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The equatorial Kelvin waves, remotely excited by basin‐scale climate modes, and subsequent coastal trapped waves significantly influence the intraseasonal variations, their low‐frequency modulations, and the frequency of extreme sea level events along the western coast of India. This study demonstrates that the frequency of extreme events are linked to the phase of the Indian Ocean Dipole mode. The temporal changes in the occurrence frequency of extremes are simulated in an eddy‐resolving ocean model consistently with observations. However, a non‐eddying model significantly underestimate the occurrence frequency of extreme sea level events, suggesting the importance of coastal trapped wave propagations regulated by the horizontal scale with the Rossby radius of deformation. This result implies that many state‐of‐the‐art climate models with a one‐degree ocean horizontal resolution may underestimate future coastal sea level variability and the frequency of extreme events under global warming and potential modulations of major internal climate modes. Plain Language Summary: Sea level variations in the northern Indian Ocean are influenced by ocean waves near the coast, typically in a horizontal scale less than 100 km. It remains unclear whether there is a relationship between extreme events associated with coastal waves and climate variability. Also, if such a relationship exists, it is uncertain how well it is represented in climate simulations, which often have relatively coarse horizontal resolution. To highlight the role of relatively small scale coastal waves, this study compared sea level variations along the western coast of India using two ocean models with coarse and fine horizontal resolutions. We found that the high‐resolution model adequately simulates the generation and propagation of coastal waves, and thus successfully simulate sea level variations along western India modulated by large scale climate variability with a 20–150‐day time scale. This result suggests that many recent climate simulations may have underestimated the frequency of extreme sea level events in coastal regions. Key Points: The eddy‐resolving model represents the intrasesonal sea level variability along the coast of India explained by coastal trapped wavesThe occurrence frequency of extreme intraseasonal sea level anomalies is significantly underestimated in the non‐eddying modelChanges in the probability distributions of sea level associated with the Indian Ocean Dipole are simulated in the eddy‐resolving model [ABSTRACT FROM AUTHOR]

Introduction: Hydrothermal vents, rich in heavy metals, provided a unique niche for heavy metal resistant microbes. However, knowledge about copper resistant microbes in deep sea hydrothermal vents is still limited. Methods: The copper-resistant bacteria were isolated from deep-sea hydrothermal vent samples and conducted thorough physical, phylogenetic, and genomic analyses to elucidate their copper resistance capability and related genes. Results: Twelve highly copper-resistant bacteria (up to 6-10 mM) were isolated from deep sea hydrothermal fields They were affiliated with the Pseudoalteromonas (4), Marinobacter (3), Halomonas (2), Psychrobacter (1), and Pseudomonas (1) genus in the α-Proteobacteria, and the Sphingomonas (1) genus in the β-Proteobacteria. The presence of copper in the medium obviously induced the amount of polysaccharides and proteins in the crude extracellular polymeric substances (EPS) produced by Halomonas sp. CuT 3-1, Pseudoalteromonas sp. CuT 4-3 and Marinobacter metalliresistant CuT 6, which could absorb 40 to 50 mg•g-1 copper. We further described a novel species, Marinobacter metalliresistant sp. nov. CuT 6T, which exhibited a higher copper resistance and encoded more heavy metal resistance-related genes than other Marinobacter species. Discussion: It revealed that the copper resistance capability exhibited by these strains in hydrothermal fields is likely attributed to the production of exopolymeric substances, such as polysaccharides and proteins, as well as active transport or efflux mechanisms for heavy metals. [ABSTRACT FROM AUTHOR]

In the years prior to legal emancipation, British officials enacted a series of laws intended to ameliorate the condition of those held in slavery in their colonies. This article investigates the impact of amelioration on the islands of the Seychelles immediately prior to emancipation. While the legal changes, including the dispatch of a Protector of Slaves to the Seychelles, were limited in terms of effectiveness, their implementation offered people new avenues to protest mistreatment and engage directly with the language of abolition. Reports filed by the protector highlight people's uncertainty and isolation during the years leading up to emancipation. While there is evidence of resistance through uprisings, desertions, and the filing of formal complaints, people in the Seychelles faced significant challenges as owners used the islands' distance from colonial oversight to maintain control through violence and patriarchal structures of domination. As remote 'island laboratories', however, the islands offer unique insights into the ways in which people managed to leverage British abolitionism to their advantage even on such isolated islands. [ABSTRACT FROM AUTHOR]

The hadal zone (water depths > 6000 m) are unlike the overlying shallower marine regions (bathyal and abyssal) as it does not follow a continuum from the continental shelves to abyssal plains, but rather exhibits a globally disjunct series of discrete deep-sea habitats confined within geomorphological features. From an ecological perspective, hadal communities are often endemic to individual or adjacent features and are partitioned and isolated by geomorphological structures. To examine the size, shape, depth and degree of isolation of features where hadal fauna inhabit, this study explores the broad seafloor geomorphology, and distinctly partitioned hadal areas, across the Southwest Pacific and East Indian oceans using global bathymetric datasets. This research revealed the area occupied by hadal depths to be 716,915 km2 of which 58% are accounted for by trenches, 37% in basins and troughs, and 5% fracture zones. The largest feature in terms of area > 6000 m depth is the Wharton Basin with 218,030 km2 spanning 376 discrete areas. The largest continuous hadal habitats were the Kermadec and Tonga trenches at 145,103 and 111,951 km2 respectively, whereas features such as the Java Trench comprise two hadal components partitioned by a bathymetric high. Conversely, no physical barrier exists between the New Britain and Bougainville trenches thus any literature pertaining to hadal species or habitats from these trenches can be merged. This study highlights that the hadal zone mainly comprises two main geomorphological features (trenches and basins) that differ in size, depth and complexity. Hadal basins cover vast, generally shallower areas, comparable to abyssal plains, whereas trenches, despite a lesser footprint, represent greater depth ranges and complexity. As such, sampling designs and interpretation of ecological data must differ and hadal basins likely play an increasingly important role in understanding ecological shifts from abyssal to hadal ecosystems. [ABSTRACT FROM AUTHOR]

Evaluation of fish stock status is a key step for fisheries management. Tuna Regional Fisheries Management Organizations (t-RFMOs) are moving towards management strategy evaluation (MSE), a process that combines science and policy and depends on technical aspects, developed by scientists, designed to meet management objectives established by managers and other stakeholders. In the Indian Ocean, the current management advice for swordfish (Xiphias gladius) is based on an ensemble of 24 models considering four areas of uncertainty about the stock dynamics. There is an ongoing MSE process for swordfish, and this paper describes the methodology being applied for the conditioning of the operating model (OM), including model selection and validation. In the MSE, nine sources of uncertainty were considered, each being characterized by 2–3 levels. A partial factorial design was employed to reduce the number of models from a full factorial design to those needed to encompass the overall uncertainty. A selection and validation process was carried out, filtering models that converged, showed good predictive skills, and provided plausible estimates. Overall, the estimated spawning stock biomass (SSB) relative to SSB at maximum sustainable yield (MSY), and fishing mortality (F) relative to FMSY encompasses the estimates of the stock assessment ensemble at the most optimist area of the distribution. The MSE for swordfish is an ongoing process that is expected to provide more robust management advice in the future. Further developments to the OM can still occur, but the methods presented herein can be applied to this, or other species, MSE processes. [ABSTRACT FROM AUTHOR]

