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Divergent responses of the coral holobiont to deoxygenation and prior environmental stress

Abstract.

"Ocean deoxygenation is intensifying globally due to human activities – and is emerging as a grave threat to coral reef ecosystems where it can cause coral bleaching and mass mortality. However, deoxygenation is one of many threats to coral reefs, making it essential to understand how prior environmental stress may influence responses to deoxygenation. To address this question, we examined responses of the coral holobiont (i.e., the coral host, Symbiodiniaceae, and the microbiome) to deoxygenation in corals with different environmental stress backgrounds. [...]".

 

Source: Frontiers in Marine Science
Authors: Sara D. Swaminathan et al.
DOI: https://doi.org/10.3389/fmars.2023.1301474

Read the full article here.


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.


Increasing hypoxia on global coral reefs under ocean warming

Abstract. 

"Ocean deoxygenation is predicted to threaten marine ecosystems globally. However, current and future oxygen concentrations and the occurrence of hypoxic events on coral reefs remain underexplored. Here, using autonomous sensor data to explore oxygen variability and hypoxia exposure at 32 representative reef sites, we reveal that hypoxia is already pervasive on many reefs. Eighty-four percent of reefs experienced weak to moderate (≤153 µmol O2 kg−1to ≤92 µmol O2 kg−1) hypoxia and 13% experienced severe (≤61 µmol O2 kg−1) hypoxia. Under different climate change scenarios based on four Shared Socioeconomic Pathways (SSPs) [...]".

 

Source: Nature 
Authors: Ariel K. Pezner et al.
DOI: https://doi.org/10.1038/s41558-023-01619-2

Read the full article here.


Widespread oxyregulation in tropical corals under hypoxia

Abstract. 

"Hypoxia (low oxygen stress) is increasingly reported on coral reefs, caused by ocean deoxygenation linked to coastal nutrient pollution and ocean warming. While the ability to regulate respiration is a key driver of hypoxia tolerance in many other aquatic taxa, corals' oxyregulatory capabilities remain virtually unexplored. Here, we examine O2-consumption patterns across 17 coral species under declining O2partial pressure (pO2). All corals showed ability to oxyregulate, but total positive regulation (Tpos) varied between species, ranging from 0.41 (Pocillopora damicornis) to 2.42 (P. acuta). [...]".

 

Source: Science Direct 
Authors: David J. Hughes et al.
DOI: https://doi.org/10.1016/j.marpolbul.2022.113722

Read the full article here.


Global declines in coral reef calcium carbonate production under ocean acidification and warming

Abstract.

"Ocean warming and acidification threaten the future growth of coral reefs. This is because the calcifying coral reef taxa that construct the calcium carbonate frameworks and cement the reef together are highly sensitive to ocean warming and acidification. However, the global-scale effects of ocean warming and acidification on rates of coral reef net carbonate production remain poorly constrained despite a wealth of studies assessing their effects on the calcification of individual organisms[...]"

 

Source: PNAS- Proceedings of the National Academy of Sciences of the United States of America
Authors: Christopher E. Cornwall et al.
DOI: https://doi.org/10.1073/pnas.2015265118

Read the full article here.


Coral reef survival under accelerating ocean deoxygenation

Abstract.

"Global warming and local eutrophication simultaneously lower oxygen (O2) saturation and increase biological O2 demands to cause deoxygenation. Tropical shallow waters, and their coral reefs, are particularly vulnerable to extreme low O2 (hypoxia) events. These events can drive mass mortality of reef biota; however, they currently remain unaccounted for when considering coral reef persistence under local environmental alterations and global climatic change. In this Perspective, we integrate existing biological, ecological and geochemical[...]"

 

Source: Nature Climate Change
Authors: David J. Hughes et al.
DOI: https://doi.org/10.1038/s41558-020-0737-9

Read the full article here.


Ocean deoxygenation could be silently killing coral reefs, scientists say

"In March, Australia’s Great Barrier Reef suffered its most widespread bleaching event to date. Sixty percent of the reef underwent moderate to severe bleaching, and some corals may never recover.

The cause of this bleaching event was climate change, which brought unusually warm waters to the Great Barrier Reef in February, and disrupted the delicate, symbiotic relationship between the corals and their life-sustaining algae. In general, when sea temperatures rise, corals become stressed and expel algae from their tissues. Without this algae, the corals turn ghostly white and slowly starve. [...]"

Source: Mongabay

Read the full article here.


Coral reef survival under accelerating ocean deoxygenation

Abstract.

"Global warming and local eutrophication simultaneously lower oxygen (O2) saturation and increase biological O2 demands to cause deoxygenation. Tropical shallow waters, and their coral reefs, are particularly vulnerable to extreme low O2 (hypoxia) events. These events can drive mass mortality of reef biota; however, they currently remain unaccounted for when considering coral reef persistence under local environmental alterations and global climatic change. [...]"

Source: Nature Climate Change
Authors: David J. Hughes et al.
DOI: 10.1038/s41558-020-0737-9

Read the full article here.


Denitrification Aligns with N2 Fixation in Red Sea Corals

Abstract.

"Denitrification may potentially alleviate excess nitrogen (N) availability in coral holobionts to maintain a favourable N to phosphorous ratio in the coral tissue. However, little is known about the abundance and activity of denitrifiers in the coral holobiont. The present study used the nirS marker gene as a proxy for denitrification potential along with measurements of denitrification rates in a comparative coral taxonomic framework from the Red Sea: Acropora hemprichiiMillepora dichotoma, and Pleuractis granulosa. [...]"

Source: Scientific Reports
Authors: Arjen Tilstra et al.
DOI: 10.1038/s41598-019-55408-z

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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