Species Composition &amp; Diversity Assessment of Mangroves over Indian Sundarbans

doi:10.21203/rs.3.rs-3224356/v1

Download PDF

Research Article

Species Composition & Diversity Assessment of Mangroves over Indian Sundarbans

https://doi.org/10.21203/rs.3.rs-3224356/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

The study on species composition and diversity measurement has been conducted at the Kaikhali Village under Kultali District, Indian Sundarbans using random sampling technique to get the proper zones for suitable quadrat survey. Field survey has been run during monsoon season and primary data on species composition and diversity components has been incorporated. The primary objective of this study is to comprehend the species composition of true mangroves over Indian Sundarbans and secondary objective is to assess the species diversity profile of the study area. 11 types of true mangroves and 3 types of mangrove associates have been found and taxonomically enumerated during the field survey. For this study, Species Diversity Indices and Diversity Profiles are also measured to get the valid viewpoint regarding the species diversity as well as species richness. Species Distribution within the study area has also been studied through quadrat individual analysis. The results shows up that in spite of micro region under Indian Sundarbans, several mangrove species and their abundance are there and diversity of this region is quite high. However, monotypic species especially Bain (Peyara Bain, Jat Bain & Kalo Bain) species are quite rich and diversified in this region.

True Mangrove Species

Species Composition

Species Diversity Indices

Diversity Assessment

Indian Sundarbans

Shannon & Simpson Index

According to Blasco et al., (1988), Mangrove is described in four following ways: Mangrove ecosystem comprises interface among mangroves-animals-humans-fisheries-hydro-geographical network, forest communities with river networks, canal system and graticules of tidal creek system, sandy or muddy area without any forest. Mangrove forest includes generally forest areas superimposed by hydro-geographical network system belonging to differential salinity based and highly productive inter tidal areas. Mangrove land is associated with woody and grassy halophytic communities from intertidal areas under coastal environment. This section is under almost barren saline soils and generally includes the serial stages of herbaceous halophytes. Mangrove area concept is under indistinct and indefinite manner. Apparently, this section indulges all mangrove communities belonging to salt flats and tidal creek systems and small scale maps (< 1:1000000) showing the nearby concepts of ‘mangrove area’. Mangrove ecosystem comprising of trees and shrubs growing along the tropical and subtropical coastlines is one of the richest and productive ecosystems in the interface between marine and terrestrial ecosystem providing environmental and economic services (DasGupta & Shaw, 2015).

Being the largest delta of the world, it consists of approximately 10,000 km² area under mangrove forest out of which 4200 km² of reserved forest in Indian part and 6000 km² approx. of reserved forest in Bangladesh. Another 5400 km² of inhabited region, non-forest area of India is also known as Sundarbans region of India along the north and north western fringe of mangrove forest. Having the most vibrant ecosystem, Sundarbans is the part of Ganga-Brahmaputra-Meghna delta comprising an area about 25,000km² over southern Bangladesh and West Bengal out of which Indian Sundarbans Delta consists of 9630km² of areal coverage (Guha et al., 2015). According to Department of Sundarbans Affairs, Govt. of West Bengal, being the part of the Man and Biosphere Programme (MAB), as per the general conference of UNESCO in 1970, the Ministry of Environment and forests, Govt. of India adopted the MAB Programme and declared the entire 9630km² area of Sundarbans as the Sundarbans Biosphere Reserve in 1989 for coordinating and integrating diversified activities of conservation, preservation, research and training programmes for creating a great synchronization between nature and human.

True mangroves are a group of plants that are specially adapted to survive in saline and waterlogged environments (Barik et al., 2014). They possess unique adaptations such as specialized root systems, salt filtration mechanisms, and tolerance to tidal fluctuations. The high species richness of mangroves in the Indian Sundarbans is not only important for the biodiversity of the region but also for the ecological functioning and stability of the ecosystem. Each species plays a role in providing habitat, nutrient cycling, carbon sequestration, and other ecosystem services (Nandy et al., 2021). It is important to note that the species richness of mangroves in the Sundarbans may vary due to factors such as tidal influence, salinity gradients, and land-sea interactions. Ongoing research and monitoring efforts help to enhance our understanding of the diversity and distribution of mangrove species in this unique and valuable ecosystem.

