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Upper mantle anisotropy has been mapped beneath continents at high spatial resolution. Beneath the oceans, however, shear wave splitting constraints on upper mantle anisotropy are sparse, due to the paucity of seismic receivers. A technique that does not require the availability of seismic stations close to the region under study is differential PS‐SKS splitting. Here, we use global wavefield simulations to investigate circumstances under which PS‐SKS splitting can be applied, and then use this technique to measure upper mantle anisotropy beneath the Pacific Ocean basin. Our results demonstrate that upper mantle anisotropy in our study region mostly reflects shearing due to the Pacific plate. North of Fiji, we observe a rotation of fast polarization directions, away from the direction of absolute plate motion of the Pacific plate. This may reflect far‐field mantle flow effects associated with the subduction of the Australian plate beneath the Pacific. Plain Language Summary: Earthquakes cause seismic waves whose speeds sometimes depend on their polarization and propagation direction. This material property, called seismic anisotropy, can be used to infer the direction of flow in Earth's upper mantle. Seismic anisotropy is straightforward to measure directly beneath a seismic station, but harder to study if station coverage is sparse. We use a technique that allows us to infer upper mantle seismic anisotropy beneath the Pacific Ocean in places without nearby seismic stations. Our measurements show that while seismic anisotropy varies laterally beneath the Pacific Ocean, in most cases it can be explained by the movement of the Pacific tectonic plate, leading to horizontal shearing of the underlying mantle. North of Fiji, we can observe the effects that the subduction of the Australian beneath the Pacific tectonic plate has on upper mantle flow. Key Points: We test the robustness of differential PS‐SKS shear‐wave splitting measurements to characterize anisotropy near the PS bounce pointWe use this technique infer seismic anisotropy beneath the Pacific OceanA majority of our measurements can be explained by plate motion induced shearing beneath the Pacific plate [ABSTRACT FROM AUTHOR]

This study investigates the transient evolution of tropical Pacific sea surface temperature (SST) responses to a constant northern high-latitude solar heating in fully coupled CESM 1.2. The study identifies two stages through multiple ensemble runs. 1) In the first 3 years, a hemispherically asymmetric pattern emerges, caused by air–sea interactions associated with the anomalous cross-equatorial Hadley cell. The northern tropics experience warming that is blocked north of the equator by the intertropical convergence zone. The southeast Pacific cooling reaches the equatorial region and is amplified by the equatorial Ekman divergence. 2) Within a decade, the equatorial cooling is replaced by warming in the eastern equatorial basin. The anomalous warming that appears faster than the time scales of the oceanic ventilation is attributed to anomalous meridional heat convergence and weakening of the northern subtropical cell. Our findings highlight the influence of ocean dynamics on the temporal and spatial evolution of tropical SST response to hemispherically asymmetric heating. The initial cooling caused by Ekman divergence delays the arrival of slow warming, while initial wind and temperature anomalies set the stage for the weakening of the subtropical cell. The results have important implications for understanding the evolution of tropical SST patterns in observational records and future climate change simulations, as they show strong interhemispheric temperature asymmetry in the extratropics. [ABSTRACT FROM AUTHOR]

Aim: Lineages colonizing subtropical oceanic islands often have to overcome geographical isolation and novel climate stressors to found new populations. Historical and ecological factors influence the success of colonization and subsequent diversification, leaving a signal in the genetic constitution of the diverged, range‐restricted taxa. Here, we examined the historical biogeography of endemic marine fishes to quantify the role of geographical proximity and climate differences in determining colonization, and the underlying mechanisms of speciation. Location: Subtropical islands of the Southwest Pacific. Taxa: Thirty endemic marine ray‐finned fishes from 17 genera. Methods: Using parametric biogeographical history models, we estimated the ancestral geographical ranges for 144 species based on time‐calibrated phylogenies that included endemic species and their closest sister taxa, linking terminal nodes with geographical distribution classified into 14 biogeographical areas. Results: Ancestral range estimations revealed most species originated in Australia (66%), while only 10% and 7% originated in northern tropical Pacific locations and the East Pacific respectively, with 17% of species‐range estimations being inconclusive. Vicariant events alone were identified as the most likely process shaping range evolution in 57% of the 14 best‐fitting models, dispersal alone was favoured for 14% of species and both processes had a role for the remaining 29% of species. Across all phylogenies, likelihood‐ratio tests confirmed that geographical distance and climatic differences constrained dispersal in 73% and 33% of species, respectively. Main Conclusions: Marine fishes endemic to subtropical islands of the Southwest Pacific originated by vicariant and jump‐dispersal events mainly from ancestral populations in mainland Australia. Geographical distance and climatic differences are significant taxon‐specific factors influencing the dispersal of marine fishes in the region. [ABSTRACT FROM AUTHOR]

Since the early 21st century, the Asia-Pacific has become a dynamic region of development by some powerful countries in the world such as the United States (US), India, China, and Russia. Thus, the issue of ensuring maritime security to develop sea trade plays a central role in the strategies of these countries. From India's perspective, maritime security in the Indian Ocean - Pacific Ocean is a deciding factor in the development, affirming its position and creating a balance of power in the country in comparison with other countries in the region. Nevertheless, the developed sea trade of India has faced challenges from various countries including the US, and China. Therefore, India has promoted a cooperative relationship with Vietnam to guarantee maritime security for Indian traders in the region. This paper aims to provide general information about maritime security as well as to determine and estimate India's maritime security strategies. Additionally, it will present the role of Vietnam in India's maritime security policies. The findings show that both nations, India and Vietnam have adequate backup strategies, which is the foundation for developing sea trade sustainability. Furthermore, India and Vietnam will play an increasingly strong role in the Asia-Pacific in the future. [ABSTRACT FROM AUTHOR]

