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Now showing items 1 - 13 of 13

  • A checklist of tintinnids (loricate ciliates) from the coastal zone of India.

    Sai Elangovan, S   Gauns, Mangesh  

    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.=20
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  • Biogeochemistry and ecology ofPyrosoma spinosumfrom the Central Arabian Sea

    Gauns, Mangesh   Mochemadkar, Sunita   Pratihary, Anil   Roy, Rajdeep   Naqvi, Syed  

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  • Observational insights into chlorophyll distributions of subtropical South Indian Ocean eddies

    Dufois, Francois   Hardman-Mountford, Nick J.   Fernandes, Michelle   Wojtasiewicz, Bozena   Shenoy, Damodar   Slawinski, Dirk   Gauns, Mangesh   Greenwood, Jim   Toresen, Reidar  

    The South Indian Ocean subtropical gyre has been described as a unique environment where anticyclonic ocean eddies highlight enhanced surface chlorophyll in winter. The processes responsible for this chlorophyll increase in anticyclones have remained elusive, primarily because previous studies investigating this unusual behavior were mostly based on satellite data, which only views the ocean surface. Here we present in situ data from an oceanographic voyage focusing on the mesoscale variability of biogeochemical variables across the subtropical gyre. During this voyage an autonomous biogeochemical profiling float transected an anticyclonic eddy, recording its physical and biological state over a period of 6weeks. We show that several processes might be responsible for the eddy/chlorophyll relationship, including horizontal advection of productive waters and deeper convective mixing in anticyclonic eddies. While a deep chlorophyll maximum is present in the subtropical Indian Ocean outside anticyclonic eddies, mixing reaches deeper in anticyclonic eddy cores, resulting in increased surface chlorophyll due to the stirring of the deep chlorophyll maximum and possibly resulting in new production from nitrate injection below the deep chlorophyll maximum.
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  • Epibiotic communities (microalgae and meiofauna) on the pneumatophores of Avicennia officinalis (L.)

    Sahoo, Gobardhan   Ansari, Z. A.   Shaikh, Jamila Bi   Varik, Sandesh U.   Gauns, Mangesh  

    In a mangrove environment, several groups of organisms are symbiotically associated with pneumatophores (aerial roots). But whether these organisms are exclusively found in this habitat (uniqueness) or accidentally settled here from water or sedimentary habitat, is not clearly understood. This hampers our understanding of their functional ecology. Hence the present study aimed to characterise the epibiotic microalga and meiofauna from the pneumatophores of mangrove Avicennia officinalis. To determine the habitat influence, these communities were also compared with those found in water and sedimentary habitat. Four estuarine mangrove sites represented by brackish water (salinity varying from 5 to 12) and located at different spatial scales (5-50 km distance) were chosen to determine whether these communities are consistent or vary with sites. Overall, the microalgal community was found to vary both among the habitats as well as sites. In the pneumatophore habitat, several tychoplanktons such as Coscinodiscus, Thalassionema, Cyclotella, Fragilariopsis, and Biddulphia were observed instead of benthic ones. These diatoms are planktonic genera and might have settled on pneumatophores from the water column. The observed variability in the microalgal composition among the sites is possibly due to predatory interactions or the dominance of particular species of macroalga that govern the diatom community. On the other hand, among the meiofaunal community, diptera, halacarida, tanaidacea, and foraminifera were mainly found in the pneumatophore habitat than in the sediment. Because pneumatophores either provide refugee to meiofauna against predators or are saturated with oxygen that meiofauna can utilize for respiration. Pneumatophores were also found to harbour several rare (abundance <1%) epibionts, the ecological importance of which is discussed in this paper. (C) 2017 Elsevier Ltd. All rights reserved.
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  • 2015鈥�16 ENSO contributed reduction in oil sardines along the Kerala coast, south鈥恮est India

    Shetye, Suhas S.   Kurian, Siby   Gauns, Mangesh   Vidya, Pottekkatt Jayapalan  

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  • Variability of organic nitrogen and its role in regulating phytoplankton in the eastern Arabian Sea

    Shetye, Suhas S.   Kurian, Siby   Naik, Hema   Gauns, Mangesh   Chndrasekhararao, A.V.   Kumar, Ashwini   Naik, Bhagyashri  

