Coral reefs are under severe threat from global warming, particularly due to the increasing frequency of mass coral bleaching events. This study documents the effects of the fourth global coral bleaching event on corals of Tahanea, a remote uninhabited French Polynesian atoll over a 10-month period. Coral surveys (transects and tracking of individual colonies) and temperature monitoring were conducted by one in situ observer. The marine heatwave lasted 80 days, from January 24, 2024, to April 12, 2024, with a peak intensity of + 1.55 °C above climatological levels. This event was the longest in the past 30 years in the South Pacific region as well as the most intense in terms of cumulative intensity (79.2 °C·days) and daily degree heating week (DHW) annual maximum (reaching 4.7 °C weeks−1). In May 2024, 11–16

Open-pit mines are known to exacerbate soil erosion and generate large quantities of fine particles, which are carried by watersheds to coastal waters. In New Caledonia, the exploitation of ultramafic massifs highly enriched in metals (Co, Cr, Fe and Ni) can therefore have harmful effects on tropical lagoons by increasing turbidity and releasing toxic compounds to the marine food web. In this study, we used various biogeochemical (POC, delta 13C, PON, POP, Chl a, Pheo a) and geochemical (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, Ti, V, Zn) parameters to examine the origin, transport, and fate of suspended particulate matter (SPM) in the Voh lagoon after eight years of mining activities. Maximum concentrations of SPM (1.93 mg.L- 1), Chl a (1.23 & micro;g.L- 1), Cr (327 & micro;g.g- 1), Co (32.4 & micro;g.g- 1) and Ni (756 & micro;g.g- 1) were observed in Vavouto bay, downstream of the Koniambo ultramafic massif watershed. Approximately 34% of SPM present in surface waters originated from the Koniambo ultramafic massif. The increase in particle inputs linked to mining activity has led to the eutrophication of the lagoon. Due to transport processes, SPM are now distributed throughout the lagoon, settling at the bottom and burying the corals. In this context, the Voh lagoon presents a high ecological risk. This study provides an opportunity to refine predictive modelling techniques for contamination scenarios.

While the rise in global ocean temperature continues its course, reaching 1.45 +/- 0.12 degrees C above pre-industrial level according to the World Meteorological Organization in 2023, marine heatwave frequencies and intensities increase. Consequently, coral reef ecosystems, which are among the most vulnerable environments, are strongly impacted by dystrophic events and corals experiencing increasing frequencies of bleaching events. That has devastating consequences for the Pacific Island countries and territories (PICTs) that strongly rely on these ecosystems. In situ observation remains the best alternative for providing accurate characterization of long-term trends and extremes in these shallow environments. This paper presents the coastal temperature dataset of the ReefTEMPS monitoring network (Varillon et al., 2025, 10.17882/55128; Liao et al., 2025, 10.17882/82291) in which moored stations are implemented over a number of PICTs over a wide region in the western and central South Pacific from New Caledonia to French Polynesia. These in situ temperature time series are unique in several ways: in the length of some historical stations dating back to 1958 for the oldest, thus providing more than 65 years of daily data; in the number of countries sampled (16 PICTs); and in the variety of coral ecosystems monitored (from atolls to high islands and from barrier reefs' external slopes to shallow and narrow lagoons). Measurement devices have evolved over the years to provide increasingly precise and frequent observations, so the ReefTEMPS network was endorsed as a French National Observation Service in 2020, a label ensuring quality-controlled and open-access data of long-term observations. All stations are publicly available in ASCII or formatted NetCDF files either in the ReefTEMPS dedicated information system, which also allows for a quick visualization of time series, or on the SEANOE marine data platform. All links and accesses to these temperature time series are provided herein. The longevity of these temperature time series allows for diagnosing long-term trends, highlighting the influence of multiple processes on temperature dynamics (e.g. internal waves, cyclones, seasonal, and climate modes) and documenting the time evolution of extreme events. All files are made publicly available on dedicated SEANOE repositories.

