Shift in phytoplankton community structure strongly linked with physico-chemical parameters. Re-appearance of Triceratium sp.(polyhaline, indicating salinity tolerance) across sampling locations.

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 DISCUSSION
Rising atmospheric carbon dioxide (CO2)
 Natural phytoplankton assemblages across all the study sites were found to be overwhelmingly dominated by
concentration is causing global warming and ocean
acidification, which increasingly are recognized as members of Bacillariophyceae (28 genera; 16 Centric and 12 Pennate forms) followed by Dinophyceae (5 genera).
Mooriganga estuary
important 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 and
Sundarbans located on the southern fringe of West Skeletonema; while for dinophytes, Ceratium, Dinophysis and Peridinium were dominant throughout the study period
Bengal at the apex of the Bay of Bengal has been (Fig 2).
Chemaguri creek
reported undergoing changes in the water quality.  Major phytoplankton functional groups at the generic level showed seasonal variation with shifts in hydrographical
Plankton, 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 study
the 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 polymorphus
for studying the natural phytoplankton assemblages
(centric diatom) at the amino acid level respectively, while clones L12 and L14 showed 97% & 99% identity with rbcL
across 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 nutrient
parameters 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 area
PCR-clone library approach based on key functional
genes (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 of
attempted for studying the molecular dynamics of the study period. phytoplankton cell densities. However, in late spring and
phytoplankton assemblages. Natural phytoplankton a
250 summer pico-phytoplankton cells were abundant that may
assemblages across all the study sites are found to
have contributed to gross Chlorophyll-a concentrations.
Micro molar
be overwhelmingly dominated by members of 200 Silicate Also, in winter phytoplankton assemblages consisted of
Bacillariophyceae followed by Dinophyceae. Chaetoceros sp. Thalassionema sp. Cyclotella sp.
differential size groups which might have contributed
Picoplankton 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 evaluation
variation with shifts in physico-chemical parameters
50 of large, short-term changes in phytoplankton community
and nutrient concentrations. Water temperature and
Pleurosigma sp. Thalassiosira sp. Coscinodiscus sp. composition.
pH values coupled with phytoplankton community 0
dynamics in the present study show significant 200
variation 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. 150
Preliminary results from the clone library approach
3
m)
Micro molar
indicate the presence of several novel phytoplankton 100
lineages possibly playing an important role in Nitrate
nutrient metabolism including in carbon cycling. This
50
study is a part of an ongoing investigation to
2
0
understand how phytoplankton communities may
respond to changes in aquatic carbon chemistry in 500 P1 P2 P3 P4
Net-phytoplankton
the Sundarbans.
1
400
Phosphate b
cell/100ml
INTRODUCTION 300
0 200
Mangrove ecosystems are threatened globally
due to climate change¹. The Indian 100
c
Sundarbans has not been spared from the 0
pH
impacts of climate change. The objectives of
the 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 29
using phytoplankton as proxies. A PCR-clone Sampling weeks
library approach based on key functional HIGHLIGHTS
genes (NR and RUBISCO) involved in nitrogen
40  Shift in phytoplankton community structure strongly linked with physico-chemical
and 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 a
Systematic 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
10
undertaken 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 of
February, 2011), from four geographic stations 0 pico-phytoplankton in biogeochemical cycling using laboratory and field based
in and around the Sagar Island of Indian
Sundarbans (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 REFERENCES
from 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 World
amplified 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.