To understand the possible influence of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on the deep sea, as well as the geochemical behavior and transport of radionuclides, ¹³⁴Cs, ¹³⁷Cs, ²³⁹, ²⁴⁰Pu, ²⁴¹Pu, and ²³⁷Np were measured in the abyssal sediments of the Northwest Pacific (NWP) and Central Equatorial Pacific (CEP) Ocean. Data on the characteristics of these sediments obtained after the FDNPP accident are extremely rare, especially in the NWP subtropical gyre (NPSG) region. FDNPP-derived radio-Cs (¹³⁴Cs, ¹³⁷Cs) arrived at the open sea floor of the NWP before 2018 but was only found in the Kuroshio-Oyashio Extension (KOE) region. No FDNPP-derived Pu was detected in the abyssal sediments of the NWP or CEP. Pu in the NWP mainly originated from global fallout and the Pacific Proving Ground (PPG) close-in fallout, except for at station WP1 (39°N in the KOE region), where an abnormal but non-FDNPP-derived Pu signal was detected. Pu in the eastern CEP sediment was less affected by the PPG close-in fallout from the Marshall Islands and was mainly derived from global fallout, with some close-in fallout from the Johnston Atoll test. The KOE region was the area most affected by PPG close-in fallout Pu via Kuroshio transport, while the lowest inventories of ²³⁹⁺²⁴⁰Pu and ²³⁷Np were found in the NPSG region due to its oligotrophic environment. The ²³⁷Np originated from the same source as Pu, and the latitudinal pattern of ²³⁷Np was consistent with that of Pu. Station SS (in the marginal sea of the NWP) contained high ²³⁷Np/²³⁹Pu atom ratios in the deeper layers of sediment and had a ²³⁷Np depth profile opposite that of the ²³⁹⁺²⁴⁰Pu profile, compared to other stations; these differences are mainly attributed to differences in the behaviors of ²³⁷Np and ²³⁹Pu.

Perfluorinated alkyl substances (PFASs) are global, persistent, and toxic contaminants. We assessed PFAS concentrations in green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles from the North Pacific. Fifteen compounds were quantified via liquid chromatography tandem mass spectrometry from 62 green turtle and 6 hawksbill plasma samples from Hawai’i, Palmyra Atoll, and the Northern Marianas Islands. Plasma from 14 green turtles severely afflicted with fibropapillomatosis, and eggs from 12 Hawaiian hawksbill nests from 7 females were analyzed. Perfluorooctane sulfonate (PFOS) predominated in green turtle plasma; perfluorononanoic acid (PFNA) predominated in hawksbill tissues. Concentrations were greater in hawksbill than green turtle plasma (p < 0.05), related to trophic differences. Green turtle plasma PFOS concentrations were related to human populations from highest to lowest: Hawai’i, Marianas, Palmyra. Influence on fibropapillomatosis was not evident. PFASs were maternally transferred to hawksbill eggs, with decreasing concentrations with distance from airports and with clutch order from one female. A risk assessment of PFOS showed concern for immunosuppression in Kailua green turtles and alarming concern for hawksbill developmental toxicity. Perfluoroundecanoic (PFUnA) and perfluorotridecanoic (PFTriA) acid levels were correlated with reduced emergence success (p < 0.05). Studies to further examine PFAS effects on sea turtle development would be beneficial.

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.

Pearl farming sustainability in South Central Pacific (SCP) atolls strongly depends on water quality and renewal. These factors are partly controlled by the wave conditions that impact the lagoon circulation. To characterize the wave conditions around 83 SCP atolls including those hosting pearl farming activities, we used 18 years of WaveWatchIII simulation with a grid refined from 50 to 5 km resolution. Three regional wave regimes are statistically identified: two associated with long distant swells originating from mid-latitude storms, and one with local trade winds. All regimes occur with a relatively high frequency (22–44%), but with a marked seasonality. Wave conditions are also strongly modified locally during their propagation between the archipelagoes. Western and southern isolated atolls generally have a single regime all around their rims. In contrast, central Tuamotu atolls experience different regimes depending on their levels of protection. These results help understanding atoll hydrodynamics, which has implications for their management.

This study presents the first report on the concentration of trace elements (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) in the blood and egg fractions of green turtles from Rocas Atoll, a pristine nesting site in NE Brazil. The highest concentrations of all elements were in the blood or shell samples. In order, iron, Zn, Cu, Al and As presented the highest concentrations in all tissues. The nonessential trace elements were below the limit of detection for more than 50% of the yolk (Al, Cd and Pb) and albumen samples (Al, As, Ba, Cd and Pb). This study will serve as a baseline reference for future monitoring of the ecotoxicology of breeding green turtles in the southwestern Atlantic Ocean.

