Coast Of India Research Articles

Habitat characteristics mediated partitioning of economically important bivalves in a tropical monsoon-influenced estuary.

Bivalves are benthic organisms inhabiting coastal marine habitats, especially estuarine tidal and mudflats. Due to their high stocking density and rich protein content, they form a major part of the artisanal fishery resource around the world. A clear partitioning in the population of bivalves, Paphia malabarica (Chemnitz, 1782), and Meretrix casta (Gmelin, 1791) in southern (Chicalim) and northern (Siridao) bank of a tropical Zuari estuary influenced by the monsoon along the Indian west coast, is evidenced. This study unravels the reasons for their partitioning in this estuary. Paphia malabarica is an exclusive inhabitant of Chicalim which has silty-sandy sediment, whereas M. casta is exclusive to Siridao, a sandy habitat. Observations showed that this segregation is facilitated by the semi-enclosed nature of habitat at Chicalim with the high amount of degraded and aged sediment organic carbon, high chlorophyll a, elemental, and biochemical components, whereas Siridao experiences the high impact of tidal currents, low sediment organic carbon, and high water column chlorophyll a. The habitat in Siridao gets exposed to UV radiation during low tide, reducing the photosynthetic oxygen production, turning the habitat to periodic anoxia indicated by differences in the TOC:TS ratio. However, such conditions may not influence M. casta, which can derive oxygen from the water column. The fatty acids specific to diatoms, dinoflagellates, higher plants, and partially degraded organic matter in the tissues of P. malabarica indicate their ability to source the food from the sediment and water column, whereas in tissues of M. casta, higher dinoflagellate-specific fatty acids followed by diatom and bacteria indicate water column-derived food. Chicalim can be considered an actively coupled benthic-pelagic habitat, and Siridao as an uncoupled habitat. Thus, the diverse flux of food particles, species-specific feeding ecology, and local hydrodynamics operating at these habitats could be the determining factors in the partitioning of the bivalves. Graphical abstract .

Stock structure analysis of Priacanthus hamrur (Forsskal, 1775) along the Indian coast based on truss morphometry

Marine biology,marine ecology,Phytoplankton, marine algae, zooplankton, nekton, benthos, corals and coral reefs, ecology, zoogeography and systematics, primary production and experimental work on ecosystem including energy flow at different trophic levels, population dynamics and theoretical models, recycling of matter, influence of environmental factors on metabolic activity, marine microbiology, mariculture and experimental work on propagation of cultivable species, biology of fishes, marine reptiles, sea birds and mammals, physical, chemical, geological and meteorological features of the environments related to marine biology, marine environmental damage caused by pollution and engineering works, underwater observations, conservation of living resources, modifications in methodology and techniques and development of new apparatus related to marine sciences

New Record and Range Extension of the Orange Scorpionfish, Neomerinthe amplisquamiceps (Scorpaenidae), in the Coastal Waters of Visakhapatnam, India

In this paper, we report finding of 74 specimens of Neomerinthe amplisquamiceps (Scorpaendiae) and field observations of this species from the Indian coast. Specimens of N. amplisquamiceps were captured between 150 and 300 m depth with a 38 m high speed demersal trawl (crustacean version, codend, mesh size 40 mm) and 46 m Expo model demersal trawl (mesh size 30 mm). This rare, poorly known species is the only member of the genus Neomerinthe in the Indian ichthyofauna. The new records improve the current knowledge on N. amplisquamiceps, and refine the limits of its geographical distribution and habitat preference. Analyses of morphometric and meristic characters confirmed the identity of the specimens and are described, compared and summarized.

Seasonal characteristics of sea breeze and thermal internal boundary layer over Indian east coast region

