West Coast Of India Research Articles

Determining chlorophyll-a thresholds for characterizing algal bloom conditions: An ocean colour remote sensing approach.

The Indian coast has been experiencing an increase in algal bloom events over the decades. Owing to the regional and seasonal dynamics of algal biomass (proxy: chlorophyll-a, hereafter chl-a), a multitude of thresholds of chl-a has been defined for different parts of the global seas to determine algal bloom conditions. However, no such clear definition is given for the Indian coastal waters. The current study defined chl-a thresholds to demarcate algal bloom conditions for the coastal waters of India, accounting for the variability at hotspots (in accordance with reported events: secondary data), causative species, and satellite-retrieved long-term trends. The secondary data analysis identified nine bloom hotspots along the east and west coasts of India. Among the blooms, diatoms prevailed the most, compared to dinoflagellates and cyanobacteria. Quartile analysis was employed on satellite-retrieved daily chl-a anomaly to determine specific bloom thresholds. Consequently, these quartile thresholds were utilized to classify various bloom phases, such as the 25th percentile (Likely to Bloom), 50th percentile (Bloom), 75th percentile (Intense Bloom), and 90th percentile (Extreme Bloom). As per this percentile-based classification, the 'Bloom' category corresponds to a chl-a range of 0.89-0.94mgm-3 and 0.76-2.87mgm-3, for the identified hotspots along the east and west coasts, respectively. Likewise, during the 'Intense Bloom' phase, the chl-a concentration exceeds 0.99-1.47 and 1.12-4.46mgm-3 at the hotspots along the east and west coasts, respectively. The seasonality of blooms revealed an increasing trend during the pre-southwest monsoon period on the central east coast of India. On the west coast, significant upwelling during the southwest monsoon period has been substantiated to be conducive for blooms. This study provides an avenue towards utilization of the threshold criteria in detecting different phases of bloom using satellite data in coastal waters where field observations are limited due to various factors.

Bio-concentration of hazardous metals in migrant shorebirds in a key conservation reserve and adjoining areas on the west coast of India.

Heavy metal pollution is a growing environmental concern as it causes the degradation of wetlands by affecting the organisms at different trophic levels. Shorebirds typically feed on benthic invertebrates including polychaete worms, crustaceans and molluscs. Thus, the assessment of bioconcentration of heavy metals in shorebirds provides an insight into the extent of bioaccumulation of these hazardous metals in the upper trophic levels. We studied the variation in the bioconcentration of hazardous heavy metals (chromium, lead and cadmium) in the faeces of 12 species of shorebirds (belonging to different foraging guilds including Endangered Great Knot, Vulnerable Grey Plover, Broad billed Sandpiper and Curlew Sandpiper and Near Threatened Eurasian Oystercatcher, Ruddy Turnstone and Dunlin) in relation to trends in their abundance over a period of five years (2019-2023). The study spanned over three different habitats (mudflats, mangroves and sand beaches) of Kadalundi Vallikkunnu Community Reserve (KVCR) and adjoining sand beaches, which are important wintering/ stop-over sites for the migrant shorebirds that provide abundant nutritional resources for the foraging shorebirds. We demonstrate that there has been a drastic increase in the heavy metal concentration in shorebird faeces from 2019 to 2023. Further, the findings indicate that predating and biofilm-grazing shorebirds in mangrove habitats, as well as small-bodied shorebirds in general are exposed to high levels of heavy metals. This study highlights that heavy metals in the coastal habitats are increasing and that there are potential risks from exposure to foraging shorebirds. Heavy metals have known adverse effects on shorebirds. Our study shows that reducing pollution and protecting community reserves alongside their surrounding habitats are crucial to combat biodiversity loss and maintain diversity in these areas.

