Arabian Sea Coast Research Articles

Formation mechanisms and biogeochemical response of coastal salinity front in the central eastern Arabian Sea

This study investigates the formation mechanisms and impact of a coastal salinity front observed in the central eastern Arabian Sea (EAS) coast, particularly off Mangalore (∼13°N), during the peak summer monsoon in August 2018. The interplay of intense monsoon rainfall, river runoff and coastal upwelling created a dynamic frontal zone characterised by distinct physical and biogeochemical properties in the central EAS. The study revealed that observed salinity fronts are formed due to the breaking of freshwater lenses by strong upwelled waters and the subsequent offshore transport of low-salinity plumes by prevailing current and Ekman transport. The high nutrient concentrations enhanced the chlorophyll a concentration 15–20 times higher (10.12 mg/m3) in the frontal zone compared to the non-frontal station. The dominance of diatoms in the frontal zone indicates herbivorous control in the coastal food web. Accumulation of plastic debris and foam-like particles in the frontal zone poses ecological risks and threatens aquatic life.

Holocene to present-day coastal landscapes of Bar al Hikman (Oman): Neolithic waypoints on the shores of the Arabian Sea

Dramatic climatic and environmental changes over the last 12,000 years have significantly impacted Arabian coastal stratigraphy and human populations. The Bar Al Hikman peninsula (BAH), the largest low-lying area (1000 km2) along the Arabian Sea coast of Oman is a monsoon storm-dominated carbonate-evaporite system, where late Neolithic artifacts suggest human presence from at least 5.75–5.05 ka before the present (BP). Despite its archaeological significance at the crossroads of important Neolithic coastal sites in Dhofar, Masirah, and Ja'alan coast, paleoenvironmental interpretation, timing, and expression of relative sea level (RSL) changes in this coastal area remain poorly understood. Fortunately, the extensive size and arid climate of the area have preserved carbonate-dominated Mid-Late Holocene coastal geomorphologies exceptionally well, making this area an excellent geological archive to study past coastal environments, thereby understanding how environmental changes at BAH influenced Neolithic human mobility and settlement patterns. This study reconstructs the paleoenvironment of BAH over the last 12,000 years using a combination of field and remote sensing techniques, including satellite imagery, digital elevation models, bathymetric data, GIA modeling, and Sea Level Index Points to trace RSL history. The Holocene transgression began flooding the extensive continental shelf offshore BAH around 10 ka BP, progressively separating Masirah from the mainland through channel formation between 9.5 and 8.0 ka BP. It then inundated the present-day BAH peninsula around 7.7 ka BP, reaching a highstand of 2.5–3.2 m above present sea level by 6.0 ka BP (Mid-Holocene Highstand; MHHS), before gradually declining to the current level. Human presence documented at BAH (5.75–5.05 ka BP) coincides with the end of the mid-Holocene highstand, and the onset of the regression. This relative sea level history is contemporaneous to the aridification of Arabia, a period of transition from mangrove-dominated intertidal settings to coral reef and carbonate coastal barriers. The disappearance of mangrove-like gastropods around 5.4 cal ka BP and the subsequent appearance of significant coral fragments in the sediment indicates a critical change in terms of environmental settings with less nutrients and a warmer sea surface temperature). Comparing the findings at BAH to well-established nearby Neolithic sites on Masirah Island, the scarcity of prehistoric remains at BAH suggests that during the Mid-Holocene Highstand (MHHS), the small, rocky, paleo-low-lying islands at BAH may have served as waypoints and shelters between Masirah and the mainland.

