G.V.M. Gupta

• M.Sc., Ph.D
• Director at Centre For Marine Living Resources and Ecology

The responses of Phytoplankton Size Classes (PSCs) to seasons and the distinct phases of coastal upwelling in the northern Indian Ocean is an understudied aspect. This study introduces observations from a monthly time series conducted at three cross-shore transects in the south, central, and north regions between 6-13°N along the southwest coast of...

Submarine groundwater discharge (SGD) is a significant contributor to effect phytoplankton community shift and marine ecosystem changes, yet little information is available about its influence in the Indian coastal waters. This microcosm study assessed the impact of groundwater input on carbonate chemistry changes, plankton community structuring an...

To understand the variation in dissolved organic matter (DOM) source characteristics in relation to the dynamics of physical and biological processes in marine environments, fluorescence spectroscopy was utilized as a measurement tool. Observations were carried out in the mixed layer waters of the eastern Arabian Sea (EAS), from coastal to offshore...

Eutrophication of marine ecosystems is a global problem, particularly in a changing climate and the spreading of Oxygen Minimum Zones (OMZs). The eastern Arabian Sea has both seasonal and permanent/perennial OMZs, but our understanding of the fauna there is extremely poor. So, this study investigated the composition and physiological status (alive...

The structure and characteristics of watermass along the eastern Arabian Sea (EAS) have been re-evaluated using ship-based monthly repeat measurements along the 2000m isobath during 2018. Overall, the EAS is identified by various watermasses viz. Bay of Bengal Water (BBW) and Arabian Sea High Saline Water (ASHSW) in the surface layers (0-150m) asso...

Submarine groundwater discharge is a pivotal factor in modifying the structure of phytoplankton communities in coastal waters. The objective of the study was to investigate how variations in nutrient concentrations and ratios influence the composition of phytoplankton communities along the coastal waters of Bay of Bengal. The experiment involved mi...

The upwelling phenomenon plays a vital role within marine ecosystems, transporting essential nutrients from the bottom to the surface and boosting biological productivity. However, the bacterial community structure in upwelling zones along the western coast of India (WCI) is under-studied. This research systematically examines bacterial diversity a...

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 signif...

The basin-wide phytoplankton succession and community behaviour in response to varying nutrient patterns during various upwelling phases are detailed, for the first time, in the eastern Arabian Sea (EAS, ∼6◦ to 22◦N) during the summer monsoon (SM) of 2018. Three consecutive observations were carried out during early SM (June-July), peak SM (August)...

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...

A twenty-four month long observational study conducted in an Asia's largest brackish water ecosystem, Chilika Lagoon, India, aimed to unravel dissolved organic matter (DOM) dynamics in this tropical brackish water ecosystem. The study assessed the interplay between allochthonous and autochthonous DOM sources during lean and active flow periods base...

Ciliates are highly developed and diverse eukaryotes belonging to the microzooplankton community; they exhibit a wide distributional range and are a crucial component of the microbial food web. The current study addresses the species aggregation of ciliates, which is rare and underreported, from the Indian waters. The aggregation was dominated by c...

The largest continental shelf Oxygen Minimum Zone (OMZ) in the world is formed along the Indian western shelf in the eastern Arabian Sea during the Southwest Monsoon [(SWM); June–September], which is a natural pollution event associated with the coastal upwelling. This study examines the composition, abundance, and distribution of copepods during t...

India's vast exclusive economic zone (EEZ) with its rich bounty of living and non-living resources, offers a great opportunity to expand its economy and food security , and could enable sustainable development and create resilient jobs. Marine fisheries, mariculture and marine bioprospecting are significant sectors which could act as the next big d...

This review has been undertaken to understand the effectiveness of ocean acidification on oceanic micronutrient metal cycles (iron, copper and zinc) and its potential impacts on marine biota. Ocean acidification will slow down the oxidation of Fe(II) thereby retarding Fe(III) formation and subsequent hydrolysis/precipitation leading to an increase...

Despite the omnipresence of microplastics (MPs), the studies around the western continental shelf of India i.e. Eastern Arabian Sea (EAS) are uncovered and understudied. Thus the present study was focused to understand the spatial distribution, characterization and risk assessment of MPs in sediment across seven coastal transects (10 to 50 m) all a...

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...

Repeat measurements (nine times) of nutrients at seven to ten coast-offshore transects along the eastern Arabian Sea (EAS) in 2018–19 revealed nitrogen as the major limiting nutrient controlling the primary production. The summer monsoon upwelling at varying extents along the EAS and the winter convection in the north EAS primarily controlled the d...