These are just a few examples of the true mangrove species found in the Indian Sundarbans. The region is known for its high species diversity, with around 64 plant species reported from the Indian part of the Sundarbans alone. The mangrove forests of the Sundarbans not only support a wide range of plant and animal species but also provide numerous ecological services, including coastal protection, carbon sequestration, and nursery grounds for fish and crustaceans. However, like many other mangrove ecosystems worldwide, the Sundarbans face various threats, including habitat loss, pollution, climate change, and overexploitation. Conservation efforts and sustainable management practices are essential to safeguard the species diversity and ecological integrity of the true mangroves in the Indian Sundarbans.

Species diversity refers to the variety and abundance of different species in a particular ecosystem or on the planet as a whole. It is a measure of the number of distinct species present in a given area or system and the relative proportion of each species within that area. Species diversity is a fundamental component of biodiversity, which encompasses the variety of life forms, genes, and ecosystems on Earth (Islam et al., 2016; Prasanna et al., 2020). It plays a crucial role in maintaining the health and stability of ecosystems, as each species contributes to the overall functioning of the ecosystem in various ways. Assessment of forest biological diversity can give the insight to the conservational aspects and forest management in a sustainable way (Pesiu et al., 2022). There are several aspects to species diversity, including:

Species Richness: This refers to the total number of different species present in a specific area. Higher species richness indicates greater biodiversity. It is a fundamental component of biodiversity and provides a measure of the variety of life forms within a given ecosystem or across a broader geographical region (Islam et al., 2016). The concept of species richness focuses on the count of species and does not consider the abundance or distribution of individuals within those species. It simply represents the total number of distinct species present. Species richness can be measured at various spatial scales, ranging from local communities to entire ecosystems or global scales. For example, in a small pond, species richness may refer to the number of different types of fish, plants, and invertebrates present. On a larger scale, species richness in a tropical rainforest can encompass thousands of plant, animal, and microbial species. High species richness is generally associated with greater biodiversity and ecological complexity. Ecosystems with higher species richness tend to exhibit a wider range of ecological roles, interactions, and functional diversity. This can enhance ecosystem resilience, stability, and productivity.

Species Evenness: Abantao et al., (2015) deciphers that species evenness refers to the relative abundance of different species within an ecosystem. In a diverse ecosystem, species are evenly distributed, whereas in a less diverse ecosystem, some species may dominate while others are scarce. Species evenness, also known as species equitability or relative abundance, refers to the distribution of individuals among different species within an ecosystem. It quantifies how evenly or unevenly individuals are distributed across species within a given area or community. Species evenness is typically measured using mathematical indices, with one of the most commonly used indices being the Shannon evenness index or the Pielou's evenness index. These indices consider both species richness (the number of different species) and the relative abundance of each species. Species evenness also plays a role in ecosystem services and ecological processes. In communities with high evenness, a greater number of species contribute to key ecological functions such as nutrient cycling, pollination, and pest control. This can lead to a loss of diversity and reduced functional redundancy, making the ecosystem more vulnerable to disturbances and less resilient in the face of environmental changes.

Species Composition: This refers to the specific combination of species present in a particular area. Different ecosystems have distinct species compositions based on factors such as climate, geography, and habitat type. It describes the identities and relative proportions of different species within an ecosystem. By studying species composition, scientists can better understand the structure, dynamics, and functioning of ecosystems. It is characterized by such factors like; Dominant species, Indicator species, Keystone species, Rare or Endemic Species, Invasive Species. Studying and monitoring species composition is crucial for various ecological and conservation purposes (Prasanna et al., 2020; Pesiu et al., 2022). It helps in assessing the health and integrity of ecosystems, identifying patterns of biodiversity, understanding ecological relationships, and detecting changes or shifts in communities over time. Conservation efforts often aim to protect and preserve species composition by safeguarding habitats, managing invasive species, and promoting the recovery of threatened or endangered species. Overall, species composition provides valuable information for understanding the unique biological characteristics and ecological dynamics of a given area, contributing to our broader understanding of biodiversity and ecosystem functioning (Pesiu et al., 2022).

Species diversity can be measured using various quantitative indices and metrics that take into account species richness and evenness (Aye et al., 2022). Some commonly used measures of species diversity include (Peet, 2003; Hubálek 2000; Roswell et al., 2021):

