Gujarat Coast Research Articles

Feasibility of Middle East-to-India Pipeline Examined in Study

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202396, “Middle East to India Pipeline,” by Ian Nash and Matthew Rawlings, SPE, Peritus International. The paper has not been peer reviewed. The complete paper addresses the conceptualization and planning of a Middle East-to-India deepwater pipeline (MEIDP), which is planned to reach a record water depth of 3450 m and cross two continental slopes, an earthquake subduction zone [the Owen Fracture Zone (OFZ)], and outfall debris of the Indus River Fan in 2500-m-deep water. The authors examine the techniques, analysis, and technology development available at the time of writing to make such challenging routes increasingly feasible. Introduction India relies on regasification of liquefied natural gas (LNG) with terminals at major port locations. The Middle East has ready supplies of gas; however, significant challenges exist for a long-distance, ultradeepwater pipeline. South Asia Gas Enterprise (SAGE) has been developing the MEIDP as a transnational gas infrastructure project to deliver 1.1 billion scf/D from Oman to the Gujarat coast of India by a deepwater route across the Arabian Sea (Fig. 1). The pipeline will be laid as a common carrier pipeline wherein SAGE would be the gas transporter and pay a tariff for pipeline use. Gas buyers and gas sellers will negotiate long-term gas-supply contracts in a tripartite framework agreement. The current work builds on the extensive study of a potential deepwater route of the Oman-to-India pipeline performed in the early 1990s. Economic and political drivers for the project, including project economics, are detailed in the complete paper.

Geochemical and isotope tracing of groundwater salinity in the coastal Gujarat alluvial plain, India

This study attempts to learn the groundwater salinization mechanism in the large and well-populated coastal Gujarat alluvial plain under growing anthropogenic pressures. For this purpose, geochemical compositions and 87Sr/86Sr were analyzed in 53 groundwater samples collected in the three different seasons during 2016–2017. Additionally, surface water samples collected in each season from two nearby large rivers (Narmada and Tapi) and urban sewage discharge of Surat city were also analyzed. Excluding a few salinity hotspots (EC >8–18 mS/cm), the seasonal average of EC (~2.3–2.5 mS/cm) in groundwater shows little fluctuations negating evaporation as the major salinization process. Localized anthropogenic inputs as traced using NO3 also fail to explain the widespread groundwater salinity. A strong marine influence on the groundwater salinity is revealed by an average Cl/Br of ~655 ± 104 mol/mol in groundwater (except a few outliers) falling close to the seawater composition. The lateral seawater intrusion at shallow depths is generally not supported by the freshening of coastal groundwater samples and generally seaward movements of shallow groundwater as indicated by regional piezometric heads. However, few (Ca)-Mg-Cl type groundwaters collected from north of the Narmada River fall in the piezometric depressions and hint at seawater intrusion and/or upconing of deep saline aquifers. The Sr isotope budget in most of the alluvial groundwater samples is controlled by the seepage groundwater–seawater mixing. Exceptional 87Sr/86Sr values owing to Sr inputs from different age terrains are found in the northeastern groundwater and a few groundwater samples collected downslope of ancient deposits in the central alluvium. The upconing of salty waters having marine signatures partly altered by aquifer–water interactions primarily governs the regional groundwater salinity, which makes the study area vulnerable to continued salinization by excessive groundwater extraction.

New record of spot-tail sleeper ray Narke dipterygia (Bloch and Schneider, 1801) (Elasmobranchii, Torpediniformes, Narkidae) from the coast of Gujarat, India

Narke dipterygia (Bloch and Schneider, 1801), commonly known as numb ray, is a widely distributed species in the Arabian Sea and South-East Asian countries. It has been recorded from Oman, Pakistan, Sri Lanka, Malaysia, Singapore, Indonesia, Thailand, Viet Nam, China, Taiwan Province of China and Japan. In India, majority of the findings of the species is from east and west coasts of India, only two records were reported namely Bombay of Maharashtra and Kerala. The present paper confirms the presence of N. dipterygia for the first time from Gujarat coast located on the west coast of India. The diagnostic characteristics and remarks on the taxonomy and distribution of N. dipterygia have been described in this paper.

