Check List 10(2): 329–334, 2014 © 2014 Check List and Authors Chec List ISSN 1809-127X (available at www.checklist.org.br) Journal of species lists and distribution

True Mangrove Species of Sundarbans Delta, West Bengal, pecies S

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Jyotiskona Barik 1* and Soumyajit Chowdhury 2 ists L Eastern India 1 School of Oceanographic Studies, Jadavpur University, Kolkata – 700032, West Bengal, India.

[email protected] 2 Centre for Biodiversity and Ecological Studies, Kolkata – 700 084, West Bengal, India. * Corresponding Author. E-mail: Abstract: Varied opinions exist as to the species composition and ecological distinction of mangrove habitats of the Indian Sundarbans. Furthermore, distinction of true or major mangroves from mangrove-associate and minor species was left unresolved by past authors. The present study thus aimed to revise a species list of true mangroves in the Indian Sundarbans delta. An indexing of adaptive morpho-physiological characters of mangroves for the tidal-saline environment was conducted. The analysis illustrated 24 species of true mangroves in Indian Sundarbans, belonging to nine families. Of

has highlighted the taxonomic richness and status of true mangrove from Indian Sundarbans, resolving the long debated distinctionthese, Rhizophoraceae of true from showed minor and maximum associate richness mangroves. at each of the generic and specific categories assessed. The current study

Introduction families Mandal and Naskar (2008). Further ambiguity exists regarding the distinction of major or true mangroves fauna due to its extremely dynamic physico-chemical from minor and mangrove-associated species, particularly The Sundarbans delta is a rich reservoir of flora and at their generic levels. Mandal and Nandi (1989) reported dynamic zone supports a diverse gene pool of micro and 22 true mangroves species from Indian Sundarbans, macrofactors. biotic Encompassing communities, India in andwhich Bangladesh, mangrove thisvegetation highly while Chaudhuri and Choudhury (1994) reported 36 occupies a special status (Guha Bakshi et al., 1998). The species. The studies of Naskar (1983) and Naskar and Sundarbans mangrove ecosystem is highly productive and Mandal (1999) did not clarify this issue, as they remained serves as a link between terrestrial and estuarine aquatic uncertain regarding the exact status and composition of ecosystems (Untawale, 1987). true or major mangroves in Indian Sundarbans. However, Mangroves are a threatened salt tolerant higher group according to recent studies by Mandal and Naskar (2008), 28 species of major mangroves have been found in Indian in relatively sheltered areas along estuaries, coastal Sundarbans. The study also mentioned Indian Sundarbans lagoonsof flowering and backwaters.plants (Naskar They and are Mandal, generally 1999) inundated that occur and to be more diverse in its species composition than the exposed during regular high and low tides respectively, other mangrove formations in India. and are nurtured by a mixture of fresh water from rains In the present context, the authors seek to revise the and land drainage with coastal marine waters (Banerjee species list of the true or major mangroves occurring et al. 2002). The plants of mangrove vegetation are in Indian Sundarbans, taking into consideration their relatively poor in species diversity and show similarities morpho-physiological characters for adapting to the tidal- in their general architecture and physiological adaptations saline environment in this deltaic region. – a case of convergent evolution. Typical mangrove species usually have pneumatophores or breathing roots Materials and Methods (negative geotropic root), stilt roots, knee roots, viviparous Study Area germination, xerophyllous leaves and salt excretory glands (Tomlinson, 1986). However, several mangrove workers like Mac Nae (1968), Blasco (1977), Mepham and Mepham fringe The on Indian the state Sundarbans of West (21°31′00″ Bengal spreading N - 22°30′00″ over the N, (1984), Tomlinson (1986), Naskar and Guha Bakshi major88°10′00″ portion E - 89°51′00″ of the districts E) is located of North on the 24-Parganas southern and South 24-Parganas. The region is bordered by eco-physiological attributes. Different approaches were Harinbhanga-Raimangal river along the International adopted(1987) definedin the process mangroves towards emphasizing classifying the on mangrove different boundary with Bangladesh in the east, the Hooghly River species in different mangrove areas of India, including the in the west, “Dampier- Hodges line” in the North and Indian Sundarbans delta. Bay of Bengal in the south. The Indian Sundarbans delta Regarding the species composition and ecological (declared as Sundarbans Biosphere Reserve under the ‘Man and Biosphere Programme’ in 1989) covers an area several authors opined variedly; viz. 60 species under 41 of 9,630 km2 (Naskar and Mandal 1999) (Figure 1). Of the distinction of mangrove flora in the Indian Sundarbans, mangrove and mangrove associates (Naskar and Guha of the islands support mangrove forests (Chaudhuri and genera and 29 families (Rao 1986), 56 species of euryhaline Choudhury102 islands 1994).in the estuary, The mangrove 54 are inhabited forests of and the the Indian rest

Bakshi 1987) and 69 species under 49 genera and 35 329 Barik and Chowdhury | Mangrove Species of Sundarbans Delta, India

Sundarbans have been estimated between 418, 888 ha.

