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Tropical ecosystems sustain higher biodiversity and face faster species extinction. However, baseline information of these areas is either inadequate or scattered due to various reasons. The 2,360 km long coast of North West India (NWI), is a heavily industrialized and urbanized zone. This coast with unique biogeographical and climatic features with two notified marine protected areas also supports rich biodiversity. This review was motivated by a need to construct a synoptic view on marine benthic ecology and functioning by consolidating available information of macrobenthos. Two thousand seventy-eight macrobenthic taxa belonging to 14 phyla were compiled from 147 references and were composed mostly by Polychaeta (n = 617), Gastropoda (n = 602), and Bivalvia (n = 216). Habitat wise, intertidal and subtidal zones were more intensely studied and contributed most to the diversity records. Sediment texture and salinity were the major drivers of macrobenthic community structure in the subtidal areas and estuaries, respectively. In the intertidal zones, zonation patterns related to the tidal levels and time of exposure were distinct with the high water zones being sparsely populated and lower intertidal zones sustaining higher species and functional diversities. All zones of NWI coast were distinctly impacted to various extent by anthropogenic activities affecting the resident macrobenthos. Decline in species richness and species substitution due to pollution were reported in urbanized zones. Non-monsoonal months favored a more conducive environment for the macrobenthic diversity and functionality. Hypoxia tolerant polychaete species mainly belonging to Spionidae and Cossuridae dominated during the low oxygen conditions of upwelling and OMZ zones of NWI. Inadequate identification and inconsistency of sampling methods were major deterrents for concluding trends of distributions. Suggestions for future macrobenthic research include focusing on lesser studied groups and are

Marine soft-sediments sustain functionally important benthic assemblages that are critical for remineralization of organic matter and supply of nutrients to the water column. While these assemblages are well studied along continental margins, investigations from insular margin that surround oceanic islands are very limited. This paper examines the distribution and standing stock of macrozoobenthos at 50, 100, and 200 m depth contours surrounding the Andaman and Nicobar archipelago in the tropical Indian Ocean. The standing stock of macrozoobenthos decreased from the mesophotic reef areas (50 m depth) to the deeper strata (200 m), particularly in the case of the dominant groups, the polychaetes and crustaceans. Smaller-sized, interstitial polychaetes and crustaceans were abundant in the coarser sandy sediments at the shallower sites. The polychaetes were represented by 606 species (279 genera) in the study, of which >50% were rare species. Based on polychaete species composition, three regions were delineated in the study area - the Nicobar margin, the western margin of the Andaman (Bay of Bengal sector), and the eastern margin of the Andaman (Andaman Sea sector). The long, uninterrupted Andaman Island chain formed a geographic barrier separating the eastern and western margins, resulting in the regional distinctions in sediment nature and hydrographic characteristics, which in turn influenced species distribution. Corresponding differences were absent in the case of the Nicobar Islands, which are widely separated by transecting channels, permitting exchange of water between the Bay of Bengal and the Andaman Sea. Within the three regions, polychaete communities changed significantly in taxonomic and functional composition with increasing depth. The well oxygenated, coarse sandy sediments around mesophotic reefs (50 m) harbored predator-dominated assemblages. The 200 m sites, which were characterized by oxygen minimum conditions (<0.5 ml.l-1), particularly around th