We study the near-inertial response of the salinity-stratified north Bay of Bengal to monsoonal wind forcing using 6 years of hourly observations from four moorings. The mean annual energy input from surface winds to near-inertial mixed layer currents is 10–20 kJ m−2, occurring mainly in distinct synoptic "events" from April–September. A total of fifteen events are analyzed: Seven when the ocean is capped by a thin layer of low-salinity river water (fresh) and eight when it is not (salty). The average near-inertial energy input from winds is 40% higher in the fresh cases than in the salty cases. During the fresh events, 1) mixed layer near-inertial motions decay about two times faster and 2) near-inertial kinetic energy below the mixed layer is reduced by at least a factor of three relative to the salty cases. The near-inertial horizontal wavelength was measured for one fresh and one salty event; the fresh was about three times shorter initially. A linear model of near-inertial wave propagation tuned to these data reproduces 2); the thin (10 m) mixed layers during the fresh events excite high modes, which propagate more slowly than the low modes excited by the thicker (40 m) mixed layers in the salty events. The model does not reproduce 1); the rapid decay of the mixed layer inertial motions in the fresh events is not explained by the linear wave propagation at the resolved scales; a different and currently unknown set of processes is likely responsible. [ABSTRACT FROM AUTHOR]

The East African Coastal Current (EACC) is an important western boundary current of the tropical south Indian Ocean and plays an important role in the ocean circulation and biogeochemical cycles in the Indian Ocean. This study investigates the interannual variability of the EACC and its dynamical mechanisms. The result shows that the EACC has interannual variability associated with El Niño–Southern Oscillation (ENSO) during 1993–2017. The EACC shows a significantly positive correlation with the Niño-3.4 index with a correlation coefficient of 0.65, lagging the Niño-3.4 index by 18 months. During the decaying phases of El Niño (La Niña) events, the negative (positive) sea level anomaly (SLA) propagates westward as upwelling (downwelling) Rossby waves from the southeast Indian Ocean to the southwest Indian Ocean and then strengthens (weakens) the EACC due to zonal SLA gradient off the East African coast under geostrophic equilibrium. The SLA gradually weakens in the southeast Indian Ocean during its westward propagation but strengthens in the southwest Indian Ocean promoted by local wind stress curl anomaly. This study can improve our understanding of the relationship between the western boundary current of the tropical south Indian Ocean and large-scale ENSO air–sea processes and is important for managing marine fisheries and ecosystems on the East African coast. [ABSTRACT FROM AUTHOR]

This paper discusses the upgraded data assimilation (DA) wave forecasting system at the Indian National Centre for Ocean Information Services (INCOIS). Significant wave height (SWH) observations from deep and shallow water buoys in the North Indian Ocean are incorporated into the assimilation system in conjunction with satellite observations from SARAL/AltiKa, Jason-3, Sentinel-3a, and Sentinel-3b. In deep water, satellite DA improved the SWH forecast by ~16%, and the inclusion of buoy observations enhanced it up to ~43% in the initial forecast hours. The impact of satellite DA persists throughout the forecast period of 5 days for swell height, with 11–27% improvement. Ingestion of buoy observations further improved it up to ~31.5% at the 3rd hr forecast. For the wind–sea height, buoy DA resulted in an improvement of 9–26% during the initial 12 hr. In general, the positive impact of buoy DA only lasts till the 30th hr forecast. In shallow water, the impact of satellite DA on SWH prediction is moderate, with positive improvements of 4–7.5%. Adding buoy observations significantly improved it to 10–40% in the initial 12 hr, especially for the low wave heights. Although the buoy DA improved the prediction of wave periods compared to the non-assimilated model, it tends to degrade the forecast compared to the model with satellite DA alone. This points to the limitation of the current assimilation approach in correcting the wave energy distribution in the background spectrum, particularly at higher frequencies. [ABSTRACT FROM AUTHOR]

2019 witnessed one of the strongest positive Indian Ocean Dipole. A very strong positive subsurface mode (pSSM) co-evolved in the Tropical Indian Ocean (TIO) during September–October–November 2019, which strengthened further during December–January–February (DJF) 2019–2020. This is the first occurrence of such a very strong pSSM in the recent decades, which strengthened during DJF without any favourable forcing from the Pacific. The TIO further displayed anomalous basin-wide surface warming from winter 2019 to summer 2020. It is found from both observations and model experiments that ocean dynamics associated with pSSM played a major role in the TIO basin-wide warming during 2020. The subsurface–surface interaction along the downwelling Rossby wave path from boreal winter to spring, the reflected Kelvin waves and surface currents have contributed to the basin-wide surface warming of the TIO from DJF (2019–2020) onwards. The mixed layer heat budget analysis reveals that the surface heat fluxes were not favourable for the basin-wide surface warming, thereby undermining the role of any Pacific forcing through atmospheric pathways. The ocean model sensitivity experiments further highlight the importance of Indian Ocean dynamics in the co-evolution of subsurface temperature and sea surface temperature over TIO, especially during the 2019–2020 event. Research highlights: A strong subsurface dipole mode evolved in the Tropical Indian Ocean temperature during 2019–2020. Indian Ocean basin-wide surface warming persisted up to summer 2020, highlighting the role of ocean dynamics. Indian Ocean dynamics associated with the subsurface mode is responsible for the evolution of basin-wide surface warming. Ocean model experiments support the role of ocean dynamics in the evolution of basin-wide surface warming. [ABSTRACT FROM AUTHOR]

Recent research has shown that there is a projected increase in the frequency of strong positive Indian Ocean dipole (spIOD) events in terms of both sea surface temperature (SST) and precipitation. However, it is not clear whether the spIOD events defined by SST and precipitation, hereafter referred to as SST-spIOD and Pr-spIOD events, respectively, will increase at the same pace under greenhouse warming. Using climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and CMIP6 that can reasonably simulate the spIOD events, here we find that the occurrence of Pr-spIOD events increases much more than that of SST-spIOD events (+217% vs +77%) under the future high-emission scenario. The diverse response stems from a notably large increase in the spIOD events with strong rainfall but moderate SST anomalies (Pr-only spIOD), which is facilitated by a change in the local meridional Hadley circulation induced by land–sea thermal contrast in addition to the background mean-state SST warming. For the spIOD events with prominent anomalies in both rainfall and SST (concurrent spIOD), their occurrences are projected to increase, but their average SST amplitude is projected to weaken. The increased occurrence is associated with a westward-extended structural change induced by mean linear zonal advection feedbacks, while the weakened event-average SST amplitude results from a more stabilized atmosphere and coincides with the projected reduction in IOD SST skewness. Our results suggest that IOD-related mitigation strategies should consider the diverse responses of different kinds of spIOD events to greenhouse warming. [ABSTRACT FROM AUTHOR]

This study identifies two distinct patterns of the summer Indian Ocean dipole (IOD)—the coastal IOD and the offshore IOD—named based on the proximity of their eastern pole to Sumatra. Their spatial characteristics, evolutionary mechanisms, relationships with ENSO, impacts on precipitation, and the factors controlling the simulation performances of climate models are discussed. The coastal IOD has the same eastern pole as the conventional IOD, which is located off the coast of Sumatra, but its western pole is situated in the central region of the tropical Indian Ocean (TIO). In contrast, the offshore IOD shares the same western pole as the conventional IOD, which is located off the coast of Somalia, whereas its eastern pole is positioned in the central TIO. Regarding their evolutions, while they initially develop similarly, their later evolutions differ due to their distinct pole locations: The offshore IOD peaks in summer, while the coastal IOD can be sustained into autumn. The coastal IOD correlates to preceding and late ENSO states, but the offshore IOD does not, making it an independent internal mode of TIO. The two IODs affect climate differently, with only the coastal IOD affecting Australian rainfall. Climate models exhibit varied levels of performance in simulating the two IODs. Specifically, a stronger link between spring TIO rainfall and ENSO, as well as stronger southeasterly monsoon winds in the southern TIO, can enhance the coastal IOD modeling, while a stronger summer Somali jet benefits the simulation of the offshore IOD. Distinguishing these two IODs has implications for accurate diagnosis and prediction of the summer climate surrounding the TIO. Significance Statement: The Indian Ocean dipole (IOD) significantly influences the monsoon climate. Previous studies use a unified IOD index based on all-season sea surface temperature (SST) data of tropical Indian Ocean (TIO), resulting in a representation biased toward the autumn peak season. However, understanding SST patterns during summer is crucial for Asian summer monsoon precipitation, and what are the characteristic patterns of summer IOD remains unclear. This study fundamentally advances the understanding of the IOD's seasonal diversity by identifying two distinct dipole patterns in the summer TIO. These patterns differ from the conventional IOD in terms of spatial characteristics, evolutions, ENSO relationships, and precipitation impacts. Distinguishing between these two IODs is anticipated to improve the diagnosis and prediction of summer monsoon rainfall. [ABSTRACT FROM AUTHOR]

The authors discuss the genetic diversity in the Read Sea and related aquatic environments. They talk about the diverse ecosystem of the Red Sea, areas that provide habitats for versatile marine organisms such as invertebrates, sharks, and other fishes, and the status of the Red Sea genetic diversity studies, gaps and future directions.

