Impact of bleaching stress on the function of the oxygen evolving complex of zooxanthellae from scleractinian corals

Ross Hill*, Peter J. Ralph

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Global climate change is leading to the rise of ocean temperatures and is triggering mass coral bleaching events on reefs around the world. The expulsion of the symbiotic dinoflagellate algae is believed to occur as a result of damage to the photosynthetic apparatus of these symbionts, although the specific site of initial impact is yet to be conclusively resolved. Here, the sensitivity of the oxygen evolving complex (OEC) to bleaching stress was studied as well as its natural variation between seasons. The artificial electron donor, diphenyl carbazide (DPC), was added to cultured, freshly isolated and expelled (bleaching treatments only) zooxanthellae suspensions. Chl a fluorescence and oxygen production measurements showed that upon addition of DPC, no restoration of diminished photochemical efficiency occurred under control or bleaching conditions. This result was consistent between 12 h and 5 d bleaching treatments on Pocilloporadamicornis, indicating that the OEC is not the primary site of damage, and that zooxanthellae expulsion from the host is a nonselective process with respect to the functioning of the OEC. Further experiments measuring fast induction curves (FICs) revealed that in both summer and winter, the temperature when OEC function was lost occurred between 7°C and 14°C above the sea surface temperature. FIC and oxygen production measurements of P. damicornis during exposure to bleaching stress demonstrated that the thermotolerance of the OEC increased above the temperature of the bleaching treatment over a 4 h period. This finding indicates that the OEC has the capacity to acclimate between seasons and remains functional at temperatures well above bleaching thresholds.

Original languageEnglish
Pages (from-to)299-310
Number of pages12
JournalJournal of Phycology
Volume44
Issue number2
DOIs
Publication statusPublished - Apr 2008
Externally publishedYes

Keywords

  • Chlorophyll a fluorescence
  • Coral bleaching
  • Donor side
  • Fast induction curves
  • O-J-I-P
  • Photosystem II
  • Pulse amplitude modulated (PAM)

Fingerprint Dive into the research topics of 'Impact of bleaching stress on the function of the oxygen evolving complex of zooxanthellae from scleractinian corals'. Together they form a unique fingerprint.

Cite this