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Shetye S, Kurian S, Shenoy D, Gauns M, Pratihary A, Shirodkar G, Naik H, Fernandes M, Vidya P, Nandakumar K, Shaikh A. Contrasting patterns in pH variability in the Arabian Sea and Bay of Bengal. Environ Sci Pollut Res Int 2024; 31:15271-15288. [PMID: 38289549 DOI: 10.1007/s11356-024-31950-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 01/05/2024] [Indexed: 02/24/2024]
Abstract
Continuous understanding of the ongoing ocean acidification (OA) is essential for predicting the future impact of OA on marine ecosystems. Here we report the results of open ocean time-series measurements (19 cruises) of seawater pH in total hydrogen ion scale (pHT) and associated parameters in the Arabian Sea (AS) and the Bay of Bengal (BoB). During southwest monsoon (SWM), the pHT within the 30 to 100 m water column shows the maximum difference between the two basins with BoB pHT being lower (up to ~0.39 units) than AS which could be due to freshwater influx from rivers, mixed layer dynamics, and cold-core eddies. However, during Spring inter-monsoon (SIM), the pHT of BoB follows the trend of AS. A contrasting finding is that the lowest pHT occurs at 350 to 500 m in the BoB while it is ~1000 m in the AS. The pHT within the 150 to 1500 m layer of these two basins shows lower values by 0.03 (±0.02) in the BoB as compared to the AS. The possible reasons for the low pHT within the BoB oxygen minimum zone (OMZ) could be due to intrusion of western Pacific water in the BoB, freshwater influx from rivers, variations in OMZ of the two basins, higher temperature (~2°C) within the OMZ of the AS, and denitrification in the AS. The pHT in both the basins (500 to 1000 m) is lower than in the North Atlantic and higher than in the North Pacific waters; however, the pHT in the 200 to 500 m is lower in the BoB than in all these basins. This study highlights the under-saturation of calcium carbonate at very shallow depths (~ 100 m) in the BoB, indicating that the plankton in the BoB are facing a major risk from OA compared to the AS and need further investigation.
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Affiliation(s)
- Suhas Shetye
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India.
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Damodar Shenoy
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Anil Pratihary
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Gayatri Shirodkar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Hema Naik
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Michelle Fernandes
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Pottekkatt Vidya
- National Centre for Polar and Ocean Research (NCPOR), Ministry of Earth Sciences, Headland Sada, Goa, 403 804, India
| | - Kuniyil Nandakumar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Adnan Shaikh
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
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Garg S, Gauns M, Pratihary AK. Response of oceanic subsurface chlorophyll maxima to environmental drivers in the Northern Indian Ocean. Environ Res 2024; 240:117528. [PMID: 37898227 DOI: 10.1016/j.envres.2023.117528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 10/30/2023]
Abstract
Subsurface Chlorophyll Maxima (SCM) contributes a significant proportion to depth-integrated ocean primary production, making it important to understand its spatiotemporal variability in changing environmental conditions. Based on field observations and in situ data, we studied SCM characteristics in four distinct environmental settings across Northern Indian Ocean: SEAS-south eastern Arabian Sea (coastal upwelling zone), SAS-Southern Arabian Sea (Arabian Sea mini warm pool-ASMWP), SBOB-Southern Bay of Bengal (presence of mesoscale eddies) and ANS-Andaman Sea (region of active volcanoes). SCM displayed significant spatial variability: ZSCM (SCM depth) ranged between 25 and 88 m (mean = 59.5 m), Chlmax (SCM magnitude) ranged between 0.07 and 0.2 mg m-3 (mean = 0.12 mg m-3) while TSCM (SCM thickness) ranged between 33 and 100 m (mean = 69 m). Major factors affecting the ZSCM were light and nutrients, since ZSCM was closely related to Zeu (euphotic depth) and ZN (nitracline depth). Positive relation between Chlmax and micro phytoplankton suggests micro phytoplankton to be a major contributor in increasing Chlmax. TSCM was associated to ZT (thermocline depth) and nutrient concentration. Increase in stratification and oligotrophy, resulted in deeper, thicker peaks of lower magnitude, and such nature of peaks could increase in continued warming scenarios. Dinoflagellates increased in warmer oligotrophic environments. Nanophytoplankton were higher at deeper ZSCM, possibly due to their adaptability to low light. Upwelling caused shoaling of SCM with higher Chlmax in SEAS. SCM deepened in SAS and SBOB, dominated by picophytoplankton due to the influence of ASMWP (in SAS) and anticyclonic eddy (in SBOB). Ammonia and nutrient inputs from submarine vents in ANS, caused shoaling of ZN and ZSCM. Globally, multiple physical processes operate at short spatiotemporal scale, causing SCM variability, and the same should not be overlooked while estimating primary production or carbon export to deep ocean, through generalisations established at larger scale in the world ocean.
