News

Extinction of cold-water corals on the Namibian shelf due to low oxygen contents

"They were also able to link this event with a shift in the Benguela upwelling system, and an associated intensification of the oxygen minimum zone in this region. The team has now published their findings in the journal Geology.

Known as 'ecosystem engineers', cold-water corals play an important role in the species diversity of the deep sea. The coral species Lophelia pertusa is significantly involved in reef formation. [...]"

Source: EurekAlert!

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The Dynamics and Impact of Ocean Acidification and Hypoxia:

Insights from Sustained Investigations in the Northern California Current Large Marine Ecosystem

Abstract.

"Coastal upwelling ecosystems around the world are defined by wind-generated currents that bring deep, nutrient-rich waters to the surface ocean where they fuel exceptionally productive food webs. These ecosystems are also now understood to share a common vulnerability to ocean acidification and hypoxia (OAH). In the California Current Large Marine Ecosystem (CCLME), reports of marine life die-offs by fishers and resource managers triggered research that led to an understanding of the risks posed by hypoxia. Similarly, unprecedented losses from shellfish hatcheries led to novel insights into the coastal expression of ocean acidification. [...]"

Source: Oceanography
Authors: Francis Chan et al.
DOI: 10.5670/oceanog.2019.312

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Effects of upwelling duration and phytoplankton growth regime on dissolved oxygen levels in an idealized Iberian Peninsula upwelling system

Abstract.

"We apply a coupled modelling system composed of a state-of-the-art hydrodynamical model and a low complexity biogeochemical model to an idealized Iberian Peninsula upwelling system to identify the main drivers of dissolved oxygen variability and to study its response to changes in the duration of the upwelling season and in phytoplankton growth regime. [...]"

Source: Nonlinear Processes in Geophysics (preprint)
Authors: João H. Bettencourt et al.
DOI: 10.5194/npg-2019-47

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Fish debris in sediments from the last 25 kyr in the Humboldt Current reveal the role of productivity and oxygen on small pelagic fishes

Abstract.

"Upwelling of cold, nutrient-rich water from the oxygen minimum zone (OMZ) off Peru sustains the world’s highest production of forage fish, mostly composed of anchovy (Engraulis ringens). However, the potential impacts of climate change on upwelling dynamics and thus fish productivity in the near future are uncertain. Here, we reconstruct past changes in fish populations during the last 25,000 years to unravel their response to changes in OMZ intensity and productivity. [...]"

Source: Progress in Oceanography
Authors: RenatoSalvatteci et al.
DOI: 10.1016/j.pocean.2019.05.006

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Antarctic offshore polynyas linked to Southern Hemisphere climate anomalies

Abstract.

"Offshore Antarctic polynyas—large openings in the winter sea ice cover—are thought to be maintained by a rapid ventilation of deep-ocean heat through convective mixing. These rare phenomena may alter abyssal properties and circulation, yet their formation mechanisms are not well understood. Here we demonstrate that concurrent upper-ocean preconditioning and meteorological perturbations are responsible for the appearance of polynyas in the Weddell Sea region of the Southern Ocean. [...]"

Source: Nature
Authors: Ethan C. Campbell et al.
DOI: 10.1038/s41586-019-1294-0

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Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Abstract.

"The coastal upwelling regime off Peru in December 2012 showed considerable vertical concentration gradients of dissolved nitrous oxide (N2O) across the top few meters of the ocean. The gradients were predominantly downward, i.e., concentrations decreased toward the surface. Ignoring these gradients causes a systematic error in regionally integrated gas exchange estimates, when using observed concentrations at several meters below the surface as input for bulk flux parameterizations – as is routinely practiced. [...]"

Source: Biogeosciences
Authors: Tim Fischer et al.
DOI: 10.5194/bg-16-2307-2019

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Diapycnal dissolved organic matter supply into the upper Peruvian oxycline

Abstract.

"The eastern tropical South Pacific (ETSP) hosts the Peruvian upwelling system, which represents one of the most productive areas in the world ocean. High primary production followed by rapid heterotrophic utilization of organic matter supports the formation of one of the most intense oxygen minimum zones (OMZs) in the world ocean, where dissolved oxygen (O2) concentrations reach less than 1 µmol kg−1. [...]"

Source: Biogeosciences
Authors: Alexandra N. Loginova et al.
DOI: 10.5194/bg-16-2033-2019

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Remote and local drivers of oxygen and nitrate variability in the shallow oxygen minimum zone off Mauritania in June 2014

Abstract.

"Upwelling systems play a key role in the global carbon and nitrogen cycles and are also of local relevance due to their high productivity and fish resources. To capture and understand the high spatial and temporal variability in physical and biogeochemical parameters found in these regions, novel measurement techniques have to be combined in an interdisciplinary manner. Here we use high-resolution glider-based physical–biogeochemical observations in combination with ship-based underwater vision profiler, sensor and bottle data to investigate the drivers of oxygen and nitrate variability across the shelf break off Mauritania in June 2014. [...]"

Source: Biogeosciences
Authors: Soeren Thomsen et al.
DOI: 10.5194/bg-16-979-2019

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N2O Emissions From the Northern Benguela Upwelling System

Abstract.

"The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well‐developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N2O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near‐surface waters emit N2O to the atmosphere in the BUS is highly uncertain. [...]"

Source: Geophysical Research Letters
Authors: D. L. Arévalo‐Martínez et al.
DOI: 10.1029/2018GL081648

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Seasonal Variability of the Mauritania Current and Hydrography at 18°N

Abstract.

"Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. [...]"

Source: JGR Oceans
Authors: T. Klenz, M. Dengler and P. Brandt
DOI: 10.1029/2018JC014264

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