The middle Darriwilian carbon isotope excursion (MDICE) event is first documented from central eastern Korea (Taebaeksan Basin), the eastern part of the Sino-Korean Block, and is well correlated with global carbon isotope chemostratigraphy. The Korean MDICE record shows three broad positive peaks and complements records from the Middle Ordovician peri-Gondwanan epeiric seas showing incomplete records due to disconformity. This study reconstructed paleoceanographic conditions with nitrogen isotopic compositions and clay mineral compositions to understand the causes of carbon isotope excursions. The heavier excursion in nitrogen isotopic curve and abrupt increase of kaolinite in the early MDICE interval are interpreted as a result of epeiric sea denitrification associated with strong seawater stratification, and the main cause of those conditions was likely increased precipitation in the adjacent land. Subsequent sea-level rise caused an anti-estuarine circulation in the Taebaeksan sea and increased the organic carbon burial in the adjacent basin setting, which might have sustained the MDICE. The documentation of the MDICE event in this study supports the view that the MDICE occurred globally. This study provides not only information on the regional paleoceanographic conditions that occurred in the Middle Ordovician epeiric seas during the course of MDICE, but also reports that the MDICE event occurred as a response to seawater circulation associated with global sea-level rising in the Middle Ordovician.

Barco, R.A., Garrity, G.M., Scott, J.J., Amend, J.P., Nealson, K.H., Emerson, D., 2020. A genus definition for Bacteria Archaea and based on a standard genome relatedness index. mBio 11, e02475-19.

http://mbio.asm.org/content/11/1/e02475-19.abstract Abstract: Genus assignment is fundamental in the characterization of microbes, yet there is currently no unambiguous way to demarcate genera solely using standard genomic relatedness indices. Here, we propose an approach to demarcate genera that relies on the combined use of the average nucleotide identity, genome alignment fraction, and the distinction between type- and non-type species. More than 3,500 genomes representing type strains of species from >850 genera of either bacterial or archaeal lineages were tested. Over 140 genera were analyzed in detail within the taxonomic context of order/family. Significant genomic differences between members of a genus and type species of other genera in the same order/family were conserved in 94% of the cases. Nearly 90% (92% if polyphyletic genera are excluded) of the type strains were classified in agreement with current taxonomy. The 448 type strains that need reclassification directly impact 33% of the genera analyzed in detail. The results provide a first line of evidence that the combination of genomic indices provides added resolution to effectively demarcate genera within the taxonomic framework that is currently based on the 16S rRNA gene. We also identify the emergence of natural breakpoints at the genome level that can further help in the circumscription of taxa, increasing the proportion of directly impacted genera to at least 43% and pointing at inaccuracies on the use of the 16S rRNA gene as a taxonomic marker, despite its precision. Altogether, these results suggest that genomic coherence is an emergent property of genera Bacteria Archaea in and . Bacteria Archaea Importance: In recent decades, the taxonomy of and , and therefore genus designation, has been largely based on the use of a single ribosomal gene, the 16S rRNA gene, as a taxonomic marker. We propose an approach to delineate genera that excludes the direct use of the 16S rRNA gene and focuses on a standard genome relatedness index, the average nucleotide identity. Our findings are of importance to the Bacteria Archaea microbiology community because the emergent properties of and that are identified in this study will help assign genera with higher taxonomic resolution.

Bargar, T.A., Stout, S.A., Alvarez, D., 2020. Petroleum hydrocarbons in semipermeable membrane devices Deepwater Horizon deployed in the Northern Gulf of Mexico and Florida keys following the incident. Marine Pollution Bulletin 150, 110622.

http://www.sciencedirect.com/science/article/pii/S0025326X19307702 Deepwater Horizon The (DWH) oil spill from April to July of 2010 contaminated Gulf of Mexico waters through release of an estimated 4.1 × 106 barrels of oil. Beginning in June of 2010, semipermeable membrane devices (SPMDs) were deployed near areas with sensitive marine habitats (Alabama Alps and Western Shelf) potentially exposed to that oil. Elevated TPAH50 concentrations, flux rates and similarity of histograms and