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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.

The monsoon circulation in the Northern Indian Ocean (NIO) is unique since it develops in response to the bi-annual reversing monsoonal winds, with the ocean currents mirroring this change through directionality and intensity. The interaction between the reversing currents and topographic features have implications for the development of the Island Mass Effect (IME) in the NIO. The IME in the NIO is characterized by areas of high chlorophyll concentrations identified through remote sensing to be located around the Maldives and Sri Lanka in the NIO. The IME around the Maldives was observed to reverse between the monsoons to downstream of the incoming monsoonal current whilst a recirculation feature known as the Sri Lanka Dome (SLD) developed off the east coast of Sri Lanka during the Southwest Monsoon (SWM). To understand the physical mechanisms underlying this monsoonal variability of the IME, a numerical model based on the Regional Ocean Modeling System (ROMS) was implemented and validated. The model was able to simulate the regional circulation and was used to investigate the three-dimensional structure of the IME around the Maldives and Sri Lanka in terms of its temperature and velocity. Results revealed that downwelling processes were prevalent along the Maldives for both monsoon periods but was applicable only to latitudes above 4°N since that was the extent of the monsoon current influence. For the Maldives, atolls located south of 4°N, were influenced by the equatorial currents. Around Sri Lanka, upwelling processes were responsible for the IME during the SWM but with strong downwelling during the NEM. In addition, there were also regional differences in intra-seasonal variability for these processes. Overall, the strength of the IME processes was closely tied to the monsoon current intensity and was found to reach its peak when the monsoon currents were at the maximum.

Iodine affects the radiative budget and the oxidative capacity of the atmosphere and is consequently involved in important climate feedbacks. A fraction of the iodine emitted by oceans ends up in aerosols, where complex halogen chemistry regulates the recycling of iodine to the gas-phase where it effectively destroys ozone. The iodine speciation and major ion composition of aerosol samples collected during four cruises in the East and West Pacific and Indian Oceans was studied to understand the influences on iodine's gas-aerosol phase recycling. A significant inverse relationship exists between iodide (I-) and iodate (IO3-) proportions in both fine and coarse mode aerosols, with a relatively constant soluble organic iodine (SOI) fraction of 19.8% (median) for fine and coarse mode samples of all cruises combined. Consistent with previous work on the Atlantic Ocean, this work further provides observational support that IO3- reduction is attributed to aerosol acidity, which is associated to smaller aerosol particles and air masses that have been influenced by anthropogenic emissions. Significant correlations are found between SOI and I-, which supports hypotheses that SOI may be a source for I-. This data contributes to a growing observational dataset on aerosol iodine speciation and provides evidence for relatively constant proportions of iodine species in unpolluted marine aerosols. Future development in our understanding of iodine speciation depends on aerosol pH measurements and unravelling the complex composition of SOI in aerosols.

The Socotra Archipelago (Yemen), a group of four islands off the north-eastern tip of Africa in the western Indian Ocean, has a population that relies heavily on small-scale fishing for livelihoods and food security. However, the reporting of fisheries catches by Yemen has consistently been incomplete, with artisanal (small-scale, commercial) catches underreported and small-scale non-commercial subsistence and recreational catches not reported at all. Here, we reconstruct the total small-scale catches and fishing effort from the waters of the Socotra Archipelago for 1950 to 2019, and derive catch-per-unit-effort (CPUE) estimates for these fisheries. The catch officially reported by the Food and Agriculture Organization on behalf of Yemen that was assumed taken from the archipelago is thought to be around 20% of the total reconstructed catch for the archipelago. The reconstructed small-scale catch increased from ~1,500 t in 1950 to an all-time peak of 12,000 t in 2000 before declining to 3,300 t by 2014. Thereafter, catches increased again slightly to just over 3,700 t·year-1 by 2019. Artisanal catches accounted for around 70% of total small-scale catches prior to 2010, but made up only around 46% by 2019. Conversely, subsistence catches increased from ~1,000 t in 2010 to ~2,000 t in 2019, and accounted for 54% of total catches by 2019. Small-scale fishing effort increased by over 1000% since 1950 and reached over 11 million kWdays by 2019. The CPUE derived for small-scale fisheries declined by 78% since 1950, from 1.4 kg·kWday-1 to 0.3 kg·kWday-1 in 2019, with most of the decline occurring after 2000. Our findings suggest resource overexploitation, and may assist efforts to more sustainably manage the Socotra Archipelago's fish stocks. Small-scale fisheries support food and nutrient security of the local population, not least during political and humanitarian crises such as in Yemen.