The objective of this study is to assess the potential impact of nickel mining activity on zooplankton communities in a coral reef channel lagoon (Voh Koné, New Caledonia). During a multidisciplinary campaign in February 2018, we analyzed the variation in zooplankton abundance, biomass and taxonomic diversity, as a function of the distance from the metallurgical plant site and of hydrodynamic conditions and environmental variables. We also compared these results with those obtained in an earlier study conducted in 2009 prior the mining. The results show the high variability of planktonic variables between stations and periods, mainly related to natural factors (hydrodynamics, climatic events). However, lagoon zooplankton also appears to be affected by mining development, and in particular by the increase in sediment inputs and consequent turbidity. Zooplankton taxonomic richness and diversity were negatively correlated with non-algal particle concentrations (CNAP considered as an indicator of turbidity) with 10 more sensitive taxa completely absent at the highest concentrations. We interpret these negative relationships as the result of the degradation of food quality by mixing with inedible and less assimilable non-algal particles. The effect of metal toxicity cannot be excluded, even though the metal concentrations recorded in the lagoon are far from known toxic concentrations, but this hypothesis should be further developed. Overall, our results highlight the good resilience of lagoon zooplankton probably partly related to the high renewal rate of the lagoon water.

Accelerating rate of human impact and environmental change severely affects marine biodiversity and increases the urgency to implement the Convention on Biological Diversity (CBD) 30×30 plan for conserving 30% of sea areas by 2030. However, area-based conservation targets are complex to identify in a 3-dimensional (3D) ocean where deep-sea features such as seamounts have been seldom studied mostly due to challenging methodologies to implement at great depths. Yet, the use of emerging technologies, such as environmental DNA combined with modern modeling frameworks, could help address the problem. We collected environmental DNA, echosounder acoustic, and video data at 15 seamounts and deep island slopes across the Coral Sea. We modeled 7 fish community metrics and the abundances of 45 individual species and molecular operational taxonomic units (MOTUs) in benthic and pelagic waters (down to 600-m deep) with boosted regression trees and generalized joint attribute models to describe biodiversity on seamounts and deep slopes and identify 3D protection solutions for achieving the CBD area target in New Caledonia (1.4 million km 2 ). We prioritized the identified conservation units in a 3D space, based on various biodiversity targets, to meet the goal of protecting at least 30% of the spatial domain, with a focus on areas with high biodiversity. The relationship between biodiversity protection targets and the spatial area protected by the solution was linear. The scenario protecting 30% of each biodiversity metric preserved almost 30% of the considered spatial domain and accounted for the 3D distribution of biodiversity. Our study paves the way for the use of combined data collection methodologies to improve biodiversity estimates in 3D structured marine environments for the selection of conservation areas and for the use of biodiversity targets to achieve area-based international targets.

Between 2018 and 2022, four pearl farming Tuamotu atolls of French Polynesia were monitored with autonomous oceanographic instruments to measure the hydrodynamics of atoll lagoons and the ocean–lagoon water exchanges. These surveys were conducted within the framework of the ANR-funded MANA (Management of Atolls) project and its extensions to additional sites. The overarching goal was to improve knowledge on the processes influencing the spat collection of the pearl oyster Pinctada margaritifera, the oyster species used to produce black pearls. These data sets are also critical for the calibration and validation of 3D high spatial resolution hydrodynamic models used to study oyster larval dispersal within lagoons. The observational strategies focused on the characterization of ocean–lagoon exchanges through passes and hoa (i.e., shallow reef flats), lagoon circulation, incident waves breaking on the forereef, water elevation inside the lagoon as well as spatial temperature variability. Chronologically, the investigated atolls were first Raroia Atoll with 9 months of measurements between May 2018 and March 2019 during which the MALIS1 and MALIS2 cruises on-board the R/V ALIS took place. It was followed by a 4 month deployment in Takapoto Atoll (November 2021 to March 2022). In late April 2022, Apataki Atoll was instrumented until end of July, followed by Takaroa measurements between July and October 2022. Apataki (Leg2) and Takaroa Atoll were conjointly instrumented during the MALIS 3 oceanographic cruise. Altogether, those multi-atoll data bring a worldwide unique oceanographic atoll data set that is useful for addressing local pearl farming questions but potentially beneficial for other fundamental and applied investigations. Each data set was post-processed, quality controlled and converted into NetCDF format. Files are available in open source into dedicated repositories in the SEANOE marine data platform. Links (DOI) of individual data sets are provided in Table 2.