Diversity and Ecology of Pollution Tolerant Phytoplankton Along Patalganga Estuary, West Coast of India

Diversity and Ecology of Pollution Tolerant Phytoplankton Along Patalganga Estuary, West Coast of India

A review on the impacts of climate variability on small pelagic fish stock variability with special emphasis on the Indian west coast

A review on the impacts of climate variability on small pelagic fish stock variability with special emphasis on the Indian west coast

Mercury Contamination Threatens Kentish Plover Populations in a key Conservation Reserve in the West Coast of India

Mercury Contamination Threatens Kentish Plover Populations in a key Conservation Reserve in the West Coast of India

Microstructures along the Indian west-coast continental shelf: layering and vertical mixing

During the month of October, the West Indian Coastal Current (WICC) is in a stage of transition from equatorward to poleward flow. The sea surface salinity near the Indian Coast is lower in the south compared to the north. Whereas the sea surface temperature is higher in the north than in the south. A salinity maximum (SM, Salinity ≥ 35.7 psu) exists in the sub-surface between depth ranges of 50–80 m. In situ vertical microstructure profiles collected along the continental shelf off the West Coast of India (WCI) for the first time, are used in this study to characterize vertical mixing under these complex thermodynamic regimes. Estimated sectional mean (median) values of the dissipation rates of turbulent kinetic energy (ɛ) and thermal variance (χ) are in the range 10−9−10−8 (10−9−10−8) W kg−1 and 10−8−10−7 (10−9−10−8) °C2 s−1 respectively. Sectional mean (median) values of the diapycnal diffusivity (Kρ) and eddy thermal diffusivity (KT) are in the range 10−6−10−5 (10−6−10−5) m2 s−1 and 10−4−10−2 (10−6−10−4) m2 s−1, respectively. The barrier layer (BL) was observed at most of the measurement locations. The layering structures in the salinity profiles observed within BL indicate the phase of transition of halocline reformation. Experiments using a one-dimensional model suggest that this layering is caused by the mixing of surface freshwater (surface freshening caused by heavy rains) with mixed-layer water. Double diffusion with weak staircase structures in temperature and salinity is observed predominantly in the interior layer of the ocean in this region. The presence of SM at most stations, with its thickness decreasing from north to south, created conditions favorable for double-diffusive mixing. Signatures of salt fingering (SF) and diffusive convection (DC) were observed in 40% and 8% of the water column, respectively. Turbulent mixing in the column below the mixed layer (ML) is weak (KT≤10−6 m2 s−1) to moderate (KT∼10−4 m2 s−1), with some highly turbulent intermittent regions (KT∼10−2 m2 s−1) conducive to DC. The data presented here show the prevalence of two mixing regimes in the vertical: (1) vertical mixing of freshwater (due to rain) with the ambient mixed layer water, and (2) small-scale double-diffusive mixing due to contrasting temperature–salinity gradients predominantly in the ocean’s interior layer (below the isothermal layer).

Seasonal nutrient loadings in four monsoonal micro/meso tidal tropical estuaries, west coast of India

Nutrient concentrations were studied seasonally along estuarine and fluvial regions of four micro/meso tidal rivers from Karnataka and Maharashtra, west coast of India. This study was performed to assess the pathway of nutrients across the salinity gradients and evaluate the impacts of weathering and human activity on nutrient concentrations. The rivers of Maharashtra had phosphate concentrations several orders of magnitude higher than the rivers of Karnataka. Nutrient vs salinity plots suggest nutrient addition for Maharashtra rivers and removal in Karnataka rivers. The nutrients in the Karnataka rivers were mostly affected by sewage outfall and anthropogenic activities (industries), while in the Maharashtra rivers, it was influenced by fertilizer application and wastewater discharge. The seasonal nutrient distribution suggests nutrient loadings occurred from the catchments during the wet (monsoon) season in all the rivers. Significant deviations from the Redfield ratio implied occurrences of algal blooms which could threaten those ecosystems.