Nutrient dynamics in small west-flowing tropical mountainous rivers of India

In this study, the distribution of dissolved inorganic nitrate (DIN), phosphorus (DIP), and silicate (DSi) in surface waters of 70 coastal rivers in India's Western Ghats (WG) has been determined. The nutrient concentrations in individual rivers appear to be influenced by catchment geology, land use, and climate. The entire WG region contributes 0.31 Tg of DIN, 0.03 Tg of DIP, and 5.65 Tg of DSi annually to the coastal Arabian Sea. The annual ratios of N:P, Si:N, and Si:P suggest that most of these rivers are limited by P rather than N, and there is an excess supply of Si, primarily from natural sources. P limitation is severe during monsoon periods, while N limitation is observed in the Deccan Traps region. The annual export of 0.31 Tg of DIN from WG rivers could support 2.05 Tg of carbon (new production) on the Arabian Sea coast, indicating that the riverine export of DIN can significantly remove atmospheric CO2 through biological pumps in the Arabian Sea. The study also confirms that the excess input of Si from natural processes relative to the anthropogenic supply of limited P and N further supports the idea that riverine nutrient inputs from small west-flowing tropical mountainous rivers do not contribute to coastal eutrophication along the Eastern Arabian Sea coast.

Freshwater plume‐like condition near the north‐eastern coastal Arabian Sea during early Miocene: Evidence from the stable isotope record in the growth bands of gastropods (Turritella sp.)

AbstractThe Early Miocene witnessed major tectonic, palaeoceanographic and climatological reorganizations over the Asian realm. The Himalayan and Tibetan plateau upliftment influenced monsoon intensity during this age. Contemporary high‐resolution tropical hydroclimate records are limited. Here, we present an early Miocene sub‐annual stable isotope record from the growth bands of well‐preserved Turritella sp. from the Kachchh basin, Western India. It showed δ13C and δ18O variabilities from −4.83‰ to −1.80‰ and − 7.06‰ to −2.66‰ (in VPDB) respectively. Conventional oxygen isotope thermometry showed an apparent temperature seasonality from 9.3° to 28.1°C. A comparison of the present early Miocene δ18O record with the modern δ18O records in the carbonates from coastal‐estuarine environments of the Indian Ocean confirmed a high freshwater influx into the NE Arabian Sea during the early Miocene, similar to the modern‐day freshwater plume events observed in the coastal region.

Biology of the Bombayduck Harpadon nehereus (Hamilton, 1822) from the north-eastern Arabian Sea, India

The Bombayduck Harpadon nehereus (Hamilton, 1822) is a common species and majorcontributor to the fishery in the northern Arabian Sea. The biology of H. nehereus, exploitedby set bagnets (SBN, dol netters) and trawlers from the northern Arabian Sea coast of India(Gujarat and Maharashtra) was investigated during 2014 to 2019. Fishes with a size rangeof 30-408 mm mainly contributed to the fish landing. The sex ratio (male: female) was 1:1.5.Length at maturity (Lm) for females was estimated at 207 mm TL. Mature ovaries containedova of all maturity stages indicating the species to be a continuous spawner. The absolutefecundity ranged from 23,444 to 1,34,432 eggs per fish and relative fecundity ranged from235-430 eggs g-1. The gonadosomatic index and monthly maturity stages suggested thatH. nehereus is a continuous spawner with peaks occurring from February to April. The ‘b’value in the length-weight relationship was 3.31 showing a positive allometric growth. Thediet analysis showed H. nehereus to be a highly carnivorous predator which fed mainly oncrustaceans (Index of Relative Importance, IRI = 82.7%) followed by teleosts (17.3%). Thepresent article discusses the biology of H. nehereus in the north-eastern Arabian Sea. Keywords:Biology, Bombayduck, Fisheries, Harpadon nehereus,Indian Ocean, Trophic level

Seasonal predictability of the extreme Pakistani rainfall of 2022 possible contributions from the northern coastal Arabian Sea temperature

During the summer of 2022, Pakistan and northwestern India were hit by an unprecedented spell of heavy rainfall. Despite capturing major tropical climate anomalies, almost all seasonal prediction systems failed to predict the extreme event, far surpassing the 2010 event. While trying to find possible causes of such a failure through an analysis of inter-member anomalies and numerical experiments, we have discovered that the positive sea surface temperature anomalies in the northern coastal Arabian Sea were one of the key factors behind the event. Although the ensemble mean prediction by the original system captured only 7% of the observed precipitation anomalies over Pakistan, the sensitivity experiments, in which the model sea surface temperature in the northern Arabian Sea was nudged to observation, captured about 25% of the observed anomalies. Improving our ability to predict the conditions of the northern Arabian Sea will contribute to better forecasting of extreme rainfall events such as the one experienced in Pakistan in 2022. Further analysis and possible coordinated sensitivity experiments with multi-models are necessary for a better understanding and improving the prediction.

