Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins

Background: The deep-sea hypersaline anoxic basins (DHABs) of the Mediterranean (water depth similar to 3500 m) are some of the most extreme oceanic habitats known. Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB haloclines and brines, loriciferans are the only metazoan reported to inhabit the anoxic DHAB brines. Our goal was to further investigate metazoan communities in DHAB haloclines and brines. Results: We report observations from sediments of three DHAB (Urania, Discovery, L'Atalante) haloclines, comparing these to observations from sediments underlying normoxic waters of typical Mediterranean salinity. Due to technical difficulties, sampling of the brines was not possible. Morphotype analysis indicates nematodes are the most abundant taxon; crustaceans, loriciferans and bryozoans were also noted. Among nematodes, Daptonema was the most abundant genus; three morphotypes were noted with a degree of endemicity. The majority of rRNA sequences were from planktonic taxa, suggesting that at least some individual metazoans were preserved and inactive. Nematode abundance data, in some cases determined from direct counts of sediments incubated in situ with CellTracker (TM) Green, was patchy but generally indicates the highest abundances in either normoxic control samples or in upper halocline samples; nematodes were absent or very rare in lower halocline samples. Ultrastructural analysis indicates the nematodes in L'Atalante normoxic control sediments were fit, while specimens from L'Atalante upper halocline were healthy or had only recently died and those from the lower halocline had no identifiable organelles. Loriciferans, which were only rarely encountered, were found in both normoxic control samples as well as in Discovery and L'Atalante haloclines. It is not clear how a metazoan taxon could remain viable under this wide range of conditions. Conclusions: We document a community of living nematodes in normoxic, normal saline deep-sea Mediterranean sediments and in the upper halocline portions of the DHABs. Occurrences of nematodes in mid-halocline and lower halocline samples did not provide compelling evidence of a living community in those zones. The possibility of a viable metazoan community in brines of DHABs is not supported by our data at this time

Fungal and prokaryotic activities in the marine subsurface biosphere at Peru Margin and Canterbury Basin inferred from RNA-based analyses and microscopy

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 7 (2016): 846, doi:10.3389/fmicb.2016.00846.The deep sedimentary biosphere, extending 100s of meters below the seafloor harbors unexpected diversity of Bacteria, Archaea, and microbial eukaryotes. Far less is known about microbial eukaryotes in subsurface habitats, albeit several studies have indicated that fungi dominate microbial eukaryotic communities and fungal molecular signatures (of both yeasts and filamentous forms) have been detected in samples as deep as 1740 mbsf. Here, we compare and contrast fungal ribosomal RNA gene signatures and whole community metatranscriptomes present in sediment core samples from 6 and 95 mbsf from Peru Margin site 1229A and from samples from 12 and 345 mbsf from Canterbury Basin site U1352. The metatranscriptome analyses reveal higher relative expression of amino acid and peptide transporters in the less nutrient rich Canterbury Basin sediments compared to the nutrient rich Peru Margin, and higher expression of motility genes in the Peru Margin samples. Higher expression of genes associated with metals transporters and antibiotic resistance and production was detected in Canterbury Basin sediments. A poly-A focused metatranscriptome produced for the Canterbury Basin sample from 345 mbsf provides further evidence for active fungal communities in the subsurface in the form of fungal-associated transcripts for metabolic and cellular processes, cell and membrane functions, and catalytic activities. Fungal communities at comparable depths at the two geographically separated locations appear dominated by distinct taxa. Differences in taxonomic composition and expression of genes associated with particular metabolic activities may be a function of sediment organic content as well as oceanic province. Microscopic analysis of Canterbury Basin sediment samples from 4 and 403 mbsf produced visualizations of septate fungal filaments, branching fungi, conidiogenesis, and spores. These images provide another important line of evidence supporting the occurrence and activity of fungi in the deep subseafloor biosphere.This work was supported by Deep Carbon Observatory subaward #48550 to VE, and NSF Center for Deep Energy Biosphere Investigations (CDEBI) grant OCE-0939564 to VE and GB. GB was also supported by the European project MaCuMBA (Marine Microorganisms: Cultivation Methods for Improving Their Biotechnological Applications, FP7, Grant agreement number 311975)

Structured Multiple Endosymbiosis of Bacteria and Archaea in a Ciliate from Marine Sulfidic Sediments: A Survival Mechanism in Low Oxygen, Sulfidic Sediments?

Marine micro-oxic to sulfidic environments are sites of intensive biogeochemical cycling and elemental sequestration, where prokaryotes are major driving forces mediating carbon, nitrogen, sulfur, phosphorus, and metal cycles, important from both biogeochemical and evolutionary perspectives. Associations between single-celled eukaryotes and bacteria and/or archaea are common in such habitats. Here we describe a ciliate common in the micro-oxic to anoxic, typically sulfidic, sediments of Santa Barbara Basin (CA, USA). The ciliate is 95% similar to Parduzcia orbis (18S rRNA). Transmission electron micrographs reveal clusters of at least three different endobiont types organized within membrane-bound sub-cellular regions. Catalyzed reporter deposition–fluorescent in situ hybridization and 16S rRNA clone libraries confirm the symbionts include up to two sulfate reducers (Desulfobulbaceae, Desulfobacteraceae), a methanogen (Methanobacteriales), and possibly a Bacteroidete (Cytophaga) and a Type I methanotroph, suggesting synergistic metabolisms in this environment. This case study is discussed in terms of implications to biogeochemistry, and benthic ecology