Low–lying coral islands are susceptible to rising sea levels and climate change, posing risks to island habitability over the next century. The decadal timescale evolution of the islands can provide an understanding of the governing controls of change and island response. This study investigates variations in the shoreline morphology of the Lakshadweep coral islands (Northern Indian Ocean/Arabian Sea) using satellite datasets (2003–2022; CNES/Airbus;0.3m – 0.7m resolution) and sedimentological data. Of the thirty islands (ten inhabited), six islands (Bangaram, Thinnakara, Suheli, Minicoy, Androth and Bitra) have been studied. Most of these islands are less than 1 km² in size except Androth and Minicoy (>4 km² ). While the data is discontinuous for the islands due to cloud obscuring, the shoreline morphology depicts variations for all the islands’ studied, irrespective of habitation and size. Larger islands have undergone consistent erosion since 2007 (total land loss is approximately 3 - 5% cumulatively). Smaller islands have undergone lateral migration, with sediment erosion usually along the southern edge and sediment migration and accumulation northwards, however, overall, their size remains consistently stable. The migration of sediments is observed only from 2007–2017, which coincides with severe El–Nino Southern Oscillation (ENSO) and low amplitude positive Indian Ocean Dipole (IOD) events. Furthermore, sedimentological analysis along Bangaram’s (small island) accreting margin reveals unconsolidated bio-detrital grainstones with predominant sand-sized fractions (2 – 0.25mm). Corals (43%), molluscs (33%), forams (13%), and algae (8%) are the major sediment producers (with 3% unidentified bioclasts). The ongoing climate warming and ocean acidification will influence the carbonate sediment budget in addition to the changing hydrodynamics owing to monsoons, cyclones, and coupled ocean-atmospheric regional phenomenon, altering the sediment production, transport and accumulation on these islands. Furthermore, rising sea levels and consequent erosion by wave action might lead to rapid drowning in the next few centuries. Our study identifies the current status of the island size variability in the Lakshadweep Archipelago and how site-specific and global factors influence them, thus providing insights into assessing the habitability within these low-lying coral islands. [ABSTRACT FROM AUTHOR]

Atmospheric teleconnections from the Pacific El Niño are key to determining the East Asian winter climate. Using the database for policy decision-making for future climate change (d4PDF) large-ensemble simulations, the present study investigates a mechanism for the warm and cold East Asian winters during El Niño with a focus on atmospheric teleconnections triggered by anomalous sea surface temperature (SST) patterns in the tropical Indo-Pacific. Our results show that the western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP pattern tends to appear in years when both an early El Niño and the positive phase of the Indian Ocean dipole (IOD) mode develop in boreal autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies indicate that the WP pattern is associated with the weakened Indo-Pacific Walker circulation. By contrast, the WP pattern does not dominate in the cold winters due to the absence of strong TIO warming. The present study proposes a mechanism that promotes the excitation of the WP pattern through the upper-troposphere divergence in East Asia associated with the Walker circulation modulated by the tropical Indo-Pacific interbasin interaction. Significance Statement: The East Asian winter temperature variability is controlled not only by the strong atmospheric internal variability in the midlatitudes and high latitudes but also by remote forcing from the tropical ocean. Our study investigates how El Niño exerts diverse impacts on the East Asian winter temperature, depending on where atmospheric convection intensifies in the tropical Pacific Ocean and the Indian Ocean. Our results show that an intense warming of the tropical Indian Ocean and the early development of El Niño are the major factors for warm winters in East Asia. Given that a precursor of the intense Indian Ocean warming appears in boreal autumn, our findings should contribute to the improvement of seasonal prediction for the East Asian winter climate. [ABSTRACT FROM AUTHOR]

The analysis of water samples collected during the MD218 CROTALE expedition (February-March, 2019), and the 4th Indian Southern Ocean Expedition (SOE) (January-February, 2010) (re-visited samples) resulted in the occurrence of a new coccolithophore species belonging to the genus Alisphaera, and is named Alisphaera crostae sp. nov. This new species appears monomorphic and shows distinctive morphological differences in terms of its coccolith size, flange structure, and nodules, compared to other known Alisphaera species. In this study, morphological differences between A. crostae and other Alisphaera species are illustrated and compared. We suggest that the genus Alisphaera may have a higher diversity and may possess a wider distribution than previously evidenced, which requires more careful observation [ABSTRACT FROM AUTHOR]

• Long-term dynamics of algal bloom patterns and their causative factors are assessed. • Time-series satellite data are analyzed and modelled using non-parametric methods. • Increased occurrence and reduction in the areal extent of algal blooms are observed. • The relative influence of ocean, atmosphere, and land parameters changes by regions. • Temporal prediction of blooms is possible with a time lag of 2 months. Algal blooms are global phenomena in marine and fresh waters. An understanding of the impacts of climate change and anthropogenic activities on marine algal blooms is essential for protecting marine ecosystems. We have studied the long-term changes in the spatial patterns of algal blooms over the northern Indian Ocean and assessed the influence of the ocean, atmosphere, and land-based processes on them. We have analyzed multi-source satellite data (2003 – 2020) of various parameters such as algal concentration, temperature, salinity, sea level, particulate organic carbon, precipitation, wind speed, and river discharge on an open-source cloud computing platform. The seasonality of variables is assessed using a harmonic model, and their spatial trend is estimated using the non-parametric Mann-Kendall test. The spatial relationship between various geophysical parameters and algal bloom concentration is assessed by the cross-correlation test, and the prediction is done using a multivariate autoregression model. Results suggest that each variable exhibits distinguishable seasonal patterns. Algal bloom duration showed a significant increase over time. However, algal bloom coverage showed a significant decline in the coastal waters in all seasons except post-monsoon. The cross-correlation test unveils that lower temperatures, salinity, and sea level promote algal bloom occurrences in coastal waters rather than open waters. Furthermore, the statistical model with a time lag of 2 months shows better performance for prediction of bloom intensity (r2 = 0.86). [ABSTRACT FROM AUTHOR]

The oriental fruit fly (Bactrocera dorsalis) is one of the world's most invasive and polyphagous fruit pests. It causes severe damage throughout its range and can devastate the entire fruit harvest in unprotected orchards. In 2007, B. dorsalis was detected in Mayotte, where it now ranks ninth on the list of fruit fly species of economic importance. This tropical island is a good study area to analyse the host range of B. dorsalis and its interactions with other resident fruit fly species.Two field campaigns were carried out from 2012 to 2014 and from 2019 to 2021. We collected fruit from all over the island in cultivated and non‐cultivated areas and compared the infestation rates between the two periods.We detected six fruit fly species, including the common species Dacus ciliatus, Neoceratitis cyanescens, Ceratitis capitata, B. dorsalis and two rarer species, Dacus etiennellus and Trirhithrum nigerrimum.The most surprising result was the low occurrence of B. dorsalis, with only seven host plant species identified out of a total of 84 plant species. Infestation rates were low for these host plant species, even in the case of mango (11.71 flies/kg) and Indian almond (0.97 fly/kg), which are considered to be major host plants of B. dorsalis.Bactrocera dorsalis seems to have a lower impact in Mayotte than in other parts of the world. We discuss the possible causes of the weak infestation rates observed, which could provide the key to regulating the species on the island. [ABSTRACT FROM AUTHOR]

