Hg, Ni and Zn were analyzed. Zn was highest in Dunlin, Little-ringed Plover, Marsh Sandpiper, and Common sandpiper, Ni showed highest in Little ringed plover, and Common sandpiper, Co, Cr, and Cu were maximum in Little stint, Marsh sandpiper, and Dunlin, respectively. The Hg was higher in Black-winged stilt, Common redshank, Curlew Sandpiper, Eurasian curlew, Lesser Sand-plover, Temminck’s stint, Kentish plover, Spotted redshank, and Wood sandpiper, the Pb found highest in Kentish plover, Painted stork, Spotted redshank, Wood sandpiper, Eurasian Curlew, and Lesser sand-plover. The concentration of metals showed significant variations among the species of shorebirds studied (P < 0.001). The mercury negatively correlated with the other metals than the other six metals studied in both the wetlands. The order of metal concentration in the feathers of shorebirds was Zn > Ni > Co > Cr > Cu > Pb > Hg. Nevertheless, the current study revealed that the level of metals in the shorebirds is alarming; since the PWLS and PMF are located along the CAF routes, it needs intensive studies on various pollutions to manage both the resident as well as migratory shorebirds.

Distribution of phylogenetic proximity upon species-rich marine Ascomycetes with reference to Pichavaram mangrove soil sediment of southern India

The Fungi isolated from mangrove soil sediment plays a vital role in mineralization, decomposition of various organic and inorganic substrates of the marine ecosystem. Such marine fungal isolates are widely used in pharmaceutical applications, biochemical conversions, and enzyme technology. The unique adaptableness of fungi allows them to colonize the diverse form of habitats. However, the fungal distribution and phylogenetic proximity rich strains in mangrove sediment are merely studied. Thus our study explores the fungal diversity and its phylogenetic closeness and also the most prevalent species of the Pichavaram mangrove sediment of southern India. In the present study, we perform the phylogenetic proximity and its molecular distribution of Ascomycetes fungi isolated from the Pichavaram mangrove forest. The comparison of genetic diversity analysis of our isolates was further confirmed by our evolutionary imprints. Moreover, the motif enrichment analysis and RNA folding rate of our findings reveal the functional stability may act within the specie rich mangrove soil sediment of Ascomycetes fungi. Only a few studies have undergone about Ascomycetes class in the role of ecology and adaptive mechanism to date. Thus our results evidenced the dominance of ascomycete fungi in estuarine sediment capable of surviving, grow, and interact with other marine microbiomes of that environment helps to build a healthy ecological niche.

A novel approach to assess the heavy metal content in the feathers of shorebirds: A perspective of environmental research

Metals are major toxic elements and cause various diseases and damage shorebirds. The study envisaged the heavy metals content in the feathers of shorebirds, prey, water, and sediment from Pichavaram Mangrove Forest (PMF). Primary feathers of shorebirds species such as Curlew Sandpiper, Eurasian Curlew, and Painted Stork were collected and analyzed the following metals viz., Cd, Cu, Cr, Co, Pb, Hg, Ni, and Zn. The levels of Hg, Cr, Pb and Ni varied significantly among the metals studied (p < 0.05). The metal contamination pattern of shorebirds followed in the following order: Painted stork > Eurasian Curlew > Curlew sandpiper. However, in the habitat, Cd, Co, Pb, Hg, Ni and Zi varied significantly between water and sediment (p < 0.05) and Cd, Cu, Hg, Pb, Ni, and Zi differed significantly among the prey species (p < 0.05). Overall, except for Cd, whereas, other seven metals showed significant differences between the feathers of shorebirds and the environment such as water, sediment, polychaetes, mollusc, crabs, prawns and fishes (p < 0.05). Nevertheless, the resident bird (Painted stork) had a higher level of metal accumulation than migratory species, showing that PMF is under threat and requires proper monitoring, management and conservation strategies to sustain organisms that depend on it.

ISOLATION OF ACTINOMYCETES FROM THE SEDIMENTS OF PICHAVARAM MANGROVE FOREST, SOUTH INDIA AND ANALYSING THEIR ANTIBACTERIAL EFFICACY

Objective: The aim of the present investigation is to isolate actinomycetes from the sediments of Pichavaram mangrove forest, South India, and to screen for their antibacterial efficiency.&#x0D; Methods: Actinomycetes were isolated by culturing the samples in Starch Casein Agar medium; they were screened primarily for their antibacterial efficiency against Gram-positive and Gram-negative bacterial organisms. Solvent extraction was done with 50% (percentage) ethyl acetate, crude extracts of actinomycetes were prepared at different concentrations using dimethyl sulfoxide and treated against the bacterial organisms. Antibacterial assay was done in Mueller–Hinton agar medium.&#x0D; Results: Thirteen actinomycetes were isolated; among them, four actinomycete isolates (Pichavaram mangrove actinomycete 2 [PMA2], PMA6, PMA9, and PMA13) exhibited antibacterial activity.&#x0D; Conclusion: Isolate PMA2 exhibited very strong antibacterial activity and isolate PMA13 is weakly active against the tested bacterial organisms.

