Waters Of Arabian Sea Research Articles

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.

Identifying priority sites for whale shark ship collision management globally

The expansion of the world's merchant fleet poses a great threat to the ocean's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable species. The Endangered whale shark (Rhincodon typus) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These “constellation” sites are of significant ecological, socio-economic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world (>50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species.

Intrusion of Arabian Sea high salinity water and monsoon-associated processes modulate planktic foraminiferal abundance and carbon burial in the southwestern Bay of Bengal.

The unicellular calcareous planktic foraminifera sequester a significant portion of the carbon dioxide dissolved in the ocean, thus burying the carbon in sediments for millions of years. The global warming and associated processes are likely to affect the planktic foraminiferal abundance and diversity. Therefore, their baseline distribution has to be documented and correlated with ambient parameters to assess its fate under different climate change scenarios. Here, we report an exceptionally high abundance of planktic foraminifera and thus large carbon burial in the southwestern Bay of Bengal. The very high absolute abundance of planktic foraminifera in the Cauvery River basin is attributed to biannual productivity, warmer and saline waters. Globigerinita glutinata is the highest abundant species followed by Globigerinoides ruber and Globigerina bulloides. Globigerina bulloides is abundant on the shelf, where the upwelling is more frequent. The relative abundance of Globorotalia menardii is positively correlated with thermocline salinity and negatively correlated with thermocline temperature. Similarly, Neogloboquadrina dutertrei and Globoquadrina conglomerata are negatively correlated with mixed layer as well as thermocline temperature and mixed layer salinity. Both these species are positively correlated with thermocline salinity. Globigerina falconensis is more abundant in the southernmost transect influenced by intense winter monsoon precipitation. We report that G. ruber prefers high saline and warmer waters with the highest abundance in the southernmost transect. From the foraminiferal distribution, it is evident that the temperature and salinity of the mixed layer as well as thermocline, food availability, and monsoon-associated processes affect the planktic foraminiferal abundance and thus carbon burial in the southwestern Bay of Bengal. The changes in influx of southeastern Arabian Sea water will affect the planktic foraminiferal population and subsequent carbon burial in the southwestern Bay of Bengal.

Impact of local and remote winds on the surface waves in the coastal waters of eastern Arabian Sea

This research aims to provide analysis of wave propagation and the interaction between local and remote winds on surface waves in the coastal waters of the eastern Arabian Sea. The analysis is based on measurements from a buoy deployed at 23 m water depth along with the data from the ERA5 re-analysis. By employing lead-lag correlation analysis techniques, we identified the origin and propagation routes of waves in this region. The analysis identified the western Indian Ocean as the primary source of the waves. However, the impact of northerly systems such as Shamal and Makran winds cannot be ignored, as they play a prominent role during the pre- and post-monsoon seasons and weak southwest monsoon periods. Moreover, the study focuses on event-based analysis of tropical cyclone Tauktae based on cyclone's track, correlation analysis of its impact, and the spatial lag correlation of the associated wave system. The study builds upon existing knowledge concerning the generation and propagation of swells in the Indian Ocean. The findings of this research will contribute to a better understanding of wave dynamics in the eastern Arabian Sea and have implications for coastal engineering and marine operations in the region.

Period and length of high surface gravity waves measured in the coastal waters of eastern Arabian Sea and its variations in 10 years

Information on the period and length of waves is required for the planning and design of marine facilities and wave energy converters. In this article, the period and length of the waves measured during the peak monsoon (June–July) in the coastal waters of the eastern Arabian Sea for 10 years are examined. The most typical wave periods (T) are within 3.9 s and 5.5 s and about 25 % are above 9 s. The peak wave period (Tp) indicates that during the peak monsoon months, long-period waves dominate the eastern Arabian Sea. Significant wave period and integral wave period show a good linear relationship with energy wave period with a slope value close to 1. There are inter-annual variations of up to 15 % in the 90-percentile value of the Tp. From 2010 to 2019, the average wavelength during peak monsoon varied from 61.3 m to 67.6 m and the maximum wavelength from 216.6 m to 248.8 m. Interannual variations in the 90-percentile values for wavelength corresponding to maximum wave height is only 7 %.

