Assessing the reproducibility of coral oxygen and carbon isotope time series from Fiji and Tonga and their application to the reconstruction of South Pacific Convergence Zone movements since the mid-1800s

A major feature affecting the hydrology of the southern hemisphere is the South Pacific Convergence Zone (SPCZ); a band of high rainfall extending southeastward from the Western Pacific Warm Pool (WPWP). It is a key source of atmospheric water vapor and latent heating. While it is clear that the SPCZ plays a fundamental role in Earth\u27s climate, little is known about the patterns and mechanisms responsible for interannual to century-scale changes in its position and how it may respond to global climate change. This research was focused on developing precisely dated, coral-derived geochemical records of SPCZ variability over the last 200 years. A unique regional coral network consisting of five coral time-series from Fiji (cores 1F, AB, FVB1, FVB2 and 16F) and three from Tonga (cores TH1, TNI2 and TF1) was used to investigate the reproducibility of coral δ18O and δ13C records to create Fiji and Tonga coral δ 18O and δ13C composite records for paleoclimatic reconstruction. Using at least three coral δ18O records from the same area is sufficient to obtain a statistically reliable signal for climate reconstruction. Fiji and Tonga coral δ18O composites at annual resolution are a suitable proxy for past sea surface salinity (SSS) variability. The Fiji coral core δ13C composite can be used to reconstruct the oceanic δ13C variability of the dissolved inorganic carbon (DIC) reservoir. The long-term decreasing trend in δ13C Fiji-DIC could be considered a representation of the well-known Suess effect. This study discusses interannual, decadal/interdecadal and long-term trends in the SPCZ salinity front movements, which appear to reflect mostly changes in water mass advection, rather than changes in precipitation linked with SPCZ displacement. Fiji and Tonga long term freshening trends suggest that the SPCZ is intensifying and/or expanding. The difference in salinity between Fiji and Tonga indicates that Fiji is freshening at a more rapid rate than Tonga. This study concludes that an intensification of the eastward flowing Subtropical Counter Current during the 20th century appears to be bringing relatively colder and saltier waters to Tonga; those conditions counterbalance the effects of the warmer and fresher conditions induced by the SPCZ expansion

Saving our marine archives

A concerted effort has begun to gather and preserve archives of marine samples and descriptive data, giving scientists ready access to insights on ancient environments

The Suess effect in Fiji coral delta C-13 and its potential as a tracer of anthropogenlc CO2 uptake

In the context of increasing anthropogenic CO2 emissions, determining the rate of oceanic CO2 uptake is of high interest. Centennial-scale changes in delta C-13 of the surface water dissolved inorganic carbon (DIC) reservoir have been shown to be influenced by the carbon isotopic composition of atmospheric CO2. However, the availability of direct oceanic delta C-13 measurements is limited and methods for reconstructing past delta C-13 variability of the oceanic DIC are needed. Geochemical reconstructions of DIC variability can help in understanding how the ocean has reacted to historical changes in the carbon cycle. This study explores the potential of using temporal variations in delta C-13 measured in five Fijian Porites corals for reconstructing oceanic delta C-13 variability. A centennial-scale decreasing delta C-13 trend is observed in these Fiji corals. Other studies have linked similar decreasing delta C-13 trends to anthropogenic changes in the atmospheric carbon reservoir (the "C-13 Suess effect"). We conclude that solar irradiance is the factor influencing the delta C-13 cycle on a seasonal scale, however it is not responsible for the centennial-scale decreasing delta C-13 trend. In addition, variations in skeletal extension rate are not found to account for centennial-scale delta C-13 variability in these corals. Rather, we found that water depth at which a Fijian Porites colony calcifies influences both delta C-13 and extension rate mean values. The water depth-delta C-13 relationship induces a dampening effect on the centennial-scale decreasing delta C-13 trend. We removed this "water depth effect" from the 813C composite, resulting in a truer representation of delta C-13 variability of the Fiji surface water DIC (delta C-13(Fiji-DIC)). The centennial-scale trend in this Fiji coral composite delta C-13(Fiji-DIC) time-series shares similarities with atmospheric delta C-13(CO2), implicating the C-13 Suess effect as the source of the this coral delta C-13 trend. Additionally, our study finds that the delta C-13 variability between the atmosphere and the ocean in this region is not synchronous; the coral delta C-13 response is delayed by similar to 10 years. This agrees with the previously established model of isotopic disequilibrium between atmospheric delta C-13(CO2) and oceanic surface water DIC. (c) 2012 Elsevier B.V. All rights reserved