Characteristics of the sea breeze and thermal internal boundary layer (TIBL) during different seasons are studied using mini micropulse lidar (MPL) at Kattankulathur (12.83° N, 80.04° E, 45 m) and radiosonde and surface meteorological observations at Meenambakkam (13.0° N, 80.06° E, 16 m) during the period January 2016–June 2018 over Chennai, in the Indian east coast region. Study of the sea breeze is important because it is one of the main factors responsible for most of the convective rainfall during summer monsoon season over Chennai. The sea breeze onset occurs from morning ~ 07:00 IST to late afternoon during winter and pre-monsoon seasons whereas it occurs from mid-morning ~ 09:00 IST to late evening ~ 19:00 IST during the summer monsoon and post-monsoon seasons. The cessation of the sea breeze lies between the late evening ~ 18:00 IST and early morning ~ 04:00 IST on the next day. Sea breeze prevails for the longest (shortest) duration during pre-monsoon (summer monsoon) season. The temperature, moisture, refractivity, and aerosol profiles show double mixed layer characteristics indicating TIBL as the first layer and convective boundary layer (CBL) or residual layer (RL) as the second layer. TIBL occurs throughout the year with maximum occurrence during pre-monsoon season. It varies from 0.2 to 0.8 km (0.4–1.0 km) with peak at 0.4 km (0.6 km) over Meenambakkam (Kattankulathur). TIBL height is found to be at altitude ~ 0.54 ± 0.16 km and 0.62 ± 0.13 km at Meenambakkam and Kattankulathur, respectively. TIBL shows a weak seasonal variation with maximum height during winter and minimum height during summer in contrast to the seasonal variation of the CBL.

Evaluation of Matrix Issues in the Applicability of the Neuro-2a Cell Based Assay on the Detection of CTX in Fish Samples.

Ciguatoxins (CTXs) are a group of neurotoxins responsible for the syndrome ciguatera fish poisoning (CFP) as a result of the consumption of contaminated fish. The presence of these toxins has been detected around the Pacific, Caribbean and Indian coasts. Recent reports indicate the emergence of CFP in other geographic areas, in particular in European coasts, of the Canary Islands (Spain) and Madeira (Portugal). A neuroblastoma cell line of murine origin (N2a) has been applied to assay different groups of neurotoxins, acting on voltage-gated sodium channel (VGSC) of excitable cells, N2a-MTT. The great potential of N2a-MTT as a sensitive tool for the CTXs screening is clearly recognized, notably because it allows the detection of these toxins at levels below recommended as security levels. However, the complexity of the matrix is a critical point on the application of N2a-MTT, which needs to be evaluated. The aim of this work is to provide recommendations for an implemented N2a-MTT method for CTXs determination in fish that avoids matrix effects, particularly those related to high lipid content.

Salt marsh vegetation in India: Species composition, distribution, zonation pattern and conservation implications

Salt marshes are one among the most productive coastal ecosystems, mostly confined to low-energy coasts of temperate and high latitude. Tropical and sub-tropical salt marshes are generally less studied. The present study attempts to assess the status of salt marsh vegetation along the Indian coast regarding its species composition, density, and zonation pattern. Satellite images were used to map salt marshes along the coastal region and to perform field surveys for status assessment at selected sites between November 2014 and July 2018. The total extent of salt marshes in India is estimated as about 290 km2. A total of 14 salt marsh species are found distributed along the Indian coast, belonging to 11 genera under six families. The most diverse family is represented by Amaranthaceae. The overall mean density of salt marsh vegetation is estimated to be 19 ± 1 plants per m2 with the highest density recorded in Lakshadweep (28 m−2) followed by Tamil Nadu (23 m−2), West Bengal (19 m−2), Maharashtra (18 m−2), Andhra Pradesh (17 m−2), Gujarat (15 m−2) and Puducherry (10 m−2). The zonation pattern of salt marsh vegetation in pure stands is detailed from observations. Conservation implications on salt marshes have been discussed. This study provides insight into salt marshes in the tropical environment.

Mineralogical composition and C/N contents in soil and water among betel vineyards of coastal Odisha, India

