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Western Indian Ocean (western + indian_ocean)
Selected AbstractsThe Thaikkal-Kadakkarappally Boat: an Archaeological Example of Medieval Shipbuilding in the Western Indian OceanINTERNATIONAL JOURNAL OF NAUTICAL ARCHAEOLOGY, Issue 2 2004Victoria Tomalin Recent excavations at Kadakkarappally in Kerala, south-west India, have unearthed the remains of an iron-fastened boat, believed to predate the earliest known records for the use of iron in South Asian boatbuilding. The design departs significantly from the traditional view of Indian watercraft, although the use of locally available timber and the suitability of the design for use in the backwaters that characterise the region suggest that it was built and used in India. This is the first excavation of its type to take place in Kerala and contradicts the belief, widely held in Kerala, that the survival of organic remains has been negated by the tropical climate of the region. © 2004 The Nautical Archaeology Society [source] Phylogeography of the introduced species Rattus rattus in the western Indian Ocean, with special emphasis on the colonization history of MadagascarJOURNAL OF BIOGEOGRAPHY, Issue 3 2010Charlotte Tollenaere Abstract Aim, To describe the phylogeographic patterns of the black rat, Rattus rattus, from islands in the western Indian Ocean where the species has been introduced (Madagascar and the neighbouring islands of Réunion, Mayotte and Grande Comore), in comparison with the postulated source area (India). Location, Western Indian Ocean: India, Arabian Peninsula, East Africa and the islands of Madagascar, Réunion, Grande Comore and Mayotte. Methods, Mitochondrial DNA (cytochrome b, tRNA and D-loop, 1762 bp) was sequenced for 71 individuals from 11 countries in the western Indian Ocean. A partial D-loop (419 bp) was also sequenced for eight populations from Madagascar (97 individuals), which were analysed in addition to six previously published populations from southern Madagascar. Results, Haplotypes from India and the Arabian Peninsula occupied a basal position in the phylogenetic tree, whereas those from islands were distributed in different monophyletic clusters: Madagascar grouped with Mayotte, while Réunion and Grand Comore were present in two other separate groups. The only exception was one individual from Madagascar (out of 190) carrying a haplotype that clustered with those from Réunion and South Africa. ,Isolation with migration' simulations favoured a model with no recurrent migration between Oman and Madagascar. Mismatch distribution analyses dated the expansion of Malagasy populations on a time-scale compatible with human colonization history. Higher haplotype diversity and older expansion times were found on the east coast of Madagascar compared with the central highlands. Main conclusions, Phylogeographic patterns supported the hypothesis of human-mediated colonization of R. rattus from source populations in either the native area (India) or anciently colonized regions (the Arabian Peninsula) to islands of the western Indian Ocean. Despite their proximity, each island has a distinct colonization history. Independent colonization events may have occurred simultaneously in Madagascar and Grande Comore, whereas Mayotte would have been colonized from Madagascar. Réunion was colonized independently, presumably from Europe. Malagasy populations may have originated from a single successful colonization event, followed by rapid expansion, first in coastal zones and then in the central highlands. The congruence of the observed phylogeographic pattern with human colonization events and pathways supports the potential relevance of the black rat in tracing human history. [source] Temporal variability in fish larval supply to Malindi Marine Park, coastal KenyaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2009Boaz Kaunda-Arara Abstract 1.Larval supply to reef sites influences adult population structure, reef connectivity and conservation potential of marine reserves, but few studies have examined this topic in the Western Indian Ocean (WIO). 2.Fish larval supply to Malindi Marine Park in Kenya was studied using light-traps for a period extending from March 2005 to June 2006. The traps caught pre-settlement fish larvae at two sites spread across the park. Catch rates (number trap,1night,1) were used to represent larval abundance and to test the influence of seasonality and habitat characteristics on larval abundance in the park. 3.Thirty-three species of reef fish larvae in 15 families were sampled. Larval supply to the park was more diverse during the north-east monsoon season (30 species) than in the south-east monsoon season (15 species), with inter-annual variability in abundance. Higher catch rates of larvae occurred in the north-east monsoon month of March in both 2005 and 2006 and the inter-monsoon month of September 2005. 4.Family-specific temporal variation in larval abundance showed dominance of the families Apogonidae and Caesionidae in the park, with higher abundance during the north-east monsoon months. A few families (e.g. Canthigasteridae) showed dominance during the south-east monsoon season. Regression and rank Spearman correlation analyses indicated positive correlation of chlorophyll-a with larval supply while water depth had significant negative correlation with abundance of the Apogonidae and Caesionidae. 