The responses of marine species to environmental changes and anthropogenic pressures (e.g., fishing) interact with ecological and evolutionary processes that are not well understood. Knowledge of changes in the distribution range and genetic diversity of species and their populations into the future is essential for the conservation and sustainable management of resources. Almaco jack (Seriola rivoliana) is a pelagic fish with high importance to fisheries and aquaculture in the Pacific Ocean. In this study, we assessed contemporary genomic diversity and structure in loci that are putatively under selection (outlier loci) and determined their potential functions. Using a combination of genotype–environment association, spatial distribution models, and demogenetic simulations, we modeled the effects of climate change (under three different RCP scenarios) and fishing pressure on the species' geographic distribution and genomic diversity and structure to 2050 and 2100. Our results show that most of the outlier loci identified were related to biological and metabolic processes that may be associated with temperature and salinity. The contemporary genomic structure showed three populations—two in the Eastern Pacific (Cabo San Lucas and Eastern Pacific) and one in the Central Pacific (Hawaii). Future projections suggest a loss of suitable habitat and potential range contractions for most scenarios, while fishing pressure decreased population connectivity. Our results suggest that future climate change scenarios and fishing pressure will affect the genomic structure and genotypic composition of S. rivoliana and lead to loss of genomic diversity in populations distributed in the eastern‐central Pacific Ocean, which could have profound effects on fisheries that depend on this resource. [ABSTRACT FROM AUTHOR]

This study conducted stable isotope analysis (δ13C, δ15N, and δ34S) on the epidermis and two skeletal elements (rib and squamosal bones) of Hawaiian green turtles (Chelonia mydas) and putative diet items obtained from two neritic sites: the Kona/Kohala coast and Oahu. Turtle tissues were collected in 2018–2020 and diet samples in 2018, 2019, and 2021. The effect of body size and sampling locality on individual bulk tissue isotope values was evaluated, and stable isotope mixing models based on δ13C, δ15N, and δ34S values from those tissues and four groups of food sources were used to reconstruct diet histories of the turtles. Mixing models indicated that green turtles along the Kona/Kohala coast consumed an omnivorous diet, whereas those from Oahu had an herbivorous diet. These diet make-ups are consistent with published gut content analyses. However, mixing models using the stable isotope ratios in rib and squamosal bone failed to yield reasonable diet histories, probably due to inadequacies of the applied trophic discrimination factor (TDF), a key model parameter. These results further establish that stable isotope ratios in the epidermis can be used effectively to study green turtle diet, but also reveal that more validation—and establishment of appropriate TDFs—is needed before bone can be used reliably to assess green turtle diet. [ABSTRACT FROM AUTHOR]

At 19:28 AM on 4 March 2021 (UTC), a Mw 8.1 megathrust earthquake occurred close to Raoul Island, New Zealand, on the Kermadec Subduction Zone. Closely following two other tsunamigenic ruptures, it triggered a tsunami that was quickly recorded by oceanic and coastal gauges. Analysis of 158 filtered sea-level records revealed that the tsunami had not only a regional impact but was recorded by most gauges in the Pacific Ocean and eight gauges in the Indian and the southern Atlantic Oceans, in good agreement with modelling results of tsunami propagation. Careful determination of tsunami arrival times and first and largest waves amplitude for each station support the fact that the first wave is almost never the highest one. The maximum amplitude is about three times higher than the first wave amplitude and the largest wave is recorded with a median value of ∼3 h after the first arrival. In addition, recordings of the largest wave of this small but transoceanic tsunami are not related to the distance to the earthquake epicentre. Finally, this tsunami which occurred simultaneously with several localised storms in the Pacific Ocean is an opportunity to highlight the difficulty in distinguishing between the different types of waves. [ABSTRACT FROM AUTHOR]

The western-central equatorial Pacific (WCEP) zonal wind affects El Niño-Southern Oscillation (ENSO) by involving a series of multiscale air-sea interactions. Its interannual variation contributes the most to ENSO amplitude. Thus, understanding the predictability of the WCEP interannual wind is of great importance for better predictions of ENSO. Here, we show that the North Pacific Oscillation (NPO) and the South Pacific Oscillation (SPO) alternate in fueling this interannual wind from late boreal winter to austral winter in the presence of background trade winds in different hemispheres. During the boreal winter-spring, the NPO registers footprints in the tropics by benefiting from the Pacific meridional mode and modulating the northwestern Pacific intertropical convergence zone (NITCZ). However, as austral winter approaches, the SPO takes over the role of the NPO in maintaining the anomalous NITCZ. Moreover, the interannual wind is further driven to the east in the positive phase of the SPO, by intensified central-eastern equatorial Pacific convection resulting from tropical-extratropical heat flux adjustments. A reconstructed WCEP interannual wind index involving only the NPO and the SPO possesses a long lead time for ENSO prediction of nearly one year. These two extratropical boosters enhance the viability of equatorial Pacific zonal wind anomalies associated with the large growth rate of ENSO, and the one in the winter hemisphere seems to be more efficient in forcing the tropics. Our result further indicates that the NPO benefits a long-lead prediction of the WCEP interannual wind and ENSO, while the SPO is the dominant extratropical predictor of ENSO amplitude. [ABSTRACT FROM AUTHOR]

The Pacific meridional modes (PMMs) are the leading ocean-atmosphere coupled modes in the subtropical northeastern (NPMM) and southeastern (SPMM) Pacific, respectively, and have been suggested to be key precursors to equatorial Pacific variability. Previous studies pointed out that both NPMM- and SPMM-related sea surface temperature (SST) anomalies are primarily driven by net surface heat flux variations during their equatorward evolution. However, whether oceanic heat advective processes would play a role during the evolution remains unclear. To address this issue, we perform an ocean mixed layer heat budget analysis based on observations and three ocean reanalysis datasets, and then reveal the effect of ocean advections on the evolution by comparing a fully coupled dynamic ocean model (DOM) to a slab ocean model (SOM). Our results suggest that for the NPMMevolution, ocean advections-primarily by anomalous meridional Ekman heat advections driven by mean and anomalous zonal wind stresses-play a damping role in the south of the NPMM. Thus, the NPMM SST anomalies appear to instead exhibit a poleward shift, although still freely propagating westward from the preceding boreal winter to the following summer. This finding challenges the traditional view that the NPMMpropagates equatorward through the wind-evaporation-SST feedback. For the SPMMevolution, ocean advections play a damping role in the center of the SPMM from boreal spring to summer, as well as an intensification role in the southwest Pacific during summer. However, the effect of the intensification on the SPMM evolution is hard to determine due to the strong simulation bias of the SPMMevolution in the DOM. [ABSTRACT FROM AUTHOR]

