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Symbioses between Bacteria, Archaea, and Eukarya in deep-sea marine environments represent a means for eukaryotes to exploit otherwise inhospitable habitats. Such symbioses are abundant in many low-oxygen benthic marine environments, where the majority of microbial eukaryotes contain prokaryotic symbionts. Here, we present evidence suggesting that in certain oxygen-depleted marine water-column habitats, the majority of microbial eukaryotes are also associated with prokaryotic cells. Ciliates (protists) associated with bacteria were found to be the dominant eukaryotic morphotype in the haloclines of two different deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea. These findings are compared to associations between ciliates and bacteria documented from the permanently anoxic waters of the Cariaco Basin (Caribbean Sea). The dominance of ciliates exhibiting epibiotic bacteria across three different oxygen-depleted marine water column habitats suggests that such partnerships confer a fitness advantage for ciliates in these environments.
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http://dx.doi.org/10.3389/fmicb.2012.00341 | DOI Listing |
Microbiome
August 2025
Marine Science Institute, University of California, Santa Barbara, CA, USA.
Background: Fungi are known members of marine microbiomes that can act as saprotrophs, parasites, and pathogens. Although a few studies utilizing cultivation-based methods and metabarcoding have been conducted, the diversity, ecological roles, and functional activities of fungi in the open ocean remain vastly underexplored. This gap in knowledge is particularly notable in oxygen minimum zones (OMZ) of the ocean, which have expanded over the past 50 years, affecting marine ecosystems and biogeochemical cycles.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
July 2025
Département des Sciences Biologiques, Université du Québec à Montréal, Montréal H2X 1Y4, QC, Canada.
Dissolved oxygen (DO) is an essential resource in ice-covered lakes, regulating water quality and biodiversity, including the survival of economically important fish species. Most of the world's lakes seasonally freeze, often resulting in oxygen depletion as ice cover inhibits water column ventilation and snow cover limits photosynthesis while respiration continues. Widespread shortening of ice-cover duration in a warmer world might improve winter oxygenation, but this hypothesis remains untested.
View Article and Find Full Text PDFMar Environ Res
August 2025
College of Marine Living Resource Sciences and Management, Shanghai Ocean University, Shanghai, 201306, China; Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China; National Engineering Research Center fo
This study analyzes the effects of the El Niño and La Niña phenomena on the physiological ecology and mercury contamination levels of Chub mackerel, using samples collected from the Northwest Pacific region in 2021 (a La Niña year) and 2023 (an El Niño year). We analyzed body condition (Fulton's K index), trophic dynamics (δC, δN isotopes), and mercury levels in individuals across size classes (100-300 mm). The results indicate that, smaller mackerel (100-200 mm) exhibited significantly higher K values during El Niño (p < 0.
View Article and Find Full Text PDFPNAS Nexus
March 2025
Marine Science Program, Biological and Environmental Science and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
Persistent oxygen-depleted zones in the ocean are known primarily from enclosed basins in temperate regions or the open ocean (including oxygen minimum and limiting zones) (1). However, little is known about the possibility of such zones forming in tropical coastal domains, even though the combination of warmer temperatures and complex geological features in some tropical regions makes their occurrence more likely (1, 2). Here, we report two subsurface oxygen-depleted zones within deep (>490 m) depressions of the Red Sea's Difaht Farasan-a carbonate platform hosting the world's third largest contiguous tropical coral reef system.
View Article and Find Full Text PDFEcol Evol
January 2025
Tianjin Key Laboratory of Animal and Plant Resistance, Tianjin Key Laboratory of Conservation and Utilization of Animal Diversity, College of Life Science Tianjin Normal University Tianjin China.
Understanding the adaptation of archaea to hypoxia is essential for deciphering the functions and mechanisms of microbes when suffering environmental changes. However, the dynamics and responses of archaea to the sedimentary hypoxia in Bohai Sea are still unclear. In this study, the diversity, composition, and distribution of archaeal community in sediment along an inshore-offshore transect across the oxygen-depleted area in the Bohai Sea were investigated in June, July, and August of 2021 by employing high-throughput sequencing of 16S rRNA gene.
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