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Affiliation(s)
- Shriya Garg
- Academy of Scientific and Innovative Research (AcSIR), Gaziabad, India; CSIR- National Institute of Oceanography, Goa, 403004, India
| | - Mangesh Gauns
- Academy of Scientific and Innovative Research (AcSIR), Gaziabad, India; CSIR- National Institute of Oceanography, Goa, 403004, India.
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Shetye S, Pratihary A, Shenoy D, Kurian S, Gauns M, Uskaikar H, Naik B, Nandakumar K, Borker S. Rice husk as a potential source of silicate to oceanic phytoplankton. Sci Total Environ 2023; 879:162941. [PMID: 36934917 DOI: 10.1016/j.scitotenv.2023.162941] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 03/10/2023] [Accepted: 03/14/2023] [Indexed: 05/17/2023]
Abstract
Global oceans are witnessing changes in the phytoplankton community composition due to various environmental stressors such as rising temperature, stratification, nutrient limitation, and ocean acidification. The Arabian Sea is undergoing changes in its phytoplankton community composition, especially during winter, with the diatoms being replaced by harmful algal blooms (HABs) of dinoflagellates. Recent studies have already highlighted dissolved silicate (DSi) limitation and change in Silicon (Si)/Nitrogen (N) ratios as the factors responsible for the observed changes in the phytoplankton community in the Arabian Sea. Our investigation also revealed Si/N < 1 in the northern Arabian Sea, indicating DSi limitation, especially during winter. Here, we demonstrate that rice husk with its phytoliths is an important source of bioavailable DSi for oceanic phytoplankton. Our experiment showed that a rice husk can release ∼12 μM of DSi in 15 days and can release DSi for ∼20 days. The DSi availability increased diatom abundance up to ∼9 times. The major benefitted diatom species from DSi enrichment were Nitzshia spp., Striatella spp., Navicula spp., Dactiliosolen spp., and Leptocylindrus spp. The increase in diatom abundance was accompanied by an increase in fucoxanthin and dimethyl sulphide (DMS), an anti-greenhouse gas. Thus, the rice husk with its buoyancy and slow DSi release has the potential to reduce HABs, and increase diatoms and fishery resources in addition to carbon dioxide (CO2) sequestration in DSi-limited oceanic regions such as the Arabian Sea. Rice husk if released at the formation site of the Subantarctic mode water in the Southern Ocean could supply DSi to the thermocline in the global oceans thereby increasing diatom blooms and consequently the biotic carbon sequestration potential of the entire ocean.
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Affiliation(s)
- Suhas Shetye
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India.
| | - Anil Pratihary
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Damodar Shenoy
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Hema Uskaikar
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Bhagyashri Naik
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - K Nandakumar
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Sidhesh Borker
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
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Dias AB, Kurian S, Vijayan NT, Gauns M, Khichi R, Pratihary AK, Borker SG, Shenoy DM. Recurrence of Gonyaulax polygramma bloom in the southeastern Arabian Sea. Environ Monit Assess 2023; 195:635. [PMID: 37133635 DOI: 10.1007/s10661-023-11278-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 04/19/2023] [Indexed: 05/04/2023]
Abstract
Gonyaulax polygramma, a bloom-forming dinoflagellate, has been repeatedly observed along the southeastern Arabian Sea in recent years. During our study in October 2021, a patch of reddish-brown water was observed in the nearshore waters off Kannur (southwest coast of India) and later identified as Gonyaulax polygramma using scanning electron microscopy (SEM) and HPLC-based phytoplankton marker pigments. Gonyaulax polygramma accounted for 99.4% of the phytoplankton abundance at the bloom location, with high concentrations of peridinin and chlorophyll-a at the study site. High concentration of SiO42- was observed at the bloom site, while other nutrients were lower than the previously reported values. The bloom of Gonyaulax polygramma also resulted in high concentrations of dimethylsulfide, an anti-greenhouse gas, at the bloom site. In addition to onsite observation, Sentinel-3 satellite data was also used in the detection and validation of the observed bloom using the NDCI index. From the satellite image, it was evident that the bloom persisted at the mouth of the rivers during the study period. Since the red tide of Gonyaulax polygramma has been observed recurrently in the southeastern Arabian Sea, it is proposed to use satellites to detect and monitor the bloom on a routine basis.