Shannon-Wiener Diversity Index (H'): This index combines both species richness and evenness. It considers both the number of species and their relative abundances in a community. The Shannon-Wiener index takes into account the probability of encountering any given species within the community, providing a measure of overall diversity. Higher values of H' indicate greater diversity.
Simpson's Diversity Index (D): Simpson's index focuses more on the dominance or concentration of individuals within a community. It quantifies the probability that two randomly selected individuals belong to the same species. The index ranges from 0 to 1, where higher values indicate lower diversity and dominance of a few species.
Pielou's Evenness Index (J'): Pielou's index measures the equitability or evenness of species within a community. It considers both species richness and the distribution of individuals among species. The index ranges from 0 to 1, with 1 indicating perfect evenness, where all species have equal abundances.
Quadrat Individual Analysis: Quadrat individual analysis is a method used in ecology to study and analyze the distribution and abundance of individuals within a specific area or habitat. It involves the use of quadrats, which are square or rectangular frames of a known size that are randomly or systematically placed within the study area to sample the population. It consists of selection of quadrats, sampling design followed by data collection and its associated analysis. This analysis provides valuable insights into the spatial distribution patterns, population density, and composition of species within a specific habitat. It can help identify areas of high or low abundance, detect changes over time, and provide baseline data for ecological monitoring and conservation efforts.

Study Area

The Indian Sundarbans, located in the eastern part of India and shared with Bangladesh, is a globally recognized hotspot for mangrove forests. Mangroves are unique ecosystems that thrive in the intertidal zones of tropical and subtropical coastal areas, characterized by brackish water and muddy soils. The Sundarbans is home to a diverse range of true mangrove species, which contribute to the region's species diversity and ecological significance. The Sundarbans is home to a diverse range of mangrove species, contributing to its high species richness. The Sundarbans is a UNESCO World Heritage Site and one of the largest mangrove forests in the world.

It is located in the delta region of the Ganges, Brahmaputra, and Meghna rivers, spanning across India and Bangladesh. The Indian Sundarbans, situated in the state of West Bengal, covers a significant portion of the Sundarbans region consisting of two districts specifically named South 24 Parganas and North 24 Parganas. Total 19 blocks are under the Indian Sundarbans where, 13 blocks are from South 14 Parganas and 6 blocks are from North 24 Parganas. Here the study area associated with the Kaikhali village under the Kultali block of South 24 Parganas district under the Indian Sundarbans. Here this study area is subjected to Kaikhali village of Kultali block under the South 24 Parganas district over Indian Sundarbans (Fig. 1).The Sundarbans is renowned for its unique ecosystem, characterized by its mangrove forests, extensive network of tidal rivers and creeks, and diverse wildlife. It serves as a critical habitat for several endangered species, including the Bengal tiger, saltwater crocodile, and various species of birds, reptiles, and marine life. Kultali is a subdivision within the South 24 Parganas district of West Bengal, encompassing several villages and towns. It is one of the administrative units within the Indian Sundarbans and is known for its proximity to the Sundarbans mangrove forests.

Over the Kaikhali Village of Kultali Block under South 24 Parganas over Indian Sundarbans, 15 quadrats were randomly chosen for the species diversity analysis and enumeration of mangrove species (True & Mangrove Associates). Figure 2 deciphers the possible locations of the chosen quadrats that was retrieved through GPS receiver.

Objectives

This study has two primary objectives that are following:

To comprehend the species composition of true mangroves over Indian Sundarbans
To assess the species diversity profile of the study area

Materials

Primary data on identification and enumeration of mangrove species over the study area through the quadrat survey has been considered as the materials of the study. Field work had been run during the monsoon season and quadrats were set as per the availability and accessibility over the study area. True Mangrove Species, Mangrove Associates and Parasites have been found over the area. GPS Points were also measured during the field to get the valid locational attributes of the quadrats size ranged from approximately 7*7 m to 4*4 m.

Methods

This study is oriented towards the Species Diversity Analysis using the primary data analysis through randomly chosen quadrats. After compiling the all data according to the quadrats, Species Richness Analysis, Quadrat Individual Analysis, Species Distribution Analysis, Diversity Profile Analysis, Frequency Percentage (%) & Abundance Analysis, Relative Frequency & Relative Abundance Analysis & Species Diversity Indices Analysis have been run to get an envelope viewpoint regarding the nature of diversity of the study area (Fig. 3). Shannon Index, Simpson Index, Dominance Index & Evenness Index have been measured to get a comprehensive insight of the mangrove diversity of the study area. Species Composition has been evaluated on behalf of the taxonomic enumeration of the mangrove species during the field survey. All sub methods and mapping have been carried out using PAST, Biodiversity Pro Software, Microsoft Excel, Arc Map Version 10.8 and Google Earth Pro Software.

Taxonomic Enumeration of True Mangrove Species

Indian Sundarbans being the most vibrant ecosystem has its own unique diversity having 24 types of true mangrove species. This study belongs to the Kaikhali Village under the Kultali Block of South 24 Parganas district that has been covered through the field survey and 16 types of true mangroves, 4 types of mangrove associates and 2 types of Parasites have been found and taxonomically enumerated through this section (Plate 1).