Between 2018 and 2022, four pearl farming Tuamotu atolls of French Polynesia were monitored with autonomous oceanographic instruments to measure the hydrodynamics of atoll lagoons and the ocean-lagoon water exchanges. These surveys were conducted in the frame of ANR MANA (Management of Atolls) project and its extensions to additional sites. The overarching goal was to improve knowledge on the processes influencing the spat collection of the pearl oyster Pinctada margaritifera, the oyster species used to produce black pearls. These data sets are also critical for the calibration and validation of 3D high spatial resolution hydrodynamic models used to study the oyster larval dispersal within lagoons. The observational strategies focused on the characterization of ocean/lagoon exchanges through passes and hoa (i.e., shallow reef flats), lagoon circulation, incident waves breaking on the forereef, water elevation inside lagoon as well as spatial temperature variability. Chronologically, the investigated atolls were first Raroia Atoll with 9 months measurements between May 2018 and March 2019 during which the MALIS1 and MALIS2 cruises on-board the R/V ALIS took place. It was followed by a 4-month deployment in Takapoto Atoll (November 2021 to March 2022). In late April 2022, Apataki Atoll was instrumented until end of July, followed by Takaroa measurements between July to October. Apataki (Leg2) and Takaroa Atoll were conjointly instrumented during the MALIS 3 oceanographic cruise. Altogether, those multi-atoll data bring a worldwide unique oceanographic atoll data set, useful to address local pearl farming questions but potentially beneficial for other fundamental and applied investigations. Each data set was post processed, quality controlled and converted in NetCDF format. Files are available in open source into dedicated repositories in the SEANOE marine data platform with permanent DOIs.

Benthic exchanges of oxygen and nutrient at the sediment-water interface were investigated under light and dark conditions at 5 selected sites in a sub-tropical atoll. Mean oxygen fluxes were - 1316.5 ± 242.0 μmol m-2 h-1 and mean effluxes of oxygen under light conditions were 2231.7 ± 626.4 μmol m-2 h-1, presumably due to microphytobenthos present at the sediment-water interface. The consequences of this high related productivity was a systematic consumption of nutrients (DIN, PO4 and Si(OH)4) during almost all light incubations, contrasting with the effluxes of nutrients during dark incubations. Our results suggest that the sediments were net autotrophic and the oxygen balance in favor of microbenthic production when compared to community demand. Diurnal rates of gross benthic primary productivity were high (3423 ± 1192 μmol m-2 h-1) which emphasize the role of microphytobenthos in maintaining the oxygen reservoir in tropical lagoons.

This study reports the first measurements of nitrogen uptake and new data on carbon fixation (15N/13C incorporation) for two size-fractionated phytoplankton (<2 μm and >2 μm), on organic matter, and phytoplankton stocks in Ahe lagoon. Data were collected between November and December 2017, during the hot season with prevailing trade winds. Ammonium and nitrate uptake data (7.58 to 39.81 and 1.80 to 21.43 μmol N m−3 h−1, respectively) suggest a rapid turn-over of N-nutrients in the water column and show that primary production was largely sustained by recycled nitrogen providing 68% of the pelagic N demand. These results highlight the spatial heterogeneity of the measured processes linked to the local hydrodynamics, exhibiting higher regenerated production in the more exploited southwestern part of the lagoon and a higher proportion of new production in the north. Intense nutrient recycling appears to promote nanophytoplankton production which is critical for pearl oyster growth.

