Southwest Coast Of India Research Articles

Status of spatio-temporal variation in water quality of Ashtamudi estuary: a Ramsar wetland, southwest India

ABSTRACT The study aimed to monitor the water quality status of Ashtamudi estuary – a Ramsar wetland situated along south west coast of India. Surface water samples collected were analysed to evaluate the spatio-temporal variability in water quality parameters. Riverine sites exhibited a relative lowering of total dissolved solids due to dilution effect via runoff, substantiated by rainfall and river discharge data. Increased average salinity during non-monsoon (23.84 ± 1.02 ppt) and subsequent enriched levels of major ions at sites near to Arabian Sea was attributed to seawater intrusion. The conservative nature of major ions was established through Theoretical Dilution Line. Relatively higher biochemical oxygen demand (average = 6.54 ± 0.82 mg/L ) during monsoon was due to allochthonous organic matter input and subsequent biodegradation, substantiated by depleted Eh values (range: −105.70 to −12 mV). Concentration of dissolved inorganic phosphate (range: 0.32–2.58 µM) and nitrate (range: 1.43–182.14 µM) during non-monsoon was comparable with already published data. Decline in phosphate content during non-monsoon was due to decreased runoff, adsorption to sediments, and phytoplankton uptake. Increased silicate concentration during non-monsoon (average = 28.73 ± 0.5 µM) could be related to biodegradation of phytoplankton detritus. In general, no drastic variations in water quality were noted compared to that of the earlier investigations.

Characterization and risk assessment of microplastics accumulated in sediments and benthic molluscs in the mangrove wetlands along the south-west coast of India.

Characterization and risk assessment of microplastics accumulated in sediments and benthic molluscs in the mangrove wetlands along the south-west coast of India.

Swash zone sentinels: Unravelling microplastic pollution in selected beaches along the Southwest Coast of Peninsular India using the sand crab, Emerita emeritus.

Swash zone sentinels: Unravelling microplastic pollution in selected beaches along the Southwest Coast of Peninsular India using the sand crab, Emerita emeritus.

Assessment of heavy metal contamination and geochemical characterization of sediments in Kadinamkulam-Anchuthengu Lake a tropical coastal wetland system in south west coast of India

Assessment of heavy metal contamination and geochemical characterization of sediments in Kadinamkulam-Anchuthengu Lake a tropical coastal wetland system in south west coast of India

Validation and assessment of Potential Fishing Zone (PFZ) dynamics along the southwest coast of India through environmental proxies and trophic guild analysis

Validation and assessment of Potential Fishing Zone (PFZ) dynamics along the southwest coast of India through environmental proxies and trophic guild analysis

Marine Plastic Debris Managed Sustainably Using a Circular Economy Approach on the Southwest Coast of India

Marine Plastic Debris Managed Sustainably Using a Circular Economy Approach on the Southwest Coast of India

New Distributional Records of 31 Marine Fish Species from Rocky Reefs of Kerala: Insights from Underwater Visual Census on the Southwest Coast of India

New Distributional Records of 31 Marine Fish Species from Rocky Reefs of Kerala: Insights from Underwater Visual Census on the Southwest Coast of India

Subtidal variability of near-surface salinity in the Cochin estuary, southwest coast of India: Insights from year-long continuous observation

Subtidal variability of near-surface salinity in the Cochin estuary, southwest coast of India: Insights from year-long continuous observation

Reproductive biology of the Crimson jobfish Pristipomoides filamentosus (Valenciennes, 1830) landed along the southern coast of Kerala, India

The crimson jobfish Pristipomoides filamentosus is an important food fish belonging to the family Lutjanidae, distributed widely throughout the Indo-Pacific region, with high consumer demand and potential as a candidate species for farming. Reproductive biology of P. filamentosus was studied from 594 specimens (317 females and 277 males) collected from Vizhinjam fish landing centre on the south-west coast of India during October 2022-March 2023. The fork length (FL) of the fish ranged from 19.1 to 75.1 cm in females and 19.7 to 76.5 cm in males and the body weight (BW) ranged from 103.5 to 4276.5 g in females and 130.1 to 4346.1 g in males. The sex ratio (male: female) was 1:1.1, reflecting a marginal dominance of females in most of the months and size ranges. For females, the mean length at first maturity (Lm50) was estimated at 36.6 cm FL and for males, 35.5 cm FL. GSI showed maximum values for both females (1.73) and males (2.52) in January and February, respectively. Spawning-capable females and males were dominant during February (62.2%) and January (59.4%). Asynchronous ovarian development demonstrated multiple spawning with two distinct modes (375-404 m and 465-494 m) in the oocyte diameter distribution. Fecundity increased with fork length, body weight and ovary weight, which ranged from 151,573 to 724,856 eggs, with an average of 432,983 eggs. Based on the analyses of maturity phases and histological studies, immature, developing, spawning capable, regressing, and regenerating maturity phases for both sexes are described. Globally, information on the reproductive biology of P. filamentosus is meagre. Results of the present study could contribute to broodstock development and effective management of its fisheryin the region. Keywords: Batch spawner, Broodstock development, Fecundity, Gonadosomatic index, Histology, Length at first maturity, Sex ratio

