News

Variable Oxygen Levels Lead to Variable Stoichiometry of Benthic Nutrient Fluxes in a Hypertrophic Estuary

Abstract.

"Harmful blooms of cyanobacteria may extend over long time spans due to self-sustaining mechanisms. We hypothesized that settled blooms may increase redox-dependent P release and unbalance the stoichiometry of benthic nutrient regeneration (NH4+:SiO2:PO43− ratios). We tested this hypothesis in the hypertrophic Curonian Lagoon, the largest in Europe. During summer, at peak chlorophyll and water temperatures, sediment cores were collected over 19 stations representing all the lagoon sedimentary environments. Sediment organic content, granulometry, aerobic respiration, and oxic[...]"

 

Source: Estuaries and Coasts
Authors: Marco Bartoli et al.
DOI: https://doi.org/10.1007/s12237-020-00786-1

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Enhanced Organic Carbon Burial in Sediments of Oxygen Minimum Zones Upon Ocean Deoxygenation

Abstract.

"Oxygen minimum zones (OMZs) in the ocean are expanding. This expansion is attributed to global warming and may continue over the next 10 to 100 kyrs due to multiple climate CO2-driven factors. The expansion of oxygen-deficient waters has the potential to enhance organic carbon burial in marine sediments, thereby providing a negative feedback on global warming. Here, we study the response of dissolved oxygen in the ocean to increased phosphorus and iron inputs due to CO2-driven enhanced weathering and increased dust emissions, respectively. We use an ocean biogeochemical model[...]"

Source: frontiers in the Marine Science
Authors: Itzel Ruvalcaba Baroni et al.
DOI: https://doi.org/10.3389/fmars.2019.00839

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Can microplastics pose a threat to ocean carbon sequestration?

Abstract.

"Global climate change has attracted worldwide attention. The ocean is the largest active carbon pool on the planet and plays an important role in global climate change. However, marine plastic pollution is getting increasingly serious due to the large consumption and mismanagement of global plastics. The impact of marine plastics on ecosystem responsible for the gas exchange and circulation of marine CO2 may cause more greenhouse gas emissions. Consequently, in this paper, threats of marine microplastics to ocean carbon sequestration are discussed. Marine microplastics[...]"

 

Source: Science Direct
Authors: Maocai Shen et al.
DOI: https://doi.org/10.1016/j.marpolbul.2019.110712

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Observing the Global Ocean with Biogeochemical-Argo

Abstract.

"Biogeochemical-Argo (BGC-Argo) is a network of profiling floats carrying sensors that enable observation of as many as six essential biogeochemical and bio-optical variables: oxygen, nitrate, pH, chlorophyll a, suspended particles, and downwelling irradiance. This sensor network represents today's most promising strategy for collecting temporally and vertically resolved observations of biogeochemical properties throughout the ocean. All data are freely available within 24 hours of transmission. These data fill large gaps in ocean-observing systems and support three ambitions: gaining a better understanding of biogeochemical processes (e.g., the biological[...]"

 

Source: Annual Review of Marine Science
Authors: Hervé Claustre et al.
DOI: https://doi.org/10.1146/annurev-marine-010419-010956

Read the full article here.

 

 


The regulation of oxygen to low concentrations in marineoxygen-minimum zones

Abstract.

"The Bay of Bengal hosts persistent, measurable, but sub-micromolar, concentrations of oxygenin its oxygen-minimum zone (OMZ). Such low-oxygen conditions are not necessarily rare in theglobal ocean and seem also to characterize the OMZ of the Pescadero Basin in the Gulf of California,as well as the outer edges of otherwise anoxic OMZs, such as can be found, for example, in theEastern Tropical North Pacific. We show here that biological controls on oxygen consumption arerequired to allow the semistable persistence of low-oxygen conditions in OMZ settings; otherwise,only small changes in physical mixing or rates of primary production would drive the OMZ betweenanoxic and oxic states with potentially large swings in oxygen concentration. [...]"

Source: Journal of Marine Research
Authors: Donald E. Canfield et al.
 

