Mangrove microniches determine the structural and functional diversity of enriched petroleum hydrocarbon-degrading consortia

In this study, the combination of culture enrichments and molecular tools was used to identify bacterial guilds, plasmids and functional genes potentially important in the process of petroleum hydrocarbon (PH) decontamination in mangrove microniches (rhizospheres and bulk sediment). In addition, we aimed to recover PH-degrading consortia (PHDC) for future use in remediation strategies. The PHDC were enriched with petroleum from rhizosphere and bulk sediment samples taken from a mangrove chronically polluted with oil hydrocarbons. Southern blot hybridization (SBH) assays of PCR amplicons from environmental DNA before enrichments resulted in weak positive signals for the functional gene types targeted, suggesting that PH-degrading genotypes and plasmids were in low abundance in the rhizosphere and bulk sediments. However, after enrichment, these genes were detected and strong microniche-dependent differences in the abundance and composition of hydrocarbonoclastic bacterial populations, plasmids (IncP-1 alpha, IncP-1 beta, IncP-7 and IncP-9) and functional genes (naphthalene, extradiol and intradiol dioxygenases) were revealed by in-depth molecular analyses [PCR-denaturing gradient gel electrophoresis and hybridization (SBH and microarray)]. Our results suggest that, despite the low abundance of PH-degrading genes and plasmids in the environmental samples, the original bacterial composition of the mangrove microniches determined the structural and functional diversity of the PHDC enriched.Deutsche Forschungsgemeinschaft [SM59/4-1, 4-2]; FAPERJ-Brazil; European Commission [003998, 211684]; Alexander-von-Humboldt-Stiftung; CONICET (Argentina)info:eu-repo/semantics/publishedVersio

Inherited morphobathymetric controls over contourite drift deposition: a case study from the late Cenozoic Mentelle Basin, Australia

Deep-sea sedimentary deposits are important archives of the geologic past that preserve the records of past environmental changes in earth’s ocean. The detailed analysis of deep-sea sedimentary archives, in particular of contourite drifts, can help elucidate past changes in ocean circulation and the stratigraphic evolution of continental margins. However, the bathymetric profile of an oceanic basin can shape and modify the architecture of contourite drifts via the interaction between down-slope and along-slope processes. The identification of local bathymetric influence on depositional architectures is therefore important to help decipher local versus regional influences on deep-sea sedimentary signatures. Seismic data from Mentelle Basin in the southeast Indian Ocean integrated with deep-sea core data reveal a calcareous-siliciclastic mixed contourite-turbidite system developed during the late Cenozoic, starting in the middle Miocene. Current winnowing led to the formation of regional hiatuses, ferromanganese crusts, and siliciclastic lag deposits. The main locus of sediment deposition occurred on the shallower parts of the basin, whereas sediment preservation remained low in the deeper areas. Seismic analysis shows that inherited topography influenced the architecture of contourite deposits within the basin, with elongate-mounded and sheeted drifts forming preferentially at shallower depths on the continental slope and the Naturaliste Plateau, while channel incision occurred in the deepest parts of the basin. These results suggest that the intensification of current transport occurred preferentially within the deeper and spatially constrained parts of the basin, whereas current deflection around the slope and plateau enhanced drift deposition and preservation at shallower depths. Therefore, the basin topography at the time of deposition controlled the distribution of deep-sea deposits and drift morphologies within the mixed contourite-turbidite system in the Mentelle Basin.G. Tagliaro, C.C. Wainman, and C.S. Fulthorp

Canterbury drifts at ocean drilling program site 1119, New Zealand: climatic modulation of southwest Pacific intermediate water flows since 3.9 Ma

We provide a record of variations in southwest Pacific Ocean intermediate water flow that shows a strong correlation between periods of vigorous flow and warm climate phases. Ocean Drilling Program Site 1119, located at 395 m water depth on the upper continental slope east of New Zealand, penetrated 514 m of silts and silty clays (glacial deposits) punctuated by muds and episodic 0.02–1.2-m-thick terrigenous sands (interglacial deposits). The natural gamma-ray record reflects the waxing and waning of the South Island ice cap since 3.91 Ma. Below 86.19 m composite depth, the succession comprises drift sediments deposited from north-flowing intermediate Subantarctic Mode Water (SAMW, ~250–800 m depth) and Antarctic Intermediate Water (~800–1100 m depth). A change from the deposition of large, low-energy drifts on the middle slope to smaller, higher-energy drifts on the upper slope coincided with global climatic deterioration that occurred after ca. 3.25 Ma. This change marks an upward expansion of intermediate cold waters, perhaps caused by the inception of the Subantarctic Front and the consequent commencement of Southland Current–driven SAMW flow