Differential coral bleaching-contrasting the activity and response of enzymatic antioxidants in symbiotic partners under thermal stress

Krueger, Thomas, Hawkins, Thomas D., Becker, Susanne, Pontasch, Stefanie, Dove, Sophie, Hoegh-Guldberg, Ove, Leggat, William, Fisher, Paul L., and Davy, Simon K. (2015) Differential coral bleaching-contrasting the activity and response of enzymatic antioxidants in symbiotic partners under thermal stress. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 190. pp. 15-25.

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Abstract

Mass coral bleaching due to thermal stress represents a major threat to the integrity and functioning of coral reefs. Thermal thresholds vary, however, between corals, partly as a result of the specific type of endosymbiotic dinoflagellate (Symbiodinium sp.) they harbour. The production of reactive oxygen species (ROS) in corals under thermal and light stress has been recognised as one mechanism that can lead to cellular damage and the loss of their symbiont population (Oxidative Theory of Coral Bleaching). Here, we compared the response of symbiont and host enzymatic antioxidants in the coral species Acropora millepora and Montipora digitata at 28 degrees C and 33 degrees C. A. millepora at 33 degrees C showed a decrease in photochemical efficiency of photosystem II (PSII) and increase in maximum midday excitation pressure on PSII, with subsequent bleaching (declining photosynthetic pigment and symbiont density). M. digitata exhibited no bleaching response and photochemical changes in its symbionts were minor. The symbiont antioxidant enzymes superoxide dismutase, ascorbate peroxidase, and catalase peroxidase showed no significant upregulation to elevated temperatures in either coral, while only catalase was significantly elevated in both coral hosts at 33 degrees C Increased host catalase activity in the susceptible coral after 5 days at 33 degrees C was independent of antioxidant responses in the symbiont and preceded significant declines in PSII photochemical efficiencies. This finding suggests a potential decoupling of host redox mechanisms from symbiont photophysiology and raises questions about the importance of symbiont-derived ROS in initiating coral bleaching.

Item ID: 41791
Item Type: Article (Refereed Research - C1)
Keywords: APX, Acropora millepora, CAT, global change, Montipora digitata, oxidative stress, SOD, symbiodinium, symbiosis, thermal biology
ISSN: 1531-4332
Funders: Royal Society of New Zealand (RSNZ)
Projects and Grants: RSNZ Marsden Fund contract number VUW0902
Date Deposited: 08 Dec 2015 18:15
FoR Codes: 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060702 Plant Cell and Molecular Biology @ 100%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960305 Ecosystem Adaptation to Climate Change @ 80%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 20%
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