Larval dispersal of pearl oysters Pinctada margaritifera in the Gambier Islands (French Polynesia) and exploring options for adult restocking using in situ data and numerical modelling.

Black pearl farming is the second source of French Polynesia income after tourism, and Gambier Islands are the main farming sites. Gambier main lagoon contains several sub-lagoons critical for pearl oyster rearing and spat collecting (SC). The Rikitea lagoon, traditionally had good SC rates in the warm season which ensured steady supplies of oysters for black pearl production. However, since 2018, SC has abruptly decreased. To assess the factors affecting SC, Gambier lagoon hydrodynamics was investigated in 2019-2020 to calibrate a hydrodynamic model and simulate larval dispersal around the SC areas. The model shows the strong wind influence on larval dispersal and accumulation patterns and suggests that windy months in the warm season as it can occur during La Niña episodes can explain recent poor SC. Larval dispersal scenarios also informed on best locations to perform adult oyster restocking, a practice that can also enhance SC on the long term.

Seabird and reef conservation must include coral islands.

Tropical seabirds exert key roles in reef ecosystems but face growing threats from climate change, especially on coral reef islands (CRIs). Therefore, we advocate for a more comprehensive, global data exchange on CRIs and CRI-dependent seabirds and outline steps for improving their study and conservation.

A multivariate approach to synthetize large amount of connectivity matrices for management decisions: Application to oyster population restocking in the pearl farming context of Tuamotu Archipelago semi-closed atolls.

In applied ecology, numerical biophysical modelling allows running numerous simulations of spatial connectivity between source and destination locations. To characterize population connectivity, larval dispersal and resulting connectivity matrices can be computed for various forcing conditions of wind, density of spawners, or pelagic larval durations. Here, we investigate a methodology to synthetize meaningfully all numerical experiments performed for three atoll lagoons in the Tuamotu Archipelago pearl farming context. The objective is to identify the best restocking locations that consistently maximize the spread of pearl oyster larval dispersal, considering all forcing conditions. A multivariate generic approach is used to process and synthesize time-series of connectivity matrices and identify afterward with contextual criteria the spawning locations that match a variety of specific connectivity, logistical and ecological criteria. Similar synthesis of large volume of connectivity matrices will likely gain momentum considering the increasing use of numerical models for applied science and population management.

Natural stocks of Pinctada margaritifera pearl oysters in Tuamotu and Gambier lagoons: New assessments, temporal evolutions, and consequences for the French Polynesia pearl farming industry.

Knowledge of the status of the black-lipped pearl oyster Pinctada margaritifera populations is critical for the sustainability of the French Polynesia black pearl farming industry. Indeed, this activity relies on collection of spat settling out of the water column, which is inherently related to the abundance of in situ benthic stocks and their reproductive capacities. From surveys performed between 2016 and 2021, we present new stock assessments of natural wild oyster populations from four contrasted pearl farming lagoons (Gambier, Takapoto, Raroia, Takume). Also using Ahe atoll historical data, we first highlight how results vary with the methods (Direct, Zonal and Cokriging) used to scale in situ density measurements to lagoon-scale stocks. Takapoto and Gambier populations were also previously surveyed at least twice since the 1980s, allowing to demonstrate with field data clear changes in stock distributions and population structures. The consequences of our findings are discussed to provide recommendations for stock monitoring and management in the future.

Remote sensing provides new insights on phytoplankton biomass dynamics and black pearl oyster life-history traits in a Pacific Ocean deep atoll.

Thus far, no long-term in situ observation of planktonic biomass have been undertaken to optimize the black-lip pearl oyster aquaculture in the remote Tuamotu atolls. The feasibility of using data from the OLI sensor onboard Landsat-8 satellite to determine chlorophyll a concentrations (Chla) in a deep atoll, Ahe, was then assessed over the 2013-2021 period using 153 images. Validations with in situ observations were satisfactory, while seasonal and spatial patterns in Chla were evidenced within the lagoon. Then, a bioenergetic modelling exercise was undertaken to estimate oyster life-history traits when exposed to the retrieved Chla. The outputs provide spatio-temporal variations in pelagic larval duration (11.1 to 30.6 days), time to reach commercial size (18.8 to 45.3 months) and reproductive outputs (0.5 to 1.7 event year-1). This first study shows the potential of using remote sensing to monitor the trophic status of deep pearl farming lagoons and help aquaculture management.

Periodicity of wave-driven flows and lagoon water renewal for 74 Central Pacific Ocean atolls.