The Piper betle L. leaves and their significance were described in various ayurvedic studies of India and China for its diverse use in cultural practices and treatment of various health disorders. The leaves of P. betle were used as post-meal mouth freshener in India for centuries. However, it offers economic benefits to farmers of Coastal India at large. Betel leaves cultivated agricultural soils play a significant role for their mineralogical composition. So, this present study aimed to find out the soil physicochemical characteristics and C/N contents of Betel vineyards of coastal Odisha. The soil and water samples were collected from local varieties of P. betle L. cultivated vineyards of Balasore, Ganjam, and Puri districts of Odisha and investigated their mineralogical composition. The soil mineralogy plays crucial role to understand the soil–plant relations. Coastal soil samples also contain the most prized mineral aggregations from economical perspectives. The mineralogical composition involves chemical composition, essential elemental composition, and surface morphology. The mineralogical and elemental composition of soil samples were carried out by using various techniques like Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray fluorescence, scanning electron microscopy attached with energy-dispersive X-ray system. CHNS analyzer for quantification of hydrogen, nitrogen, carbon, and sulfur content. H2O2 (30%)-treated soil is employed to eliminate the organic carbon from mass soil samples. The scanning electron microscopy analysis revealed the presence of heterogeneity shape and size of surface soils of both treated and untreated soils. For estimation of total organic carbon (TOC), inorganic carbon, total nitrogen, and total carbon, water samples were analyzed through TOC analyzer. Percentage variation arises in GAN and PUR sites soil due to more assumption of organic matter from clay soils in comparison with sandy soils of BAL. The spectra of FTIR point out Kaolinite and Quartz as the key components and others are minor components. The common minerals like quartz, hematite, kaolinite, montmorillonite, calcite, organic matter and illite in diverse compositions are recognized. Further, the presence of these above minerals was confirmed by the XRD analysis. Morphological analysis of kaolinite indicated euhedral, hexagonal, and pseudo-hexagonal-shaped plates. The mineralogical data revealed the relative abundance of phosphorus and nitrogen was less in all soils. Depletion of P and N may be resulted due to introduction of fresh plowed soil from grazed pastoral land. The present research uncovers that soils requires adequate input of additional compost, manures, and fertilizers for maximal vegetative growth and economic yield as well. As P. betle species is very precious medicinal plant, and this research suggested not to use contaminated water for betel cultivation. Our results also helpful for the improvement in soil management in the vineyards to determining the mineral nutrients that affect plant growth and development.

Experimental Investigation of a Bidirectional Impulse Turbine for Oscillating Flows at Various Resistive Loads

A bidirectional impulse turbine is a self-rectifying air turbine used in an oscillating water column wave energy converters. Most of the study on bidirectional impulse turbines involves steady-state performance analysis; however, the performance under oscillating airflow conditions is necessary to understand its behavior. The objective of this study is to experimentally analyze an optimized and numerically investigated bidirectional impulse turbine with fixed guide vane subjected to oscillating airflow conditions. A bidirectional airflow test facility developed at Indian Institute of Technology Madras, Chennai, India is employed to determine the aerodynamic characterization of the turbine and the dynamics involved in each of the coupling stages. The test rig consists of a piston chamber assembly, which provides different airflow rates by varying the stroke length (SL) and cycle time. Emphasis is made on the pressure and flow rate coefficients of the turbine, turbine-generator coupling, and power developed for different input conditions. The operating range of the turbine is mapped for four different frequencies and three SLs. Different electrical loading and the power output were analyzed for accelerations and decelerations of inflow and outflow. The preliminary dynamic characterization of the turbine with respect to nondimentionalized pressure coefficient and flow coefficient was determined for inflow and outflow. The power output is found to be in strong correlation with the flow rate and angular rotation of the rotor. The turbine analyzed in the experimental test rig will be proceeded with real sea testing on the Indian coast by the National Institute of Ocean Technology, Chennai, India.

Observed variability of the East India Coastal Current on the continental shelf during 2010–2018

Observed variability of the East India Coastal Current on the continental shelf during 2010–2018

Fishery and estimation of Potential yield for Bombayduck Harpodon nehereus along Gujarat coast, India

Bombayduck Harpadon nehereus (Hamilton, 1822) is one of the key fishery resources landed along the Indian coast with uniqueness in distribution and exploitation. The resource is known for discontinuous distribution, majorly along the north-west and north-east coasts of India. Gujarat is the lead state to contribute nearly 64.72% (72,949 t) to the total national landings of the resource (11,2705 t) in 2018. Dolnet gear contributes nearly 95% of the total landings of the resource in the region. The landings and the corresponding catch per unit effort (CPUE) showed a fluctuating trend over the study period of 1994-2014. The catches fluctuated between 35,235 t (2016) and 92,188 t (2004), whereas the CPUE oscillated in the range of 15 to 20 kg h-1 (1998) and 30.76 kg h-1 (2003). The period of 1994-2000 was the most productive period with an average catch of 72,133 t, whereas the succeeding decade was the leanest phase with an average annual catch of 50,035 t. The estimated potential yield (= maximum sustainable yield, MSY) was estimated at 73,700 t and 70,108 t using the Bayesian surplus production model (CMSY & BSM) and basic Schaefer surplus production model respectively. The present catch and exploitation levels were found to be close to the optimum level and a further increase in effort for the resource is not recommended.

