News

Latitudinal gradient in the respiration quotient and the implications for ocean oxygen availability

Abstract.

"Climate-driven depletion of ocean oxygen strongly impacts the global cycles of carbon and nutrients as well as the survival of many animal species. One of the main uncertainties in predicting changes to marine oxygen levels is the regulation of the biological respiration demand associated with the biological pump. Derived from the Redfield ratio, the molar ratio of oxygen to organic carbon consumed during respiration (i.e., the respiration quotient, r −O2:C  r−O2:C ) is consistently assumed constant but rarely, if ever, measured. Using a prognostic[...]"

 

Source: Proceedings of the National Academy of Sciences of the United States of America
Authors: Allison R. Moreno et al.
DOI:  https://doi.org/10.1073/pnas.2004986117

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Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming

Abstract.

"It is well established that the ocean is currently losing dissolved oxygen (O2) in response to ocean warming, but the long‐term, equilibrium response of O2 to a warmer climate is neither well quantified nor understood. Here we use idealized multimillennial global warming simulations with a comprehensive Earth system model to show that the equilibrium response in ocean O2 differs fundamentally from the ongoing transient response. After physical equilibration of the model (>4,000 years) under a two times preindustrial CO2 scenario, the deep ocean[...]"

Source: Advancing Earth and Space Science
Authors: T. L. Frölicher et al.
DOI: https://doi.org/10.1029/2020GB006601

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Mangrove-Derived Organic and Inorganic Carbon Exchanges Between the Sinnamary Estuarine System

Abstract.

"There is growing evidence that a substantial fraction of the dissolved organic and inorganic carbon (DOC and DIC) and particulate organic carbon (POC) can be exported from mangroves to the ocean. Yet our understanding of C fluxes in mangrove forests is limited to only few regional studies that exclude the world's longest sediment dispersal system connected to the Amazon River. The present study aims at (1) examining tidal fluctuations of DOC, POC, and DIC; their isotopes; and optical properties such as chromophoric dissolved organic matter[...]"


Source: Advancing Earth And Space Science
Authors: Raghab Ray et al.
DOI: https://doi.org/10.1029/2020JG005739

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Ocean acidification reduces growth and grazing impact of Antarctic heterotrophic nanoflagellates

Abstract.

"High-latitude oceans have been identified as particularly vulnerable to ocean acidification if anthropogenic CO2 emissions continue. Marine microbes are an essential part of the marine food web and are a critical link in biogeochemical processes in the ocean, such as the cycling of nutrients and carbon. Despite this, the response of Antarctic marine microbial communities to ocean acidification is poorly understood. We investigated the effect of increasing fCO2 on the growth of heterotrophic nanoflagellates (HNFs), nano- and picophytoplankton, and prokaryotes (heterotrophic Bacteria and Archaea) in a natural coastal Antarctic marine microbial community from Prydz Bay, East Antarctica.[...]"

 

Source: Biogeosciences
Authors: Stacy Deppeler et al.
DOI: 10.5194/bg-17-4153-2020

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Can ocean community production and respiration be determined by measuring high-frequency oxygen profiles from autonomous floats?

Abstract.

"Oceanic primary production forms the basis of the marine food web and provides a pathway for carbon sequestration. Despite its importance, spatial and temporal variations of primary production are poorly observed, in large part because the traditional measurement techniques are laborious and require the presence of a ship. More efficient methods are emerging that take advantage of miniaturized sensors integrated into autonomous platforms such as gliders and profiling floats. One such method relies on determining the diurnal cycle of dissolved oxygen in the mixed layer and has been applied successfully to measurements from gliders and mixed-layer floats. [...]”

 

Source: Biogeosciences
Authors: Christopher Gordon et al.
DOI: 10.5194/bg-17-41110.5194

 

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Imprint of Trace Dissolved Oxygen on Prokaryoplankton Community Structure in an Oxygen Minimum Zone

Abstract.

"The Eastern Tropical North Pacific (ETNP) is a large, persistent, and intensifying oxygen minimum zone (OMZ) that accounts for almost half of the total area of global OMZs. Within the OMZ core (∼350–700 m depth), dissolved oxygen is typically near or below the analytical detection limit of modern sensors (∼10 nM). Steep oxygen gradients above and below the OMZ core lead to vertical structuring of microbial communities that also vary between particle-associated (PA) and free-living (FL) size fractions [...]"

Source: Frontiers in Marine Science
Authors: Luis Medina Faull et al.
DOI: 10.3389/fmars.2020.00360

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NOAA, partners to report on 2020 Gulf of Mexico ‘dead zone’ monitoring cruise

NOAA and its partners will report on their recent research cruise to measure the extent of the hypoxic or “dead zone” in the Gulf of Mexico during a media teleconference on Tue., Aug. 4 at 11:00 a.m. EDT.

In June, NOAA scientists forecasted this summer’s dead zone – an area of low to no oxygen that can kill fish and other marine life – to be approximately 6,700 square miles. That is larger than the long-term average measured size of 5,387 square miles, but substantially less than the record of 8,776 square miles set in 2017.

 

Visit the announcement here.