Mineralogy of Alluvial Soils Developed in Narmada River Basin in West Coast of Gujarat

Clay minerals have played a significant role for the plant nutrient management for crop production. Soils of recent and old alluvial plains deposited by Narmada river in Jhagadia block were investigated for their mineralogical makeup. The soils on recent alluvial plains (P1) (Fluventic Haplustepts) are very deep, moderately well drained, very dark grayish brown to very dark brown, silt loam to silt clay loam on level to nearly level slope with clay loam surface and slight erosion. The soils of old alluvial plain (P2) (Vertic Haplustepts) are similar to recent alluvial plain with clayey texture and moderate erosion. The pedons were sampled at one km (recent alluvial plain) and at two km (old alluvial plain) distance from Narmada river stream. The soils of recent alluvial plain are slightly alkaline (pH 7.5-8.5), slightly calcareous (<5% CaCO3) with moderate cation exchange capacity (CEC) and high in base saturation (>90%). The soils of old alluvial plain have high CEC and CaCO3 in sub-surface horizons. This paper presents a detailed study on clay minerals in surface and sub-surface sediments deposited by the Narmada river drainage basin. Clay content was ranged from 30-50% in recent alluvia and 50-60% in old alluvia. The soils of recent alluvia were high in silt fraction (40-47%) which plays an active role in potassium nutrition. The smectite content was significantly higher (weighted mean 64.9%) in old alluvial plain compared with recent plain (weighted mean 37.8%). A reverse pattern of mica distribution was observed in clay fraction of both the plains. The distribution of quartz and K/Na feldspars showed similar trends in sand fraction but wide variability was observed in the case of hydralsite, kenyaite, and boehmite content with depth. The mineralogical study indicated that the clay mineral assemblage of both sites varied in smectites and mica, which imparts heterogeneity to soil properties.

Salinity and temperature profiling for the submarine groundwater discharge simulations: Quantification through heat and solute transport model

Developed coastal regions are the hotspots for contaminated groundwater discharge, affecting sensitive marine ecosystems. The present study aims to identify submarine groundwater discharge (SGD) locations and quantify the contaminant load reaching to the western coast of India (Gujarat coast) using stable isotopes, seepage meter, heat and solute transport model. The coastal aquifers are highly enriched in trace metals due to various active natural processes and anthropogenic activities across the coast. Terrestrial and recirculated SGD was a significant contributor to flow and metal load, which ranged from 1.04 to 181.1 m3.year−1 and 0–77.41 kg.year-1, respectively. The highest estimated SGD in the Gujarat coast was relatively less than the SGD reported in the Bay of Bengal and comparable to the South Chennai coast. The order of metal flux found in the study was Zn > Fe > Cr > Pb > Ni > Cu > Mn, whereas the highest flux of Zn (77.41 kg. year−1) was reported at Fansa beach, which was 7x Fe-flux and 45 x Cr-flux, respectively. Higher micronutrients (Fe and Zn) load in the southern coast leads to increased vulnerability of eutrophication, algal blooms and biotic ligand formation in aquatic species. This enrichment of micronutrients in the coastal ecosystem was evident by the growth of seaweeds on the seabed at SGD identified locations.

Spatial variability in the community structure of microphytoplankton along the southeastern Arabian sea during an unusually warm winter monsoon season

The microphytoplankton community structure and composition were investigated along the South Eastern Arabian Sea (SEAS) during the late winter monsoon season (January 2020). A total of 186 species of phytoplankton were identified, with cyanobacteria Trichodesmium erythraeum (72%) being the most dominant, followed by diatoms (11%) and dinoflagellates (2.7%). Major blooms of T. erythraeum were observed towards the southern region of SEAS characterised by high SST (28.75 ± 0.7 °C), high surface salinity (34.6 ± 1.2 psu) and low wind speed (∼3.6 m s−1). The T. erythraeum bloom areas generally observed high nitrate and low silicate and phosphate concentrations with high chlorophyll a concentration (8.96 ± 2.92 mg m−3). In non-bloom regions, centric diatoms like Chaetoceros spp., Bacteriastrum spp. and Leptocylindrus sp. dominated. The abundance of diatoms observed a decreasing trend towards the southern extend of SEAS. The remote sensing data derived for the area observed sea surface temperatures are about 1.0 °C higher than the climatological mean of January. The higher temperatures (29 °C–32 °C) are clearly visible in the Indian coastal region from Kanyakumari to the Gujarat coast, suggesting unusual warming in the eastern coast of the Arabian Sea in January 2020. This warming which was more prominent towards the southern extend of SEAS, might have augmented the proliferation of T. erythraeum along the surface waters of SEAS.