The age and species composition of mangrove forest directly influence the net primary productivity and carbon sequestration potential

Abstract Although mangroves inhabit only 0.7% of global coastal zone, but they have a significant contribution to the global carbon. Primary production by mangroves provides a substantial source of energy for aquatic food webs. Net primary productivity and carbon sequestration potential play a pivotal role in understanding the characteristics of the forest ecosystem. Therefore, in order to assess whether the age of mangrove forest and species composition has any influence on the net primary productivity and carbon sequestration potential; six plots of different age group (2, 7, 8, 12, 13 yrs and natural population), and mangrove species combinations were studied in Pichavaram mangrove forest, Tamil Nadu, India. Soil temperature, net canopy photosynthesis and forest functional index significantly varied between mangrove species and age. Regression analysis showed that the soil pH and bulk density positively influenced the carbon sequestration potential which was significant between age group. Higher age group (13yrs) and the natural site showed two-fold higher (21.52 ± 0.72 gC/m2/day) net canopy photosynthesis. Forest functional index, shoot Biomass, root Biomass, plant biomass, carbon biomass and CO2 equivalent showed significant variation with species or age having maximum value in natural plot. Net primary productivity was significant between mangrove species or age. However, carbon sequestration potential increased with the increase in age of plants. Maximum carbon sequestration potential was found in Xylocarpus mekongensis. The data obtained from the present study can be effectively used for drafting conservation and management policies for the fragile mangrove forest ecosystem.

Identification of anticancer activity of phytoconstituents from mangrove

Medicinal plants from the marine ecosystem are a rich source of medicinal plants having a potential for miracle drugs. It is clear from the observation that the local inhabitants of Pichavaram mangrove forest have excellent knowledge about the phytomedicine. Thus they have developed their traditional system of utilizing these mangroves for medicinal purposes. Cancer is the name given to a collection of related and multistep disease. In all types of cancer, a few of the body's cells begin to divide without stopping and spread into the surrounding. It is developed by environmental, physical, chemical, metabolic and genetic factors. In this study, methanol was used to prepare an extract from A. marina leaves and screened for anticancer activity. The phytoconstituents like alkaloids, flavonoids, saponin and tannin present in the extract were quantified, and anticancer activity of the same was identified. Further, the apoptotic cell death effect of methanol extract on the Hela cell line was determined. The flavonoids of A. marina showed higher anti-cancer activity on Hela cells followed by tannin, alkaloids and saponin. The result of the apoptotic cell death effect of A. marina may provide an effective therapeutic strategy against cervical cancer. Finally, it is concluded that the extract of A. marina exhibited anticancer activity.

Diurnal and seasonal patterns of soil CO2 efflux from the Pichavaram mangroves, India.

The diurnal and seasonal variation of soil carbon dioxide (CO2) flux was measured in the Pichavaram mangrove forest, the Southeast coast of India from February 2016 to October 2016 using an automated soil CO2 flux chamber system. Maximum soil CO2 efflux reached at 14:00h and minimum at 00:00h. The surface soil CO2 concentration ranged from 375 to 532ppm with the mean 405 ± 18ppm. The daily soil CO2 flux varied from near zero to about 7μmolm-2s-1 with a mean value of 2.4 ± 1.3μmolm-2s-1. The highest seasonal CO2 efflux from soil was during the summer and premonsoon seasons, whereas low flux values were recorded during the monsoon season. Soil CO2 efflux values were highly correlated with soil temperature. Tidal inundation during monsoon season, extreme drought condition in summer, and unusual precipitation are the major factors controlling the soil CO2 flux.

Taxonomic Characterization and Antagonistic Efficacy of Streptomyces cavourensis SKCMM1 Isolated from Sediment of Pichavaram Mangrove Forest

Taxonomic Characterization and Antagonistic Efficacy of Streptomyces cavourensis SKCMM1 Isolated from Sediment of Pichavaram Mangrove Forest