Characterizing Reef Net Metabolism Via the Diel Co-Variation of pH and Dissolved Oxygen From High Resolution in Situ Sensors
Characterizing Reef Net Metabolism Via the Diel Co-Variation of pH and Dissolved Oxygen From High Resolution in Situ Sensors
Coral reefs are subject to degradation by multiple environmental stressors which are predicted to intensify. Stress can alter ecosystem composition, with shifts from hard coral to macroalgae dominated reefs often accompanied by an increase in soft corals and sponges. Such changes may alter net ecosystem metabolism and biogeochemistry by shifting the balance between photosynthesis, respiration, calcification and dissolution. We deployed high temporal resolution pH and dissolved oxygen (DO) sensors at four Caribbean reef sites with varying covers of hard and soft corals, sponges and macroalgae. The resultant data indicated that the strength of the “metabolic pulse”, specifically the co-variation in daily pH and DO oscillations, was driven by the net balance of light -dependent and -independent metabolism. pH and DO were positively correlated over the diel cycle at coral dominated sites, suggesting that photosynthesis and respiration were the major controlling processes, and further indicated by agreement with a simple production:respiration model. Whereas, at a site with high macroalgal cover, pH and DO decoupling was observed during daylight hours. This indicates that an unidentified light-driven process altered the expected pH:DO relationship. We hypothesize that this could be mediated by the higher levels of macroalgae, which either stimulated bacterial-mediated carbonate dissolution via the production and release of allelopathic compounds or retained oxygen, evolved during photosynthesis, in the gaseous form in seawater (ebullition). Our work demonstrates that high resolution monitoring of pH and DO provides insight into coral reef biogeochemical functioning and can be key for understanding long-term changes in coral reef metabolism.
Belize, Caribbean, coral reefs, dissolved oxygen, macroalgae, pH
Cryer, Sarah E.
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Evans, Claire
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Fowell, Sara E.
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Andrews, Gilbert
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Brown, Peter
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Carvalho, Filipa
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Degallerie, Diana
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Ludgate, Jake
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Rosado, Samir
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Sanders, Richard
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Strong, James A.
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Theophille, Derrick
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Young, Arlene
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Loucaides, Socratis
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10 September 2023
Cryer, Sarah E.
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Evans, Claire
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Fowell, Sara E.
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Andrews, Gilbert
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Brown, Peter
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Carvalho, Filipa
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Degallerie, Diana
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Ludgate, Jake
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Rosado, Samir
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Sanders, Richard
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Strong, James A.
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Theophille, Derrick
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Young, Arlene
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Loucaides, Socratis
5d0c31a4-269d-44a5-a858-13dc609ae072
Cryer, Sarah E., Evans, Claire, Fowell, Sara E., Andrews, Gilbert, Brown, Peter, Carvalho, Filipa, Degallerie, Diana, Ludgate, Jake, Rosado, Samir, Sanders, Richard, Strong, James A., Theophille, Derrick, Young, Arlene and Loucaides, Socratis
(2023)
Characterizing Reef Net Metabolism Via the Diel Co-Variation of pH and Dissolved Oxygen From High Resolution in Situ Sensors.
Global Biogeochemical Cycles, 37 (9), [e2022GB007577].
(doi:10.1029/2022GB007577).
Abstract
Coral reefs are subject to degradation by multiple environmental stressors which are predicted to intensify. Stress can alter ecosystem composition, with shifts from hard coral to macroalgae dominated reefs often accompanied by an increase in soft corals and sponges. Such changes may alter net ecosystem metabolism and biogeochemistry by shifting the balance between photosynthesis, respiration, calcification and dissolution. We deployed high temporal resolution pH and dissolved oxygen (DO) sensors at four Caribbean reef sites with varying covers of hard and soft corals, sponges and macroalgae. The resultant data indicated that the strength of the “metabolic pulse”, specifically the co-variation in daily pH and DO oscillations, was driven by the net balance of light -dependent and -independent metabolism. pH and DO were positively correlated over the diel cycle at coral dominated sites, suggesting that photosynthesis and respiration were the major controlling processes, and further indicated by agreement with a simple production:respiration model. Whereas, at a site with high macroalgal cover, pH and DO decoupling was observed during daylight hours. This indicates that an unidentified light-driven process altered the expected pH:DO relationship. We hypothesize that this could be mediated by the higher levels of macroalgae, which either stimulated bacterial-mediated carbonate dissolution via the production and release of allelopathic compounds or retained oxygen, evolved during photosynthesis, in the gaseous form in seawater (ebullition). Our work demonstrates that high resolution monitoring of pH and DO provides insight into coral reef biogeochemical functioning and can be key for understanding long-term changes in coral reef metabolism.