First record of marine gastropod Prionovolva brevis (G. B. Sowerby I, 1828) from Gujarat coast, India

The present study describes a single species of marine gastropod commonly called fruit egg shell cowrie, Prionovolva brevis (G. B. Sowerby I, 1828) reported for the first time from Gujarat, India. This species was found in association with soft coral (Dendronephthya sp.) in lower intertidal zone of Sikka coast. A morphological description with key characters, illustrations and geographical distribution of present species are given.

Two-level planning approach to analyze techno-economic feasibility of hybrid offshore wind-solar pv power plants

In this paper, a two-level planning framework has been proposed to assess the techno-economic feasibility of hybrid offshore wind-solar PV power plants. In the first level, the optimal layout design of hybrid offshore wind-solar PV plants is determined to maximize the generation considering wake effect and shadow loss for wind turbines (WTs) and solar PV panels, respectively. Particle Swarm Optimization (PSO) is used to determine the optimal layout of hybrid power plants. In the second level, economic analysis has been conducted to determine the feasibility of the hybrid offshore power plants for any particular site. In this context, two scenarios have been investigated. In scenario-1, the optimal share of wind and solar generation for an offshore hybrid plant of given capacity is determined from a techno-economic point of view. On the other hand, in scenario-2, the optimal share of solar PV panels utilizing the existing electrical infrastructure of offshore wind plants has been determined. Both cases are compared on the basis of the Levelized cost of energy (LCOE), and the best alternative has been highlighted for a site in this study. Yearly data of wind speed and solar irradiation of a site near the coast of Gujarat in India has been considered to investigate the proposed approach.

Site-specific response of a 5 MW offshore wind turbine for Gujarat Coast of India

In India, the coastline of Gujarat is known to have a high potential for offshore wind energy. However, the region is highly seismically active with large magnitude earthquakes experienced in the past. The aim of the work is to investigate the site-specific response of an offshore wind turbine (OWT) for assessment of suitability of installation of OWT along the Gujarat coast. Seismic hazard analyses of 44 sites are performed using deterministic approach and response spectrum matched acceleration time histories at all these sites are obtained. Monopile for the wind turbine is designed considering a two-layered soil profile. As per specifications of National Renewable Energy Laboratory (NREL), three-dimensional finite element model of 5 MW OWT along with the soil domain is developed in the software ABAQUS considering material nonlinearity. Earthquake time histories combined with wind and wave load are being employed for the analyses. It is observed that the sites lying between Kachchh and Saurashtra regions are most vulnerable whereas sites along the western coast of Saurashtra are found to be least vulnerable. Further, seismic fragility curves for the OWT are derived for different damage states in order to evaluate the probability of damage under various seismic scenarios.

Delineation of submarine groundwater discharge and seawater intrusion zones using anomalies in the field water quality parameters, groundwater level fluctuation and sea surface temperature along the Gujarat coast of India

Nature mediated processes like seawater intrusion (SWI) and its complementary processes like submarine groundwater discharge (SGD) often cause severe water stress on the coastal water resources worldwide. The present work attempts to delineate the SWI and SGD zones along the North-Western coast of India (constituting the entire coastline of Gujarat) which is currently facing severe water crises due to the freshwater salinization and water loss through the coastal aquifer system. In the present work site-specific water characteristics and groundwater level were used as a proxy for identifying the probable zones of SWI and SGD. For the delineation purpose, we have collected 540 water samples distanced at 5–10 km (seawater, porewater and groundwater; 180 each) from the entire coastline of Gujarat. Further, a three-tier validation system has been adopted for delineating the SWI and SGD zones followed by the physical verification of the locations through the integration of (i) Groundwater fluctuation dynamic, (ii) MODIS derived sea surface temperature (SST) anomaly, and (iii) Electrical conductivity (EC) based gradient mapping. The study has identified 9 out of 14 districts being vulnerable to SWI, whereas the remaining five districts from south Gujarat and the Saurashtra coast are suspectable for SGD. The present work will act as a preliminary basis for formulating a framework for the detailed investigation of the mixing process along the coast.

