Mauritius Oceanography Institute

Victoria, Mauritius

Mauritius Oceanography Institute

Victoria, Mauritius
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Munoz J.,CNRS Natural Product Chemistry Institute | Moriou C.,CNRS Natural Product Chemistry Institute | Gallard J.-F.,CNRS Natural Product Chemistry Institute | Marie P.D.,Mauritius Oceanography Institute | Al-Mourabit A.,CNRS Natural Product Chemistry Institute
Tetrahedron Letters | Year: 2012

Two novel dimeric pyrrole-aminoimidazole (PAI) alkaloids (-) donnazoles A-B (1-2) were isolated from the marine sponge Axinella donnani collected off the Mauritius Island. Their structures were elucidated mainly by 2D NMR. Both compounds bear the crucial substituted cyclopentane of 'pre-axinellamine', the hypothetical common intermediate of all dimeric PAIs. Additionally, the essential trans-6,7 ring junction of palau′amine's congeners is already established in 1 and 2. The absolute configurations of 1 and 2 were deduced via NOE correlations in combination with the comparison of their circular dichroism data with the one of (-) sceptrin. The absolute configuration of (-) donnazoles A (1) and B (2) is coherent with the absolute configuration of the known dimeric members of PAI alkaloids. © 2012 Elsevier Ltd. All rights reserved.

Beedessee G.,Mauritius Oceanography Institute | Ramanjooloo A.,Mauritius Oceanography Institute | Aubert G.,CNRS Natural Product Chemistry Institute | Eloy L.,CNRS Natural Product Chemistry Institute | And 4 more authors.
Environmental Toxicology and Pharmacology | Year: 2012

The ocean is an exceptional source of natural products with many of them exhibiting novel structural features and bioactivity. As one of the most interesting phylum with respect to pharmacological active marine compounds, Poriferas have been investigated widely in the last few decades. A total of 60 organic extracts (hexane, ethyl acetate and butanol) from 20 species of marine sponges from Mauritius were screened at 50μg/ml in an in vitro screening assay against 9 human cancer cell lines. From these tested extracts, many exhibited pronounced cytotoxic effect at least in one of the cell lines and cell type cytotoxic specificity was observed. 27% of ethyl acetate, 11% of hexane and 2% of butanol extracts were found to possess a cytotoxicity ≥75% on 9 different cancer cell lines with the sponges Petrosia sp. 1, Petrosia sp. 2, Pericharax heteroraphis and Jaspis sp. being the most active. Overall, the HL-60 cellsweremuch more sensitive to most of the extracts than the other cell lines. We further evaluated the properties of the ethyl acetate (JDE) and hexane extract (JDH) of one sponge, Jaspis sp. on KB cells. JDE displayed a smaller IC50 than JDH. Clonogenic assay confirmed the antiproliferative effect of both extracts while mitochondrialmembrane potential change and microscopic analysis demonstrated extracts-induced apoptosis. Treatment with 100 ng/ml of JDE led to a significant increase of cells (24 h: 4.02%; 48 h: 26.23%) in sub-G1 phase. The cytotoxic properties of the tested extracts from these sponges suggest the presence of compounds with pharmacological potential and are currently undergoing fractionation to isolate the active constituents. © 2012 Elsevier B.V.

Rawat A.,Ifremer Laboratoire dOceanographie Spatiale | Rawat A.,Mauritius Oceanography Institute | Ardhuin F.,Ifremer Laboratoire dOceanographie Spatiale | Ardhuin F.,CNRS Physics Laboratory | And 5 more authors.
Geophysical Research Letters | Year: 2014

Ocean infragravity (IG) waves are low-frequency waves generated along shorelines by incident seas and swell and with heights of the order of 1 cm in the open ocean. Despite these small amplitudes, they can be of much importance for ice shelf break up and errors in measurements of sea level by future satellite altimeters. A combination of numerical model results and in situ data is used to show that bottom pressure signals in the infragravity frequency band can be dominated by bursts of energy that travel across ocean basins, and can last for several days. Two particularly strong events recorded in 2008 are studied, one in the North-Pacific and the other in the North-Atlantic. It is shown that infragravity waves can travel across whole oceans basins with the signal recorded on the western shores often dominated by IG waves coming from the opposite shore of that same ocean basin. © 2014. American Geophysical Union. All Rights Reserved.

Yahagi T.,University of Tokyo | Watanabe H.,Japan Agency for Marine - Earth Science and Technology | Kojima S.,University of Tokyo | Beedessee G.,Mauritius Oceanography Institute | Komai T.,Natural History Museum and Institute
Zootaxa | Year: 2014

A new species of the alvinocaridid shrimp genus Alvinocaris Williams & Chace, 1982 is described from the Solitaire hydrothermal vent field at 2606 m depth on the Central Indian Ridge. Alvinocaris solitaire sp. nov., the first species of the genus to be recorded from the Indian Ocean, is morphologically most similar to A. lusca Williams & Chace, 1982 from the Galapagos Rift, East Pacific Rise. The new species is distinguished from A. lusca by the less produced pterygostomial angle of the carapace, the presence of small teeth on the posterolateral margin of the third pleuron, and the lack of short plumose setae on the posteromedian margin of the telson. The genetic divergence of the mitochondrial cytochrome c oxidase subunit I (COI) gene (600 bp) among the nine Alvinocaris species analyzed clearly indicates that the new taxon is distinct from the congeneric species for which genetic data are available. Copyright © 2014 Magnolia Press.

