Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity
"The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. [...]"
Authors: Zouhair Lachkar, Marina Lévy, and Shafer Smith
Metabolic versatility of a novel N2-fixing Alphaproteobacterium isolated from a marine oxygen minimum zone
"The N2-fixing (diazotrophic) community in marine ecosystems is dominated by non-cyanobacterial microorganisms. Yet, very little is known about their identity, function and ecological relevance due to a lack of cultured representatives. Here we report a novel heterotrophic diazotroph isolated from the oxygen minimum zone (OMZ) off Peru. [...]"
Source: environmental microbiology
Authors: Clara Martínez-Pérez et al.
Patterns of deoxygenation: sensitivity to natural and anthropogenic drivers
"Observational estimates and numerical models both indicate a significant overall decline in marine oxygen levels over the past few decades. Spatial patterns of oxygen change, however, differ considerably between observed and modelled estimates. Particularly in the tropical thermocline that hosts open-ocean oxygen minimum zones, observations indicate a general oxygen decline, whereas most of the state-of-the-art models simulate increasing oxygen levels. Possible reasons for the apparent model-data discrepancies are examined. [...]"
Source: Philosophical Transactions of the Royal Socie
Authors: Andreas Oschlies et al.
Bacterial Community Profiling of the Arabian Sea Oxygen Minimum Zone Sediments using Cultivation Independent Approach
"The eastern Arabian Sea has a unique and permanent oxygen minimum zone (OMZ) that extends along the western continental margin of India. In order to understand the bacterial community structure and diversity of OMZ sediment of the Arabian Sea (AS), PCR-DGGE analysis were carried out for samples collected off Ratnagiri, Goa and Karwar at 50m, 200m, 500m and 1000m depths. [...]"
Source: Examines Mar Biol Oceanogr
Authors: Baby Divya, Annie Feby and Shanta Nair
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Biodiversity surprises at bubbly deep-sea cold seeps along Cascadia fault
"A new study led by Oregon State University (OSU) graduate student Sarah Seabrook that uses scientific data and samples from Ocean Networks Canada (ONC) focuses on the extent, variability, and complexity of species—from microbes to tubeworms—found at deep-sea cold seep habitats along the Cascadia fault off the west coast of North America.
The study reports for the first time on the surprisingly rich and diverse microbial and animal communities at eight recently discovered cold seeps, comparing these new sites off the coasts of Washington, Oregon, and northern California with two known seeps off the coast of British Columbia at Barkley Canyon and Clayoquot Slope—both monitored by ONC's cabled offshore observatory. [...]"
On the effect of low oxygen concentrations on bacterial degradation of sinking particles
"In marine oxygen (O2) minimum zones (OMZs), the transfer of particulate organic carbon (POC) to depth via the biological carbon pump might be enhanced as a result of slower remineralisation under lower dissolved O2 concentrations (DO). In parallel, nitrogen (N) loss to the atmosphere through microbial processes, such as denitrification and anammox, is directly linked to particulate nitrogen (PN) export. [...]"
Source: Scientific Reports
Authors: Frédéric A. C. Le Moigne
When oxygen disappeared, early marine animals really started evolving
"Animals need oxygen to survive, but a relative lack of oxygen in Earth’s ancient oceans helped early marine creatures evolve, a new study claims. Indeed, the “Cambrian explosion”—the burst of evolution about 540 million years ago that included the birth of most of the major animal groups we know today—was enabled by oxygen deprivation, the researchers say. The finding comes in the wake of a better understanding of how oxygen levels in the oceans and the atmosphere fluctuated in the deep past, and may shift how scientists think animal evolution can proceed. [...]"
Source: Science Magazine
Author: Lucas Joel
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Abyssal ocean overturning shaped by seafloor distribution
"The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows—referred to as the abyssal overturning circulation—is key to quantifying the ocean’s ability to store carbon and heat on timescales exceeding a century. [...]"
Authors: C. de Lavergne et al.
Mysterious ‘shadow zone’ traps 2000-year-old water
"A MYSTERIOUS abyss in the ocean known as the “shadow zone” traps ancient water dating back to 400AD. We now know why it’s there.
IT’S called the “shadow zone” and it lies around two kilometres below the surface in an ocean abyss where trapped water dates back to the fourth century.
This ancient water, which is between 1000 and 2000 years old, dates back to when the ancient Germanic tribe the Goths instigated the end of the Western Roman Empire and the rise of Medieval Europe. [...]"
Climate and anthropogenic controls of coastal deoxygenation on interannual to centennial timescales
"Understanding dissolved oxygen variability in the ocean is limited by the short duration of direct measurements, however sedimentary oxidation-reduction reactions can provide context for modern observations. Here we use bulk sediment redox-sensitive metal enrichment factors (MoEF, ReEF, and UEF) and scanning X-ray fluorescence (XRF) records to examine annual-scale sedimentary oxygen concentrations in the Santa Barbara Basin from the Industrial Revolution (AD ~1850) to present. [...]"
Source: Geophysical Research Letters
Authors: Yi Wang, Ingrid Hendy, Tiffany J. Napier