Mitochondrial Cytochrome b based Identification of Some Commercially Important Fishes Found in the Arabian Sea Coast of Pakistan

Mitochondrial Cytochrome b based Identification of Some Commercially Important Fishes Found in the Arabian Sea Coast of Pakistan

Beyond the Goldsmith Line: Assessing the Intricacies of Border Control, Regional Interactions, and Cross-Border Risks in the Iran-Pakistan Border Region

The Goldsmith Line is a crucial 564-mile route that runs from the Koh-i-Malik Siah tri-junction to Gawadar on the Arabian Sea coast, serving as a significant connection between the Middle East and South Asia, specifically dividing Iran and Pakistan. The Baloch people living on both sides of this border contribute to the region's demographic importance. This study examines the intricacies of border management, exploring historical elements such as regional alliances, relationships with the United States, and sectarian conflicts that have influenced security in the area. The Goldsmith Line is not involved in territorial issues but has security challenges because of cross-border migration, drug smuggling, and extremism. The border has become a potential battleground due to ongoing tensions and separatist operations. Despite the 1960 Border Accord and the 2013 security management agreement, controlling the area is difficult because of insufficient infrastructure and technology. The study examines how the Joint Comprehensive Plan of Action (JCPOA) has affected Iran-Pakistan relations and proposes that a strategic partnership rather than sectarianism should be the basis for bilateral ties. Transnational criminal organizations are increasing, making border security more complex, leading to attacks and allegations between the two nations. To tackle these difficulties, we need increased collaboration, technical progress, and a wider emphasis on socioeconomic growth to reduce criminal activities and promote regional stability.

Industrially significant biomolecules from recently discovered haloalkaliphiles, inhabitants of the coastal mangrove vegetation in Bordi, India

The coastal Arabian Sea area near Bordi, Maharashtra, India is one of the natural places for mangrove vegetation. This sampling site has been explored for the first time, and to the best of our knowledge, no other researchers have conducted scientific research on the same site prior to this. Water samples from the rhizosphere of the mangrove Avicennia marina were collected and physicochemical examination revealed that the water samples were of saline-alkaline quality. The haloalkaliphiles were isolated by using different microbiological media and characterized by polyphasic approach. Further, the isolates were identified by 16 S rRNA partial gene sequencing and MEGA version 11, a public domain was used for the evolutionary studies. The production of industrially important hydrolytic enzymes amylase, lipase, and protease were optimized in submerged fermentation media using efficient isolates via the OVAT approach, and the enzymes were found to be alkali and salt stable. The carotenoid producer, Planococcus plakortidis BMS5, was deposited at N.C.M.R., Pune, India under accession number MCC5186. The synthesis of carotenoids by Planococcus plakortidis BMS5 was carefully investigated. Thin layer chromatography, UV–VIS spectroscopy, and GC-MS were used to characterise the carotenoids. The hydrolytic enzymes produced by the efficient isolates exhibited great activity and stability over a wide pH (7−12) and temperature (20–50 oC) range. Furthermore, at 10–15% salt, the hydrolytic enzymes were the most stable. The carotenoids produced by haloalkaliphiles were discovered to have antioxidant characteristics and could be exploited in the food and pharmaceutical industries. The haloalkaliphiles' hydrolytic enzymes have the potential to be used in the development of new medicinal formulations. Overall, this study illustrates the potential of employing microbes from extreme environments to produce useful bioactive chemicals with a variety of applications in diverse industries.