Three-dimensional electrical imaging of the Aravali-Tural-Rajwadi geothermal system, West Coast of India

Three-dimensional electrical imaging of the Aravali-Tural-Rajwadi geothermal system, West Coast of India

Pollution Profile of the Panvel Creek, Raigad, Maharashtra, India: Analysis of the Heavy Metal Contamination

The concentration of heavy metal levels (Cd, Cu, Hg, Ni, Pb, and Zn) were assessed in water samples from Panvel creek, District Raigad, Maharashtra, West Coast of India. The heavy metals were analysed by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Results of the study reveal that, Cu, Ni, Zn, and Hg were detected in water samples of Panvel creek whereas Pb and Cd were not reported. Levels of Cu range from not detectable to 0.037 ppm whereas concentration of Ni varies from not detectable to 0.048. Zn is the only metal which is consistently detected at both the sites during all seasons whereas its values were moderately high (0.108 ppm) during the monsoon at both sites. Highest values were recorded for Hg, especially during the pre-monsoon. Highest levels of Ni and Zn were detected at both sites during monsoon season whereas Cu, Pb, Hg and Cd were not detected during monsoon at all sites. Further, Cu and Zn were detected during post-monsoon, while other metals such as Ni, Pb, Hg and Cd remain not detectable. Zn was only heavy metal detected at both sites during all sampling seasons while Pb and Cd were absent from the water samples during all the seasons at all sites. Average concentration of heavy metals reported in Panvel creek was found to be in the order of Hg>Zn>Ni>Cu>Pb>Cd. Therefore, the coastal water from the Panvel creek is polluted by heavy metals. Absence of heavy metals like Pb and Cd is attributed to the waste discharged in the creek are free from these metals and is also beneficial to the coastal biota of the creek. Consistent occurrence of Cu, Ni, Zn, and Hg in Panvel creek should not be ignored considering their impact on the ecosystem and marine biota.

Survival strategies of Bar-tailed Godwit in tropical sand beaches: Straight-line and zigzag foraging techniques

The near-threatened Bar-tailed Godwit (Limosa lapponica) makes the longest non-stop endurance flights among shorebirds. They are regular winter visitors to the Kadalundi-Vallikkunnu Community Reserve and adjoining sand beaches along the west coast of India. The research investigates their foraging strategies within sand beaches, observed over six years (2016–2022). Extensive field observations across major sand beaches documented two distinct modes of continuous stitching behaviour; a straight-line mode and a zigzag mode. Despite predation pressure and human disturbances, Bar-tailed Godwits achieved high prey capture rates, likely due to the abundance of benthic invertebrates. The study also revealed the prevalence of this behaviour and its association with rate of prey consumption, particularly focusing on the availability of Cosmonotus crabs, the dominant prey species. The zigzag pattern, was associated with higher prey capture rates, suggesting an adaptive response to prey distribution. Our findings suggest that, this unique foraging strategy allows Bar-tailed Godwits to optimize prey capture while conserving time and energy, especially in resource-scarce environments. Furthermore, the implications of these behaviours are discussed in the context of prey availability, nutrient content, and the energetic demands of long-distance migration, shedding light on to the adaptive mechanisms employed by shorebirds in challenging habitats.

English Language Learning and Acquisition Theories

Introduction: Language is a powerful tool and means of communication and to communicate with others we also use other ways such as Body manners, gestures, signals and facial expressions which is also called as a non-verbal communication. English is a tool, like basic arithmetic, or literacy, or computer skills. An ability they need to master in order to function effectively in today’s world. The L1 remains the learners primary language and the only they identify with what teachers aiming for is functional English-knowing bilingualism. Socio-political status: With the European trade patterns, most of the known European-based Creole languages were existed in the coastal regions of the Americas, Western Africa, Goa and along with the west coast of India. Indian Ocean Creole languages are based on European languages with elements from Malagasy and possibly other Asian languages. Learning Language Through Culture: Learning other language is to understand the nature of the relationship between language and culture, learners need to engage with the ways in which context affects what is communicated and how. Standard English is the variety of English that is generally acknowledged as the model for the speech and writing of educated speakers in UK. It is also associated with Received Pronunciation or accent. Intuitive acquisition: We learn anther language the same way as we learnt our first language or mother tongue. Intuitive acquisition through lots of exposure to the language in authentic communicative situations. Habit-formation: Language is a set of habits: we mimic and memorize and drill the patterns of the language until we learn to produce the correct forms automatically. Cognitive Process: Language involves the understanding of underlying rules: if we master these rules, we will be able to apply them in different contexts. That may be at school, home, with community or with others. Skill-learning: Language is a skill. We learn it in school just as we learn other skills: someone explains rules or words to us, we understand and practice them until we master them and use them fluently and skillfully.