Acoustic Identification of Dolphin Whistle Types in Deep Waters of Arabian Sea Using Wavelet Threshold Denoising Approach

Acoustic Identification of Dolphin Whistle Types in Deep Waters of Arabian Sea Using Wavelet Threshold Denoising Approach

A study on microzooplankton community from the coastal waters of eastern Arabian Sea: emphasis on the dominance of heterotrophic dinoflagellates.

We studied the community composition of microzooplankton (MZP) from the surface waters off Candolim, Goa. The MZP communities were examined for the year 2013, covering different seasons and four stations (Near-shore: G3 & G4, offshore: G5 & G6). A total of 30 species belonging to 24 genera were recorded, which include loricate ciliates (LC: 14 species of 13 genera), aloricate ciliates (ALC: 5 species of 3 genera), heterotrophic dinoflagellates (HDS: 11 species of 8 genera), and copepod nauplii. The MZP abundance in the coastal waters varied spatially irrespective of different seasons, with higher abundance in the offshore stations (G5 & G6, 38-127 cells L-1) and lower abundance in the near-shore stations (G3 & G4, 20-97 cells L-1). The MZP community composition showed the dominance of HDS (16-85%) in the near-shore stations during most of the seasons and inferiority during NEM (16-18%). Moreover, all the coastal waters (near and offshore) were dominated by HDS (58-85%) during spring inter-monsoon. The dominant species of HDS were Dinophysis apicata, Dinophysis caudata, Prorocentrum micans, Protoperidinium breve, Protoperidinium latistriatum, and Protoperidinium granii. The statistical analysis (Canonical correspondence analysis and Spearman's rank correlation) depicts that the MZP abundance and community composition were mainly controlled by salinity (r = 0.4-0.7). Whereas the dominance of HDS in the coastal waters could be the reason for its mixotrophic nature and diverse feeding mechanism. Thus, a strong positive correlation between the HDS and LC (r = 0.73-0.92) showed the feeding ability of HDS in their relative community.

Bio-optical complexity and radiant heating rates in the coastal waters of eastern Arabian Sea

This study aimed to elucidate the effect of bio-optical complexity on radiant heating rates in coastal waters of the eastern Arabian Sea. The in situ measurements covered a large spatial domain between 9°35′N and 15°43′N and east of 72°58′E and comprised different bio-optical measurements and in-water light field, along the pre-determined nine transects in the vicinity of riverine discharge sites influenced by Indian Summer Monsoon caused precipitation. In addition to the spatial survey, timeseries measurements were also conducted at 15°27′N and 73°42′E at a depth of 20 m. Analyzing the distinctness in surface remote sensing reflectance, data were clustered into four optical water types, representing different bio-optical states. The nearshore waters had the highest concentrations of bio-optical constituents (more bio-optically complex) while the offshore waters had low concentrations of chlorophyll-a and suspended matter (least bio-optically complex). There was a presence of higher colored dissolved organic matter in the offshore waters than in its global estimations. The estimation of radiant heating rates at the surface increased from offshore to nearshore waters. In contrast, the euphotic depth-integrated estimations of radiant heating rate were similar in nearshore and offshore waters. Because the nearshore waters had much shallower bottom and euphotic depths as compared to the offshore, similarity in radiant heating rate estimates seemed to attribute to the higher concentrations of bio-optical constituents in nearshore waters. In conditions with similar surface-reaching irradiance in nearshore and offshore waters, higher attenuation of underwater solar transmission (shallow euphotic depth) occurred when absorption and backscattering by bio-optical constituents increased. The radiant heating rate for the euphotic column in the four bio-optical water types, i.e., O1T (offshore), O2T, O3T, and O4T (nearshore) were 0.225 ± 0.118 °C hr−1, 0.214 ± 0.096 °C hr−1, 0.191 ± 0.097 °C hr−1, and 0.21 ± 0.12 °C hr−1, respectively.

