Comparative Analysis of Phytoplankton Composition and Abundance over a Two-Decade Period at the Land–Ocean Boundary of a Tropical Mangrove Ecosystem     

Haimanti Biswas  Mitali Dey  Dipnarayan Ganguly  Tarun K. De  Sandip Ghosh  Tapan K. Jana 《Estuaries and Coasts》2010,33(2):384-394

Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′ N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007. Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered by long-term changes in climate.  相似文献   

Dynamics of intensification of the boreal summer monsoon flow during IOD events   总被引：1，自引：0，他引：1  

Suchithra Sundaram  R. Krishnan  Ayantika Dey  P. Swapna 《Meteorology and Atmospheric Physics》2010,107(1-2):17-31

The present study focuses on understanding the dynamics of intensification of the boreal summer monsoon cross-equatorial flow generally observed during positive-Indian Ocean Dipole (IOD) events, by taking 1994 as a case study. In particular, the influence of the anomalous divergent motions during 1994 (i.e., east–west circulation over equatorial Indian Ocean and the monsoon Hadley-type circulation) on the intensification of summer monsoon cross-equatorial flow is investigated. This problem is examined using diagnostic analyses and simulation experiments from a multi-level global atmospheric model forced with observed diabatic heating. The results suggest that the transfer of kinetic energy (KE) from the divergent motions to the rotational flows can be very effective during IOD periods like 1994; and provides a plausible explanation for the increase of KE of the monsoon cross-equatorial flow over Bay-of-Bengal and adjoining areas. The study also investigates the enhanced activity of westward propagating disturbances observed during 1994 over the monsoon region.  相似文献   

Rapid assessment of community needs and fisheries status in tsunami-affected communities in Aceh Province,Indonesia     

Len R. Garces  Michael D. Pido  Robert S. Pomeroy  Sonny Koeshendrajana  Budi Iskandar Prisantoso  Nurul Ahmad Fatan  Dedi Adhuri  T. Raiful  Syamsul Rizal  Alexander Tewfik  Madan Dey 《Ocean & Coastal Management》2010,53(2):69-79

This paper describes the application of the methodology called Rapid Appraisal of Fisheries Management System (RAFMS) to assess quickly the situation in tsunami-affected coastal fisheries in Aceh Province, Indonesia. As a diagnostic tool, the RAFMS is introduced in terms of its conceptual framework and procedures. The RAFMS was used to appraise the status of the fisheries sector in selected 15 villages. Information generated concerning level of fishing effort, marketing patterns and community perspectives on livelihood options are used as three illustrative examples. The paper also provides some insights in applying the RAFMS methodology in the context of disasters and in the broader context of tropical fisheries management.  相似文献   

Environmental Effects on the Toxicity of Methyl Mercuric Chloride to Chorella vulgaris.     

L. C. Rai  R. Dey 《洁净——土壤、空气、水》1980,8(4):319-327

The effect of different concentrations, viz. 0.01, 0.001 and 0.0001 ppm of methyl mercuric chloride on survival, growth behaviour and chlorophyll content of Chlorella vulgaris has been studied under various environmental conditions. Methyl mercury at 0.01 ppm is 100% toxic to the test alga. At a sublethal (0.001 ppm) dose of CH₃HgCl, Chlorophyll a was more inhibited than Chlorophyll b. Toxicity was found to be very much under the influence of pH as at acid pH growth is highly reduced by a sublethal concentration, whereas the same concentration does not have an inhibitory influence in the alkaline range of pH. Eutrophic waters seem to reduce the heavy metal toxicity in general.  相似文献   

Torsional wave under initial stress     

Sukhendu Dey 《Pure and Applied Geophysics》1972,94(1):53-59

Summary In this paper, the frequency equation for phase velocity of torsional wave in a rod of circular cross section under initial tension has been obtained. The graphs are plotted to compare the velocity with that in the absence of initial tension. Some analytical informations have been obtained for instability of the body under initial compression.  相似文献   

Seismic vulnerability assessment of earthquake-prone mega-city Shillong,India using geophysical mapping and remote sensing     

Saurabh Baruah  Goutam Kashyap Boruah  Sangeeta Sharma  Washim Akram Hoque  Timangshu Chetia  Chandan Dey 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(2):112-127