Sensitivity of newly transformed juveniles of the freshwater pearl mussel: Margaritifera margaritifera to acute toxicity of a wide range of contaminants

The freshwater pearl mussel (FWPM) Margaritifera margaritifera is a bivalve mollusk critically endangered in Europe. There is a special concern about the conservation of this species, but little is known about its sensitivity to environmental pollution. Here, acute toxicity tests were conducted at 16°C according to a standard guide for conducting toxicity tests on freshwater mussels (ASTM international E2455), in order to assess toxicity thresholds for arsenic (As), aluminum (Al), cadmium (Cd), copper (Cu), nickel (Ni), nitrates (NO3−), and orthophosphates (PO43−) on newly transformed juveniles of M. margaritifera. The comparison with toxicity data for other newly transformed freshwater mussel juveniles from the same family and superfamily, Margaritiferidae and Unionidae, showed that FWPM juveniles were the most sensitive species to NO3−, among the most sensitive species to Ni, the least sensitive species to Cd, and showed an intermediate sensitivity to Cu compared to other freshwater mussels. This study is the first to provide toxicity thresholds for several pollutants on newly transformed juveniles of the FWPM. This brings new knowledge on its sensitivity to environmental pollution that could be helpful data for conservation strategies and these findings represent the first window for further complex studies

Case Report:Pregnancy and birth in a mild phenotype of Alström syndrome

Background: Alstrom syndrome (AS) is an ultrarare multisystemic progressive disease caused by autosomal recessive variations of the ALMS1 gene (2p13). AS is characterized by double sensory impairment, cardiomyopathy, childhood obesity, extreme insulin resistance, early nonalcoholic fatty liver disease, renal dysfunction, respiratory disease, endocrine and urologic disorders. In female AS patients, hyperandrogenism has been described but fertility issues and conception have not been investigated so far. Case: This case report describes the spontaneous conception, pregnancy, and birth in a 27-year-old woman with AS, characterized by a mild phenotype with late onset of visual impairment, residual perception of light, and hypertension. Before pregnancy, menses were regular with increased levels of dihydrotestosterone and androstanediol glucuronide in the follicular phase, and the ovaries and endometrium were normal during vaginal ultrasound. A thorough clinical follow-up of the maternal and fetal conditions was carried out. A weight gain of 10 kg during pregnancy was recorded, and serial blood and urine tests were all within the normal range, except for mild anemia. The course of pregnancy was uneventful up to 34 weeks of gestation when preeclampsia developed with an abnormally high level of blood pressure and edema in the lower limbs. At 35 weeks + 3 days of gestation, an urgent cesarean section was performed, and a healthy male weighing 1,950 g was born. Histological examination of the placenta showed partial signs of flow obstruction, limited abruption areas, congested fetal vessels and villi, and a small single infarcted area. Conclusion: The present case demonstrates for the first time that conceiving is possible for patients with ALMS. Particular attention should be given to the management of AS systemic comorbidities through the course of pregnancy

Impact of nickel mining in New Caledonia on marbled eels Anguilla marmorata

International audienceNew Caledonia is particularly affected by nickel open pit mining activities because of the presence of ultramafic soils rich in metal trace elements. The nickel particles dispersed by atmospheric transport and soil erosion during the excavation of nickel will end up by deposition or leaching in aquatic ecosystems where they may be bioaccumulated by living organisms in the rivers downstream the mines. Despite alarming freshwater metals concentrations, no study investigated the level of their bioaccumulation in eels living downstream mining sites, and if high bioaccumulation levels occur, the potential consequences on eel's health. The aim of this study was to determine how eels Anguilla marmorata are impacted in situ by metal concentrations issued from mining activity by measuring: morphometric parameters; metal concentrations in tissues and organs and transcription levels of target genes encoding proteins involved in several metabolic key functions. Among organs, liver was found to be the most affected by mining with average nickel concentrations of 5.14 mg/kg versus 1.63 mg/kg for eel liver away from mines leading to dysregulation of numerous genes involved in oxidative stress, DNA repair, apoptosis, reproduction and both lipid and mitochondrial metabolisms. This study should allow us to define in an integrated way if metals released by mining activities influence metals bioaccumulation in eels and induce biological effects

Influence of a hydroelectric dam on fish mercury contamination along the Sinnamary River (French Guiana)

