News

Biogeochemical role of subsurface coherent eddies in the ocean: Tracer cannonballs, hypoxic storms, and microbial stewpots?

Abstract.

"Subsurface coherent eddies are well-known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here, we use a global eddying (0.1° ) ocean-biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS), and quantify their biogeochemical effects as they propagate westward into the subtropical gyres.  [...]"

Source: Global Biogeochemical Cycles
Authors: Ivy Frenge et al.
DOI: 10.1002/2017GB005743


Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification

Abstract.

"At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific.  [...]"

Source: Biogeosciences
Authors: Birgit Gaye et al.
DOI: 10.5194/bg-15-507-2018

Read the full article here.


New measurement technology helps to determine NO concentrations in the ocean

"Nitrogen monoxide (NO) belongs to the group of nitrogen oxides which are infamous as toxic emissions in urban agglomerations. But NO is also produced in nature and plays a role in the nitrogen cycle. However, from earth's largest ecosystem, the ocean, we have hardly any NO measurements."

Source: Science Daily

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Nitric oxide (NO) in the oxygen minimum zone off Peru

Abstract.

"Nitric oxide (NO) is a short-lived compound of the marine nitrogen cycle. However, measurements of NO in seawater are analytically challenging and our knowledge about its oceanic distribution is, therefore, rudimentary. NO was measured in the oxygen minimum zone (OMZ) of the eastern tropical South Pacific Ocean (ETSP) off Peru during R/V Meteor cruise M93 in February/March 2013. [...]"

Source: Deep Sea Research Part II: Topical Studies in Oceanography
Authors: Hannah E. Lutterbeck et al.
DOI: 10.1016/j.dsr2.2017.12.023

Read the full article here.


Insights into the metabolic functioning of a multipartner ciliate symbiosis from oxygen-depleted sediments

Abstract.

"Symbioses between anaerobic or microaerophilic protists and prokaryotes are common in anoxic and oxygen-depleted habitats ranging from marine sediments to gastrointestinal tracts. Nevertheless, little is known about the mechanisms of metabolic interaction between partners. In these putatively syntrophic associations, consumption of fermentative end products (e.g., hydrogen) by the prokaryotic symbionts is thought to facilitate protistan anaerobic metabolism.  [...]"

Source: Molecular Ecology
Authors: R. A. Beinart et al.
DOI: 10.1111/mec.14465

Read the full article here.


Mn∕Ca intra- and inter-test variability in the benthic foraminifer Ammonia tepida

Abstract.

"The adaptation of some benthic foraminiferal species to low-oxygen conditions provides the prospect of using the chemical composition of their tests as proxies for bottom water oxygenation. Manganese may be particularly suitable as such a geochemical proxy because this redox element is soluble in reduced form (Mn2+) and hence can be incorporated into benthic foraminiferal tests under low-oxygen conditions. [...]"

Source: Biogeosciences
Authors: Jassin Petersen et al.
DOI: 10.5194/bg-15-331-2018

Read the full article here.


Ocean Deoxygenation – Another Global Challenge

"The ocean is facing unprecedented pressures that are causing massive ecosystem and nutrient cycle disruption the result of industrial-scale depletion of ocean wildlife and destabilization of steady-state ecosystems. This occurs not only on the seafloor by trawling, dredging, drilling, and mining but also in the water column with nets, long lines, fish aggregating devices and other techniques; methods introduced in recent decades to extract with unprecedented speed and scale from ecosystems hundreds of millions of years in the making.  [...]"

Source: GIS and Science
Author: Matt Artz
 

Read the full article here.

 


Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum

Abstract.

"The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning, and migrations, but detailed records from tropical regions are lacking. [...]"

Source: Climate of the Past
Authors: Joost Frieling et al.
DOI: 10.5194/cp-14-39-2018

Read the full article here.


Oxygen loss strains marine ecosystems

A new review highlights the impact of declining oxygen levels in the open ocean and coastal waters due to increasing temperatures and nutrient discharge.

 

"Half of the world’s oxygen originates from the ocean. Yet, worldwide, the amount of open ocean without any oxygen has quadrupled over the past 50 years. Oxygen-minimum zones have expanded by several million square kilometres, increasing by more than 10-fold since 1950.  [...]"

Source: nature Middle East
Author: Lakshini Mendis
DOI: 10.1038/nmiddleeast.2018.2

Read the full article here.


Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity

Abstract.

"The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. [...]"

Source: Biogeosciences
Authors: Zouhair Lachkar, Marina Lévy, and Shafer Smith
DOI: 10.5194/bg-15-159-2018

Read the full article here.


A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts

Abstract.

"The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O2) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. [...]"

Source: Nature
Authors: Daniel A. Stolper
DOI: 10.1038/nature25009

Read the full article here.


Oceans suffocating as huge dead zones quadruple since 1950, scientists warn

Areas starved of oxygen in open ocean and by coasts have soared in recent decades, risking dire consequences for marine life and humanity

 

"Ocean dead zones with zero oxygen have quadrupled in size since 1950, scientists have warned, while the number of very low oxygen sites near coasts have multiplied tenfold. Most sea creatures cannot survive in these zones and current trends would lead to mass extinction in the long run, risking dire consequences for the hundreds of millions of people who depend on the sea. [...]"

Source: The Guardian

Read the full article here.


Declining oxygen in the global ocean and coastal waters

Abstract.

"Oxygen is fundamental to life. Not only is it essential for the survival of individual animals, but it regulates global cycles of major nutrients and carbon. The oxygen content of the open ocean and coastal waters has been declining for at least the past half-century, largely because of human activities that have increased global temperatures and nutrients discharged to coastal waters. [...]"

Source: Science
Authors: Denise Breitburg et al.
DOI: 10.1126/science.aam7240

Read the full article here.


Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Abstract.

"The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution."

Source: Biogeosciences
Authors: Thomas W. Trull et al.
DOI: 10.5194/bg-15-31-2018

Read the full article here.


Multifarious anchovy and sardine regimes in the Humboldt Current System during the last 150 years

Abstract.

"The Humboldt Current System (HCS) has the highest production of forage fish in the world, although it is highly variable and the future of the primary component, anchovy, is uncertain in the context of global warming. Paradigms based on late 20th century observations suggest that large-scale forcing controls decadal-scale fluctuations of anchovy and sardine across different boundary currents of the Pacific. We develop records of anchovy and sardine fluctuations since 1860 AD using fish scales from multiple sites containing laminated sediments and compare them with Pacific basin-scale and regional indices of ocean climate variability. [...]"

Source: Global Change Biology
Authors: Renato Salvatteci et al.
DOI: 10.1111/gcb.13991

Read the full article here.


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