Based on daily data from the Japanese 55-year Reanalysis (JRA-55) covering the winters (NDJFM) from 1958 to 2018, this study examines the growth and decay mechanisms of the baroclinic wave packet (BWP) inferred from regression analysis over the North Pacific. Day-to-day kinetic energy (KE) and available potential energy (APE) budget analysis suggest that BWP is driven mainly by baroclinic energy conversion (CPB), barotropic energy conversion (CKB), and the nonlinear term (CKE). CPB acts as a predominant APE source for BWP. Part of CPB acts to overcome the APE loss caused by transient eddy flux and most of it acts as a dominant KE source to drive BWP throughout its lifespan. CKB acts as a KE source before day −1, and as a major KE sink to damp BWP afterward, in which the north–south gradient of the climatological meridional flow plays a key role. Similarly, CKE acts as a KE source before day 0 and as a major KE sink afterward. The damping effect of CKE comes mainly from the scale interaction through the advection of high-frequency meridional momentum by the low-frequency zonal flow. It turns out that the vertical geopotential flux divergence also plays an active role in the dynamical coupling of different vertical BWP parts. There is persistent geopotential flux transfer from the middle-tropospheric layer into the lower- and upper-tropospheric layers, which serves as a major KE source to drive the BWP anomalies for the two layers and a major KE sink for the middle-tropospheric layer where the baroclinic energy conversion is the strongest. Significance Statement: Previous studies indicate that baroclinic waves tend to organize into wave packets and are driven by the baroclinic instability. This study finds that the baroclinic waves decay mainly through the barotropic energy conversion and nonlinear processes. The results also indicate that the vertical geopotential flux divergence plays an active role in the dynamical coupling of the BWP anomalies in different layers of the troposphere. It is therefore very important to improve the representations of the climatological-mean flow, wave–mean flow interaction, and wave–wave interaction between high- and low-frequency waves in the midlatitudes, as well as the process of vertical transfer of the geopotential flux in numerical models for a better prediction of weather and climate variability in the extratropic regions. [ABSTRACT FROM AUTHOR]

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human‐driven disturbance. Using genus‐level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats. [ABSTRACT FROM AUTHOR]

Reversible scavenging, the oceanographic process by which dissolved metals exchange onto and off sinking particles and are thereby transported to deeper depths, has been well established for the metal thorium for decades. Reversible scavenging both deepens the elemental distribution of adsorptive elements and shortens their oceanic residence times in the ocean compared to nonadsorptive metals, and scavenging ultimately removes elements from the ocean via sedimentation. Thus, it is important to understand which metals undergo reversible scavenging and under what conditions. Recently, reversible scavenging has been invoked in global biogeochemical models of a range of metals including lead, iron, copper, and zinc to fit modeled data to observations of oceanic dissolved metal distributions. Nonetheless, the effects of reversible scavenging remain difficult to visualize in ocean sections of dissolved metals and to distinguish from other processes such as biological regeneration. Here, we show that particle-rich "veils" descending from high-productivity zones in the equatorial and North Pacific provide idealized illustrations of reversible scavenging of dissolved lead (Pb). A meridional section of dissolved Pb isotope ratios across the central Pacific shows that where particle concentrations are sufficiently high, such as within particle veils, vertical transport of anthropogenic surface-dissolved Pb isotope ratios toward the deep ocean is manifested as columnar isotope anomalies. Modeling of this effect shows that reversible scavenging within particle-rich waters allows anthropogenic Pb isotope ratios from the surface to penetrate ancient deep waters on timescales sufficiently rapid to overcome horizontal mixing of deep water Pb isotope ratios along abyssal isopycnals. [ABSTRACT FROM AUTHOR]

In the deep ocean, whale falls (deceased whales that sink to the seafloor) act as a boost of productivity in this otherwise generally food-limited setting, nourishing organisms from sharks to microbes during the various stages of their decomposition. Annelid worms are habitual colonizers of whale falls, with new species regularly reported from these settings and their systematics helping to resolve biogeographic patterns among deep-sea organic fall environments. During a 2017 expedition of the Australian research vessel RV Investigator to sample bathyal to abyssal communities off Australia's east coast, a natural whale fall was opportunistically trawled at ~1000 m depth. In this study, we provide detailed taxonomic descriptions of the annelids associated with this whale-fall community, using both morphological and molecular techniques. From this material we describe nine new species from five families (Dorvilleidae: Ophryotrocha dahlgreni sp. nov. Ophryotrocha hanneloreae sp. nov., Ophryotrocha ravarae sp. nov.; Hesionidae: Vrijenhoekia timoharai sp. nov.; Nereididae: Neanthes adriangloveri sp. nov., Neanthes visicete sp. nov.; Orbiniidae: Orbiniella jamesi sp. nov.), including two belonging to the bone-eating genus Osedax (Siboglinidae: Osedax waadjum sp. nov., Osedax byronbayensis sp. nov.) that are the first to be described from Australian waters. We further provide systematic accounts for 10 taxa within the Ampharetidae, Amphinomidae, Microphthalmidae, Nereididae, Orbiniidae, Phyllodocidae, Protodrilidae, Sphaerodoridae and Phascolosomatidae. Our investigations uncover unique occurrences and for the first time enable the evaluation of biogeographic links between Australian whale falls and others in the western Pacific as well as worldwide. [ABSTRACT FROM AUTHOR]