Recent studies suggest that pelagic sediments can enrich rare-earth elements (REE) acting as a significant reservoir for the global REE budget as well as a potential resource for future exploitation. Although Ca-phosphate (e.g., bioapatite fossils) and Fe-Mn (oxyhydr)oxides (e.g., micronodule) have been considered important REE carriers in deep-sea sediments, the proportion of REE held by each mineral phase remains enigmatic. Here, we have investigated the sediments from two promising REE-rich prospective areas: the Tiki Basin in the Southeast Pacific (TKB) and the Central Indian Ocean Basin (CIOB). The mineral grains including bioapatite fossils and Fe-Mn micronodules have been inspected individually by in-situ microscale analytical methods. Correspondently, the REE bound to Ca-phosphate and Fe-Mn (oxyhydr)oxides have been sequentially extracted and quantified. The crucial role of Ca-phosphate is substantiated by sequential leaching which reveals its dominance in hosting ~69.3-89.4% of total REE. The Fe-Mn (oxyhydr)oxides carry ~8.2% to 22.0% of REE in bulk sediments, but they account for ~70.0-80.5% of Ce owing to their preferential adsorption of Ce over the other REE. Surface sediment on modern seafloor can accumulate high REE contents resulting from the REE scavenging by the host phases within the range of sediment-seawater interface. Differences between TKB and CIOB samples indicate that the REE enrichment in the deep-sea environment may be controlled by multiple factors including the productivity of overlying seawater (e.g., phosphorus flux), water depth relative to carbonate compensation depth (CCD), sedimentation rate, redox condition, and hydrothermal vent input (e.g., Fe-Mn precipitations).

The fin whale is listed as globally vulnerable, with ongoing threats to their population, yet little is known about the distribution and movements of the Southern Hemisphere sub-species, Balaenoptera physalus quoyi. This study assesses fin whale distribution in the Southern Hemisphere analysing acoustic recordings from 15 locations in Antarctic and Australian waters from 2002 to 2019. A seasonal acoustic presence of fin whales in Antarctic waters from late austral summer to autumn (February to June) with long-term, consistent annual usage areas was identified at the Southern Kerguelen Plateau and Dumont d'Urville sites. In comparison, limited vocal presence of fin whales was observed at the Casey site. In Australian waters, fin whales were seasonally present from austral autumn to mid-spring (May to October) on east and west coasts, with a decadal pattern of acoustic presence observed at Cape Leeuwin, WA. Two migratory pathways are identified, from the Indian sector of Antarctica to the west coast of Australia and from the Pacific sector of Antarctica to the east coast of Australia. The identified seasonal distributions and migratory pathways provide valuable information to aid in monitoring the recovery of this vulnerable sub-species. We suggest the identified distribution and dispersal from the Southern Kerguelen Plateau and Dumont d'Urville sites to the west and east coasts of Australia respectively, as well as the spatial separation between Antarctic sites, provide preliminary evidence of separate sub-populations of the Southern Hemisphere sub-species of fin whale.

Seagrass meadows are prominent in many coastal zones worldwide and significant contributors to global primary production. The large bottom roughness (or canopy) created by seagrass meadows substantially alters near-bed hydrodynamics and sediment transport. In this study, we investigate how a seagrass meadow in a low-energy environment (forced by local winds) modifies near-bed mean and wave-driven flows and assess how this relates to suspended sediment concentration (SSC). A two-week field study was conducted at Garden Island in southwestern Australia, a shallow and sheltered coastal region subjected to large diurnal sea-breeze cycles, typical of many low-energy environments where seagrasses are found. The mean and turbulent flow structure, along with optical estimates of SSC, were measured within both a seagrass canopy and over an adjacent bare bed. Near-bed mean current velocities within the seagrass canopy were on average 35% of the velocity above the canopy. Oscillatory wave velocities were less attenuated than mean current velocities, with near-bed values on average being 83% of those above the canopy. Mean and maximum shear velocities inferred from currents and waves above the canopy frequently exceeded the threshold for sediment resuspension, but no significant variation was observed in the SSC. However, a significant correlation was observed between SSC and bed shear stress estimated using near-bed velocities inside the canopy. When sediment was resuspended, there were substantial differences between the SSCs within and above the canopy layer, with higher levels confined within the canopy. This study demonstrates the importance of measuring near-bed hydrodynamic processes directly within seagrass canopies for predicting the role seagrass meadows play in regulating local rates of sediment resuspension.