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Affiliation(s)
- Albertina B Dias
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
| | - Neethu T Vijayan
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Rahul Khichi
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Anil K Pratihary
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Sidhesh G Borker
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Damodar M Shenoy
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
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Shetye S, Gazi S, Manglavil A, Shenoy D, Kurian S, Pratihary A, Shirodkar G, Mohan R, Dias A, Naik H, Gauns M, Nandakumar K, Borker S. Malformation in coccolithophores in low pH waters: evidences from the eastern Arabian Sea. Environ Sci Pollut Res Int 2023; 30:42351-42366. [PMID: 36648723 DOI: 10.1007/s11356-023-25249-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 01/06/2023] [Indexed: 01/18/2023]
Abstract
Oceanic calcifying plankton such as coccolithophores is expected to exhibit sensitivity to climate change stressors such as warming and acidification. Observational studies on coccolithophore communities along with carbonate chemistry provide important perceptions of possible adaptations of these organisms to ocean acidification. However, this phytoplankton group remains one of the least studied in the northern Indian Ocean. In 2017, the biogeochemistry group at the Council for Scientific and Industrial Research-National Institute of Oceanography (CSIR-NIO) initiated a coccolithophore monitoring study in the eastern Arabian Sea (EAS). Here, we document for the first time a detailed spatial and seasonal distribution of coccolithophores and their controlling factors from the EAS, which is a well-known source of CO2 to the atmosphere. To infer the seasonality, data collected at three transects (Goa, Mangalore, and Kochi) during the Southwest Monsoon (SWM) of 2018 was compared with that of the late SWM of 2017. Apart from this, the abundance of coccolithophores was studied at the Candolim Time Series (CaTS) transect, off Goa during the Northeast Monsoon (NEM). The most abundant coccolithophore species found in the study region was Gephyrocapsa oceanica. A high abundance of G. oceanica (1800 × 103cells L-1) was observed at the Mangalore transect during the late SWM despite experiencing low pH and can be linked to nitrogen availability. The high abundance of G. oceanica at Mangalore was associated with high dimethylsulphide (DMS). Particulate inorganic carbon (PIC) and scattering coefficient retrieved from satellites also indicated a high abundance of coccolithophores off Mangalore during the late SWM of 2017. Interestingly, G. oceanica showed malformation during the late SWM in low pH waters. Malformation in coccolithophores could have a far-reaching impact on the settling fluxes of organic matter and also on the emissions of climatically important gases such as DMS and CO2, thus influencing atmospheric chemistry. The satellite data for PIC in the EAS indicates a high abundance of coccolithophore in recent years, especially during the warm El Nino years (2015 and 2018). This warrants the need for a better assessment of the fate of coccolithophores in high-CO2 and warmer oceans.
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Affiliation(s)
- Suhas Shetye
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
| | - Sahina Gazi
- ESSO-National Centre for Polar & Ocean Research, Headland Sada, Goa, 403804, India
| | - Arundhathy Manglavil
- Regional Centre, CSIR-National Institute of Oceanography, Kochi, Kerala, 628018, India
| | - Damodar Shenoy
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Anil Pratihary
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Gayatri Shirodkar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Rahul Mohan
- ESSO-National Centre for Polar & Ocean Research, Headland Sada, Goa, 403804, India
| | - Albertina Dias
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Hema Naik
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | | | - Sidhesh Borker
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
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Shetye SS, Nandakumar K, Kurian S, Gauns M, Shenoy DM, Naik H, Vidya PJ, Karapurkar SG. Organic carbon dynamics in the continental shelf waters of the eastern Arabian Sea. Environ Monit Assess 2022; 194:716. [PMID: 36048260 DOI: 10.1007/s10661-022-10390-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 08/12/2022] [Indexed: 06/15/2023]
Abstract
The seasonal and spatial distribution of total organic carbon (TOC) is presented for the coastal waters of the eastern Arabian Sea, which experiences seasonal suboxia during the late southwest monsoon (SWM). This study reveals that high TOC was observed off Kochi as compared to Goa and Mangalore transects, and may be attributed to stronger upwelling along the Kerala coast. This is also supported by the excess carbon due to upwelling during the late SWM that varied from 37 μM (Goa), 39 μM (Mangalore), to 51 μM (Kochi). Our seasonal data from 2014 to 2020 at the Goa transect indicates that high TOC is seen during late SWM to fall inter monsoon (FIM) and between the late northeast monsoon (NEM) to the early spring inter monsoon (SIM). The high TOC concentrations and C/N ratios observed during the FIM are a combination of high primary production, the buildup of remnant organic matter from the previous season (due to prevailing low oxygen conditions), accumulation of refractory organic carbon, and release from diatoms (especially Chaetoceros sp.). Inter-annual variations indicate that phytoplankton blooms resulted in higher TOC concentrations, especially during the year 2020. Based on a comparison with an Elnino-Southern Oscillation (ENSO) year (2015), we can infer that the partitioning of carbon may increase from particulate to dissolved phase in future warming scenarios.