The aim of this article is to clarify the particular distribution of deep-water Indian Ocean scleractinian corals with respect to the location of the belts of the global oceanic conveyor. This study is based on the author's own and others' publications on the fauna of Indian Ocean corals; it ranks by depth the stations where these organisms have been found. It has been determined that a maximum of finds was obtained at a depth of 1–2 km, with the amount declining sharply at lower depths, and that the amount increases once more at a depth of 4–5 km. However, at lower depths, scleractinian corals are represented by just three species belonging to two genera. An asymmetrical spatial distribution of scleractinian corals at depths greater than 3 km was established, with a far greater number of stations in the western part of the ocean than in the east. This phenomenon is likely linked to the idiosyncracies of the circulation of both contemporary and Neogene water. Comparison of the fauna of Indian Ocean scleractinian corals at depths of 1–2 km with those of the Pacific, which have already been studied, shows that the Pacific features the greatest abundance of species, 109, while that of the Indian Ocean has 18 species. [ABSTRACT FROM AUTHOR]

We studied phenocrysts and melt inclusions in order to evaluate physical and chemical conditions of petrogenesis of the Sulawesi Island (southwestern Pacific subduction belt) basalts. The compositions of the clinopyroxene and plagioclase phenocrysts hosted by basalts of the Lokon Volcano indicate two types of melts: primitive and differentiated. The primitive magmas produced high-anorthite plagioclases that are absent from the Lokon volcano andesites. The second type of melts produced clinopyroxenes and plagioclases of similar composition in basalts and andesites. Similarities in the compositions of homogeneous glasses of melt inclusions in minerals from the Lokon Volcano and other volcanoes of Sulawesi Island and the SW Pacific suggest similar P–T conditions for the formation of magmatic systems. In particular, inclusion data demonstrate that basaltic magmas of the Lokon and Soputan volcanoes are primitive melts (SiO2 = 48.2–51.5 wt % and MgO up to 8 wt %), which is consistent with the contents of other oxides. These inclusions plot at the beginning of the "andesitic" trends in variation diagrams. Accordingly, these melts could be the primary melts for the entire magmatic system that formed andesitic to basaltic effusive rocks of the Tondono caldera and the Lokon and Soputan volcanoes. Based on the compositions of melt inclusions and host minerals in Lokon basalts, we concluded that clinopyroxene phenocrysts crystallized at two levels: 20.6–14.5 km (1150–1130°С) and 13–6 km (1145–1105°С), and plagioclase phenocrysts crystallized at 1160–1120°С. In general, our data on melt inclusions and phenocrysts indicate fundamental differences in the PTX parameters of the magmatic systems that formed basalts and andesites of Sulawesi Island. The basalt-hosted clinopyroxene phenocrysts crystallized from compositionally stable melts at slightly decreasing temperatures and a significant pressure drop during magma ascent. In contrast, crystallization of phenocrysts in the andesites occurred with delays in deep intermediate chambers, at constant pressures and a significant drop in temperature, which facilitated the processes of fractionation and evolution of melts. [ABSTRACT FROM AUTHOR]

The oceanic bottom mixed layer (BML) is a well mixed, weakly stratified, turbulent boundary layer. Adjacent to the seabed, the BML is of intrinsic importance for studying ocean mixing, energy dissipation, particle cycling and sediment-water interactions. While deep-seabed mining of polymetallic nodules is anticipated to commence in the Clarion-Clipperton Zone (CCZ) of the northeastern tropical Pacific Ocean, knowledge gaps regarding the form of the BML and its potentially key influence on the dispersal of sediment plumes generated by deep-seabed mining activities are yet to be addressed. Here, we report recent field observations from the German mining licence area in the CCZ that characterise the structure and variability of the BML locally. Quasi-uniform profiles of potential temperature extending from the seafloor reveal the presence of a spatially and temporally variable BML with an average local thickness of approximately 250 m. Deep horizontal currents in the region have a mean speed of 3.5 cm s - 1 and a maximum speed of 12 cm s - 1 at 18.63 ms above bottom over an 11 month record. The near-bottom currents initially have a net southeastward flow, followed by westward and southward flows with the development of complex, anticyclonic flow patterns. Theoretical predictions and historical data show broad consistency with mean BML thickness but cannot explain the observed heterogeneity of local BML thickness. We postulate that deep pressure anomalies induced by passing surface mesoscale eddies and abyssal thermal fronts could affect BML thickness, in addition to local topographic effects. A simplified transport model is then used to study the influence of the BML on the interplay between turbulent diffusion and sediment settling in the transport of deep-seabed mining induced sediment plumes. Over a range of realistic parameter values, the effects of BML on plume evolution can vary significantly, highlighting that resolving the BML will be a crucial step for accurate numerical modelling of plume dispersal. Article Highlights: Field observations detail the presence of bottom mixed layer in the abyss of the Clarion-Clipperton Zone in the northeastern tropical Pacific Mean local thickness of the layer is approximately 250 m, with large spatial and temporal heterogeneity that needs further understanding The transport of benthic sediment plumes generated by deep-seabed mining can be greatly influenced by bottom mixed layer variability [ABSTRACT FROM AUTHOR]

