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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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Projections of climate-driven changes in tuna vertical habitat based on species-specific differences in blood oxygen affinity

Abstract.

"Oxygen concentrations are hypothesized to decrease in many areas of the ocean as a result of anthropogenically driven climate change, resulting in habitat compression for pelagic animals. The oxygen partial pressure, pO2, at which blood is 50% saturated (P50) is a measure of blood oxygen affinity and a gauge of the tolerance of animals for low ambient oxygen. Tuna species display a wide range of blood oxygen affinities (i.e., P50 values) and therefore may be differentially impacted by habitat compression as they make extensive vertical movements to forage on subdaily time scales. [...]"

Source: Global Change Biology
Authors: K. A. S. Mislan et al.
DOI: 10.1111/gcb.13799

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Ecophenotypic responses of benthic foraminifera to oxygen availability along an oxygen gradient in the California Borderland

Abstract.

"Spatial variation in environmental conditions can elicit predictable size and morphological responses in marine organisms through influences on physiology. Thus, spatial and temporal variation in marine organism size and shape are often used to infer paleoenvironmental conditions, such as dissolved oxygen concentrations. Benthic foraminifera commonly serve as a tool for reconstructing past ocean oxygen levels. [...]" 

Source: marine ecology
Authors: Caitlin R. Keating-Bitonti, Jonathan L. Payne
DOI: 10.1111/maec.12430

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Metabolic Roles of Uncultivated Bacterioplankton Lineages in the Northern Gulf of Mexico “Dead Zone”

Abstract.

"Marine regions that have seasonal to long-term low dissolved oxygen (DO) concentrations, sometimes called “dead zones,” are increasing in number and severity around the globe with deleterious effects on ecology and economics. One of the largest of these coastal dead zones occurs on the continental shelf of the northern Gulf of Mexico (nGOM), which results from eutrophication-enhanced bacterioplankton respiration and strong seasonal stratification. [...]"

Source: mBio
Authors: J. Cameron Thrash et al.
DOI: 10.1128/mBio.01017-17

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Spatial Patterns of Groundwater Biogeochemical Reactivity in an Intertidal Beach Aquifer

Abstract.

"Beach aquifers host a dynamic and reactive mixing zone between fresh and saline groundwater of contrasting origin and composition. Seawater, driven up the beachface by waves and tides, infiltrates into the aquifer and meets the seaward-discharging fresh groundwater, creating and maintaining a reactive intertidal circulation cell. Within the cell, land-derived nutrients delivered by fresh groundwater are transformed or attenuated. We investigated this process by collecting porewater samples from multi-level wells along a shore-perpendicular transect on a beach near Cape Henlopen, Delaware and analyzing solute and particulate concentrations. [...]"

Source: Biogeosciences
Authors: Kyra H. Kim
DOI: 10.1002/2017JG003943

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Short-term variability of dissolved rare earth elements and neodymium isotopes in the entire water column of the Panama Basin

Abstract.

"The distribution of dissolved rare earth elements (REEs) and neodymium isotopes (εNd) in the open ocean traces water mass mixing and provides information on lithogenic inputs to the source regions of the water masses. However, the processes influencing the REE budget at the ocean margins, in particular source and sink mechanisms, are not yet well quantified. In this study the first dissolved REE concentrations and Nd isotope compositions of seawater from the Panama Basin (RV Meteor cruise M90) in the Eastern Equatorial Pacific (EEP) are presented. The EEP is characterized by one of the world's largest oxygen minimum zones (OMZs). It is dominated by high particle fluxes that are expected to enhance the removal of REEs from the water column by scavenging. [...]"

Source: Earth and Planetary Science Letters
Authors: P.Grasse et al.
DOI: 10.1016/j.epsl.2017.07.022

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Intense oceanic uptake of oxygen during 2014–2015 winter convection in the Labrador Sea

Abstract.

"Measurements of near-surface oxygen (O2) concentrations and mixed layer depth from the K1 mooring in the central Labrador Sea are used to calculate the change in column-integrated (0–1700 m) O2 content over the deep convection winter 2014/2015. During the mixed layer deepening period, November 2014 to April 2015, the oxygen content increased by 24.3 ± 3.4 mol m−2, 40% higher than previous results from winters with weaker convection. By estimating the contribution of respiration and lateral transport on the oxygen budget, the cumulative air-sea gas exchange is derived. [...]"

Source: Geophysical Research Letters
Authors: Jannes Koelling, Douglas W. R. Wallace, Uwe Send, Johannes Karstensen
DOI: 10.1002/2017GL073933

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Taking a deep breath? Scientists measure unusually high oxygen uptake in the Labrador Sea

"The Labrador Sea in the North Atlantic is one of the few areas in the world ocean where cold, saline seawater sinks to large depths and forms deep water. This convection process also transports oxygen into the deep sea. A team of scientists from Scripps Institution of Oceanography (San Diego, California), Dalhousie University (Halifax, Canada) and GEOMAR Helmholtz Centre for Ocean Research Kiel have now published the analysis of data obtained from the mooring K1 in the international scientific journal Geophysical Research Letters. [...]"

Source: phys.org

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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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Widespread seawater circulation in 18–22 Ma oceanic crust: Impact on heat flow and sediment geochemistry

Abstract.

"On the basis of heat-flow measurements, seismic mapping, and sediment pore-water analysis, we demonstrate widespread and efficient ventilation of the 18–22 Ma oceanic crust of the northeast equatorial Pacific Ocean. Recharge and discharge appear to be associated with basement outcrops, including seamounts and north-south–trending faults, along which sediment cover thins out and volcanic rocks are exposed. Low-temperature hydrothermal circulation through the volcanic crust leads to the reduction of heat flow through overlying sediments, with measured heat-flow values that are well below those expected from conductive cooling curves for lithosphere of this age. [...]"

Source: Geology
Authors: Thomas Kuhn et al.
DOI: 10.1130/G39091.1

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