Metabolic prioritization of fish in hypoxic waters: an integrative modeling approach
"Marine hypoxia has had major consequences for both economically and ecologically critical fish species around the world. As hypoxic regions continue to grow in severity and extent, we must deepen our understanding of mechanisms driving population and community responses to major stressors. It has been shown that food availability and habitat use are the most critical components of impacts on individual fish leading to observed outcomes at higher levels of organization. However, differences within and among species in partitioning available energy for metabolic demands – or metabolic prioritization – in response to stressors are often ignored. [...]".
Source: Frontiers in Marine Science
Authors: Elizabeth Duskey
Partitioning of the denitrification pathway and other nitrite metabolisms within global oxygen deficient zones
"Oxygen deficient zones (ODZs) account for about 30% of total oceanic fixed nitrogen loss via processes including denitrification, a microbially mediated pathway proceeding stepwise from NO3– to N2. This process may be performed entirely by complete denitrifiers capable of all four enzymatic steps, but many organisms possess only partial denitrification pathways, either producing or consuming key intermediates such as the greenhouse gas N2O. Metagenomics and marker gene surveys have revealed a diversity of denitrification genes within ODZs, but whether these genes co-occur within [...]".
Authors: Irene H. Zhang et al.
Microscale dynamics promote segregated denitrification in diatom aggregates sinking slowly in bulk oxygenated seawater
"Sinking marine particles drive the biological pump that naturally sequesters carbon from the atmosphere. Despite their small size, the compartmentalized nature of particles promotes intense localized metabolic activity by their bacterial colonizers. Yet the mechanisms promoting the onset of denitrification, a metabolism that arises once oxygen is limiting, remain to be established. Here we show experimentally that slow sinking aggregates composed of marine diatoms—important primary producers for global carbon export—support active denitrification even among bulk oxygenated water typically thought to exclude anaerobic metabolisms. [...]".
Authors: Davide Ciccarese et al.
Sulfate triple-oxygen-isotope evidence confirming oceanic oxygenation 570 million years ago
"The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we show that carbonate-associated sulfate (CAS) from three different paleocontinents all have conspicuous negative 17O anomalies (Δ′17OCAS values down to −0.53‰) during the SE. [...]".
Authors: Haiyang Wang et al.
Deoxygenation of the Baltic Sea during the last millennium
"Over the last 1,000 years, changing climate strongly influenced the ecosystem of coastal oceans such as the Baltic Sea. Sedimentary records revealed that changing temperatures could be linked to changing oxygen levels, spreading anoxic, oxygen-free areas in the Baltic Sea. However, the attribution of changing oxygen levels remains to be challenging. This work simulates a preindustrial period of 850 years, covering the Medieval Climate Anomaly (MCA) and the Little Ice Age using a coupled physical-biogeochemical model. [...]".
Source: Frontiers in Marine Science
Authors: Florian Börgel et al.
Natural hypoxic conditions do not affect the respiration rates of the cold-water coral Desmophyllum pertusum (Lophelia pertusa) ...
Full title: "Natural hypoxic conditions do not affect the respiration rates of the cold-water coral Desmophyllum pertusum (Lophelia pertusa) living in the Angola margin (Southeastern Atlantic Ocean)"
"Large, well-developed and flourishing reefs dominated by the cold-water coral Desmophyllum pertusum have recently been discovered along the Angola margin in the southeastern Atlantic Ocean living under very low oxygen concentrations (0.6–1.5 mL L−1). This study assessed the respiration rates of this coral in a short-term (10 days) aquarium experiment under naturally [...]".
Source: Science Direct
Authors: Andrea Gori et al.
Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition ...
Full title: "Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition: New insights from a palaeoceanographic empirical approach"
"Modern marine settings are experiencing rapid deoxygenation mainly forced by global warming and anthropogenic eutrophication. Therefore, studies that assess the role of climate variability in large spatiotemporal deoxygenations during past climate changes are needed to better comprehend the consequences of the current global warming and ocean deoxygenation. [...]".
Source: Science Direct
Authors: Ricardo D. Monedero-Contreras et al.
Hypoxia and warming take sides with small marine protists: An integrated laboratory and field study
"Hypoxia and ocean warming are two mounting global environmental threats influencing marine ecosystems. However, the interactive effects of rising temperature and depleted dissolved oxygen (DO) on marine protists remains unknown. Here, we conducted a series of laboratory experiments on four protozoa with distinct cell sizes to investigate the combined effects of temperature (19, 22, 25, 28, and 31 °C) and oxygen availability (hypoxia, 2 mg DO L−1 and normoxia, 7 mg DO L−1) on their physiological performances (i.e., growth, ingestion, and respiration rates). The hypoxia-induced inhibition in three physiological rates increased with the biovolume of the protists. [...]".
Source: Science Direct
Authors: Cheng Qian et al.
Oxygen dynamics in marine productive ecosystems at ecologically relevant scales
"The decline of dissolved oxygen in the oceans could be detrimental to marine life and biogeochemical cycles. However, predicting future oxygen availability with models that mainly focus on temporal and spatial large-scale mean values could lead to incorrect predictions. Marine ecosystems are strongly influenced by short temporal- and small spatial-scale oxygen fluctuations. Large-scale modelling neglects fluctuations, which include the pervasive occurrence of high oxygen supersaturation on a daily time scale in productive ecosystems such as coral reefs, seagrass meadows and mangrove forests and the spatial heterogeneity in oxygen availability at microclimatic scales. [...]".
Authors: Folco Giomi et al.
Can Oxygen Utilization Rate Be Used to Track the Long-Term Changes of Aerobic Respiration in the Mesopelagic Atlantic Ocean?
"Quantifying changes in oceanic aerobic respiration is essential for understanding marine deoxygenation. Here we use an Earth system model to investigate if and to what extent oxygen utilization rate (OUR) can be used to track the temporal change of true respiration (Rtrue). Rtrue results from the degradation of particulate and dissolved organic matter in the model ocean, acting as ground truth to evaluate the accuracy of OUR. Results show that in thermocline and intermediate waters of the North Atlantic Subtropical Gyre (200–1,000 m), vertically integrated OUR and Rtrue both decrease by 0.2 molO2/m2/yr from 1850 to 2100 under global warming. [...]".
Source: Wiley Online Library
Authors: Haichao Guo et al.
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