Introduction: A sustainable fishery relies on consistent and substantial recruitment. There is, however, considerably high mortality among fish larvae during their early development. One of the most important factors determining larval survival is foraging success. Bigeye tuna is among the most important commercial species in the Indian Ocean. Despite being routinely researched and assessed, it remains unclear how food availability affects the recruitment success of bigeye tuna. Methods: In this study, we used phytoplankton size (MD50) as an indicator of prey availability and investigated the connection betweenMD50 and bigeye tuna recruitment from 2000 to 2018 through the Beverton-Holt stock-recruitment function. The Indian Ocean was divided into four regions to accommodate spatial differences. Results: As a result, larger MD50 could bring higher recruitment, particularly in the eastern and southern Indian Ocean. Based on the analysis, we inferred that for bigeye tuna, the eastern Indian Ocean is the primary spawning ground, and the peak spawning period falls in Season 2 (April-June). Discussion: The conclusions provide valuable insights for understanding the recruitment characteristics of bigeye tuna in the Indian Ocean. [ABSTRACT FROM AUTHOR]

Context: The quagga catshark (Halaelurus quagga) is a small-sized (~370-mm total length), deep-water catshark (Family: Pentanchidae), assessed as Data Deficient on the IUCN Red List. Aim: We aimed to bridge critical knowledge gaps on aspects of the life history and exploitation of H. quagga to make a meaningful Red List assessment, and develop management plans. Methods: Specimens landed as bycatch in three harbours along the Laccadive Sea coast of south-western India were examined to gather the first information on exploited length classes and aspects of reproductive biology. Key results: Halaelurus quagga had a female-dominated sex ratio, a positively allometric growth in females, and isometric growth in males. Mature H. quagga males ranged between 294 and 336 mm, and females between 315 and 370 mm, with pregnant females carrying two, three or four egg cases with embryos in each uterus. Conclusions: This study provides the first information on the biology and exploitation of H. quagga , showing that the species is landed (and discarded) as bycatch in trawl fisheries, with the catches comprising a significant amount of reproductively active individuals. Implications: The intense deep-sea bottom-trawling off south-western India is a major threat to H. quagga , and, if left unmanaged, could likely trigger a threatened category on the IUCN Red List. The first study on the exploitation levels and aspects of biology of Halaelurus quagga , a poorly known deep-water catshark, showed a female-dominated sex ratio, a positively allometric growth in females and isometric growth in males. Mature H. quagga males ranged between 294 and 336 mm, and females between 315 and 370 mm, with pregnant females carrying two, three or four egg cases, with embryos in each uterus. This species is landed (and discarded) as bycatch in shrimp fisheries, with the catches comprising a significant amount of reproductively active individuals. [ABSTRACT FROM AUTHOR]

The tropical southwest Indian Ocean is a coral biodiversity hotspot, with remote reefs physically connected by larval dispersal through eddies and a complex set of equatorial and boundary currents. Based on multidecadal, 2 km resolution hydrodynamic and larval dispersal models that incorporate temporal variability in dispersal, we find that powerful zonal currents, current bifurcations, and geographic isolation act as leaky dispersal barriers, partitioning the southwest Indian Ocean into clusters of reefs that tend to consistently retain larvae, and therefore gene flow, over many generations. Whilst exceptionally remote, the Chagos Archipelago can broadcast (and receive) considerable numbers of larvae to (and from) reefs across the wider southwest Indian Ocean, most significantly exchanging larvae with the Inner Islands of Seychelles, but also the Mozambique Channel region. Considering multi-generational dispersal indicates that most coral populations in the southwest Indian Ocean are physically connected within a few hundred steps of dispersal. These results suggest that regional biogeography and population structure can be largely attributed to geologically recent patterns of larval dispersal, although some notable discrepancies indicate that palaeogeography and environmental suitability also play an important role. The model output and connectivity matrices are available in full and will provide useful physical context to regional biogeography and connectivity studies, as well as supporting marine spatial planning efforts. [ABSTRACT FROM AUTHOR]

Introduction: Pelagic cephalopods play a key role in the Chinese food supply. The market value of seafood frequently fluctuates based on its geographical origin and species, making it imperative to trace the origin and distinguish forms to guarantee food quality and accurate information. Methods: In this study, we used biochemical tracers, including stable isotope analysis and fatty acid composition profiling, to trace the origin of purpleback flying squid (Sthenoteuthis oualaniensis) from the Indian Ocean and South China Sea. We measured the d13C and d15N values and fatty acid (FA) contents in samples from different forms of S. oualaniensis obtained from these two oceanic regions. We analyzed the feeding and nutritional differences among these populations and conducted discriminant analysis. Results and discussion: Significant regional and form differences were observed in both isotopic values and FA profiles in the muscle tissues of S. oualaniensis. Forms with larger sizes exhibited higher d13C and d15N values, potentially resulting from different feeding preferences and geographical environments. The discriminant analysis revealed that isotopic composition could effectively distinguish individuals from different oceanic regions, whereas FA composition was more effective in distinguishing different forms within the same oceanic region. The combination of isotopes and FAs could accurately discriminate S. oualaniensis of different forms and from different oceanic regions, achieving a discrimination accuracy of 100%. This study provides a reference for tracing the origin of pelagic cephalopods with complex form structures. [ABSTRACT FROM AUTHOR]

The El Niño–Southern Oscillation (ENSO) has a significant impact on the surface climate of East Asia by modulating the atmospheric circulation over the Kuroshio Extension. Here, we show that the ENSO–East Asia teleconnections are strongest in early winter due to the combined effects of the Indian Ocean and Maritime Continent convections, but weakest in mid‐winter as these tropical convections weaken. During the early El Niño winter, convection is enhanced over the Indian Ocean and suppressed over the Maritime Continent. The associated Rossby wave trains constructively interfere over the Kuroshio Extension, resulting in anticyclonic circulation anomalies. The equatorial central Pacific convection has a minimal impact on the East Asia. This result suggests that the Indian Ocean and the Maritime Continent convections, rather than the equatorial central Pacific convection, are the precursors of the early winter ENSO–East Asia teleconnections, and need to be considered for subseasonal‐to‐seasonal prediction in East Asia. Plain Language Summary: The El Niño–Southern Oscillation (ENSO) significantly influences the winter surface climate in East Asia through atmospheric teleconnections. The ENSO teleconnections are particularly pronounced in early winter when an anomalous anticyclonic circulation developes over the Kuroshio Extension and transports warm and moist air to the East Asian continent, but weaken in mid‐winter. Here, we show that such subseasonal variability of the ENSO–East Asia teleconnections is primarily determined by tropical convection over the Indian Ocean and the Maritime Continent, with a minimal impact of convection over the equatorial central Pacific where ENSO develops. Key Points: The El Niño‐Southern Oscillation (ENSO) teleconnections show distinct subseasonal variability over East Asia, with the strongest teleconnections in early winterThe ENSO–East Asia teleconnections are modulated by anomalous tropical convection over the Indian Ocean and the Maritime Continent on subseasonal time scaleRossby wave trains induced by enhanced convection over the Indian Ocean and those by suppressed convection over the Maritime Continent constructively interfere over the East Asia during the early El Niño winter [ABSTRACT FROM AUTHOR]

