Cold seeps are oases for biological communities on the sea floor around hydrocarbon emission pathways.Microbial utilization of methane and other hydrocarbons yield products that fuel rich chemosynthetic communities at...Cold seeps are oases for biological communities on the sea floor around hydrocarbon emission pathways.Microbial utilization of methane and other hydrocarbons yield products that fuel rich chemosynthetic communities at these sites.One such site in the cold seep ecosystem of Krishna-Godavari basin(K-G basin)along the east coast of India,discovered in Feb 2018 at a depth of 1800 m was assessed for its bacterial diversity.The seep bacterial communities were dominated by phylum Proteobacteria(57%),Firmicutes(16%)and unclassified species belonging to the family Helicobacteriaceae.The surface sediments of the seep had maximum OTUs(operational taxonomic units)(2.27×10^(3))with a Shannon alpha diversity index of 8.06.In general,environmental parameters like total organic carbon(p<0.01),sulfate(p<0.001),sulfide(p<0.05)and methane(p<0.01)were responsible for shaping the bacterial community of the cold seep ecosystem in the K-G Basin.Environmental parameters play a significant role in changing the bacterial diversity richness between different cold seep environments in the oceans.展开更多
Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect be...Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect benthicforaminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment wasconducted on Cymbaloporetta plana to understand the coupled effect of temperature(25°C, 27°C, 30°C) and food(102±5,203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimenssubjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimensfed with 508±23 cells reproduced, 0 irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggeststhat it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food,died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproductionwith decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow waterbenthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect thegrowth and abundance of shallow water benthic foraminifera.展开更多
The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, ...The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.展开更多
Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying mor...Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying morphologies. ＇Mesh rim＇, ＇window＇, ＇hourglass＇ and ＇bastite＇ are the most common textures displayed by both chrysotile and lizardite. Numerous chrysotile veins in association with cross cutting magnetite veins indicate an advanced stage of serpentinisation. The relatively high abundance of chrysotile and lizardite suggest their close association and formation at a temperature below 250℃. Abundant ＇mesh rim＇ and ＇bastite＇ texture and variegated matrix reveal that the present serpentinites might have formed due to the interaction of harzburgite and seawater. Positive Eu anomaly （Eu/Eu^＊ up to ＋3.38）, higher La/Sm （up to 4.40） and Nb/La （up to 6.34） ratios suggest substantial hydrothermal influence during the formation of the serpentinites.展开更多
Knowledge of sea surface temperature(SST)behaviour is vital for long-term climate scenarios.This study highlights essential outcomes about the distinguishable and unsurprising warming of the SST along the southern bor...Knowledge of sea surface temperature(SST)behaviour is vital for long-term climate scenarios.This study highlights essential outcomes about the distinguishable and unsurprising warming of the SST along the southern border of the Levantine Basin.The analysis is based on monthly SST data for the period 1948-2018.The southern Levantine Basin has undergone SST increase,during the last 71 years.In this study,a consistent warming trend has been found for the analysed SST data series,with a rate of 0.04℃/a,i.e.,0.4℃/(10 a).From 1975 to 1991 the mean annual SST was 17.1℃,and this increased to be 19.2℃,over the period 2002-2018.Results revealed two opposite trends of variability:a decreasing trend(−0.06℃/a)over the period 1975-1991,and an increasing trend(0.2℃/a)from 2002 to 2018.Over the period 1948-2018,positive mean annual SST anomalies had an average of 1.8℃,and negative anomalies had an average of−1.1℃.The lowest SST total increase was found from January to April,with values about 0.03℃,while the highest warming appeared from June to September.The driving mechanisms behind the SST changes need to be more investigated,to understand the future trends and impacts of climate change in the Levantine Basin.展开更多