(IUCN 1989) and 6,749 km2 (Naskar and Mandal 1999). (UNEP 1985 (unpublished data)), 200,000-300,000 ha. arises from the fact that some analyses denote areas designatedThe discrepancy as forest in thelands figures (e.g. including for forest waterways cover possibly and degraded forest) while others represent an assessment of the tree-covered areas only (Chaudhuri and Choudhury 1994).

Methodology The present work is a species list for the true mangroves in Indian Sundarbans, following a set of morpho-physiological features (Figure 2) as regard their adaptation in the saline-tidal zone. The authors incorporated both the previous works (as literature

survey) as well as field surveys. Field surveys for two (Figureyears: 2010 1), and taking 2011 into involved account sampling the adaptiveof mangrove features flora consideredin Eastern, Centralin the present and Western case for parts being of truethe Sundarbansmangroves. The adaptive features considered here were followed after Tomlinson (1986). Voucher specimens were deposited in

bythe theCentre authors for Biodiversity in consultation and Ecological with various Studies, mangrove India. specialists.Identifications IUCN were statuses carried were out taken at the from specific the IUCN category Red Figure 1. List of Threatened Species, Version 2011.2 (2012). present study. A satellite image of India Sundarbans; W, C and E represent Western, Central and Eastern parts of Indian Sundarbans under the

Figure 2. Consideration of key morpho-physiological features for being true or major mangroves, with a list of species qualifying for major counterparts of Indian Sundarban mangroves. The list of species follows the same order as in Table 1.

330 Barik and Chowdhury | Mangrove Species of Sundarbans Delta, India

Figure 3. Graphical representation of the percentage of richness in genera and species of mangrove families in Indian Sundarbans pertaining to true mangroves.

Results the “true mangrove family” (Duke et al. 1998), shows the richest assemblage in most of the mangrove ecosystems of total of 24 species of true or major mangroves were the world by having a myriad of adaptive specializations, as recordedFollowing in the the Indian literature Sundarbans review (Table and field 1 and survey, Figure a also evident in the present case of Sundarbans ecosystem 2). The present species list comprises of nine species in four genera belonging to Rhizophoraceae family; three viviparous germination in members of Rhizophoraceae species in one genus to Sonneratiaceae; three species in(Figure Sundarbans 2). Features provide like mechanical stilt roots support (Figure 5F) towards and in one genus under Avicenniaceae; three species in two substrate instability as well as increased survivability of genera under Meliaceae; two species in two genera under saplings. Palmae/Arecaceae; and one species in one genus each under Combretaceae, Plumbaginaceae, Sterculiaceae and Discussion Myrcenaceae (Figure 3). Mangrove ecosystems are threatened globally due to As the present article deals with species-level taxa their widespread resources which are utilized for human of true mangroves in Indian Sundarbans, varieties of Avicennia marina Vierh., viz. A. marina var. marina (Forsk. overexploitation of resources and conversion to other Vierh) and A. marina var. acutissima Stapf. & Mold. ex Mold., use. In the Asia-Pacific region, non-sustainable utilization, as proposed by Naskar and Mandal (1999) were hence infrastructure development and paddy cultivation are excluded from the species list. Excoecaria agallocha Linn., drasticallyland-uses principally reducing for these fish resource ponds, human bases settlements, at a very a widely noted mangrove-associate or even a marginal alarming rate (Umali et al. 1987). In Indian Sundarbans, the species (Askornkeae et al. 1992) that has been included principal problems hindering sustainable management of under the true mangroves by Mandal and Nandi (1989) and the mangrove ecosystem is land acquisition by reclamation Naskar and Mandal (1999) has also been excluded in the for settlement and expansion of agriculture resulting from present study. Besides, considering the salient characters population pressure (Burbridge 1984 (unpublished data)). (for being true mangroves) adopted here (Figures 2, 4 and Of the twenty-four true mangrove species in Sundarbans, E. agallocha woody in nature and having snake roots, which seemed their conservation importance (IUCN, 2011). While inadequate5), to meet qualified the criteria only for for two being characters, true mangroves, by being Sonneratiafive species griffithii are globally Kurz. isconsidered critically endangered, important regarding Heritiera as also suggested by Askornkeae et al. (1992). Likewise, fomes Buch. Ham. (locally revered and called as Sundari) Porteresia coarctata (Roxb.) Takeoka, Acanthus ilicifolius is considered endangered. The remaining three species, (L.), A. volubilis Wall. and Scyphiphora hydrophyllacea viz. Ceriops decandra Ding Hou, Aegialitis rotundifolia Gaertn. F. are also mentioned as true mangroves by Mandal Roxb. and Phoenix paludosa Roxb. are near threatened. and Naskar (2008), but are here also excluded from the Sonneratia caseolaris present list as they too did not qualify for most of the enlisted in IUCN Red List (IUCN, 2011). The present study aforementioned characters. All these species, however, has illustrated an indexing Engler, system, however and highlighted has not yet how been the were found to have salt-tolerant mechanisms, but as long debated distinction of true or major mangroves from mangrove-associates (Giesen et al. 2006; Sengupta and minor and mangrove-associate species can be determined Lahiri Majumdar 2010). on common adaptive characters. It may further help in Of the nine families in Sundarbans, Rhizophoraceae preparing or revising species lists of different mangroves, shows the maximum richness in taxa at both genus and which in turn can support development of policy towards species level (Figure 3); this family, often referred to as mangrove conservation in India.