On decadal time scales, a zonal SST dipole dominates the tropical Indian Ocean in boreal late summer and fall, called the decadal Indian Ocean dipole (D-IOD). The D-IOD has a spatial pattern different from the traditional interannual IOD, with its eastern pole located off Java, rather than the whole Sumatra–Java coasts as the latter. Here, we show that the D-IOD is generated by both the remote tropical Pacific decadal variability (TPDV) forcing and the decadal modulation of interannual IODs, but with its distinctive spatial pattern and seasonality mainly shaped by the former. In August–September (AS), due to the seasonal strengthening of trade winds, the descending branch of TPDV-induced Walker circulation moves westward into the eastern Indian Ocean relative to June–July, which stimulates equatorial easterly anomalies and oceanic upwelling Kelvin waves, causing subsurface cooling off Java. The subsurface cooling just occurs within the time window of climatological coastal upwelling so that subsurface cold anomalies are brought into the surface by mean upwelling and further transported offshore by mean flows, forming the D-IOD eastern pole. The subsurface cooling is only generated near Java but not Sumatra, because the former is closer to the exit of the Indonesian Throughflow (ITF). Weakened ITF during positive TPDV inhibits the growth of subsurface warming off Java prior to the establishment of AS equatorial easterly anomalies, whereas this ITF effect is not observed off Sumatra. Moreover, warming of the D-IOD western pole might be associated with off-equatorial Rossby waves induced by TPDV-related wind stress curls. Significance Statement: The decadal Indian Ocean dipole (D-IOD) is one of the leading decadal modes of the tropical Indian Ocean SST variations. Its formation mechanisms, especially those related to its spatiotemporal characteristics, are not well understood. Based on observations and reanalysis, we show that the tropical Pacific decadal variability (TPDV) mainly accounts for the distinctive spatial pattern and seasonality of the D-IOD via the seasonal migration of the anomalous Walker circulation and ensuing oceanic subsurface dynamics. Our results highlight that the TPDV is an important source of D-IOD's predictability, and it might be beneficial for operational decadal predictions for the tropical Indian Ocean. [ABSTRACT FROM AUTHOR]

Estuaries are often observed as the boundary between the ocean and the river, separating coastal environments, rather than being seen as a continuum. Owing to insufficient research on demersal fish communities across nearshore marine to estuarine habitats, particularly in South Africa, this study employed a spatial seascape approach, with seasonal sampling of soft-bottom benthic habitats in two permanently open estuaries and the adjacent marine nearshore environment of Algoa Bay on the south coast of South Africa. A total of 790 fish representing 29 species were collected in the marine nearshore, and 6 414 fish (28 species) were caught in the estuarine zone. Two discrete demersal fish assemblages were identified as representing the marine nearshore and estuarine environments. The marine nearshore fish assemblages were dominated by marine species (e.g. Argyrosomus inodorus and Cynoglossus zanzibarensis) that were not recorded in the estuarine environment, whereas marine estuarine-opportunist species (e.g. Pomadasys olivaceus and Galeichthys feliceps) were more abundant in the marine nearshore than in the estuarine environment. The estuaries were dominated by benthic marine estuarine-dependent and marine and estuarine species (e.g. Rhabdosargus holubi, Solea turbynei, Heteromycteris capensis, Psammogobius knysnaensis and Glossogobius callidus). Differences observed in abundance and species richness along the estuarine to marine continuum were primarily related to the salinity gradient. These findings are significant as altered freshwater flows and consequent changes in salinity and productivity can have an impact on the nursery use of both estuaries and the marine nearshore by fish species. [ABSTRACT FROM AUTHOR]

This rapid communication describes a lithic blade that was recently recovered during excavations in the Velondriake Marine Protected Area in southwest Madagascar. This represents the only recorded archaeological lithic blade recovered from southwest Madagascar. The blade was recovered in situ at a depth of 1.66 m, a deposit dating to between 750 and 1200 BP at site G134, adjacent to the modern village of Antsaragnasoa. While similar in material choice (translucent-brown chert) and morphology (parallel-sided blade) to other lithics recovered at the northern sites of Ambohiposa and Lakaton'i Anja, it is significantly larger than other recorded lithics on Madagascar. More research is required but this finding suggests that lithic technology may have been more widespread on the island, particularly among coastal communities, than previously thought. [ABSTRACT FROM AUTHOR]

The construction of the China-Myanmar Economic Corridor (CMEC) out of Ruili and the China-Myanmar Indian Ocean New Corridor (CMIONC) out of Qingshuihe in Mengding has attracted much attention. The great contrast between the construction and development of the CMEC and the CMIONC has raised widespread concern in the academic community. Therefore, we developed a theory and framework of international corridor analysis based on the SWOT (Strengths, Weaknesses, Opportunities, and Threats), and conducted a comparative analysis of SWOT elements and key influencing factors between the CMEC and CMIONC (Ruili-Lashu and Mengding-Qingshuihe-Lashu) to reveal the differences between them and the key influencing factors of the CMIONC. We evaluated the comparative advantages of the CMEC and CMIONC and the geographic logic of focusing on various choices at different times. The study produced several important results: (1) There are significant differences in the key factors influencing the construction of the China-Myanmar Indian Ocean Corridor in different spatial and temporal sequences. The key influencing factors in the historical domain have obvious geographic determinism, and the natural geographic environment and features represented by topography, elevation, rivers, geology, among others., profoundly influenced the construction of the China-Myanmar corridor in the early period. The key influencing factors in the actual domain are mostly the degree of human initiative and the degree of scientific and technological progress contributing to the construction of the corridor and the extent to which the corridor will be constructed. Whether the progress of science and technology can contribute to the "space-time compression" of the corridor construction is to be determined. Whether the subjective initiative and progress of science and technology can shorten the construction distance of the corridor and the construction period of key sections and whether it can enhance the degree of connection with the urban agglomerations and improve the transport network system should be analyzed. Furthermore, the key influencing factors in the future domain will be the growth and national discourse support of the corridor. These aspects include strategic positioning and long-term mechanisms to serve the country, the most direct national positioning of the channel, empowerment, and discourse policy support, and others. (2) Ruili and Qingshuihe of Mengding, as the Chinese exit ports of the China-Myanmar Indian Ocean Corridor, have focused on different geographic considerations at different times and have been subject to the influences and constraints of the dominant SWOT elements. Ruili (the "herringbone" corridor) is a type of resistance strategy adjustment, and the Mengding Qingshui River (new corridor) is a type of resistance strategy aggressiveness. (3) On the whole, the advantages and potentials of the line from the Mengding Qingshuihe River to Laxun (the new corridor) are more evident than those of the line from Ruili to Laxun ("herringbone" corridor), and the obstacles and difficulties are relatively small, which proves that the advantages are in Meng for the new corridor program. The "herringbone" corridor and the new corridor have prominent complementary characteristics, highlighting the scientific soundness and feasibility of the double "Y" axis corridor concept. [ABSTRACT FROM AUTHOR]