Forecasting quarterly landings of total fish and major pelagic fishes and modelling the impacts of climate change on Bombay duck along India’s north-western Gujarat coast

Quarterly landings or catches of total fishes and the major pelagic fish species, were forecasted using the methods and models viz. autoregressive integrated moving average (ARIMA), non-linear autoregressive (NAR) artificial neural network (ANN), autoregressive integrated moving average with exogenous inputs (ARIMAX), non-linear autoregressive with external (exogenous) inputs (NARX) artificial neural network. The models were also developed by considering only two important variables (differ for total fish and selected fish species) obtained from the ANN model. These simplified models proved nearly as good in their predictions. Simulated sea surface temperature (SST) for the A2 climate change scenario was used as an input for the NARX model to estimate the catches of Bombay duck over a short term (2020 – 2025) and a long term (2030 – 2050) with the last two years’ (2012 – 2013) average catch of training data as a benchmark. The catches increased on average by 41 % in the short term but decreased by 17.72 % in the long term.

Discharge water temperature assessment of thermal power plant using remote sensing techniques

Thermal power plants are generally constructed near to sea coast to meet their requirement of cooling water. The warm water discharge from the thermal power plant is one of the major environmental concerns in view of the thermal pollution in the sea water. The temperature limit for the warm water discharge from the thermal power plant has to be monitored and controlled. Coastal Gujarat Power Limited (CGPL) operates (24 × 7) at an “once-through system” based sea water circulation for power generation. The used sea water is then discharged into the sea through an outlet channel. As per environmental norms, the discharge water temperature needs to be maintained below the stipulated “delta” rise (+7 °C) with respect to ambient sea surface temperature at the inlet. We demonstrate the applicability of thermal remote sensing data in understanding the seasonal and temporal variations of the temperature difference between the discharge water and the ambient sea water. We used thermal band data from Landsat-8 satellite imagery to map water surface temperature and create temperature profiles along the intake and outflow channels (till the sea), to understand the variation of temperature and estimate the “ΔT” between intake point and various observation points along the outflow. This analysis was carried out for all 11 months (except June) of the year 2018 to correlate temperature variations with seasonal changes. Tidal conditions during the time of data acquisition were also considered to account for the effect of tides on ΔT. The result shows that the average temperature rise between intake and outflow are maintained at ∼3 °C across all the months of 2018, with minor variations in the months of July and August. Further, average temperature drop from outflow to cooling channel (before diaphragm) is seen to be ∼2 °C across all the months with similar seasonal fluctuations.

Ichthyofauna species diversity of Gulf of Kachchh, Gujarat, India Case study: Jakhau and Mandvi coast

A checklist of marine fishes from the coastal areas of Jakhau and Mandvi, Gulf of Kachchh, west coast of Gujarat, India, was compiled through the fish collection from December 2013 to March 2015. On examination, a total of 20 orders, 47 families and 96 species were recorded. Of these four species were recorded from class Elasmobranchii and 92 species from class Actinopterygii. The Family Carangidae showed species dominance with 10 individuals, while the order Eupercaria is dominated with 18 numbers of species. The checklist contains 10 Not evaluated species, 6 Data deficient species, 68 Least concern species, 5 near-threatened species, 4 Vulnerable, 2 Endangered, and 1 Critically endangered species as per IUCN red list records. Of the total 96 species, the Jakhau sampling site reported 74 species; Mandvi sampling site reported 77 species, while 54 species were reported common from both the sites. Deveximentum indicium (Monkolprasit, 1973) was reported for the first time from Jakhau sampling station of Gulf of Kachchh, Gujarat. Further research is needed for better understanding and conservation of such species. The detailed study of fish habitats in the Kachchh Gulf will provide an insight into diversity and exposures to habitat destruction.

Performance of numerical weather prediction models in predicting track of recurving cyclone Vayu over Arabian Sea during June 2019

A tropical cyclone (TC) Vayu developed over the Arabian Sea during June, 2019. It followed a northward track from southeast Arabian Sea to northeast Arabian Sea close to Gujarat coast during 10–12 June 2019 as a very severe cyclonic storm. It skirted south Gujarat coast by recurving west-northwestwards during 13th–14th June and again made a northeastward recurvature on 16th June towards Gujarat coast. However, it weakened over Sea on 17th. There was large divergence among various models in predicting the track of TC Vayu leading to over warning for Gujarat state and also delay in dewarning leading to evacuation of people from coastal region. Hence, a study has thus been taken up to analyze the performance of various numerical weather prediction (NWP) models in forecasting the track of TC Vayu so as to find out the reason for above limitation of NWP models. Results suggest that there is a need to relook into the existing multi-model ensemble (MME) technique which outperforms individual models in track forecasting. There is also a need to improve the individual deterministic model guidance so as to suitably represent the interaction between mid-latitude westerlies with the TC and steering anticyclone by improving the initial and boundary conditions through augmented direct and remotely sensed observations over the Arabian Sea and their assimilation in NWP models.