Background. Zooplankton plays an important role in the marine ecosystem. A high level of taxonomic expertise is necessary for accurate species identification based on morphological characteristics. As an alternative method to morphological classification, we focused on a molecular approach using 18S and 28S ribosomal RNA (rRNA) gene sequences. This study investigates how the accuracy of species identification by metabarcoding improves when taxonomically verified sequences of dominant zooplankton species are added to the public database. The improvement was tested by using natural zooplankton samples. Methods. rRNA gene sequences were obtained from dominant zooplankton species from six sea areas around Japan and registered in the public database for improving the accuracy of taxonomic classifications. Two reference databases with and without newly registered sequences were created. Comparison of detected OTUs associated with single species between the two references was done using field-collected zooplankton samples from the Sea of Okhotsk for metabarcoding analysis to verify whether or not the newly registered sequences improved the accuracy of taxonomic classifications. Results. A total of 166 sequences in 96 species based on the 18S marker and 165 sequences in 95 species based on the 28S marker belonging to Arthropoda (mostly Copepoda) and Chaetognatha were registered in the public database. The newly registered sequences were mainly composed of small non-calanoid copepods, such as species belonging to Oithona and Oncaea. Based on the metabarcoding analysis of field samples, a total of 18 out of 92 OTUs were identified at the species level based on newly registered sequences in the data obtained by the 18S marker. Based on the 28S marker, 42 out of 89 OTUs were classified at the species level based on taxonomically verified sequences. Thanks to the newly registered sequences, the number of OTUs associated with a single species based on the 18S marker increased by 16% in total and by 10% per sample. Based on the 28S marker, the number of OTUs associated with a single species increased by 39% in total and by 15% per sample. The improved accuracy of species identification was confirmed by comparing different sequences obtained from the same species. The newly registered sequences had higher similarity values (mean >0.003) than the pre-existing sequences based on both rRNA genes. These OTUs were identified at the species level based on sequences not only present in the Sea of Okhotsk but also in other areas. Discussion. The results of the registration of new taxonomically verified sequences and the subsequent comparison of databases based on metabarcoding data of natural zooplankton samples clearly showed an increase in accuracy in species identification. Continuous registration of sequence data covering various environmental conditions is necessary for further improvement of metabarcoding analysis of zooplankton for monitoring marine ecosystems. [ABSTRACT FROM AUTHOR]

In the subtropical North Pacific, the east‐west gradient of iron deposition as atmospheric Asian dust strongly affects the zonal distribution of biological N2 fixation activity in numerical models, but the in‐situ relationship at a basin‐scale is not well examined. We examined the trans‐Pacific zonal variation in N2 fixation activity on 23°N in summer along with environmental parameters that potentially influence diazotrophy. Dissolved inorganic iron (DFe) was consistently low (<0.4 nM) throughout the transect. The atmospheric dust iron (dust‐Fe) flux increased westward, whereas phosphate and labile phosphoric monoesters in the surface decreased westward. N2 fixation varied between 34.6 and 298 μmol‐N m−2 d−1 and was high (>200 μmol‐N m−2 d−1) in the central area (150–180°W). N2 fixation rates significantly increased with dust‐Fe input only in the western area (137–180°E), whereas the contribution of DFe diffused from below the euphotic zone was often larger in the eastern area (120–170°W). N2 fixation was considerably low in the phosphate‐depleted western area despite the excess amount of iron relative to phosphate, and it increased with the labile phosphoric monoesters stock. These indicated that N2 fixation was primarily limited by phosphorus in the western area, though this activity also increased with iron supply from dust, likely due to phosphorus‐iron co‐limitation. In contrast, in the phosphorus‐repleted eastern area, iron supplied from dust and below the euphotic zone appeared to limit N2 fixation. Overall, N2 fixation in the subtropical North Pacific was likely limited by zonally different factors relating to iron and phosphorus availability. Plain Language Summary: N2 fixation, a process that converts N2 gas into ammonia, substantially affects biological production in subtropical ecosystems, where nitrogenous nutrients are scarce. The availability of both iron and phosphorus are primary factors controlling the growth of N2‐fixing organisms. In North Pacific subtropical waters, iron input as atmospheric Asian dust is considered to control the east‐west variation in N2 fixation; however, their relationship is not well‐examined. Here, we investigated the trans‐Pacific distribution of N2 fixation activity with iron and phosphorus availability. Our results show that dust input correlates with N2 fixation in the western area (137–180°E), which is in contrast with the eastern area (120–170°W), where vertically diffused iron was also important. In the phosphate‐depleted western area, N2 fixation positively correlated with the proxies of phosphorus supply, suggesting phosphorus limitation. This indicates phosphorus availability substantially controls the zonal distribution of N2 fixation in the subtropical North Pacific through co‐limitation with iron. The limitations are relaxed in the central area (150–180°W), likely due to elevated nutrient supply caused by bottom topography, resulting in a peak in N2 fixation. Therefore, the dynamics of both iron and phosphorus must be considered simultaneously to predict the response of N2 fixation to environmental changes. Key Points: Along the zonal transect in the subtropical North Pacific, N2 fixation activity was high in the central area (150–180°W)The central North Pacific was characterized by intermediate iron and phosphorus supply in the euphotic zoneEast‐west gradient of phosphorus availability controls the N2 fixation in the North Pacific through likely co‐limitation with iron [ABSTRACT FROM AUTHOR]

Despite very low concentrations of cobalt in marine waters, cyanobacteria in the genus Prochlorococcus retain the genetic machinery for the synthesis and use of cobalt-bearing cofactors (cobalamins) in their genomes. We explore cobalt metabolism in a Prochlorococcus isolate from the equatorial Pacific Ocean (strain MIT9215) through a series of growth experiments under iron- and cobalt-limiting conditions. Metal uptake rates, quantitative proteomic measurements of cobalamin-dependent enzymes, and theoretical calculations all indicate that Prochlorococcus MIT9215 can sustain growth with less than 50 cobalt atoms per cell, ∼100-fold lower than minimum iron requirements for these cells (∼5,100 atoms per cell). Quantitative descriptions of Prochlorococcus cobalt limitation are used to interpret the cobalt distribution in the equatorial Pacific Ocean, where surface concentrations are among the lowest measured globally but Prochlorococcus biomass is high. A low minimum cobalt quota ensures that other nutrients, notably iron, will be exhausted before cobalt can be fully depleted, helping to explain the persistence of cobalt-dependent metabolism in marine cyanobacteria.