Abstract. On the 5th of December 2018, a magnitude Mw 7.5 earthquake occurred southeast of Maré, an island of the Loyalty Archipelago, New Caledonia. This earthquake is located at the junction between the plunging Loyalty ridge and the southernmost Vanuatu arc, in a tectonically very active area regularly subjected to strong seismic crises and events higher than magnitude 7 and up to 8. Widely felt in New Caledonia it has been immediately followed by a tsunami warning, confirmed shortly after by a first wave arrival at the Loyalty Islands tide gauges (Maré and Lifou), then along the east coast of Grande Terre of New Caledonia and in several islands of the Vanuatu Archipelago. Seafloor initial deformation linked to tsunami generation has been modeled with MOST numerical code using earthquake parameters available from seismic observatories. Then the wave propagation has been modeled using SCHISM, another modelling code solving the shallow water equations on an unstructured grid based on a new regional DEM of ~180 m resolution and allowing refinement in many critical areas. Finally, the results have been compared to tide gauge records, field observations and testimonials from 2018. The arrival times, wave amplitude and polarities present good similarities, especially in far-field locations (Hienghène, Port-Vila and Poindimié). Maximum wave heights and energy maps for two different scenarios highlight the fact that the orientation of the source (strike of the rupture) played an important role, focusing the maximum energy path of the tsunami south of Grande-Terre and the Isle of Pines. However, both scenarios indicate similar propagation toward Aneityum, Vanuatu southernmost island, the bathymetry acting like a waveguide. This study has a significant implication in tsunami hazard mitigation in New Caledonia as it helps to validate the modelling code and process used to prepare a scenarios database for warning and coastal evacuation.

On 5 December 2018, a magnitude Mw 7.5 earthquake occurred southeast of Maré, an island of the Loyalty Islands archipelago, New Caledonia. This earthquake is located at the junction between the plunging Loyalty Ridge and the southern part of the Vanuatu Arc, in a tectonically complex and very active area regularly subjected to strong seismic crises and earthquakes higher than magnitude 7 and up to 8. Widely felt in New Caledonia, it was immediately followed by a tsunami warning, confirmed shortly after by a first wave arrival at the Loyalty Islands tide gauges (Maré and Lifou), and then along the east coast of Grande Terre of New Caledonia and in several islands of the Vanuatu Archipelago. Two solutions of the seafloor initial deformation are considered for tsunami generation modeling, one using a non-uniform finite-source model from USGS and the other being a uniform slip model built from the Global Centroid Moment Tensor (GCMT) solution, with the geological knowledge of the region and empirical laws establishing relationships between the moment magnitude and the fault plane geometry. Both tsunami generation and propagation are simulated using the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM), an open-source modeling code solving the shallow-water equations on an unstructured grid allowing refinement in many critical areas. The results of numerical simulations are compared to tide gauge records, field observations and testimonials from 2018. Careful inspection of wave amplitude and wave energy maps for the two simulated scenarios shows clearly that the heterogeneous deformation model is inappropriate, while it raises the importance of the fault plane geometry and azimuth for tsunami amplitude and directivity. The arrival times, wave amplitude and polarities obtained with the uniform slip model are globally coherent, especially in far-field locations (Hienghène, Poindimié and Port Vila). Due to interactions between the tsunami waves and the numerous bathymetric structures like the Loyalty and Norfolk ridges in the neighborhood of the source, the tsunami propagating toward the south of Grande Terre and the Isle of Pines is captured by these structures acting like waveguides, allowing it to propagate to the north-northwest, especially in the Loyalty Islands and along the east coast of Grande Terre. A similar observation results from the propagation in the Vanuatu islands, from Aneityum to Efate.

ReefTEMPS is a sensor network which is part of the French national federative Research Infrastructure for coastal ocean and seashore observations ILICO.

