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


"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


"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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Ocean acidification could doom key Arctic fish species: study

Ocean acidification combined with warming of the world oceans and loss of oxygen is having a severe impact on key Arctic marine species such as polar cod in the Barents Sea, according to a new study conducted by German scientists.


"The eight-year interdisciplinary study, which began in 2009 and involved more than 250 scientist in the German research network on ocean acidification BIOACID (Biological Impacts of Ocean Acidification), investigated how different marine species respond to ocean acidification – a change in the ocean chemistry that occurs when carbon dioxide (CO2) from the atmosphere dissolves in seawater.

In addition to ocean acidification, the study, Exploring Ocean Change: Biological Impacts of Ocean Acidification, also examined the cascading effect of other stressors such as ocean warming, deoxygenation, overfishing and eutrophication – the increased concentration of nutrients in estuaries and coastal waters that causes harmful algal blooms, ocean dead zones and fish kills. [...]"

Source: The Independent Barents Observer

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A strong case for limiting climate change

"As a gigantic carbon sink, the ocean has taken up about a third of the carbon dioxide (CO2) released into the atmosphere by human activities. But when absorbed by seawater, the greenhouse gas triggers chemical reactions, causing the ocean to acidify. Ocean acidification affects ecosystems and important services the ocean provides to humankind. This includes the regulation of the Earth's climate, food provision, recreation as well as biodiversity as a condition for intact and functioning ecosystems. [...]"

Source: EurekAlert

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Impacts of El Niño events on the Peruvian upwelling system productivity


"Every 2–7 years, El Niño events trigger a strong decrease in phytoplankton productivity off Peru, which profoundly alters the environmental landscape and trophic chain of the marine ecosystem. Here we use a regional coupled physical-biogeochemical model to study the dynamical processes involved in the productivity changes during El Nino, with a focus on the strongest events of the 1958–2008 period. Model evaluation using satellite and in situ observations shows that the model reproduces the surface and subsurface interannual physical and biogeochemical variability. [...]"

Source: Journal of Geophysical Research: Oceans
Authors: D. Espinoza-Morriberón
DOI: 10.1002/2016JC012439

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Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystem


"The upwelling system off central Chile (36.5° S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30–50 m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. [...]"

Source: Biogeosciences
Authors: Alexander Galán et al.
DOI: 10.5194/bg-14-4795-2017

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Turbulence and hypoxia contribute to dense zooplankton scattering layers in Patagonian Fjord System


"Abstract. The Puyuhuapi Fjord is an atypical fjord, with two mouths, located in northern Patagonia (44.7° S). One mouth lies to the south, close to the Pacific Ocean, whilst the second connects with the Jacaf Channel to the north where a shallow sill inhibits deep water ventilation contributing to the hypoxic conditions below ~ 100 m depth. Acoustic Doppler Current Profiler moorings, scientific echo sounder transects, and in-situ abundance measurements were used to study zooplankton assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel. […]"

Source: Ocean Science (in review)
Authors: Iván Pérez-Santos et al.
DOI: 10.5194/os-2017-89

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


"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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A Giant Blob of Floodwater From Harvey Is Still Moving Through the Gulf

"The rain began on August 25, and it would fall, remarkably, for four more days. We know now that Hurricane Harvey dumped as much as 60 inches of rain over parts of Texas. Twenty trillion gallons in all. The equivalent of the entire Chesapeake Bay. Enough to push the Earth’s crust down two centimeters. [...]

What oceanographers do know about the interface of freshwater and ocean comes from studying rivers that naturally empty into the sea. The key is density. Because freshwater lacks dissolved salt, it is less dense and floats atop seawater. It becomes a barrier between the air and the ocean water, which can have nasty consequences. “The freshwater sitting on the salty water cuts off the oxygen from the atmosphere getting into the ocean, and then you get the dead zone,” says Steve DiMarco [...]"

Source: The Atlantic

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