The El Nino-Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Paci- fic Ocean-atmosphere interactions. The oscillatory nature of ENSO requires both positive and negative ocean-atmospher...The El Nino-Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Paci- fic Ocean-atmosphere interactions. The oscillatory nature of ENSO requires both positive and negative ocean-atmosphere feedbacks. The positive feedback is dated back to Bjerknes' hypothesis in the 1960s, and different negative feedbacks have been proposed since the 1980s associated with the delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator. The de- layed oscillator assumes that wave reflection at the western boundary provides a negative feedback for the coupled system to oscillate. The western Pacific oscillator emphasizes equatorial wind in the western Pacific that provides a negative feedback for the coupled system. The recharge-discharge oscillator argues that discharge and recharge of equatorial heat content cause the coupled system to oscillate. The advective-re- flective oscillator emphasizes the importance of zonal advection associated with wave reflection at both the western and eastern boundaries. All of these physics are summarized in a unificd ENSO oscillator. The de- layed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflec- tive oscillator can be extracted as special cases of the unified oscillator. As suggested by this unified oscillator, all of the previnus ENSO oscillator mechanisms may be operating in nature.展开更多
Oxidative stress and antioxidant defence systems were assessed in a marine brown alga Padina tetrastromatica, commonly occurring from the tropics. Lipid peroxidation （LPX） and H2O2 were measured as oxidative stress ...Oxidative stress and antioxidant defence systems were assessed in a marine brown alga Padina tetrastromatica, commonly occurring from the tropics. Lipid peroxidation （LPX） and H2O2 were measured as oxidative stress markers, and antioxidant defences were measured as catalase （CAT）, glutathione S-transferase （GST） and ascorbic acid （ASA）, in order to understand their dissimilarity with respect to pollution levels from selective locations along the central west coast of India. A significant increased levels of LPX, H2O2, CAT and GST were observed in samples from relatively polluted localities （Colaba and Karwar） when compared to less polluted locality （Anjuna）, while AsA concentration was higher in algal samples from worst polluted region of Colaba. Heavy metals such as Cd and Pb were also higher in the vicinity of polluted areas compared to reference area. Variation of oxidative stress indices in response to accumulation of heavy metals within P. tetrastromatica could be used as molecular biomarkers in assessment and monitoring environmental quality of ecologically sensitive marine habitats.展开更多
The 5°S-10°S band in the Indian Ocean,named recently as Seychelles-Chagos Thermocline Ridge (SCTR),is a region where several phenomena of significant climatic influence build up.It is a generation region for...The 5°S-10°S band in the Indian Ocean,named recently as Seychelles-Chagos Thermocline Ridge (SCTR),is a region where several phenomena of significant climatic influence build up.It is a generation region for tropical cyclones striking the inhabited islands in the Indian Ocean and the African coast.It was recently shown that it is one of the regions where atmospheric intraseasonal variability (e.g.Madden Julian Oscillation,MJO) is展开更多
Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typica...Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.展开更多
Colletotrichum gloeosporioides sensu lato has been associated with anthracnose in diverse commercial crops.It is now established that C.gloeosporioides sensu lato comprises 33 phylogenetic species and C.gloeosporioide...Colletotrichum gloeosporioides sensu lato has been associated with anthracnose in diverse commercial crops.It is now established that C.gloeosporioides sensu lato comprises 33 phylogenetic species and C.gloeosporioides sensu stricto is not a common pathogen of tropical fruits.In this study,we investigated the phylogenetic relationships of 85 Colletotrichum isolates associated with select tropical fruits and flowering plants from India.In the ApMat marker analysis,the 85 isolates clustered with 7 known Colletotrichum species(C.aotearoa,C.dianesei,C.endomangiferae,C.musae,C.siamense,C.theobromicola,Glomerella cingulata f.sp.camelliae)and six novel lineages.One of the novel lineages is described and illustrated in this paper as Colletotrichum communis sp.nov.,while new-host pathogen associations for C.aotearoa,C.endomangiferae,C.dianesei and C.theobromicola are reported from India.Out of the 85 isolates analysed in this paper,73 isolates clustered within the C.siamense species complex,indicating that C.siamense species complex,not C.gloeosporioides sensu stricto,is common on tropical fruits.In comparison with act,cal,gapdh,ITS and tub2 gene markers,we recommend the use of the ApMat marker for accurate identification of cryptic species within the C.siamense species complex.We believe that the ApMat marker,in combination with one or two similar‘phylogenetically superior’gene markers,is a better candidate for specieslevel classification of fungi that were traditionally identified as‘Colletotrichum gloeosporioides’.展开更多