Demographic Characteristics of Asian Sea Bass (Lates calcarifer), A Diadromous Fish from the Vembanad Estuary on the South West Coast of India

Demographic Characteristics of Asian Sea Bass (Lates calcarifer), A Diadromous Fish from the Vembanad Estuary on the South West Coast of India

Unveiling the virulence, genetic links, and enzyme profiles of bivalve-associated Vibrio parahaemolyticus from the southwest coast of India.

The study investigated the virulence, enzymatic activity, and genetic variants of Vibrio parahaemolyticus isolates from bivalves. Isolates were screened for the tdh, trh, T3SS1, T3SS2 (α and β), and T6SS1 genes associated with human infections. The tdh was found in 2.6% of isolates and trh in 3.5%. None carried both tdh and trh, and no isolates harbored T3SS2α or T3SS2β genes. All isolates contained T3SS1 genes, and 64% expressed T6SS1. Enzyme profiling revealed significant lipase, gelatinase, amylase, cellulase, lecithinase, DNase, and caseinase production, implying their ability to function as virulence factors by helping pathogens invade tissues, damage cells, and evade the host's immune defenses, thereby promoting disease development. Additionally, pulsed field gel electrophoresis and ERIC-PCR analyses examined genetic variability and linkages among the isolates. These findings demonstrate the genetic and enzymatic heterogeneity of V. parahaemolyticus in bivalves, underscoring potential risks to human health.

Livelihood Vulnerability of Small-scale Fisher Households to Climatic Hazards: A Gendered Analysis in the South West Coast of India

The experiment was conducted during January–March, 2021 at Ernakulam district of Kerala state, India to study the livelihood vulnerability of small-scale coastal fisher households to climatic hazards in a gendered perspective. The state of Kerala along the south west coast of India has been identified as one of the climate vulnerable hotspots threatened by extreme events including sea level rise. Coastal fisher communities across the world are highly vulnerable to climate change in view of the dependence on fishery-based livelihoods, depletion of marine resources, low resource possession, lack of fishing rights and other environmental hazards. Considering the low resilience of women to climate change, gender-based livelihood vulnerability assessments are essential for effective decisions on adaptation strategies within the constraints of local resources and infrastructure. The paper depicts the results of the gendered vulnerability assessment of small-scale fisher households in Ernakulum district of Kerala state. A composite livelihood vulnerability index (LVI) was developed based on the data on 400 small scale fisher households. The LVI was constructed across 8 major components consisting of socio-demographic particulars, health, water, food, natural and physical capital, financial capital, social capital and climate hazards. The results indicated that female- headed households had higher vulnerability (LVI-0.40) compared to male -headed households (LVI-0.37) and suggest the need for gender inclusive approach in the national, state and local level action plans on climate change adaptation and disaster-risk reduction programme.

Assemblage and diversity of euglenophytes in the intertidal pools along the southwest coast of India

Assemblage and diversity of euglenophytes in the intertidal pools along the southwest coast of India

Retrieval of abandoned, lost, or otherwise discarded fishing gear through different retrieval modes and analysis of biota on the retrieved gear.

