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Dissolved Organic Matter Influences N2 Fixation in the New Caledonian Lagoon (Western Tropical South Pacific)

Abstract.

"Specialized prokaryotes performing biological dinitrogen (N2) fixation (“diazotrophs”) provide an important source of fixed nitrogen in oligotrophic marine ecosystems such as tropical and subtropical oceans. In these waters, cyanobacterial photosynthetic diazotrophs are well known to be abundant and active, yet the role and contribution of non-cyanobacterial diazotrophs are currently unclear. The latter are not photosynthetic (here called “heterotrophic”) and hence require external sources of organic matter to sustain N2 fixation.  [...]"

Source: Frontiers in Marine Science
Authors: Mar Benavides et al.
DOI: 10.3389/fmars.2018.00089

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Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone

Abstract.

"Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP‐OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical‐equatorial pathway, and (3) derive a refined annual‐mean oxygen budget for the ESP‐OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical‐equatorial advection, with more than one‐third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). [...]"

Source: Oceans
Authors: P. J. Llanillo et al.
DOI: 10.1002/2017JC013509

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Upper ocean hydrology of the Northern Humboldt Current System at seasonal, interannual and interdecadal scales

Abstract.

"Since the 1960’s, the Instituto del Mar del Perú (IMARPE) collected tens of thousands of in-situ temperature and salinity profiles in the Northern Humboldt Current System (NHCS). In this study, we blend this unique database with the historical in-situ profiles available from the World Ocean Database for the period 1960-2014 and apply a four-dimensional interpolation scheme to construct a seasonal climatology of temperature and salinity of the NHCS [...]"

Source: Progress in Oceanography
Authors: Carmen Grados et al.
DOI: 10.1016/j.pocean.2018.05.005

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Will ocean zones with low oxygen levels expand or shrink?

"Computer simulations show that areas of the ocean that have low levels of dissolved oxygen will expand, but then shrink, in response to global warming — adding to an emerging picture of the finely balanced processes involved.

Global warming has reduced the amount of dissolved oxygen in the ocean by 2% since 1960. A major concern is that the rate of loss of dissolved oxygen has already increased by up to 20% in tropical waters, expanding the volume of regions called oxygen minimum zones (OMZs), where levels of dissolved oxygen are already very low."

Source: Nature
Authors: Laure Resplandy
DOI: 10.1038/d41586-018-05034-y

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Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming

Abstract.

"Dissolved oxygen (O2) is essential for the survival of marine animals. Climate change impacts on future oxygen distributions could modify species biogeography, trophic interactions, biodiversity, and biogeochemistry. The Coupled Model Intercomparison Project Phase 5 models predict a decreasing trend in marine O2 over the 21st century.  [...]"

Source: Global Biogeochemical Cycles
Authors: Weiwei Fu et al.
DOI: 10.1002/2017GB005788

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UNM scientists find widespread ocean anoxia as cause for past mass extinction

"New research sheds light on first of five major mass extinctions

For decades, scientists have conducted research centered around the five major mass extinctions that have shaped the world we live in. The extinctions date back more than 450 million years with the Late Ordovician Mass Extinction to the deadliest extinction, the Late Permian extinction 250 million years ago that wiped out over 90 percent of species. [...]"

Source: EurekAlert!

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Stepwise oxygenation of early Cambrian ocean controls early metazoan diversification

Abstract.

"The Ediacaran–Cambrian transition is a critical period in Earth history, during which both marine environment and life experienced drastic changes. It was suggested that pervasive oxygenation and associated chemical changes in the ocean have potentially triggered the rapid diversification of early Cambrian metazoans. The timing and process of ocean oxygenation, however, have not been well constrained. [...]"

Source: Palaeogeography, Palaeoclimatology, Palaeoecology
Authors: Xiangkuan Zhao et al.
DOI: 10.1016/j.palaeo.2018.05.009

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Oxygen minimum zone cryptic sulfur cycling sustained by offshore transport of key sulfur oxidizing bacteria

Abstract.

"Members of the gammaproteobacterial clade SUP05 couple water column sulfide oxidation to nitrate reduction in sulfidic oxygen minimum zones (OMZs). Their abundance in offshore OMZ waters devoid of detectable sulfide has led to the suggestion that local sulfate reduction fuels SUP05-mediated sulfide oxidation in a so-called “cryptic sulfur cycle”. [...]"

Source: Nature Communications
Authors: Cameron M. Callbeck et al.
DOI: 10.1038/s41467-018-04041-x

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Global Insurance Industry Steps Up to Turn Ocean Risk Into Resilience

At the Ocean Risk Summit in Bermuda, experts gathered to advance a new model for how insurance and reinsurance companies can leverage their products and balance sheets to restore marine ecosystems and slow climate change impacts.

"When Hurricane Irma smashed into the British Virgin Islands last September at speeds faster than a jumbo jet at takeoff, the devastation was total. The storm caused damage valued at three times more than the Caribbean islands’ entire gross domestic product, while the territory’s economy – including its biggest industry, tourism – shut down for months. [...]"

Source: Oceans Deeply

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The Baltic Sea as a time machine for the future coastal ocean

Abstract.

"Coastal global oceans are expected to undergo drastic changes driven by climate change and increasing anthropogenic pressures in coming decades. Predicting specific future conditions and assessing the best management strategies to maintain ecosystem integrity and sustainable resource use are difficult, because of multiple interacting pressures, uncertain projections, and a lack of test cases for management. [...]"

Source: Science Advances
Authors: Thorsten B. H. Reusch et al.
DOI: 10.1126/sciadv.aar8195

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