Microplastics are recognized as a growing threat for the marine environment that may even affect areas generally considered pristine. In this work we surveyed the microplastic contamination in the Faafu Atoll (Maldives, Indian Ocean) across twelve sampling station, located either inside or outside the reef rim. Sediments and seawater samples were collected. Despite the remoteness of the atoll, the scarce local population and low touristic annual afflux, the detected average abundance were 0.32 ± 0.15 particles/m3 in the surface water and 22.8 ± 10.5 particles/m2 in the beach sediments. Polymers identified through Fourier-Transform Infrared spectroscopy were mostly polyethylene, polypropylene, polystyrene, polyvinylchloride, polyethyleneterephtalate, and polyamide. Elastomeric residues and charred microparticles were also found. In particular, the charred microparticles were prevalently located nearby the inhabited island and they might be considered a peculiarity of the area, related to local practice of burning plastic waste at the shoreline.

The Chagos Archipelago is geographically remote and isolated from most direct anthropogenic pressures. Here, we quantify the abundance and diversity of decapod crustaceans inhabiting dead coral colonies, representing a standardised microhabitat, across the Archipelago. Using morphological and molecular techniques we recorded 1868 decapods from 164 nominal species within 54 dead coral colonies, but total species estimates (Chao1 estimator) calculate at least 217 species. Galatheids were the most dominant taxa, though alpheids and hippolytids were also very abundant. 32% of species were rare, and 46% of species were found at only one atoll. This prevalence of rarer species has been reported in other cryptofauna studies, suggesting these assemblages maybe comprised of low-abundance species. This study provides the first estimate of diversity for reef cryptofauna in Chagos, which will serve as a useful baseline for global comparisons of coral reef biodiversity.

Six marine biota species were collected from the Xuande Atoll, South China Sea to investigate the bioaccumulation of dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) and dechlorane plus (DP). Pike conger (Muraenesox talabonoides) had the highest concentrations of halogenated organic pollutants (HOPs) among the six marine biota species. DDTs were the predominant HOPs, followed by PCBs and PBDEs, with minor contributions of DBDPE and DP. Twenty-one percent of samples had ratios of (DDE+DDD)/ΣDDTs lower than 0.5, implying the presence of fresh DDT inputs in the environment of the Xuande Atoll. The biomagnification factor values for DDTs, PCBs, PBDEs and DP were higher than 1, suggesting biomagnification of these contaminants in the marine food chains. Consumption of seafood from the Xuande Atoll might not subject local residents in the coastal areas of South China to health risks as far as HOPs are concerned.

Studies on remote, uninhabited, near-pristine reefs have revealed surprisingly large populations of large reef fish. Locations such as the northwestern Hawaiian Islands, northern Marianas Islands, Line Islands, U.S. remote Pacific Islands, Cocos-Keeling Atoll and Chagos archipelago have much higher reef fish biomass than islands and reefs near people. Much of the high biomass of most remote reef fish communities lies in the largest species, such as sharks, bumphead parrots, giant trevally, and humphead wrasse. Some, such as sharks and giant trevally, are apex predators, but others such as bumphead parrots and humphead wrasse, are not. At many locations, decreases in large reef fish species have been attributed to fishing. Fishing is well known to remove the largest fish first, and a quantitative measure of vulnerability to fishing indicates that large reef fish species are much more vulnerable to fishing than small fish. The removal of large reef fish by fishing parallels the extinction of terrestrial megafauna by early humans. However large reef fish have great value for various ecological roles and for reef tourism.

Localised loss of live coral cover at Palmyra Atoll (central Pacific Ocean) has been attributed to increased temperature and/or sedimentation arising from alterations made to the lagoon system. It has been hypothesised that a causeway spanning the lagoon hinders water circulation, resulting in warmer and/or more turbid water flowing towards a site of high coral cover and diversity (Coral Gardens). Analyses of a multi-site and multi-year data set revealed no differences in mean temperature or turbidity values on either side of the causeway and provided no evidence of significantly warmer or more turbid water at Coral Gardens. We conclude that the putative decline in live coral cover cannot be attributed to the presence of the causeway and that proposed management actions involving modification to the causeway cannot achieve the conservation outcomes suggested of them.