Central West Coast Of India Research Articles

Investigating the evolution of sand bars and natural channel formation in the Mandovi estuary along the central west coast of India

Coastal formations, such as sandbars, play a vital role in shaping the environment and maintaining local and regional coastal morphology. This study deals with two noteworthy sandbars, namely Aguada and Reis Magos which are in the Mandovi estuary of the Goa region in the central west coast of India. They have attracted great attention because of their dynamics and their role in shaping the adjoining coast. This study employs a comprehensive approach, incorporating in-situ observations and remote sensing methods, to investigate the mechanisms underlying the emergence and dissipation of these sandbars and their linkage with adjoining navigational channels and coastline. During the intense wave conditions of the southwest monsoon (June to September), these sandbars undergo a temporary phase of dispersion. This phenomenon results in the accumulation of sand from both the sandbars and the neighbouring Miramar beach within the navigational channel. As a consequence, it obstructs maritime traffic and forms a unified shallow bar, obstructing maritime navigation in the area. However, following the attenuation of monsoon waves in October to November, the sandbar and beach initiate a gradual replenishment process, aimed at compensating for the sediment loss incurred during the monsoon season. This recurring trend has demonstrated persistent characteristics over an extended period. The presence of the sandbar may pose navigational challenges for large barges, cruise ships, and fishing boats but on the other hand, it serves as an effective barrier against incoming high-energy waves into the inner parts of the Mandovi estuary. Results revealed notable variations in the extent of the sandbar over the study period. The maximum recorded extent of the sandbar was 82.48ha and 32.59ha on May 04, 2021, while the minimum extent was measured at 36.68ha and 7.14ha on February 14, 2019, for Reis Magos and Aguada bar respectively. The sandbar promotes a calm environment along the shoreline and reduces erosion susceptibility by dissipating the wave energy before reaching the riverbanks. The absence of this protective sandbar would have significantly impacted the parts of the Goa region. Notably, the maximum erosion of 107m was observed at the right bank of the estuary, while the maximum accretion of 141m was recorded in the Caranzalem from 1975 to 2023. This study contributes valuable insights into the formation, dissipation, and environmental implications of sandbars within the estuary in Goa. The integration of in-situ observations and remote sensing data affords a comprehensive understanding of sandbar dynamics, highlighting the essential role that they play in coastal protection, navigation and the preservation of the local environment.

Preliminary Studies on Recovery of Placer Chromite from Central West Coast of India

Preliminary Studies on Recovery of Placer Chromite from Central West Coast of India

Seasonally varying biogeochemical regime around the coral habitats off central west coast of India

The Western Indian Continental Shelf (WICS) experiences upwelling during the Southwest Monsoon (SWM), leading to deoxygenation and acidification of subsurface waters. The region has patchy growth of corals, e.g. in the Grande Island and Angria Bank. Measurements made during the late SWM of 2022 reveal that the shelf waters around the Grande Island were subject to varying environmental conditions, viz. lower temperature (21.3–26.1°C), oxygen (0–4.9 mL L−1) and pHT (7.506–7.927). Complete anoxia was associated with sulphide build-up to a maximum of 5.9 μmol L−1 at 17 m depth. An additional episodic condition (high temperature, low oxygen and pH) also occurred associated presumably with a plankton bloom in April 2017. Hence, unlike the offshore coral site Angria Bank, waters around the Grande Island experiences extreme changes in physico-chemical conditions (e.g. Ωarg ∼1.2–1.8 during October 2022) seasonally as reported here. The biogeochemical conditions are however not as intense (Ωarg = 0.6) as observed along the eastern boundary upwelling system of the Pacific Ocean.

Fresh and recirculated submarine groundwater discharge zones along the central west coast of India