331 Barik and Chowdhury | Mangrove Species of Sundarbans Delta, India

Figure 4. The mangrove forest of Indian Sundarbans, showing the woody nature of the true mangrove plants.

Table 1. A list of true mangrove species from Indian Sundarbans Region with their IUCN status.

FAMILY GENUS SPECIES VOUCHER NO. IUCN STATUS cylindrica Blume Least Concern gymnorhiza Lamk. Least Concern Bruguiera CBES403 parviflora Wt. and Arn. Least Concern CBES456 sexangula Poir Least Concern CBES459 Rhizophoraceae decandra Ding Hou /roxburghiana Arn. Near Threatened Ceriops CBES460 tagal Robinson/candolleana Robinson Least Concern CBES471 apiculata Blume/conjugata Arn. Least Concern Rhizophora CBES472 mucronata Lamk. Least Concern CBES507 Kandelia candel Druce Least Concern CBES549 apetala Buch. Ham. Least Concern CBES664 Sonneratiaceae Sonneratia caseolaris Not Listed CBES692 griffithii Kurz. Engler CBES598 Combretaceae Lumnitzera racemosa Willd. Least Concern CBES538 Critically Endangered granatum Koen Least Concern Xylocarpus CBES612 Meliaceae mekongensis Pieree Least Concern CBES588 Aglaia cuculata Pellegrin CBES476 alba Blume Least Concern CBES440 Data Deficient Avicenniaceae Avicennia marina vierh. Least Concern CBES518 officinalis L. Least Concern CBES432 Plumbaginaceae Aegialitis rotundifolia Roxb. Near Threatened CBES504 Sterculiaceae Heritiera fomes Buch. Ham. CBES621 Myrsinaceae Aegiceras corniculatum Blanco Least Concern CBES556 Endangered Nypa fruticans Wumb. Least Concern Palmae/Arecaceae CBES484 Phoenix paludosa Roxb. Near Threatened CBES579 CBES614

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Figure 5. Bruguiera sexangula, (b) Salt crystals on the leaf of Aegialitis rotundifolia, (c) Viviparous germination in A. rotundifolia, (d) Pneumatophores in Avicennia officinalis, (e) Knee roots in Xylocarpus Representative mekongensis, (f) images Stilt roots of adaptive in Rhizophora features mucronata for true mangroves, (g) Snake rootsin Indian in Ceriops Sundarbans: decandra (a), (h)Succulent Root buttress leaves inof X. mekongensis.

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Received: September 2013 Kolkata: Zoological SurveyTropical of India. Ecology 116 pp. Accepted: March 2014 Mandal R.N. and K.R. Naskar. 2008. Diversity and classification of Indian Published online: May 2014 mangroves: a review. 49(2): 131–146. Editorial responsibility: Paul A. Egan

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