Mangipudi V.R.,National Institute of Oceanography of India | Mangipudi V.R.,Mauritius Oceanography Institute | Goli A.,National Institute of Oceanography of India | Desa M.,National Institute of Oceanography of India | And 2 more authors.
Marine and Petroleum Geology | Year: 2014

Proven hydrocarbon occurrence in the Krishna Godavari (KG) basin, a part of the Eastern Continental Margin of India initiated intense exploration activities to discern the potential hydrocarbon bearing structures/payoff zones. Recent discovery of gas hydrates in its offshore triggered detailed exploration measures adopting advanced seismic data acquisition techniques supported by deep drilling to understand its genesis. Interpretation of Multichannel Seismic (MCS) sections highlighted several distinct horizons from Lower Cretaceous to Recent in the sediment overburden, and the nature and configuration of the underlying crust. The sections also depicted the presence of growth faults, shale bulging, toe thrust faulting, delta progradation, active sliding/slumping, buried channels, pinchout structures and reflection free zones, indicating the different types of sedimentary processes, varied geological environments and neotectonic activity in the KG offshore. High resolution sparker (HRS) data revealed subsidence, gas/fluid expulsion pathways, occasional diapiric intrusions and growth faulting in the upper slope, and toe thrust faulting, upthrust and diapiric intrusions in the lower slope. The mid slope is characteried by a well stratified E-W trending basin bounded by upthrust and diapirism. The entire region is associated with gas escape features (blanking zones, columnar type gas vents, fault controlled mud/shale diapirs, large dimension gas saturated zones and pockmarks). The growth faults, shale bulging and toe thrusting seen in the MCS data since Oligocene time could be linked to shale diapirism, upthrust, gas/fluid expulsion, subsidence and mini-basin formation observed on the shallow HRS records. Synthesis of these datasets suggests that the distribution of gas hydrate in the shallow sediments may be controlled by the deeper structural and tectonic configuration. Therefore, knowledge about shallow sedimentary column and its connectivity with deeper strata through faults/fractures and other structural features, and the geological architecture are significantly important to evaluate the genesis of gas hydrates. © 2014 Elsevier Ltd.

Titov V.V.,National Oceanic and Atmospheric Administration | Moore C.W.,University of Washington | Greenslade D.J.M.,Center for Australian Weather and Climate Research | Pattiaratchi C.,University of Western Australia | And 4 more authors.
Pure and Applied Geophysics | Year: 2011

Almost 5 years after the 26 December 2004 Indian Ocean tragedy, the 10 August 2009 Andaman tsunami demonstrated that accurate forecasting is possible using the tsunami community modeling tool Community Model Interface for Tsunamis (ComMIT). ComMIT is designed for ease of use, and allows dissemination of results to the community while addressing concerns associated with proprietary issues of bathymetry and topography. It uses initial conditions from a precomputed propagation database, has an easy-to-interpret graphical interface, and requires only portable hardware. ComMIT was initially developed for Indian Ocean countries with support from the United Nations Educational, Scientific, and Cultural Organization (UNESCO), the United States Agency for International Development (USAID), and the National Oceanic and Atmospheric Administration (NOAA). To date, more than 60 scientists from 17 countries in the Indian Ocean have been trained and are using it in operational inundation mapping. © 2011 Springer Basel AG (outside the USA).

Ardhuin F.,French Research Institute for Exploitation of the Sea | Rawat A.,French Research Institute for Exploitation of the Sea | Rawat A.,Mauritius Oceanography Institute | Aucan J.,Institut Universitaire de France
Ocean Modelling | Year: 2014

The spectral wave model WAVEWATCH III is extended from the windsea and swell band to lower frequencies, in order to represent free waves in the infragravity (IG) wave band. This extension is based on an empirical source of IG energy, which is defined along shorelines from the significant wave height and a mean period. The empirical proportionality factor is found to reproduce accurately the variations of free IG wave energy in coastal areas, where it was calibrated, and also has a good skill at global scales. In the open ocean, the model is particularly verified for frequencies in the range 5 to 14. mHz for which ocean bottom records are sensitive to the IG signal. The model captures between 30% and 80% of the variance in IG wave heights, depending on location, and reproduces the mean IG energies within 50%. Where the model reproduces best the IG variability, it can be used to fill in the gaps between recording stations, providing a first view of the global IG wave field. Our first application is the estimation of the surface gravity wave contribution to the surface elevation spectra that will be measured by the Surface Water Ocean Topography (SWOT) satellite mission. The actual contribution of IG waves on measured along-track wavenumber spectra varies with the cross-track averaging method. Typically, the strongest IG signal is expected to occur for wavelengths between 2 and 10km. For a given region, the spectral level at 10km wavelength are not very sensitive to the local depth in the range 200 to 5000m. At this wavelength, and on the east side of all mid-latitude ocean basins, the median spectral density associated to free IG waves is of the order of 0.4cm2/(cycle/km), equal to the expected quasi-geostrophic signature of surface currents. IG spectra rise above 4 times this level for 16% of the time. Even at 20km wavelength, spectral levels above 1cm2/(cycle/km) are likely to occur more that 10% of the time for some oceanic regions. © 2014 Elsevier Ltd.