French Polynesia atolls are spread on a vast 2300 by 1200 km Central Pacific Ocean area exposed to spatially and temporally dependent wave forcing. They also have a wide range of closed to open morphologies and several have been suitable to develop from black-lipped pearl oysters a substantial pearl farming activity in the past 30 years, representing nowadays the 2nd source of income for French Polynesia. Considering here only the component of lagoon renewal that is driven by waves, we investigate for 74 atolls different lagoon renewal metrics using 20 years of wave model data at 0.05° spatial resolution. Wavelet spectral analyses highlight that atolls, even in close vicinity, can be exposed to different and characteristic periodicities in wave-driven flows and water renewal. These characteristics are discussed in relation to pearl farming atolls, including atolls known to be efficient oyster spat producers, a critical activity for pearl farming sustainability.

The MANA (MANagement of Atolls, 2017-2022) project for pearl oyster aquaculture management in the Central Pacific Ocean using modelling approaches: Overview of first results.

This editorial presents results of the MANA (MANagement of Atolls) project compiled in the form of a Marine Pollution Bulletin collection of 14 articles. MANA is a project funded by the French Agence National pour la Recherche that specifically addresses the development of knowledge and management tools for pearl farming atolls, with a focus on the spat collecting activity in French Polynesia. The 14 papers cover the range of thematic tasks described in the initial project, including atoll geomorphology and bathymetry, climate forcing, atoll lagoon and rim hydrodynamics, typology of atolls, evaluation of remote sensing data for monitoring atoll lagoons, and development of numerical models and spatially-explicit tools that altogether have contributed to the applied objectives. In addition, this editorial draws an update on the pearl farming industry in French Polynesia with the latest statistics, and discusses the next targeted priorities for research programs focusing on pearl farming atolls.

A systematic prioritization approach for identifying suitable pearl oyster restocking zones following a mass mortality event in Takaroa Atoll, French Polynesia.

Oyster farming for black pearl production is central in French Polynesia. It is the second source of national income and provides substantial job opportunities, notably in remote atolls. However, this sector has been undermined by successive crises, such as mass-mortalities of wild and farmed oyster stocks that have impacted entire lagoons. An option to revive the activity consists of reintroducing oysters in strategic benthic locations selected to maximize reproduction and dispersal of larvae throughout the lagoon, hence promoting recolonization and spat collection for farming. For Takaroa, a Tuamotu atoll recently impacted by mortalities, a systematic prioritization approach identified these restocking sites, using environmental and socio-economic criteria such as: location of suitable habitats for oyster settlement, larval connectivity estimated from hydrodynamic circulation model, farming waste accumulation, and opportunity cost to fishers and farmers who lose access to restocking areas. This approach provides managers with a portfolio of restocking options.

Nation-wide hierarchical and spatially-explicit framework to characterize seagrass meadows in New-Caledonia, and its potential application to the Indo-Pacific.

Despite their ecological role and multiple contributions to human societies, the distribution of Indo-Pacific seagrasses remains poorly known in many places. Herein, we outline a hierarchical spatially-explicit assessment framework to derive nation-wide synoptic knowledge of the distribution of seagrass species and communities. We applied the framework to New Caledonia (southwest Pacific Ocean) and its 36,200 km2 of reefs and lagoons. The framework is primarily field-based but can leverage various habitat maps derived from remote sensing. Field data collection can be stratified by map products and retrospectively contribute to developing new seagrass distribution maps. Airborne and satellite remote sensing alone do not allow for the spatial generalisation of the finest attributes (species distribution and types of seagrass beds), but staged stratified field sampling provides synoptic views of these attributes. Using three examples, we discuss how the hierarchical and spatial information generated from this framework's application can inform conservation and management objectives.

Tide and wave driven flow across the rim reef of the atoll of Raroia (Tuamotu, French Polynesia).

The currents flowing across the rim of the atoll of Raroia were investigated with a 1 year-long dataset of wave, water level and currents. Offshore waves break on the edge of the reef outside the atoll's rim and drive current into the lagoon, through the shallow hoa that cut across the rim. The additional water volume generated by this wave driven flow induces an elevation of water level throughout the atoll's lagoon and is evacuated back into the open ocean through a deep reef pass. The water level inside the atoll is also driven by astronomical tides, which enter the lagoon thought the reef pass, after undergoing a ~50% decrease in amplitude and a ~4 hour lag. Using a simple parametric model with three calibrated coefficients, we show that currents across the atoll's rim can be estimated as a function of the offshore wave conditions and the water level difference between the ocean and the lagoon.

Seagrass ecosystems of the Pacific Island Countries and Territories: A global bright spot.