La salinité de surface de la mer (SSS : Sea Surface Salinity) influence la dynamique océanique et porte la signature du cycle de l'eau à l'interface océan-atmosphère. Pour mieux comprendre ses variations, le Service national d'observation SSS (SNO SSS) du Laboratoire d'études en géophysique et océanographie spatiales (Legos, Toulouse) gère un réseau global de navires d'opportunité équipés de thermosalinographes, initié il y a 50 ans. La maintenance des instruments est effectuée aux ports de Nouméa et du Havre par l'Institut de recherche pour le développement (IRD). Les données sont transmises en temps réel pour la surveillance des instruments et l'océanographie opérationnelle. Après correction des dérives instrumentales en temps différé, les données sont mises à disposition de la communauté scientifique internationale, et permettent d'étudier des processus océaniques et climatiques d'échelle régionale à globale, ou de valider modèles et données satellitaires. Sea Surface Salinity (SSS) affects the ocean dynamics and bears the signature of the water cycle at the ocean-atmosphere interface. To better understand its variations, the French SSS Observation Service from the Laboratory for Studies in Geophysics and Spatial Oceanography (LEGOS, Toulouse, France) manages a global network of voluntary observing ships equipped with thermosalinographs (TSG), initiated 50 years ago. The instruments are regularly serviced at harbour calls in New Caledonia and mainland France by the French National Research Institute for Sustainable Development (IRD). Data are transmitted in real time for instrument monitoring and operational oceanography. After correction of instrumental drifts in delayed time, data are freely distributed to the international research community, and used for process-oriented climate studies from regional to global scale, or for validation of models and satellite data.

ReefTEMPS is a sensors network initiated in 1958 to monitor the coastal area of the South, West and South-West Pacific. This long-term observatory allows the acquisition of several parameters: Sea temperature, Electrical conductivity / practical salinity, Sea pressure / Waves height & period, Fluorescence, PH / acidity, Turbidity, with frequency running from 1 second to 30 minutes). The main objective is to study the climatic parameters of the tropical ocean with a focus on the coastal sea waters to monitor the long-term effects of the global change and its impacts on the coral reefs and their resources. ReefTEMPS is an observation network operated by the LEGOS since 2018 (and before by GOPS (South Pacific integrated observatory for the environment, terrestrial and marine biodiversity)). Five operators each manage a sub-region : WP1 New-Caledonia (IRD Noumea), WP2 French Polynesia (SO CORAIL / CRIOBE), WP3 Pacific States (SPC), WP4 Fidji (USP, WP5 Futuna (UNC). ReefTemps is part of the French national Research Infrastructure IR I-LICO. ReefTemps include a sensors-oriented environmental information system. It provides different types of interoperable services (including OGC standard SOS - Sensor Observation Service), each tailored to a specific scientific user community. The measurements provided by sensors, deployed for more than 40years for some, are stored in a dedicated database designed by US IMAGO in the late 2000s. All data acquired are publicly accessible without any restriction (under CC-BY licence). The extracted data are accessible from this ReefTEMPS landing page with a downloadable ZIP file. All the data acquired, including the most recent data, are accessible from the ReefTemps data portal and through the different ReefTEMPS web services. The ZIP archive contains all ReefTemps data acquired since 1958 to 14 Febrary 2018, for all parameters, and with different quality levels (from RAW to historical series). The ZIP archive contains 170 data files in NetCDF OceanCite 2.0 format. There is one file for each platform, with different parameter and different quality level.

ReefTEMPS est un reseau de capteurs de temperature, pression et salinite dans le domaine cotier du Pacifique Sud, Ouest et Sud-Ouest, opere par le GOPS (Grand Observatoire de l'environnement et de la biodiversite terrestre et marine du Pacifique Sud). Un des objectifs initiaux du projet etait de fournir differents types de services interoperables adaptes pour chacun d'eux a une communaute scientifique utilisatrice particuliere. Il devait aussi etre integre une base de donnees de mesures issues de capteurs deployes pour certains depuis plus de 40 ans. Ainsi, le systeme d'information a ete cree en 2011 et l'utilisation de SOS (Sensor Observation Service - http://www.opengeospatial.org/standards/sos) nous a semble pertinente des sa creation. En 2016, ce systeme d'information a ete modernise. En 2016, le systeme a ete porte sous Docker, permettant ainsi de simplifier les processus de deploiement et de mettre en place les dernieres versions des technologies utilisees. Nous sommes notamment passes de la version 1 a la version 2 de SOS et avons reorganise l'application tant sur le fond (notions d'offering, component et systems reconsiderees, nouvelles specifications SOS 2.x prises en compte) que sur la forme (REST au lieu de SOAP, JSON privilegie a XML pour l'echange de donnees). La nouvelle version est en production depuis juin 2017 : http://reeftemps.observatoire-gops.org. Toutes les donnees acquises sont accessibles publiquement sans restriction.