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Affiliation(s)
- Suhas S Shetye
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India.
| | - K Nandakumar
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India
| | - Damodar M Shenoy
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India
| | - Hema Naik
- CSIR-National Institute of Oceanography, Dona Paula-403 004, Goa, India
| | - P J Vidya
- National Centre for Polar & Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa-8403 804, Goa, India
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Shenoy DM, Kurian S, Shirodkar G, Uskaikar H, Gauns M, Naqvi SWA. Impact of physical processes on oxygen loss and production of hydrogen sulphide and methane in a tropical freshwater reservoir. Environ Sci Pollut Res Int 2021; 28:39655-39667. [PMID: 33761073 DOI: 10.1007/s11356-021-13472-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 03/11/2021] [Indexed: 06/12/2023]
Abstract
Carbon neutrality of tropical reservoirs is a big concern in recent years as some estimates project high methane emission from these reservoirs. While there are studies available on the impact of physical processes (stratification and mixing) on the biogeochemistry of tropical reservoirs, not much information is available on the inter-annual variability in the low-oxygen conditions and production/accumulation of hydrogen sulphide (H2S) and methane (CH4) during summer. This paper presents time series data based on monthly in situ observations from a tropical reservoir (Tillari, Maharashtra) situated in the Western Ghats in India. Sampling was carried out for temperature, dissolved oxygen (DO), H2S, and CH4 at a fixed location from March 2010 until June 2014. The reservoir experiences stable stratification during summer (March to June) with complete loss of oxygen and production of H2S (max. ~ 9 μM) and CH4 (max. ~ 185 μM) in the profundal zone. During the summer stratification, the hypolimnion acted as a pool of CH4 with integrated values ranging between 3502 and 41,632 mg m-2. However, the intensity and duration of anoxia varied during different years, influencing H2S and CH4 production. Mixing in the reservoir was observed between July and September in association with the monsoonal runoff, which increased the DO concentrations in the sub-surface layers. Besides, complete mixing was observed between December and February due to winter convection. This, however, was found to play an important role, as weaker mixing in the preceding year was associated with severe oxygen loss in the profundal zone during the following summer with a production of H2S and CH4. In contrast, more robust mixing during winter led to moderate low-oxygen conditions with less production of these gases in the subsequent summer. Based on our observations and considering a large number of reservoirs in the tropics, we hypothesise that with the present trends of global warming and less cold winters, low-oxygen conditions in the profundal zone may become more severe in the future with positive feedback on H2S and CH4 production during summer.
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Affiliation(s)
- Damodar M Shenoy
- Chemical Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
| | - Siby Kurian
- Chemical Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Gayatri Shirodkar
- Chemical Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Hema Uskaikar
- Chemical Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Mangesh Gauns
- Chemical Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
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Narvenkar G, Naqvi SWA, Kurian S, Shenoy DM, Pratihary AK, Naik H, Patil S, Sarkar A, Gauns M. Correction to: Dissolved methane in Indian freshwater reservoirs. Environ Monit Assess 2021; 193:217. [PMID: 33758970 DOI: 10.1007/s10661-021-08983-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- G Narvenkar
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India.