Seagrass ecosystems exist throughout Pacific Island Countries and Territories (PICTs). Despite this area covering nearly 8% of the global ocean, information on seagrass distribution, biogeography, and status remains largely absent from the scientific literature. We confirm 16 seagrass species occur across 17 of the 22 PICTs with the highest number in Melanesia, followed by Micronesia and Polynesia respectively. The greatest diversity of seagrass occurs in Papua New Guinea (13 species), and attenuates eastward across the Pacific to two species in French Polynesia. We conservatively estimate seagrass extent to be 1446.2 km2, with the greatest extent (84%) in Melanesia. We find seagrass condition in 65% of PICTs increasing or displaying no discernible trend since records began. Marine conservation across the region overwhelmingly focuses on coral reefs, with seagrass ecosystems marginalised in conservation legislation and policy. Traditional knowledge is playing a greater role in managing local seagrass resources and these approaches are having greater success than contemporary conservation approaches. In a world where the future of seagrass ecosystems is looking progressively dire, the Pacific Islands appears as a global bright spot, where pressures remain relatively low and seagrass more resilient.

Seagrass ecosystem contributions to people's quality of life in the Pacific Island Countries and Territories.

Seagrass ecosystems provide critical contributions (goods and perceived benefits or detriments) for the livelihoods and wellbeing of Pacific Islander peoples. Through in-depth examination of the contributions provided by seagrass ecosystems across the Pacific Island Countries and Territories (PICTs), we find a greater quantity in the Near Oceania (New Guinea, the Bismarck Archipelago and the Solomon Islands) and western Micronesian (Palau and Northern Marianas) regions; indicating a stronger coupling between human society and seagrass ecosystems. We also find many non-material contributions historically have been overlooked and under-appreciated by decision-makers. Closer cultural connections likely motivate guardianship of seagrass ecosystems by Pacific communities to mitigate local anthropogenic pressures. Regional comparisons also shed light on general and specific aspects of the importance of seagrass ecosystems to Pacific Islanders, which are critical for forming evidence-based policy and management to ensure the long-term resilience of seagrass ecosystems and the contributions they provide.

Understanding connectivity of pearl oyster populations within Tuamotu atoll semi-closed lagoons: Cumulative insight from genetics and biophysical modelling approaches.

Connectivity affects species demography, (meta)population dynamics, evolution, phylogeny and biogeography. Various methodological approaches are applied to measure connectivity. Biophysical modelling can explore systematically the influence of atmospheric, oceanic and ecological forcing, while genetics measures connectivity patterns within the sampling strategy limit. In the Pacific Ocean pearl farming lagoons, the activity relies on spat collecting of the black lipped pearl oyster Pinctada margaritifera occurring after the larval dispersal phase, which follows spawning from wild or farmed populations. Biophysical 3D modelling and genomic studies have both separately brought insights on within-lagoon connectivity and on the origin of spats. Here, we combined previous genetics results with new realistic biophysical modelling scenarios to elucidate connectivity in Ahe Atoll lagoon. When combined, we identified the weather sequence likely explaining the realized connectivity observations. We discuss the strengths, weaknesses, opportunities and threats of combining these two approaches considering specific pearl farming demographic connectivity questions.

An appraisal of systematic conservation planning for Pacific Ocean Tropical Islands coastal environments.

Systematic Conservation Planning (SCP) offers concepts and toolboxes to make spatial decisions on where to focus conservation actions while minimizing a variety of costs to stakeholders. Thirty-four studies of Pacific Ocean Tropical Islands were scrutinized to categorize past and current types of applications. It appeared that scenarios were often built on a biodiversity representation objective, opportunity costs for fishers was the most frequent cost factor, and an evolution from simple to sophisticated scenarios followed the need to maximize resilience and connectivity while mitigating climate change impacts. However, proxies and models were often not validated, pointing to data quality issues. Customary management by local communities motivated applications specific to the Pacific region, but several island features remained ignored, including invertebrate fishing, ciguatera poisoning and mariculture. Fourteen recommendations are provided to enhance scenarios' robustness, island specificities integration, complex modelling accuracy, and better use of SCP for island management.

Correction: Reisser, C.M.O. et al. Population Connectivity and Genetic Assessment of Exploited and Natural Populations of Pearl Oysters within a French Polynesian Atoll Lagoon. Genes 2020, 11, 426.

The authors wish to make the following corrections to this paper [...].

Monitoring pearl farming lagoon temperature with global high resolution satellite-derived products: An evaluation using Raroia Atoll, French Polynesia.

Temperature is important for pearl oyster reproduction, pelagic larval duration, and growth in the context of pearl farming, but has seldom been monitored over long periods in remote atolls. To test if satellite-derived Sea Surface Temperature (SST) could provide a solution, two daily global SST products were compared with 18 high-precision loggers deployed during 10-months in the wide Raroia atoll (Tuamotu Archipelago, French Polynesia). The Multi-scale-Ultra-high-Resolution (MUR) SST was better correlated with lagoon temperature (r > 0.97) than the Global-Foundation-Sea-Surface-Temperature-Analysis (G1SST) SST (r < 0.94). Differences between observations and MUR SST ranged between -0.75 °C and + 1.12 °C and were influenced by seasons and locations, depth, and hours of measurements. Within this uncertainty range, simulations using a Dynamic Energy Budget model predicted similar life traits of oysters. Therefore, MUR SST appears suitable to monitor lagoon temperature in wide atolls, model oyster population dynamics and assist pearl oyster research and management.