Plate 1: True Mangroves & Mangrove Associates of Kaikhali Village

Tabulation on Mangrove species of the study area consists of the species composition of the study area (Table 1).

Table 1

Taxonomic Enumeration of Mangroves of the Study Area
Species	Local Name	Scientific Name	Family Name	Nature	Characteristics
Tora	Tora/ Satari	Aegialitis rotundifolia	Aegialitidaceae	True Mangrove Species	• The shrub is up to 3 m high without any aerial roots • The tap roots are sunken, but not penetrate into deep • The leaf of this plants is simple, alternate, cauline, exstipulate, petiolate type
Khalshi	Khalshi	Aegiceras corniculatum	Myrsinaceae		• It is a small tree or shrub upto4 m high, 16 cm-20 cm trunk diameter at the base • The leaves are simple, alternate or spirally arranged • The inflorescence is simple
Geoa	Geoa/Gneoa	Exoecaria agallacha	Euphorbiceae		• This is a medium dioecious tree, 15 m-20 m high, deliquescent, woody, • The roots are generally without any aerial growth • The stems are differentiated into nodes and internodes
Chak-keora	Chak-keora	Sonneratia caseolaris	Sonneratiaceae		• It is a small evergreen tree, up to 8 m high, deliquescent branching, woody • The leaves are opposite, decussate, exstipulate, simple, cauline, short, petiolate • The germination is epigleal
Keora/Tak-keora	Keora/Tak-keora	Sonneratia apetala	Sonneratiaceae		• It is a small to medium sized tree, up to 15 m high, crown large, deliquescent branching • The internodes are 3cm-4cm in length • The leaves are opposite, decussate, simple, cauline, petiolate
Passur	Passur	Xylocarpus mekongenesis	Meliaceae		• It is a much branched, deciduous tree attain up to 20 m high, a mangrove species • buttresses very insignificant or absent, but well developed aerial root-suckers • The inflorescence united cymes, about 8 cm long, longer with distinct main axis
Manda	Manda	Viscum orientale	Loranthaceae	Parasites	• The stem is much differentiated into nodes and internodes, much branched • The leaves are, petiolate, petiole not prominent • The inflorescence is cymosely type
Bara Manda	Bara Manda	Dendrophthoe falcata	Loranthaceae	Parasites	• It is a semi-parasitic plant or epiphytic plant on the mangrove forests • The normal roots are absent • The stem is well differentiated into nodes and internodes, branched
Gol-pata	Gol-pata	Nypa fruticans	Arecaceae	True Mangrove Species	• The stem is dichotomously, branched • The leaves innately compound, spirally arranged on the top • The seeds grooved ad axially
Jat ban/Jatbani/Jatbyne	Jat ban/Jatbani/Jatbyne	Avicennia officinalis	Avicenniaceae	True Mangrove Species	• It is an evergreen, perennial tree, generally attain height between15 m and 20 m • The aerial roots are well-developed, pneumatophores numerous • The number of pneumatophores varies between 500–1200
Kalo ban/Kalo ban/Kala byne/Kali Bain	Kalo ban/Kalo ban/Kala byne/Kali Bain	Avicennia alba	Avicenniaceae	True Mangrove Species	• This is an evergreen medium tree, perennial, generally 10–12 m high • The underground roots are much branched, divergent, spreading horizontally
Peyara ban/Peyarabani/Peyarabyne	Peyara ban/Peyarabani/Peyarabyne	Avicennia marina	Avicenniaceae		• This is a shrub to small tree, bushy, evergreen, perennial, generally 3 m-8 m high • The underground roots are much branched, spreading horizontally, runs up to 15 m away from the trunk base • The leaves are opposite, decussate, cauline, simple, exstipulate, petiolate
Mat-Garan/JatGaran	Mat-Garan/JatGaran	Ceriops tagal	Rhizophoraceae		• This is a small to moderate tree, much branched, pyramidal, up to 8m high, evergreen • The leaves are opposite, decussate, simple, cauline, exstipulate, petiolate
Jhamti Goran	Jhamti Goran	Ceriops decandra	Rhizophoraceae		• It is an evergreen shrub or small tree, attain 3m-5m height • The leaves are opposite, decussate, cauline, simple, petiolate
Dhundul	Dhundul	Xylocarpus granatum	Meliaceae		• It is much branched, dark green, deciduous tree • The leaves are compound, with usually 4 leaflets, opposite, superimposed or alternate
Dhani Ghash	Dhani Ghash	Porteresia coarctata	Poaceae	Mangrove Associate	• It is a culm standing, erect from a stout creeping rhizome or root stock • The length of the internode is 8cm-14cm long
Kankra	Kankra	Bruuiera gymnorrhiza	Rhizophoraceae	True Mangrove Species	• The tree is medium in size,12m-15m in height, evergreen, erect, much diffused spreading branches • The under-ground roots are not deep sunken, profusely spreading from the surface layer
Giria Sak	Giria Sak/ Giresak	Suadea maritima	Chenopodiaceae	Mangrove Associate	• It is an erect much branched herb. • The root is tap root, occasionally exposed during tidal current. • The internodes are not rigid, solid, woody, rough, terete, green grey. • There are spikes at leaf axis: ebracteate, small flowered.
Mota Giria	Gad Bani/Mota Giria	Sesuvium portulacastrum	Aizoaceae		• The plant is prostrate, much branched herb, occasionally creeping on the mud frequently. • The tap roots are poorly developed. • The adventitious roots develop from the nodes. • The leaf is simple type, opposite decussate, exstipulate, petiolate
Harkosh Kanta	Harkoch Kanta/ Horgoja	Acanthus ilicifolius	Acanthaceae		• It is tiny shrub or tall herb, up to 1.5 m high, scarcely woody, bushy with very dense growth. • Shallow tap roots, but occasionally stilt roots are conspicuous from the tap roots, fibrous nutritious roots develop. • The leaf is simple, opposite decussate, cauline, exstipulate, petiole short, 0.3 cm long and 0.4 cm broad