| | - S W A Naqvi
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - S Kurian
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - D M Shenoy
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - A K Pratihary
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - H Naik
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - S Patil
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - A Sarkar
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
| | - M Gauns
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India
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Shetye SS, Kurian S, Vidya PJ, Gauns M, Shenoy DM, Aparna SG, Nandakumar K, Karapurkar SG. Total organic carbon and its role in oxygen utilization in the eastern Arabian Sea. Mar Pollut Bull 2021; 163:111939. [PMID: 33383319 DOI: 10.1016/j.marpolbul.2020.111939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 12/03/2020] [Accepted: 12/05/2020] [Indexed: 06/12/2023]
Abstract
We report seasonal and temporal variation of total organic carbon (TOC) in the eastern Arabian Sea (AS). In comparison to the deep, TOC in the top 100 m showed spatial variation with higher concentrations towards northern AS during North east monsoon (NEM) and South west monsoon (SWM). A comparison with the US-JGOFS data (1995) shows warmer temperatures, enhanced TOC and low chlorophyll in the recent years. High TOC is associated with Arabian Sea high saline waters (ASHSW), advected from the Arabian Gulf, might have resulted in an enhancement of TOC in the eastern AS. This excess TOC supports a high abundance of bacteria despite the low primary productivity. TOC oxidation accounted for 14.3% and 22.5% of oxygen consumption for waters with potential density between 24.5 and 27.3 kg/m3. This study attains great significance considering the missing links with respect to the role of transport processes in ocean deoxygenation under ongoing warming scenarios.
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Affiliation(s)
- Suhas S Shetye
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India.
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - P J Vidya
- National Centre for Polar & Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa 403 804, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Damodar M Shenoy
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - S G Aparna
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - K Nandakumar
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
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Shetye SS, Bandekar M, Nandakumar K, Kurian S, Gauns M, Jawak S, Pratihary A, Elangovan SS, Naik BR, Lakshmi S, Aswathi VK. Sea foam-associated pathogenic bacteria along the west coast of India. Environ Monit Assess 2021; 193:27. [PMID: 33389180 DOI: 10.1007/s10661-020-08783-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 11/30/2020] [Indexed: 06/12/2023]
Abstract
Anthropogenic activities release effluents containing nutrients and pathogenic bacteria that change the characteristics of coastal ecosystems. An important type of marine pollution which has occurred in 3 different states in India during 2019 is sea foam. Sea foam was found on Hole beach, Goa (Lat: 15.404° N, Long: 73.787° E), where nutrients (NO3- = 137 μM and organic nitrogen = 121 μM) from a garbage dumpyard are released directly via streams/gutters to coastal waters. This resulted in a bloom of the diatom Thalassiosira pseudonana, associated with high concentration of total organic carbon and fucoxanthin. Decay of this bloom along with strong agitation due to rocks and wave action resulted in sea foam. We isolated foam-associated bacteria and identified pathogenic bacteria including Enterobacter cancerogenus through 16S rRNA gene sequencing. Such foam-associated pathogenic bacteria, could be antibiotic resistant, and may have adverse effects on human health. This can also hamper the tourism industry of a small state like Goa that relies heavily on tourism.
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Affiliation(s)
- Suhas S Shetye
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India.
| | - Mandar Bandekar
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | | | - Siby Kurian
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - Shridhar Jawak
- Svalbard Integrated Arctic Earth Observing System (SIOS), SIOS Knowledge Centre, Svalbard Science Centre, P.O. Box 156, N-9171, Longyearbyen, Svalbard, Norway
| | - Anil Pratihary
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - S Sai Elangovan
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - Bhagyashri R Naik
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - Sethu Lakshmi
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
| | - V K Aswathi
- CSIR-National Institute of Oceanography, Donapaula, Goa, 403004, India
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11
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Kurian S, Chndrasekhararao AV, Vidya PJ, Shenoy DM, Gauns M, Uskaikar H, Aparna SG. Role of oceanic fronts in enhancing phytoplankton biomass in the eastern Arabian Sea during an oligotrophic period. Mar Environ Res 2020; 160:105023. [PMID: 32907734 DOI: 10.1016/j.marenvres.2020.105023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/04/2020] [Accepted: 05/19/2020] [Indexed: 06/11/2023]
Abstract
In the present study, using in-situ and satellite observations, we investigate the influence of physical processes on the enhancement of phytoplankton biomass in the eastern Arabian Sea (EAS). Water column measurements were carried out from 9⁰N to 21⁰N (stations II-2 to II-14) along 68⁰E transect in the EAS during the beginning of fall intermonsoon (FIM) of 2014. Both in-situ and satellite-derived chlorophyll a (Chl a) showed higher biomass at 15⁰N (station II-8) compared to northern and southern stations. We explored the possible physical processes which can lead to high biological productivity at this station. Our study shows that nearly two times enhancement in Chl a at station II-8 was contributed by an open-ocean front, which occurred two days before the measurement. Based on phytoplankton marker pigments, it was evident that haptophytes were abundant at II-8 with a minor contribution from diatoms and dinoflagellates. This condition also led to a high concentration (4.9 nM) of dimethylsulphide (DMS), an anti-green house gas with a net flux of 3.76 μmol m-2d-1 at this site. Among the picophytoplankton, Synechococcus were abundant at this station, however Prochlorococcus were absent as confirmed by both marker pigment and flow cytometric counts. The case study presented here demonstrates the dynamic nature of open ocean fronts and their overall contribution to the productivity of the eastern Arabian Sea during the oligotrophic inter-monsoon period.