ABSTRACT

The concept of seismic vulnerability is a yard-stick of damage estimation from a probable earthquake considering physical cum social dimension and enables a basis for decision-makers to develop preparedness and mitigation strategies. We aim at vulnerability assessment of the typical urban system of capital city Shillong situated on hilly terrain. High-resolution satellite imagery of Shillong facilitates analysis of building footprints, communication network, and open ground. Different building typologies are identified taking into account the building’s structural configuration assessed through a rapid visual survey of more than 15% of total residential households. Slope map demarcates the landslide-prone area through discrete elevation modelling. A methodology incorporating several parameters e.g. building typology, slope angle, shear wave velocity characteristics, geomorphology, and the number of occupants in correlation with a physical measurement of vulnerability is presented and is applied to estimate the dimension of vulnerability. Additionally, MASW survey indicates lithology up to 30?m deep along with the existence of stiff soil and rocks at different depths whereas resonant frequency is identified to be in the range of 6–8?Hz through H/V ratio. Integrating all, it is observed that more than 60% of Shillong city falls under moderate to higher vulnerability and the rest is less vulnerable.  相似文献   

Spatio-temporal variations in the estimation of PM10 from MODIS-derived aerosol optical depth for the urban areas in the Central Indo-Gangetic Plain     

Shikha Chitranshi  Satya Prakash Sharma  Sagnik Dey 《Meteorology and Atmospheric Physics》2015,127(1):107-121

  相似文献   

Impacts of aerosols on dynamics of Indian summer monsoon using a regional climate model   总被引：1，自引：0，他引：1  

Sushant Das  Sagnik Dey  S. K. Dash 《Climate Dynamics》2015,44(5-6):1685-1697

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Evaluation of Recharge and Groundwater Dynamics of a Shallow Alluvial Aquifer in Central Ganga Basin,Kanpur (India)   总被引：2，自引：0，他引：2  

Anirban Dhar  Satiprasad Sahoo  Saumava Dey  Madhumita Sahoo 《Natural Resources Research》2014,23(4):409-422

Evaluation of recharge and groundwater dynamics of an aquifer is an important step for finding a proper groundwater management scenario. This has been performed on the basis of statistical Kendall Tau test to find a relationship between groundwater levels and hydro-meteorological parameters (e.g., precipitation, temperature, evaporation). Recharge to the aquifer was estimated for identification of critical areas/locations based on the analytical Soil and Water Assessment Tool. Moreover, spatiotemporal variability of groundwater levels has been quantified using space–time variogram. The overall characterization method has been applied to the shallow alluvial aquifer of Kanpur city in India. The analysis was performed using groundwater level data from 56 monitoring piezometer locations in Kanpur from March 2006 to June 2011. Groundwater level shows relatively higher correlation with temperature. Performance of the geostatistical model was evaluated by comparing with the observed values of groundwater level from January 2011 to June 2011 for two scenarios: “with limited spatiotemporal data” and “without spatiotemporal data.” It is evident that spatiotemporal prediction of groundwater level can be performed even for the unmonitored/missing data. This analysis demonstrates the potential applicability of the method for a general aquifer system.  相似文献   

Experiment on visualizing micro-level surface characters of sediment sections: a methodological approach to reflectance-based alternative petrographic image analysis   总被引：1，自引：1，他引：0  

Sudip Dey  Chandrani Debbarma  Prasamita Sarkar  Muh Aris Marfai 《Arabian Journal of Geosciences》2011,4(5-6):899-906

This paper discusses an experiment on digital imaging and visualizing the surface condition of the sediment depositions. For that purpose, a part of South Tripura district was selected as sampling site. Physically, the selected area is located in a fold belt and preserves the history of Tertiary–Quaternary landform evolution in the main types of sediment depositions. Three samples, each from the different types of Tertiary depositions, were finally taken for thick section making, optical microscopy under reflected light, and soft computing. Geometric optical measurement and physical optical measurement were done to understand the surface condition of Bokabil, Tipam, and Duplitila samples by bidirectional reflectance distribution function and radiometric scales (within 0–255 digital number values). Maximum surface smoothness or near-perfect reflection surface was measured by brightness–contrast slicing operation.  相似文献