This study presents how flood water transforms the hydrobiology of the nearshore waters close to estuarine inlets along the southwest coast of India, which are susceptible to significant freshwater discharge during the Southwest Monsoon (SWM) and depression events during the rest of the year. In the current study, coastal hydrography off Kochi that...

Phytoplankton size classes (PSCs) are important in marine ecosystems because they organise the food chain and trophic pathways, which determine the overall biological environment. Based on three FORV Sagar Sampada cruises, the current study provides changes in PSCs in the Northeastern Arabian Sea (NEAS; north of 18 N) during different phases of the...

Issue 25 reports on the 8th International Symposium on Gas Transfer at Water Surfaces, which took place from 17-20 May 2022 in Plymouth, UK and online. The GTWS symposium normally occurs every 5 years and has brought together scientists from countries all over the world. In May 2022, the event took place in Plymouth Marine Laboratory (PML), UK and...

This study describes an assessment of an ocean-ecosystem model in simulating marine ecosystemdynamics in the Indian coastal waters. Long-term sustainedin-situobservations of temperature,salinity, chlorophyll-a and dissolved oxygen (DO) collected in the coastal waters of India, andship-based observations are used for this assessment. The model captu...

Particulate organic carbon (POC) and its variability were studied to assess the accuracy of ocean colour retrieval algorithms over the eastern Arabian Sea (EAS) as it controls the carbon sequestration, oxygen minimum zone and biogeochemical (C, N and P) cycles. The seasonality in the physical and biological processes strongly influenced the distrib...

Even though the seasonal pattern of phytoplankton biomass distribution in the seas around India is reasonably well understood, there is relatively little information on phytoplankton size classes. The current study shows how phytoplankton of different size classes respond to nutrient enrichment caused by vertical convective mixing during the Northe...

Changes in macrozoobenthic standing stock and composition along the south-eastern Arabian Sea continental shelf (30–200 m) are investigated, based on data collected from the same sites during the same season 14 years apart (winter monsoon, 1998 and 2012), using the same platform, sampling gear, methods etc. During both surveys, polychaetes dominate...

The oxygen minimum zone (OMZ) in the eastern Arabian Sea (EAS, ∼6° to 21°N), within Indian Exclusive Economic Zone (EEZ), is mapped, for the first time, for one year through ten repeated ship-based observations between December 2017 and January 2019 at seven to ten stations along the 2000 m depth contour. On an annual basis, the OMZ (<20 µM oxygen)...

Dynamic stability (Brunt-Vaisala frequency) has marked control on the formation of deep chlorophyll maximum (DCM) layers when it occurs in shallow euphotic zone. In this work, the monthly timeseries hydrographic data collected during December, 2017 to January, 2019 were used to investigate the relationship between vertical structure of dynamic stab...

The lesser known coastal upwelling in the North Eastern Arabian Sea (NEAS) during summer monsoon, its associated dynamics and forcing mechanisms is elucidated for the first time using basin scale monthly time-series in-situ and satellite data. The presence of cool upwelled waters along northwest coast of India from July to early October with an ass...

The Gulf of Mannar (GoM), located between India and Sri Lanka, has astonishing faunal richness and diversity. Two oceanographic data sets supplemented with satellite remote sensing observations are discussed here to show the unique ecological setting in the GoM sustaining a rich and diverse fauna. We tested the hypothesis that a specific stretch of...

The Indian Ocean presents two distinct climate regimes. The north Indian Ocean is dominated by the monsoons, whereas the seasonal reversal is less pronounced in the south. The prevailing wind pattern produces upwelling along different parts of the coast in both hemispheres during different times of the year. Additionally, dynamical processes and ed...

The baseline study of Microplastics (MPs) in zooplankton (copepods, chaetognaths, decapods, and fish larvae) from six different zones along India's west coast (off Kanyakumari/Cape Comorin, Kochi, Mangalore, Goa, Mumbai, and Okha) in the Eastern Arabian Sea (EAS) is presented here with their vast ecosystem impacts. This investigation revealed that...

The quantity of floating plastic debris (FPD) is continuously being increased in the oceans. To assess their size, structure, and composition along the eastern Arabian Sea (EAS), FPD samples were collected by using a surface plankton net. The microplastic size fraction (0.5–5mm) was the most prevalent accounting for >50% of the total, followed by m...

Coastal upwelling that occurs in the eastern Arabian Sea (EAS) drive the complex dynamics of the food chain. Macrofauna plays a key role in the functioning of coastal ecosystems, but few studies explored the taxonomic and functional patterns of macrofaunal communities under upwelling influence. These patterns have been investigated in this study by...