Agricultural Water Deficit Trends in Yemen

Globally, climate change is triggering shifts in water availability, especially across arid and desert landscapes similar to that in Yemen, where precipitation patterns are increasingly erratic. Here, we use water budget calculations, drought metrics, and trend analyses to examine climatic water deficits, with the aim of unraveling irrigation demands and overall water stress across Yemen. The results indicate that 94% of the influx is lost back to the atmosphere via evapotranspiration, 6% is converted to runoff, and only a negligible amount, generally less than 1%, is retained as storage. The results also show an unrelenting, statistically significant water deficit increase of 0.17 mm yr−1 on the Sen’s slope, at the critical Z-value of 0.005 across the country, for the past 63 years. Our findings challenge the conventional understanding of water deficits across Yemen and suggest that the country’s water resources situation is direr than was earlier documented. Further results show that while the water shortage mosaic across the country experiences interannual variations, their occurrence is significantly intensifying. As such, an immediate and radical modernization of integrated water management systems, including concerted investments in irrigation and artificial recharge wells, especially across the Arabian Sea Coast, the Red Sea Coast, and the Highlands, is strongly recommended.

Inter-seasonal variation in nitrogen uptake rates of the eutrophic Cochin estuary and adjacent coastal Arabian Sea

The study assessed the Cochin estuary and adjacent coastal Arabian Sea for their seasonal variation in nitrate (NO3−) and ammonium (NH4+) uptake rates by total and nano + picoplankton using the 15N tracer technique. The results suggested that the NO3− and NH4+ uptake rates in the Cochin estuary are higher than those in the adjacent coastal Arabian Sea. NO3− and NH4+ uptake rates in the nearshore stations in the off Cochin station were high, indicating the influence of the eutrophic estuary. NO3− and NH4+ uptake rates conducted in off Mangalore transect were significantly lower than those of the off Cochin as it does not have an exchange with eutrophic systems. The nano + picoplankton's contribution to the total DIN uptake rates in the Cochin estuary was 77–98 %, indicating the relevance of nano + pico phytoplankton in the N cycling of the region.

Deep Sea Communication Networks for the Safety and Sustainability of Fishermen in India: A Survey

Due to long coastline of India, fishing is considered as the primary source of livelihood for the people in coastal zones. With nearly one million active fishermen, India is the 2nd largest fish producer in the world. Despite having long coastline and vast fishing community, natural calamities like cyclones frequently hit the fishing operations and render damage to the lives and property. The safety and sustainability of the fishermen remain major issues due to the lack of proper communication network from boat to shore. Though mobile network connectivity is available up to 22km from the seacoast, most of the fishermen venture into deep sea to perform the fishing activities. Recently, when the cyclone Ockhi ravaged the Arabian Sea coast, many fishermen from Kerala and Tamilnadu went missing due to delayed cyclone warning and network disconnection from the shore. In such vulnerable conditions, the fishermen community is posing serious question whether they would return safely to the shore another time when they go out to sea. Hence, this study highlights the need to develop emergency communication network for the safety of fishermen along the coastline. This survey presents a brief review of some of the solutions that address the emergency communication requirements for the fishermen far from the sea shore. Further, this study also highlights the need to install floating communication devices offshore to enable seamless connectivity during disaster times.

Anthropogenic marine litter: An approach to environmental quality for India's southeastern Arabian Sea coast

Anthropogenic marine litter (AML), mainly plastic, is a global concern that is persistent and widespread. To prevent and mitigate this threat, we need to understand the magnitude and source of AML. There is limited knowledge about AML pollution on the Indian Coast. In this context, the present study examined the distribution, abundance, typology, and beach quality based on AML along 22 beaches on the southeastern coast of the Arabian Sea. A total of 4911 AML items were classified into 9 categories, weighing 16.79 kg, and retrieved from a total area of 8000 m2. The mean abundance and weight of AML in the current study were 0.45 ± 0.34 items/m2 and 1.53 ± 0.92 g/m2, respectively. Thottapally showed the most abundant AML among the studied beaches with 0.96 items/m2, followed by Azheekkal with 0.73 items/m2. Plastic, being the most common item, accounts for 77.6 % of all items and has a mean density of 0.35 items/m2 comprising hard plastic (22 %), thermocol (13 %), food wrappers (7 %), cigarette butts (7 %), plastic rope (6 %), and plastic cutlery (6 %). Hazardous anthropogenic litter (HAL) was maximum at Thottapally (17.71 %; 85 out of 480 items collected). Based on the cleanliness of beaches, they are graded “moderately clean” (63 %) by the General Index (GI), “clean” (54 %), and “moderately clean” (40 %) as calculated by the Clean Coast Index (CCI). Hazardous Anthropogenic Beach Litter Index (HABLI) classifies 72 % of beaches as “moderately safe”, while the Environmental Status Index (ESI) rates 68 % of beaches as “mediocre”. Besides, model simulations demonstrated the pathways of AML propagation, which correlate to the littoral and coastal current flow patterns over the region. Land-based activities were the crucial factors influencing AML distribution. The study highlighted the need for effective regional litter management strategies, policy instruments for the litter impact pathways, economic, regulatory, and behavioural management tools, which were also discussed.