5.On a short-term temporal scale larval abundance in the park was highly correlated with the new moon lunar phase more than the full moon. However, on a long-term scale (16 months) larval supply to the park was significant only over a 2-month period and was correlated with environmental productivity more than ambient temperature. These results are useful in understanding the role of larval supply in structuring adult fish populations and the factors that force larval flux at reef sites. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evaluation of mangrove structure and condition in two trans-boundary areas in the Western Indian OceanAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2009S. O. Bandeira Abstract 1.The structure, forest condition and regeneration status of nine mangrove forests in two trans-boundary areas of Mozambique bordering Tanzania and South Africa were studied. The main objective was to estimate the cutting intensity in the selected sites , Saco and Sangala in southern Mozambique; Mecúfi, Pemba, Ibo, Luchete, Ulo in northern Mozambique, and Mngoji 1 and Mngoji 2 in Tanzania. 2.A total of 135, 10,m×10,m quadrats were set in the outer, middle and lower parts of the mangrove forests at all sampling sites. Measurements included stem diameter at breast height (DBH) and height of adult trees (i.e. all trees with stem diameter more than 2.5,cm). Young trees (with stem diameter of less than 2.5,cm) were classified as juveniles. To assess forest condition, trees within the quadrat were classified into intact, partially cut, coppiced, die back and stump. Pole quality was appraised through the classification of the lead stem into three categories,straight, semi-straight and crooked poles. 3.The results indicate different levels of exploitation with Mngoji 1 and Mngoji 2, the most degraded sites, having stump densities of 959,stumps,ha,1 and 592,stumps,ha,1, respectively. Most sites had mostly poles of inferior quality (crooked poles), but high densities of straight and semi-straight poles were found in Mngoji 1 (742,stems,ha,1) and Saco (636,stems,ha,1). 4.Natural regeneration was observed in most sites but not for all species, with adequate regeneration in Saco (14,766 saplings ha,1) and Mecúfi (14,706 saplings ha,1), while low regeneration was recorded in Mngoji 1 and 2 (2212 saplings ha,1 and 4799saplingsha,1, respectively). 5.These results indicate the need for improved mangrove management and replanting especially in mangrove depleted conservation areas of southern Tanzania. Copyright © 2009 John Wiley & Sons, Ltd. [source] Enabling regional management in a changing climate through Bayesian meta-analysis of a large-scale disturbanceGLOBAL ECOLOGY, Issue 3 2010M Aaron MacNeil ABSTRACT Aim, Quantifying and predicting change in large ecosystems is an important research objective for applied ecologists as human disturbance effects become increasingly evident at regional and global scales. However, studies used to make inferences about large-scale change are frequently of uneven quality and few in number, having been undertaken to study local, rather than global, change. Our aim is to improve the quality of inferences that can be made in meta-analyses of large-scale disturbance by integrating studies of varying quality in a unified modelling framework that is informative for both local and regional management. Innovation, Here we improve conventionally structured meta-analysis methods by including imputation of unknown study variances and the use of Bayesian factor potentials. The approach is a coherent framework for integrating data of varying quality across multiple studies while facilitating belief statements about the uncertainty in parameter estimates and the probable outcome of future events. The approach is applied to a regional meta-analysis of the effects of loss of coral cover on species richness and the abundance of coral-dependent fishes in the western Indian Ocean (WIO) before and after a mass bleaching event in 1998. Main conclusions, Our Bayesian approach to meta-analysis provided greater precision of parameter estimates than conventional weighted linear regression meta-analytical techniques, allowing us to integrate all available data from 66 available study locations in the WIO across multiple scales. The approach thereby: (1) estimated uncertainty in site-level estimates of change, (2) provided a regional estimate for future change at any given site in the WIO, and (3) provided a probabilistic belief framework for future management of reef resources at both local and regional scales. [source] Basin-wide warming of the Indian Ocean during El Niño and Indian Ocean dipole yearsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2007J. S. Chowdary Abstract Basin-wide wintertime surface warming is observed in the Indian Ocean during El Niño years. The basin-wide warming is found to be stronger when El Niño and Indian Ocean Dipole (IOD) co-occur. The mechanisms responsible for the basin-wide warming are different for the years with El Niño only (El Niño without IOD) and for the co-occurrence (both El Niño and IOD) years. Strong westward propagation of downwelling Rossby waves is observed in the southern Indian Ocean during the IOD years. Such strong propagation is not