The growing number of oxygen-deficient coastal zones around the world and their impacts on marine life has always been a controversial issue as their development is largely attributed to anthropogenic activities which can be mitigated by human actions. However, contrary to this prevailing understanding, we show here for the first time, using new co...

Coastal upwelling in the south eastern Arabian Sea (SEAS) leads to oxygen depletion over the continental shelf during the summer monsoon season (June–September), with latitudinal gradients in intensity. Based on two surveys in the onset (June) and peak (August) phases of the summer monsoon, the present study evaluates the response of macrozoobenthi...

The Indian Ocean presents two distinct climate regimes. The North Indian Ocean is dominated by the monsoons, whereas the seasonal variation is less pronounced in the south. The prevailing wind pattern produces upwelling along different parts of the coast in both hemispheres during different times of the year. Additionally, dynamical processes and e...

The paper describes the community composition of phytoplankton in the eastern Arabian Sea (EAS) during winter monsoon (WM, January-February 2018), encompassing the entire eastern part of the Arabian Sea basin (~ 6-22°N and 77-67°E) with high-resolution sampling (7 transects, 56 sites), from coastal to offshore regions. The phytoplankton pigment con...

Marine soft-sediments sustain functionally important benthic assemblages that are critical for remineralization of organic matter and supply of nutrients to the water column. While these assemblages are well studied along continental margins, investigations from insular margin that surround oceanic islands are very limited. This paper examines the...

Repeat observations over the Kochi and Mangalore shelves of the southeastern Arabian Sea (SEAS) during April to December 2012 revealed substantial accumulation of methane (CH4) in the nearshore waters (48.6 ± 34.4 nM) compared to the outer shelf (2.9 ± 0.7 nM). Sediment methanogenesis and estuarine discharge appear to be the major sources of CH4 in...

The resolution of the model emerges to be an important factor in simulating the real oceanic features. In this paper, the performance of two coupled bio-physical models, having spatial resolutions 1/12° (~9 km) and 1/4° (~25 km) configured using Regional Ocean Modeling System (ROMS), have been evaluated in simulating upper ocean dynamics of the Ara...

Upwelling enhances pCO2 levels due to injection of carbon rich water to the surface despite the removal of carbon due to increase in primary production supported by enhanced nutrients. It is hypothesized that in the Bay of Bengal, upwelling may decrease pCO2 due to existence of low saline and pCO2 poor waters in the subsurface layer. In order to te...

As projected by climate change models, increase in sea surface temperature and precipitation in the future may alter nutrient cycling in the coastal regions due to potential changes in phytoplankton community structure and their ability to assimilate nitrogen (N) and carbon (C). An experiment simulating different temperature and salinity conditions...

The South Eastern Arabian Sea (SEAS) margin represents a tropical eastern boundary upwelling system, which is subjected to intense seasonal hypoxia in the continental shelf, and impingement of oxygen minimum zone (OMZ) along the continental slope. This paper provides the first comprehensive information on abundance, diversity and distribution patte...

The response of the plankton community (micro- herein after MZP and mesozooplankton) to the seasonal intrusion of Bay of Bengal (BoB) water into the Arabian Sea from November (Initial Phase-IP) to January (Peak Phase-PP) and resultant stratification was tracked in the present study. During the winter monsoon (November –February) as part of seasonal...

Bioavailable dissolved organic carbon (B-DOC), nitrogen (B-DON) and their degradation rate constants were measured for the Chilika Lagoon, India. Long-term laboratory incubation experiments (90 days) were conducted at a constant temperature (25 °C) to quantify the bioavailable dissolved organic matter (DOM) and the possible degradation rate coeffic...

Carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the Cochin estuary, a tropical eutrophic estuary along the southwest coast of India, and the adjacent coastal Arabian Sea was measured to understand spatiotemporal variability in sources and processes controlling inorganic carbon (C) dynamics in this estuarine-coastal system. δ1...

Winter cooling and persistent mixing for more than a quarter of year (November to early March) along the North Eastern Arabian Sea (NEAS) results in nutrient enrichment of the euphotic column thereby triggering biological production. Hydrographic characteristics of NEAS during Late Winter Monsoon (LWM) and Early Spring Inter Monsoon (ESIM) and the...

The state of the ocean simulated through a numerical model is extremely sensitive to the forcing and hence, the choice of appropriate forcing is essential, in particular wind-fields. We compared Regional Ocean Modeling System (ROMS) simulations when forced with two different wind-fields derived from satellite sensors (scatterometers), namely QuickS...