The study area receives an average of 2840.0 mm of rainfall within four months every year. A portion of the rainwater is flown to the sea as surface water, and the other part is percolated into the bottom as groundwater. In coastal aquifers, the groundwater is transported to the sea due to a hydraulic gradient, and it contains a significant quantity of dissolved materials and nutrients. SGD processes impact the ocean productivity, mangrove and coral growth, local acidification and many. To isolate the SGD on the central west coast of India, different data was referred. The GWL concerning MSL contributed significantly to demarcating the SGD zones by considering the positive (>0 m) and negative (<0 m) values of GWL concerning above MSL. Thermal images for SST of pre-monsoon and post-monsoon periods of 2020 exhibit cooler surrounded by warmer, which might be the SGD buffering zones in the off-central west coast of India. By considering the results from GWL and SST, 8 SGD beach sites were identified for the further particularized study. The water samples were collected in March 2022, and analyzed using standard procedures and instruments. Fresh and mixing (recirculated) zones have been isolated by piper, hydrochemical facies evolution, and Ca2++Mg2+/K++Na + Vs log Cl− ionic ratio plots. The aquifer water chemical elements are converting possibly due to ionic exchange processes. The decrease in salinity and conductivity observed in the pore water just below the seawater might be due to the influence of freshwater inputs, helping to isolate the fresh SGD and recirculated SGD zones in the study area. Among 8 sites, 3 were found to be fresh SGD sites and 5 were noticed to be mixing/recirculated SGD sites. Most of these Beaches are bounded by hills, which helps to lead the SGD along the central west coast of India.

Coral reef-associated brachyuran fauna (Crustacea: Decapoda: Brachyura) from Angria Bank off the west coast of India.

Underwater sampling via SCUBA and grab at the Angria Bank coral reefs off the central west coast of India in January 2014 revealed 11 species of Brachyura. Seven species, namely, Thusaenys irami (Laurie, 1906), Tanaocheles bidentata (Nobili, 1901), Portunus convexus De Haan, 1835, Xiphonectes macrophthalmus (Rathbun, 1906), Thalamita gatavakensis Nobili, 1906, Serenius ceylonicus (Laurie, 1906), and Soliella flava (Rathbun, 1894) are reported for the first time from Indian waters. Furthermore, the geographical distribution of T. irami and S. ceylonicus is extended westwards of hitherto known ranges.

Reconstruction of Holocene relative sea-level from beach ridges of the central west coast of India using GPR and OSL dating

The Holocene sea-level and associated shoreline regression of beach ridges in the central west coast of India have been reconstructed based on internal sedimentary architecture and luminescence chronology. For this purpose, various techniques namely ground penetrating radar (GPR), optically-stimulated luminescence (OSL) dating, and interferometry synthetic aperture radar (InSAR) have been used. The berm and beach-dune boundary of paleo beach ridges have been mapped from the high-resolution sub-surface images and converted into sea-level indicators using modern analogs and OSL ages. GPR reflection data shows a number of seaward dipping radar facies with a few landward dipping facies in paleo beach ridges. In the case of the swale, radar signal has been highly attenuated due to the presence of water and mud causing the appearance of multiple horizontal and parallel positive and negative couplets in the sedimentary layer. The results of the research reveal that the oldest beach ridge was formed around 7.7 kyr BP and sea-level was +2 m above mean sea-level. The average progradation rate of these ridges is 0.14 m/yr. From the grain size analysis, it has been found that the larger share of grain size falls into the classes of fine and moderate sand. The present displacement map of the region, which has been generated from the Sentinel-1 datasets, demonstrates that the average upliftment is 2.5 mm/yr whereas subsidence is 1 mm/yr. The fall of the Holocene relative sea-level with respect to the study region is the consequence of both global and regional events.

Insights from catch composition and historical records of elasmobranchs in the Malvan fishery on the central west coast of India.

Although elasmobranchs (sharks and rays) are highly threatened by fisheries, there are few studies that examine gear and fishery effects on catch composition and abundance across India, one of the top elasmobranch fishing nations globally. We assessed elasmobranch diversity, abundance, catch rates and fishery characteristics using landing surveys in Malvan on the central-western coast of India, a major multi-gear, multi-species fishing centre, over three sampling periods from February 2018 to March 2020. We sampled 3145 fishing trips and recorded 27 elasmobranch species, of which nearly half are categorised as "Threatened" by the IUCN. In addition, we documented historical records by compiling information from identification guides, research papers, articles and reports. During the study period, the catch was dominated by small-sized coastal species like the spadenose shark (Scoliodon laticaudus) and the scaly whipray (Brevitrygon walga). Trawlers accounted for 64.9% of the catch, highest by number, and captured smaller-sized individuals. Nonetheless, artisanal and gillnet fisheries had higher catch per unit effort (CPUE) for rays (5.1 ± 1.0) and sharks (10 ± 1.0), respectively, and captured significantly larger-sized individuals. Through generalised linear models, we found seasonal, gear and fishery effects on the abundance and size of commonly caught species. The presence of neonates and gravid females of multiple species also suggests nursery grounds in this region. Historically, 141 species have been recorded in this region, and a comparison with current catch suggests a shift in elasmobranch community structure and potential mesopredator release. This study emphasises the importance of gear and species-specific research for conservation planning at the local level and suggests the need for management strategies with fisher cooperation.