seen in the case of the El Niño-only years. This indicates that the ocean dynamics play an important role in winter warming of the western Indian Ocean during the IOD years. The weak easterly wind anomalies in the El Niño-only years show no measurable impact on the Wyrtki Jets, but weakening or reversal of these jets is seen in the IOD years. This strongly suggests that the variability related to surface circulation is due to the local IOD forcing rather than El Niño induced wind anomaly. For the El Niño-only composites, surface heat fluxes (mainly latent heat flux and short wave radiation) play an important role in maintaining the basin-wide surface warming in the Indian Ocean. In the IOD-only composites (when there is no El Niño in the Pacific), such basin-wide warming is not seen because of the absence of ENSO (El Niño and Southern Oscillation) induced subsidence over the eastern Indian Ocean. For the years in which both El Niño in the Pacific and dipole in the Indian Ocean co-occur, warming in the western Indian Ocean is due to the ocean dynamics and that in the eastern Indian Ocean is due to the anomalous latent heat flux and solar radiation. Copyright © 2007 Royal Meteorological Society [source] Age and growth of the Randall's threadfin bream Nemipterus randalli (Russell, 1986), a recent Lessepsian migrant in Iskenderun Bay, northeastern MediterraneanJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2010D. Erguden Summary Randall's threadfin bream, Nemipterus randalli, first recorded in Iskenderun Bay in Turkey in 2008, seems to have increased in the region. The species, widespread in the western Indian Ocean and with a rapid expansion, appears to have migrated to the bay via the Red Sea. Although its presence in the region has been published, there has been little or no information as to age and growth parameters of this Lessepsian migrant in its new habitat. The present study aims to determine the basic age and growth parameters of the species colonized in the region. A total of 379 collected individuals were studied from November 2007 to October 2008. Total specimen lengths ranged from 4.80 to 21.50 cm, and weights from 1.10 to 138.36 g. Maximum age was 3 years for both sexes. The length,weight relationship was described as W = 0.0011 × L3.061 (r2 = 0.982). The von Bertalanffy growth parameters were: L, = 34.96 cm; K = 0.214 year,1; t0 = ,1.244 year for the entire population. These data were compared with results from studies made in other geographic areas. [source] Long-standing environmental conditions, geographic isolation and host,symbiont specificity influence the relative ecological dominance and genetic diversification of coral endosymbionts in the genus SymbiodiniumJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Todd C. LaJeunesse Abstract Aim, This study examines the importance of geographic proximity, host life history and regional and local differences in environment (temperature and water clarity) in driving the ecological and evolutionary processes underpinning the global patterns of diversity and distribution of symbiotic dinoflagellates. By comparing and contrasting coral,algal symbioses from isolated regions with differing environmental conditions, we may assess the potential of coral communities to respond to significant changes in climate. Location, Indian Ocean. Methods, Community assemblages of obligate symbiotic invertebrates were sampled at numerous sites from two regions, the north-eastern Indian Ocean (Andaman Sea, western Thailand) and the western Indian Ocean (Zanzibar, Tanzania). Molecular genetic methods, including denaturing gradient gel electrophoresis analysis of the ribosomal internal transcribed spacers, DNA sequencing and microsatellite genotyping, were used to characterize the ,species' diversity and evolutionary relationships of symbiotic dinoflagellates (genus Symbiodinium). Host,symbiont specificity, geographic isolation and local and regional environmental factors were evaluated in terms of their importance in governing the distribution and prevalence of certain symbiont taxa. Results, Host-generalist symbionts (C3u and D1-4, formerly D1a now designated Symbiodinium trenchi) frequently occurred alone and sometimes together in hosts with horizontal modes of symbiont acquisition. However, the majority of Symbiodinium diversity consisted of apparently host-specific ,species'. Clade C Symbiodinium were diverse and dominated host assemblages from sites sampled in the western Indian Ocean, a pattern analogous to symbiont communities on the Great Barrier Reef with similar environmental conditions. Clade D Symbiodinium were diverse and occurred frequently in hosts from the north-eastern Indian Ocean, especially at inshore locations, where temperatures are warmer, water turbidity is high and large tidal exchanges commonly expose coral populations to aerial desiccation. Main conclusions, Regional and local differences in cnidarian,algal combinations indicate that these symbioses are ecologically and evolutionarily responsive and can thrive under various environmental conditions. The high temperatures and turbid conditions of the north-eastern Indian Ocean partly explain the ecological success of Clade D Symbiodinium relative to Clade C. Phylogenetic, ecological and population genetic data further indicate that Clade D has undergone