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Variability of dissolved oxygen in the Arabian Sea Oxygen Minimum Zone and its driving mechanisms

Abstract.

"The Arabian Sea hosts one of the most intense, perennial Oxygen Minimum Zones (OMZ) in the world ocean. Observations along a meridional transect at 68°E extending from 8 to 21°N showed large seasonal as well as interannual changes in the dissolved oxygen and nitrite concentrations. Unlike previous studies that used observations from the periphery of the OMZ, our observations are from its core and also allow us demarcating the southern extent of the OMZ. [...]"

Source: Journal of Marine Systems
Authors: Damodar M.Shenoy et al.
DOI: 10.1016/j.jmarsys.2020.103310 

Read the full article here.


When microbiologists plunge into the ocean

Microbiologists stake their claim: assessing climate change involves new ways of studying the ocean’s microbes.

"Microbiology wants in. No longer should microbes and microbial processes be left out of climate change assessments, state 33 researchers from nine countries in their consensus statement1, “Scientists’ warning to humanity: microorganisms and climate change.” There’s a “need to act,” the authors write. By underappreciating the importance of microbial processes both on land and in the oceans, “we fundamentally limit our understanding of Earth’s biosphere and response to climate change and thus jeopardize efforts to create an environmentally sustainable future.” [...]"

Source: Nature Methods 
Authors: Vivien Marx
DOI: 10.1038/s41592-020-0736-9

Read the full article here.


The regulation of oxygen to low concentrations in marine oxygen-minimum zones

Abstract.

"The Bay of Bengal hosts persistent, measurable, but sub-micromolar, concentrations of oxygen in its oxygen-minimum zone (OMZ). Such low-oxygen conditions are not necessarily rare in the global ocean and seem also to characterize the OMZ of the Pescadero Basin in the Gulf of California, as well as the outer edges of otherwise anoxic OMZs, such as can be found, for example, in the Eastern Tropical North Pacific. We show here that biological controls on oxygen consumption are required to allow the semistable persistence of low-oxygen conditions in OMZ settings; otherwise, only small changes in physical mixing or rates of primary production would drive the OMZ between anoxic and oxic states with potentially large swings in oxygen concentration. [...]"

Source: Journal of Marine Research 
Authors: Don E. Canfield et al.

Read the full article here.


No detectable Weddell Sea Antarctic Bottom Water export during the Last and Penultimate Glacial Maximum

Abstract.

"Weddell Sea-derived Antarctic Bottom Water (AABW) is one of the most important deep water masses in the Southern Hemisphere occupying large portions of the deep Southern Ocean (SO) today. While substantial changes in SO-overturning circulation were previously suggested, the state of Weddell Sea AABW export during glacial climates remains poorly understood. [...]"

Source: Nature Communications
Authors: Huang Huang et al.
DOI: 10.1038/s41467-020-14302-3

Read the full article here.


Physical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling system

Abstract.

"The northern Humboldt current system (NHCS or Peru upwelling system) sustains the world's largest small pelagic fishery. While a nearshore surface cooling has been observed off southern Peru in recent decades, there is still considerable debate on the impact of climate change on the regional ecosystem. This calls for more accurate regional climate projections of the 21st century, using adapted tools such as regional eddy-resolving coupled biophysical models. [...]"

Source: Biogeosciences (preprint)
Authors: Vincent Echevin et al.
DOI: 10.5194/bg-2020-4

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Anaerobic Activity Is a Big Contributor in Marine “Dead Zones”

Climate models that do not account for anaerobic microbial activity may underestimate future expansion of oxygen-depleted waters.

"Certain parts of Earth’s oceans are so oxygen depleted that they can hardly sustain life. Climate models predict that these “dead zones” will expand as global warming progresses, affecting ecosystems, fisheries, and the climate itself. Now Lengger et al. provide new evidence that such predictions do not adequately account for the activity of anaerobic microbes that consume inorganic carbon within dead zones. [...]"