Species Diversity Analysis

Species Diversity Analysis has been enveloped through some sub analyses consisting of Species Distribution Analysis, Species Richness Analysis, Quadrat Individual Analysis, Frequency Percentage-Relative Frequency & Abundance- Relative Abundance Analysis, and Species Diversity Indices Analysis. Species Diversity Indices Analysis is composed of three types of indices e.g. Shannon Index, Dominance Index, and Simpson Index & Evenness Index.

Frequency (f): The number of times a given event occurs.

e.g., the number of quadrants that contain maple trees as a ration of all the quadrants

f_{i =}j_i/k

Where, j_i =Number of quadrants with species i

k = Total number of quadrants

Relative Frequency (RF _i ): The frequency of species relative to the sum total of the frequencies of the other species found.

RF_i = (Frequency of a Species/ Frequency of all Species)*100

Abundance: Species Abundance is the number of individuals per species. In a quadrat study, abundance is calculate using the formulae:

Abundance=\(\frac{\varvec{T}\varvec{o}\varvec{t}\varvec{a}\varvec{l} \varvec{n}\varvec{o}. \varvec{o}\varvec{f} \varvec{i}\varvec{n}\varvec{d}\varvec{i}\varvec{v}\varvec{i}\varvec{d}\varvec{u}\varvec{a}\varvec{l} \varvec{o}\varvec{f} \varvec{t}\varvec{h}\varvec{e} \varvec{s}\varvec{p}\varvec{e}\varvec{c}\varvec{i}\varvec{e}\varvec{s}\varvec{A}}{ \varvec{N}\varvec{o}. \varvec{o}\varvec{f} \varvec{q}\varvec{u}\varvec{a}\varvec{d}\varvec{r}\varvec{a}\varvec{t}\varvec{e} \varvec{p}\varvec{e}\varvec{r} \varvec{u}\varvec{n}\varvec{i}\varvec{t}\varvec{s} \varvec{i}\varvec{n} \varvec{w}\varvec{h}\varvec{i}\varvec{c}\varvec{h} \varvec{t}\varvec{h}\varvec{e}\varvec{y} \varvec{o}\varvec{c}\varvec{c}\varvec{u}\varvec{r}}\)*100

• Relative Abundance:

Relative Abundance=\(\frac{\varvec{T}\varvec{o}\varvec{t}\varvec{a}\varvec{l} \varvec{n}\varvec{o}. \varvec{o}\varvec{f} \varvec{s}\varvec{p}\varvec{e}\varvec{c}\varvec{i}\varvec{e}\varvec{s} \varvec{A}}{\varvec{T}\varvec{o}\varvec{t}\varvec{a}\varvec{l} \varvec{n}\varvec{o}. \varvec{o}\varvec{f} \varvec{i}\varvec{n}\varvec{d}\varvec{i}\varvec{v}\varvec{i}\varvec{d}\varvec{u}\varvec{a}\varvec{l} \varvec{o}\varvec{f} \varvec{a}\varvec{l}\varvec{l} \varvec{s}\varvec{p}\varvec{e}\varvec{c}\varvec{i}\varvec{e}\varvec{s}}\)*100

Shannon-Weiner Index: Shannon-Weiner index of diversity (information index) is a measure derived from information theories developed by Claude E. Shannon and Nobert Weiner and published in 1949 by Shannon and Warren Weaver.

