News

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
DOI: 10.1126/science.aar5252

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Abyssal ocean overturning shaped by seafloor distribution

Abstract.

"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. [...]"

Source: Nature
Authors: C. de Lavergne et al.
DOI: 10.1038/nature24472

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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. [...]"

Source: new.com.au

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Climate and anthropogenic controls of coastal deoxygenation on interannual to centennial timescales

Abstract.

"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
DOI: 10.1002/2017GL075443

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50-years of data from a 'living oxygen minimum' lab could help predict the oceans' future

"Canadian and US Department of Energy researchers have released 50 years’ worth of data chronicling the deoxygenating cycles of a fjord off Canada’s west coast, and detailing the response of the microbial communities inhabiting the fjord.

The mass of data, collected in two new Nature family papers, could help scientists better predict the impact of human activities and ocean deoxygenation on marine environments. Currently, oxygen minimum zones (OMZs) constitute up to 7 percent of global ocean volume. Continued expansion of OMZs in the northeastern subarctic Pacific has the potential to transport oxygen-depleted waters into coastal regions, adversely affecting nutrient cycles and fisheries productivity. [...]"

Source: University of British Columbia (media contact: Chris Balma)

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The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

Abtract.

"Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). [...]"

Source: Biogeosciences
Authors: Michelle I. Graco et al.
DOI: 10.5194/bg-14-4601-2017

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Monitoring microbial responses to ocean deoxygenation in a model oxygen minimum zone

Abstract.

"Today in Scientific Data, two compendia of geochemical and multi-omic sequence information (DNA, RNA, protein) generated over almost a decade of time series monitoring in a seasonally anoxic coastal marine setting are presented to the scientific community. These data descriptors introduce a model ecosystem for the study of microbial responses to ocean deoxygenation, a phenotype that is currently expanding due to climate change."

Source: Scientific Data
Authors: Steven J. Hallam, Mónica Torres-Beltrán & Alyse K. Hawley
DOI: 10.1038/sdata.2017.158

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Oxygen Minimum Zone Contrasts between the Arabian Sea and the Bay of Bengal Implied by Differences in Remineralization Depth

Abstract.

"The combination of high primary productivity and weak ventilation in the Arabian Sea (AS) and Bay of Bengal (BoB) generates vast areas of depleted oxygen, known as Oxygen Minimum Zones (OMZs). The AS OMZ is the world's thickest and hosts up to 40% of global denitrification. In contrast, the OMZ in the BoB is weaker and denitrification free. Using a series of model simulations, we show that the deeper remineralization depth (RD) in the BoB, potentially associated with organic matter aggregation with riverine mineral particles, contributes to weaken its OMZ. [...]"

Source: Geophysical Research Letters
Authors: Muchamad Al Azhar, Zouhair Lachkar, Marina Lévy, Shafer Smith
DOI: 10.1002/2017GL075157

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Short-term variability of dissolved rare earth elements and neodymium isotopes in the entire water column of the Panama Basin

Abstract.

"The distribution of dissolved rare earth elements (REEs) and neodymium isotopes (εNd) in the open ocean traces water mass mixing and provides information on lithogenic inputs to the source regions of the water masses. However, the processes influencing the REE budget at the ocean margins, in particular source and sink mechanisms, are not yet well quantified. In this study the first dissolved REE concentrations and Nd isotope compositions of seawater from the Panama Basin (RV Meteor cruise M90) in the Eastern Equatorial Pacific (EEP) are presented. The EEP is characterized by one of the world's largest oxygen minimum zones (OMZs). It is dominated by high particle fluxes that are expected to enhance the removal of REEs from the water column by scavenging. [...]"

Source: Earth and Planetary Science Letters
Authors: P.Grasse et al.
DOI: 10.1016/j.epsl.2017.07.022

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Role of zooplankton in determining the efficiency of the biological carbon pump

Abstract.

"The efficiency of the ocean's biological carbon pump (BCPeff – here the product of particle export and transfer efficiencies) plays a key role in the air–sea partitioning of CO2. Despite its importance in the global carbon cycle, the biological processes that control BCPeff are poorly known. We investigate the potential role that zooplankton play in the biological carbon pump using both in situ observations and model output. Observed and modelled estimates of fast, slow, and total sinking fluxes are presented from three oceanic sites: the Atlantic sector of the Southern Ocean, the temperate North Atlantic, and the equatorial Pacific oxygen minimum zone (OMZ)."

Source: Biogeosciences
Authors: Emma L. Cavan et al.
DOI: 10.5194/bg-14-177-2017

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