Linking 'omics measurements with biogeochemical cycles is a widespread challenge in microbial community ecology. Here, we propose applying genomic adaptation as 'biosensors' for microbial investments to overcome nutrient stress. We then integrate this genomic information with a trait-based model to predict regional shifts in the elemental composition of marine plankton communities. We evaluated this approach using metagenomic and particulate organic matter samples from the Atlantic, Indian and Pacific Oceans. We find that our genome-based trait model significantly improves our prediction of particulate C : P (carbon : phosphorus) across ocean regions. Furthermore, we detect previously unrecognized ocean areas of iron, nitrogen and phosphorus stress. In many ecosystems, it can be very challenging to quantify microbial stress. Thus, a carefully calibrated genomic approach could become a widespread tool for understanding microbial responses to environmental changes and the biogeochemical outcomes. This article is part of the theme issue 'Conceptual challenges in microbial community ecology'.

Slender sole Lyopsetta exilis is an abundant groundfish on the continental shelf and inner waters of British Columbia, Canada, where it reaches a maximum standard length of 44 cm. Benthic image surveys coupled with oxygen measurements in Saanich Inlet document a dense population in bottom conditions near anoxia (0.03 ml l-1 oxygen) where diel migrating zooplankton intersect the bottom; we confirm this species is a planktivore, which limits its depth range to the base of the migration layer. In a comparison with slender sole from a nearby well-oxygenated habitat, several probable effects of living in severe hypoxia emerge: both sexes are significantly smaller in Saanich and the sex ratio is male-skewed. Otoliths from the Saanich fish were difficult to read due to many checks, but both sexes were smaller at age with the largest female (20 cm) from the hypoxia zone registering 17 years. Hypoxia appears to have a direct consequence on growth despite good food supply in this productive basin. Hyperventilation, a low metabolic rate and a very low critical oxygen tension help this fish regulate oxygen uptake in severely hypoxic conditions; it will be particularly resilient as the incidence of hypoxia increases on the continental shelf. Data from small-mesh bottom-trawl surveys over four decades reveal an increase in mean annual catch per unit effort in southern regions of the province, including the outer shelf and the Strait of Georgia. The California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton database records a general decline in fish larvae on the Oregon-California shelf since 1990, but slender sole larvae are increasing there, as they are in the Strait of Georgia. We project that the slender sole will gain relative benefits in the future warming, deoxygenated northeast Pacific Ocean.

Abstract: In deep‐sea environments, plant remains of several origins are found, including branches, twigs, leaves, and wood pieces, among others. As most of the deep‐sea bottoms are oligotrophic and nutrient‐limited, plant remains provide an oasis of localized organic enrichment and a substrate for colonization. Sunken wood was suggested to play an important evolutionary role in the diversification of chemosynthetic ecosystems, possibly representing stepping stones for the colonization between vent and seep ecosystems. In order to understand colonization processes of the Pacific Costa Rican meio‐epifaunal assemblages associated with sunken wood, a field experiment was conducted on Mound 12 (8°55.778′N, 84°18.730′W) at ~1,000 m water depth. Woodblocks were placed in four different habitats (Mussel beds, tube worms, near mussel beds, rubble bottoms), and different local environmental conditions (seepage‐active and seepage‐inactive sites). Seven experimental Douglas fir woodblocks (each 1,047 cm2 in surface area) were deployed from the R/V Atlantis using the manned submersible Alvin in February 2009 and recovered after 10.5 months in January 2010. Sample processing and analyses led to a data set of abundance (total 9,951 individuals) and spatial distribution of nine meio‐epifaunal higher taxa/groups. Meio‐epifaunal densities on individual woodblocks ranged from 3 to 26 ind.10 cm2. Copepods accounted for the highest abundances (75.1%), followed by nauplii larvae (11.7%) and nematodes (9.8%). The maximum number of individuals (26.3 ind.10 cm−2) was found in blocks placed in seepage‐inactive areas (near active mussel beds) in contrast to 2.9 ind.10 cm−2 in active areas (within a mussel bed). A hierarchical cluster analysis grouped blocks according to seepage activity and not to habitat, but tests of similarity showed no significant differences in higher taxon composition and abundances, probably owing either to substrate homogeneity or low sample size. Copepods were the most abundant representatives, suggesting that this group is one of the most successful in colonizing in the early stage of succession, in this case while hardwood substrates are not yet decomposed or bored by bivalves.

BackgroundThe unusual holopelagic annelid Poeobius meseres Heath, 1930 (Flabelligeridae) was first collected from Monterey Bay, California and has been subsequently recorded across the northern Pacific from Japan to the Gulf of California. Rare occurrences in the eastern tropical Pacific have extended as far as 7° S off Peru.New informationUsing molecular phylogenetic analysis of a newly-collected specimen from the Salas y Gómez Ridge off Chile, we extend the known geographic range of P. meseres southwards by 2040 km. This subtropical specimen showed higher genetic similarity to a specimen from the type locality (< 1.5% pairwise COI distance) than to representatives from the Aleutian Islands and Japan (5-6%), establishing the first genetically-confirmed occurrence of this species in the Southern Hemisphere. The latitudinal range of P. meseres encompasses the sole collection locality, off Ecuador, of Enigma terwielii Betrem, 1925, a pelagic annelid which has been compared to P. meseres, but is indeterminable due to an inadequate description. We therefore suggest that the earlier sole record of E. terwielii may have been an occurrence of what is known now as P. meseres.