Carbon uptake rates in a tropical eutrophic estuary (Cochin estuary) and the adjacent coastal Arabian Sea were measured for the first time using 13C-NaHCO3 labelling technique. The rates in the estuarine water (pre-monsoon: 3.0-20.4; monsoon: 2.55-12.4; post-monsoon: 3.1-16.3 µmol C l-1 h-1) were significantly higher than the coastal locations (pre...

Repeat measurements of dissolved nitrous oxide (N2O) along two transects of the western continental shelf of India in 2012 revealed high concentrations of 45±32 nM (off Kochi) and 73±63 nM (off Mangalore) during the summer monsoon (SM). N2O concentrations increased non-linearly during the peak of the SM upwelling, when low O2 (<25 µM) conditions pr...

The core objective of the Marine Living Resource Program (MLRP) has been to delineate and quantify marine living resources of the country’s vast exclusive economic zone (EEZ), to understand the complex environmental regimes influencing their distribution, and to conduct R&D activities related to marine living resources. The programme was initiated...

The objectives of the present study were to evaluate the ecological status of tropical coastal waters using the temperate benthic indices and examine the effect of seasonal variability on the performance of benthic indices. Macrobenthic samples were collected from northwest to southeast coast of India during 2003–2012 and we tested different univar...

Detailed measurements of carbon (C) isotopic composition in dissolved inorganic ( 13CDIC) and particulate organic ( 13CPOC) fractions were conducted at 18 stations in the Cochin estuary during the post-monsoon season. In general, C biogeochemistry of different regions of the Cochin estuary appears to be regulated by different sources and processe...

Please read it full online at "EOS - Earth & Space Science News" doi:10.1029/2016EO046753. Off the coast of southwestern India, seasonal upwelling affects seawater composition and biological activity. Understanding these changes is important for predicting the potential impacts of human activity in the Arabian Sea, a tropical marine ecosystem. In...

Observations along ten shelf transects in 2012 near 10°N in the southeastern Arabian Sea revealed the usual warm oligotrophic conditions during the winter monsoon (WM) and upwelling of oxygen-deficient, nutrient-rich cool water during the summer monsoon (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major pr...

Supplementary Figures of the article 'Evolution to decay of Upwelling and associated Biogeochemistry over the southeastern Arabian Sea shelf', Journal of Geophysical Research - Biogeosciences, 121, 159-175, doi: 10.1002/2015JG003163

Quantification of nitrogen (N) transformation rates in tropical estuarine-coastal waters coupled systems undergoing anthropogenic disturbances is scant. A thorough understanding of these metabolic rates is required to evolve a mitigation strategy to save such systems from further degradation. Here, we report the first measurements of ammonium (NH4+...

Characteristics of a cold-core eddy and its influence on the mesozooplankton community were studied along the central (87°E) Bay of Bengal during winter monsoon (November, 2008) based on in situ data. The thermo-haline structure and the satellite derived sea level anomaly maps showed the presence of a cyclonic eddy between 16°N and 20°N. The nutrie...

The south eastern Arabian Sea is characterized by intense coastal upwelling, high biological production and subsurface oxygen depletion during the southwest monsoon (June-September). Concurrently, a seasonal closure to trawling activities (15th June to 31st July) is implemented here, as a sustainable ecosystem management practice. The effects of mo...

Coastal lagoons around the world have become increasingly vulnerable to eutrophication and often the impingement is severe with regard to plankton. In this study, we measured how environmental heterogeneity persuades mesozooplankton (MSP) community dynamics in a large tropical coastal lagoon wrought by human impingement, including the creation of a...

The winter monsoon season, spanning from November to February usually represents a quiescent period of the South Eastern Arabian Sea (SEAS). Seasonally reversing circulation plays an important role in exchanging water mass between the Arabian Sea and Bay of Bengal. lntrusion of BoB low saline water starts in November concurrent with the initial pha...

Coastal lagoons are known to have high physico-chemical and biological variability over both spatial and temporal scales often as a result of anthropogenic effects. Chilka Lake, Asia’s largest brackish water lagoon on the east coast of India, is one such example of human intervention (e.g. creation of a new inlet opening) affecting its hydrochemist...

Symbiotic diatom-diazotrophic cyanobacteria association (DDA) of Rhizosolenia hebetata and Rhizosolenia formosa with endosymbiotic cyanobacteria Richelia intracellularis was noticed and documented for the first time during a bloom of the cyanobacterium Trichodesmium erythraeum in the oligotrophic shelf waters along Kochi and Mangalore transects, so...