Source: EOS.org

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Modulation of the North Atlantic deoxygenation by the slowdown of the nutrient stream

Abstract.

"Western boundary currents act as transport pathways for nutrient-rich waters from low to high latitudes (nutrient streams) and are responsible for maintaining midlatitude and high-latitude productivity in the North Atlantic and North Pacific. This study investigates the centennial oxygen (O2) and nutrient changes over the Northern Hemisphere in the context of the projected warming and general weakening of the Atlantic Meridional Overturning Circulation (AMOC) in a subset of Earth system models included in the CMIP5 catalogue. In all models examined, the Atlantic warms faster than the Pacific Ocean, resulting in a greater basin-scale solubility decrease. [...]"

Source: Biogeosciences
Authors: Filippos Tagklis et al.
DOI: 10.5194/bg-17-231-2020

Read the full article here.


Record-Setting Ocean Warmth Continued in 2019

"Human-emitted greenhouse gases (GHGs) have resulted in a long-term and unequivocal warming of the planet (IPCC, 2019). More than 90% of the excess heat is stored within the world’s oceans, where it accumulates and causes increases in ocean temperature (Rhein et al., 2013; Abram et al., 2019). Because the oceans are the main repository of the Earth’s energy imbalance, measuring ocean heat content (OHC) is one of the best way to quantify the rate of global warming (Trenberth et al., 2016; Von Schuckmann et al., 2016; Cheng et al., 2018). [...]"

Source: Advances in Atmospheric Sciences
Authors: Lijing Cheng et al.
DOI: 10.1007/s00376-020-9283-7

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Record-setting ocean warmth continued in 2019

"A new analysis shows the world's oceans were the warmest in 2019 than any other time in recorded human history, especially between the surface and a depth of 2,000 meters. The study, conducted by an international team of 14 scientists from 11 institutes across the world, also concludes that the past ten years have been the warmest on record for global ocean temperatures, with the past five years holding the highest record. [...]"

Source: EurekAlert!

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Implications of different nitrogen input sources for potential production and carbon flux estimates in the coastal Gulf of Mexico (GOM)

and Korean Peninsula coastal waters

Abstract.

"The coastal Gulf of Mexico (GOM) and coastal sea off the Korean Peninsula (CSK) both suffer from human-induced eutrophication. We used a nitrogen (N) mass balance model in two different regions with different nitrogen input sources to estimate organic carbon fluxes and predict future carbon fluxes under different model scenarios. The coastal GOM receives nitrogen predominantly from the Mississippi and Atchafalaya rivers and atmospheric nitrogen deposition is only a minor component in this region. [...]"

Source: Ocean Science
Authors: Jongsun Kim et al.
DOI: 10.5194/os-16-45-2020

Read the full article here.


Fish Diet Shifts Associated with the Northern Gulf of Mexico Hypoxic Zone

Abstract.

"The occurrence of low dissolved oxygen (hypoxia) in coastal waters may alter trophic interactions within the water column. This study identified a threshold at which hypoxia in the northern Gulf of Mexico (NGOMEX) alters composition of fish catch and diet composition (stomach contents) of fishes using fish trawl data from summers 2006–2008. Hypoxia in the NGOMEX impacted fish catch per unit effort (CPUE) and diet below dissolved oxygen thresholds of 1.15 mg L−1 (for fish CPUE) and 1.71 mg L−1 (for diet). CPUE of many fish species was lower at hypoxic sites (≤ 1.15 mg L −1) as compared to normoxic regions (> 1.15 mg L −1), including the key recreational or commercial fish species Atlantic croaker Micropogonias undulatus and red snapper Lutjanus campechanus. [...]"

Source: Estuaries and Coasts
Authors: Cassandra N. Glaspie et al.
DOI: 10.1007/s12237-019-00626-x

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Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays

Abstract.

"Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems.  [...]"

Source:  Annual Review of Marine Science
Authors: John L. Largier
DOI: 10.1146/annurev-marine-010419-011020

Read the full article here.


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

Read the full article here.


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

Read the full article here.


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

Read the full article here.


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