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  • Giosan, Liviu  (4)
  • Biodiversity Research  (4)
  • 1
    Online Resource
    Online Resource
    Wiley ; 2019
    In:  Geobiology Vol. 17, No. 4 ( 2019-07), p. 436-448
    In: Geobiology, Wiley, Vol. 17, No. 4 ( 2019-07), p. 436-448
    Abstract: Subsurface microbial communities are generally thought to be structured through in situ environmental conditions such as the availability of electron acceptors and donors and porosity, but recent studies suggest that the vertical distribution of a subset of subseafloor microbial taxa, which were present at the time of deposition, were selected by the paleodepositional environment. However, additional highly resolved temporal records of subsurface microbiomes and paired paleoenvironmental reconstructions are needed to justify this claim. Here, we performed a highly resolved shotgun metagenomics survey to study the taxonomic and functional diversity of the subsurface microbiome in Holocene sediments underlying the permanently stratified and anoxic Black Sea. Obligate aerobic bacteria made the largest contribution to the observed shifts in microbial communities associated with known Holocene climate stages and transitions. This suggests that the aerobic fraction of the subseafloor microbiome was seeded from the water column and did not undergo post‐depositional selection. In contrast, obligate and facultative anaerobic bacteria showed the most significant response to the establishment of modern‐day environmental conditions 5.2 ka ago that led to a major shift in planktonic communities and in the type of sequestered organic matter available for microbial degradation. No significant shift in the subseafloor microbiome was observed as a result of environmental changes that occurred shortly after the marine reconnection, 9 ka ago. This supports the general view that the marine reconnection was a gradual process. We conclude that a high‐resolution analysis of downcore changes in the subseafloor microbiome can provide detailed insights into paleoenvironmental conditions and biogeochemical processes that occurred at the time of deposition.
    Type of Medium: Online Resource
    ISSN: 1472-4677 , 1472-4669
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2113509-5
    SSG: 12
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  • 2
    In: Geobiology, Wiley, Vol. 19, No. 2 ( 2021-03), p. 162-172
    Abstract: The vertical distribution of subseafloor archaeal communities is thought to be primarily controlled by in situ conditions in sediments such as the availability of electron acceptors and donors, although sharp community shifts have also been observed at lithological boundaries suggesting that at least a subset of vertically stratified Archaea form a long‐term genetic record of coinciding environmental conditions that occurred at the time of sediment deposition. To substantiate this possibility, we performed a highly resolved 16S rRNA gene survey of vertically stratified archaeal communities paired with paleo‐oceanographic proxies in a sedimentary record from the northern Red Sea spanning the last glacial–interglacial cycle (i.e., marine isotope stages 1–6; MIS1‐6). Our results show a strong significant correlation between subseafloor archaeal communities and drastic paleodepositional changes associated with glacial low vs. interglacial high stands (ANOSIM; R  = .73; p  = .001) and only a moderately strong correlation with lithological changes. Bathyarchaeota, Lokiarchaeota, MBGA, and DHVEG‐1 were the most abundant identified archaeal groups. Whether they represented ancient cell lines from the time of deposition or migrated to the specific sedimentary horizons after deposition remains speculative. However, we show that the majority of sedimentary archaeal tetraether membrane lipids were of allochthonous origin and not produced in situ. Slow post‐burial growth under energy‐limited conditions would explain why the downcore distribution of these dominant archaeal groups still indirectly reflect changes in the paleodepositional environment that prevailed during the analyzed marine isotope stages. In addition, archaea seeded from the overlying water column such as Thaumarchaeota and group II and III Euryarchaeota, which were likely not have been able to subsist after burial, were identified from a lower abundance of preserved sedimentary DNA signatures, and represented direct markers of paleoenvironmental changes in the Red Sea spanning the last six marine isotope stages.
    Type of Medium: Online Resource
    ISSN: 1472-4677 , 1472-4669
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2113509-5
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 2013
    In:  Proceedings of the National Academy of Sciences Vol. 110, No. 21 ( 2013-05-21), p. 8609-8614
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 110, No. 21 ( 2013-05-21), p. 8609-8614
    Abstract: The complex interplay of climate shifts over Eurasia and global sea level changes modulates freshwater and saltwater inputs to the Black Sea. The dynamics of the hydrologic changes from the Late Glacial into the Holocene remain a matter of debate, and information on how these changes affected the ecology of the Black Sea is sparse. Here we used Roche 454 next-generation pyrosequencing of sedimentary 18S rRNA genes to reconstruct the plankton community structure in the Black Sea over the last ca. 11,400 y. We found that 150 of 2,710 species showed a statistically significant response to four environmental stages. Freshwater chlorophytes were the best indicator species for lacustrine conditions ( 〉 9.0 ka B.P.), although the copresence of previously unidentified marine taxa indicated that the Black Sea might have been influenced to some extent by the Marmara Sea since at least 9.6 ka calendar (cal) B.P. Dinoflagellates, cercozoa, eustigmatophytes, and haptophytes responded most dramatically to the gradual increase in salinity after the latest marine reconnection and during the warm and moist mid-Holocene climatic optimum. According to paired analysis of deuterium/hydrogen (D/H) isotope ratios in fossil alkenones, salinity increased rapidly with the onset of the dry Subboreal after ∼5.2 ka B.P., leading to an increase in marine fungi and the first occurrence of marine copepods. A gradual succession of dinoflagellates, diatoms, and chrysophytes occurred during the refreshening after ∼2.5 ka cal B.P. with the onset of the cool and wet Subatlantic climate and recent anthropogenic perturbations.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2013
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    In: Grana, Informa UK Limited, Vol. 53, No. 3 ( 2014-07-03), p. 249-251
    Type of Medium: Online Resource
    ISSN: 0017-3134 , 1651-2049
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2014
    detail.hit.zdb_id: 2016533-X
    detail.hit.zdb_id: 420608-3
    SSG: 12
    SSG: 13
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