Redox Changes during the Past 100 ka in the Deeper Eastern Arabian Sea: A Study Based on Trace Elements and Multivariate Statistical Analysis

The temporal distribution of trace elements in a sediment core (SK117/GC-08) indicates minor changes in oxygenation during the last 100 kilo years in the bottom waters of the deeper eastern Arabian Sea. The high values of Mn, Co, Cu, Mn/Al, Co/Al, Cu/Al, V/Cr, and V/(V + Ni) in the sediments during interglacials and interstitials collectively indicate oxic conditions during warm periods. The high values of Cr, Ni, V, Mo, Cr/Al, Ni/Al, and Ni/Co in sediments during glacials and stadials collectively indicate dysoxic to suboxic conditions during the colder last glacial maximum and during the entire marine isotope stage two. The bottom waters have never experienced anoxic conditions. Multivariate statistics showed the attribution of the trace elements in two factors: cluster 1 (Co, Cu, Mn) was enriched during oxic conditions and cluster 2 (Cr, Mo, Ni, V) was enriched during dysoxic to suboxic conditions. Oxygenation conditions are mainly driven by variations in monsoon-controlled surface water productivity and changes in the flux of circumpolar deep water. The dysoxic to suboxic bottom water conditions developed at the core location during colder climates are very well synchronised with an increased organic matter flux. The main factor that controls the accumulation of the organic-rich sediments in the eastern Arabian Sea during a glacial is the increase in the supply of organic matter from increased primary productivity in the surface waters, controlled by winter monsoon winds, and localized convective mixing. During warmer interglacials and interstadials, the core location has remained well ventilated.

A note on cetacean distribution in the Indian EEZ and contiguous seas during 2003-07

Relatively little is known about the distribution of cetaceans in Indian seas due to lack of systematic surveys. For collecting data on species distribution, 35 opportunistic surveys were conducted onboard FORV Sagar Sampada between October 2003 and February 2007 in the Indian EEZ and contiguous seas. In 5,254 hours of sighting effort, a total of 473 cetacean records were made with 5,865 individuals. The occurrence of 10 species from three cetacean families was confirmed. The Indo-Pacific bottlenose dolphin was the most frequently sighted species, whereas the spinner dolphin was dominant in terms of abundance. Long-beaked common dolphins, Indo-Pacific hump-backed dolphin and sperm whales were also recorded at frequent intervals. Cetaceans were found to have a wide geographical distribution in the Indian EEZ and contiguous seas. High abundance and species richness were recorded in the Southeastern Arabian Sea and southern Sri Lankan waters. From the information collected during the present study, the platform of opportunity has proved to be a useful means for cetacean survey.

Assessment of toxic normal saturated hydrocarbons in the Arabian seawater and Omani freshwater samples using liquid chromatography–mass spectrometry

The NHs contaminated water samples can cause several health problems such as skin irritation, acne, irregular breathing, lung irritation, cardiac arrest, itching, central nervous system (CNS), and cancer. Therefore, this current study aims to develop extraction and detection methods for normal hydrocarbons (NHs) in water samples with dichloromethane (DCM) and to detect and quantify the level of NHs in the seawater and freshwater samples by using liquid chromatography-mass spectrometry (LC–MS). Sixty-four water samples were collected from five different ports of Oman, including, Matrah, Al Mouj Marina, Salalah, Duqm, and Sohar ports, and one fresh water from Falaj Daris. The solvent–solvent extraction method was used to extract the NHs of seawater and freshwater sample with DCM. The DCM layer was passed through the silica gel column and evaporated DCM by using a rotary evaporator at low temperature and pressure. The samples were analyzed using liquid chromatography-mass spectrometry (LC/MS). The results showed that all collected seawater and freshwater samples contain NHs, but the concentration is below the detection limit. The water samples of those selected areas were not polluted by NHs toxicants. In conclusion, the low concentration of NHs could be due to the effective treatment of effluents discharged by industries, refineries, ships, and other marine vehicles. So far, it is the first report on extracting and detecting NHs in seawater and freshwater samples using LC/MS.