In the California Current Ecosystem, El Niño acts as a natural phenomenon that is partially representative of climate change impacts on marine bacteria at timescales relevant to microbial communities. Between 2014-2016, the North Pacific warm anomaly (a.k.a., the "blob") and an El Niño event resulted in prolonged ocean warming in the Southern California Bight (SCB). To determine whether this "marine heatwave" resulted in shifts in microbial populations, we sequenced the rpoC1 gene from the biogeochemically important picocyanobacteria Prochlorococcus and Synechococcus at 434 time points from 2009-2018 in the MICRO time series at Newport Beach, CA. Across the time series, we observed an increase in the abundance of Prochlorococcus relative to Synechococcus as well as elevated frequencies of ecotypes commonly associated with low-nutrient and high-temperature conditions. The relationships between environmental and ecotype trends appeared to operate on differing temporal scales. In contrast to ecotype trends, most microdiverse populations were static and possibly reflect local habitat conditions. The only exceptions were microdiversity from Prochlorococcous HLI and Synechococcus Clade II that shifted in response to the 2015 El Niño event. Overall, Prochlorococcus and Synechococcus populations did not return to their pre-heatwave composition by the end of this study. This research demonstrates that extended warming in the SCB can result in persistent changes in key microbial populations.

Massive, long-lived deep-sea red tree corals (Primnoa pacifica) form a solid, layered axis comprised of calcite and gorgonin skeleton. They are abundant on the outer continental shelf and upper slope of the Northeast Pacific, providing habitat for fish and invertebrates. Yet, their large size and arborescent morphology makes them susceptible to disturbance from fishing activities. A better understanding of their growth patterns will facilitate in-situ estimates of population age structure and biomass. Here, we evaluated relationships between ages, growth rates, gross morphological characteristics, and banding patterns in 11 colonies collected from depths of ~141-335 m off the Alaskan coast. These corals ranged in age from 12 to 80 years old. They grew faster radially (0.33-0.74 mm year-1) and axially (2.41-6.39 cm year-1) than in previously measured older colonies, suggesting that growth in P. pacifica declines slowly with age, and that basal diameter and axial height eventually plateau. However, since coral morphology correlated with age in younger colonies (< century), we developed an in-situ age estimation technique for corals from the Northeast Pacific Ocean providing a non-invasive method for evaluating coral age without removing colonies from the population. Furthermore, we determined that annual bands provided the most accurate means for determining coral age in live-collected corals, relative to radiometric dating. Taken together, this work provides insight into P. pacifica growth patterns to inform coastal managers about the demographics of this ecologically important species. With this new ability to estimate the age of red tree corals in-situ, we can readily determine the age-class structure and consequently, the maturity status of thickets, using non-invasive video survey techniques when coupled with mensuration systems such as lasers or stereo-cameras. Enhanced surveys could identify which populations are most vulnerable to disturbance from human activities, and which should be highlighted for protection.

Sweet potato dispersal from Americas to French Polynesia predates known human colonization periods, therefore being a long-standing dilemma. According to recent phylogenetic studies, the most likely hypothesis to explain this migration is the sea-drift long-distance dispersal, but no research indicating the response of I. batatas seeds to seawater conditions have been performed so far. The aim of this study was to understand seawater resistance in I. batatas, an essential feature for the sea-drift natural dispersal hypothesis, thus shedding light on the historical biogeography of this species, which also has implications on human civilization history, as the archaeological presence of sweet potato in both continents has been used as an evidence of pre-Columbian contacts between ancient civilizations. The experiment consisted of submitting sweet potato seeds to seawater treatments and observing the respective germination rates after different periods of immersion. Subsequently, one-way ANOVAs were conducted to test for significant differences between groups. All seeds from the seawater immersion treatments germinated, which confirms that I. batatas seeds are resistant to seawater salinity for a period of 120 days. Our results support the sea-drift natural dispersal hypothesis, thus shedding light on part of the logical conditions for one of the major hypotheses on the historical biogeography of this species, which also plays an important role in the discussions related to prehistorical human mobility in Polynesian islands.

The northern South China Sea continental margin is the key or critical segment of the Ocean-Continent Connection Zone (OCCZ) of the Great South China Block, the junction between the Tethyan and the (Paleo-) Pacific dynamic systems, and the interaction area between the Indian Ocean and the Pacific Ocean. However, due to the low-degree geophysical exploration in the past, the regional tectonic background, processes and mechanism of the transition between the Tethyan and the Pacific tectonic domains are unclear. Based on the latest large number of seismic profiles, we focus on the Cenozoic basin structure in the continental margin of the northern South China Sea and try to reveal the Mesozoic basement structures of the northern South China Sea continental margin, with the aim of exploring the pre-Cenozoic tectonic evolution and the Cenozoic opening, spreading, ridge fossil and closure of the South China Sea oceanic basin, so as to serve the accurate oil and gas exploration in this area at the same time. The seismic interpretation of the Pearl River Mouth Basin and the field structural investigation of the South China continental margin show that the OCCZ of the South China Block has experienced three processes: Mesozoic Indosinian collisional orogeny, Early Yanshanian accretionary orogeny and Late Yanshanian transpressive orogeny. During the Cenozoic era, it experienced the dispersive extension into basins under the control of NW-SE-directed normal extension in the early stage, the dextral pull-apart into basins under the control of NE-NNE-trending strike-slip faults in the middle stage, and the sinistral pull-apart into basins under the control of NW-WNW strike-slip faults in the late stage. In general, the transition process from the Tethyan to the Pacific tectonic systems can be subdivided into four stages: the transition from the Paleo-Tethyan to the Neo-Tethyan tectonic systems, the transition from the Neo-Tethyan to the Paleo-Pacific tectonic systems, the transition from the Neo-Tethyan to the Pacific tectonic systems, and the transition from the Paleo-Pacific to the Pacific tectonic systems. The tectonic transition of the East Asian OCCZ reflects the long-term mechanism of the Earth plate dynamic system driving the plate superconvergence in East Asia, in particular of the importance of the deep or submarine “Triple Poles”, the Southeast Asian U-shape subduction system, the Pacific LLSVP and the African LLSVP. More importantly, the Southeast Asian U-shape subduction system is also one of the important dynamic engines of the Earth plate motion.