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  • Spatial variability of copepod species distribution in the eastern Arabian Sea in pre-monsoon conditions

    D'souza, Analiza Maria   Gauns, Mangesh  

    This work examines the spatial variability among mesozooplankton abundance and copepod species diversity along the continental margin prior to the onset of southwest monsoon in the eastern Arabian Sea during the year 2011. The eastern Arabian Sea experiences seasonal hypoxia during the receding phase of monsoon that corresponds to low copepod abundance in the slope region. Collectively, fifty copepod species were identified over the continental margin where the diversity index (H') ranged between 2.59 and 3.73. Bray-Curtis cluster analysis clustered the stations into three groups that corresponded to the continental shelf, slope and break reaches of the eastern Arabian Sea. This spatial variability among the groups is mainly ascribed to changes in the relative contributions of the prevailing species. The distinct genera of the continental shelf were Microsetella spp. and Temora turbinata; at the slope region, Oncaea spp. and at shelf-break, Pleuromamma indica. Overall, herbivorous copepods were numerically abundant at the continental shelf and carnivores at the slope. The discrepancy between the distributions of herbivorous versus carnivorous copepod assemblages may be attributed to environmental factors such as ambient water dissolved oxygen and phytoplankton biomass.
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  • Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal

    Fernandes, Veronica   Ramaiah, Nagappa   Paul, Jane T.   Sardessai, Sugandha   Babu, R. Jyoti   Gauns, Mangesh  

    With large influx of freshwater that decreases sea-surface salinities,weak wind forcing of < 10 m s(-1) and almost always warm (> 28 degrees C) sea-surface temperature that stratifies and shallows the mixed layer leading to low or no nutrient injections into the surface, primary production in Bay of Bengal is reportedly low. As a consequence, the Bay of Bengal is considered as a region of low biological productivity. Along with many biological parameters, bacterioplankton abundance and production were measured in the Bay of Bengal during post monsoon (September-October 2002) along an open ocean transect, in the central Bay (CB, 88 degrees E) and the other transect in the western Bay (WB). The latter representing the coastal influenced shelf/slope waters. Bacterioplankton abundances (< 2 x 10(9) cells l(-1)) were similar to those reported from the HNLC equatorial Pacific and the highly productive northern Arabian Sea. Yet, the thymidine uptake rates along CB (average of 1.46 pM h(-1)) and WB (average of 1.40 pM h(-1)) were less than those from the northwestern Indian Ocean. These abundances and uptake rates were higher than those in the oligotrophic northwestern Sargasso Sea (< 7 x 10(8) cells l(-1); av 1.0 pM h(-1)). Concentrations of chlorophyll a (chl a), primary production rates and total organic carbon (TOC) were also measured for a comparison of heterotrophic and autotrophic production. In the WB, bacterioplankton carbon biomass equaled similar to 95% of chl a carbon than just 31% in the CB. Average bacterial:primary production (BP:PP) ratios accounted for 29% in the CB and 31% in the WB. This is mainly due to lower primary productivity (PP) in the WB (281 mg C m(-2) d(-1)) than in the CB (306 mg C m(-2) day(-1)). This study indicates that bacteria-phytoplankton relationship differs in the open (CB) and coastal waters (WB). Higher abundance and contrastingly low bacterial production (BP) in WB may be because of the riverine bacteria, brought in through discharges, becoming dormant and unable to reproduce in salinities of 28 or more psu. Heterotrophic bacteria appear to utilize in situ DOC rather rapidly and their carbon demand is similar to 50% of daily primary production. It is also apparent that allochthonous organic matter, in particular in the western Bay, is important for meeting their carbon demand.
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  • Seasonal variations in abundance, biomass and grazing rates of microzooplankton in a tropical monsoonal estuary

    Gauns, Mangesh   Mochemadkar, Sunita   Patil, Shrikant   Pratihary, Anil   Naqvi, S. W. A.   Madhupratap, M.  