Measurements of 129I in waters of China, India and Arabian Sea

AMS experiments were conducted to use 129I as a tracer of the outspread of nuclear pollution from the 2011 Fukushima Nuclear Accident over India, China and the Arabian Sea. Water samples were collected repetitively between 2016 and 2020. Seawater samples from Shanghai and from Disneyland Hong Kong had low iodine concentrations of 1.4 × 107 atoms/L. However, the India big rivers and the Arabian Sea, have about one order of magnitude higher iodine concentrations on average 2.3 × 108 atoms/L. The values of the 129I tracer concentrations decrease towards south-west direction in the Arabian Sea and is reduced for rivers in the Himalayan region close to Tibet. At Muscat and Salalah, located on the Oman coast, the measured concentration in water samples were on average 2.2 × 107 atoms/L. The enhanced concentation of the 129I tracer in India is likely produced by internal pollution sources.

Isotopic fingerprinting of dual monsoon moisture sources, evapotranspiration process and microclimate manifestation over the tropical rainforest region, western part of the Western Ghats, India

The changes in precipitation pattern provide an understanding on the hydroclimatic response to global warming during the Anthropocene. The present study investigates sources of precipitation moisture for the Indian Monsoon and the local environmental mechanisms controlling its distribution over the southwest coast of India. This is achieved by the characterization of stable isotope ratios of oxygen (δ18O) and hydrogen (δ2H) in rainwater samples collected from a high humid tropical setting (Swarna-Madisal river basin) of the Western Ghats, South India and another station further south (Bakrabail, southern edge of Nethravati river basin). This study contributes to the detailed investigation on rainwater isotopic composition and microclimate characteristics which is lacking in the humid west coast region. The rainwater isotopic composition of coast was close to that of the Arabian Sea water and reflected the first condensate of vapours which were originally formed under fast evaporation at the nearby ocean. In inland location, the higher d-excess values reflect continental moisture recycling. Evapotranspiration has led to higher kinetic fractionation effect in the inland region. The isotopic storm effect during winter monsoon season suggested the rain distribution from saturated air masses formed under deep convective effect in the Bay of Bengal. The overall local meteoric water line (LMWL) in the Swarna-Madisal basin was found to be δ2H = {(7.2 × δ18O) + 7.5}, R2 = 0.98. Further south, the LMWL of Bakrabail was, δ2H = {(8.19 × δ18O) + 16.1}, R2 = 0.98 for annual observation and displayed minimal variability for inter-seasonal slopes (7.73 for summer monsoon, 8.48 for winter monsoon and 8.36 for pre-monsoon) and intercepts (15.6 for summer monsoon, 17.8 for winter monsoon and 15.5 for pre-monsoon). In regions of vegetation dominance and humid climate, the prevailing local air mass masked the rain-out effect of marine air mass as well as the amount effect which support microclimatic settings at the local precipitation sites in southwest India. The time and space variability of regional moisture circulation in controlling atmospheric water balance has been deduced in this study. Thus, the high efficacy of stable isotopes in tracing the manifestation of microclimate in the humid tropics has been demonstrated.

Influences of sea level changes and the South Asian Monsoon on southern Red Sea oceanography over the last 30 ka

AbstractThe southern Red Sea is a key region for investigating the effect of climate forces on a semi-closed basin. Detailed micropaleontological (planktic foraminifera) and isotopic (δ18Ο, δ13C) analyses along with reconstructions of sea surface temperature and salinity on a sediment core from the Farasan banks revealed the imprints of sea level changes and the South Asian Monsoon on the area. Comparison with surrounding records provided insights on the Red Sea-Gulf of Aden (GoA)-Northwestern Arabian Sea (NWArS) water exchange pattern over the last 30 ka. During glacial sea-level lowstand, flow of water from the GoA prevented hypersalinity in the southern Red Sea. Deglacial sea level rise improved water mass exchange between the NWArS, GoA and the entire Red Sea, resulting in relatively similar surface water conditions during the early Holocene when sea-level rise slowed. Thus, sea level change is the major driver of Red Sea δ18O variability. Southwest Monsoon (SWM), which was dominant during the late glacial and Early–Middle Holocene, enhanced surface productivity in the southern Red Sea. Northeast Monsoon (NEM) dominated around Heinrich stadial 1, as indicated by a nearly aplanktonic zone that was probably caused by restricted GoA inflow and low productivity.

