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Methane fluxes from coastal sediments are enhanced by macrofauna

Abstract.

"Methane and nitrous oxide are potent greenhouse gases (GHGs) that contribute to climate change. Coastal sediments are important GHG producers, but the contribution of macrofauna (benthic invertebrates larger than 1 mm) inhabiting them is currently unknown. Through a combination of trace gas, isotope, and molecular analyses, we studied the direct and indirect contribution of two macrofaunal groups, polychaetes and bivalves, to methane and nitrous oxide fluxes from coastal sediments. [...]"

Source: Scientific Reports
Authors: Stefano Bonaglia et al.
DOI: 10.1038/s41598-017-13263-w

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Pteropods are excellent recorders of surface temperature and carbonate ion concentration

Abstract.

"Pteropods are among the first responders to ocean acidification and warming, but have not yet been widely explored as carriers of marine paleoenvironmental signals. In order to characterize the stable isotopic composition of aragonitic pteropod shells and their variation in response to climate change parameters, such as seawater temperature, pteropod shells (Heliconoides inflatus) were collected along a latitudinal transect in the Atlantic Ocean (31° N to 38° S). [...]"

Source: Scientific Reports
Authors: N. Keul et al.
DOI: 10.1038/s41598-017-11708-w

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The possible roles of algae in restricting the increase in atmospheric CO2 and global temperature

Abstract.

"Anthropogenic inputs are increasing the CO2 content of the atmosphere, and the CO2 and total inorganic C in the surface ocean and, to a lesser degree, the deep ocean. The greenhouse effect of the increased CO2 (and, to a lesser extent, other greenhouse gases) is very probably the major cause of present global warming. The warming increases temperature of the atmosphere and the surface ocean to a greater extent than the deep ocean, with shoaling of the thermocline, decreasing nutrient flux to the surface ocean where there is greater mean photosynthetic photon flux density. [...]"

Source: European Journal of Phycology 
Author: John A. Raven
DOI: 10.1080/09670262.2017.1362593

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Biodiversity response to natural gradients of multiple stressors on continental margins

Abstract.

"Sharp increases in atmospheric CO2 are resulting in ocean warming, acidification and deoxygenation that threaten marine organisms on continental margins and their ecological functions and resulting ecosystem services. The relative influence of these stressors on biodiversity remains unclear, as well as the threshold levels for change and when secondary stressors become important.  [...]"

Source: Proceedings of the Royal Society B
Authors: Erik A. Sperling, Christina A. Frieder, Lisa A. Levin
DOI: 10.1098/rspb.2016.0637

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Role of zooplankton in determining the efficiency of the biological carbon pump

Abstract.

"The efficiency of the ocean's biological carbon pump (BCPeff – here the product of particle export and transfer efficiencies) plays a key role in the air–sea partitioning of CO2. Despite its importance in the global carbon cycle, the biological processes that control BCPeff are poorly known. We investigate the potential role that zooplankton play in the biological carbon pump using both in situ observations and model output. Observed and modelled estimates of fast, slow, and total sinking fluxes are presented from three oceanic sites: the Atlantic sector of the Southern Ocean, the temperate North Atlantic, and the equatorial Pacific oxygen minimum zone (OMZ)."

Source: Biogeosciences
Authors: Emma L. Cavan et al.
DOI: 10.5194/bg-14-177-2017

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Microbial oxidation as a methane sink beneath the West Antarctic Ice Sheet

Anstract.

"Aquatic habitats beneath ice masses contain active microbial ecosystems capable of cycling important greenhouse gases, such as methane (CH4). A large methane reservoir is thought to exist beneath the West Antarctic Ice Sheet, but its quantity, source and ultimate fate are poorly understood. For instance, O2 supplied by basal melting should result in conditions favourable for aerobic methane oxidation. Here we use measurements of methane concentrations and stable isotope compositions along with genomic analyses to assess the sources and cycling of methane in Subglacial Lake Whillans (SLW) in West Antarctica. [...]"

Source: Nature Geoscience
Authors: Alexander B. Michaud et al.
DOI: 10.1038/ngeo2992

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Influence of seaway changes during the Pliocene on tropical Pacific climate in the Kiel climate model

 Mean state, annual cycle, ENSO, and their interactions

Abstract.

"The El Niño/Southern Oscillation (ENSO) is the leading mode of tropical Pacific interannual variability in the present-day climate. Available proxy evidence suggests that ENSO also existed during past climates, for example during the Pliocene extending from about 5.3 million to about 2.6 million years BP. Here we investigate the influences of the Panama Seaway closing and Indonesian Passages narrowing, and also of atmospheric carbon dioxide (CO2) on the tropical Pacific mean climate and annual cycle, and their combined impact on ENSO during the Pliocene. [...]"

Source: Climate Dynamics
Authors: Zhaoyang Song, Mojib Latif, Wonsun Park, Uta Krebs-Kanzow, Birgit Schneider
DOI: 10.1007/s00382-016-3298-x

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Deep-ocean dissolved organic matter reactivity along the Mediterranean Sea: does size matter?

Abstract.

"Despite of the major role ascribed to marine dissolved organic matter (DOM) in the global carbon cycle, the reactivity of this pool in the dark ocean is still poorly understood. Present hypotheses, posed within the size-reactivity continuum (SRC) and the microbial carbon pump (MCP) conceptual frameworks, need further empirical support. Here, we provide field evidence of the soundness of the SRC model. We sampled the high salinity core-of-flow of the Levantine Intermediate Water along its westward route through the entire Mediterranean Sea. At selected sites, DOM was size-fractionated in apparent high (aHMW) and low (aLMW) molecular weight fractions using an efficient ultrafiltration cell. [...]"

Source: Scientific Reports
Authors: Alba María Martínez-Pérez, Xosé Antón Álvarez-Salgado, Javier Arístegui & Mar Nieto-Cid
DOI: 10.1038/s41598-017-05941-6

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Persistent spatial structuring of coastal ocean acidification in the California Current System

Abstract.

"The near-term progression of ocean acidification (OA) is projected to bring about sharp changes in the chemistry of coastal upwelling ecosystems. The distribution of OA exposure across these early-impact systems, however, is highly uncertain and limits our understanding of whether and how spatial management actions can be deployed to ameliorate future impacts. Through a novel coastal OA observing network, we have uncovered a remarkably persistent spatial mosaic in the penetration of acidified waters into ecologically-important nearshore habitats across 1,000 km of the California Current Large Marine Ecosystem.  [...]"

Source: Scientific Reports
Authors: F. Chan et al.
DOI: 10.1038/s41598-017-02777-y

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The geologic history of seawater pH

Abstract.  

"Although pH is a fundamental property of Earth’s oceans, critical to our understanding of seawater biogeochemistry, its long-timescale geologic history is poorly constrained. We constrain seawater pH through time by accounting for the cycles of the major components of seawater. We infer an increase from early Archean pH values between ~6.5 and 7.0 and Phanerozoic values between ~7.5 and 9.0, which was caused by a gradual decrease in atmospheric pCO2 in response to solar brightening, alongside a decrease in hydrothermal exchange between seawater and the ocean crust. [...]"

Source: Science Vol. 355
Authors: I. Halevy, A. Bachan
DOI: 10.1126/science.aal4151

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