Microbial taxa related to natural hydrogen and methane emissions in serpentinite-hosted hyperalkaline springs of New Caledonia.

The southeastern part of New Caledonia main island (Grande Terre) is the location of a large ophiolitic formation that hosts several hyperalkaline springs discharging high pH (∼11) and warm (<40°C) fluids enriched in methane (CH4) and hydrogen (H2). These waters are produced by the serpentinization of the ultrabasic rock formations. Molecular surveys had previously revealed the prokaryotic diversity of some of these New Caledonian springs, especially from the submarine chimneys of Prony Bay hydrothermal field. Here we investigate the microbial community of hyperalkaline waters from on-land springs and their relationships with elevated concentrations of dissolved H2 (21.1-721.3 µmol/L) and CH4 (153.0-376.6 µmol/L). 16S rRNA gene analyses (metabarcoding and qPCR) provided evidence of abundant and diverse prokaryotic communities inhabiting hyperalkaline fluids at all the collected springs. The abundance of prokaryotes was positively correlated to the H2/CH4 ratio. Prokaryotes consisted mainly of bacteria that use H2 as an energy source, such as microaerophilic Hydrogenophaga/Serpentinimonas (detected in all sources on land) or anaerobic sulfate-reducing Desulfonatronum, which were exclusively found in the most reducing (Eh ref H2 ∼ -700 mV) and the most H2-enriched waters discharging at the intertidal spring of the Bain des Japonais. The relative abundance of a specific group of uncultured Methanosarcinales that thrive in serpentinization-driven ecosystems emitting H2, considered potential H2-consuming methanogens, was positively correlated with CH4 concentrations, and negatively correlated to the relative abundance of methylotrophic Gammaproteobacteria. Firmicutes were also numerous in hyperalkaline waters, and their relative abundance (e.g., Gracilibacter or Dethiobacter) was proportional to the dissolved H2 concentrations, but their role in the H2 budget remains to be assessed. The prokaryotic communities thriving in New Caledonia hyperalkaline waters are similar to those found in other serpentinite-hosted high-pH waters worldwide, such as Lost City (North Atlantic) and The Cedars (California).

New fossil discoveries illustrate the diversity of past terrestrial ecosystems in New Caledonia.

New Caledonia was, until recently, considered an old continental island harbouring a rich biota with outstanding Gondwanan relicts. However, deep marine sedimentation and tectonic evidence suggest complete submergence of the island during the latest Cretaceous to the Paleocene. Molecular phylogenies provide evidence for some deeply-diverging clades that may predate the Eocene and abundant post-Oligocene colonisation events. Extinction and colonization biases, as well as survival of some groups in refuges on neighbouring paleo-islands, may have obscured biogeographic trends over long time scales. Fossil data are therefore crucial for understanding the history of the New Caledonian biota, but occurrences are sparse and have received only limited attention. Here we describe five exceptional fossil assemblages that provide important new insights into New Caledonia's terrestrial paleobiota from three key time intervals: prior to the submersion of the island, following re-emergence, and prior to Pleistocene climatic shifts. These will be of major importance for elucidating changes in New Caledonia's floristic composition over time.

Unravelling the nature of Waiparaconus, a pennatulacean (Cnidaria: Octocorallia) from the Late Mesozoic-Early Cainozoic of the Southern Hemisphere.

Enigmatic calcareous conical fossils have been known from marine Paleocene-Eocene sequences of New Zealand since the early 1870s. More recently, similar fossils have been recorded from both Late Cretaceous marine sequences of Western Australia, New Caledonia and Antarctica, and possibly from the Eocene of South America. The present paper extends the record to the late Cretaceous of New Caledonia. These remains are unlike any living taxa, and have been variously interpreted as molluscs (rudistid bivalves), cirripedes (stalked barnacles), annelids and inorganic structures. Assignation to the Cirripedia has been refuted by Buckeridge (1983, 1993), who proposed that the material would be better placed within the Cnidaria. We investigate this hypothesis in light of the New Caledonian material and by comparison with living gorgonians and pennatulaceans, and demonstrate that Waiparaconus is best placed within the Pennatulacea. Waiparaconus zelandicus varies in form somewhat, with 3 morphotypes defined and reinforced by geography. Comment is provided on the imperative to fit organic remains into known groups, with reflection on what may happen if taxa are left in insertae sedis.

Pleural mesothelioma in New Caledonia: associations with environmental risk factors.

BACKGROUND: High incidences of malignant mesothelioma (MM) have been observed in New Caledonia. Previous work has shown an association between MM and soil containing serpentinite. OBJECTIVES: We studied the spatial and temporal variation of MM and its association with environmental factors. METHODS: We investigated the 109 MM cases recorded in the Cancer Registry of New Caledonia between 1984 and 2008 and performed spatial, temporal, and space-time cluster analyses. We conducted an ecological analysis involving 100 tribes over a large area including those with the highest incidence rates. Associations with environmental factors were assessed using logistic and Poisson regression analyses. RESULTS: The highest incidence was observed in the Houaïlou area with a world age-standardized rate of 128.7 per 100,000 person-years [95% confidence interval (CI), 70.41-137.84]. A significant spatial cluster grouped 18 tribes (31 observed cases vs. 8 expected cases; p = 0.001), but no significant temporal clusters were identified. The ecological analyses identified serpentinite on roads as the greatest environmental risk factor (odds ratio = 495.0; 95% CI, 46.2-4679.7; multivariate incidence rate ratio = 13.0; 95% CI, 10.2-16.6). The risk increased with serpentinite surface, proximity to serpentinite quarries and distance to the peridotite massif. The association with serpentines was stronger than with amphiboles. Living on a slope and close to dense vegetation appeared protective. The use of whitewash, previously suggested to be a risk factor, was not associated with MM incidence. CONCLUSIONS: Presence of serpentinite on roads is a major environmental risk factor for mesothelioma in New Caledonia.