Microbiology and Nitrogen Cycle in the Benthic Sediments of a Glacial Oligotrophic Deep Andean Lake as Analog of Ancient Martian Lake-Beds

Potential benthic habitats of early Mars lakes, probably oligotrophic, could range from hydrothermal to cold sediments. Dynamic processes in the water column (such as turbidity or UV penetration) as well as in the benthic bed (temperature gradients, turbation, or sedimentation rate) contribute to supply nutrients to a potential microbial ecosystem. High altitude, oligotrophic, and deep Andean lakes with active deglaciation processes and recent or past volcanic activity are natural models to assess the feasibility of life in other planetary lake/ocean environments and to develop technology for their exploration. We sampled the benthic sediments (down to 269 m depth) of the oligotrophic lake Laguna Negra (Central Andes, Chile) to investigate its ecosystem through geochemical, biomarker profiling, and molecular ecology studies. The chemistry of the benthic water was similar to the rest of the water column, except for variable amounts of ammonium (up to 2.8 ppm) and nitrate (up to 0.13 ppm). A life detector chip with a 300-antibody microarray revealed the presence of biomass in the form of exopolysaccharides and other microbial markers associated to several phylogenetic groups and potential microaerobic and anaerobic metabolisms such as nitrate reduction. DNA analyses showed that 27% of the Archaea sequences corresponded to a group of ammonia-oxidizing archaea (AOA) similar (97%) to Nitrosopumilus spp. and Nitrosoarchaeum spp. (Thaumarchaeota), and 4% of Bacteria sequences to nitrite-oxidizing bacteria from the Nitrospira genus, suggesting a coupling between ammonia and nitrite oxidation. Mesocosm experiments with the specific AOA inhibitor 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) demonstrated an AOA-associated ammonia oxidation activity with the simultaneous accumulation of nitrate and sulfate. The results showed a rich benthic microbial community dominated by microaerobic and anaerobic metabolisms thriving under aphotic, low temperature (4°C), and relatively high pressure, that might be a suitable terrestrial analog of other planetary settings

A test in a high altitude lake of a multi-parametric rapid methodology for assessing life in liquid environments on planetary bodies: A potential new freshwater polychaete Tubeworm community

On our planet, aqueous environments such as deep sea or high-altitude aphotic lakes, subject to present or past volcanic activity and active deglaciation, may provide analogs to the aqueous environments found on such planetary bodies as Europa, Titan or Enceladus. We report here on the methodologies and technologies tested in Laguna Negra, a high altitude lake in the Central Andes, Chile, for exploring and assessing the presence of life within planetary lakes or interior oceans. We adopted a multi-parametric Rapid Ecological Assessment (REA) approach centered around collecting video imagery (by an Underwater Imaging System) and sampling benthic sediments (for sedimentological, biological and geochemical analysis) to depths of 272 m, to complement physico-chemical sampling of the water column and collection of shallow sediments for microbiological analysis (reported in separate publications). This enabled us to classify and assess the apparent status of benthic habitats, based on substrata and environmental characteristics, together with floral and faunal community characteristics and bioturbation artifacts. Video imagery showed that the lower water column was characterized by a variably intense sestonic flux of particles and debris, among which were planktonic organisms such as ostracods, copepods, and possibly cladocerans. Sediment analysis revealed at all depths abundant diatom frustules, mainly of an acidophile pennade diatom Pinnularia acidicola, amid vegetal debris likely originating from littoral macrophytes. Video imagery showed that the lakebed was partly covered by microbial mats and depositional matter and harbored an unexpectedly rich assortment of macrofauna, including sponges, tubificid worms, flatworms, bivalves and crustaceans. Various forms of bioturbation were also encountered, some with the animals in the tracks. Most notably, at the deepest site, a previously undescribed faunal feature was evident, apparently formed by a mat-like community of several layers of what appeared to be polychaete tubeworms, possibly of the family Siboglinidae. It is hypothesized that the hydrothermal activity observed in the region may supply the compounds able to support the deep-water microrganisms from which such tubeworms typically gain sustenance. Such processes could be present on other deep and aphotic liquid-water-bearing planetary bodies

The Concept of Oceanian Sovereignty in the Context of Deep Sea Mining in the Pacific Region

Based on an interdisciplinary experience addressing traditional dimensions in marine resource management in the Pacific, the socio-ecological interconnectivity between island communities, the ocean realm and the legal context concerning the management of seabed resources (Tilot, 2006, 2010; Tilot et al., 2018, 2021a,b; Mulalap et al., 2020; Willaert, 2020a,b, c; 2021; DOSI, 2021), this paper proposes to discuss the relevance and efficacy of the concept of "Oceanian Sovereignty" (Bambridge et al., 2021) in the context of Deep Sea Mining, from the different legal, environmental, anthropological, social, political, and economic science perspectives. The policies and practices developed in the Pacific in this context could well serve as a suitable model elsewhere to reconcile competing perspectives in addition to sustaining the Human Well-being and Sustainable Livelihoods (HWSL) and the health of the Global Ocean