Coral Reef Functioning Along a Cross‐shelf Environmental Gradient: Abiotic and Biotic Drivers of Coral Reef Growth in the Red Sea

Handle URI:
http://hdl.handle.net/10754/612171
Title:
Coral Reef Functioning Along a Cross‐shelf Environmental Gradient: Abiotic and Biotic Drivers of Coral Reef Growth in the Red Sea
Authors:
Roik, Anna ( 0000-0002-8293-8339 )
Abstract:
Despite high temperature and salinity conditions that challenge reef growth in other oceans, the Red Sea maintains amongst the most biodiverse and productive coral reefs worldwide. It is therefore an important region for the exploration of coral reef functioning, and expected to contribute valuable insights towards the understanding of coral reefs in challenging environments. This dissertation assessed the baseline variability of in situ abiotic conditions (temperature, dissolved oxygen, pH, and total alkalinity, among others) in the central Red Sea and highlights these environmental regimes in a global context. Further, focus was directed on biotic factors (biofilm community dynamics, calcification and bioerosion), which underlie reef growth processes and are crucial for maintaining coral reef functioning and ecosystem services. Using full‐year data from an environmental cross‐shelf gradient, the dynamic interplay of abiotic and biotic factors was investigated. In situ observations demonstrate that central Red Sea coral reefs were highly variable on spatial, seasonal, and diel scales, and exhibited comparably high temperature, high salinity, and low dissolved oxygen levels, which on the one hand reflect future ocean predictions. Under these conditions epilithic bacterial and algal assemblages were mainly driven by variables (i.e., temperature, salinity, dissolved oxygen) which are predicted to change strongly in the progression of global climate change, implying an influential bottom up effect on reef‐building communities. On the other hand, measured alkalinity and other carbonate chemistry value were close to the estimates of preindustrial global ocean surface water and thus in favor of reef growth processes. Despite this beneficial carbonate chemistry, calcification and carbonate budgets in the reefs were not higher than in other coral reef regions. In this regard, seasonal calcification patterns suggest that summer temperatures may be exceeding the optima of calcifiers. As a possible interpretation of the here observed environmental regimes, it can be concluded that the central Red Sea may be less sensitive to ocean acidification, but is already impacted by ocean warming. Importantly, this dissertation provides valuable present‐day baseline data of the natural variability of relevant abiotic drivers together with benthic community and reef growth dynamics. These data will be important for future comparative studies and efforts to quantify the impact of future environmental change in the region.
Advisors:
Voolstra, Christian R. ( 0000-0003-4555-3795 )
Committee Member:
Jones, Burton ( 0000-0002-9599-1593 ) ; Ravasi, Timothy ( 0000-0002-9950-465X ) ; McCulloch, Malcolm
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Program:
Marine Science
Issue Date:
Jun-2016
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorVoolstra, Christian R.en
dc.contributor.authorRoik, Annaen
dc.date.accessioned2016-06-08T11:57:00Z-
dc.date.available2016-06-08T11:57:00Z-
dc.date.issued2016-06-
dc.identifier.urihttp://hdl.handle.net/10754/612171-
dc.description.abstractDespite high temperature and salinity conditions that challenge reef growth in other oceans, the Red Sea maintains amongst the most biodiverse and productive coral reefs worldwide. It is therefore an important region for the exploration of coral reef functioning, and expected to contribute valuable insights towards the understanding of coral reefs in challenging environments. This dissertation assessed the baseline variability of in situ abiotic conditions (temperature, dissolved oxygen, pH, and total alkalinity, among others) in the central Red Sea and highlights these environmental regimes in a global context. Further, focus was directed on biotic factors (biofilm community dynamics, calcification and bioerosion), which underlie reef growth processes and are crucial for maintaining coral reef functioning and ecosystem services. Using full‐year data from an environmental cross‐shelf gradient, the dynamic interplay of abiotic and biotic factors was investigated. In situ observations demonstrate that central Red Sea coral reefs were highly variable on spatial, seasonal, and diel scales, and exhibited comparably high temperature, high salinity, and low dissolved oxygen levels, which on the one hand reflect future ocean predictions. Under these conditions epilithic bacterial and algal assemblages were mainly driven by variables (i.e., temperature, salinity, dissolved oxygen) which are predicted to change strongly in the progression of global climate change, implying an influential bottom up effect on reef‐building communities. On the other hand, measured alkalinity and other carbonate chemistry value were close to the estimates of preindustrial global ocean surface water and thus in favor of reef growth processes. Despite this beneficial carbonate chemistry, calcification and carbonate budgets in the reefs were not higher than in other coral reef regions. In this regard, seasonal calcification patterns suggest that summer temperatures may be exceeding the optima of calcifiers. As a possible interpretation of the here observed environmental regimes, it can be concluded that the central Red Sea may be less sensitive to ocean acidification, but is already impacted by ocean warming. Importantly, this dissertation provides valuable present‐day baseline data of the natural variability of relevant abiotic drivers together with benthic community and reef growth dynamics. These data will be important for future comparative studies and efforts to quantify the impact of future environmental change in the region.en
dc.language.isoenen
dc.subjectRed Seaen
dc.subjectCalcificationen
dc.subjectCoral Reefen
dc.subjectCarbonate Budgeten
dc.subjectBacteriaen
dc.titleCoral Reef Functioning Along a Cross‐shelf Environmental Gradient: Abiotic and Biotic Drivers of Coral Reef Growth in the Red Seaen
dc.typeDissertationen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberJones, Burtonen
dc.contributor.committeememberRavasi, Timothyen
dc.contributor.committeememberMcCulloch, Malcolmen
thesis.degree.disciplineMarine Scienceen
thesis.degree.nameDoctor of Philosophyen
dc.person.id117235en
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