Osmoadjustment in the Coral Holobiont

Handle URI:
http://hdl.handle.net/10754/623283
Title:
Osmoadjustment in the Coral Holobiont
Authors:
Röthig, Till ( 0000-0001-6359-8589 )
Abstract:
Coral reefs are under considerable decline. The framework builders in coral reefs are scleractinian corals, which comprise so-called holobionts, consisting of cnidarian host, algal symbionts (genus Symbiodinium), and other associated microbes. Corals are commonly considered stenohaline osmoconformers, possessing limited capability to adjust to salinity changes. However, corals differ in their ability to cope with different salinities. The underlying mechanisms have not yet been addressed. To further understand putative mechanisms involved, I examined coral holobiont osmoregulation conducting a range of experiments on the coral Fungia granulosa. In my research F. granulosa from the Red Sea exhibited pronounced physiological reactions (decreased photosynthesis, cessation of calcification) upon short-term incubations (4 h) to high salinity (55). However, during a 29-day in situ salinity transect experiment, coral holobiont photosynthesis was unimpaired under high salinity (49) indicating acclimatization. F. granulosa microbiome changes after the 29-day high salinity exposure aligned with a bacterial community restructuring that putatively supports the coral salinity acclimatization (osmolyte synthesis, nutrient fixation/cycling). Long-term incubations (7 d) of cultured Symbiodinium exhibited cell growth even at ‘extreme’ salinity levels of 25 and 55. Metabolic profiles of four Symbiodinium strains exposed to increased (55) and decreased (25) salinities for 4 h indicated distinct carbohydrates and amino acids to be putatively involved in the osmoadjustment. Importantly, under high salinity the osmolyte floridoside was consistently increased. This could be corroborated in the coral model Aiptasia and in corals from the Persian/Arabian Gulf, where floridoside was also markedly increased upon short- (15 h) and long-term (>24 months) exposure to high salinity, confirming an important role of floridoside in the osmoadjustment of cnidarian holobionts. This thesis demonstrates osmoacclimatization of F. granulosa and osmoadjustment of cultured Symbiodinium. All three main compartments (i.e. coral host, Symbiodinium, bacteria) seem to contribute to the coral holobionts salinity adjustment. However, the exact mechanisms of coral host and bacteria contribution remain to be determined. Floridoside likely constitutes a conserved osmolyte increasing the salinity resilience of Symbiodinium and also of the cnidarian/coral holobiont. Floridoside further possess’ antioxidative properties, possibly providing a protection from reactive oxygen species formation as a result of salinity stress or/and other environmental stressors.
Advisors:
Voolstra, Christian R. ( 0000-0003-4555-3795 )
Committee Member:
Ravasi, Timothy ( 0000-0002-9950-465X ) ; Moran, Xose Anxelu G. ( 0000-0002-9823-5339 ) ; Bourne, David
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Program:
Marine Science
Issue Date:
Apr-2017
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorVoolstra, Christian R.en
dc.contributor.authorRöthig, Tillen
dc.date.accessioned2017-04-26T13:41:49Z-
dc.date.available2017-04-26T13:41:49Z-
dc.date.issued2017-04-
dc.identifier.urihttp://hdl.handle.net/10754/623283-
dc.description.abstractCoral reefs are under considerable decline. The framework builders in coral reefs are scleractinian corals, which comprise so-called holobionts, consisting of cnidarian host, algal symbionts (genus Symbiodinium), and other associated microbes. Corals are commonly considered stenohaline osmoconformers, possessing limited capability to adjust to salinity changes. However, corals differ in their ability to cope with different salinities. The underlying mechanisms have not yet been addressed. To further understand putative mechanisms involved, I examined coral holobiont osmoregulation conducting a range of experiments on the coral Fungia granulosa. In my research F. granulosa from the Red Sea exhibited pronounced physiological reactions (decreased photosynthesis, cessation of calcification) upon short-term incubations (4 h) to high salinity (55). However, during a 29-day in situ salinity transect experiment, coral holobiont photosynthesis was unimpaired under high salinity (49) indicating acclimatization. F. granulosa microbiome changes after the 29-day high salinity exposure aligned with a bacterial community restructuring that putatively supports the coral salinity acclimatization (osmolyte synthesis, nutrient fixation/cycling). Long-term incubations (7 d) of cultured Symbiodinium exhibited cell growth even at ‘extreme’ salinity levels of 25 and 55. Metabolic profiles of four Symbiodinium strains exposed to increased (55) and decreased (25) salinities for 4 h indicated distinct carbohydrates and amino acids to be putatively involved in the osmoadjustment. Importantly, under high salinity the osmolyte floridoside was consistently increased. This could be corroborated in the coral model Aiptasia and in corals from the Persian/Arabian Gulf, where floridoside was also markedly increased upon short- (15 h) and long-term (>24 months) exposure to high salinity, confirming an important role of floridoside in the osmoadjustment of cnidarian holobionts. This thesis demonstrates osmoacclimatization of F. granulosa and osmoadjustment of cultured Symbiodinium. All three main compartments (i.e. coral host, Symbiodinium, bacteria) seem to contribute to the coral holobionts salinity adjustment. However, the exact mechanisms of coral host and bacteria contribution remain to be determined. Floridoside likely constitutes a conserved osmolyte increasing the salinity resilience of Symbiodinium and also of the cnidarian/coral holobiont. Floridoside further possess’ antioxidative properties, possibly providing a protection from reactive oxygen species formation as a result of salinity stress or/and other environmental stressors.en
dc.language.isoenen
dc.subjectMetabolite Protilingen
dc.subjectRed Seaen
dc.subjectCoral Reefen
dc.subjectcoral holobionten
dc.subjectClimate changeen
dc.subjectBacterial Community Protilingen
dc.titleOsmoadjustment in the Coral Holobionten
dc.typeDissertationen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberRavasi, Timothyen
dc.contributor.committeememberMoran, Xose Anxelu G.en
dc.contributor.committeememberBourne, Daviden
thesis.degree.disciplineMarine Scienceen
thesis.degree.nameDoctor of Philosophyen
dc.person.id122297en
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