Impacts of hypoxic events surpass those of future ocean warming and acidification
"Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control–treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic events (1–3.5 O2 mg l−1) with those experimentally yielded by ocean warming (+4 °C) and acidification (−0.4 units) conditions[...]"
Source: Nature Ecology & Evolution
Authors: Eduardo Sampaio et al.
Ocean acidification may slow the pace of tropicalization of temperate fish communities
"Poleward range extensions by warm-adapted sea urchins are switching temperate marine ecosystems from kelp-dominated to barren-dominated systems that favour the establishment of range-extending tropical fishes. Yet, such tropicalization may be buffered by ocean acidification, which reduces urchin grazing performance and the urchin barrens that tropical range-extending fishes prefer. Using ecosystems experiencing natural warming and acidification, we show that ocean acidification could buffer warming-facilitated[...]"
Source: Nature Climate Change
Authors: Ericka O. C. Coni et al.
Bacteriohopanepolyols signature in sediments of the East China Sea and its indications for hypoxia and organic matter sources
"The bacterial biomarker group of bacteriohopanepolyols (BHPs) has shown a significant potential to track terrestrial inputs and to respond to environmental changes. A total of 12 BHPs were detected in surface sediments of the East China Sea (ECS), with the contents of 3.79–361 μg/g TOC. The spatial distribution patterns and correlation analyses of bacteriohopanetetrol (BHT) and soil marker BHPs in sediments of the ECS indicate that they were mainly derived from marine autochthonous and terrestrial sources[...]"
Source: Science Direct
Authors: Meiling Yin et al.
Effect of dissolved oxygen and hydrogen on the stress corrosion cracking behavior of alloy 600 in high temperature water
"The stress corrosion cracking behavior of alloy 600 was studied in high temperature water at 288°C to 360°C. The effects of dissolved oxygen (DO) and dissolved hydrogen (DH) on crack growth rate (CGR) are discussed. Results show that the CGR of alloy 600 in hydrogenated water (at the Ni/NiO phase boundary) is about 2-200 times higher than in 2 ppm O2 oxygenated water at 325°C and 360°C, while the opposite behavior was observed at 288°C. Much more severe intergranular oxidation was observed[...]"
Source: Science Direct
Authors: Jiamei Wang et al.
Impact of the Agulhas Return Current on the oceanography of the Kerguelen Plateau region, Southern Ocean, over the last 40 kyrs
"The oceanography of the western Indian sector of the Southern Ocean is extremely complex due to the presence of several subantartic islands and plateaus that alter the zonal flow of the Antarctic Circumpolar Current. The circulation is even more complex around the Kerguelen Islands (KI) as the hydrological fronts merge with the Agulhas Return Current, the latter transporting warm surface waters from the low latitudes to the Subantarctic Zone (SAZ) east of KI. Here we present new sea-surface and sub-surface temperatures, based on diatom and radiolarian census[...]"
Source: Science Direct
Authors: M.Civel-Mazens et al.
Variable coastal hypoxia exposure and drivers across the southern California Current
"Declining oxygen is one of the most drastic changes in the ocean, and this trend is expected to worsen under future climate change scenarios. Spatial variability in dissolved oxygen dynamics and hypoxia exposures can drive differences in vulnerabilities of coastal ecosystems and resources, but documentation of variability at regional scales is rare in open-coast systems. Using a regional collaborative network of dissolved oxygen and temperature sensors maintained by scientists and fishing cooperatives from California, USA, and Baja California, Mexico, we characterize spatial and temporal variability in dissolved oxygen[...]"
Source: Nature Scientific Reports
Authors: Natalie H. N. Low et al.
Increase of a hypoxia-tolerant fish, Harpadon nehereus (Synodontidae), as a result of ocean deoxygenation off southwestern China
"We report a sudden explosive rise in abundance off southeastern China of a fish species that is hypoxia-tolerant, Bombay duck (Harpadon nehereus, Family Synodontidae), belonging to an Order (the Aulopiformes) encompassing overwhelmingly deep-sea fishes, but which predominantly occurs in coastal water. We suggest that this is made possible by the very high water content of its muscle and other tissues (about 90%, vs 75–80% for other coastal fish), which reduces its oxygen requirements and allows it to outcompete other fish in low-oxygen[...]"
Source: Environmental Biology of Fishes
Authors: Bin Kang et al.
Hydrostatic pressure is the universal key driver of microbial evolution in the deep ocean and beyond
"Oceans cover approximately 70% of the Earth’s surface, and microbes comprise 90% of the ocean biomass and are regarded as an important ‘hidden’ driver of essential elemental cycling, such as carbon cycling, in the oceans (Karl, 2007; Salazar and Sunagawa, 2017). Although the general public – even many scientists – think of the oceans as unified, stable water systems, they contain varied environments, including extreme environments such as oxygen-deficient zones, oligotrophic open ocean, polar water regions, deep ocean[...]"
Source: Environmental Microbiology Reports
Authors: Xiang Xiao et al.
Toward a better understanding of fish-based contribution to ocean carbon flux
"Fishes are the dominant vertebrates in the ocean, yet we know little of their contribution to carbon export flux at regional to global scales. We synthesize the existing information on fish-based carbon flux in coastal and pelagic waters, identify gaps and challenges in measuring this flux and approaches to address them, and recommend research priorities. Based on our synthesis of passive (fecal pellet sinking) and active.[...]".
Source: ASLO- Association for the Sciences of Limnology and Oceanography
Authors: Grace K. Saba et al.
Extreme Levels of Ocean Acidification Restructure the Plankton Community and Biogeochemistry of a Temperate Coastal Ecosystem: A Mesocosm Study
"The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms[...]".
Authors: Carsten Spisla et al.