Sordariomycetes is one of the largest classes of Ascomycota and is characterised by perithecial ascomata and inoperculate unitunicate asci.The class includes many important plant pathogens,as well as endophytes,saprob...Sordariomycetes is one of the largest classes of Ascomycota and is characterised by perithecial ascomata and inoperculate unitunicate asci.The class includes many important plant pathogens,as well as endophytes,saprobes,epiphytes,and fungicolous,lichenized or lichenicolous taxa.The class includes freshwater,marine and terrestrial taxa and has a worldwide distribution.This paper provides an updated outline of the Sordariomycetes and a backbone tree incorporating asexual and sexual genera in the class.Based on phylogeny and morphology we introduced three subclasses;Diaporthomycetidae,Lulworthiomycetidae and Meliolomycetidae and five orders;Amplistromatales,Annulatascales,Falcocladiales,Jobellisiales and Togniniales.The outline is based on literature to the end of 2014 and the backbone tree published in this paper.Notes for 397 taxa with information,such as new family and genera novelties,novel molecular data published since the Outline of Ascomycota 2009,and new links between sexual and asexual genera and thus synonymies,are provided.The Sordariomycetes now comprises six subclasses,28 orders,90 families and 1344 genera.In addition a list of 829 genera with uncertain placement in Sordariomycetesis also provided.展开更多
Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation patte...Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation pattern.Thus,the long term quantification of changes in aerosol and cloud characteristics and their interactions on both temporal as well as spatial scale will provide a crucial information for the better assessment of future climate change.In present study,18 years(2003-2020)MODerate Resolution Imaging Spectro-radiometer(MODIS)derived aerosol-cloud dataset over the Northern Indian Ocean(NIO)were analysed to assess climatology and trend of aerosol,cloud characteristics and their correlation.We found a strong heterogeneity in spatio-temporal variation of aerosol and cloud parameters over the NIO that are more prominent for the coastal region.The climatological mean of aerosol loading is found high(AOD≥0.5)over the outflow region along the Indian sub-continent and low(AOD≤0.2)over the northern equatorial open ocean.The climatological mean of cloud properties shows dominance of optically thicker deep convective(CTP<600 hPa and CTT<260 K)clouds over the southern Bay of Bengal(BoB)and thinner shallow(CTP>700 hPa and CTT>273 K)over the northwestern Arabian Sea(AS).Similarly,bigger effective radii(>17µm)observed along the equatorial open ocean whereas smaller CER(<17µm)were found over Indian sub-continental coastline and western AS.Further,trend analysis reveals an increasing pattern in AOD(0.002 yr^(-1)),CER(0.051µm yr^(-1)),LWP(0.033 gm^(-2) yr^(-1))and CF(0.002 yr^(-1))while COD,CTT and CTP show negative trend in order of-0.005 yr^(-1),-0.094 K yr^(-1) and-1.160 hPa yr^(-1),respectively.We also perform similar analysis for seven sub-region of interest(R1 to R7)across the NIO and results show a decreasing pattern in AOD(-0.001 yr^(-1))at R4 against maximum mean AOD(0.44±0.03).However,coastal sub-regions R1 and R5 illustrate maximum increase in aerosol loading(>0.003 yr^(-1))suggesting a significant impact of sub-continental outflow over the regions.The spatial correlation of cloud properties with respect to AOD shows a positive slope for CER(0.14)and CF(0.48)and a negative for COD(-0.19),LWP(-0.18),CTT(-0.37),CTP(-0.41).The present study provides in-depth information about the aerosol-cloud characteristics for a long term scale over NIO and could be useful in regional aerosol-cloud interaction induced climate forcing estimation.展开更多
In response to the Deepwater Horizon （DwH） oil spill event in 2010, the Naval Oceanographic Office deployed a nowcast-forecast system covering the Gulf of Mexico and adjacent Caribbean Sea that was designated Americ...In response to the Deepwater Horizon （DwH） oil spill event in 2010, the Naval Oceanographic Office deployed a nowcast-forecast system covering the Gulf of Mexico and adjacent Caribbean Sea that was designated Americas Seas, or AMSEAS, which is documented in this manuscript. The DwH disaster provided a challenge to the application of available ocean-forecast capabilities, and also generated a historically large observational dataset. AMSEAS was evaluated by four complementary efforts, each with somewhat different aims and approaches： a university research consortium within an Integrated Ocean Observing System （IOOS） testbed; a petroleum industry consortium, the Gulf of Mexico 3-D Operational Ocean Forecast System Pilot Prediction Project （GOMEX-PPP）; a British Petroleum （BP） funded project at the Northern Gulf Institute in response to the oil spill; and the Navy itself. Validation metrics are presented in these different projects for water temperature and salinity profiles, sea surface wind, sea surface temperature, sea surface height, and volume transport, for different forecast time scales. The validation found certain geographic and time biases/errors, and small but systematic improvements relative to earlier regional and global modeling efforts. On the basis of these positive AMSEAS validation studies, an oil spill transport simulation was conducted using archived AMSEAS nowcasts to examine transport into the estuaries east of the Mississippi River. This effort captured the influences of Hurricane Alex and a non-tropical cyclone off the Louisiana coast, both of which pushed oil into the western Mississippi Sound, illustrating the importance of the atmospheric influence on oil spills such as DwH.展开更多