Understanding of the biological diversity, involving molecular phylogenetic methods, is a fundamental task for a broad array of evolutionary, taxonomic, and ecological studies, as well as a basis for conservation. Our hydrobiological survey during an expedition in 2021 to the coastal waters of the Kuril Islands (the northwestern Pacific) revealed the undocumented diversity of the nudibranch molluscs. Two new species of the genera Zelentia and Cuthonella are described here using analysis of fine-scale morphological and molecular data. Representatives of the genus Zelentia prior to this study were known only from the North Atlantic and from the Canadian and US northeastern Pacific. In addition, two new distributional records of the previously described species Cuthonella denbei Korshunova et al., 2020 and Cuthonella soboli Martynov, 1992 are presented here for the first time. The molecular phylogenetic framework for the majority of the species of the genera Cuthonella and Zelentia, including the two new species, confirmed the taxonomic distinctness of the genus Zelentia (family Trinchesiidae) and the genus Cuthonella (family Cuthonellidae), and represents another important result of this study. Key words: biodiversity, Cuthonella, North Pacific, nudibranch molluscs, molecular phylogeny, phylogeography, Zelentia La comprehension de la diversite biologique, notamment par des methodes de phylogenetique moleculaire, constitue une tache fondamentale d'une vaste gamme d'etudes taxonomiques, ecologiques et de l'evolution, ainsi qu'un fondement de la conservation. Un leve hydrobiologique realise durant une expedition en 2021 dans les eaux littorales des Kouriles (nord-ouest de l'ocean Pacifique) revele une diversite non documentee de mollusques nudibranches. Deux nouvelles especes des genres Zelentia et Cuthonella sont decrites en utilisant une analyse de donnees moleculaires et morphologiques fines. Des representants du genre Zelentia n'etaient auparavant connus que de l'Amerique du Nord et des eaux canadiennes et etats-uniennes du nordest de l'ocean Pacifique. En outre, deux nouveaux cas de presence des especes deja decrites Cuthonella denbei Korshunova et al., 2020 et Cuthonella soboli Martynov, 1992 qui elargissent leurs aires de repartition respectives, sont presentes pour la premiere fois. Le cadre phylogenetique moleculaire pour la majorite des especes des genres Cuthonella et Zelentia, incluant deux nouvelles especes, confirme le caractere distinct sur le plan taxonomique du genre Zelentia (famille des trinchesiides) et du genre Cuthonella (famille des cuthonellides) et constitue un autre important resultat de la presente etude. [Traduit par la Redaction] Mots-cles : biodiversite, Cuthonella, Pacifique Nord, mollusques nudibranches, phylogenetique moleculaire, phylogeographie, Zelentia, Introduction The Kuril Islands are scientifically and economically an important chain of over 50 volcanic islands in the northwestern Pacific with diverse fauna and flora (e.g., Kotlyakov et al. 2009; [...]

CONTENTS I Introduction 1 II Culture and the Anthropocene 6 III Oceans as Lived and Living Cultural Spaces: Pacific Histories and Presents 11 IV Oceans as Gateways: Reimagining International Law [...], This article argues that international legal responses to the Anthropocene cannot be adequately designed or implemented unless peoples&apos; cultural relationships with the ocean are taken into account. Drawing on the voices of Pacific peoples and their descriptions of the ocean as territory and a source of identity, we debunk the idea of the ocean as a static or transient place, arguing instead that it is a core element of &apos;territory&apos;, place and belonging. International cultural heritage law offers a pathway for leveraging these narratives into international legal regimes, including the development of international mobility regimes. To the extent that Pacific peoples are set to bear the brunt of the costs of the Anthropocene, and because their relationships with the ocean provides innovative ways of rethinking the design and implementation of international law, it is imperative that their voices are brought to the fore.

Residents of the twin cities of Indiana Harbor and East Chicago in northwest Indiana, weary of food and gasoline rationing and tired from fashioning the weapons needed for victory, gathered [...]

Climate-induced environmental variability is proving to be a driving factor reshaping the distribution and altering the movement of marine species. However, how Pacific Ocean squids, with their 1-year life span and adaptive abilities, and which support >25% of global squid fisheries, respond to environmental variability is poorly understood. We address this knowledge gap by constructing spatio–temporal models for two squid species in three fishing grounds (Ommastrephes bartramii in the northwest Pacific Ocean and Dosidicus gigas in the eastern Pacific Ocean) using generalized additive mixed models based on data from digitized Chinese squid-jigging logbooks for 2005–2017. The relationships between environmental variables and local abundance of squids reflected by environmental and traditional spatial response curves track changes in climate. The peaks and troughs in squid biomass coincide with La Niña and El Niño events, but are moderate in contrast to the effects of directional climate-induced environmental variability. We find substantial poleward shifts by squids inhabiting low and middle latitudes. These findings have broad implications for food security and open ocean ecosystem dynamics. [ABSTRACT FROM AUTHOR]

We report a mode of ionospheric resonance induced by the 2022 January 15, Hunga Tonga–Hunga–Ha'apai volcanic eruption, captured globally through ground-based Global Navigation Satellite Systems networks. In the near-field region, we observe a strong ionospheric disturbance in the total electron content, including contributions from acoustic and gravity waves. In contrast, propagation of gravity waves, seismic airwaves diffracted by topographic barriers and/or atmospheric Lamb waves can be documented for far-field ionospheric disturbances. Specifically, the atmospheric wave propagation towards the Hawaii Islands involved three distinct modes of ionospheric perturbation through Rayleigh, gravity and atmospheric Lamb waves. Further, we also noted that the peak-to-peak amplitude of the disturbance reached ∼ 8.7 per cent of the background electrons, which is significantly higher than the recent volcanic explosions in the Japanese Islands and the 2020 chemical explosion in Beirut. The ionospheric total electron content perturbations can provide important information about the volcanic source, hence they could be useful as a measure of eruption intensity and for real-time hazard monitoring. [ABSTRACT FROM AUTHOR]