Scyphozoa Pelagia noctiluca (Forsskal, 1775): blooming on the coast of Gujarat, India and its predation by Anemonia viridis (Forsskal, 1775)

The jellyfish bloom, i.e. the aggregation of Pelagia noctiluca, which occurred in January 2016 along the Shivrajpur coast facing the Arabian Sea, is reported. The jellyfish population was studied based on the Pelagia noctiluca individuals that were stranded in low tide pools and those that were washed ashore. Transects were laid to collect data on the jellyfish density. The oceanographic and physicochemical parameters at the time of bloom were studied. The probability of correlation between the time of bloom and the movement of P. noctiluca was considered. Additionally, mating and predation on the species were documented. We assume that the jellyfish bloom might have drifted to this coast due to the landlocked characteristics of the Arabian Sea and northward movements of sea currents. So far, jellyfish has been known to be the dietary preference of several vertebrate predators. Here, we report an interesting event of Anemonia viridis feeding on Pelagia noctiluca during their blooms in several intertidal pools on the coast.

Status of seawater intrusion in coastal aquifer of Gujarat, India: a review

Seawater intrusion (SWI) is a universal concern, intensified and aggravated due to over-exploitation of groundwater, sea-level rise, and climate change in the coastal province. According to the Ghyben–Herzberg principle, the stability between freshwater and saltwater is caused by the density difference between the two, until the pressure equalizes. The keystone of India’s geography, economy, biodiversity, and the environment are its extended and vast coastline, which occupies the most precious as well as potential aquifer system. This review mainly fascinated on the status, knowledge, and vulnerability of SWI within the aquifers of the coastal region of Gujarat, India. Foregoing investigations reveal that the meteoric intensification in the salinity of coastal regions of Gujarat is the chief provenance of socioeconomic development and environmental degradation. Different studies are performed to analyze and mitigate the SWI problem. In this region, groundwater over-exploitation is the foremost driver of SWI. There are miscellaneous developmental and management skills and techniques to diminish the SWI in coastal regions of the world. Numerous models are fabricated and established to analyze and epitomize the complications associated with it. Numerical models suggest some valuable techniques to manage groundwater-related problems. This study also delivers some advanced management strategies such as dilution of salinewater by artificial recharge techniques, construction of physical barriers in the subsurface to reduce the intrusion etc. feasible to the coast of Gujarat.

On the dynamics of cyclogenesis, rapid intensification and recurvature of the very severe cyclonic storm, Ockhi

A very severe cyclonic storm (VSCS), ‘Ockhi’ started its journey from southwest Bay of Bengal (BoB) over Comorin area (7.5°N–77.5°E) as a low-pressure area on 28 November, 2017. Initially it moved north-westwards across Lakshadweep Islands without hitting Tamil Nadu or Kerala coast, then moved north-eastward over the Arabian Sea and dissipated upon hitting south Gujarat coast on 06 December, 2017. Rapid intensification (RI), clockwise recurvature and a longer track were the major features of the VSCS, Ockhi. In the present study, an attempt has been made to understand the mechanism of cyclogenesis, RI and recurvature of the Ockhi using satellite and reanalysis datasets. Initially, role of easterly waves (EW) and Madden Jullian Oscillations (MJO) on the cyclogenesis of tropical cyclone Ockhi is addressed. Our analysis suggests that the EW (MJO) played a seminal (insignificant) role in preconditioning the atmosphere for the cyclogenesis of the Ockhi. Our detailed analysis using various oceanic parameters indicate that, the passage of the cyclonic storm over the regions of high thermal energy, especially warmer ocean mean temperature (OMT) at 100 m depth, was instrumental in its rapid intensification. Further, we addressed the recurving feature of the VSCS Ockhi using steering flow analysis. It is found that strong north-eastward steering winds, embedded in subtropical westerlies with deep southward extent, favoured the recurving of the Ockhi towards north-eastward by suppressing the conventional westward (north-westward) track movement.