Tropical cyclones are intense and frequent natural hazards in the Bay of Bengal(BoB),leading to substantial losses of life and property along coastal areas.Understanding the seasonal variations and environmental facto...Tropical cyclones are intense and frequent natural hazards in the Bay of Bengal(BoB),leading to substantial losses of life and property along coastal areas.Understanding the seasonal variations and environmental factors that influence cyclone behavior in this region is essential for effective disaster preparedness and mitigation.This study conducts a comparative analysis of pre-monsoon and post-monsoon tropical cyclones of identical categories on upper oceanic parameters,including sea surface temperature(SST),sea surface salinity(SSS),sea level pressure(SLP),mixed layer depth(MLD),chlorophyll-a,and Ekman transport in the BoB.SSTs exhibit seasonal variation during cyclonic events,with pre-monsoon temperatures ranging from 29 to 31℃,compared to post-monsoon of 28 to 29℃.展开更多
文摘Cold seeps are oases for biological communities on the sea floor around hydrocarbon emission pathways.Microbial utilization of methane and other hydrocarbons yield products that fuel rich chemosynthetic communities at these sites.One such site in the cold seep ecosystem of Krishna-Godavari basin(K-G basin)along the east coast of India,discovered in Feb 2018 at a depth of 1800 m was assessed for its bacterial diversity.The seep bacterial communities were dominated by phylum Proteobacteria(57%),Firmicutes(16%)and unclassified species belonging to the family Helicobacteriaceae.The surface sediments of the seep had maximum OTUs(operational taxonomic units)(2.27×10^(3))with a Shannon alpha diversity index of 8.06.In general,environmental parameters like total organic carbon(p<0.01),sulfate(p<0.001),sulfide(p<0.05)and methane(p<0.01)were responsible for shaping the bacterial community of the cold seep ecosystem in the K-G Basin.Environmental parameters play a significant role in changing the bacterial diversity richness between different cold seep environments in the oceans.
基金the Department of Science and Technology,New Delhi,for the financial support to RS under the National Network Programme on Climate Change and Coastal Vulnerability(DST/CCP/NCC&CV/130/2017(G))SRK under the Women Scientist Scheme [SR/WOS-A/LS-145/2016(G)],This is a NIO contribution number 9341
文摘Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect benthicforaminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment wasconducted on Cymbaloporetta plana to understand the coupled effect of temperature(25°C, 27°C, 30°C) and food(102±5,203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimenssubjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimensfed with 508±23 cells reproduced, 0 irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggeststhat it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food,died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproductionwith decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow waterbenthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect thegrowth and abundance of shallow water benthic foraminifera.
基金supported by the Department of Science and Technology through a FASTRACK project to RSthe Council of Scientific and Industrial Research,India by funding GEOSINKS project
文摘The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.
基金funded by ONR grant No.0014-97-1-0925CSIR Network Programme(COR 0006)on Indian Ocean ridges
文摘Serpentinites from the inside corner high （6°38.5′S/68°19.34′E） from the Northern Central Indian Ridge （NCIR） are comprised mainly of high Mg-rich lizardite and chrysotile pseudomorphs with varying morphologies. ＇Mesh rim＇, ＇window＇, ＇hourglass＇ and ＇bastite＇ are the most common textures displayed by both chrysotile and lizardite. Numerous chrysotile veins in association with cross cutting magnetite veins indicate an advanced stage of serpentinisation. The relatively high abundance of chrysotile and lizardite suggest their close association and formation at a temperature below 250℃. Abundant ＇mesh rim＇ and ＇bastite＇ texture and variegated matrix reveal that the present serpentinites might have formed due to the interaction of harzburgite and seawater. Positive Eu anomaly （Eu/Eu^＊ up to ＋3.38）, higher La/Sm （up to 4.40） and Nb/La （up to 6.34） ratios suggest substantial hydrothermal influence during the formation of the serpentinites.