Abandoned, lost, or otherwise discarded fishing gear (ALDFG) contribute significantly to marine debris, and studies regarding this subject are getting coign of vantage worldwide. This study assessed ALDFG through retrieval exercises in three prominent fishing locations, viz., Enayam, Vizhinjam, and Kochi along the southwest coast of India. The retrieval of ALDFG was carried out by scuba diving, creeper/grapple retrieval, and a bottom trawling survey by covering an area of 1.1 km2, 1.25 km2, and 32 km2, respectively, in the three study locations, Enayam, Vizhinjam, and Kochi. A total of 55.6kg ALDFG were retrieved which mainly composed of whole or parts of lobster traps, trawl cod ends, fish traps, gillnets, long lines, head ropes/foot ropes, and squid jigs contributing 46, 25, 14, 9, 4, 2, and 0.5%, respectively, to the total retrieved gear. Lobster traps dominated the retrieved ALDFG. The scuba diving mode of retrieval was most effective in Enayam and Vizhinjam due to water clarity and suitable depth range. Bottom trawling was effective in Kochi as the trials were carried out in commercial trawling grounds, where concentrations of ALDFG were reported as bycatch in trawl operations. The creeper/grapple retrieval trial along the Kochi coast failed due to the design's incompetency for deep muddy ground at the test site. Overall, 670 organisms were attached/caught in the retrieved gear of which 62% were live and 38% were dead. Perna viridis (green mussel) was the dominant species among the three study sites. The traps retrieved from Enayam and Vizhinjam did not show any signs of ghost fishing but were in a state of initiating a new ecosystem for benthic organisms. The traps of Enayam were made of HDPE webbing which contributes to marine plastic pollution, while traps of Vizhinjam were made of natural materials. Other retrieved gear types also did not show any evidence of ghost fishing. However, the polyamide (PA) monofilament gillnets disrupted the benthic mussel bed and coral reef in Enayam and Vizhinjam, respectively, by covering the habitat and hindering the growth of organisms native to the habitat. This highlights the occurrence of ALDFG and its subsequent impact on the biota in the studied area. This study, covering a smaller area, points to the need for further extensive research in this direction for the responsible management of fishing gears along the Indian coast.

Multiple proxies to investigate the submarine groundwater discharge into the Arabian Sea, Southwest coast, India: integration of biogeochemical, geophysical, and remote sensing techniques.

Submarine Groundwater Discharge (SGD) constitutes a pivotal mechanism for the transference of freshwater, nutrients, and pollutants from terrestrial to marine environments, exerting a profound influence on coastal water quality and ecosystem dynamics. In this investigation, we executed an extensive field sampling campaign along the 650km coastal expanse of southwest India, employing a 10-km sampling interval, to discern and validate the probable zones of SGD. We have utilized a transect-based methodology for the systematic collection of groundwater, porewater, and seawater samples, employing a suite of proxies to scrutinize SGD). This multifaceted approach encompassed biogeochemical, geophysical, and remote sensing techniques. The in situ physio-chemical parameters, encompassing electrical conductivity (EC), total dissolved solids (TDS), pH, dissolved oxygen (DO), temperature, and salinity, facilitated the delineation of prospective SGD sites. Adjacent continuous probable SGD sites were amalgamated into nine potential SGD zones spanning the 650km coastal stretch. Comprehensive analyses of major ions and nutrients revealed maximum observed seawater concentrations of nitrate, phosphate, and silica at 22.11µM/L, 12.5µM/L, and 11.69µM/L, respectively, underscoring the SGD signatures and the subsequent transference of nutrients from terrestrial sources to the ocean via subsurface pathways. Furthermore, geophysical investigations employing Electrical Resistivity Tomography (ERT) at the nine potential SGD zones substantiated the groundwater signatures, elucidating subsurface lithology, delineating the aquifer system, and determining the extent of the saline-freshwater interface, including discharge depth. All ERT profiles were meticulously calibrated against available lithological data. Additionally, we executed a comprehensive evaluation of Landsat-8 satellite imagery within the thermal infrared spectral domain (10.6-11.19μm) to monitor variations in sea surface temperature (SST) and sea surface anomalies across three stratified thermal ranges (21-28°C, 25-33°C, and 11-23°C) encompassing the entire study area. The visual correlation observed between lower SST values and the identified SGD probable zones further substantiates supplementary validation. Ultimately, the verification of these nine prospective SGD zones was reinforced through a meticulous comparison with groundwater level data, which ranged from 0 to 41m above mean sea level (MSL). This extensive investigation represents the inaugural comprehensive identification and confirmation of SGD zones along the southwest coast of India, spanning a 650-km stretch, resulting in a more precise demarcation of the area into nine SGD probable zones where multiple proxies are mutually corroborative.

Gobioid fishes of Ashtamudi Ramsar Lake, India: 40 years of misidentification of Oxyurichthys tentacularis, a new country record of O. omanensis, and three new records to the Southwest coast (Gobiiformes: Gobiidae).