Active eukaryotes in microbialites from Highborne Cay, Bahamas, and Hamelin Pool (Shark Bay), Australia

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in The ISME Journal 8 (2014): 418–429, doi:10.1038/ismej.2013.130.Microbialites are organosedimentary structures that are formed through the interaction of benthic microbial communities and sediments and include mineral precipitation. These lithifying microbial mat structures include stromatolites and thrombolites. Exuma Sound in the Bahamas, and Hamelin Pool in Shark Bay, Western Australia are two locations where significant stands of modern microbialites exist. Although prokaryotic diversity in these structures is reasonably well documented, little is known about the eukaryotic component of these communities and their potential to influence sedimentary fabrics through grazing, binding and burrowing activities. Accordingly, comparisons of eukaryotic communities in modern stromatolitic and thrombolytic mats can potentially provide insight into the coexistence of both laminated and clotted mat structures in close proximity to one another. Here we examine this possibility by comparing eukaryotic diversity based on Sanger and high-throughput pyrosequencing of small subunit ribosomal RNA (18S rRNA) genes. Analyses were based on total RNA extracts as template to minimize input from inactive or deceased organisms. Results identified diverse eukaryotic communities particularly stramenopiles, Alveolata, Metazoa, Amoebozoa, and Rhizaria within different mat types at both locations, as well as abundant and diverse signatures of eukaryotes with <80% sequence similarity to sequences in GenBank. This suggests presence of significant novel eukaryotic diversity, particularly in hypersaline Hamelin Pool. There was evidence of vertical structuring of protist populations and foraminiferal diversity was highest in bioturbated/clotted thrombolite mats of Highborne Cay.This work was funded by grant OCE-0926421 to JMB and VPE and OCE-0926372 to RES

Élaboration et expérimentation d’un modèle intégrateur en accompagnement professionnel dans le cadre d’une recherche-action-formation

This research experiments an innovative integrative model of professional support in collaboration with two health and physical education teachers. The objectives of this article are to describe: 1) the modifications made to the model by the participants and 2) the strengths and the elements to improve this process. To meet these objectives, two methods of data collection were used in a collaborative action research: 1) group interviews and 2) logbooks. The main finding is that this professional development device has several strengths, but requires a significant commitment from the participants. Keywords: professional support, professional development, collaborative action research, health education, health and physical educationCette recherche expérimente un modèle intégrateur novateur en accompagnement professionnel en collaboration avec deux enseignantes d’éducation physique et à la santé. Les objectifs de cet article sont de décrire : 1) les modifications apportées au modèle par les participantes et 2) les forces et les éléments à améliorer de la démarche d’accompagnement. Pour répondre à ces objectifs, nous avons utilisé deux méthodes de collecte de données dans une recherche-action-formation, soit : 1) des entretiens collectifs et 2) des journaux de bord. Le principal constat est que la démarche d’accompagnement présente plusieurs forces selon les participantes, mais nécessite un engagement important de leur part. Mots-clés : accompagnement professionnel, développement professionnel, recherche-action-formation, éducation à la santé, éducation physique et à la sant

Impacts of multiple stressors on a benthic foraminiferal community: a long-term experiment assessing response to ocean acidification, hypoxia and warming

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bernhard, J. M., Wit, J. C., Starczak, V. R., Beaudoin, D. J., Phalen, W. G., & McCorkle, D. C. Impacts of multiple stressors on a benthic foraminiferal community: a long-term experiment assessing response to ocean acidification, hypoxia and warming. Frontiers in Marine Science, 8, (2021): 643339, https://doi.org/10.3389/fmars.2021.643339.Ocean chemistry is changing as a result of human activities. Atmospheric carbon dioxide (CO2) concentrations are increasing, causing an increase in oceanic pCO2 that drives a decrease in oceanic pH, a process called ocean acidification (OA). Higher CO2 concentrations are also linked to rising global temperatures that can result in more stratified surface waters, reducing the exchange between surface and deep waters; this stronger stratification, along with nutrient pollution, contributes to an expansion of oxygen-depleted zones (so called hypoxia or deoxygenation). Determining the response of marine organisms to environmental changes is important for assessments of future ecosystem functioning. While many studies have assessed the impact of individual or paired stressors, fewer studies have assessed the combined impact of pCO2, O2, and temperature. A long-term experiment (∼10 months) with different treatments of these three stressors was conducted to determine their sole or combined impact on the abundance and survival of a benthic foraminiferal community collected from a continental-shelf site. Foraminifera are well suited to such study because of their small size, relatively rapid growth, varied mineralogies and physiologies. Inoculation materials were collected from a ∼77-m deep site south of Woods Hole, MA. Very fine sediments (<53 μm) were used as inoculum, to allow the entire community to respond. Thirty-eight morphologically identified taxa grew during the experiment. Multivariate statistical analysis indicates that hypoxia was the major driving factor distinguishing the yields, while warming was secondary. Species responses were not consistent, with different species being most abundant in different treatments. Some taxa grew in all of the triple-stressor samples. Results from the experiment suggest that foraminiferal species’ responses will vary considerably, with some being negatively impacted by predicted environmental changes, while other taxa will tolerate, and perhaps even benefit, from deoxygenation, warming and OA.This work was supported by the US NSF SEES-OA grant OCE-1219948 to JB and the Investment in Science Program at WHOI. DM also received support from the NSF Independent Research and Development Program