The aim of this study was to document the composition and distribution of deep-water fishes associated with a submarine canyon-valley feature. A work-class Remotely Operated Vehicle (ROV) fitted with stereo-video cameras was used to record fish abundance and assemblage composition along transects at water depths between 300 and 900 metres. Three areas (A, B, C) were sampled along a submarine canyon-valley feature on the continental slope of tropical north-western Australia. Water conductivity/salinity, temperature, and depth were also collected using an ROV mounted Conductivity Temperature and Depth (CTD) instrument. Multivariate analyses were used to investigate fish assemblage composition, and species distribution models were fitted using boosted regression trees. These models were used to generate predictive maps of the occurrence of four abundant taxa over the survey areas. CTD data identified three water masses, tropical surface water, South Indian Central Water (centred ∼200 m depth), and a lower salinity Antarctic Intermediate Water (AAIW) ∼550 m depth. Distinct fish assemblages were found among areas and between canyon-valley and non-canyon habitats. The canyon-valley habitats supported more fish and taxa than non-canyon habitats. The fish assemblages of the deeper location (∼700-900 m, Area A) were different to that of the shallower locations (∼400-700 m, Areas B and C). Deep-water habitats were characterised by a Paraliparis (snail fish) species, while shallower habitats were characterised by the family Macrouridae (rat tails). Species distribution models highlighted the fine-scale environmental niche associations of the four most abundant taxa. The survey area had a high diversity of fish taxa and was dominated by the family Macrouridae. The deepest habitat had a different fish fauna to the shallower areas. This faunal break can be attributed to the influence of AAIW. ROVs provide a platform on which multiple instruments can be mounted and com

* Construction of Asset Wealth Index for Tanzanian Small-Scale Fisheries based on a Multiple Correspondence Approach. * Less wealthy fishers target fewer species and are less able to absorb changes in management measures such as closures. * Wealthier fishers with high adaptive capacity are able to better absorb the short-term losses of fisheries closures.

Tropical shallow-water habitats represent the marine environments with the greatest biodiversity; however, these habitats are the most vulnerable to climate warming. Corals, seagrasses, and macroalgae play a crucial role in the structure, functions, and processes of the coastal ecosystems. Understanding their growth and physiological responses to elevated temperature and interspecific sensitivity is a necessary step to predict the fate of future coastal community. Six species representatives, including Pocillopora acuta, Porites lutea, Halophila ovalis, Thalassia hemprichii, Padina boryana, and Ulva intestinalis, collected from Phuket, Thailand, were subjected to stress manipulation for 5 days. Corals were tested at 27, 29.5, 32, and 34.5°C, while seagrasses and macroalgae were tested at 27, 32, 37, and 42°C. After the stress period, the species were allowed to recover for 5 days at 27°C for corals and 32°C for seagrasses and macroalgae. Non-destructive evaluation of photosynthetic parameters (Fv/Fm, Fv/F0, ϕPSII and rapid light curves) was carried out on days 0, 3, 5, 6, 8, and 10. Chlorophyll contents and growth rates were quantified at the end of stress, and recovery periods. An integrated biomarker response (IBR) approach was adopted to integrate the candidate responses (Fv/Fm, chlorophyll content, and growth rate) and quantify the overall temperature effects. Elevated temperatures were found to affect photosynthesis, chlorophyll content, and growth rates of all species. Lethal effects were detected at 34.5°C in corals, whereas adverse but recoverable effects were detected at 32°C. Seagrasses and macroalgae displayed a rapid decline in photosynthesis and lethal effects at 42°C. In some species, sublethal stress manifested as slower growth and lower chlorophyll content at 37°C, while photosynthesis remained unaffected. Among all, T. hemprichii displayed the highest thermotolerance. IBR provided evidence that elevated temperature affected the overall perf

Detailed ocean currents in the southeastern tropical Indian Ocean adjacent to southern Sumatran and Javan coasts have not been fully explained because of limited observations. In this study, zonal current characteristics in the region have been studied using simulation results of a 1/8∘ global hybrid coordinate ocean model from 1950 to 2013. The simulated zonal currents across three meridional sections were then investigated using an empirical orthogonal function (EOF), where the first three modes account for 75 %-98 % of the total variance. The first temporal mode of EOF is then investigated using ensemble empirical mode decomposition (EEMD) to distinguish the signals. This study has revealed distinctive features of currents in the South Java Current (SJC) region, the Indonesian Throughflow (ITF)-South Equatorial Current (SEC) region, and the transition zone between these regions. The vertical structures of zonal currents in southern Java and offshore Sumatra are characterized by a one-layer flow. Conversely, a two-layer flow is observed in the nearshore and transition regions of Sumatra. Current variation in the SJC region has peak energies that are sequentially dominated by semiannual, intraseasonal, and annual timescales. Meanwhile, the transition zone is characterized by semiannual and intraseasonal periods with pronounced interannual variations. In contrast, interannual variability associated with El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) modulates the prominent intraseasonal variability of current in the ITF-SEC region. ENSO has the strongest influence at the outflow ITF, while the IOD's strongest influence is in southwestern Sumatra, with the ENSO (IOD) leading the current by 4 months (1 month). Moreover, the contributions (largest to smallest) of each EEMD mode at the nearshore of Java and offshore Sumatra are intraseasonal, semiannual, annual, interannual, and long-term fluctuations. The contribution of long-term