Population Connectivity and Genetic Assessment of Exploited and Natural Populations of Pearl Oysters within a French Polynesian Atoll Lagoon.

In French Polynesia, the production and exportation of black pearls through the aquaculture of the black-lip pearl oyster Pinctada margaritifera provide the second largest economic income for the country after tourism. This industry entirely relies on the collection of natural spats from few highly recruiting lagoons. In recent years, pearl oyster producers have experienced variable success rates in spat collection, with significant spatial and temporal variability in spat supply, driving uncertainty in the future of pearl production. This study combines, for the first time in a farmed lagoon, genetic (SNPs), demographic (sex ratio, age), and biophysical data (larval dispersal modelling) to shed new light on population dynamics, connectivity, and spat recruitment in Ahe Atoll, a well-studied pearl farming site. Our results indicate that the geographical structuring of the natural populations and the contribution of both natural and exploited stocks to the production of spats result from the interaction of hydrodynamic features, life history traits and demographic parameters: the northeastern natural populations are older, not well connected to the southwestern natural populations and are not replenished by larvae produced by adjacent exploited populations. Moreover, we observe that the exploited populations did not contribute to larval production during our experiment, despite a sampling period set during the most productive season for spat collection. This is likely the result of a strong male bias in the exploited populations, coupled with a sweepstakes reproductive strategy of the species. Our results warrant further investigations over the future of the northeastern older natural populations and a reflection on the current perliculture techniques.

Checklist of the marine and estuarine fishes of New Ireland Province, Papua New Guinea, western Pacific Ocean, with 810 new records.

A checklist of the marine and estuarine fishes of New Ireland Province is presented, with special emphasis on Kavieng District, combining both previous and new records. After the recent KAVIENG 2014 expedition, a total of 1325 species in 153 families were recorded from the region. The largest families are the Gobiidae, Pomacentridae, Labridae, Serranidae, Apogonidae, Lutjanidae, Chaetodontidae, Blenniidae, Carangidae, Acanthuridae, Scaridae, Holocentridae, Syn-gnathidae, Lethrinidae and Scorpaenidae. A total of 810 fish species (61.1 % of the total marine and estuarine fish fauna) are recorded from New Ireland for the first time.The fish fauna of New Ireland includes 142 species in transitional waters and 1264 species in marine habitats, and 54 species species in freshwater habitats. Zoogeographically, 1179 species have a wide distribution range, most frequently a broad Indo-West Pacific distribution. Among the remaining species, just 12 are endemic to New Ireland.

Challenges in rendering Coral Triangle habitat richness in remotely sensed habitat maps: The case of Bunaken Island (Indonesia).

The Coral Triangle is the epicenter of marine biodiversity, yet the numbers of habitats that can be found on coral reefs remain poorly described. First surveys for habitat mapping in Indonesia revealed a high number of habitats (>150) even for structurally simple reefs. To be able to represent all these habitats, typical habitat mapping procedures and performances are poorly effective even using very high resolution satellite images. Using Bunaken Island (North Sulawesi, Indonesia) as a case study, we devised a way to maintain all the in situ habitat information in remote sensing habitat map products without loss and with mapping procedures based on photo-interpretation. The result is a product which is consistent with a per-polygon fuzzy classification. As such, it is a complex product that meets our habitat representation goal, but its complexity can also limit its immediate use by managers and conservation planners when analyses per habitat are needed.

Consequences of an uncertain mass mortality regime triggered by climate variability on giant clam population management in the Pacific Ocean.

Despite actions to manage sustainably tropical Pacific Ocean reef fisheries, managers have faced failures and frustrations because of unpredicted mass mortality events triggered by climate variability. The consequences of these events on the long-term population dynamics of living resources need to be better understood for better management decisions. Here, we use a giant clam (Tridacna maxima) spatially explicit population model to compare the efficiency of several management strategies under various scenarios of natural mortality, including mass mortality due to climatic anomalies. The model was parameterized by in situ estimations of growth and mortality and fishing effort, and was validated by historical and new in situ surveys of giant clam stocks in two French Polynesia lagoons. Projections on the long run (100 years) suggested that the best management strategy was a decrease of fishing pressure through quota implementation, regardless of the mortality regime considered. In contrast, increasing the minimum legal size of catch and closing areas to fishing were less efficient. When high mortality occurred due to climate variability, the efficiency of all management scenarios decreased markedly. Simulating El Niño Southern Oscillation event by adding temporal autocorrelation in natural mortality rates increased the natural variability of stocks, and also decreased the efficiency of management. These results highlight the difficulties that managers in small Pacific islands can expect in the future in the face of global warming, climate anomalies and new mass mortalities.