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Cold-Water Coral Reefs in the Oxygen Minimum Zones Off West Africa

Abstract.

"The discoveries of large reefs within cold-water coral mound provinces revealed that the West African margin is a coral hotspot area in the Atlantic Ocean. The most striking observation is that cold-water corals thrive in extensive oxygen minimum zones under extreme conditions. This points to a wide tolerance of cold-water corals in these regions to low oxygen concentrations. The coral mound provinces off Mauritania, Angola, and Namibia, which are located in the centre of the local oxygen minimum zones, were selected as key study areas, and their regional oceanographic, bio-ecological, and geo-morphological settings are described in detail. [...]".

 

Source: Springer Nature
Authors: Claudia Wienberg et al.
DOI: https://doi.org/10.1007/978-3-031-40897-7_8

Read the full article here.


Bottom-water hypoxia in the Paracas Bay (Peru, 13.8°S) associated with seasonal and synoptic time scale variability of winds and water stratification

Abstract.

"Coastal hypoxia can occur naturally in inshore areas of the Eastern Boundary Upwelling Systems, influenced by the nutrient-rich and low-oxygen upwelling waters. This study aims to explore the influence of water stratification and winds on bottom-water hypoxia of the Paracas Bay, an area subjected to the most intense alongshore winds and active coastal upwelling in the Peruvian coast. Monitoring data of the Pisco-Paracas water properties [...]".

 

Source: Science Direct
Authors: Lander Merma-Mora et al.
DOI: https://doi.org/10.1016/j.jmarsys.2023.103918

Read the full article here.


Spatial and Temporal Redox Heterogeneity Controlled by a Fe(II), Anoxic Upwelling System in the Early Mesoproterozoic Ocean

Abstract. 

"The availability of oxygen and nutrients during the Mesoproterozoic (1.6–1.0 Ga) is thought to influence the rate of eukaryote evolution. The cause of the transition from low productivity in the upper Wumishan Formation to organic-rich sediments in the Hongshuizhuang Formation remains unknown. We report FeHR/FeT, Fepy/FeHR, MoEF, UEF, VEF, and [Ce/Ce*]SN in one core of the Yanliao Basin to study the redox evolution and compare it with other sections in different depths of the Yanliao Basin to get clues of the spatial and temporal redox heterogeneity. [...]".

 

Source: Wiley Online Library
Authors: Mingze Ye et al.
DOI: https://doi.org/10.1029/2023GL103598

Read the full article here.


Prokaryotic community dynamics and nitrogen-cycling genes in an oxygen-deficient upwelling system during La Niña and El Niño conditions

Abstract. 

"Dissolved oxygen regulates microbial distribution and nitrogen cycling and, therefore, ocean productivity and Earth's climate. To date, the assembly of microbial communities in relation to oceanographic changes due to El Niño Southern Oscillation (ENSO) remains poorly understood in oxygen minimum zones (OMZ). The Mexican Pacific upwelling system supports high productivity and a permanent OMZ. Here, the spatiotemporal distribution of the prokaryotic community and nitrogen-cycling genes was investigated along a repeated transect subjected to varying oceanographic conditions associated with La Niña in 2018 and El Niño in 2019. [...]".

 

Source: Wiley Online Library 
Authors: Silvia Pajares et al.
DOI: https://doi.org/10.1111/1462-2920.16362

Read the full article here.


Otoliths of marine fishes record evidence of low oxygen, temperature and pH conditions of deep Oxygen Minimum Zones

Abstract.

"The deep-sea is rapidly losing oxygen, with profound implications for marine organisms. Within Eastern Boundary Upwelling Systems, such as the California and the Benguela Current Ecosystems, an important question is how the ongoing expansion, intensification and shoaling of Oxygen Minimum Zones (OMZs) will affect deep-sea fishes throughout their lifetimes. One of the first steps to filling this knowledge gap is through the development of tools and techniques to track fishes’ exposure to hypoxic (<45 μmol kg-1), low-temperature (∼4–10°C) and low-pH (∼7.5) waters when inhabiting OMZs. [...]".

 

Source: Science Direct 
Authors: Leticia Maria Cavole et al.
DOI: https://doi.org/10.1016/j.dsr.2022.103941

Read the full article here.


Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events

Abstract.

"Ocean mesoscale eddies have been identified as drivers of localized extremely low dissolved oxygen concentration ([O2]) conditions in the subsurface. We employ a global physical-biogeochemical ocean model at eddy-permitting resolution to conduct a census of open-ocean eddies near Eastern Boundary Upwelling Systems adjacent to tropical Oxygen Minimum Zones (OMZs). We track cyclonic and anticyclonic eddies with a surface signature over the period 1992–2018 and isolate their subsurface oxygen characteristics. We identify strongly deoxygenating eddies and quantify their contribution to low [O2] extreme events. [...]".

 

Source: Geophysical Research Letters
Authors: Jamie Atkins et al.
DOI: https://doi.org/10.1029/2022GL098672

Read the full article here.


Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers

Abstract. 

"Understanding species’ responses to upwelling may be especially important in light of ongoing environmental change. Upwelling frequency and intensity are expected to increase in the future, while ocean acidification and deoxygenation are expected to decrease the pH and dissolved oxygen (DO) of upwelled waters. However, the acute effects of a single upwelling event and the integrated effects of multiple upwelling events on marine organisms are poorly understood. Here, we use in situ measurements of pH, temperature, and DO to characterize the covariance of environmental conditions within upwelling-dominated kelp forest ecosystems. We then test the effects of acute (0–3 days) and chronic (1–3 months) upwelling on the performance of two species of kelp forest grazers, the echinoderm, Mesocentrotus franciscanus, and the gastropod, Promartynia pulligo. We exposed organisms to static conditions in a regression design to determine the shape of the relationship between upwelling and performance and provide insights into the potential effects in a variable environment. We found that respiration, grazing, growth, and net calcification decline linearly with increasing upwelling intensity for Mfrancicanus over both acute and chronic timescales. [...]".

 

Source: Wiley Online Library

Authors: Emily M. Donham et al. 

DOI: https://doi.org/10.1111/gcb.16125

Read the full article here.


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.


Article Open Access Published: 29 November 2019 Role of synoptic activity on projected changes in upwelling-favourable winds at the ocean’s eastern bo

Abstract.

"The climate of the ocean’s eastern boundaries is strongly influenced by subtropical anticyclones, which drive a surface wind stress that promotes coastal upwelling of nutrient-rich subsurface water that supports high primary productivity and an abundance of food resources. Understanding the projected response of upwelling-favourable winds to climate change has broad implications for coastal biogeochemistry, ecology, and fisheries. [...]"

Source: npj Climate and Atmospheric Science
Authors: Catalina Aguirre et al.
DOI: 10.1038/s41612-019-0101-9

Read the full article here.


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!

Read the full article here.


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