Bill Length of Non-breeding Shorebirds Influences the Water Depth Preferences for Foraging in the West Coast of India.

Body size, bill length and shape determine foraging techniques, habitat selection and diet among shorebirds. In this study, water depth preferences of different shorebirds with different bill sizes in various habitats including mudflats, mangroves at Kadalundi-Vallikkunnu Community Reserve (KVCR) (19 shorebird species) and adjacent agroecosystems at Vazhakkad (12 species) were studied between 2017 and 2020. The bill length of the shorebirds was significantly and positively associated with the average water depth, where shorebirds were observed to forage. Shorebirds with shorter bill lengths preferred shallow waters and those with longer bills preferred deep waters for their foraging activities. Habitat type also had a significant effect on the shorebird occurrence. Eurasian Curlews in both mangroves and mudflats were observed in areas with a higher water depth compared to other species. This is due to the fact that shorebirds tend to specialise in feeding habitats or in prey items to reduce intraspecific competition and distribute themselves in space and time in accordance with the availability of their resources. The occurrence of some species in agroecosystems is attributed to the reduced food availability, habitat quality and other disturbances for shorebirds on tidal flats, which are critical for sustaining migratory phenology. The differences in bill morphology are crucial in determining diet, water depth, niche preferences and segregation. Morphological characters and hydrological rhythms determine specialisation in diet and habitat preference in shorebirds.

Slavery, Mobility, and Identity on the Western Coast of India, Sixteenth–Eighteenth Centuries

AbstractIn the wake of the establishment of the Portuguese in the region, slavery was fundamentally constitutive of early modern society on the west coast of India. While indigenous hierarchies and existing systems of slavery shaped Portuguese slavery, over time, indigenous society too was transformed by the extensive reliance on enslaved labor facilitated by European trafficking networks. Centering slavery in the study of South Asian history underscores the importance of considering the difference between elite projects of enforcing boundaries, both spatial and social, and the ways in which enslaved people negotiated these projects. Thus, instead of taking for granted the classificatory labels of race, caste, and blackness imposed upon enslaved peoples by elite institutions, a social history of slavery elucidates instead the evolution of these mechanisms for policing identity, and the centrality of the expropriation of labor in identity formation.

Controls on the distribution and fractionation of rare earth elements in recent sediments from the rivers along the west coast of India

Controls on the distribution and fractionation of rare earth elements in recent sediments from the rivers along the west coast of India

Natural light driven plastic leaching effects on carbon chemistry in the tropical coastal waters of eastern Arabian sea: An experimental study