From March 18 to April 2, 2017, the PUFFAlis expedition took place aboard research vessel Alis of IRD. This campaign was a continuation of previous oceanographic expeditions concerned with the feeding areas of seabirds (MOMAlis) as well as on land on the Gouaro Deva shearwater colony. It was also the extension of the NECTAlis campaigns that were dedicated at studying the oceanic trophic chain that leads to tunas. Six scientists embarked to sample the different levels of the oceanic trophic chain of the New Caledonia basin off Pindai. In the middle of the expedition, a day was devoted to communicating with the high school students of Pouembout and the services of the environment and fisheries of the Northern Province. The expedition’s logbook is preceded by the press release issued on this occasion.

Sea Surface Salinity (SSS) is an essential climate variable that requires long term in situ observation. The French SSS Observation Service (SSS-OS) manages a network of Voluntary Observing Ships equipped with thermosalinographs (TSG). The network is global though more concentrated in the tropical Pacific and North Atlantic oceanic basins. The acquisition system is autonomous with real time transmission and is regularly serviced at harbor calls. There are distinct real time and delayed time processing chains. Real time processing includes automatic alerts to detect potential instrument problems, in case raw data are outside of climatic limits, and graphical monitoring tools. Delayed time processing relies on a dedicated software for attribution of data quality flags by visual inspection, and correction of TSG time series by comparison with daily water samples and collocated Argo data. A method for optimizing the automatic attribution of quality flags in real time, based on testing different thresholds for data deviation from climatology and retroactively comparing the resulting flags to delayed time flags, is presented. The SSS-OS real time data feed the Coriolis operational oceanography database, while the research-quality delayed time data can be extracted for selected time and geographical ranges through a graphical web interface. Delayed time data have been also combined with other SSS data sources to produce gridded files for the Pacific and Atlantic oceans. A short review of the research activities conducted with such data is given. It includes observation-based process-oriented and climate studies from regional to global scale as well as studies where in situ SSS is used for calibration/validation of models, coral proxies or satellite data.

Donnees de temperature cotiere du Pacifique Sud et Sud-Ouest ReefTEMPS est un reseau de capteurs de temperature des eaux cotieres de differents etats insulaires du Pacifique Sud et Sud-Ouest pour le suivi a long terme du changement climatique et de ses effets sur l'etat des recifs coralliens et de leurs ressources. Le systeme d'information SI-TEC-PSO permet la gestion et la valorisation de ces donnees d'observation. La genericite du SI permet egalement de gerer d'autres variables issues de nouveaux capteurs. En chiffres 18 pays 21 M de mesures 104 plateformes serie de donnees cycle de mesure Architecture orientee services suite de donnees d'observation issues d'un instrument sur une plateforme donnee et une periode continue regroupement de donnees d'observation, par agregation de plusieurs cycles, ayant meme plateforme, parametre physique, niveau de qualification de donnees et famille d'instrument THREDDS Serveur de donnees grillees (netCDF) Apache/Python Serveur web dap2csv dap2graph DB-oceano • redondance des metadonnees dans le schema « md-diffusion » • mise a plat des series de donnees en fichier netCDF schema md-diffusion Optimisations pour la volumetrie Apache Tomcat Serveur web DB-oceano fichiers netCDF organises en series fichier netCDF representant un cycle de mesure Importation GET sos?request=DescribeSensor Administration, traitement par les oceanographes Remerciements • Au pole Informatique Scientifique et Appui aux partenaires du Sud de la DSI de l'IRD qui a soutenu le projet dans le cadre de SPIRALES (Soutien aux Projets InfoRmAtiques dans Les Equipes Scientifiques) • Au reseau R&D 52°North pour ses avancees sur les standards Sensor Web Enablement (SWE). Le client web de ReefTEMPS est base sur leur client libre : ThinSweClient 2.0. • Aux societes Apside et Geomatys pour leur contribution aux developpements (respectivement DB-oceano et Constellation) GET csw GET wms?request=GetMap GET sos?request=DescribeSensor GET dap2csv