文摘Knowledge of sea surface temperature(SST)behaviour is vital for long-term climate scenarios.This study highlights essential outcomes about the distinguishable and unsurprising warming of the SST along the southern border of the Levantine Basin.The analysis is based on monthly SST data for the period 1948-2018.The southern Levantine Basin has undergone SST increase,during the last 71 years.In this study,a consistent warming trend has been found for the analysed SST data series,with a rate of 0.04℃/a,i.e.,0.4℃/(10 a).From 1975 to 1991 the mean annual SST was 17.1℃,and this increased to be 19.2℃,over the period 2002-2018.Results revealed two opposite trends of variability:a decreasing trend(−0.06℃/a)over the period 1975-1991,and an increasing trend(0.2℃/a)from 2002 to 2018.Over the period 1948-2018,positive mean annual SST anomalies had an average of 1.8℃,and negative anomalies had an average of−1.1℃.The lowest SST total increase was found from January to April,with values about 0.03℃,while the highest warming appeared from June to September.The driving mechanisms behind the SST changes need to be more investigated,to understand the future trends and impacts of climate change in the Levantine Basin.
基金supported by the National Oceanic and Atmospheric Administration(NOAA)Office of Global Programs(CLIVAR-Pacific Program)by the base funding of NOAA Atlantic Oceanographic and Meteorologi cal Laboratory.
文摘The El Nino-Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Paci- fic Ocean-atmosphere interactions. The oscillatory nature of ENSO requires both positive and negative ocean-atmosphere feedbacks. The positive feedback is dated back to Bjerknes' hypothesis in the 1960s, and different negative feedbacks have been proposed since the 1980s associated with the delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator. The de- layed oscillator assumes that wave reflection at the western boundary provides a negative feedback for the coupled system to oscillate. The western Pacific oscillator emphasizes equatorial wind in the western Pacific that provides a negative feedback for the coupled system. The recharge-discharge oscillator argues that discharge and recharge of equatorial heat content cause the coupled system to oscillate. The advective-re- flective oscillator emphasizes the importance of zonal advection associated with wave reflection at both the western and eastern boundaries. All of these physics are summarized in a unificd ENSO oscillator. The de- layed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflec- tive oscillator can be extracted as special cases of the unified oscillator. As suggested by this unified oscillator, all of the previnus ENSO oscillator mechanisms may be operating in nature.
基金carried under the funds from CSIR,Network Project 0018
文摘Oxidative stress and antioxidant defence systems were assessed in a marine brown alga Padina tetrastromatica, commonly occurring from the tropics. Lipid peroxidation （LPX） and H2O2 were measured as oxidative stress markers, and antioxidant defences were measured as catalase （CAT）, glutathione S-transferase （GST） and ascorbic acid （ASA）, in order to understand their dissimilarity with respect to pollution levels from selective locations along the central west coast of India. A significant increased levels of LPX, H2O2, CAT and GST were observed in samples from relatively polluted localities （Colaba and Karwar） when compared to less polluted locality （Anjuna）, while AsA concentration was higher in algal samples from worst polluted region of Colaba. Heavy metals such as Cd and Pb were also higher in the vicinity of polluted areas compared to reference area. Variation of oxidative stress indices in response to accumulation of heavy metals within P. tetrastromatica could be used as molecular biomarkers in assessment and monitoring environmental quality of ecologically sensitive marine habitats.
文摘The 5°S-10°S band in the Indian Ocean,named recently as Seychelles-Chagos Thermocline Ridge (SCTR),is a region where several phenomena of significant climatic influence build up.It is a generation region for tropical cyclones striking the inhabited islands in the Indian Ocean and the African coast.It was recently shown that it is one of the regions where atmospheric intraseasonal variability (e.g.Madden Julian Oscillation,MJO) is
文摘Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.
