Potential oxygen consumption and community composition of sediment bacteria in a seasonally hypoxic enclosed bay

• Published in: PeerJ (San Francisco, CA) Vol. 9; p. e11836
• Main Authors: Mori, Fumiaki, Umezawa, Yu, Kondo, Ryuji, Nishihara, Gregory N, Wada, Minoru
• Format: Journal Article
• Language: English
• Published: San Diego PeerJ. Ltd 10.08.2021; PeerJ, Inc; PeerJ Inc
• Subjects: Aquatic and Marine Chemistry; Arcobacter; Bacteria; Bacterial community composition; Biogeochemistry; Coastal hypoxia; Community composition; Dissolved oxygen; Ecology; Enclosed bay; Hypoxia; Marine Biology; Microbiology; Molecular Biology; Oxygen consumption; Respiration; rRNA 16S; Salinity; Sediment oxygen consumption; Sediments; Sulfate reduction; Sulfate-reducing bacteria; Sulfur; Summer; Japan; Omura Bay
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.11836

The dynamics of potential oxygen consumption at the sediment surface in a seasonally hypoxic bay were monitored monthly by applying a tetrazolium dye (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride [INT]) reduction assay to intact sediment core samples for two consecutive years (2012-2013). Based on the empirically determined correlation between INT reduction (INT-formazan formation) and actual oxygen consumption of sediment samples, we inferred the relative contribution of biological and non-biological (chemical) processes to the potential whole oxygen consumption in the collected sediment samples. It was demonstrated that both potentials consistently increased and reached a maximum during summer hypoxia in each year. For samples collected in 2012, amplicon sequence variants (ASVs) of the bacterial 16S rRNA genes derived from the sediment surface revealed a sharp increase in the relative abundance of sulfate reducing bacteria toward hypoxia. In addition, a notable shift in other bacterial compositions was observed before and after the INT assay incubation. It was Arcobacter (Arcobacteraceae, Campylobacteria), a putative sulfur-oxidizing bacterial genus, that increased markedly during the assay period in the summer samples. These findings have implications not only for members of Delta- and Gammaproteobacteria that are consistently responsible for the consumption of dissolved oxygen (DO) year-round in the sediment, but also for those that might grow rapidly in response to episodic DO supply on the sediment surface during midst of seasonal hypoxia.