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Affiliation(s)
- Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India.
| | - A V Chndrasekhararao
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India; Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620 024, India
| | - P J Vidya
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Damodar M Shenoy
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - Hema Uskaikar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
| | - S G Aparna
- CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India
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12
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Naik BR, Gauns M, Bepari K, Uskaikar H, Shenoy DM. Variation in phytoplankton community and its implication to dimethylsulphide production at a coastal station off Goa, India. Mar Environ Res 2020; 157:104926. [PMID: 32275508 DOI: 10.1016/j.marenvres.2020.104926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 02/04/2020] [Accepted: 02/23/2020] [Indexed: 06/11/2023]
Abstract
Seasonal hypoxia/suboxia (at times anoxia) towards the end of Southwest monsoon (SWM; June to September) at the coastal time series site off Goa, West coast of India was found to influence the dynamics of phytoplankton biomass, community structure and production of climatically active gas, dimethylsulphide (DMS). In this diatom dominated study region, high DMS production in the subsurface waters during late SWM might possible be attributed to the stress experienced by micro- and macro-algae from the prevailing low oxygen subsurface waters through different pathways specifically believed to be via methylation pathway (see Schafer et al., 2010). Based on laboratory experiments, we hypothesize presence of floating seaweeds mostly Sargassum species washed from the shore to the study site to contribute sizably to DMS production in the water column as they sink and degrade during the senescence phase. However, we are yet to address its loss/emission processes across the oxic-hypoxic boundary of seasonal (and permanent) oxygen minimum zone of the northern Indian Ocean, which is important from the viewpoint of global climate change.
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Affiliation(s)
- Bhagyashri R Naik
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India; School of Earth, Ocean and Atmospheric Sciences, Goa University, Taleigao Plateau, Goa, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India.
| | - Kausar Bepari
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India; Centre for Marine Living Resources and Ecology, Kochi, Kerala, India
| | - Hema Uskaikar
- CSIR-National Institute of Oceanography, Dona Paula, Goa, India
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13
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Shetye SS, Kurian S, Naik H, Gauns M, Chndrasekhararao AV, Kumar A, Naik B. Variability of organic nitrogen and its role in regulating phytoplankton in the eastern Arabian Sea. Mar Pollut Bull 2019; 141:550-560. [PMID: 30955767 DOI: 10.1016/j.marpolbul.2019.02.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 01/27/2019] [Accepted: 02/16/2019] [Indexed: 06/09/2023]
Abstract
The relative importance of organic nitrogen (ON) and inorganic nitrogen (IN) as nitrogen sources for the phytoplankton communities were studied through a seasonal time series of nitrogen species in the eastern Arabian Sea. Seasonal data on nitrogen species showed that ON dominates the system throughout the year and account for >90% of the total nitrogen (TN) during north east monsoon (NEM). The average ON concentration in the study region was 11.5 μM during NEM as compared to 7.2 μM during south west monsoon (SWM). The contribution of picoplankton to the total phytoplankton pool (fpico) increased from 19% during SWM to 36% in NEM. Along with cyanobacteria, the diatoms Thalassionema nitzchoides and Thalassiosira sp. and among the dinoflagellates Pronoctiluca sp. were found to proliferate in ON rich waters. We suggest atmospheric deposition, riverine-input, resuspension of bottom sediment and ground water intrusion as the possible sources of ON in the study region.
