News

Nancy Rabalais - The "dead zone" of the Gulf of Mexico

"Ocean expert Nancy Rabalais tracks the ominously named "dead zone" in the Gulf of Mexico -- where there isn't enough oxygen in the water to support life. The Gulf has the second largest dead zone in the world; on top of killing fish and crustaceans, it's also killing fisheries in these waters. Rabalais tells us about what's causing it -- and how we can reverse its harmful effects and restore one of America's natural treasures."

Watch the full TED Talk here.


Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean

Abstract.

"The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. [...]"

Source: Nature Geoscience
Authors: William R. Gray et al.
DOI: 10.1038/s41561-018-0108-6

Read the full article here.


Oxygenation of the Mesoproterozoic ocean and the evolution of complex eukaryotes

Abstract.

"The Mesoproterozoic era (1,600–1,000 million years ago (Ma)) has long been considered a period of relative environmental stasis, with persistently low levels of atmospheric oxygen. There remains much uncertainty, however, over the evolution of ocean chemistry during this period, which may have been of profound significance for the early evolution of eukaryotic life. [...]"

Source: Nature Geoscience
Authors: Kan Zhang
DOI: 10.1038/s41561-018-0111-y

Read the full article here.


Tiny microenvironments in the ocean hold clues to global nitrogen cycle

"Nitrogen is essential to marine life and cycles throughout the ocean in a delicately balanced system. Living organisms--especially marine plants called phytoplankton--require nitrogen in processes such as photosynthesis. In turn, phytoplankton growth takes up carbon dioxide from the atmosphere and helps regulate global climate. [...]"

Source: EruekAlert

Read the full article here.

 


Life on the edge: active microbial communities in the Kryos MgCl2-brine basin at very low water activity

Abstract.

"The Kryos Basin is a deep-sea hypersaline anoxic basin (DHAB) located in the Eastern Mediterranean Sea (34.98°N 22.04°E). It is filled with brine of re-dissolved Messinian evaporites and is nearly saturated with MgCl2-equivalents, which makes this habitat extremely challenging for life. The strong density difference between the anoxic brine and the overlying oxic Mediterranean seawater impedes mixing, giving rise to a narrow chemocline. [...]"

Source: The ISME Journal
Authors: Lea Steinle et al.
DOI: 10.1038/s41396-018-0107-z

Read the full article here.


Multiple episodes of extensive marine anoxia linked to global warming and continental weathering following the latest Permian mass extinction

Abstract.

"Explaining the ~5-million-year delay in marine biotic recovery following the latest Permian mass extinction, the largest biotic crisis of the Phanerozoic, is a fundamental challenge for both geological and biological sciences. Ocean redox perturbations may have played a critical role in this delayed recovery. However, the lack of quantitative constraints on the details of Early Triassic oceanic anoxia (for example, time, duration, and extent) leaves the links between oceanic conditions and the delayed biotic recovery ambiguous. [...]"

Source: Science Advances
Authors: Feifei Zhan et al.
DOI:10.1126/sciadv.1602921

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Ocean euxinia and climate change "double whammy" drove the Late Ordovician mass extinction

Abstract.

"The Late Ordovician mass extinction (LOME, ca. 445 Ma) was the first of the "Big Five" Phanerozoic extinction events and comprised two extinction pulses. Proposed kill mechanisms include glacially induced global cooling and the expansion of water-column anoxia and/or euxinia (sulfidic conditions), but no general consensus has been reached with regard to the precise role of these mechanisms. [...]"

Source: Geology
Authors: Caineng Zou et al.
DOI: 10.1130/G40121.1

Read the full article here.


A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

Abstract.

"Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O2 content following the Great Oxidation Event (GOE), leading to a mid-Proterozoic ocean (ca. 2.0–0.8 Ga) with oxygenated surface waters and predominantly anoxic deep waters. The extent of mid-Proterozoic seafloor anoxia has been recently estimated using mass-balance models based on molybdenum (Mo), uranium (U), and chromium (Cr) enrichments in organic-rich mudrocks (ORM).  [...]"

Source: Geochimica et Cosmochimica Acta
Authors: Alex I.Sheen et al.
DOI: 10.1016/j.gca.2018.01.036

Read the full article here.


The hunt for the most-wanted chemolithoautotrophic spookmicrobes

Abstract.

"Microorganisms are the drivers of biogeochemical methane and nitrogen cycles. Essential roles of chemolithoautotrophic microorganisms in these cycles were predicted long before their identification. Dedicated enrichment procedures, metagenomics surveys and single-cell technologies have enabled the identification of several new groups of most-wanted spookmicrobes, including novel methoxydotrophic methanogens that produce methane from methylated coal compounds and acetoclastic ‘Candidatus Methanothrix paradoxum’, which is active in oxic soils. [...]"

Source: FEMS Microbiology Ecology
Authors: Michiel H in ‘t Zandt et al.
DOI: 10.1093/femsec/fiy064


Latitudinal variations of δ30Si and δ15N signatures along the Peruvian shelf:

quantifying the effects of nutrient utilization versus denitrification over the past 600 years

Abstract. 

"The sedimentary stable nitrogen isotope compositions of bulk organic matter (δ15Nbulk) and silicon isotope composition of diatoms (δ30SiBSi) both mainly reflect the degree of past nutrient utilization by primary producers. However, in ocean areas where anoxic and suboxic conditions prevail, the δ15Nbulk signal ultimately recorded within the sediments is also influenced by water column denitrification causing an increase in the subsurface δ15N signature of dissolved nitrate (δ15NO3) upwelled to the surface. [...]"

Source: Biogeosciences
Authors: Kristin Doering et al.
DOI: 10.5194/bg-2018-118

Read the full article here.


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