Molybdenum and tungsten are redox-sensitive elements, and their stable isotope ratios have attracted attention as paleoceanographic proxies. However, our knowledge of the distribution of stable Mo and W isotopes in the modern hydrosphere remains limited. In this study, we provided the concentrations and isotope ratios of dissolved Mo and W in the oceans (the North Pacific and Indian Oceans), marginal seas (the East China Sea and Sea of Japan), and a river-estuary system in Japan (from the Uji-Yodo rivers to Osaka Bay). In the North Pacific and Indian Oceans, the W concentration was 48.2 ± 6.2 pmol/kg (ave ± 2sd, n = 109), δ186/184W was 0.52 ± 0.06 ‰, the Mo concentration was 105.1 ± 8.0 nmol/kg, and δ98/95Mo was 2.40 ± 0.06 ‰. The results indicate that W has the constant concentration and isotopic composition in the modern ocean as well as Mo. In the East China Sea and the Sea of Japan, the W concentration and δ186/184W in the upper water (< 1000 m depth) were different from those in the ocean (W = 56 ± 18 pmol/kg, δ186/184W = 0.45 ± 0.06 ‰, n = 24). However, the concentrations in deeper water were congruent with those in the oceans (W = 49.9 ± 7.6 pmol/kg, δ186/184W = 0.50 ± 0.02 ‰, n = 7). The Mo concentration was 105.4 ± 3.1 nmol/kg and δ98/95Mo was 2.36 ± 0.03 ‰ (n = 31) throughout the water column, congruent with those in the ocean. In the Uji River-Yodo River-Osaka Bay system, the W concentration reached 1074 pmol/kg and δ186/184W reached 0.20 ‰. We propose that the enrichment of W with a low δ186/184W in the river-estuary system and marginal seas is caused by anthropogenic pollution. Anthropogenic Mo pollution was not detected in marginal seas. However, the Mo concentration and δ98/95Mo showed high anomalies above the mixing line of river water and seawater in the lower Yodo River and Osaka Bay, implying possible anthropogenic pollution of Mo in the metropolitan area.

Whale sharks off the western coast of India have suffered high levels of fishing pressure in the past, and today continue to be caught in small-scale fisheries as by-catch. Additionally, coastlines in this region host very large and growing human populations that are undergoing rapid development. This exacerbates ongoing anthropogenic threats to this species such as pollution, habitat loss, and ship traffic. For these reasons, there is an urgent need for data on movement patterns of whale sharks in this region of the Indian Ocean. Here, we address this issue by providing the first data on the horizontal movements of whale sharks tagged in the northern Arabian Sea off the western coast of the Indian state of Gujarat. From 2011 to 2017, eight individuals, ranging from 5.4 to 8 m were tagged and monitored using satellite telemetry. Tag retention varied from 1 to 137 days, with the sharks traveling distances of 34 - ∼2,230 km. Six of the eight individuals remained close to their tagging locations, although two sharks displayed wide ranging movements into the Arabian Sea, following frontal zones between water masses of different sea surface temperatures. We explore the relationship between the movement patterns of these whale sharks and the physical and biological processes of the region.

Marine sponges are set to become more abundant in many near-future oligotrophic environments, where they play crucial roles in nutrient cycling. Of high importance is their mass turnover of dissolved organic matter (DOM), a heterogeneous mixture that constitutes the largest fraction of organic matter in the ocean and is recycled primarily by bacterial mediation. Little is known, however, about the mechanism that enables sponges to incorporate large quantities of DOM in their nutrition, unlike most other invertebrates. Here, we examine the cellular capacity for direct processing of DOM, and the fate of the processed matter, inside a dinoflagellate-hosting bioeroding sponge that is prominent on Indo-Pacific coral reefs. Integrating transmission electron microscopy with nanoscale secondary ion mass spectrometry, we track 15N- and 13C-enriched DOM over time at the individual cell level of an intact sponge holobiont. We show initial high enrichment in the filter-feeding cells of the sponge, providing visual evidence of their capacity to process DOM through pinocytosis without mediation of resident bacteria. Subsequent enrichment of the endosymbiotic dinoflagellates also suggests sharing of host nitrogenous wastes. Our results shed light on the physiological mechanism behind the ecologically important ability of sponges to cycle DOM via the recently described sponge loop.

Even as Japan remains divided over proposed changes in the role it should play in regional security issues, senior U.S. and Japanese military officers say they hope the Japanese navy may soon be freed up to play a more active role in the Pacific and beyond, plying some of the world's most hotly contested waters.