H=-∑p_i ln p_i

Where, P_i=\(\frac{No. of individual of a species }{No. of individuals of all species in the sample}\)

• Simpson’s Index(D):

D = 1-\(\frac{\sum \varvec{n}(\varvec{n}-1)}{\varvec{N}(\varvec{N}-1)}\)

Where, D = Diversity

N = Total number of organisms of all species found

n = Number of individuals of a particular species

Evenness Index (J’): Pielou's index measures the equitability or evenness of species within a community.

J’= H/H_max

H_max= Maximum Value of H ln(s)

Species Distribution Analysis

As per the species distribution analysis of the study area, it has been found that all species are aggregated except Manda Species is randomly distributed individually. As per the statistics, total chi- square value of whole community is 10204.74414; pooled chi-square value is 1210.403198 & Heterogeneity is 8994.34082. Total & Pooled values are dispersed aggregately and Heterogeneity is dispersed in discordantly.

Species Richness Analysis

Species Richness Analysis Graph consists of two factors e.g. No. of Pooled Samples & estimator. As per the pooled samples (15), Estimator values have been differentiated where, for 12–15 pooled samples the estimator value is 16 (Highest), for sample 1 the estimator is 4.8 (Lowest) & for other samples (2–11) the value ranges between 6.8–15.6.

Quadrat Individual Analysis

The various species which has been found in the study area has been divided in 15 quadrats. The different species has been distributed in the different quadrats which has been considered. The various species has been studied and the data has been analyzed later. In the above data it has been found that Jat Bain has been found in the maximum number (518) at quadrat 6 and Manda has been least (1) found at quadrat 6.

A Quadrat Matrix Plot has been carried out for the better presentation of the species distribution and frequency based analysis throughout the 15 quadrats chosen at the field. It’s one kind of Pictogram where shades of color have been used to represent the frequency variation and distribution of all species encountered throughout the quadrats.

Highest Frequency is shown for Jat Bain species at Q6 and lowest found for Manda at Q6 (Fig. 8).

Frequency Percentage & Abundance Analysis

Frequency Percentage and Abundance Analysis depicts about the how diversified a particular species in a specific area. It has been observed that, the Kalo Bain & Jat Bain has the maximum Frequency % (100%) and the lowest frequency percentage is of Tok Keora (6.6667), Kakra Gach (6.6667) and Giria Sak (6.6667). In the case of Abundance, the highest value of Abundance is for Dhani Ghash (207.5) & the lowest value of Abundance is for Manda (1).

Rank wise Abundance Plot has been evaluated for the better understanding of species wise abundance values. As per statistics, highest abundance value (100) is for Manda Species, Lowest (19.264) is for Jat Bain that is high in number in the study area. For the rest of species, the abundance ranges between 35.887–99.963 (Fig. 10).

Figure 9: Abundance Plot

Relative Frequency & Relative Abundance Analysis

Relative Frequency analysis is used to determine how often certain values of a specific species may occur and to assess the reliability of the prediction. Relative Abundance can be measured of how frequent or rare a species is in relation to other species in a specific area or community.

It has been observed that the highest relative frequency of Kalo Bain and the Jat Bain (0.1807229) and the lowest value is for Manda (0.01204819). The highest value for Relative Abundance is for Jat Bain (19.26367) and the lowest value is for Manda (0.11156) (Fig. 11).

Species Diversity Indices Analysis

Three types of indices have been considered for the species diversity analysis of the study area e.g. Shannon Index, Simpson Index & Evenness Index.

a) Shannon Index/ Diversity Index (H) is an important species diversity index that indicates higher the value higher the diversity, lower the value lower the diversity.

Figure 11: Shannon Index (H)

It has been observed that the highest Shannon-Weiner Index value is for Jat Bain (0.31726285) and the lowest Shannon-Weiner Index value is for Manda (0.00293675). Q9 (1.704) has the highest value & Q2 (0.4947) has the lowest diversity value (Fig. 12).

b) Dominance Index (D) is an important species diversity index which belongs to the dominancy index. Higher the value, lower the diversity and higher the dominancy level lower the value higher the diversity and lower the dominancy level. Q2 (0.7806) has the highest value and Q14 (0.2429) has the lowest dominance value (Fig. 13).

c) Simpson Index (1-D) is used to measure the level of species diversity from the dominancy index by subtracting from 1. Higher the value, higher the diversity and lower the value, lower the diversity.