Feeding habits and reproductive biology of the rabbitfish, Siganus vermiculatus, along the central west coast of India

Feeding habits and reproductive biology of the rabbitfish, Siganus vermiculatus, along the central west coast of India

Multi-resource potentiality and multi-hazard susceptibility assessments of the central west coast of India applying machine learning and geospatial techniques

Multi-resource potentiality and multi-hazard susceptibility assessments of the central west coast of India applying machine learning and geospatial techniques

Preliminary observations on the coral reef communities in Angria Bank, an isolated carbonate bank in the Northern Indian Ocean

Submerged carbonate banks are of significant geological and biological importance and relatively little is known about the biodiversity of these deeper and less accessible habitats. This study provides pilot information on the biodiversity and spatial distribution of the coral reef communities in Angria Bank, a submerged carbonate platform along the central west coast of India. An exploratory survey was carried out in January 2014 to document the habitat characteristics and biodiversity of different reef communities across a gradient from the western to the eastern edge of the Angria Bank. The western zone of the bank comprises rocky and coralline substrates in contrast to the eastern zone which is sandy with calcareous deposits. The overall biodiversity includes 16 genera of corals from 10 families and 82 species of reef fish from 26 families, comparatively lower than the other major reef formations in the Indian Ocean. The study sites between the depths of 25–29 m along the eastern edge of the bank host abundant and diverse coral communities. The macroalgae was equally abundant in three of the five dive sites along the east zone reflecting the homogeneous distribution of reef communities in the Angria bank. Other invertebrates including members of the phylum Porifera, Mollusca, Annelida, Arthropoda, Echinodermata, and Cnidaria account for 28 species. Angria Bank signifies a biodiversity hotspot and these remote habitats hold the potential to serve as a refugium for the shallow reef communities for a range of environmental disturbances. Further research to understand the effect of climate-associated stress on the reef communities of Angria bank is vital to evolve a conservation strategy to sustain the biodiversity and resilience of these communities.

Sediment dynamics of tropical open coast beaches, central west coast of India: implications of spatio-temporal variability

Sediment dynamics of tropical open coast beaches, central west coast of India: implications of spatio-temporal variability

Exploring Diversity and Polymer Degrading Potential of Epiphytic Bacteria Isolated from Marine Macroalgae.

The macroalgae surface allows specific bacterial communities to colonize, resulting in complex biological interactions. In recent years, several researchers have studied the diversity and function of the epiphytic bacteria associated with algal host, but largely these interactions remain underexplored. In the present study we analysed the cultivable diversity and polymer degradation potential of epiphytic bacteria associated with five different marine macroalgae (Sargassum, Ulva, Padina, Dictyota and Pterocladia sp.) sampled from the central west coast of India. Out of the total 360 strains isolated, purified and preserved, about 238 strains were identified through 16S rRNA gene sequence analysis and processed for polymer (cellulose, pectin, xylan and starch) degrading activities. Phylogeny placed the strains within the classes Actinobacteria, Bacilli, Alpha-proteobacteria, and Gamma-proteobacteria and clustered them into 45 genera, wherein Vibrio, Bacillus, Pseudoalteromonas, Alteromonas, Staphylococcus and Kocuria spp. were the most abundant with 20 strains identified as potentially novel taxa within the genera Bacillus, Cellulosimicrobium, Gordonia, Marinomonas, Vibrio, Luteimonas and Pseudoalteromonas. In terms of polymer hydrolysis potential, 61.3% had xylanase activity, while 59.7%, 58.8%, and 52.2% had amylase, cellulase, and pectinase activity, respectively. Overall, 75.6% of the strains degraded more than one polysaccharide, 24% degraded all polymers, while nine strains (3.8%) degraded raw sugarcane bagasse. This study showed great potential for seaweed-associated bacteria in the bio-remediation of agro-waste based raw materials, which can be employed in the form of green technology.