MAXIMUM SUSTAINABLE YIELD OF TRAWL FISHERY ALONG THE SOUTH-WEST COAST OF INDIA: BAYESIAN ESTIMATION APPROACH

The south-west region of the Indian coast is shared by three maritime states and it contributes nearly 32% to the total marine fish production of the country. Mechanised trawl fishery accounts for 44% of the marine fish harvest in the south-west coast and a number of resources are harvested by trawl nets from this region. An assessment of the trawl fishery to determine sustainable harvest levels for mechanised trawlers in the region was carried out using time series data on annual landings and fishing effort of mechanised trawlers during the period 1990-2015. A Bayesian estimation method for Schaefer model was used for the analysis. Posterior probability densities of parameters of the model, maximum sustainable yield (MSY) and corresponding biomass were obtained through Bayesian estimation for the trawl fishery in south-west coast and the harvest levels were found to be above MSY from 2012 onwards. Forecasts of biomass and fish landings by mechanised trawlers upto 2025 under different levels of fishing effort were also simulated using the model to study the dynamic changes over time. It was found that the numbers of multiday trawlers and single day trawlers operating in this region have to be reduced by 207 and 36 respectively to retain the harvest at sustainable level.

Genetic and virulence characterisation of Vibrio parahaemolyticus isolated from Indian coast

BackgroundV. parahaemolyticus is autochthonous to the marine environment and causes seafood-borne gastroenteritis in humans. Generally, V. parahaemolyticus recovered from the environment and/or seafood is thought to be non-pathogenic and the relationship between environmental isolates and acute diarrhoeal disease is poorly understood. In this study, we explored the virulence potential of environmental V. parahaemolyticus isolated from water, plankton and assorted seafood samples collected from the Indian coast.ResultsTwenty-two V. parahaemolyticus isolates from seafood harboured virulence associated genes encoding the thermostable-direct haemolysin (TDH), TDH-related haemolysin (TRH), and Type 3 secretion systems (T3SS) and 95.5% of the toxigenic isolates had pandemic strain attributes (toxRS/new+). Nine serovars, with pandemic strain traits were newly identified and an O4:K36 tdh−trh+V. parahaemolyticus bearing pandemic marker gene was recognised for the first time. Results obtained by reverse transcription PCR showed trh, T3SS1 and T3SS2β to be functional in the seafood isolates. Moreover, the environmental strains were cytotoxic and could invade Caco-2 cells upon infection as well as induce changes to the tight junction protein, ZO-1 and the actin cytoskeleton.ConclusionOur study provides evidence that environmental isolates of V. parahaemolyticus are potentially invasive and capable of eliciting pathogenic characteristics typical of clinical strains and present a potential health risk. We also demonstrate that virulence of this pathogen is highly complex and hence draws attention for the need to investigate more reliable virulence markers in order to distinguish the environmental and clinical isolates, which will be crucial for the pathogenomics and control of this pathogen.

Future wave-climate driven longshore sediment transport along the Indian coast

Longshore sediment transport is an important nearshore process that governs coastal erosion/accretion and in turn defines the orientation of coastlines. In this study, we assess the changes in longshore transport rates along the Indian coast due to the potential changes in wave parameters under the RCP4.5 climate scenario. The projected wave climate for two time slices, ‘near-term/present’ (2011–2040) and ‘mid-term/future’ (2041–2070) were used to investigate changes in the corresponding sediment transport rates. An empirical model accounting for major wave parameters, longshore current, resulting sediment transport and shoreline evolution was used. It was found that most of the Indian coast exhibited the same drift direction in both time slices, although changes in transport magnitude were present. To give a broad-brush characterisation of the coastline, the shoreline elements were classified as erosive, accretive or stable based on the comparative longshore transport rates of neighbouring elements. Similar characterisations, carried out for both time slices, showed that about 35% of the total coastline would remain unaffected due to the changing wave climate in the future (i.e. there is little to no change); about 20% is expected to ‘worsen’ (i.e. expected to undergo higher magnitudes of erosion wrt present rate) and 45% to ‘improve’ (i.e. expected to accrete/reach stability). It was also observed that the net annual transport rates pertaining to the future period are not expected to change significantly with respect to the current scenario. This indicates that the change in longshore transport rates arising from future changes in wave climate as represented by the RCP4.5 climate change scenario will have a broadly neutral effect.

