Interaction between Microbes, Minerals, and Fluids in Deep-Sea Hydrothermal Systems

The discovery of deep-sea hydrothermal vents in the late 1970s widened the limits of life and habitability. The mixing of oxidizing seawater and reduction of hydrothermal fluids create a chemical disequilibrium that is exploited by chemosynthetic bacteria and archaea to harness energy by converting inorganic carbon into organic biomass. Due to the rich variety of chemical sources and steep physico-chemical gradients, a large array of microorganisms thrive in these extreme environments, which includes but are not restricted to chemolithoautotrophs, heterotrophs, and mixotrophs. Past research has revealed the underlying relationship of these microbial communities with the subsurface geology and hydrothermal geochemistry. Endolithic microbial communities at the ocean floor catalyze a number of redox reactions through various metabolic activities. Hydrothermal chimneys harbor Fe-reducers, sulfur-reducers, sulfide and H2-oxidizers, methanogens, and heterotrophs that continuously interact with the basaltic, carbonate, or ultramafic basement rocks for energy-yielding reactions. Here, we briefly review the global deep-sea hydrothermal systems, microbial diversity, and microbe–mineral interactions therein to obtain in-depth knowledge of the biogeochemistry in such a unique and geologically critical subseafloor environment

Triple Oxygen Isotopic Compositions of Ocean Water from the Mariana Trench

International audienceHigh-precision triple oxygen isotope data on 40 water samples (5–10 923 m in depth) collected at the Challenger Deep of the Mariana Trench are reported in this study. The analyses at Laboratoire des Sciences du Climat et l’Environnement yield mean isotope values δ18O = −0.084 ± 0.224‰, δ17O = −0.061 ± 0.117‰, and 17O-excess = −17 ± 5 per meg, with standard deviations reported at 1σ. The range of δ18O (from −0.480 to 0.544‰) falls within records of the Global Seawater Oxygen-18 Database at the Mariana Trench. The average 17O-excess value at the Mariana Trench is more negative than the average 17O-excess value of −5 ± 4 (1σ) per meg in the only prior data set including deep ocean samples. The slope (λ) of the three-isotope plot of Mariana Trench water is 0.521 ± 0.003 (1σ), lower than λ of 0.528 ± 0.001 (1σ) for ocean water in the prior study. The new data set matches the prediction of the ocean isotope mass balance model, suggesting that it may represent a more appropriate ocean endmember for triple oxygen isotope thermometry. The 17O-excess of ocean water with respect to Vienna Standard Mean Ocean Water (VSMOW) is recognized to be a necessary correction in quantifying gross oxygen productivity of euphotic regions and relative humidity of moisture source regions

Phosphorus Species in Deep-Sea Carbonate Deposits: Implications for Phosphorus Cycling in Cold Seep Environments

Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P in seep carbonates were examined at three deep-sea cold seeps in the South China Sea and East China Sea. The Ca-P accounts for the largest proportion of P—followed by detrital-P, Fe-P, organic-P, and exchangeable-P. The distribution patterns of Ca-P, detrital-P, and organic-P in the seep carbonates differ from one another, as shown by elemental mapping with NanoSIMS and scanning electron microscopy. The covariation of P with Ca and C reveals that Ca-P co-precipitates with Ca-carbonate, which is linked to the process of sulfate-driven anaerobic oxidation of methane. Organic-P is also observed within biofilm-like organic carbon aggregates, revealing the microbial enrichment of P by fluids in the process of anaerobic oxidation of methane. P with a granulated morphology was identified as detrital-P derived from deep sediments. Most importantly, it is evident that Ca-P is positively correlated to the Fe content in all the seep carbonates. This indicates the likelihood that the dissolved P in cold-seep fluids is released primarily from Fe oxides through Fe-driven anaerobic oxidation of methane in deep sediments. These processes associated with different species of P may have significant implications for P geochemical cycling and anaerobic oxidation of methane impelled by Fe and sulfate reduction in cold seep environments

Laser tweezers Raman spectroscopy combined with deep learning to classify marine bacteria

Rapid identification of marine microorganisms is critical in marine ecology, and Raman spectroscopy is a promising means to achieve this. Single cell Raman spectra contain the biochemical profile of a cell, which can be used to identify cell phenotype through classification models. However, traditional classification methods require a substantial reference database, which is highly challenging when sampling at difficult-to-access locations. In this scenario, only a few spectra are available to create a taxonomy model, making qualitative analysis difficult. And the accuracy of classification is reduced when the signal-to-noise ratio of a spectrum is low. Here, we describe a novel method for categorizing microorganisms that combines optical tweezers Raman spectroscopy, Progressive Growing of Generative Adversarial Nets (PGGAN), and Residual network (ResNet) analysis. Using the optical Raman tweezers, we acquired single cell Raman spectra from five deep-sea bacterial strains. We randomly selected 300 spectra from each strain as the database for training a PGGAN model. PGGAN generates a large number of high-resolution spectra similar to the real data for the training of the residual neural network. Experimental validations show that the method enhances machine learning classification accuracy while also reducing the demand for a considerable amount of training data, both of which are advantageous for analyzing Raman spectra of low signal-to-noise ratios. A classification model was built with this method, which reduces the spectra collection time to 1/3 without compromising the classification accuracy

Large plastic debris dumps: New biodiversity hot spots emerging on the deep-sea floor

Macroplastic debris recorded in the Mariana Trench and accumulated on some deep-sea canyons worldwide has aroused great public concerns. Large plastic debris dumps found in canyons of the Xisha Trough, South China Sea have become hot spots for deep-sea pollution, with 1 order of magnitude higher abundance than in other investigated canyons. Here we adopted an integrative specimen-based approach to examine macroplastic items from large debris dumps in the Xisha Trough and comparative items from continental shelves with rare macroplastics. On the investigated items, we found an epibenthic ecosystem with relatively high species diversity, comprised of 49 mm-sized fungi and invertebrate species dominated by scyphozoan polyps and brachiopod juveniles according to inhabiting density. These large dumps are functioning as new biodiversity hot spots hosting endemic species like soft corals or aplacophoran molluscs, providing a spawning habitat for gastropods and even specialized parasitic flatworms, and can be inferred as potential scattered regional sources releasing deep-sea coronate jellyfish. We hypothesize that macroplastics can boost population extension of sessile and some free-living (Mollusca) invertebrates and affect the deep-sea benthic-pelagic coupling process. The baseline of associated organisms needs to be set up and monitored in more canyons, where debris is transported to and accumulated at the highest density.Fil: Song, Xikun. Xiamen University; ChinaFil: Lyu, Mingxin. Xiamen University; ChinaFil: Zhang, Xiaodi. Chinese Academy of Sciences; República de ChinaFil: Ruthensteiner, Bernhard. Zoologische Staatssammlung München; AlemaniaFil: Ahn, In Young. Korea Polar Research Institute; Corea del SurFil: Pastorino, Roberto Santiago Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Wang, Yunan. Xiamen University; ChinaFil: Gu, Yifan. Xiamen University; ChinaFil: Ta, Kaiwen. Chinese Academy of Sciences; República de ChinaFil: Sun, Jie. Northwestern University; Estados UnidosFil: Liu, Xi. Northwestern University; Estados UnidosFil: Han, Jian. Northwestern University; Estados UnidosFil: Ke, Caihuan. Xiamen University; ChinaFil: Peng, Xiaotong. Chinese Academy of Sciences; República de Chin