Govinden-Soulange J.,University of Mauritius | Marie D.,Mauritius Oceanography Institute | Kauroo S.,University of Mauritius | Beesoo R.,University of Mauritius | Ramanjooloo A.,Mauritius Oceanography Institute
Tropical Journal of Pharmaceutical Research | Year: 2014

Purpose: To investigate the antimicrobial activity of crude and fractionated extracts of Biemna tubulosa and Stylissa spp. thriving in Trou aux Biches lagoon, North East Mauritius. Methods: Crude extracts (methanol: dichloromethane 1:1) and fractions of Biemna tubulosa and Stylissa spp (hexane, ethyl acetate and butanol) were tested against some bacterial organisms, namely, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis, using broth microdilution assay. The extracts were screened for the presence of compounds that could be responsible for bioactivity. Results: Preliminary chemical screening revealed the presence of tannins, saponins, terpenes, alkaloids and phenols. The hexane fraction of Stylissa spp. and the ethyl actetate and butanol extracts of Biemna tubulosa were more active than the control antibiotic. Maximum antimicrobial activity was noted for the butanol fraction of Biemna tubulosa with minimum inhibitory concentration (MIC) of 0.091 mg/ml against E. coli. The hexane soluble fraction of Stylissa spp. was more active with MIC of 0.125 mg/ml against S. aureus and E. coli and 0.250 mg/ml against E. faecalis. Conclusion: The broad spectrum antibacterial activity of these sponges seemed to be due to the presence of sesterterpenes and triterpenes, alkaloids and tannins detected in the extract fractions. This is probably the first report on the antimicrobial activity of Biemna tubulosa and Stylissa spp. from Mauritius waters. © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. All rights reserved.

Singh M.,Goethe University Frankfurt | Singh M.,Mauritius Oceanography Institute | Kaviani A.,Goethe University Frankfurt | Rumpker G.,Goethe University Frankfurt
Geophysical Research Letters | Year: 2016

It has recently been suggested that the volcanic island of Mauritius may be underlain by a remnant of continental origin termed “Mauritia”. To constrain the crustal thickness beneath Mauritius, we analyzed data from 11 land stations, 10 of which were deployed recently by the RHUM-RUM project. From the recordings, we obtained 382 P-receiver functions (RFs). By applying the H-κ stacking technique, we derive crustal thicknesses of approximately 10–15 km. We observe a considerable variation in the Vp/Vs-ratio caused by a lack of clear multiples. Using forward modeling of RFs, we show that the lack of clear multiples can be explained by a transitional Moho, where the velocity increases gradually. The modeling further indicates that the thickness of this gradient zone is estimated to be approximately 10 km. We argue that our findings suggest oceanic crust thickened by crustal underplating due the mantle plume currently located beneath the La Réunion. ©2016. American Geophysical Union. All Rights Reserved.

Beedessee G.,Mauritius Oceanography Institute | Ramanjooloo A.,Mauritius Oceanography Institute | Surnam-Boodhun R.,Mauritius Oceanography Institute | Van Soest R.W.M.,Netherlands Center for Biodiversity Naturalis | Marie D.E.P.,Mauritius Oceanography Institute
Chemistry and Biodiversity | Year: 2013

Patients diagnosed with Alzheimer's disease (AD) show a characteristic neurochemical deficit of acetylcholine, especially in the basal forebrains. The use of acetylcholinesterase (AChE) inhibitors to retard the hydrolysis of acetylcholine has been suggested as a promising strategy for AD treatment. In this study, we evaluated the acetylcholinesterase inhibitory (AChEI) activities of 134 extracts obtained from 45 species of marine sponges. Thin-layer chromatography (TLC) and microplate assays reveal potent acetylcholinsterase inhibitory activities of two AcOEt extracts from the sponges Pericharax heteroraphis and Amphimedon navalis Pulitzer-Finali. We further investigated the inhibitory kinetics of the extracts and found them to display mixed competitive/noncompetitive inhibition and associated their inhibitory activity partly to terpenoids. Acetylcholinesterase inhibitors from marine organisms have been rarely studied, and this study demonstrated the potential of marine sponges as a source of pharmaceutical leads against neurodegenerative diseases. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich.

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