This study examined the effects of solar light driven plastic degradation on carbon chemistry in the coastal waters of eastern Arabian Sea along the west coast of India. The research was conducted through experimental incubations exposed to natural sunlight at multiple locations between December 2023–February 2024. Photodegradation induced a significant pH decrease (up to 0.38 ± 0.02) between controls and plastic incubations ranging from 8.17 ± 0.01 to 7.54 ± 0.02 with the highest variation in the Mumbai coast ranging from 8.13 ± 0.01 to 7.75 ± 0.03. pH variations are primarily caused by the leaching of organic acids and CO2 release during solar irradiated incubation. Plastic leaching due to natural light irradiation and subsequent changes in the water chemistry is of prime significance with dissolved organic carbon (DOC) leaching of 0.002–0.03% of plastic weight into the coastal waters. Our estimations suggest 15–75 metric tonnes (MT) of DOC release per year by plastic pollution in the eastern Arabian Sea coastal waters. Further, the fluorescent dissolved organic matter (FDOM) fragmentation, a part of DOC, may act as an organic source of synthetic contaminants and would promote heterotrophic microbial action in the coastal waters. Photodegradation of plastic and the interaction of natural DOC and plastic-derived DOC resulted in longer wavelengths FDOM, which may affect the penetration of photosynthetically active radiation in the water column, thereby impacting primary production. Finally, future research work focussing on the role of plastic pollution in coastal ocean acidification and vice-versa is essential and will be increasingly intense in the upcoming decades.

A Lankan invasion? An intriguing case of the presence of a Sri Lankan endemic skink on the southwestern Indian Coast

The biota of the Indian subcontinent is a result of Gondwanan vicariance to some extent but largely through multiple faunal exchanges between neighbouring regions. However, in recent times, humans have influenced regional biotas through the human-mediated transport of many generalist species. In this study, we report populations of Lankascincus fallax, a skink species supposedly endemic to Sri Lanka, from the west coast of Kerala in India. We conducted morphological and genetic analysis to ascertain the identity of this species and to check whether the Indian population is monophyletic. We then performed a divergence dating analysis to test whether the presence of this population is a result of ancient dispersal into India or a result of more recent events. Additionally, we used species distribution modelling to test whether the Indian L. fallax is a result of natural dispersal into India during the past (mid-Pliocene to the last glacial maximum) when there were possible land bridges between India and Sri Lanka. We find that the Indian population is nested within the Sri Lankan L. fallax and that this population diverged from the Sri Lankan population very recently, during the Pleistocene. We do not find climatic suitability between the Indian west coast and Sri Lanka under current climatic conditions, or during the past suggesting no suitable dispersal corridors between India and Sri Lanka. Overall, we hypothesize that the Indian populations of L. fallax are likely a result of human-mediated transport into India and subsequent dispersal across the west coast of Kerala.

Population dynamics of the flathead grey mullet (Mugil cephalus Linnaeus 1758) in the Narmada estuary on the west coast of India

The population dynamics of flathead grey mullet, Mugil cephalus, were evaluated using length-frequency data collected from the Narmada estuary monthly between January 2018 and December 2019. The population parameters were assessed and calculated using the FiSAT-II software tool (FAO-ICLARM Stock Assessment Tools) after the estimation data were divided into 10 mm class intervals. A total of 419 specimens were collected, with an average length range of 171.14±58.15 mm and an average weight of 58.15±45.65 g, respectively. The length-weight relationships were established as W = 0.0105 L2.979. Length-frequency data revealed that length groups 140–149 (15.75 %) and 130–139 mm (13.37 %) dominated the commercial catches of M. cephalus at the Narmada estuary. Different growth parameters were estimated as L∞ = 309.75 mm, K = 0.41 yr−1 and t0 = −0.0013 years. The estimated values of mortality coefficients Z, M, and F were 1.06 yr−1, 0.52 yr−1 and 0.54 yr−1, respectively. The value of exploitation ratio (E) by using the length-converted catch curve method was established as 0.51, which was found to be a little high from the optimum value (0.50). The recruitment was found to be continuous almost throughout the year, with two peaks, once during February to May and another during August to October. The maximum sustainable yield (MSY) was estimated at 970.218 t if the suggested length at first capture (Lc = 123.44 mm TL) is maintained throughout the capture periods. The fishing pressure was found to be slightly excessive for the current stocks, which should be considered for proper management of the fishery in the Narmada estuary.

