Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef

During the summer the Arabian Gulf is the world's warmest sea, also characterized by hypersalinity and extreme annual temperature fluctuations (12–35oC), making it marginal for coral growth. Yet extensive reefs occur in all eight nations bordering the Gulf. Here we present data demonstrating re...

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Autores principales:	Alain de Verneil, John A. Burt, Matthew Mitchell, Francesco Paparella
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	hypoxia oxygen gradients reef turbulence primary production benthic respiration Science Q General. Including nature conservation, geographical distribution QH1-199.5
Acceso en línea:	https://doaj.org/article/332ea50c88c243abb0c34d11effe9070
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spelling	oai:doaj.org-article:332ea50c88c243abb0c34d11effe90702021-11-30T13:56:42ZSummer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef2296-774510.3389/fmars.2021.781428https://doaj.org/article/332ea50c88c243abb0c34d11effe90702021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fmars.2021.781428/fullhttps://doaj.org/toc/2296-7745During the summer the Arabian Gulf is the world's warmest sea, also characterized by hypersalinity and extreme annual temperature fluctuations (12–35oC), making it marginal for coral growth. Yet extensive reefs occur in all eight nations bordering the Gulf. Here we present data demonstrating recurrent summer hypoxia events [oxygen concentration (O2) <2 mg l−1] at a reef in the southern Gulf. Currently these episodes are short enough (median 3 h, max 10 h) to preclude mass mortality. Will this always be the case? Predicting future Gulf hypoxia risk for coral reef ecosystems requires diagnosing the underlying causes driving the timing and magnitude of O2 swings. To this end, we compare our data with the output of a simple coupled 1-D water column/biogeochemical model of the reef environment. This allows us to give quantitative estimates of the O2 fluxes produced by photosynthesis both in the water column and within the coral framework, by respiration processes in the benthos, and from the atmosphere. We demonstrate the role of turbulent mixing, and in particular of tides, in shaping the temporal variability of the amplitude of the diel O2 cycle. We find that, in spite of significant turbulent mixing, which maintains the temperature vertically well-mixed, the biological O2 production and consumption is dominant over the atmospheric O2 flux, and is sufficient to generate vertical differences of 1 to 5 mg l−1 between the bottom and 1.5 m above it. While estimating future trends of hypoxia frequency will require further study, the present findings single out the relevant physical and biological processes (and their interplay) which deserve further scrutiny. The Gulf today experiences temperatures expected to occur across much of the tropics by the end of the century, and the observation of recurrent hypoxia events in the Gulf suggests that similar hypoxic phenomena may represent an important, but to date underappreciated, threat to the future of global coral reefs.Alain de VerneilJohn A. BurtJohn A. BurtMatthew MitchellFrancesco PaparellaFrancesco PaparellaFrontiers Media S.A.articlehypoxiaoxygen gradientsreef turbulenceprimary productionbenthic respirationScienceQGeneral. Including nature conservation, geographical distributionQH1-199.5ENFrontiers in Marine Science, Vol 8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	hypoxia oxygen gradients reef turbulence primary production benthic respiration Science Q General. Including nature conservation, geographical distribution QH1-199.5
spellingShingle	hypoxia oxygen gradients reef turbulence primary production benthic respiration Science Q General. Including nature conservation, geographical distribution QH1-199.5 Alain de Verneil John A. Burt John A. Burt Matthew Mitchell Francesco Paparella Francesco Paparella Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
description	During the summer the Arabian Gulf is the world's warmest sea, also characterized by hypersalinity and extreme annual temperature fluctuations (12–35oC), making it marginal for coral growth. Yet extensive reefs occur in all eight nations bordering the Gulf. Here we present data demonstrating recurrent summer hypoxia events [oxygen concentration (O2) <2 mg l−1] at a reef in the southern Gulf. Currently these episodes are short enough (median 3 h, max 10 h) to preclude mass mortality. Will this always be the case? Predicting future Gulf hypoxia risk for coral reef ecosystems requires diagnosing the underlying causes driving the timing and magnitude of O2 swings. To this end, we compare our data with the output of a simple coupled 1-D water column/biogeochemical model of the reef environment. This allows us to give quantitative estimates of the O2 fluxes produced by photosynthesis both in the water column and within the coral framework, by respiration processes in the benthos, and from the atmosphere. We demonstrate the role of turbulent mixing, and in particular of tides, in shaping the temporal variability of the amplitude of the diel O2 cycle. We find that, in spite of significant turbulent mixing, which maintains the temperature vertically well-mixed, the biological O2 production and consumption is dominant over the atmospheric O2 flux, and is sufficient to generate vertical differences of 1 to 5 mg l−1 between the bottom and 1.5 m above it. While estimating future trends of hypoxia frequency will require further study, the present findings single out the relevant physical and biological processes (and their interplay) which deserve further scrutiny. The Gulf today experiences temperatures expected to occur across much of the tropics by the end of the century, and the observation of recurrent hypoxia events in the Gulf suggests that similar hypoxic phenomena may represent an important, but to date underappreciated, threat to the future of global coral reefs.
format	article
author	Alain de Verneil John A. Burt John A. Burt Matthew Mitchell Francesco Paparella Francesco Paparella
author_facet	Alain de Verneil John A. Burt John A. Burt Matthew Mitchell Francesco Paparella Francesco Paparella
author_sort	Alain de Verneil
title	Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
title_short	Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
title_full	Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
title_fullStr	Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
title_full_unstemmed	Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef
title_sort	summer oxygen dynamics on a southern arabian gulf coral reef
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/332ea50c88c243abb0c34d11effe9070
work_keys_str_mv	AT alaindeverneil summeroxygendynamicsonasouthernarabiangulfcoralreef AT johnaburt summeroxygendynamicsonasouthernarabiangulfcoralreef AT johnaburt summeroxygendynamicsonasouthernarabiangulfcoralreef AT matthewmitchell summeroxygendynamicsonasouthernarabiangulfcoralreef AT francescopaparella summeroxygendynamicsonasouthernarabiangulfcoralreef AT francescopaparella summeroxygendynamicsonasouthernarabiangulfcoralreef
_version_	1718406496942817280

Summer Oxygen Dynamics on a Southern Arabian Gulf Coral Reef

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