The influence of anthropogenic loading on the distribution of soft bottom benthic organisms of a tropical estuary (Cochin backwaters) was examined. The industrial activities were found to be high in the northern and central part of the estuary, where dissolved inorganic nitrogen (DIN > 210 μM) and phosphorus (DIP > 6.5 μM) have caused high abundanc...

Carbon biogeochemistry of a tropical ecosystem (The Cochin Estuary, India) undergoing increased human intervention was studied during February (premonsoon), April (early monsoon) and September (monsoon) 2005. The Cochin estuary sustains high levels of pCO2 (up to 6000 μatm) and CO2 effluxes (up to 274 mmolC m−2 d−1) especially during monsoon. A fir...

Carbon biogeochemistry of a tropical ecosystem (The Cochin Estuary, India) undergoing increased human intervention was studied during February (premonsoon), April (early monsoon) and September (monsoon) 2005. The Cochin estuary sustains high levels of pCO sub(2) (up to 6000 mu atm) and CO sub(2) effluxes (up to 274 mmolC m sup(-2) d sup(-1)) especi...

Bacterial productivity (BP) and respiration (BR) were examined in relation to primary productivity (PP) for the first time in a shallow tropical ecosystem (Cochin Estuary), India. The degree of dependence of BP (6.3–199.7 μg C L−1 d−1) and BR (6.6–430.4 μg C L−1 d−1) on PP (2.1–608.0 μg C L−1 d−1) was found to be extremely weak. The BP/PP (0.05–8.5...

Biolog plates were used to study the changes in the metabolic capabilities of bacterioplankton over a complete tidal cycle in a tropical ecosystem (Cochin Estuary, Kerala, India) along southwest coast of India. The pattern of utilization of carbon sources showed a definite shift in the community metabolism along a salinity gradient. Multivariate st...

Studies on biogeochemical cycling of carbon in the Chilka Lake, Asia’s largest brackish lagoon on the east coast of India, revealed, for the first time, strong seasonal and spatial variability associated with salinity distribution. The lake was studied twice during May 2005 (premonsoon) and August 2005 (monsoon). It exchanges waters with the sea (B...

Cochin backwaters, a micro tidal estuary, undergo a characteristic transformation from a river dominated system during summer monsoon to a tide-dominant system during pre-monsoon season. The present study observes that as the river flow weakens after monsoon, the flushing of the estuary diminishes and the nitrogen and phosphorous loadings through a...

Bacterial productivity (BP) and respiration (BR) were examined in relation to primary productivity (PP) for the first time in a shallow tropical ecosystem (Cochin Estuary), India. The degree of dependence of BP (6.3-199.7 mg C L-1 d-1) and BR (6.6-430.4 mg C L-1 d-1) on PP (2.1-608.0 mg C L-1 d-1) was found to be extremely weak. The BP/PP (0.05-8.5...

Environmental studies in the Cochin backwaters (CBW), a tropical estuary along the southwest coast of India showed that seasonal fluctuations in salinity created by the monsoonal rainfall and associated run off is a major factor controlling the distribution and abundance of micro- and mesozooplankton. During premonsoon season, the CBW was character...

Budgets of nitrogen and phosphorus from the semi-enclosed Muthupet lagoon were constructed through monsoon observations and modelling. The lagoon is a shallow water body and hence surface water samples associated with the lagoon were collected and measured for hydrochemical properties, inorganic and organic nutrients (dissolved inorganic nitrogen,...

Chemical properties of the water column were examined at the Indian Deep-sea Environment Experiment (INDEX) site in the Central Indian Basin (CIB), as a part of baseline studies prior to the benthic disturbance experiment for the environmental impact assessment of mining of polymetallic nodules. The study shows three equatorward moving water masses...

A two-gyre circulation system consisting of an anticyclonic gyre (ACG) in the northwestern Bay of Bengal and a cyclonic gyre (CG) west of the Andaman Islands is shown by the hydrographic data collected during May–June, prior to the southwest monsoon of 1996. This circulation system leads to an intense southwestward flow in the central Bay. The circ...

During RV Gaveshani cruise No. 235 (August-September, 1993), particulate matter was collected from euphotic and deeper waters in the Bay of Bengal and analysed for biogenic silica (BSi), lithogenic silica (LSi) and particulate organic carbon (POC). Mean depth profiles of BSi showed a minimum in the surface waters and a maximum in the middle depths...