Assessing climate change vulnerability: A village level analysis of the Indian west coast

The Indian west coast is under constant threat from climate change-induced hazards. Various social, economic, and infrastructural disparities along the coast cause significant variations in climate vulnerability. Current literature assesses vulnerability either over (1) a large area with poor spatial resolution or (2) a local area with better spatial resolution. The former assessments provide more comprehensive and broad insights into large spatial trends of vulnerability, while the latter provide more accurate and specific inputs needed by the local governments for effective intervention. However, there is a lack of studies that assess vulnerability simultaneously at a high-resolution and over a large geographic area, due to inadequacies in existing methodologies and difficulty in data management and analysis. This is a key gap that we address in our paper. We assess climate vulnerability of the entire Indian west coast at the village level, and propose a novel machine-learning based methodology tailored for high-resolution assessment over large geographic areas. This helped us produce the first high-resolution (i.e. village-level) climate vulnerability map of the entire Indian west coast. We found that the state of Maharashtra has the highest number of vulnerable villages and the state of Kerala has the least number of vulnerable villages. We collate and utilize a large dataset of 112 indicators describing socioeconomic characteristics, infrastructure and availability of financial services, among other aspects, to obtain a comprehensive picture of vulnerability. We analyze geospatial trends and attribute high vulnerability to specific indicators, which will help in effective decision-making at the village level.

Distribution and bioaccumulation status of polycyclic aromatic hydrocarbons (PAHs) in Veraval coastal waters using copepods as bio-indicators.

The study investigates the pollution characteristics of 16 priority PAHs, accumulated in copepods from a major fishing harbour and its adjacent coastal waters of Veraval, west coast of India. The total PAH accumulation is in the range of 922.16-27,807.49ngg-1 dw, with the mean concentration of 5776.59ngg-1 dw. High concentrations of PAHs were present in the copepod samples from inside the harbour. Notably, there was no significant correlation between the lipid content of copepods and the accumulation of PAHs. The molecular diagnostic ratio method (MDR) indicates that the PAH sources are petrogenic in origin, while principal component analysis (PCA) points to petroleum, coal combustion and vehicular emission sources. Total cancerous PAHs (C-PAHs) in the study area dominate by 40% of the total PAHs identified; moreover, the bioaccumulation factor (BAF) is very high in the offshore area, which is also a fishing ground. The global relevance and magnitude of the present study in the Veraval, one of the prime seafood exporting hubs in India, should be dealt with utmost avidity as the accumulation status of PAHs in the zooplankton has never been explored in the Indian coastal waters. Moreover, the current study gives the foremost data on the bioaccumulation status of PAHs in copepods from the tropical waters of India.

Objective method of predicting monsoon onset over Kerala in medium and extended range time scale using Numerical Weather Prediction models

The southwest monsoon onset over Kerala (MOK) is very crucial for an Agricultural country like India hence its prediction in the extended range time scale (about 3 weeks in advance) is very useful for the Kharif season in India. As the declaration of MOK involves subjective interpretation of the forecasters, an objective method of prediction of MOK based on dynamical models could successfully avoid bogus onsets. Two objective prediction methods for MOK are developed based on the real-time extended range forecast (ERF) of rainfall measured over Kerala coast 080-120N, 740-780E and the strength and depth of the westerly wind over the Arabian Sea (050-120N, 550-750E) for the period from 2003 to 2022 are used in the first method. In addition to these 3 indices, meridional pressure gradient along the west coast of India is used in the second method with 4 indices. The MOK date is defined objectively based on these variables exceeding the thresholds in both the methods. The results indicate that the MOK forecast with four indices performed well compared to that with three indices during the whole period from 2003 to 2022 with the mean deviation days of MOK found to be 0.75 and 3.05 days respectively. Overall, the dynamically defined onset date over Kerala based on the real-time ERF indicated useful skill at least about 2–3 weeks in advance. It is also demonstrated that the district-level Multi-Model Ensemble forecast in the medium range (5 days in advance) based on 5 global models can add value to the categorical ERF of MOK for the exact forecast date of MOK.