According to the latest report on the state of World Food and Agriculture Organization fisheries and aquaculture (SOFIA, 2022), skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) are among the five most caught finfish species of the world, with 2,827 and 1,569 thousand tons in 2020, respectively. The tropical purse seiners deploy large nets around tuna schools in the tropical waters of the world. This method targets three main tuna species, skipjack, yellowfin and bigeye (Thunnus obesus) tunas, which are mainly used for canning or frozen markets. This important fishery provides employment opportunities for many people in developing countries. Landings for the European long-distance fishery targeting tuna and tuna-like fishes from Indian Ocean, amounted to 303,638 tons valued at EUR 423.7 million (Prellezo et al., 2022), where the Spanish fleet of purse seiners targeting tropical tuna is the most important. The Spanish tropical purse seine fleet fishing in the Indian Ocean accounts for 26% of the skipjack and yellowfin tunas caught from Indian Ocean, which represent approximately 3% of worldwide catch for both species.

Tropical regions experience a diverse range of dense clouds, posing challenges for the daily reconstruction of chlorophyll-a concentration data. This underscores the pressing need for a practical method to reconstruct daily-scale chlorophyll-a concentrations in such regions. While traditional data reconstruction methods focus on single variables and rely on specific factors to infer missing data at specific locations, these single-variable methods may falter when applied to tropical oceans due to the scarcity of available data. Fortunately, all oceanographic variables undergo similar atmospheric and marine dynamic processes, creating internal relationships between them. This allows for the reconstruction of missing data through correlations between variables. Thus, this study introduces a multivariate reconstruction approach using the extended data interpolating empirical orthogonal function (ExDINEOF) method to reconstruct missing daily-scale chlorophyll-a concentration data. The ExDINEOF method considers the simultaneous relationships among multiple variables for data reconstruction in tropical oceans. To verify the method's robustness, missing data were reconstructed during the formation and passage of severe tropical cyclone Hudhud through the Bay of Bengal. The results demonstrate that ExDINEOF outperforms traditional data reconstruction methods, exhibiting favorable spatial distribution and enhanced accuracy within the dynamic tropical marine environment. Furthermore, an assessment of marine physical environmental factors associated with chlorophyll-a concentration data provides additional evidence for the ExDINEOF method's accuracy. Notably, the ExDINEOF method offers comprehensive spatial distribution aligned with underlying physical mechanisms governing phytoplankton distribution patterns, detailed phytoplankton growth, bloom, extinction variations in time series, satisfactory accuracy, and comprehensive local-level details.

The seasonality of mesoscale eddy intensity in the southeastern tropical Indian Ocean (SETIO) is investigated using the latest eddy dataset and marine hydrological reanalysis data. The results show that the eddy intensity in an area to the southwest coast of the Java Island has prominent seasonality-eddies in this area are relatively weak during the first half of the year but tend to enhance in August and peak in October. Further analysis reveals that the strong eddies in October are actually developed from the ones mainly formed in July to September, and the barotropic instability and baroclinic instability are the key dynamics for eddy development, but each plays a different role at different development stages. The barotropic instability resulting from the horizontal shear of surface current plays an important role in the early stage of eddy development. However, in the late development stage, the baroclinic instability induced by the sloping pycnocline becomes the major energy contributor of eddy development.

New research highlights both natural climate variability, warming temperatures.