Radiological dose and associated risk due to 210Po in commercial inter-tidal bivalves of southwest (Arabian Sea) coast of India

The activity concentration of 210Po was determined in edible tissues of commercial bivalves on the southwest coast of India. The 210Po activity ranged from 38.3 ± 6.9 Bq kg−1 to 91.2 ± 18.6 Bq kg−1. The annual committed effective dose (ACED) and lifetime carcinogenic risk (LCR) were calculated for different age groups to determine the potential health risk associated with bivalve consumption. The average ACED ranged from 81.5 to 194.1 μSv y−1, with the 10th and 95th percentiles being 68 and 261 μSv y−1, respectively. Lifelong mortality risk (LMTR) values ranged from 1.2 × 10−3 to 2.9 × 10−3, while lifetime morbidity risk (LMBR) values ranged from 1.9 × 10−6 to 4.9 × 10−6. The effective dose was found to be within the UNSCEAR limits.

Investigation of Waves Generated by Tropical Cyclone Kyarr in the Arabian Sea: An Application of ERA5 Reanalysis Wind Data

In this study, the wave conditions in the Arabian Sea induced by tropical cyclone Kyarr (2019) have been simulated by employing the 3rd generation wave model MIKE 21 SW. The model was run from 24 October to 1 November 2019, a total of 8 days. The MIKE 21 SW model was forced by reanalyzed ERA5 wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The results are compared with buoy data from the Indian National Centre for Ocean Information Services (INCOIS), which is located at 67.44° E, 18.50° N. In addition, the satellite altimeter data (CryoSat-2, SARAL and Jason-3 satellite altimeter data) was utilized for validation. Three wave parameters are considered for the validation: the significant wave height; the peak wave period; and the mean wave direction. The validation results showed that the significant wave height, the peak wave period, and the mean wave direction could be reasonably predicted by the model with reanalysis wind data as input. The maximum significant wave height reached to 10.7 m (with an associated peak wave period of 12.5 s) on 28 October 2019 at 23:00:00 in the middle of the Arabian Sea. For coastal areas, the significant wave height along the Iran and Pakistan (north Arabian Sea) coasts increased to a range of 1.4–2.8 m when tropical cyclone Kyarr moved northward. This wave height along with elevated sea level may cause severe coastal erosion and nearshore inland flooding. Impacts of cyclones on coastal zones critical facilities and infrastructure can be reduced by timely and suitable action before the event, so coastal managers should understand the effect of cyclones and their destructive consequences. The validated model developed in this study may be utilized as input data of evaluating the risk to life and infrastructure in this area.

Seasonal differences in raindrop size and causative microphysical processes in continental, orographic and oceanic regions of the Indian subcontinent

Global precipitation measurement dual-frequency precipitation radar observations during 2014–2021 are used for the first time to infer the dominant microphysical processes responsible for the seasonal variations in mass-weighted mean diameter (Dm) in different regions of the Indian subcontinent. Seasonal differences in mean Dm estimated using stratified rain rates for deep systems is pronounced in continental and Western Ghats, while marginal in maritime and Myanmar coast regions. The mean Dm values are larger in pre-monsoon (PM) than in other seasons in all the regions due to prevalence of deepest storms and evaporation. Seasonal differences in Dm observed at the near-surface are originated at raindrop formation altitude (1.5 km below the 0 °C isotherm) and are magnified during the descent of raindrops due to more evaporation in PM over the Arabian Sea, Western Ghats, and Myanmar coast. Raindrop size show contrasting features at the formation altitude and at the near surface in southwest monsoon (SWM) and northeast monsoon (NEM) over Bay of Bengal, foothills of Himalayas, Northwest India, and southeast peninsular India. The breakup of raindrops in NEM results in small Dm at the near surface in NEM than in SWM over the Bay of Bengal and southeast peninsular India. Higher occurrence of convection over Western Ghats, evaporation over foothills of Himalayas and northwest India in NEM results in large Dm values than in SWM. Dm values of shallow rain show considerable seasonal variations over the Arabian Sea and Western Ghats and marginal differences in the Bay of Bengal and Myanmar coast.