an adaptive radiation, especially in regions around Southeast Asia, during the Pleistocene. [source] Phylogeography of the introduced species Rattus rattus in the western Indian Ocean, with special emphasis on the colonization history of MadagascarJOURNAL OF BIOGEOGRAPHY, Issue 3 2010Charlotte Tollenaere Abstract Aim, To describe the phylogeographic patterns of the black rat, Rattus rattus, from islands in the western Indian Ocean where the species has been introduced (Madagascar and the neighbouring islands of Réunion, Mayotte and Grande Comore), in comparison with the postulated source area (India). Location, Western Indian Ocean: India, Arabian Peninsula, East Africa and the islands of Madagascar, Réunion, Grande Comore and Mayotte. Methods, Mitochondrial DNA (cytochrome b, tRNA and D-loop, 1762 bp) was sequenced for 71 individuals from 11 countries in the western Indian Ocean. A partial D-loop (419 bp) was also sequenced for eight populations from Madagascar (97 individuals), which were analysed in addition to six previously published populations from southern Madagascar. Results, Haplotypes from India and the Arabian Peninsula occupied a basal position in the phylogenetic tree, whereas those from islands were distributed in different monophyletic clusters: Madagascar grouped with Mayotte, while Réunion and Grand Comore were present in two other separate groups. The only exception was one individual from Madagascar (out of 190) carrying a haplotype that clustered with those from Réunion and South Africa. ,Isolation with migration' simulations favoured a model with no recurrent migration between Oman and Madagascar. Mismatch distribution analyses dated the expansion of Malagasy populations on a time-scale compatible with human colonization history. Higher haplotype diversity and older expansion times were found on the east coast of Madagascar compared with the central highlands. Main conclusions, Phylogeographic patterns supported the hypothesis of human-mediated colonization of R. rattus from source populations in either the native area (India) or anciently colonized regions (the Arabian Peninsula) to islands of the western Indian Ocean. Despite their proximity, each island has a distinct colonization history. Independent colonization events may have occurred simultaneously in Madagascar and Grande Comore, whereas Mayotte would have been colonized from Madagascar. Réunion was colonized independently, presumably from Europe. Malagasy populations may have originated from a single successful colonization event, followed by rapid expansion, first in coastal zones and then in the central highlands. The congruence of the observed phylogeographic pattern with human colonization events and pathways supports the potential relevance of the black rat in tracing human history. [source] Propagation mechanisms for the Madden-Julian OscillationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 569 2000Adrian J. Matthews Abstract The Madden-Julian Oscillation (MJO) is examined using 20-years of outgoing long-wave radiation and National Centers for Environmental Prediction/National Center for Atmospheric Research re-analysis data. Two mechanisms for the eastward propagation and regeneration of the convective anomalies are suggested. The first is a local mechanism operating over the warm-pool region. At the phase of the MJO with a dipole structure to the convection anomalies, there is enhanced tropical convection over the eastern Indian Ocean and reduced convection over the western Pacific. Over the equatorial western Indian Ocean, the equatorial Rossby wave response to the west of the enhanced convection includes a region of anomalous surface divergence associated with the anomalous surface westerlies and pressure ridge. This lends to suppress ascent in the boundary layer and shuts off the deep convection, eventually leading to a convective anomaly of the opposite sign. Over the Indonesian sector, the equatorial Kelvin wave response to the east of the enhanced convection includes a region of anomalous surface convergence into the anomalous equatorial surface easterlies and pressure trough, which will tend to favour convection in this region. The Indonesian sector is also influenced by an equatorial Rossby wave response (of opposite sign) to the west of die reduced convection over the western Pacific, which also has a region of anomalous surface convergence associated with its anomalous equatorial surface easterlies and pressure trough. Hence, convective anomalies of either sign tend to erode themselves from the west and initiate a convective anomaly of opposite sign via their equatorial Rossby wave response, and expand to the east via their equatorial Kelvin wave response. The second mechanism is global, involving an anomaly completing a circuit of the equator. Enhanced convection over the tropical western Pacific excites a negative mean-sea-level pressure (m.s.l.p.) anomaly which radiates rapidly eastward as a dry equatorial Kelvin wave at approximately 35 m s,1 over the eastern Pacific. It is blocked by the orographic barrier of the Andes and Central America for several days before propagating through the gap at Panama. After rapidly propagating as a dry equatorial Kelvin wave over the Atlantic, the m.s.l.p. anomaly is delayed further by the East African Highlands before it reaches