Response of sea surface temperature, chlorophyll and particulate organic carbon to a tropical cyclonic storm over the Arabian Sea, Southwest India

The response of sea surface temperature (SST), chlorophyll (Chl) and particulate organic carbon (POC) to the tropical cyclonic storm Ockhi between 29th November and 6th December 2017 over the Arabian Sea, Southwest coast of India was studied. The unique observation is that the cyclone overturned northeastwards (clockwise), the wind speed in north-northwestwards (8–12 m s−1) which caused cold patches (< 28.5 °C) in the northwestern Arabian Sea compared to the southwest coast of India. Sea surface cooling (3–4 °C) was observed in concurrence with significant Chl response (0.5–7.5 mg m−3) along the Ockhi cyclone path. The post cyclonic low SST and high Chl from cyclone centre to farther areas suggested the extent of upwelled nutrient rich cold waters for plankton proliferation. POC levels showed a 3-fold increase, affected by significant biomass production due to subsurface phytoplankton and nutrient sources evidenced by deepening of mixed layer depth. The cyclone induced contrasting surface Chl (< 1 mg m−3) and POC (80–160 mg m−3) concentration substantiated the dominance of less labile refractory organic particulates in the offshore waters. The sub surface cooling and Chl bloom was noticed up to 50 m indicating the strong relation of vertical bio-physical structure during tropical cyclones. This study revealed that the tropical cyclones can act in such a way that it improves the positive magnitude of Chl and POC whereas reverses the SST behavior, on either side of the cyclone path within a short period in the oligotrophic waters of Arabian Sea.

Diversity and Distribution of Fiddler Crabs (Crustacea: Brachyura: Ocypodidae) around the Arabian Sea.

Nine species of fiddler crabs (Crustacea: Ocypodidae: Gelasiminae) are known from the Arabian Sea and adjacent waters (Red Sea, Gulf of Aden, Gulf of Oman and Arabian/Persian Gulf): five species of Austruca, one Cranuca, two Gelasimus and one Tubuca. COI sequence data match morphological species boundaries and shows high connectivity within each. The fauna is highly endemic, with three species of Austruca (A. albimana, A. iranica and A. sindensis) confined to this region, and four others restricted to the Indian Ocean. restricted to the Indian Ocean. Austruca albimana and A. iranica speciated locally and now have narrowly overlapping ranges in Oman. Our results confirm the westernmost distributions of Austruca annulipes and Tubuca alcocki are Pakistan and the Red Sea, respectively. A key for the nine species is also provided to help identification.

Variabilities in the community structure of phytoplankton in the upwelled and non-upwelled waters of southeastern Arabian Sea during the early summer monsoon

The community structure of microphytoplankton was assessed along the southeastern Arabian Sea during the early phase of the summer monsoon. The study records an intense coastal upwelling along the southernmost region (off Thiruvananthapuram), which decreased further north. High chlorophyll-a (10.8 mg m-3) and nutrient concentration was recorded in the coastal waters of Thiruvananthapuram. Even though off Mangalore (12° N) and off Goa (15° N) where upwelling was confined to narrow coastal zone, also showed high chlorophyll-a concentration, 3.98 mg m-3 and 6.31 mg m-3, respectively. The upwelled waters were dominated by centric diatoms (Thalassiosira sp.) and the non-upwelled waters (12° N and 15° N) were dominated by dinoflagellates. Microphytoplankton cell density was the highest along off Thiruvananthapuram (4.8×104 cells L-1), with maximum cell density along the coastal waters (1.4×104 cells L-1). Phytoplankton community of upwelled and non-upwelled waters showed significant variations with 60 % similarity between phytoplankton communities of upwelled waters.