Figure 13: Simpson Index (1-D)

The highest Simpson Index value is for Manda (1) and the lowest value is for Jat Bain (0.962949). It can be concluded that Jat Bain is more dominant over the other species and more diversified in the study area. Q9 (0.7744) has the highest value whereas, Q2 (0.2194) has the lowest value (Fig. 14).

d) Evenness Index

This index is considered respective to the Shannon index (H) for the equitability analysis of the species diversity analysis. This value also ranges from 0 to 1. Higher the value higher the equitability or evenness and lower the value lower the equitability or evenness. 1 value indicates perfect evenness where all species have equal abundances.

Highest evenness index value is found at Q11 (0.7846) and lowest value is found in Q2 (0.328). Quadrat wise, Q11 shows the comparatively higher equitability or evenness as value is nearer to 1 and Q2 is found to be less even.

Diversity Profile Analysis

This section collaborates the Diversity Profile Analysis where, X axis demonstrates corresponding Alpha value and Y axis corresponds to the Diversity values. A Diversity Profile using 95% confidence level has been prepared for the better understanding of the nature of species diversity throughout the randomly chosen quadrats over the study area. Alpha Value ranges between 0-3.96 and corresponding to those values quadrat wise diversity profile has been prepared.

This study enumerates the regional distribution of species combining the species composition and diversity assessment through various diversity measurement techniques and measures. Indian Sundarbans having a vibrant mangrove ecosystem consists of 19 blocks belonging to two districts South 24 Parganas and North 24 Parganas and this estuarine ecosystem has diversified mangrove species (True Mangrove Species, Back Mangroves, Mangrove Associates, and Parasites etc.). As per the study area, Kaikhali village under Kultali block belonging to South 24 Parganas district has its own diversified mangrove ecosystem as primary survey reveals that total 16 types of true mangrove species and 4 types of mangrove associates and 2 types of parasites have been enumerated.

Proper methodological framework guides the assessment of species diversity and species composition where, randomly chosen quadrat wise several analysis have been incorporated. All species are distributed in an aggregated manner except the Manda species that is randomly distributed. For the insightful analysis, quadrat wise distribution has been carried out through the quadrat matrix plot and quadrat wise individual analysis. For the frequency distribution analysis, proper formulae on Frequency (%), Abundance, Relative Frequency and Relative Abundance have been analyzed. This analysis shows that Kalo Bain and Jat Bain being the most frequented and abundant species over the study area. Species diversity measurement indices have been run to get the better understanding of diversity, dominancy and equitability of selected species over the study area. A Diversity profile has been presented to get evaluation on quadrat wise diversification of all species.

Having analyzed the micro level species diversity assessment and associated taxonomic enumeration of all species found over the study area, remarks on conclusion asserts that there is a possible diversification of mangrove species over the study area especially Bain species are very much aggregately distributed. However, this study area is in quite danger due to mangrove degradation related to several anthropogenic reasons such as deforestation issues, tourism, and high salinity intrusion etc. Species wise salinity distribution and tolerance level along with others geomorphological factor over Indian Sundarbans can be recommended for the insightful and resourceful scientific study.

Acknowledgement

Authors are grateful to the University Grant Commission (UGC) for providing the Fellowship to the First Author as NET JRF. The authors have extended their deep appreciation and indebtedness to Jadavpur University for providing the logistics and infrastructure, along with the supervising expertise.

Ethical Approval

This article does not contain any studies with human or animal subjects performed by any of the authors.

Competing Interests

The authors declare no competing interests.

Author’s Contribution

The First author studied and prepared the manuscript and the second author supervised and edited the same.

Funding

This study is not funded.

Availability of Data & Materials

Data & Materials will be available on request.