    Seasonal abundance, composition and grazing rates of microzooplankton (20–200 µm) in the Zuari estuary were investigated to evaluate their importance in food web dynamics of a tropical monsoonal estuary. Average abundances of microzooplankton (organisms × 104 l−1) during the three seasons were 0.44 (southwest monsoon), 1.13 (post-monsoon) and 0.96 (pre-monsoon). Protozoan (ciliates, heterotrophic dinoflagellates and sarcodines) accounted for most (96 %) of the microzooplankton community, with micrometazoan (nauplii and copepodid stages of copepods, fish eggs, etc.). being far less abundant. Among protozoans, ciliates (loricates and aloricates) were most numerous (69 % of the total microzooplankton). Statistically significant (p < 0.001) co-variations of microzooplankton with other biological parameters such as chlorophyll a and bacterial biomass were observed. Salinity influenced microzooplankton distribution, with an optimum range of 15–20. Microzooplankton formed a large organic carbon pool, accounting for 24–40 % of the total carbon in the living matter. Seasonally averaged microzooplankton biomasses were 22.3, 36.1 and 24.6 mmol C m−3, respectively, during the southwest monsoon, post-monsoon and pre-monsoon periods, and were largely supported by non-living particulate carbon (detritus) particularly during the non-monsoon seasons. Experimental studies revealed significant microzooplankton grazing on phytoplankton standing stock, mainly (>60 %) by the pico and nano fraction (<20 µm) for most of the year. Phytoplankton growth rates (day−1) ranged between 0.69 and 1.24. Microzooplankton grazing was estimated to consume 30–82 % of the phytoplankton standing stock, and 58–97 % of the daily primary production. Results of the present study highlight the role of the microzooplankton as an important consumer of phytoplankton production.
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  • Variation in phytoplankton community and its implication to dimethylsulphide production at a coastal station off Goa, India

    Naik, Bhagyashri R.   Gauns, Mangesh   Bepari, Kausar   Uskaikar, Hema   Shenoy, Damodar M.  

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  • Ecological diversity of planktonic protists in spatial regimes of the Arabian Sea revealed through next-generation sequencing

    Das, Priya Brata   Gauns, Mangesh   Naqvi, S.W.A.  

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  • The relationship between volatile halocarbons and phytoplankton pigments during a Trichodesmium bloom in the coastal eastern Arabian Sea

    Roy, Rajdeep   Pratihary, Anil   Narvenkar, Gayatree   Mochemadkar, Sunita   Gauns, Mangesh   Naqvi, S. W. A.  

    Eukaryotic phytoplankton such as diatoms and prymnesiophytes produce biogenic halocarbons in the ocean that serve as important sources of chlorine and bromine to the atmosphere, but the role of cyanobacteria in halocarbon production is not well established. We studied distributions of chloroform (CHCl(3)), carbon tetrachloride (CCl(4)), methylene bromide (CH(2)Br(2)) and bromoform (CHBr(3)) in relation to phytoplankton composition, determined from pigment analysis complemented by microscopic examination, for one month in coastal waters of the eastern Arabian that experienced a Trichodesmium bloom that typically occurs during the Spring Intermonsoon season. High concentrations of zeaxanthin (23 mu g l(-1)), alpha beta betacarotene (6 mu g l(-1)) and chlorophyll a (67 mu g l(-1)) were found within the bloom whereas the marker pigment concentrations were low outside the bloom. CHCl(3) and CCl(4) occurred in relatively high concentrations in surface waters whereas CH(2)Br(2) and CHBr(3) were restricted to the subsurface layer. Chlorinated halocarbons were positively inter-correlated and with CHBr(3). The observed spatial and temporal trends in brominated compounds appear to be related to the abundance of Trichodesmium although correlations between concentrations of brominated compounds with various marker pigments were poor and statistically non-significant. The results support the existence of multiple sources and sinks of halogenated compounds, which might obscure the relationship between halocarbons and phytoplankton composition. (C) 2011 Elsevier Ltd. All rights reserved.
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  • Seasonal variations and relationships between environmental parameters and heavy metal concentrations in tissues of Crassostrea species and in its ambience from the tropical estuaries

    Shenai-Tirodkar, Prachi   Gauns, Mangesh   Kumar, Girish   Ansari, Zakir  

    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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