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Affiliation(s)
- Suhas S Shetye
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India.
| | - Siby Kurian
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Hema Naik
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Mangesh Gauns
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | | | - Ashwini Kumar
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
| | - Bhagyashri Naik
- CSIR-National Institute of Oceanography, Dona Paula 403 004, Goa, India
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14
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Sai Elangovan S, Gauns M. A checklist of tintinnids (loricate ciliates) from the coastal zone of India. Environ Monit Assess 2018; 190:672. [PMID: 30361771 DOI: 10.1007/s10661-018-7039-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 10/08/2018] [Indexed: 06/08/2023]
Abstract
We report here a checklist of tintinnids (loricate ciliates) for the coastal zone of India. Based on available literature (1978 to 2017), a total of 25 stations were studied from 5 distinct areas of Indian coastal waters. A total of 151 species of 33 genera belonging to 14 families of tintinnids were documented. Diversity patterns of tintinnids were recorded higher along the west coast (30 genera and 106 species) than the east coast of India (20 genera and 93 species). Among tintinnids families, the Codonellidae (2 genera and 52 species, 20%) and the Tintinnidae (8 genera and 21 species, 19%) are the major contributors to the total tintinnids diversity in the Indian coastal zone.
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Affiliation(s)
- S Sai Elangovan
- Biological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Mangesh Gauns
- Biological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
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15
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Shenai-Tirodkar P, Gauns M, Kumar G, Ansari Z. Seasonal variations and relationships between environmental parameters and heavy metal concentrations in tissues of Crassostrea species and in its ambience from the tropical estuaries. Environ Sci Pollut Res Int 2018; 25:20930-20945. [PMID: 29766426 DOI: 10.1007/s11356-018-2258-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 05/07/2018] [Indexed: 06/08/2023]
Abstract
This study aimed to evaluate the relationship between physicochemical parameters and heavy metal (Cu, Ni, Pb, and Cd) concentrations from sediment, seawater, and its accumulation in tissues of oyster species (Crassostrea madrasensis and C. gryphoides) from the three sites (Chicalim Bay (CB), Nerul Creek (NC), Chapora Bay (ChB)) along the Goa coast (India). Results showed enrichment of Cu and Ni in sediment exceeding the effect range low (ERL) level. The higher concentrations of Cu and Ni in sediments and in suspended particulate matter (SPM) from all the study sites are indicative of severe contamination of estuarine and associated habitats. Moreover, particulate Ni (at all the sites), Cu (at NC and ChB), Pb (at NC), and Cd (at CB and NC) concentrations were recorded more than its total loadings in surface sediment. Concentration of Cu and Cd in oyster tissue was several folds higher than its concentration in ambience. Further, this study showed that the levels of metal in oysters and their ambient environment were higher during the monsoon season. Hence, the consumption of oysters needs to be considered carefully with respect to the health hazards posed by the elevated levels of metal contaminants in certain seasons. The present study concludes that metals associated with the particulate matter in water column are the main source of metal accumulation in oyster. It is also suggested that concentration of metal pollutants in coastal and estuarine water bodies should be monitored regularly to ensure the acceptable limits of metal concentrations.
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Affiliation(s)
- Prachi Shenai-Tirodkar
- Biological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India.
| | - Mangesh Gauns
- Biological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
| | - Girish Kumar
- Department of Zoology, DAV University, Pathankot, Jalandhar, Punjab, 144012, India
| | - Zakir Ansari
- Biological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa, 403004, India
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16
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Gauns M, Mochemadkar S, Pratihary A, Roy R, Ahmad Naqvi SW. Biogeochemistry and ecology of Pyrosoma spinosum from the Central Arabian Sea. Zool Stud 2015; 54:e3. [PMID: 31966090 DOI: 10.1186/s40555-014-0075-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 11/14/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND A swarm of pelagic tunicate (Pyrosoma spinosum) was found in the surface open waters of the Arabian Sea during late southwest monsoon (September 2007). The swarm site was characterized by moderate southwesterly wind (approximately 7 m s-1), relatively low sea-surface temperature (approximately 26°C), shallow mixed layer (approximately 50 m), and substantial macro-nutrient concentrations (surface values: 2.5 μM nitrate, 0.3 μM phosphate, 0.9 μM silicate, and 5.0 μM ammonium). Despite adequate macronutrient availability, the swarm site was characterized by low diversity of phytoplankton (>5 μm) and mesozooplankton in the upper 200 m. Low chlorophyll a concentration (27.3 mg/m2 in the upper 120 m) at the swarm site was dominated (90% to 95% in the upper 40 m) by the Synechococcus (20 × 106 /ml). RESULTS Silicate deficiency in surface waters upwelled or entrained from the thermocline may be a key factor for the dominance of smaller autotrophs (flagellates and cyanobacteria) that seems to offer favorable conditions for episodic occurrence of swarms of these filter feeders. Low carbon content (37% of total dry weight) and the lower molar(carbon-to-nitrogen) ratio (5) in P.spinosum suggestgrowth of these organisms is carbon-limited. CONCLUSIONS Wedescribe various physicochemical and biological conditions at the P.spinosum swarmlocation and at two other nearby sites not affected by it. The biological factors predominantly high densities of Synechococcus and flagellates were best suited conditions for the proliferation of pyrosome biomass in the central Arabian Sea.