Mangroves in the “Plasticene”: High exposure of coastal mangroves to anthropogenic litter pollution along the Central-West coast of India

Anthropogenic litter is a ubiquitous stressor in the global ocean, and poses ominous threats to oceanic biodiversity and ecosystem functioning. At the terrestrial-ocean interface, tropical mangrove forests are subject to substantial exposure to mismanaged litter from inland and marine sources. While the effects of litter in different marine ecosystems are well-documented, research on the ecological consequences of litter pollution on mangroves remain nascent stage. Here, we investigated anthropogenic litter concentration, composition, probable sources, and impact on coastal mangroves along the Central West coast of India. The mean concentration of trapped litter was measured 8.5 ± 1.9 items/m2 (ranged 1.4 ̶ 26.9 items/m2), and 10.6 ± 0.5 items/tree (ranged 0 ̶ 85 items/tree) on the mangrove floor and mangrove canopy, respectively. Plastic dominated 83.02 % of all litter deposited on the mangrove forest floor and 93.4 % of all entangled litter on mangrove canopy. Most litter comprised single-use plastic products across all surveyed locations. Mangrove floor cleanliness was assessed using several indices, such as Clean Coast Index, General Index, Hazardous Items Index, and Pollution Load Index, reiterating an inferior cleanliness status. The pollution load index indicates “Hazard level I" plastic pollution risk across the mangroves. Litter concentration differed markedly across all sites. However, a significantly higher concentration of stranded litter was detected in the densely populated urban agglomeration and rural areas with inadequate solid waste management. Probable sources of litter indicate land-based (local) and sea-originated (fishing). Supportive information on the transport and accumulation of marine litter is examined based on the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) model version 2 reanalysis of surface wind and current pattern across the Arabian Sea followed by MIKE simulated tide-induced coastal current. Mangrove pneumatophores and branches were found to be damaged by entangled plastics. Hence, determining litter quantum and their probable input source is pivotal in mitigating anthropogenic litter impact on mangrove ecosystems and fostering mangrove conservation. Overall, results envisage that stringent enforcement, implementation of an integrated solid waste management framework, and general behavioral change of the public are crucial to mitigate litter/plastic pollution.

Faunal change over 3 decades to reveal Rotundocollarette capoori n.gen., n.sp., a unique anisakid from Johnius dussumieri from the Central west coast of India at Goa.

A unique anisakid roundworm, Rotundocollarette capoori n. gen., n.sp. infesting Johnius dussumieri from the Central West coast of India at Goa has been described. The worms are typically characterized by a cephalic collarette, a muscular collarette in post-caudal zone, intestinal caecum and a ventricular appendix. 3 pores, a part of cephalic infrastructure-a dorsal oral aperture, a dorso-laterally placed genital pore, and a sub-ventral excretory pore, at the junction of the bases of the 2 ventro-lateral lips, were typically unique as revealed by SEM studies. A pair of large squarish teeth flanked each of these three pores in the cephalic region, with 3-5 denticles in the median group, at the junction of the two arms of V-shaped structure, that joined 26-29 denticles on each arm of this V-shaped formation, running parallel and crossed past dentigerous ridges on each lip. In addition, a set of 49-50 medially organized denticles occupying the dorsal arm of V-shaped formation, in the medial space, were a conspicuous configuration, besides 70min triangular denticles at the junction of sub-ventral lips. A spined mucron at the tip of tail. The key provided by Moravec and Justine (Parasite 27:58, 2020. 10.1051/parasite/2020053) to segregate Porrocaecum-like nematode genera (Porrocaecum, Pseudoterranova, Pulchrascaris, Euterranova, and Neoterranova) has been revised to include the newly proposed genus, Rotundocollarette capoori n.gen., n.sp. The significance of the emerging nematode as an environmental bioindicator has been specified.

Spatio-Temporal Dynamics of Phytoplankton in the Mandovi Estuary, on the Central West Coast of India During Post Monsoon

Spatio-Temporal Dynamics of Phytoplankton in the Mandovi Estuary, on the Central West Coast of India During Post Monsoon

Occurrence of Elysia bangtawaensis Swennen in the mangroves of Anthropogenically polluted Thane creek, the Flamingo Bird Sanctuary, Central West Coast of India

The solar powered Sacoglossanmolluscs, Elysia bangtawaensis Swennen, ranging from 35 mm to 40 mm in length, were located for the first time from two locations in the Thane Creek Flamingo Bird Sanctuary. This is a North-western extension of its reported former range which was Ratnagiri in Maharashtra.

Energy dispersive X-Ray microanalysis in conjunction with scanning electron micrography to establish nematodes as bioindicators in marine fish environment.