International audienceThe Petit Saut hydroelectric dam and the upstream and downstream areas of the Sinnamary River in French Guiana (Amazon basin) have been studied from 1993 to 2020. The nearly thirty-years-long study of the monitoring of total mercury concentration in fish and the physicochemical survey of the environment made it possible to demonstrate the impact of the flooding of the forest and the role of the hydroelectric dam on the methylation of mercury. Results show that the physicochemical modifications generated by the construction of the dam led to a significant production of methylmercury (MeHg) in the anoxic part of the reservoir and downstream of the river leading to a strong spatio-temporal impact of the dam. Seven species of fishes are studied and their mercury concentrations vary according to many parameters: fish diet, position in the water column, site, lake oxycline level and time

Volcanisme et tectonique découverts le long de l’archipel des Comores entre l’Afrique et Madagascar

International audienceGeophysical and geological data from the North Mozambique Channel acquired during the 2020–2021 SISMAORE oceanographic cruise reveal a corridor of recent volcanic and tectonic features 200 km wide and 600 km long within and north of Comoros Archipelago. Here we identify and describe two major submarine tectono-volcanic fields: the N’Droundé province oriented N160°E north of Grande-Comore Island, and the Mwezi province oriented N130°E north of Anjouan and Mayotte Islands. The presence of popping basaltic rocks sampled in the Mwezi province suggests post-Pleistocene volcanic activity. The geometry and distribution of recent structures observed on the seafloor are consistent with a current regional dextral transtensional context. Their orientations change progressively from west to east (»N160°E, »N130°E, »EW). The volcanism in the western part appears to be influenced by the pre-existing structural fabric of the Mesozoic crust. The 200 km wide and 600 km-long tectono-volcanic corridor underlines the incipient Somalia–Lwandle dextral lithospheric plate boundary between the East-African Rift System andMadagascar.Des données géophysiques et géologiques ont été acquises lors de la campagne océanographique SISMAORE (2020–2021). Deux grands champs tectono-volcaniques sous-marins ont été découverts tout le long et principalement au nord de l’archipel des Comores : la province N’Droundé orientée N160°E au nord de Grande-Comore, et la province Mwezi orientée N130°E au nord d’Anjouan-Mayotte où des roches basaltiques de type popping-rocks suggèrent une activité volcanique possiblement actuelle à pléistocène. La géométrie et la distribution des structures récentes sont cohérentes avec un contexte régional actuel transtensif dextre. Leurs orientations évoluent d’Ouest en Est (»N160°E, »N130°E, »EW), suggérant pour la partie occidentale, une mise en place du volcanisme influencée par la structuration crustale préexistante. Le corridor tectono-volcanique de 200 km de large et de 600 km de long dessine une limite de plaque lithosphérique Somalie-Lwandle immature en décrochante dextre entre le système du rift est-africain et Madagascar

Discovery of recent volcanic and tectonic provinces along the Comoros archipelago (North Mozambique Channel) ─ Preliminary results of the SISMAORE oceanographic cruise (ANR-COYOTES project)

International audienceA new geophysical and geological dataset, acquired during the SISMAORE oceanographic campaign (2020-2021), reveals a recent tectonic and volcanic deformation distributed over 130km in the abyssal plain that permit to unravel the unconstrained lithospheric plate boundaries between Lwandle and Somalia blocks and the controversial origin of the Comoros Archipelago.Two recent submarine volcanic and tectonic provinces of 5000km2, with a large number of varied volcanic structures and faults, are unveiled: the N160° N'Droundé (north of Grande-Comore) and the N130° Mwezi provinces (north of Anjouan/Mayotte). Dredged Mwezi rocks suggest a recent gas-rich volcanic activity. It is also identified a recent N130° trending volcanic structures (cones, lava flows, eruptive fissures) between Anjouan and Mayotte in agreement with the presence of shallow earthquakes, and also recent lava flows on the southern flanks of the Grande Comore and Moheli. Southwards, recent sedimentation is important with no volcanism and deformation. A consistent sedimentary thickness covers the flanks of Mayotte and Anjouan and the presence of large areas of submarine instability at the foot and on the slope of the islands is confirmed.These first observations suggest a transtensional deformation, accommodated by dextral strike-slip motion, strongly influenced by pre-existing structuration of the Mesozoic oceanic crust and by the East Africa Rift system. The 130km wide zone of intraplate deformation characterizes an immature lithospheric plate boundary of the north Lwandle block