Isolation and characterization of alkaline amylase producers from the marine environment of Arabian sea coast

Alkaline amylase producers were isolated from the marine environment of Arabian Sea coast. A total of 10 isolates were obtained from the soil and water samples collected from the marine environment. Five isolates namely; BCSS, JBWS, RBWS, BCWS and ALSS showed good growth on alkaline M9 media with 10% NaCl having starch as the primary carbon source. Based on their maximal amylase activity, three microbial cultures (BCSS, JBWS, and RBWS) were selected for the study. The crude enzyme from these purified cultures was extracted and partial characterization was carried out. The partial characterization study involved the effect of metal ions and surfactants and determination of optimal pH and temperature and its stability studies. The amylase activity was optimum for all three cultures at 60 0C whereas, the optimum pH was found to be pH 7, pH 8 and pH 9 for RBWS, JBWS and BCSS. The pH and temperature stability studies showed maximum amylase activity at its optimal conditions for 5h (300 mins) in the order BCSS>RBWS>JBWS. The amylase activity was found to increase with sodium (BCSS), manganese (RBWS) and potassium (JBWS) at 1:1 dilution. The cultures were stable with the surfactants (Tween -20, SDS and Triton-X) at 1:10 dilution of 1% surfactant and enzyme. BCSS was the most stable at high temperature and pH among all the isolates with an optimal amylase activity at pH 9 and temperature of 60 0C. The isolate was identified to be Bacillus nanhaiisediminis NH3. These remarkable properties indicated its great potential in industrial applications.

Isolation and characterization of alkaline amylase producers from the marine environment of Arabian sea coast

Isolation and characterization of alkaline amylase producers from the marine environment of Arabian sea coast

Some aspects of the Upper Palaeolithic period in Sindh, Pakistan

The study of the Upper Palaeolithic of Sindh is still in its infancy. Although it has slightly improved during the last twenty years, and a few more sites have been discovered in different parts of the province, we are still far from achieving a good knowledge of the sequence of the events that took place during the final stages of the Pleistocene in this region of the Indian Subcontinent. Despite the archaeological importance of the southern part of the country, the Arabian Sea coast in particular, which represents the suggested route followed by Modern Humans to move to India and farther east, most of this territory has not yielded any tangible trace of their passage. The scope of this paper is to update the evidence available for the Upper Palaeolithic of Sindh, and to discuss it within the general framework of the Upper Palaeolithic period of the Indian Subcontinent.

Biochemical and Anti-proliferative activities of seven abundant tropical red seaweeds confirm nutraceutical potential of Grateloupia indica

Seaweeds are being used as food items in Asian countries from ancient times. Seaweeds mainly grow in intertidal zone and survive extreme environmental conditions and thus have developed metabolites, which help them survive in such conditions. Red seaweeds have proven to be rich in compounds, which are antioxidant and having many other health benefits. In this study, seven most abundantly grown red seaweeds, Gracilaria corticata (GC), Grateloupia indica (GI), Kappaphycus alvarezii (KA), Solieria robusta (SR), Amphiroa anceps (AA), Halymenia porphyriformis (HP), and Sarconema scinaioides (SS) were collected from Saurashtra coast of Arabian Sea. Harvested seaweeds were subjected to metabolite profiling, flavonoid and phenolic content analysis, different biological activities including radical scavenging, antioxidant, reducing and proliferation inhibition. Overall, GI was found to contain high contents (flavonoid and phenolic), biological activities and proliferation inhibition. Study confirms nutraceutical potential of red seaweed Grateloupia indica to be explored further for the bioactive compound or to be used as functional food.