基金The authors would like to thank CSIR-Institute of Microbial Technology,Chandigarh for the financial support,Dr.D.Ananthapadmanaban for his help in the microscopy and Mr.Deepak Bhatt for DNA sequencing assistance.Drs.Kevin D.Hyde,Lei Cai and Bevan Weir are thanked for the inspiration and useful discussions on Colletotrichum taxonomy.This work was supported by IMTECHOLP0071 project and CSIR-SRF fellowship awarded to GS.This is NIO contribution no.7636 and IMTECH communication no.IMT2014/21.
文摘Colletotrichum gloeosporioides sensu lato has been associated with anthracnose in diverse commercial crops.It is now established that C.gloeosporioides sensu lato comprises 33 phylogenetic species and C.gloeosporioides sensu stricto is not a common pathogen of tropical fruits.In this study,we investigated the phylogenetic relationships of 85 Colletotrichum isolates associated with select tropical fruits and flowering plants from India.In the ApMat marker analysis,the 85 isolates clustered with 7 known Colletotrichum species(C.aotearoa,C.dianesei,C.endomangiferae,C.musae,C.siamense,C.theobromicola,Glomerella cingulata f.sp.camelliae)and six novel lineages.One of the novel lineages is described and illustrated in this paper as Colletotrichum communis sp.nov.,while new-host pathogen associations for C.aotearoa,C.endomangiferae,C.dianesei and C.theobromicola are reported from India.Out of the 85 isolates analysed in this paper,73 isolates clustered within the C.siamense species complex,indicating that C.siamense species complex,not C.gloeosporioides sensu stricto,is common on tropical fruits.In comparison with act,cal,gapdh,ITS and tub2 gene markers,we recommend the use of the ApMat marker for accurate identification of cryptic species within the C.siamense species complex.We believe that the ApMat marker,in combination with one or two similar‘phylogenetically superior’gene markers,is a better candidate for specieslevel classification of fungi that were traditionally identified as‘Colletotrichum gloeosporioides’.
基金This research was supported by Featured microbial resources and diversity investigation in Southwest Karst area(2014FY120100).The authors extend their sincere appreciations to the Deanship of Scientific Research at King Saud University for its funding this Prolific Research Group(PRG-1436-09).Kevin D.Hyde thanks the Chinese Academy of Sciences,project number 2013T2S0030,for the award of Visiting Professorship for Senior International Scientists at Kunming Institute of Botany.B.D.Shenoy acknowledges the funding to visit Mae Fah Luang University,Chiang Rai under Indo-Thailand Bilateral Programme(THAI-1205).Y.P.Xiao and T.C.Wen are grateful to The National Natural Science Foundation of China(No.31460012&No.31200016).Shi-Ke Huang and J.C.Kang are grateful to the Agricultural Science and Technology Foundation of Guizhou Province(Nos.NY[2013]3042),the International Collaboration Plan of Guizhou Province(No.G[2012]7006)and the Innovation Team Construction for Science And Technology of Guizhou Province(No.[2012]4007)from the Science and Technology Department of Guizhou Province,China.
文摘Sordariomycetes is one of the largest classes of Ascomycota and is characterised by perithecial ascomata and inoperculate unitunicate asci.The class includes many important plant pathogens,as well as endophytes,saprobes,epiphytes,and fungicolous,lichenized or lichenicolous taxa.The class includes freshwater,marine and terrestrial taxa and has a worldwide distribution.This paper provides an updated outline of the Sordariomycetes and a backbone tree incorporating asexual and sexual genera in the class.Based on phylogeny and morphology we introduced three subclasses;Diaporthomycetidae,Lulworthiomycetidae and Meliolomycetidae and five orders;Amplistromatales,Annulatascales,Falcocladiales,Jobellisiales and Togniniales.The outline is based on literature to the end of 2014 and the backbone tree published in this paper.Notes for 397 taxa with information,such as new family and genera novelties,novel molecular data published since the Outline of Ascomycota 2009,and new links between sexual and asexual genera and thus synonymies,are provided.The Sordariomycetes now comprises six subclasses,28 orders,90 families and 1344 genera.In addition a list of 829 genera with uncertain placement in Sordariomycetesis also provided.
