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Dynamics of natural phytoplankton assemblages in the Indian Sundarbans assemblages in the Indian Sundarbans: An integrated Approach


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Shift in phytoplankton community structure strongly linked with physico-chemical parameters.

Re-appearance of Triceratium sp.(polyhaline, indicating salinity tolerance) across sampling locations.

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Dynamics of natural phytoplankton assemblages in the Indian Sundarbans assemblages in the Indian Sundarbans: An integrated Approach

  1. 1. DYNAMICS OF NATURAL PHYTOPLANKTON ASSEMBLAGES IN THE INDIAN SUNDARBANS: AN REPLACE THIS BOX INTEGRATED APPROACH WITH YOUR ORGANIZATION’S Dola Bhattacharjee1, Brajogopal Samanta1, Amit Kumar1, Anurag Danda2 and Punyasloke Bhadury1 HIGH RESOLUTION ¹Integrative Taxonomy and Microbial Ecology Group, Department of Biological Sciences, Indian Institute of Science Education and Research-Kolkata LOGO (IISER-K), Mohanpur Campus, Mohanpur-741252, Nadia, West Bengal, India. ²Sundarbans Programme and Climate Adaptation (Coastal Ecosystems), WWF-India, Kolkata- 700029, West Bengal, India. ABSTRACT RESULTS AND DISCUSSIONRising atmospheric carbon dioxide (CO2)  Natural phytoplankton assemblages across all the study sites were found to be overwhelmingly dominated byconcentration is causing global warming and oceanacidification, which increasingly are recognized as members of Bacillariophyceae (28 genera; 16 Centric and 12 Pennate forms) followed by Dinophyceae (5 genera). Mooriganga estuaryimportant drivers of change in biological systems Pico-phytoplankton and Cyanobacterial communities have been also detected as part of the study.including in mangrove ecosystems. The Indian  Numerically important diatom genera were Coscinodiscus, Thalassiosira, Cyclotella, Chaetoceros andSundarbans located on the southern fringe of West Skeletonema; while for dinophytes, Ceratium, Dinophysis and Peridinium were dominant throughout the study periodBengal at the apex of the Bay of Bengal has been (Fig 2). Chemaguri creekreported undergoing changes in the water quality.  Major phytoplankton functional groups at the generic level showed seasonal variation with shifts in hydrographicalPlankton, in particular phytoplankton are excellent parameters and nutrient concentrations (nitrate, phosphate and silicate) in the water column (Fig 3, a-d).indicators to study the impact of climate change in  Surface-water temperature and pH values coupled with phytoplankton community dynamics in the present studythe Sundarban aquatic ecosystems. Since March of varied when compared with previous studies indicating possible changes in the eco-region.2010 we are undertaking systematic weekly sampling  Clone L7 and L15 sequences showed 100% & 99% identity with rbcL sequence of Minutocellus polymorphusfor studying the natural phytoplankton assemblages (centric diatom) at the amino acid level respectively, while clones L12 and L14 showed 97% & 99% identity with rbcLacross four sites in the Sagar Island of Indian sequence of Amphora coffeaeformis (pennate diatom) at the amino acid level respectively.Sundarbarns. Key physico-chemical and nutrientparameters are measured as part of the study. A Preliminary results from the clone library approach indicate the presence of novel phytoplankton lineages possibly playing an important role in nutrient metabolism including in carbon and nitrogen cycling across the sampling Fig 1. Study areaPCR-clone library approach based on key functionalgenes (NR and RUBISCO) involved in nitrogen and locations.carbon metabolism in phytoplankton has been also Fig 3. Variation in physico-chemical parameters and nutrient concentration along Fig 2. Dominant diatoms from the study area.  