Spatial and temporal changes in bomb radiocarbon in the northern Indian Ocean

For improved understanding of ocean circulation in the northern Indian Ocean region, long term continuous record of radiocarbon measurement is required. Limited radiocarbon records from the region demands investigations of natural archives. Coral core records along with some literature data were analysed to study the temporal changes in 14C values over the northern Indian Ocean. The major fraction of the bomb radiocarbon appears to have transferred in to the ocean, as recent records from the surface seawater Δ14C values show comparable or even higher than the atmospheric Δ14C values. The northern Andaman region showed higher Δ14C decline rate between 1978 and 2014 compared to the southern Bay of Bengal and the Lakshadweep region. The comparable southern Bay of Bengal and the Lakshadweep Δ14C values could be due to transfer of Arabian Sea waters to the southern Bay of Bengal. The southern Andaman region shows lower Δ14C values compared to the northern Andaman region, suggesting the influence of 14C depleted waters in the region.

Spatio-temporal variability of chlorophyll-a in response to coastal upwelling and mesoscale eddies in the South Eastern Arabian Sea

ABSTRACT The influence of mesoscale dynamics on variability of phytoplankton biomass in terms of chlorophyll-a (chl-a) concentration was studied in the coastal waters of the South Eastern Arabian Sea (SEAS) using long-term satellite data. Satellite-derived chl-a, sea level anomaly, sea surface temperature, and sea surface wind data for the period 1998–2016 were compiled from various sources and analysed to investigate the chl-a variability associated with coastal upwelling and mesoscale eddies. The Empirical Orthogonal Function and Morlet wavelet analyses were performed to estimate the quantitative variability and the result showed strong seasonal and interannual modulation in chl-a concentration and associated environmental variables. The Okubo–Weiss criterion was applied for the identification of mesoscale eddies. The results indicated the presence of cyclonic (cold core) eddies during the summer monsoon season (June–September). The wind-induced upwelling and the cyclonic eddies were most intense during the summer monsoon season, causing higher values of chl-a compared with other season. It is revealed that the variability of chl-a, which might be attributed to seasonal and interannual differences in the surface and sub-surface nutrients, is caused either by coastal upwelling or cyclonic eddies. In particular, the wind-induced upwelling strongly controls the spatial and temporal variability of chl-a compared with mesoscale eddies along the SEAS. The regression model we adopted points out the dominant role played by the wind and its forcing bring about variability in chl-a. The occurrence of extreme climatic events such as El Niño, La Niña and Indian Ocean Dipole (IOD) was noticed during the study period and particularly taken into account to understand the interannual fluctuations in chl-a and associated environmental variables. The relative variability in chl-a concentration was prominent during strong El Niño, La Niña, and IOD. We have attempted to determine the relationship between chl-a with coastal upwelling and mesoscale eddies, the overall importance of such physical forcings, and their influence on bio-production in the SEAS.

Exploration and utilisation of groundwater resources in extreme arid regions of the Tibetan Plateau: A case study on Ali area, China

Identifying a good site for groundwater exploitation in arid areas with scarce hydrogeological data is a challenging task. In this study, west of the Tibet Autonomous Region located at the peak of the world ridge that belongs to the extreme water-scarce poverty zone is used as the study area. This study is the first to determine the formation and controlling factors affecting the groundwater resources in Ali area via comprehensive geophysical and geochemical prospecting. The meteorological and hydrological characteristics of the study area are analysed, and the source and characteristics of water vapour in the study area are determined. Although the Indian peninsula and the Arabian Sea water vapour transmission paths exist, only small amounts of water vapour enter the area because of the distance limit and alpine barrier, which is the main reason for the drought in the study area. An overall conclusion of the hydrogeological condition and groundwater resources in Ali area is drawn on the basis of geophysical surveying, hydrogeological drilling, and water chemical analysis. The distribution of water resources in the Quaternary Aquifer, which is controlled by water vapour transport, aquifer-forming deposits, river distribution, and temperature, is not well-proportioned. The aquifer potentiality reduces from the southern to the northern direction in sequence. Thus, the great mass of midlands and the northern region belong to drought zones. Groundwater salinity, which is affected by drought, is higher than surface water salinity and obviously increases in constituent concentrations. The findings promote the understanding and utilisation of water resources in the study area.