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Importance of wind and meltwater for observed chemical and physical changes in the Southern Ocean

Abstract.

"The Southern Ocean south of 30° S represents only one-third of the total ocean area, yet absorbs half of the total ocean anthropogenic carbon and over two-thirds of ocean anthropogenic heat. In the past, the Southern Ocean has also been one of the most sparsely measured regions of the global ocean. [...]"

Source: Nature Geoscience
Authors: Ben Bronselaer et al.
DOI: 10.1038/s41561-019-0502-8

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Extensive marine anoxia associated with the Late Devonian Hangenberg Crisis

Abstract.

"The global Hangenberg Crisis near the Devonian-Carboniferous boundary (DCB) represents one of the major Phanerozoic mass extinction events, which shaped the roots of modern vertebrate biodiversity. Marine anoxia has been cited as the proximate kill mechanism for this event. However, the detailed timing, duration, and extent of global marine redox chemistry changes across this critical interval remain controversial because most of the studies to date only constrain changes in local or regional redox chemistry. [...]"

Source: Earth and Planetary Science Letters
Authors: Feifei Zhang et al.
DOI: 10.1016/j.epsl.2019.115976

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Larval Fish Habitats and Deoxygenation in the Northern Limit of the Oxygen Minimum Zone off Mexico

Abstract.

"The present state of deoxygenation in the northern limits of the shallow oxygen minimum zone off Mexico is examined in order to detect its effects on larval fish habitats and consider the sensitivity of fish larvae to decreased dissolved oxygen. A series of cruises between 2000 and 2017 indicated a significant vertical expansion of low oxygen waters. The upper limit of suboxic conditions (<4.4 μmol/kg) has risen ~100 m at 19.5°N off Cabo Corrientes and ~50 m at 25°N in the mouth of the Gulf of California. The larval habitat distribution was related to the geographic variability of dissolved oxygen and water masses between these two latitudes. [...]"

Source: JGR Oceans
Authors: Laura Sánchez‐Velasco et al.
DOI: 10.1029/2019JC015414

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Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

Abstract.

"The ocean is the main source of thermal inertia in the climate system. Ocean heat uptake during recent decades has been quantified using ocean temperature measurements. However, these estimates all use the same imperfect ocean dataset and share additional uncertainty due to sparse coverage, especially before 2007. Here, we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2) – levels of which increase as the ocean warms and releases gases – as a whole ocean thermometer. [...]"

Source: Scientific Reports
Authors: L. Resplandy et al.
DOI: 10.1038/s41598-019-56490-z

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Climate Change and Harmful Algal Blooms: Insights and perspective

Abstract.

"Climate change is transforming aquatic ecosystems. Coastal waters have experienced progressive warming, acidification, and deoxygenation that will intensify this century. At the same time, there is a scientific consensus that the public health, recreation, tourism, fishery, aquaculture, and ecosystem impacts from harmful algal blooms (HABs) have all increased over the past several decades. [...]"

Source: Harmful Algae
Author: Author links open overlay panelChristopher J.Gobler
DOI: 10.1016/j.hal.2019.101731

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Greenhouse Gas Emissions From Native and Non-native Oysters

Abstract.

"Non-native species introductions are associated with a range of ecosystem changes such as habitat destruction, competition with native species, and biodiversity losses. Less well known is the role non-native species play in altering biogeochemical processes, such as the emission of greenhouse gases (GHGs). In this study we used laboratory incubations to compare seasonal (spring, summer, fall) emissions of the GHGs nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) from native (Crassostrea virginica) and non-native (Ostrea edulis) oysters collected from a northern temperate estuary (Duxbury Bay, Massachusetts, USA). [...]"

Source: Frontiers in Environmental Science
Authors: Gretchen J. McCarthy et al.
DOI: 10.3389/fenvs.2019.00194

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Greenhouse gas cycling by the plastisphere: The sleeper issue of plastic pollution

Abstract.

"Plastic is an allochthonous material to marine ecosystems but is rapidly colonized by marine microbial communities, with an as yet unclear contribution to biogeochemical cycles. In this study, we investigated the influence of an active microbial community grown on microplastic particles (the plastisphere) on CO2 and N2O recycling and its potential role in greenhouse gas inventories and air-sea exchange. Microplastics were collected during two cruises (Cimar 21 and FIP Montes Submarinos) from the surface layer (5 m depth) from several contrasting trophic regions of the South Pacific Ocean, i.e., from a transition zone off the eutrophic coastal upwelling of Chile, to a mesotrophic transition area of oceanic seamounts and, finally, to an oligotrophic zone in the South Pacific Subtropical Gyre. [...]"

Source: Chemosphere
Authors: MarcelaCornejo-D’Ottone et al.
DOI: 10.1016/j.chemosphere.2019.125709

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Denitrification Aligns with N2 Fixation in Red Sea Corals

Abstract.

"Denitrification may potentially alleviate excess nitrogen (N) availability in coral holobionts to maintain a favourable N to phosphorous ratio in the coral tissue. However, little is known about the abundance and activity of denitrifiers in the coral holobiont. The present study used the nirS marker gene as a proxy for denitrification potential along with measurements of denitrification rates in a comparative coral taxonomic framework from the Red Sea: Acropora hemprichiiMillepora dichotoma, and Pleuractis granulosa. [...]"

Source: Scientific Reports
Authors: Arjen Tilstra et al.
DOI: 10.1038/s41598-019-55408-z

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Warming climate will impact dead zones in Chesapeake Bay

"In recent years, scientists have projected increasingly large summer dead zones in the Chesapeake Bay, areas where there is little or no oxygen for living things like crabs and fish to thrive, even as long-term efforts to reduce nutrient pollution continue. Researchers factored in local impacts of climate change to make projections of what the oxygen content of the Chesapeake Bay will look like in the future. [...]"

Source: Science Daily

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Intensified ocean deoxygenation during the end Devonian mass extinction

Abstract.

"The end‐Devonian mass extinction (~359 Ma) substantially impacted marine ecosystems and shaped the roots of modern vertebrate biodiversity. Although multiple hypotheses have been proposed, no consensus has been reached about the mechanism inducing this extinction event. In this study, I/Ca ratio of carbonate was used to unravel the changes in local oxygen content of the upper water column during this critical interval. The Devonian‐Carboniferous boundary was recorded in two shallow water carbonate sections in South China. [...]"

Source: Geochemistry, Geophysics, Geosystems
Authors: Jiangsi Liu et al.
DOI: 10.1029/2019GC008614

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