Molecular and Systematic Identification of Food Marine Shrimps Using mtCOI Marker from Southeast Coast of India

Chennai is one of the immense habitats of shrimps on the Indian coast and it offers heaps of commercial trading each year. Studies confessed that marine shrimp species have morphologically been delineated. Molecular identification is emerging as an essential vital supportive method for taxonomy-based species identification. In this study, we have provoked molecular data of taxonomically identified marine shrimp from the Chennai coast. All the sequences generated sequences showed 99–100% similarities with the referral database sequences (National Center for Biotechnology Information, GenBank). Sequence analysis of Cytochrome c Oxidase I gene conceivably directed that all the nine shrimp species parted into five distinct groups, which are genetically diverse from each other and exhibited identical phylogenetic reservation to their respective genus. Highest sequence divergence (0.332) have appeared between Heterocarpus gibbosus and Metapenaeopsis mogiensis and the lowest divergence (0.002) between Aristeus alcocki and A. virilis. Intraspecific variation ranged from 0.022 to 0.047 for A. alcocki and Solenocera crassicornis. Interspecific variation extended from 0.003 between M. stridulans and M. barbata to 0.332 between H. gibbosus to M. mogiensis. Thus, pervasive survey and more of molecular data of shrimps might actuate the ambiguous genetic variations and distances between and within the species.

Effect of seaweed coating on quality characteristics and shelf life of tomato (Lycopersicon esculentum mill)

Seaweeds are the natural marine algae which have several properties to act as natural preservatives to extend the shelf life of perishable foods without affecting their quality and causing side effects. Locally available and cheap fruits such as tomato are perishable very easily due to its high water content. Seaweed gel coating is a good choice, easily available and cheap natural preservative abundantly available in the Indian coasts. The present study was undertaken to extend the shelf life of the tomatoes using seaweed gel coating at different concentrations. Two seaweeds namely Kappaphycus alvarezii (red algae) and Sargassum tenerrimum (brown algae) was selected due to their high gelling property. Selected seaweeds were collected in dry form from Aqua Agri Processing Limited, Mana Madurai (SIPCOT) Tamil Nadu, India. The seaweed extracts were tested for phytonutrients, antibacterial and anti-fungal activity using standard procedures. The shelf life of seaweed coated tomatoes using different concentrations of the seaweed extract (gel) was tested. From the results, it is understood that the phytonutrients namely flavonoids, steroids, saponins and tannins are present in both the selected seaweeds. Antibacterial and antifungal activity of Kappaphycus alvarezii showed higher inhibition zone than S. tenerrimum against common pathogens. Quality characteristics and shelf life evaluation was based on water loss, texture, ascorbic acid content, juice content, total soluble solids (TSS), total acidity and TSS/total acidity ratio, respectively. The results pointed out that K. alvarezii was the most effective in maintaining the quality characteristics of tomato fruits and it also supports the fruit quality during storage period than S. tenerrimum. Thus, from the results of the study it is concluded that the better quality characteristics and shelf life of tomatoes can be increased by coating seaweed gel and it can be used as a bio preservative in fruit and vegetable preservation.

Comparative evaluation of linear and nonlinear weather-based models for coconut yield prediction in the west coast of India.

Coconut is a major plantation crop of coastal India. Accurate prediction of its yield is helpful for the farmers, industries and policymakers. Weather has profound impact on coconut fruit setting, and therefore, it greatly affects the yield. Annual coconut yield and monthly weather data for 2000-2015 were compiled for fourteen districts of the west coast of India. Weather indices were generated using monthly cumulative value for rainfall and monthly average value for other parameters like maximum and minimum temperature, relative humidity, wind speed and solar radiation. Different linear models like stepwise multiple linear regression (SMLR), principal component analysis together with SMLR (PCA-SMLR), least absolute shrinkage and selection operator (LASSO) and elastic net (ELNET) with nonlinear models namely artificial neural network (ANN) and PCA-ANN were employed to model the coconut yield using the monthly weather indices as inputs. The model's performance was evaluated using R2, root mean square error (RMSE) and absolute percentage error (APE). The R2 and RMSE of the models ranged between 0.45-0.99 and 18-3624 nutsha-1 respectively during calibration while during validation the APE varied between 0.12 and 58.21. The overall average ranking of the models based these performance statistics were in the order of ELNET > LASSO > ANN > SMLR > PCA-SMLR > PCA-ANN. Results indicated that the ELNET model could be used for prediction of coconut yield for the region.

