News

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: Christopher 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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Post-depositional manganese mobilization during the last glacial period in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean

Abstract.

"Numerous studies have provided compelling evidence that the Pacific Ocean has experienced substantial glacial/interglacial changes in bottom-water oxygenation associated with enhanced carbon dioxide storage in the glacial deep ocean. Under postulated low glacial bottom-water oxygen concentrations (O2bw), redox zonation, biogeochemical processes and element fluxes in the sediments must have been distinctively different during the last glacial period (LGP) compared to current well-oxygenated conditions. [...]"

Source: Earth and Planetary Science Letters
Authors: Jessica B.Volz et al.
DOI: 10.1016/j.epsl.2019.116012

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Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling

Abstract.

"Oxygenation of Earth’s atmosphere and oceans occurred across three major steps during the Paleoproterozoic, Neoproterozoic, and Paleozoic eras, with each increase having profound consequences for the biosphere. Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks in the long-term biogeochemical cycles of carbon, oxygen, and phosphorus, and that there is no requirement for a specific stepwise external forcing to explain the course of Earth surface oxygenation. [...]"

Source: Science
Authors: Lewis J. Alcott et al.
DOI: 10.1126/science.aax6459

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Multidisciplinary Observing in the World Ocean’s Oxygen Minimum Zone Regions: From Climate to Fish — The VOICE Initiative

Abstract.

"Multidisciplinary ocean observing activities provide critical ocean information to satisfy ever-changing socioeconomic needs and require coordinated implementation. The upper oxycline (transition between high and low oxygen waters) is fundamentally important for the ecosystem structure and can be a useful proxy for multiple observing objectives connected to eastern boundary systems (EBSs) that neighbor oxygen minimum zones (OMZs). [...]"

Source: Frontiers in Marine Science
Authors: Véronique Garçon et al.
DOI: 10.3389/fmars.2019.00722

Read the full article here.


Dark carbon fixation in the Arabian Sea oxygen minimum zone contributes to sedimentary organic carbon (SOM)

Abstract.

"In response to rising CO2 concentrations and increasing global sea surface temperatures, oxygen minimum zones (OMZ), or “dead zones”, are expected to expand. OMZs are fueled by high primary productivity, resulting in enhanced biological oxygen demand at depth, subsequent oxygen depletion, and attenuation of remineralization. This results in the deposition of organic carbon‐rich sediments. Carbon drawdown is estimated by biogeochemical models; however, a major process is ignored: carbon fixation in the mid‐ and lower water column. [...]"

Source: Global Biogeochemical Cycles
Authors: Sabine K. Lengger et al.
DOI: 10.1029/2019GB006282

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‘Dead zones’ expanding rapidly in oceans as climate emergency causes unprecedented oxygen loss

"“Dead zones” are rapidly appearing in the world’s oceans as they lose oxygen at an unprecedented rate due to climate change, sewage pollution and farming practices, presenting an existential threat to marine life and ecosystems, according to a vast new study.

The overall level of oxygen in the oceans has dropped by roughly 2 per cent, while the number of known hypoxic “dead zones” – where oxygen levels are dangerously low – has skyrocketed from 45 known sites in the 1960s to at least 700 areas now dangerously devoid of the life-giving compound, some encompassing thousands of square miles. [...]"

Source: The Independent

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World’s Oceans Are Losing Oxygen Rapidly, Study Finds

"The world’s oceans are gasping for breath, a report issued Saturday at the annual global climate talks in Madrid has concluded.

The report represents the combined efforts of 67 scientists from 17 countries and was released by the International Union for Conservation of Nature. It found that oxygen levels in the world’s oceans declined by roughly 2 percent between 1960 and 2010. The decline, called deoxygenation, is largely attributed to climate change, although other human activities are contributing to the problem. One example is so-called nutrient runoff, when too many nutrients from fertilizers used on farms and lawns wash into waterways. [...]"

Source: The New York Times

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Ocean deoxygenation : everyone’s problem

Abstract.

"The ocean represents 97% of the physical habitable space on the planet and is central to sustaining all life on Earth. Since 2000 significant and dedicated effort has been directed at raising awareness and understanding of the consequences of greenhouse gas emissions on the ocean. Carbon dioxide emitted by human activities is driving the ocean towards more acidic conditions. Only in the past decade has it started to become more widely recognized that the temperature of the global ocean is also being significantly affected as a result of the effect that the carbon dioxide and other potent greenhouse gases are having in the Earth’s atmosphere. [...]"

Source: IUCN
Authors: D. Laffoley and J. M. Baxter
DOI: 10.2305/IUCN.CH.2019.13.en

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Diel and tidal pCO2 × O2 fluctuations provide physiological refuge to early life stages of a coastal forage fish

Abstract.

"Coastal ecosystems experience substantial natural fluctuations in pCO2 and dissolved oxygen (DO) conditions on diel, tidal, seasonal and interannual timescales. Rising carbon dioxide emissions and anthropogenic nutrient input are expected to increase these pCO2 and DO cycles in severity and duration of acidification and hypoxia. [...]"

Source: Scientific Reports
Authors: Emma L. Cross et al.
DOI: 10.1038/s41598-019-53930-8

Read the full article here.


Spatiotemporal redox heterogeneity and transient marine shelf oxygenation in the Mesoproterozoic ocean

Abstract.

"The Mesoproterozoic Era (1.6-1.0 Ga), long regarded as an interval of sluggish biotic evolution and persistently low atmospheric-oceanic oxygen levels, has become the subject of recent controversy regarding putative large-scale oxygenation events. In this study, we conducted a comprehensive investigation of redox, productivity, seawater sulfate concentrations, and hydrographic conditions for the ∼1.4-1.32-Ga Xiamaling Formation in the shallow Hougou and mid-depth Huangtugui sections in the Yanshan Basin (North China). [...]"

Source: Geochimica et Cosmochimica Acta
Authors: HaiyangWang et al.
DOI: 10.1016/j.gca.2019.11.028

Read the full article here.


Ocean acidification – a silently progressing crisis

"Ocean warming, acidification, deoxygenation, and marine heatwaves are all pressing marine issues that are quietly intensifying around the world. These challenges are diverse and occur on a massive scale, making it difficult for people to understand the full extent of the problem. To shed some light on this topic, the Sasakawa Peace Foundation (SPF) spoke with Mr. Tsunoda, Senior Research Fellow at the Ocean Policy Research Institute (OPRI). [...]"

Source: Sasakawa Peace Foundation

Read the full article here.


Marine animals hold promise for extending ocean monitoring

"An international team of researchers led by the University of Exeter suggests that a wide variety of marine species could be used for monitoring the world's oceans. Using electronic tags, scientists could exploit the natural behavior of sharks, penguins, turtles, seals and other species to fill gaps in our knowledge of the seas.

With three-quarters of the Earth's surface covered with water, having a comprehensive understanding of the oceans is very important in dealing with everything from fishing quotas to climate change. The problem is that the oceans are much bigger than most people realize and many parts aren't easily, if at all, accessible."

Source: New Atlas

Read the full article here.


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