In the era of globalized geo-economics, international big channel are changing the way geo-economic elements flow across borders, expanding cooperation spaces such as ports and border-free trade zones to more distant inland areas and shaping new ways of cross-border geo-economic cooperation. As an international land and sea channel connecting China and Myanmar, the China-Myanmar Indian Ocean New Channel (hereinafter "the Channel") is of great importance for promoting geo-economic cooperation between the two countries and the construction of the Belt and Road Initiative. However, owing to various obstacles in geo-economic cooperation, the geo-economic effect of the Channel has not been effectively brought into play. In this study, the obstacles to geo-economic cooperation in the Channel and its collaborative mechanisms were analyzed to provide important scientific and technological support for enhancing its geo-economic effects and strengthening geo-economic cooperation between China and Myanmar. The natural geography of the region with its high mountains and deep valleys and the frequently occurring natural disasters are natural obstacles that limit the geo-economic effect of the Channel. Moreover, the difference in economic development between China and Myanmar is not conducive to the deepening of geo-economic cooperation in the Channel. Complex armed conflicts have disrupted the construction of the Channel and China's investment in its route, and the potential intervention of India and the United States will become an added constraint on its further development. Furthermore, the multiple stakeholders game in the construction of the Channel may bring geo-risks. Contrary to preconceived notions, geo-economic cooperation in the Channel is not a strategy for regional control, but rather to create an international trade corridor deeply related to transportation logistics, supply chains, industrial chains and value chains. To promote geo-economic cooperation in the Channel, its construction should be based on a multi-level collaborative mechanism for geo-economic cooperation. At the national level, the docking of development strategies between China and Myanmar should be strengthened by promoting integration of the Channel into the Belt and Road Initiative, strengthening the docking of China-Myanmar policy communication mechanisms, and formulating a long-term development strategy plan for the Channel. At the channel level, the geo-economic effect of the Channel should be upgraded by promoting the linkage of internal and external infrastructures, strengthening geo-economic element cross-border flow and industrial cooperation, and deepening economic and trade cooperation with Myanmar and the Indian Ocean region. At the stakeholder level, a consultation mechanism involving multi-stakeholder participation should be established by strengthening the docking of multi-stakeholder interests, coordinating the mechanism of China-Myanmar port docking, and creating a three-dimensional risk prevention mechanism for the Channel. [ABSTRACT FROM AUTHOR]

In 2017, Ali Zamir's acclaimed debut novel Anguille sous roche became the first Comorian novel to circulate in translation in Europe. This article discusses its English translation, A Girl Called Eel, by Aneesa Abbas Higgins (2019) in relation to the reception, circulation, and canon formation of literature from the Comoros islands. By discussing translation's ties to heritage conservation and literary consecration in the Comorian context alongside a comparative textual and paratextual analysis of Anguille and Eel, I investigate the extent to which the novel's 'Comorianness' was erased, reclaimed, or playfully constructed along this translation journey by a wide variety of actors. These include the independent publishers Le Tripode and Jacaranda Books, who respectively published the French and English texts, various French literary institutions and French and UK-based funding bodies, as well as the author and translator themselves. [ABSTRACT FROM AUTHOR]

The Ninety East Ridge in the Indian Ocean has complex and unique characteristics. The concentrations and distribution characteristics of 10 trace metals (V, Cr, Mn, Fe, Co, Ni, Cu, Cd, Pb, and U) in seawater from the Ninety East Ridge in the Indian Ocean were investigated. Results show that the average concentrations of different trace metals in all the collected seawater samples were 1.134 µg/L for V, 0.158 µg/L for Cr, 0.489 µg/L for Mn, 0.427 µg/L for Fe, 0.011 µg/L for Co, 0.395 µg/L for Ni, 0.403 µg/L for Cu, 0.097 µg/L for Cd, 0.139 µg/L for Pb, and 3.470 µg/L for U. Differences in the horizontal and vertical distributions of all measured trace metals were revealed, and the occurrence of high concentrations was nonuniform. In addition, the significant differences in the concentration distribution of different trace metals in seawater on both sides of the Ninety East Ridge present regional segmentation in the area for various trace metals in deep sea water. This study provided basic data for future investigations on the environmental and ecological impact of trace metals in the Indian Ocean and the potential water mass transport mechanism. [ABSTRACT FROM AUTHOR]

A detailed morphological investigation, including osteological anatomy based on micro-CT scans, of two poorly known monotypic genera and species of gobiesocids, Lissonanchus lusherae Smith 1966 and Briggsia hastingsi Craig and Randall 2009, revealed that no generic-level differences existed between the two species. Briggsia Craig and Randall 2009, therefore, is a junior synonym of Lissonanchus Smith 1966. Lissonanchus is rediagnosed, having the following characters: 30 or 31 vertebrae; cephalic lateral-line canal pores poorly developed, including 2 nasal, 2 lacrimal and 1 postorbital canal pores; posterodorsal portion of anguloarticular strongly expanded laterally with bifurcated process; gill membranes on each side united ventrally, attached to the isthmus; 4th gill arch without filaments; double type adhesive disc; flattened papillae on disc region A continuous across center; flattened papillae on disc region D arranged along disc edge and continuous with papillae on disc region A; center of anterior disc (= middle area between disc regions A and D) lacking papillae; small fleshy pad on lower part of pectoral-fin base; anterior part of dorsal-fin base lacking a swollen fleshy appearance; general fresh coloration, including brownish-green body, dark brown strip extending from snout tip to posteroventral part of head through eye, and whitish part on lateroventral surface of head (bordered by dark brown strip). In particular, the anguloarticular feature of Lissonanchus is likely unique within the Gobiesocidae and is regarded as a putative autapomorphy for the genus. In contrast, the two species could be distinguished from each other by species-level differences, including counts of pectoral-fin rays, number of teeth on pharyngobranchial 3, jaw lengths, and streak patterns on the body. Accordingly, Lissonanchus is now considered to include two valid species: L. lusherae (type species) and Lissonanchus hastingsi, new combination. Although Lissonanchus was previously included in the subfamily Diademichthyinae, the genus does not share any diagnostic features of that subfamily, and the subfamilial assignment of the genus remains equivocal, like other Indo-Pacific genera considered as incertae sedis within the Gobiesocidae (e.g., Aspasmogaster Waite 1907, Conidens Briggs 1955, and Creocele Briggs 1955). [ABSTRACT FROM AUTHOR]

This article connects the political science literature on small states and the historical coverage of trade in the Indian Ocean to identify a remarkable pattern in foreign relations management of Maldivian geopolitics. The long history of interaction with foreign powers since at least the fifteenth century shows how this small state has, historically as well as now vis-à-vis India, China and the Middle East, managed well to retain control and sovereignty as an independent nation. Rich experience in handling the challenges posed by competing geopolitical interests in the wider region partly explains this Maldivian success story. However, this article also brings out the role of constant internal political rivalry within the Maldivian elites. The resulting highly dynamic intersecting pattern identifies how different parties, fractions and certain strong personalities as competing stakeholders constantly attempt to retain or grab power through strategic alliances with foreign powers. Identifying this underlying pattern allows deeper analysis of the unique, literally liquid characteristics of Maldivian geopolitics and similar small-state scenarios. [ABSTRACT FROM AUTHOR]

Marine nutrients underpin productivity and functioning of oceanic island ecosystems. On islands where they nest, seabirds represent a primary source of marine nutrients. In tropical regions, some of the largest seabird populations nest on atolls, yet there is limited information available on seabird contributions to atoll ecosystem nutrient dynamics. To investigate the spatial and seasonal dynamics of seabird contributions, we assessed seabird colonies of different taxa, including red‐footed boobies and terns, nesting on separate islands of Farquhar Atoll, Seychelles. We assessed nutrient concentrations of guano, soil, coastal plants, and nearby seagrass in seabird colonies and at a control island with no seabirds, during the wet and dry seasons. Sooty terns contributed the highest quantities of nutrients, estimated at 71.2 N tonne/year and 52.2 P tonne/year. Seabird‐derived nutrient transfer occurred year‐round from seabird colonies to soil, coastal plants and seagrass. Soil macro‐ and inorganic nutrients were higher in the high‐density tern colony and during the dry season, coinciding with the breeding period of sooty terns. Both red‐footed booby and tern colonies maintained high nitrogen levels in coastal plants year‐round, while phosphorus levels did not differ between islands or seasons. Seabird‐derived nitrogen reversed nitrogen limitation of seagrass during the dry season. We provide the first insights into seabird nutrient contributions to atoll ecosystems in Seychelles, with recommendations for seabird conservation to boost and support atoll and island ecosystem resilience. Our results from a relatively undisturbed atoll serve as a baseline with which more impacted atolls and future changes can be assessed. [ABSTRACT FROM AUTHOR]

