Manna Suman, Chaudhuri Kaberi, Bhattacharyya Somenath, Bhattacharyya Maitree
Institute of Environmental Studies and Wetland Management, DD-24, Sector-I, Salt lake, Kolkata-700064, India.
Department of Biochemistry, University of Calcutta, 35, B.C. Road, kolkata-700019, India.
Saline Syst. 2010 Aug 11;6:8. doi: 10.1186/1746-1448-6-8.
Sundarbans is the largest chunk of mangrove forest and only tiger mangrove land in the world. Compared to the rich species diversity and uniqueness, very few studies have so far been conducted here, mainly due to its inaccessibility. This study explores water quality, density of biomass, species diversity, phytoplankton abundance and bacterial population of a tidal creek in Sunderban estuary during the post and pre monsoon period of 2008-09.
Phytoplankton community was observed to be dominated by diatoms (Biacillariophyceae) followed by Pyrrophyceae (Dinoflagellates) and Chlorophyceae. A total of 46 taxa belonging to 6 groups were recorded. Other algal groups were Cyanophyceae, Euglenophyceae and Chrysophyceae. Species diversity was highest in summer (March) and lowest in winter season (November) in all the sample stations indicating its close correlation with ambient temperature. Species evenness was fairly high in all five stations throughout the study period. Present study indicated that dissolved oxygen, nutrients and turbidity are the limiting factors for the phytoplankton biomass. The estuary was in eutrophic condition (Chlorophyll-a >/=10 mug/L) in winter. During the month of May phytoplankton biomass declined and at high salinity level (21.2PSU) new phytoplankton species take over, which are definitely better resilient to the high saline environment. Bio-indicator species like Polykrikos schwartzil, Dinophysis norvegica and Prorocentrum concavum points to moderately polluted water quality of the estuary.
Eutrophication as well as presence of toxic Dinoflagellates and Cyanophyceae in the tidal creek of Sundarban estuary definitely revealed the deteriorated status of the water quality. The structure and function of the mangrove food web is unique, driven by both marine and terrestrial components. But little attention has been paid so far to the adaptive responses of mangrove biota to the various disturbances, and now our work unfolds the fact that marine status of Sundarban estuary is highly threatened which in turn will affect the ecology of the mangrove. This study indicates that ecosystem dynamics of the world heritage site Sundarban may facilitate bioinvasion putting a question mark on the sustainability of mangroves.
孙德尔本斯是世界上最大的红树林区域，也是唯一有老虎栖息的红树林地带。与丰富的物种多样性和独特性相比，到目前为止，这里开展的研究极少，主要原因是其难以进入。本研究探讨了2008 - 2009年季风后和季风前时期孙德尔本斯河口一条潮汐小溪的水质、生物量密度、物种多样性、浮游植物丰度和细菌种群。
观察到浮游植物群落以硅藻（硅藻纲）为主，其次是甲藻纲（鞭毛藻）和绿藻纲。共记录了属于6个类群的46个分类单元。其他藻类类群为蓝藻纲、裸藻纲和金藻纲。在所有采样站，物种多样性在夏季（3月）最高，在冬季（11月）最低，表明其与环境温度密切相关。在整个研究期间，所有五个站点的物种均匀度都相当高。目前的研究表明，溶解氧、营养物质和浊度是浮游植物生物量的限制因素。该河口在冬季处于富营养化状态（叶绿素 - a≥10微克/升）。在5月份，浮游植物生物量下降，在高盐度水平（21.2PSU）下，新的浮游植物物种取而代之，这些物种对高盐环境的适应能力肯定更强。像施氏多环旋沟藻、挪威裸甲藻和凹形原甲藻等生物指示物种表明该河口水质受到中度污染。
孙德尔本斯河口潮汐小溪的富营养化以及有毒鞭毛藻和蓝藻的存在，明确显示了水质的恶化状况。红树林食物网的结构和功能独特，由海洋和陆地成分共同驱动。但到目前为止，红树林生物群对各种干扰的适应性反应很少受到关注，现在我们的研究揭示了孙德尔本斯河口的海洋状况受到高度威胁，这反过来又会影响红树林的生态。本研究表明，世界遗产地孙德尔本斯的生态系统动态可能会促进生物入侵，这给红树林的可持续性打上了一个问号。