Most climate forecast agencies failed to make successful predictions of the strong 2020/2021 La Niña event before May 2020. The western equatorial Pacific warm water volume (WWV) before the 2020 spring failed to predict this La Niña event because of the near neutral state of the equatorial Pacific Ocean in the year before. A strong Indian Ocean Dipole (IOD) event took place in the fall of 2019, which is used as a precursor for the La Niña prediction in this study. We used observational data to construct the precursory relationship between negative sea level anomalies (SLA) in the southeastern tropical Indian Ocean (SETIO) in boreal fall and negative Niño 3.4 sea surface temperature anomalies index one year later. The application of the above relation to the prediction of the 2020/2021 La Niña was a great success. The dynamics behind are the Indo-Pacific "oceanic channel" connection via the Indian Ocean Kelvin wave propagation through the Indonesian seas, with the atmospheric bridge playing a secondary role. The high predictability of La Niña across the spring barrier if a positive IOD should occur in the previous year suggests that the negative SETIO SLA in fall is a much better and longer predictor for this type of La Niña prediction than the WWV. In comparison, positive SETIO SLA lead either El Niño or La Niña by one year, suggesting uncertainty of El Niño predictions.

In the summer of 2022, like in many other regions of the world, an unprecedented period of continuous high-temperature weather occurred in eastern China. The degree and duration of this event far exceeded normal standards. Between 2020 and 2022, the tropical Pacific experienced the most significant three-year consecutive La Nina event recorded in recent decades. We investigate linkages between these events: the high-temperature response in eastern China and Asia under the background of such La Nina events. Development of summer La Nina events contributed to a high-temperature heat wave during the summer of 2022. Rapid development of these events in the third year exacerbated negative Indian Ocean Dipole phases because of energy accumulation from abnormal easterly winds. The combined effects of the negative Indian Ocean Dipole phase and La Nina provided background field support that strengthened the West Pacific Subtropical High (WPSH) and the Iranian High, leading to high terrestrial temperature anomalies. An empirical orthogonal function (EOF) analysis of the vertical velocity in the middle and low latitudes of the tropical Indian Ocean and the Asian continent reveals the first two empirical orthogonal function modes to be conducive to the strengthening of Walker circulation in 2022. These two main modes jointly reflect the rising movement of the equatorial East Indian Ocean and South China Sea in 2022, and the sinking movement to the west of the Tibet Plateau and eastern China, which was conducive to generating high temperatures in eastern China. Finally, the South Asian High was affected by the La Nina event that lasted for three years, showing a strong trend towards the north, thus making an important contribution to this high temperature.

Marine heatwaves (MHWs) are anomalously warm events that profoundly affect climate change and local ecosystem. During the summer of 2012 (June-September), intense MHWs occurred in the tropical Indian Ocean (TIO) concurrently with an unseasonable positive Indian Ocean Dipole (pIOD) event. The MHW metrics (duration, frequency, cumulative intensity and maximum intensity) were characterized by northwestward-slanted patterns from west Australia to the Somalia coast. The analysis confirmed that these MHWs were closely associated with the unseasonable pIOD 2012. The weakening of Western North Pacific Subtropical High and strengthening of Australian High in spring induced an interhemispheric pressure gradient that drove two anticyclonic circulation patterns over the eastern TIO. The first anticyclonic circulation featured cross-equatorial wind anomalies from south of Java to the South China Sea/Philippine Sea, which led to strong upwelling off Sumatra-Java during the subsequent summer. The second anticyclonic circulation excited downwelling Rossby waves that propagated from the southeastern TIO to the western TIO. Thus, downwelling in the western pole and upwelling in the eastern pole led to a strong pIOD event peaking in summer, namely, the unseasonable pIOD 2012. These downwelling Rossby waves deepened the thermocline by more than 60 m and caused anomalous surface warming, thereby contributing to the occurrences of MHWs. With the development and peak of the unseasonable pIOD 2012, anomalous atmospheric circulation transported moisture from the TIO to the subtropical Western North Pacific (WNP), favoring a strong cyclonic anomaly that profoundly affected the summer monsoon rainfall over the subtropical WNP. This study provides some perspectives on the role of pIOD events in summer climate over the Indo-Northwest Pacific region.