Abantao SC, Apacible TC, Cortez SP, Pereda LT, Yllano OB (2015) Mangrove species diversity and on-site impact assessment of mangal coastal areas. Expert Opin Environ Biol 4:2
Aye WN, Tong X, Tun AW (2022) Species diversity, biomass and carbon stock assessment of Kanhlyashay Natural Mangrove Forest. Forests 13(7):1013
Barik J, Chowdhury S (2014) True Mangrove Species of Sundarbans Delta, West Bengal, Eastern India: A Revised Species List. Check List. 10:329. 10.15560/10.2.329
Blasco F, Gauquelin T, Rasolofoharinoro M, Denis J, Aizpuru M, Caldairou V (1998) Recent advances in mangrove studies using remote sensing data. Mar Freshw Res 49(4):287–296
DasGupta R, Shaw R (2015) An indicator based approach to assess coastal communities’ resilience against climate related disasters in Indian Sundarbans. J Coast Conserv 19(1):85–101
Guha P, Aitch P, Bhandari G (2015) Climate change and its impact on the ecological system of the Indian Sundarban region. Clim Change 1(4):432–438
Hubálek Z (2000) Measures of species diversity in ecology: An evaluation. Folia Zool 49:241–260
Islam S, Feroz SM, Ahmed ZU, Chowdhury AH, Khan RI, Al-Mamun AB D. U. L. L. A. H. (2016). Species richness and diversity of the floristic composition of the Sundarbans mangrove reserve forest, Bangladesh in relation to spatial habitats and salinity. The Malaysian Forester, 79(1&2), 7–38
Nandy S, Tamang M, Kushwaha S (2021) Plant Diversity Assessment in Indian Sundarban Mangroves: A Geoinformatics Approach. 10.1201/9781003083573-5
Peet R (2003) The Measurement of Species Diversity. Annu Rev Ecol Syst 5:285–307. 10.1146/annurev.es.05.110174.001441
Pesiu E, Lee GE, Salam MR, Salim JM, Lau KH, Yong JWH, Abdullah MT (2022) Species Composition, Diversity, and Biomass Estimation in Coastal and Marine Protected Areas of Terengganu, Peninsular Malaysia. Agronomy 12(10):2380
Prasanna MG, Ranawana KB, Jayasuriya KMG (2020) Species composition, abundance and diversity of mangroves in selected sites in Ampara District in th east coast of Sri Lanka (RP0636)
Roswell M, Dushoff J, Winfree R (2021) A conceptual guide to measuring species diversity. Oikos 130(3):321–338

Plate 1 is available in the Supplementary Files section.

No competing interests reported.

floatimage5.jpeg
Plate 1: True Mangroves & Mangrove Associates of Kaikhali Village

Download PDF

Version 1

posted

You are reading this latest preprint version

Species Composition & Diversity Assessment of Mangroves over Indian Sundarbans

Status:

Version 1

Abstract

Figures

Introduction

Study Area

Objectives

Materials & Methods

Materials

Methods

Results & Discussion

Taxonomic Enumeration of True Mangrove Species

Plate 1: True Mangroves & Mangrove Associates of Kaikhali Village

Species Diversity Analysis

f_{i =}j_i/k

RF_i = (Frequency of a Species/ Frequency of all Species)*100

• Relative Abundance:

H=-∑p_i ln p_i

• Simpson’s Index(D):

D = 1-\(\frac{\sum \varvec{n}(\varvec{n}-1)}{\varvec{N}(\varvec{N}-1)}\)

J’= H/H_max

Species Distribution Analysis

Species Richness Analysis

Quadrat Individual Analysis

Frequency Percentage & Abundance Analysis

Relative Frequency & Relative Abundance Analysis

Species Diversity Indices Analysis

d) Evenness Index

Diversity Profile Analysis

Conclusion

Declarations

References

Plate

Additional Declarations

Supplementary Files

Status:

Version 1

Species Composition & Diversity Assessment of Mangroves over Indian Sundarbans

Status:

Version 1

Abstract

Figures

Introduction

Study Area

Objectives

Materials & Methods

Materials

Methods

Results & Discussion

Taxonomic Enumeration of True Mangrove Species

Plate 1: True Mangroves & Mangrove Associates of Kaikhali Village

Species Diversity Analysis

fi =ji/k

RFi = (Frequency of a Species/ Frequency of all Species)*100

• Relative Abundance:

H=-∑pi ln pi

• Simpson’s Index(D):

D = 1-\(\frac{\sum \varvec{n}(\varvec{n}-1)}{\varvec{N}(\varvec{N}-1)}\)

J’= H/Hmax

Species Distribution Analysis

Species Richness Analysis

Quadrat Individual Analysis

Frequency Percentage & Abundance Analysis

Relative Frequency & Relative Abundance Analysis

Species Diversity Indices Analysis

d) Evenness Index

Diversity Profile Analysis

Conclusion

Declarations

References

Plate

Additional Declarations

Supplementary Files

Status:

Version 1

f_{i =}j_i/k

RF_i = (Frequency of a Species/ Frequency of all Species)*100

H=-∑p_i ln p_i

J’= H/H_max