The mosquito Anopheles gambiae s.s. is a primary malaria vector throughout sub-Saharan Africa including the islands of the Comoros archipelago (Anjouan, Grande Comore, Mayotte and Mohéli). These islands are located at the northern end of the Mozambique Channel in eastern Africa. Previous studies have shown a relatively high degree of genetic isolation between the Comoros islands and mainland populations of A. gambiae, but the origin of the island populations remains unclear. Here, we analyzed phylogenetic relationships among island and mainland populations using complete mitochondrial genome sequences of individual A. gambiae specimens. This work augments earlier studies based on analysis of the nuclear genome. We investigated the source population of A. gambiae for each island, estimated the number of introductions, when they occurred and explored evidence for contemporary gene flow between island and mainland populations. These studies are relevant to understanding historical patterns in the dispersal of this important malaria vector and provide information critical to assessing their potential for the exploration of genetic-based vector control methods to eliminate this disease. Phylogenetic analysis and haplotype networks were constructed from mitogenome sequences of 258 A. gambiae from the four islands. In addition, 112 individuals from seven countries across sub-Saharan Africa and Madagascar were included to identify potential source populations. Our results suggest that introduction events of A. gambiae into the Comoros archipelago were rare and recent events and support earlier claims that gene flow between the mainland and these islands is limited. This study is concordant with earlier work suggesting the suitability of these oceanic islands as appropriate sites for conducting field trial releases of genetically engineered mosquitoes (GEMs).

Plastic pollution is distributed patchily around the worlds oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation. Oceanic seabirds, particularly petrels, frequently ingest plastic, are highly threatened, and cover vast distances during foraging and migration. However, the spatial overlap between petrels and plastics is poorly understood. Here we combine marine plastic density estimates with individual movement data for 7137 birds of 77 petrel species to estimate relative exposure risk. We identify high exposure risk areas in the Mediterranean and Black seas, and the northeast Pacific, northwest Pacific, South Atlantic and southwest Indian oceans. Plastic exposure risk varies greatly among species and populations, and between breeding and non-breeding seasons. Exposure risk is disproportionately high for Threatened species. Outside the Mediterranean and Black seas, exposure risk is highest in the high seas and Exclusive Economic Zones (EEZs) of the USA, Japan, and the UK. Birds generally had higher plastic exposure risk outside the EEZ of the country where they breed. We identify conservation and research priorities, and highlight that international collaboration is key to addressing the impacts of marine plastic on wide-ranging species.

Abstract We studied chromophoric (CDOM) and fluorescent (FDOM) dissolved organic matter (DOM) and dissolved organic carbon in surface waters to determine the factors controlling the geographical distribution of DOM along two meridional transects in the Indian Ocean. For CDOM, we calculated the absorption coefficients, spectral slope, and absorption coefficient ratio from the observed absorption spectra. For FDOM, we calculated the biological (BIX) and humification (HIX) indices from the excitation emission matrices (EEMs); parallel factor analysis of the EEMs identified three fluorescent components, i.e., two humic-like and one protein-like. Using these DOM parameters, a factor analysis extracted fewer latent variables than the observed variables to account for the geographical distributions. We obtained three factors (F1, F2, and F3), which explained ~ 84% of the variance in the observed data. From the factor loadings, F1, F2, and F3 were interpreted as the effects of net primary production-derived DOM and its horizontal transport, photodegradation, and vertical transport by physical processes. We characterized seven marine biogeochemical provinces by factor scores. F1 scores gradually decreased from the northernmost to the Antarctic province, with a small maximum around the subtropical front. F2 scores were highest in the subtropical province and decreased in both the northward and southward directions. F3 scores were high in the Antarctic and northernmost provinces, and lowest in the subtropical province. Only BIX was insufficiently explained by these factors. BIX was highest in the northern part of the subtropical province, where photodegradation of DOM was the most intense. This suggests that the possible interaction between photodegradation, autochthonous production, and reworking by heterotrophic bacteria of DOM occurs in the subtropical province.

Abstract The Regional Indian Ocean model based on Modular Ocean Model (MOM4p1) was used to understand the importance of a realistic representation of bathymetry on Ocean General Circulation. The model has 1/4° uniform horizontal resolution and is forced with Coordinated Ocean-Ice Reference Experiments (CORE-II) inter-annual forcing with two simulations named BLND (realistic bathymetry) and OM3 (smoothed bathymetry), which only differ in the representation of bathymetry for the years 1992–2005. We also used recent reanalysis products from ORAS5 and SODA3 and ADCP observation to compare the subsurface currents. We show that by the inclusion of realistic bathymetry, there is a significant improvement in the upper ocean salinity, temperature, and currents, particularly near the coast. The salinity and temperature of the upper ocean are very close to the observed value near the coast. The bias in the salinity and temperature was reduced to half in BLND simulation compared to OM3, which led to a more realistic East India Coastal Current (EICC). We show the first evidence of a basin-wide cyclonic gyre over the Bay of Bengal at 1000 m depth during spring, which is just opposite to that of a basin-wide anti-cyclonic gyre at the surface. We found the presence of poleward EICC during spring at 1000 m and 2000 m depth, which is opposite to that of the surface. The presence of this deeper EICC structure is completely absent during fall. We show the presence of a boundary current along the coast of Andaman and Nicobar Island at a depth of 2000 m. The observed Wyrtki Jet (WJ) magnitude and spatial structure are most realistically reproduced in BLND simulation as compared to OM3 simulations. Both ORAS5 and SODA reanalysis products underestimate the WJ magnitude. The presence of the Maldives Islands is responsible for the westward extent of Equatorial Under Current (EUC). The presence of Maldives also creates wakes on the leeward side in the EUC zonal current. During fall, EUC is better defined in the eastern Equatorial Indian Ocean and lies at a depth of between 50 and 100 m, unlike its spring counterpart, in which its core is located slightly deeper, between 100 and 150 m depth. During peak summer months, June–July, a strong eastward zonal jet is present at 1000 m depth, similar to Wyrtki Jet (WJ). Inter-monsoon Jets, i.e., spring and fall jets, are also seen but are in the opposite direction, i.e., westward, unlike eastward in WJ.

This article examines the complex interplay between heritage, cultural identity, and state power, as exemplified by the contested heritage discourse surrounding a sea temple and the Chinese cult of Guandi in Mauritius. The main temple of Guandi in Mauritius abound in aquatic and oceanic manifestations, which stand in sharp contrast with state-endorsed, land-based Guandi temples in China. This contrast suggests a distinct cultural identity of the Chinese society in the Southwest Indian Ocean region. As reflected in the narratives of both Mauritian and Chinese authorities, the temple and cult also figure prominently in the re-imagining of Mauritian nation building and China's Maritime Silk Road Initiative. Drawing on critical heritage studies and the revitalised academic focus on sea temples that revisits the overlooked maritime connectivity, this article demonstrates how a historically-forged transoceanic identity in the name of Guandi is being contested by the new processes of heritagisation initiated by the Mauritian and Chinese states and how appreciation of the maritime heritage of Chinese diaspora in the Indian Ocean can re-emerge when the interpretation of the cult shifts from its role as one component of Mauritian and Chinese national heritage to its unorthodox oceanic reinvention. [ABSTRACT FROM AUTHOR]