Large‐scale offshore wind energy installation in northwest India: Assessment of wind resource using Weather Research and Forecasting and levelized cost of energy

AbstractIn India, there are plans for 5 GW of installed capacity of wind power by 2022. This study establishes that the wind resource along the west coast of Gujarat is sufficient for offshore wind farms of between 500 MW to 2 GW rated power to be operated with capacity factors of 40% to 54%. For the majority of sites, a levelized cost of energy (LCOE) in the range 68 to 86 £/MWh can be achieved with installation on floating support structures. The LCOE is up to 3.2 £/MWh greater for installation on bed‐fixed structures closer to shore. The wind resource and energy yield are predicted using Weather Research and Forecasting (WRF). Wind speed occurrence is predicted to within 1.3% for multiple sites simultaneously, and this provides wind turbine energy yield to within 3.4%. Wind speeds occurring due to sea breeze are accurately predicted and contribute 6.2% of annual energy generation at the nearshore locations and 3.8% at the deeper water offshore sites. While these events improve the viability of nearshore locations, floating installations offer lower LCOE for most locations along the Gujarat coast.

Bacteria associated with marine macroorganisms as potential source of quorum-sensing antagonists.

Samples were collected from different undisturbed areas along the coast of Gujarat like Okha, Diu, Veraval, and Somnath. A total of 68 marine isolates were obtained out of which 53 were associated with various marine macroorganisms like sponges, gastropods, and algae, whereas 15 were free living. Quorum-quenching ability of all the isolates was tested against Chromobacterium violaceum MK by co-culture technique as a way to simultaneously detect signal-degrading as well as nondegrading quorum-sensing inhibitors. Nineteen macroorganism-associated bacteria and eight free-living bacteria were found to possess quorum-sensing inhibitory activity against C. violaceum MK without affecting its growth. Isolate OA22 from grape alga and OA10 from purple sponge (Haliclona sp.) were found to possess the highest C6-HSL degradation activity and extracellular non-N-acyl-homoserine lactone degrading QSI activity, respectively. OA22 was also found to degrade 3-oxo-C12 homoserine lactone. Acid recovery of both the C6- and C12-HSL after degradation by OA22 indicated the presence of lactonase enzyme in the isolate. Cell-free supernatant of OA10 was extracted with ethyl acetate to obtain the quorum-quenching compound. Pigment inhibition in C. violaceum MK treated with OA10 extract was demonstrated in various ways and was indicative of QSI activity of the extract without degradation of the quorum-sensing signaling molecule. The isolates OA22 and OA10 were identified as Desemzia incerta and Bacillus sp., respectively, by 16S ribosomal DNA sequence analysis.

Microbial diversity from the continental shelf regions of the Eastern Arabian Sea: A metagenomic approach.

The marine microbiome is a complex and least-understood habitat, which play a significant role in global biogeochemical cycles. The present study reported the culture-independent assessment of microbial diversity from the Arabian Sea (AS) sediments (from Gujarat to Malabar; at 30 m depth) by using metagenome sequence analysis. Our results elucidated that bacterial communities in the Malabar coastal region are highly diverse than the Gujarat coast. Moreover, Statistical analysis (Spearman rank correlation) showed a significant correlation co-efficient value (r = P < 0.001) between microbial communities and physicochemical parameters (salinity and dissolved oxygen) in the water column. A total of 39 bacterial phyla were recorded from the eastern side of AS, of which six phyla Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Firmicutes, and Planctomycetes were found to be the most dominant group. The most dominant genus from Valapad region (Malabar Coast) was found to be Halomonas sp., while other regions were dominated with Psychrobacter pulmonis. The subsequent Principal Coordinate Analysis (PCoA) showed 99.53% variance, which suggests that, highly distinct microbial communities at Valapad (Malabar Coast) sampling location than other sites. Moreover, the microbial metabolic activity analysis revealed the important functions of microbial communities in the AS are hydrocarbon degradation, polymer degradation, nutrient oxidation and sulphate reduction (biodegradation process). Further extended studies are needed to be carried out for better understanding the functional diversity of microbial communities from the marine sediments.