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Phytoplankton calcifiers control nitrate cycling and the pace of transition in warming icehouse and cooling greenhouse climates

Abstract.

"Phytoplankton calcifiers contribute to global carbon cycling through their dual formation of calcium carbonate and particulate organic carbon (POC). The carbonate might provide an efficient export pathway for the associated POC to the deep ocean, reducing the particles' exposure to biological degradation in the upper ocean and increasing the particle settling rate. Previous work has suggested ballasting of POC by carbonate might increase in a warming climate, in spite of increasing carbonate dissolution rates, because calcifiers benefit from the widespread nutrient limitation arising from stratification. [...]"

Source: Biogeosciences
Authors: Karin F. Kvale et al.
DOI: 10.5194/bg-16-1019-2019

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The microbiomes of deep-sea hydrothermal vents: distributed globally, shaped locally

Abstract.

"The discovery of chemosynthetic ecosystems at deep-sea hydrothermal vents in 1977 changed our view of biology. Chemosynthetic bacteria and archaea form the foundation of vent ecosystems by exploiting the chemical disequilibrium between reducing hydrothermal fluids and oxidizing seawater, harnessing this energy to fix inorganic carbon into biomass. [...]"

Source: Nature Reviews Microbiology
Author: Gregory J. Dick
DOI: 10.1038/s41579-019-0160-2

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Uncovering mechanisms of global ocean change effects on the Dungeness crab (Cancer magister) through metabolomics analysis

Abstract.

"The Dungeness crab is an economically and ecologically important species distributed along the North American Pacific coast. To predict how Dungeness crab may physiologically respond to future global ocean change on a molecular level, we performed untargeted metabolomic approaches on individual Dungeness crab juveniles reared in treatments that mimicked current and projected future pH and dissolved oxygen conditions. We found 94 metabolites and 127 lipids responded in a condition-specific manner, with a greater number of known compounds more strongly responding to low oxygen than low pH exposure. [...]"

Source: bioRxiv
Authors: Shelly A. Trigg et al.
DOI: 10.1101/574798

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Bacterial fermentation and respiration processes are uncoupled in anoxic permeable sediments

Abstract.

"Permeable (sandy) sediments cover half of the continental margin and are major regulators of oceanic carbon cycling. The microbial communities within these highly dynamic sediments frequently shift between oxic and anoxic states, and hence are less stratified than those in cohesive (muddy) sediments. A major question is, therefore, how these communities maintain metabolism during oxic–anoxic transitions. [...]"

Source: Nature Microbiology
Authors: Adam J. Kessler et al.
DOI: 10.1038/s41564-019-0391-z

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Seasonal Variability of the Mauritania Current and Hydrography at 18°N

Abstract.

"Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. [...]"

Source: JGR Oceans
Authors: T. Klenz, M. Dengler and P. Brandt
DOI: 10.1029/2018JC014264

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Efficient recycling of nutrients in modern and past hypersaline environments

Abstract.

"The biogeochemistry of hypersaline environments is strongly influenced by changes in biological processes and physicochemical parameters. Although massive evaporation events have occurred repeatedly throughout Earth history, their biogeochemical cycles and global impact remain poorly understood. Here, we provide the first nitrogen isotopic data for nutrients and chloropigments from modern shallow hypersaline environments (solar salterns, Trapani, Italy) and apply the obtained insights to δ15N signatures of the Messinian salinity crisis (MSC) in the late Miocene. [...]"

Source: Scientific Reports
Authors: Y. Isaji et al.
DOI: 10.1038/s41598-019-40174-9

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Diversity of culturable Sulphur-oxidising bacteria in the oxygen minimum zones of the northern Indian Ocean

Abstract.

"Oxygen minimum zones (OMZs) are unique, widely spread and well-studied features of the global ocean, varying in seasonality and intensity. The Northern Indian Ocean contains OMZs in the Arabian Sea (AS-OMZ) and the Bay of Bengal (BB-OMZ) having unique biogeochemical features. OMZ water column harbours distinct microbial communities that play vital roles in ocean biogeochemical cycles. Sulphur cycling processes facilitated by OMZ microbial communities are poorly understood with regards to different microbial groups involved, spatially and temporally. [...]"

Source: Journal of Marine Systems (2018)
Authors: Larissa Menezes et al.
DOI: 10.1016/j.jmarsys.2018.05.007

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Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone

Abstract.

"Oxygen minimum zones are expanding globally, and at present account for around 20–40% of oceanic nitrogen loss. Heterotrophic denitrification and anammox—anaerobic ammonium oxidation with nitrite—are responsible for most nitrogen loss in these low-oxygen waters. Anammox is particularly significant in the eastern tropical South Pacific, one of the largest oxygen minimum zones globally. "

Source: Nature Geoscience (2013)
Authors: Tim Kalvelage et al.
DOI: 10.1038/ngeo1739

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'Dead zone' volume more important than area to fish, fisheries

Dubravko Justic, the Texaco Distinguished Professor in the LSU Department of Oceanography & Coastal Sciences, and Research Associate Lixia Wang recently co-authored a study suggesting that measuring the volume rather than the area of the Gulf of Mexico's dead zone, is more appropriate for monitoring its effects on marine organisms.

 

"The dead zone, a hypoxic zone, is a region of low oxygen that results from runoff of high nutrients, such as nitrogen and phosphorus, often found in fertilizer, flowing from the Mississippi River into the coastal ocean. It is the largest recurring hypoxic zone in the U.S., occurring most summers, and is located off the coast of Louisiana. This nutrient pollution, coupled with other factors, is believed to have a negative impact on fisheries because it depletes the oxygen required to support most marine life in bottom and near-bottom waters. [...]"

Source: Science Daily

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The Ocean Is Running Out of Breath, Scientists Warn

Widespread and sometimes drastic marine oxygen declines are stressing sensitive species—a trend that will continue with climate change

"Escaping predators, digestion and other animal activities—including those of humans—require oxygen. But that essential ingredient is no longer so easy for marine life to obtain, several new studies reveal.

In the past decade ocean oxygen levels have taken a dive—an alarming trend that is linked to climate change, says Andreas Oschlies, an oceanographer at the Helmholtz Center for Ocean Research Kiel in Germany, whose team tracks ocean oxygen levels worldwide. “We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are,” he says. [...]"

Source: Scientific American
Author: Laura Poppick

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