Energy Dispersive X-Ray Microanalysis has been used as the non-invasive technique on Indian helminthes to explore the role of nematode parasites as bioindicators in the marine ecosystem of Central West coast of India for the first time. The accumulation of sulphur and iron were analysed from a raphidascaridoid roundworm, Rostellascaris spinicaudatum (Malhotra and Anas) parasitizing marine catfish, Arius maculatus from the Central West coast of India at Goa. Quantitatively, the cuticle on oral armature comprised as much as ten times more sulphur than iron content in the roundworm under study. However, only carbon and oxygen were detected over caudal papillae, where no metals or other elements were recorded. The utility of a raphidascaridoid nematode to act as a bioindicator, that had the potential of a bioaccumulator effector, is highlighted.

Reproductive biology and feeding dynamics of the shrimp scad Alepes djedaba (Forsskal, 1775) from Ratnagiri, central west coast of India

The shrimp scad Alepes djedaba (Forsskal, 1775) belonging to family Carangidae is one of the important components of trawl bycatch landed at Ratnagiri, Maharashtra. Length-weight relationship, condition factor, morphometrics, feeding and reproductive biology of the species was investigated in the present study. Length-weight relationship indicated isometric growth in males, females and pooled individuals. All morphometric characters showed a moderate to high degree of correlation with total length. The qualitative and quantitative analysis of food revealed that A. djedaba is a carnivorous fish feeding mainly on Acetes spp., small fishes, copepods and shrimp larvae. The male:female sex ratio was found to be 1:0.85. Higher gonadosomatic index (GSI) values for females were observed during post-monsoon season. The ova diameter study indicated that A. djedaba follows a protracted spawning season with the individual spawning twice in a season. The absolute fecundity ranged from 15004 to 640800 eggs with an average of 309916 eggs. Length at sexual maturity for female fish was estimated to be 149 mm.Keywords: Arabian Sea, Feeding biology, Pelagic fish, Spawning season, Tropical fish

Effects of sedimentary heavy metals on meiobenthic community in tropical estuaries along eastern Arabian Sea.

The central west coast of India comprises the 720km long coastline of Maharashtra state and houses widespread industrial zones along the eastern Arabian Sea. Sediments from seven industrial-dominated estuaries along the central west coast were studied for metal enrichment and benthic assemblages to determine sediment quality status and ecological effects in these areas. The suit of geochemical indices highlighted the contamination of sediment in the estuaries concerning heavy metals. Positive correlations of Hg with Co, Zn, Ni, Cr, and Pb indicated the source similarity and effect of anthropogenic activity. non-Metric Multidimensional Scaling (n-MDS) based on meiofaunal abundance showed a cleared separation of clusters through the gradient of heavy metal concentrations. The Canonical Correspondence Analysis (CCA) results with the Monte Carlo test signified those heavy metals influenced the meiobenthic community. Heavy metals (Cr, Ni, Zn, Cd, Pb, and Hg) were the main drivers shaping the meiofaunal community with a significant (p < 0.05) reduction in taxa richness, diversity, and evenness. Dominant meiofaunal assemblages evidence the tolerance of foraminiferans and nematodes. However, these taxa were affected by decreased abundance at impacted sites compared to other fauna. In conclusion, results demonstrated that impairment occurred in the meiofaunal community in most estuaries (except AB and KK).

Rip current occurrences in meso tidal surf zones at a coastal stretch along the central west coast of India

Currents in the surfzone were measured and modeled along a coastal stretch on the central west coast of India. Wave and tide were the primary forcings for the numerical model, which was validated with the measurements. The rip current occurrences concerning the prevailing coastal processes are attempted, and the instances where the rip currents can prevail are identified. The wave height, wave period, wave direction, and water level in the nearshore waters were correlated with the rip current (>0.2 m/s) occurrence. The wave period around 7–8 s and the wave direction between 240° and 275° significantly contributed to the rip currents over the entire study region. Along Sinquerim and Candolim beach stretch, a high prevalence of rip currents is observed for wave heights in the range between 1.4 and 1.6 m. In contrast, in Candolim and Baga beaches, the rip current prevalence is greater for wave heights ranging between 0.4 and 0.7 m. In comparison, the tide level between 0.5 and 1 m was significant along the Sinquerim–Candolim stretch. In contrast, tide levels between 0.75 and 2 m were significant in rip current occurrence for the Calangute and Baga stretch.