An integrative taxonomic study on the gobioid fishes of Ashtamudi Lake (a Ramsar Site), Kerala, India revealed the occurrence of 12 species representing 10 genera, including three species of the genus Oxyurichthys. The Arrowfin goby, Oxyurichthys tentacularis, considered as the mainstay of gobioid fisheries in the Lake for over 40 years, represents a clear case of misidentification of O. ophthalmonema. Combined morpho-molecular analysis confirmed, for the first time, the occurrence of Oxyurichthys omanensis in the Indian subcontinent, and from anywhere outside its type locality in the Gulf of Oman. Three additional new records are presented: Exyrias puntang from mainland India, Paratrypauchen microcephalus from the West coast of India, and Istigobius diadema from the southwest coast of India. Intensive region-wise studies, particularly along the western coast of India, are required to better understand the diversity and distribution of estuarine and freshwater gobies.

Climatology and Trends of Various Oceanic and Atmospheric Parameters in the Arabian Sea Over the Last 45 Years

ABSTRACTThis study investigates the timescale variability of key atmospheric and oceanic variables in the Arabian Sea (AS) using 45 years (1979–2023) of data. Analyzing sea surface temperature (SST), wind components, precipitation, significant wave height, and peak wave period, notable regional and seasonal variations are identified. The northern AS experiences the highest surface warming at a rate of 0.15°C per decade. The westerlies have strengthened in the southwestern AS, while the northern AS displays a weakening trend. Along the northwest coast of India, the northerlies have intensified, but along the southwest coast of India, they have weakened. Precipitation trends have significant increases only along the southwest and northwest coasts of India. The significant wave height has increased across much of the AS, with a pronounced rise observed near the Somali coast (about 0.2 cm per year), and the peak period in the eastern AS has decreased, indicating a decline in long‐period swells from the south. Even though this basin is strongly influenced by seasonal signals, the interannual variations in wave height anomalies are particularly significant in the central AS. Seasonal analysis reveals that the wave height in the central AS has a decreasing trend in June and August, despite being the peak monsoon months. This decrease corresponds with a similar decreasing trend in SST and westerlies, as well as an increase in the peak wave period. The study further explores the influence of dominant climate modes, such as the Indian Ocean Dipole (IOD) and El Niño‐Southern Oscillation (ENSO), on the AS climate. Even though the phase agreement between IOD and ENSO is relatively good (r = 0.67) during the study period, the years 1997 and 2023 have notable differences in the meridional wind patterns, which in turn influence the significant wave height. These findings emphasise the need for adaptive strategies to address the impacts of climate variability and long‐term trends on the marine environment of the AS.

Exploration of the in-vitro antibacterial-antioxidant potentials and GC-MS metabolite profiling of seaweeds from the southwest coast of India

Abstract The present study elucidates the bioactive metabolites, antioxidants, and antibacterial potential of selected seaweeds – Kappaphycus alvarezii, Caulerpa chemnitzia, and Sargassum tenerrimum – collected from the southwest coast of India. Biomolecules were extracted using six solvents: hexane, dichloromethane, ethyl acetate, acetone, methanol, and ethanol. Among these, ethanol proved to be the most efficient extraction solvent. Notably, the ethanolic extract of S. tenerrimum exhibited high phenolic and flavonoid contents, contributing to its potent antioxidant and antibacterial properties. In contrast, the extracts of C. chemnitzia were rich in tannins, demonstrating marked antioxidant activity. Gas Chromatography-Mass Spectrometry profiling identified approximately 42 bioactive compounds with antimicrobial, antioxidant, anticancer, antidiabetic, and cardioprotective properties. Key compounds included stigmasta-5, 24(28)-dien-3-ol (3β, 24Z), cholesterol margarate, arachidonic acid, squalene, 1-hexadecanol, and δ-tocopherol, all of which hold significant nutraceutical and cosmetic value. Furthermore, antibacterial susceptibility tests against nine bacterial strains revealed that K. alvarezii was particularly effective against gram-positive bacteria, while the C. chemnitzia and S. tenerrimum extracts showed considerable efficacy against both gram-negative and gram-positive bacterial strains.

Ecological responses of benthic foraminifera to trace element pollution in the Beypore estuary, Southwest coast of India: Implications for coastal anthropogenic contamination.

Ecological responses of benthic foraminifera to trace element pollution in the Beypore estuary, Southwest coast of India: Implications for coastal anthropogenic contamination.

Implications of coastal upwelling and mud banks on the structuring of phytoplankton communities in the nearshore waters of Alappuzha, southwest coast of India.

Implications of coastal upwelling and mud banks on the structuring of phytoplankton communities in the nearshore waters of Alappuzha, southwest coast of India.