Papers by Biswajit Biswas
SpringerPlus, 2016
Background Mangroves and estuaries are ecosystems known to be extremely sensitive to environmenta... more Background Mangroves and estuaries are ecosystems known to be extremely sensitive to environmental fluctuations and are under perpetual stress because of varied reasons, and are thus particularly vulnerable to climate change. Significant environmental factors that affect the structure and function of these systems are expected to be sensitive parameters of global climate change and contribute to our understanding of the implications that such changes may have in the area under study. The present study area-the Sundarbans, is an interesting ecosystem for studying such changes. Planktoniella Schutt is essentially a warm water diatom reported from tropical waters of marine and estuarine systems (
Journal of the Bombay Natural History Society, 2015
Species constituting diatom assemblages in sediments provide important information regarding the ... more Species constituting diatom assemblages in sediments provide important information regarding the past and present environmental conditions related to soil and water physico-chemistry and also biodiversity dynamics data. This information can reveal the developmental history of the region. Diatoms are sensitive to stochastic changes in the environment, making them extremely reliable bio-indicators. The purpose of the present study was to decipher such biodiversity related information provided by the diatom assemblages from the Indian Sundarbans. Diatoms were identified in the top 50 cm layer of two sediment cores: a newly silted up deltaic landmass with mangroves in early succession stage, and an island within the Protected Area Network with mangroves in late succession stage. Fifteen diatom species, with no past records in the sediments of Indian Sundarbans were identified and described. Four species among them are sporadically mentioned in previous phytoplankton records from the Sundarbans, but these are not confirmed taxonomically. This paper provides identification and nomenclatural notes on all 15 species. High abundance and species richness of the centric forms Coscinodiscus spp., Cyclotella spp., and Thalassiosira spp. at both the sites is attributed to their proximity to estuarine rivers and their regular inundation, leading to settling of planktonic forms within sediment cores. Many pennate forms, namely Amphicampa eruca, Amphora holsatica, Diploneis spp. (except D. smithii), Epithemia turgida, Eunotia pectinalis, Giffenia cocconeiformis, and Rhaphoneis rhombus which are being reported for the first time from this region have never been part of described planktonic communities in estuarine waters, validating their ‘soil diatom’ status. Typical freshwater diatoms, namely Aulacoseira granulata and Epithemia turgida, in the sediments indicate lower salinity in these areas, not much earlier than present times.
Epilithic diatoms from three geographically isolated hill streams of Central and Eastern India we... more Epilithic diatoms from three geographically isolated hill streams of Central and Eastern India were studied and analysed to find their efficacy in determining differences in ecological conditions of the aquatic systems considered. The three sampling sites (site-1, site-2 and site-3) share the commonness of being hill streams of forests with differences in source points. 34 diatom species were identified with species-richness of 17 at site-1, 10 at site-2 and 19 at site-3. Two sets of hypotheses – null (H01, H02 & H03) and alternative (HA1, HA2 & HA3) were framed. The null hypotheses were rejected in favour of alternative hypotheses. Diversity t-tests yielded significant ‘t’ values: at α<0.0001 and <0.002, implying differences within the sampling sites. Furthermore, Mann-Whitney, Kruskal-Wallis and Wilcoxon paired-sample tests were performed to test the alternative hypotheses, of which Kruskal-Wallis yielded significant difference between the sample medians with χ2=5.457 at p=0.03801 and Wilcoxon paired-sample test yielded significant differences between sampling site pairs at α(2)=0.05 & 0.10. Thus significant differences could be established based only on diversity profile study of the epilithic diatoms.
The study highlights the dynamics and morphological characteristics of the Genus Planktoniella Sc... more The study highlights the dynamics and morphological characteristics of the Genus Planktoniella Schutt. The two available species P. sol (Wallich) Schutt. and P. blanda (Schmidt) Syvertsen and Hasle are important components of the phytoplankton assemblage in the estuarine system of Indian Sundarbans and also marine systems elsewhere. The sampling sites for the purpose of this study include four different spots
along a riverine stretch in the estuarine region adjacent to the Tiger Reserve in the Indian Sundarbans flowing into the Bay of Bengal. Integrated phytoplankton samples were preserved for the purpose from composite water samples from each site. The
water samples were analysed in field for determining pH, temperature, salinity, conductivity, TDS, turbidity and DO and subsequent to treatment and processing, the samples were microscopically analysed in the laboratory. Significant negative correlation of cell count of both species found with respect to temperature and turbidity. P. sol versus temperature (significant at α = 0.01, p = 0.001) and P. blanda versus temperature (significant at α = 0.05, p = 0.037); P. sol versus turbidity (at α = 0.05, p = 0.019) and P. blanda versus turbidity (at α = 0.05, p = 0.019). Significant positive correlation found
with respect to DO and as correlation between the two species themselves. A model has been generated for each of the two species with temperature, turbidity and DO as predictor variables and the two species of Planktoniella as response variables. The influence of other dominant phytoplankton in the samples has also been considered with Pearson correlation computed for each set of species.
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Papers by Biswajit Biswas
along a riverine stretch in the estuarine region adjacent to the Tiger Reserve in the Indian Sundarbans flowing into the Bay of Bengal. Integrated phytoplankton samples were preserved for the purpose from composite water samples from each site. The
water samples were analysed in field for determining pH, temperature, salinity, conductivity, TDS, turbidity and DO and subsequent to treatment and processing, the samples were microscopically analysed in the laboratory. Significant negative correlation of cell count of both species found with respect to temperature and turbidity. P. sol versus temperature (significant at α = 0.01, p = 0.001) and P. blanda versus temperature (significant at α = 0.05, p = 0.037); P. sol versus turbidity (at α = 0.05, p = 0.019) and P. blanda versus turbidity (at α = 0.05, p = 0.019). Significant positive correlation found
with respect to DO and as correlation between the two species themselves. A model has been generated for each of the two species with temperature, turbidity and DO as predictor variables and the two species of Planktoniella as response variables. The influence of other dominant phytoplankton in the samples has also been considered with Pearson correlation computed for each set of species.