文摘Aerosols are one of the important atmospheric constituents and exert indirect impact on climate through the modification of microphysical and radiative properties of clouds that in turn perturb the precipitation pattern.Thus,the long term quantification of changes in aerosol and cloud characteristics and their interactions on both temporal as well as spatial scale will provide a crucial information for the better assessment of future climate change.In present study,18 years(2003-2020)MODerate Resolution Imaging Spectro-radiometer(MODIS)derived aerosol-cloud dataset over the Northern Indian Ocean(NIO)were analysed to assess climatology and trend of aerosol,cloud characteristics and their correlation.We found a strong heterogeneity in spatio-temporal variation of aerosol and cloud parameters over the NIO that are more prominent for the coastal region.The climatological mean of aerosol loading is found high(AOD≥0.5)over the outflow region along the Indian sub-continent and low(AOD≤0.2)over the northern equatorial open ocean.The climatological mean of cloud properties shows dominance of optically thicker deep convective(CTP<600 hPa and CTT<260 K)clouds over the southern Bay of Bengal(BoB)and thinner shallow(CTP>700 hPa and CTT>273 K)over the northwestern Arabian Sea(AS).Similarly,bigger effective radii(>17µm)observed along the equatorial open ocean whereas smaller CER(<17µm)were found over Indian sub-continental coastline and western AS.Further,trend analysis reveals an increasing pattern in AOD(0.002 yr^(-1)),CER(0.051µm yr^(-1)),LWP(0.033 gm^(-2) yr^(-1))and CF(0.002 yr^(-1))while COD,CTT and CTP show negative trend in order of-0.005 yr^(-1),-0.094 K yr^(-1) and-1.160 hPa yr^(-1),respectively.We also perform similar analysis for seven sub-region of interest(R1 to R7)across the NIO and results show a decreasing pattern in AOD(-0.001 yr^(-1))at R4 against maximum mean AOD(0.44±0.03).However,coastal sub-regions R1 and R5 illustrate maximum increase in aerosol loading(>0.003 yr^(-1))suggesting a significant impact of sub-continental outflow over the regions.The spatial correlation of cloud properties with respect to AOD shows a positive slope for CER(0.14)and CF(0.48)and a negative for COD(-0.19),LWP(-0.18),CTT(-0.37),CTP(-0.41).The present study provides in-depth information about the aerosol-cloud characteristics for a long term scale over NIO and could be useful in regional aerosol-cloud interaction induced climate forcing estimation.
文摘In response to the Deepwater Horizon （DwH） oil spill event in 2010, the Naval Oceanographic Office deployed a nowcast-forecast system covering the Gulf of Mexico and adjacent Caribbean Sea that was designated Americas Seas, or AMSEAS, which is documented in this manuscript. The DwH disaster provided a challenge to the application of available ocean-forecast capabilities, and also generated a historically large observational dataset. AMSEAS was evaluated by four complementary efforts, each with somewhat different aims and approaches： a university research consortium within an Integrated Ocean Observing System （IOOS） testbed; a petroleum industry consortium, the Gulf of Mexico 3-D Operational Ocean Forecast System Pilot Prediction Project （GOMEX-PPP）; a British Petroleum （BP） funded project at the Northern Gulf Institute in response to the oil spill; and the Navy itself. Validation metrics are presented in these different projects for water temperature and salinity profiles, sea surface wind, sea surface temperature, sea surface height, and volume transport, for different forecast time scales. The validation found certain geographic and time biases/errors, and small but systematic improvements relative to earlier regional and global modeling efforts. On the basis of these positive AMSEAS validation studies, an oil spill transport simulation was conducted using archived AMSEAS nowcasts to examine transport into the estuaries east of the Mississippi River. This effort captured the influences of Hurricane Alex and a non-tropical cyclone off the Louisiana coast, both of which pushed oil into the western Mississippi Sound, illustrating the importance of the atmospheric influence on oil spills such as DwH.
文摘Tropical cyclones are intense and frequent natural hazards in the Bay of Bengal(BoB),leading to substantial losses of life and property along coastal areas.Understanding the seasonal variations and environmental factors that influence cyclone behavior in this region is essential for effective disaster preparedness and mitigation.This study conducts a comparative analysis of pre-monsoon and post-monsoon tropical cyclones of identical categories on upper oceanic parameters,including sea surface temperature(SST),sea surface salinity(SSS),sea level pressure(SLP),mixed layer depth(MLD),chlorophyll-a,and Ekman transport in the BoB.SSTs exhibit seasonal variation during cyclonic events,with pre-monsoon temperatures ranging from 29 to 31℃,compared to post-monsoon of 28 to 29℃.