Shift in Chlorophyll-a concentration over the study 300 period matched with that of the dynamics ofattempted for studying the molecular dynamics of the study period. phytoplankton cell densities. However, in late spring andphytoplankton assemblages. Natural phytoplankton a 250 summer pico-phytoplankton cells were abundant that mayassemblages across all the study sites are found to have contributed to gross Chlorophyll-a concentrations. Micro molarbe overwhelmingly dominated by members of 200 Silicate Also, in winter phytoplankton assemblages consisted ofBacillariophyceae followed by Dinophyceae. Chaetoceros sp. Thalassionema sp. Cyclotella sp. differential size groups which might have contributedPicoplankton communities have been also detected 150 variably in Chlorophyll-a concentrations (Fig 4, a-b).as part of the study. Generic compositions for major 100  Spectrophotometric pigment (fucoxanthin and peridinin)phytoplankton functional groups show seasonal profiles did provide division-level phylogenetic evaluationvariation with shifts in physico-chemical parameters 50 of large, short-term changes in phytoplankton communityand nutrient concentrations. Water temperature and Pleurosigma sp. Thalassiosira sp. Coscinodiscus sp. composition.pH values coupled with phytoplankton community 0dynamics in the present study show significant 200variation when compared with previous studies 4 b a Fig 4. Phytoplankton dynamics in terms of Chl a concentration and cell abundance. Chl a (mg/cu.indicating possible changes in the eco-region. 150Preliminary results from the clone library approach 3 m) Micro molarindicate the presence of several novel phytoplankton 100lineages possibly playing an important role in Nitratenutrient metabolism including in carbon cycling. This 50study is a part of an ongoing investigation to 2 0understand how phytoplankton communities mayrespond to changes in aquatic carbon chemistry in 500 P1 P2 P3 P4 Net-phytoplanktonthe Sundarbans. 1 400 Phosphate b cell/100ml INTRODUCTION 300 0 200Mangrove ecosystems are threatened globallydue to climate change¹. The Indian 100 cSundarbans has not been spared from the 0 pHimpacts of climate change. The objectives ofthe present study are to track these changes METHODS AND MATERIALS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29using phytoplankton as proxies. A PCR-clone Sampling weekslibrary approach based on key functional HIGHLIGHTSgenes (NR and RUBISCO) involved in nitrogen 40  Shift in phytoplankton community structure strongly linked with physico-chemicaland carbon metabolism in phytoplankton has d (Celcius)/Salinity (psu)been also attempted as part of this study to 35 parameters.complement with the conventional taxonomy. Mean= 29.7 ºC  Re-appearance of Triceratium sp. (polyhaline, indicating salinity tolerance) across Temperature 30 sampling locations. METHODS 25  Detection of Minutocellus polymorphus like rbcL sequences from the study site is aSystematic sampling of phytoplankton 20 new finding in the Indian Sundarbans, as part of molecular diversity studies.assemblages and measurements of related 15  Variations in salinity (0-22 psu), temperature profiles (22°C-34°C), average pH (7.99)physico-chemical parameters were Mean= 11.2 psu and net-phytoplankton cell density (1.2X10³ Lˉ¹) in the study area project changes in 10undertaken since March of 2010, the water quality when compared with previous reports².encompassing 29 weeks (till 1st week of 5  Further, we have initiated detailed investigations towards understanding the role ofFebruary, 2011), from four geographic stations 0 pico-phytoplankton in biogeochemical cycling using laboratory and field basedin and around the Sagar Island of IndianSundarbans (Fig 1). Following standard 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930 experiments in the Indian Sundarbans.protocols functional genes (NR and RUBISCO) Sampling weeks REFERENCESfrom natural phytoplankton assemblages were ACKNOWLEDGEMENTS: We thank Prof. A. Choudhury for scientific guidance, 1. Macintosh, D. J. and E. C. Ashton, 2002. A Review of Mangrove Biodiversity Conservation and Management. Report to Worldamplified and sequenced based on a PCR- WWF-India for funding this project and Director, IISER-Kolkata for providing Bank. Centre for Tropical Ecosystem Research, University of Aarhus, Denmark, 71 pp.clone library Design & Printing by Genigraphics - 800.790.4001 approach. 2. Saha, S.B. , S.B. Bhattacharyya and A. Choudhury, 2001. Photosynthetic activity in relation to hydrological characteristics of a Poster ® the facilities to undertake the study. brackishwater tidal ecosystem of Sundarbans in West Bengal, India. Tropical Ecology, 42, 111-115.