Even as Japan remains divided over proposed changes in the role it should play in regional security issues, senior U.S. and Japanese military officers say they hope the Japanese navy may soon be freed up to play a more active role in the Pacific and beyond, plying some of the world's most hotly contested waters.

Southeast Asia is home to some of the planet's most carbon-dense and biodiverse mangrove ecosystems. There is still much uncertainty with regards to the timing and magnitude of changes in mangrove cover over the past 50 years. While there are several regional to global maps of mangrove extent in Southeast Asia over the past two decades, data prior to the mid-1990s is limited due to the scarcity of Earth Observation (EO) data of sufficient quality and the historical limitations to publicly available EO. Due to this literature gap and research demand in Southeast Asia, we conducted a classification of mangrove extent using Landsat 1-2 MSS Tier 2 data from 1972 to 1977 for three Southeast Asian countries: Myanmar, Thailand, and Cambodia. Mangrove extent land cover maps were generated using a Random Forest machine learning algorithm that effectively mapped a total of 15,420.51 km2. Accuracy assessments indicated that the classification for the mangrove and non-mangrove class had a producer's accuracy of 80% and 98% user's accuracy of 90% and 96%, and an overall accuracy of 95%. We found a decline of 6,830 km2 between the 1970s and 2020, showing that 44% of the mangrove area in these countries has been lost in the past 48 years. Most of this loss occurred between the 1970s and 1996; rates of deforestation declined dramatically after 1996. This study also elaborated on the nature of mangrove change within the context of the social and political ecology of each case study country. We urge the remote sensing community to empathetically consider the local need of those who depend on mangrove resources when discussing mangrove loss drivers.

As a bio]diversity hotspot, the East Indies (Coral) Triangle possesses the highest biodiversity on the earth. However, evolutionary hypotheses around this area remain controversial; e.g., center of origin, center of accumulation, and center of overlap have been supported by different species. This study aims to answer the evolutionary influence of the Indonesian Seaway on the biodiversity of the Coral Triangle by recovering the evolutionary origins of a wide-ranging ommastrephid squid (Sthenoteuthis oualaniensis) based on integrated molecular and oceanographic clues from the Indo-Pacific. Three new clades were revealed; viz., clade I from the South China Sea, clade II from the northern East Indian Ocean, and clade III from the southern East Indian Ocean. These two Indian Ocean clades formed a monophyly closely related to clade IV from the Central-Southeast Pacific. Clade VI from the central Equatorial Pacific and clade V from the northern Eastern Pacific sit in basal positions of phylogenetic trees. Ancestral Sthenoteuthis was inferred to have originated from the Atlantic Ocean and sequentially dispersed to the northern East Pacific, central Equatorial Pacific, and West Pacific through the open Panama Seaway and being transported by westward North Equatorial Current. The East Indian Ocean was likely colonized by an ancestral population of clade IV from the Southeast Pacific. Westward South Equatorial Circulation could have promoted transoceanic migration of S. oualaniensis through the wide paleo-Indonesian Seaway. Sea level regression since the Miocene and the closure of the Indonesian Seaway at 4-3 Ma were responsible for the population genetic differentiation of S. oualaniensis in the Indo-Pacific. Therefore, the Indonesian Gateway played an important role in influencing marine organisms' migration and population differentiation through controlling and reorganizing circulations in the Indo-Pacific.

In a world where fish biodiversity is on the decline, highly vulnerable species are given a major boost today after scientists identified why some species are absent from reefs in the Indian and Pacific oceans. Incorporating this knowledge into conservation strategies will help to reduce human impact on species loss.

In a world where fish biodiversity is on the decline, highly vulnerable species are given a major boost today after scientists identified why some species are absent from reefs in the Indian and Pacific oceans. Incorporating this knowledge into conservation strategies will help to reduce human impact on species loss.

El Niño in the Pacific has an impact on dolphins over in Western Australia.

Today, the Khaled BIN SULTAN Living Oceans Foundation published our findings on the state of coral reefs in the Chagos Archipelago. This research mission gave us the chance to study some of the most isolated and well-protected coral reefs in the world. Our research, based on thousands of scientific surveys, found reefs in the Chagos Archipelago were some of the most diverse and had a higher density of fish than all of the reefs studied on the Global Reef Expedition, the largest coral reef survey and mapping expedition in history.