This paper calls for a maritime turn in critical heritage theory. Drawing on recent work on ocean and maritime ontologies, it takes up the idea of the 'ocean in excess' to argue for a maritime imagination that overcomes the separation of land from water, culture from nature. The paper begins by sketching out the terracentric norms that have come to underpin critical theory around cultural heritage. From there, recent insights on ocean ontologies are cited to show how they can open up new ways of thinking about existing strands of critical heritage work. The second half of the paper turns to the issue of ocean governance and the complex politics that arise from competing ontologies. This provides the foundation for a discussion of the transoceanic heritage discourses that are now emerging, as countries seek regional, come global influence in world affairs. Understanding these and other developments requires moving beyond the earthly, such that we more robustly engage with a multivalent heritage politics that operates across air, water and land. [ABSTRACT FROM AUTHOR]

This article explores the historical trade relationships between American, Indian, and Zanzibari merchants in the 19th century. American merchants recognized the commercial potential of Zanzibar and formed close ties with Indian businessmen, such as Jairam Shivji, to establish a mutually beneficial trade system. Zanzibar served as a gateway for American ventures across the Western Indian Ocean. The article emphasizes the significance of Indian commercial networks and the complexities of cross-cultural trade. It also discusses the theoretical frameworks of trade networks and circulation societies in understanding these interactions. The text further delves into the relationship between American traders and Indian merchants in the Indian Ocean region, the challenges faced in establishing commercial relationships on Zanzibar, and the role of the Omani Empire. It also highlights the development of bilingual commodity contracts and the expansion of American trade to other ports, including Bombay. Despite obstacles, the close relationship between American and Indian merchants remained crucial in facilitating trade in the Western Indian Ocean. [Extracted from the article]

This study examines the track and intensity forecasts of two typical Bay of Bengal tropical cyclones (TC) ASANI and MOCHA. The analysis of various Numerical Weather Prediction (NWP) model forecasts [ECMWF (European Centre for Medium range Weather Forecast), NCEP (National Centers for Environmental Prediction), NCUM (National Centre for Medium Range Weather Forecast-Unified Model), IMD (India Meteorological Department), HWRF (Hurricane Weather Research and Forecasting)], MME (Multi-model Ensemble), SCIP (Statistical Cyclone Intensity Prediction) model, and OFCL (Official) forecasts shows that intensity forecasts of ASANI and track forecasts of MOCHA were reasonably good, but there were large errors and wide variation in track forecasts of ASANI and in intensity forecasts of MOCHA. Among all model forecasts, the track forecast errors of IMD model and MME were least in general for ASANI and MOCHA respectively. Also, the landfall point forecast errors of IMD were least for ASANI, and the MME and OFCL forecast errors were least for MOCHA. No model is found to be consistently better for landfall time forecast for ASANI, and the errors of ECMWF, IMD and HWRF were least and of same order for MOCHA. The intensity forecast errors of OFCL and SCIP were least for ASANI, and the forecast errors of HWRF, IMD, NCEP, SCIP and OFCL were comparable and least for MOCHA up to 48 h forecast and HWRF errors were least thereafter in general. The ECMWF model forecast errors for intensity were found to be highest for both the TCs. The results also show that although there is significant improvement of track forecasts and limited or no improvement of intensity forecast in previous decades but challenges still persists in real time forecasting of both track and intensity due to wide variation and inconsistency of model forecasts for different TC cases. [ABSTRACT FROM AUTHOR]

The time-varying September-November relationship between the Indian Ocean Dipole (IOD) and Central African (CA) rainfall has strengthened since the 1990s, implying an increasing IOD influence over CA rainfall. Using observational and reanalysis datasets covering the 1980–2016 period, this study examines the CA circulation response associated with the Indian Ocean dynamics during the September-December IOD events, since this circulation constitutes a key moisture transport feature for CA rainfall variability. The results show that during positive IOD events (pIOD), the moisture transport drivers over CA and the Indian Ocean (IO) are synchronous, leading to an increase in CA rainfall, whereas the reverse pattern is observed during negative IOD events (nIOD). The equatorial easterly (westerly) moisture transport driven by the anticyclonic (cyclonic) circulation in the northern tropical IO and the weakening (intensification) of the African Easterly Jet's northern component (AEJ-N), leads to an increase (decrease) in CA rainfall during pIOD (nIOD). Warm (cold) SST anomalies in the eastern Indian Ocean during nIOD (pIOD) event, intensify (weaken) the large-scale upward motion, strengthening (weakening) the cyclonic circulation in the mid-troposphere, thus favoring a significant westerly (easterly) circulation. The AEJ-N weakening during pIOD events is associated with a strengthening of the meridional pressure gradient and a westward shift in the Saharan high location at the AEJ-N's northern edge. The results also reveal a significant influence of the Atlantic during pIOD events, induced by its teleconnection with the IO, whose effects are more modulated by the IOD's western pole warming than by the IOD-related SST gradient. [ABSTRACT FROM AUTHOR]

This article critically reviews four decades of development of maritime and underwater archaeology in India (MUAI). Established in 1981, the first Marine Archaeology Centre at the Council of Scientific and Industrial Research—National Institute of Oceanography in Goa, India, has conducted a series of maritime and underwater investigations. The country has also attracted international collaborations mainly focused on maritime ethnographic studies. As such, the discipline has seen steady growth, but its progress unfortunately remains slow and is struggling to keep pace with the developments happening within the discipline globally. A significant setback was in 2015 when the Underwater Archaeology Wing (UAW) of the Archaeological Survey of India was defunct. Furthermore, India is not a signatory to the 2001 UNESCO Convention on the Protection of the Underwater Cultural Heritage. This raises the question—what does the future hold for the MUAI? The government's plan to establish the country's first National Maritime Museum to display maritime past and its intention to revive the UAW to boost research indicates some optimism towards the survival of the field. Nonetheless, there exists gaps in research approaches and methodologies adopted so far and problems and challenges faced by the discipline that are hindering its growth. Along with discussing the aforementioned issues, this paper concludes with prospects for the future of MUAI. [ABSTRACT FROM AUTHOR]

Background: During the 2022 Nekton Maldives Mission, we deployed a variety of platforms (snorkelling, remotely-operated vehicles and manned submersibles) to conduct video surveys of the biodiversity and composition of shallow (< 30 m), mesophotic (30-150 m) and deep-sea (> 150 m) benthos found in the Maldives' central and southern atolls. In total, ~ 80 hrs of stereo-video footage were collected during the benthic transect surveys, which were subsequently processed using annotation software in order to evaluate benthic biodiversity and community composition. Here, we present a photographic guide for the visual, in situ identification of reef benthos encountered, including corals, sponges and other invertebrates that inhabit Maldives' nearshore habitats. We hope that this identification guide will aid future imagery-based surveys or observations of organisms during fieldwork. New information: A total of 283 morphotypes were identified, including those belonging to Octocorallia (61), Scleractinia (57), Porifera (38), Asteroidea (22), Antipatharia (15), Decapoda (13), Hydrozoa (12), Holothuroidea (10), Actiniaria (9), Echinoidea (8), Annelida (6), Chlorophyta (5), Gastropoda (4), Bivalvia (4), Ascidiacea (3), Crinoidea (3), Bryozoa (2), Cyanobacteria (2), Zoantharia (2), Cephalopoda (1), Ceriantharia (1), Corallimorpharia (1), Ctenophora (1), Ophiuroidea (1), Rhodophyta (1) and to an unknown category (1). Out of these, we identified 40 to species level, 120 to genus, 47 to family, 14 to order and suborder, 58 to class and subclass, two to phylum and one was of unknown phylum. This represents the first attempt to catalogue the mesophotic and deep-sea benthic megafaunal diversity in the Maldives using underwater imagery. [ABSTRACT FROM AUTHOR]