Role of mangroves in wind-wave climate modeling – A review

Globally, there has been dedicated research on mangrove ecosystems, however, the modeling of wave-mangrove interaction is seldom considered in the operational wave prediction for vegetated coastlines. This review work apprises on the significant impact of mangroves on surface gravity wave characteristics. Prediction and quantification of wave attenuation characteristics by mangroves is an essential pre-requisite for coastal zone management activities along a mangrove dominated shoreline. Nevertheless, the dynamic impact of waves on mangroves is missing in the current regional wave forecasting systems. In this review article, the scientific advancements in wave-mangrove interaction studies are elucidated and focus on its significance in an operational wave modeling scheme for the Indian coast. The relevant studies on wave dissipation by mangroves and other vegetation; its nonlinear interaction in the presence of currents and extreme waves, and the need for improving its parameterization are considered distinctly. The study also highlights the importance to predict the futuristic scenarios of wave attenuation characteristics in mangrove dominated regions which are highly sensitive to effects from climate change. The authors believe that the research on dynamics of wave-mangrove interaction in India has an extensive scope, and possible future endeavors towards a realistic nearshore wave modeling along mangrove dominant coasts are presented in the concluding remarks.

Investigation of genetic diversity and stock structure of Aristeus alcocki Ramadan, 1938 (Decapoda: Aristeidae) populations in the Indian coast with microsatellite markers

Aristeus alcocki (Arabian red shrimp) forms the commercially important deep-water trawl fishery in the Indian waters. This species has not been the focus of major genetic studies in spite of our previous report on its populations suggesting significant differences. Hence, we investigated the genetic diversity and stock structure of Arabian red shrimp using nine microsatellite markers with 203 individuals collected from five locations along the Indian coast form the period of 2013–2016. The observed and expected heterozygosity ranged from 0.70–0.98 (Mean: 0.85) and 0.56–0.85 (Mean: 0.69), respectively indicating significant genetic diversity among the sampled locations. Analysis of molecular variance (AMOVA) showed >99 % of genetic variability within the individuals. Cluster analysis suggested the absence of genetic distances between the locations grouping all the individuals into a single cluster. Absence of large-scale genetic differentiation is probably governed by the mixing of waters along the coastline, habitat, currents and migratory patterns of these species have been discussed. Future studies on this species should consider it as a single stock for adopting fishery management strategies in the Indian coast.

Impact of river runoff on seasonal sea level, Kelvin waves, and East India Coastal Current in the Bay of Bengal : A numerical study using ROMS

High riverine freshwater discharge makes the salinity distribution highly heterogeneous in the Bay of Bengal (BoB). This paper investigates the impact of freshwater discharge from ten major rivers on the seasonal sea surface variability and the coastal Kelvin wave characteristics in the BoB using the Regional Ocean Modeling System (ROMS). Two numerical experiments were conducted (i) with- and (ii) without-incorporating monthly climatology of river runoff into the model under the same forcing conditions. The model was forced by Comprehensive Ocean-Atmosphere DataSet (COADS) climatology for both the experiments. This study demonstrates that incorporation of river discharge into the model simulates a realistic picture of sea surface salinity, seasonal sea level variations, Kelvin wave activities, and equatorward flowing East India Coastal Current (EICC). The amplitude of the second downwelling Kelvin wave is increased most (greater than 4 cm at the Odisha coast and approximately 2 cm near the Chennai coast) due to river discharge. Apart from that, we also found that the equatorward EICC is strengthened and more organized when river runoff is considered. The volume transport by equatorward EICC becomes almost double when river runoff is included in the model in most of the region.

The impact of northern Indian Ocean rivers on the Bay of Bengal using NEMO global ocean model

The effect of river runoff over the northern Indian Ocean (NIO) especially over the Bay of Bengal (BoB) has been studied using global Nucleus for European Modelling of the Ocean (NEMO). Two sensitivity experiments, with and without river runoff are conducted and the influence of river runoff on the Indian Ocean hydrography, stratification and circulation features are studied. It is found that due to river runoff surface salinity over the northern BoB decreases by more than 5 and the East India Coastal Current strengthens by 2 cm/s during post monsoon season. The fresh river water reaches up to 15??N in the BoB and is the main cause for low salinity there. Sea surface temperature in the northwestern BoB increases by more than 0.2??C due to the river runoff in summer monsoon while surface cooling upto 0.2??C is seen in north-west part of BoB in winter season. The seasonal mixed layer depth in the region is found to be dependent on river runoff. The effect of vertical shear and Brunt Vaisala frequency on stratification is also examined. The ocean water becomes highly stratified up to 3 035 m due to the river runoff. It is found that the energy required for mixing is high in the northern and coastal BoB.