Two severe heat waves triggered coral bleaching and mass mortality in the Maldives in 1998 and 2016. Analysis of live coral cover data from 1997 to 2019 in shallow (5 m depth) reefs of the Maldives showed that the 1998 heat wave caused more than 90% of coral mortality leaving only 6.8 ± 0.3% of survived corals in all the shallow reefs investigated. No significant difference in coral mortality was observed among atolls with different levels of human pressure. Maldivian reefs needed 16 years to recover to the pre-bleaching hard coral cover values. The 2016 heat wave affected all reefs investigated, but reefs in atolls with higher human pressure showed greater coral mortality than reefs in atolls with lower human pressure. Additionally, exposed (ocean) reefs showed lower coral mortality than those in sheltered (lagoon) reefs. The reduced coral mortality in 2016 as compared to 1998 may provide some support to the Adaptive Bleaching Hypothesis (ABH) in shallow Maldivian reefs, but intensity and duration of the two heat waves were different. Analysis of coral cover data collected along depth profiles on the ocean sides of atolls, from 10 to 50 m, allowed the comparison of coral mortality at different depths to discuss the Deep Refuge Hypothesis (DRH). In the upper mesophotic zone (i.e., between 30 and 50 m), coral mortality after bleaching was negligible. However, live coral cover did not exceed 15%, a value lower than coral survival in shallow reefs. Low cover values of corals surviving in the mesophotic reefs suggest that their role as refuge or seed banks for the future recovery of some species in shallow-water reefs of the Maldives may be small. The repeatedly high coral mortality after bleaching events and the long recovery period, especially in sites with human pressure, suggest that the foreseen increased frequency of bleaching events would jeopardize the future of Maldivian reefs, and ask for reducing local pressures to improve their resilience.

The degree to which biotic communities are regionally enriched or locally saturated, and roles of key structuring processes, remain enduring ecological questions. Prior studies of reef-building corals of the Indo-West Pacific (IWP) found consistent evidence of regional enrichment, a finding subsequently questioned on methodological grounds. Here we revisit this relation and associated relations between richness and abundance (as "effective number of species"), and coral cover, used as a proxy for disturbance and competition. From 1994 to 2017, we sampled > 2,900 sites on shallow (typically < 8-10 m depth below reef crest) and deeper reef slopes in 26 coral ecoregions, from Arabia to the Coral Triangle, Eastern Australia, Micronesia and Fiji, for a total pool of 672 species. Sampling intensity varied among ecoregions but always approached asymptotic richness. Local coral communities on both shallow and deep reef slopes were, on average, comprised of 25% of regional pools, ranging from 12 to 43% for individual ecoregions. The richest individual shallow and deep sites, averaged across all ecoregions, comprised 42 and 40% of regional pools, ranging from 30 to 60%, the highest in environmentally marginal ecoregions. Analyses using log-ratio regression indicated that IWP coral communities on deeper reef slopes were intermediate between regionally enriched and locally saturated. Communities on shallow reef slopes showed more evidence of regional enrichment, consistent with these being most susceptible to disturbance. Unimodal curvilinear relations between local richness and coral cover provide support for disturbance mediation and competitive exclusion. IWP coral communities are clearly dynamic, shaped by biological, ecological, and oceanographic processes and disturbance regimes that influence reproduction, dispersal, recruitment, and survival. Yet there is also evidence for a degree of local saturation, consistent with a niche-neutral model of community assembly. The r

Long-distance drifting of seaweeds driven by ocean currents is an ideal model for exploring population-level genetic connectivity and phylogeographic structure. In the Indo-Pacific convergence region, we integrated phylogeographic and ocean current data and Lagrangian particle simulations to explore how the ocean currents contributed to the biogeographical patterns and population genetic connectivity of Sargassum polycystum. The oceanographic transport and direction of gene flow was in line with contemporary ocean currents. The S. polycystum geographical dispersal from glacial refugia homogenized the footprint of genetic divergence. The multidisciplinary intersection provides insights into the evolutionary history and biogeographic conservation of tropical seaweeds in the Indo-Pacific convergence region.

Basel Zoologists are unveiling the colorful secrets of coral reefs: On the Australian Great Barrier Reef they discovered a coral reef fish, the dusky dottyback that flexibly adapts its coloration to mimic other fishes and in doing is able to prey on their juvenile offspring. By changing colors, the dusky dottyback also decreases its risk of being detected by predators. The study has been published in the latest issue of the renowned scientific journal Current Biology.

Basel Zoologists are unveiling the colorful secrets of coral reefs: On the Australian Great Barrier Reef they discovered a coral reef fish, the dusky dottyback that flexibly adapts its coloration to mimic other fishes and in doing is able to prey on their juvenile offspring. By changing colors, the dusky dottyback also decreases its risk of being detected by predators. The study has been published in the latest issue of the renowned scientific journal Current Biology.