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Affiliation(s)
- Mangesh Gauns
- National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
| | - Sunita Mochemadkar
- National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
| | - Anil Pratihary
- National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
| | - Rajdeep Roy
- National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
| | - Syed Wajih Ahmad Naqvi
- National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
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Narvenkar G, Naqvi SWA, Kurian S, Shenoy DM, Pratihary AK, Naik H, Patil S, Sarkar A, Gauns M. Dissolved methane in Indian freshwater reservoirs. Environ Monit Assess 2013; 185:6989-6999. [PMID: 23397538 DOI: 10.1007/s10661-013-3079-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 01/03/2013] [Indexed: 06/01/2023]
Abstract
Emission of methane (CH4), a potent greenhouse gas, from tropical reservoirs is of interest because such reservoirs experience conducive conditions for CH4 production through anaerobic microbial activities. It has been suggested that Indian reservoirs have the potential to emit as much as 33.5 MT of CH4 per annum to the atmosphere. However, this estimate is based on assumptions rather than actual measurements. We present here the first data on dissolved CH4 concentrations from eight freshwater reservoirs in India, most of which experience seasonal anaerobic conditions and CH4 buildup in the hypolimnia. However, strong stratification prevents the CH4-rich subsurface layers to ventilate CH4 directly to the atmosphere, and surface water CH4 concentrations in these reservoirs are generally quite low (0.0028-0.305 μM). Moreover, only in two small reservoirs substantial CH4 accumulation occurred at depths shallower than the level where water is used for power generation and irrigation, and in the only case where measurements were made in the outflowing water, CH4 concentrations were quite low. In conjunction with short periods of CH4 accumulation and generally lower concentrations than previously assumed, our study implies that CH4 emission from Indian reservoirs has been greatly overestimated.
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Affiliation(s)
- G Narvenkar
- National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India.
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Shenoy DM, Paul JT, Gauns M, Ramaiah N, Kumar MD. Spatial variations of DMS, DMSP and phytoplankton in the Bay of Bengal during the summer monsoon 2001. Mar Environ Res 2006; 62:83-97. [PMID: 16644004 DOI: 10.1016/j.marenvres.2006.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 03/06/2006] [Accepted: 03/13/2006] [Indexed: 05/08/2023]
Abstract
Data on the distribution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in relation to phytoplankton abundance in different oceanic environments is important to understand the biogeochemistry of DMS, which plays an important role in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSPt (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSPt were restricted to the upper 40 m of the water column. Diatoms accounted for more than 95% of the phytoplankton and were the major contributors to the DMS and DMSPt pool. The mean concentration of DMS in the upper 40 m was observed to be around 1.8+/-1.9 nM in the study area, while DMSPt concentrations varied between 0.7 nM and 40.2 nM with a mean of 10.4+/-8.2 nM. The observed lower DMSPt in the northern Bay in spite of higher mean primary productivity, chlorophyll a and phytoplankton cell counts seemed to result from grazing. Though salinity divides the Bay into different biogeochemical provinces there is no relation between salinity and DMS or DMSPt. On the other hand DMS was linearly related to chlorophyll a:phaeopigments ratio. The results suggest the need for deeper insight into the role of diatoms in the biogeochemical cycling of DMS.
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Affiliation(s)
- D M Shenoy
- National Institute of Oceanography, Dona Paula, Goa 403 004, India.
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Patra PK, Lal S, Venkataramani S, Gauns M, Sarma VVSS. Seasonal variability in distribution and fluxes of methane in the Arabian Sea. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/97jc02590] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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