the Indian Ocean and coincides with the development of enhanced convection at the start of the next MJO cycle. [source] Inter- and Extra-Indian Admixture and Genetic Diversity in Reunion Island Revealed by Analysis of Mitochondrial DNAANNALS OF HUMAN GENETICS, Issue 3 2009Vincent Dubut Summary Reunion Island is a French territory located in the western Indian Ocean. The genetic pattern of the Reunionese population has been shaped by contributions from highly contrasting regions of the world. Over the last 350 years, several migration waves and cultural and socio-economic factors have led to the emergence of six main ethnic groups in Reunion. India is one of the principal regions that contributed to the setting up of the Reunionese population. Diversity, demographic and admixture analyses were performed on mtDNA variation of the Reunionese of Indian ancestry, including the Malbar and Zarab ethnic groups, in order to question their history. Using a phylogeographical approach, we generated and analysed quantitative data on the contribution of the Indian parental populations. Furthermore, we showed that the settlement of Reunion Island by Indians did not involve a founder effect, except in the very beginning of the Reunionese settlement (at the end of the 17th century). The accuracy of our results was optimised by a re-evaluation of the classification of the Southern Asian mtDNA haplogroups. Finally, by comparing our results to a previous study dealing with the Reunionese population, we highlighted how ethno-historical data are critical for reconstructing the complex history of multiethnic populations. [source] Movement of sonically tagged bluespine unicornfish, Naso unicornis, in relation to marine reserve boundaries in Rodrigues, western Indian OceanAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2010Emily Hardman Abstract 1.The lagoon fishery of Rodrigues has considerable socio-economic importance; however, catches have declined by 50% in recent years. The bluespine unicornfish, Naso unicornis (Forsskål 1775) is an important component of the fishery. 2.To begin to assess whether marine reserves might benefit this species, sonic telemetry was used to track individual fish in one of Rodrigues' four marine reserves. Seven unicornfish were caught in the Grand Bassin reserve and tagged with abdominally implanted acoustic tags. 3.Over a period of 57 days their locations were determined up to 21 times using a hand held hydrophone and receiver. Individual minimum convex polygon (MCP) home ranges varied from ,10 000,m2 to ,274,000,m2 and were not correlated with fish size. Kernel estimates of core areas (50% utilization distribution) varied from ,5000,m2 to ,175,000,m2. All seven fish stayed within the marine reserve and the largest home range occupied less than ,2% of the area of the marine reserve. 4.Fish remained on the outside edge of the lagoon on the shallow reef slope and among coral patches. These findings suggest that bluespined unicornfish biomass and numbers should increase if the Grand Bassin marine reserve is closed to fishing. Long-term monitoring will, however, be required to demonstrate this outcome. Copyright © 2010 John Wiley & Sons, Ltd. [source] Tracking island colonization history and phenotypic shifts in Indian Ocean bulbuls (Hypsipetes: Pycnonotidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2005BEN H. WARREN Molecular phylogenies of island organisms provide useful systems for testing hypotheses of convergent or parallel evolution, since selectively neutral molecular characters are likely to be independent of phenotype, and the existence of similar environments on multiple isolated islands provides numerous opportunities for populations to evolve independently under the same constraints. Here we construct a phylogenetic hypothesis for Hypsipetes bulbuls of the western Indian Ocean, and use this to test hypotheses of colonization pattern and phenotypic change among islands of the region. Mitochondrial sequence data were collected from all extant taxa of the region, combined with sequence data from relevant lineages in Asia. Data are consistent with a single Hypsipetes colonization of the western Indian Ocean from Asia within the last 2.6 Myr. The expansion of Hypsipetes appears to have occurred rapidly, with descendants found across the breadth of its western Indian Ocean range. The data suggest that a more recent expansion of Hypsipetes madagascariensis from Madagascar led to the colonization of Aldabra and a secondary colonization of the Comoros. Groupings of western Indian Ocean Hypsipetes according to phenotypic similarities do not correspond to mtDNA lineages, suggesting that these similarities have evolved by convergence or parallelism. The direction of phenotypic change cannot be inferred with confidence, since the primary expansion occurred rapidly relative to the rate of mtDNA substitution, and the colonization sequence remains uncertain. However, evidence from biogeography and comparison of independent colonization events are consistent with the persistence of a small grey continental bulbul in India and Madagascar, and multiple independent origins of large size and green plumage in insular island populations of the Comoros, Mascarenes and Seychelles. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 271,287. [source] | ||||||||||||||||