Text
Global Biogeochemical Cycles - 2023 - Cryer
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More information
Accepted/In Press date: 23 August 2023
e-pub ahead of print date: 29 August 2023
Published date: 10 September 2023
Additional Information:
Funding Information:
This work was supported by the United Kingdom Government through the Commonwealth Marine Economies Programme, which aims to enable safe and sustainable marine economies across Commonwealth Small Island Developing States. S.C. was supported by the NEXUSS Studentship Natural Environment Research Council (Grant NE/N012070/1) and NERC National Capability programme CLASS (Climate Linked Atlantic Sector Science), Grant NE/R015953/1. C.E. was supported by Natural Environment Research Council (NERC) Independent Research Fellowship NE/M018806/1. We would like to thank both our Belizean (Coastal Zone Management and Authority Belize and The Belize Port Authority) and Dominica Partners (Dominica Fisheries Division and Natura Island Dive) for their warm welcome and enthusiasm for the project. We would additionally like to thank Urska Martinicic (NOC) for deployment assistance, David Paxton (NOC) for design and manufacture of the platform, Anna Cryer for statistical advice, Duncan Stevens (UoS) for proof reading and Veerle Huvenne (NOC) for input on an early draft. Finally, we would like to thank our anonymous reviewers and the associated editor for constructive reviews, which greatly improved the manuscript.
Funding Information:
This work was supported by the United Kingdom Government through the Commonwealth Marine Economies Programme, which aims to enable safe and sustainable marine economies across Commonwealth Small Island Developing States. S.C. was supported by the NEXUSS Studentship Natural Environment Research Council (Grant NE/N012070/1) and NERC National Capability programme CLASS (Climate Linked Atlantic Sector Science), Grant NE/R015953/1. C.E. was supported by Natural Environment Research Council (NERC) Independent Research Fellowship NE/M018806/1. We would like to thank both our Belizean (Coastal Zone Management and Authority Belize and The Belize Port Authority) and Dominica Partners (Dominica Fisheries Division and Natura Island Dive) for their warm welcome and enthusiasm for the project. We would additionally like to thank Urska Martinicic (NOC) for deployment assistance, David Paxton (NOC) for design and manufacture of the platform, Anna Cryer for statistical advice, Duncan Stevens (UoS) for proof reading and Veerle Huvenne (NOC) for input on an early draft. Finally, we would like to thank our anonymous reviewers and the associated editor for constructive reviews, which greatly improved the manuscript.
Publisher Copyright:
© 2023. The Authors.
Keywords:
Belize, Caribbean, coral reefs, dissolved oxygen, macroalgae, pH
Identifiers
Local EPrints ID: 482071
URI: http://eprints.soton.ac.uk/id/eprint/482071
ISSN: 0886-6236
PURE UUID: e32e765f-7386-41ea-ad6e-a679c8b74f4a
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Date deposited: 18 Sep 2023 16:54
Last modified: 18 Mar 2024 03:49
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Contributors
Author:
Claire Evans
Author:
Sara E. Fowell
Author:
Gilbert Andrews
Author:
Peter Brown
Author:
Filipa Carvalho
Author:
Diana Degallerie
Author:
Jake Ludgate
Author:
Samir Rosado
Author:
Richard Sanders
Author:
James A. Strong
Author:
Derrick Theophille
Author:
Arlene Young
Author:
Socratis Loucaides
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