Authors

C. A. Downs; K. E. McDougall; C. M. Woodley; J. E. Fauth; R. H. Richmond; A. Kushmaro; S. W. Gibb; Y. Loya; G. K. Ostrander;E. Kramarsky-Winter

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Abbreviated Journal Title

PLoS One

Keywords

CHLOROPLAST THYLAKOID MEMBRANES; II REACTION-CENTER; PHOTOSYSTEM-II; OXIDATIVE STRESS; SEA-ANEMONE; EVOLUTIONARY DIFFERENTIATION; STRUCTURAL; REORGANIZATION; STYLOPHORA-PISTILLATA; ELECTRON-TRANSPORT; GONIASTREA-ASPERA; Multidisciplinary Sciences

Abstract

Coral bleaching is a significant contributor to the worldwide degradation of coral reefs and is indicative of the termination of symbiosis between the coral host and its symbiotic algae (dinoflagellate; Symbiodinium sp. complex), usually by expulsion or xenophagy (symbiophagy) of its dinoflagellates. Herein, we provide evidence that during the earliest stages of environmentally induced bleaching, heat stress and light stress generate distinctly different pathomorphological changes in the chloroplasts, while a combined heat-and light-stress exposure induces both pathomorphologies; suggesting that these stressors act on the dinoflagellate by different mechanisms. Within the first 48 hours of a heat stress (32 degrees C) under low-light conditions, heat stress induced decomposition of thylakoid structures before observation of extensive oxidative damage; thus it is the disorganization of the thylakoids that creates the conditions allowing photo-oxidative-stress. Conversely, during the first 48 hours of a light stress (2007 mmoles m(-2) s(-1) PAR) at 25 degrees C, condensation or fusion of multiple thylakoid lamellae occurred coincidently with levels of oxidative damage products, implying that photo-oxidative stress causes the structural membrane damage within the chloroplasts. Exposure to combined heat-and light-stresses induced both pathomorphologies, confirming that these stressors acted on the dinoflagellate via different mechanisms. Within 72 hours of exposure to heat and/or light stresses, homeostatic processes (e. g., heat-shock protein and anti-oxidant enzyme response) were evident in the remaining intact dinoflagellates, regardless of the initiating stressor. Understanding the sequence of events during bleaching when triggered by different environmental stressors is important for predicting both severity and consequences of coral bleaching.

Journal Title

Plos One

Volume

8

Issue/Number

12

Publication Date

1-1-2013

Document Type

Article

Language

English

First Page

16

WOS Identifier

WOS:000327949300003

ISSN

1932-6203

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