Tsang, Yu Man. / "November 2009." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 268-277). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.iii / Content --- p.vii / List of Tables --- p.ix / List of Figures --- p.xx / Chapter Chapter One --- General Introduction --- p.1 / Introduction --- p.1 / Coral Reefs --- p.1 / Coral-Algal Symbiosis --- p.2 / The Dinoflagellate Symbiodinium --- p.11 / Coral Communities in Hong Kong --- p.18 / Objectives --- p.21 / Study Sites - Tung Ping Chau Marine Park --- p.21 / Coral Species chosen for the Experiment --- p.23 / Platygyra acuta --- p.23 / Porites lutea --- p.23 / Thesis Outline --- p.24 / Chapter Chapter Two --- Temporal variation in photophysiological parameters of Hong Kong corals and their relationship with the environmental factors --- p.28 / Introduction --- p.28 / Methods and Materials --- p.33 / Study Sites --- p.33 / Coral Sampling for zooxanthellae density and chlorophyll concentration analysis --- p.34 / Measurement of changes in the photosynthtic activity of the corals --- p.38 / Environmental Factors --- p.38 / Data analysis --- p.39 / Results --- p.41 / Density of Zooxanthellae --- p.41 / Concentrations of Chlorophyll a and c2 (per zooxanthella) --- p.43 / Concentrations of Chlorophyll a and c2 (per surface area) --- p.46 / Chlorophyll ratio --- p.49 / Effective quantum yield --- p.51 / Photosynthetically active radiation (PAR) --- p.54 / Intra-colony variation for Platygyra acuta --- p.56 / Comparison between Platygyra acuta and Porites lutea --- p.64 / Environmental factors and their correlations with photophysiological parameters in corals --- p.68 / Discussion --- p.73 / Density of zooxanthellae --- p.74 / Concentrations of Chlorophyll a and c2 --- p.80 / Chlorophyll ratio --- p.85 / Effective quantum yield --- p.88 / Intra-colony variation --- p.94 / Between species comparison --- p.98 / Summary --- p.107 / Chapter Chapter Three --- PCR-RFLP Analysis on Symbiodinium in Platygyra acuta --- p.241 / Introduction --- p.241 / Methods and Materials --- p.244 / Sample collection --- p.244 / Molecular phylotyping --- p.245 / Results --- p.247 / Discussion --- p.249 / Summary --- p.257 / Chapter Chapter Four --- Summary and Conclusion --- p.262 / References --- p.268

Coral reefs constitute some of the most prolific and diverse ecosystems on our planet, but also among the most threatened. This thesis investigates the effects of environmental stressors on corals’ metabolism and symbiont diversity. Paper I shows that the coral Turbinaria mesenterina withstood a single stressor while a combination of two stressors (decreased salinity and increased seawater temperature) lead to decreased metabolism. Increased seawater temperature in combination with two stressors (enhanced nutrients and decreased salinity) lead to rapid mortality of all specimens. Paper II shows that chronic stress in combination with increased seawater temperature affects coral species differently. Porites lutea did not show any difference in response to temperature increase, regardless of environmental disturbance history, while Galaxea fascicularis’ metabolism was negatively affected in chronically disturbed corals but not in corals from less disturbed areas. The main explanation for the difference in response between the two species is different compositions of endosymbionts as found in paper III. P. lutea only harboured the symbiont C15, regardless of environment, whilst D1a dominated the nearshore G. fascicularis and C1 dominated offshore corals. In paper IV there was a clear inshore-offshore pattern of D1a along the whole coast of Vietnam, where D1a dominated inshore. In contrast, the five symbionts belonging to group C displayed a strong latitudinal gradient, with diversity increasing from north to south. The coral host showed higher diversity offshore than inshore. The thesis emphasizes the importance of improving water quality (paper I and II) and protecting marginal areas since tolerant coral hosts and symbionts can be found there (paper III and IV), as well as safeguarding areas with high symbiont diversity (paper IV) to increase the ability of corals to withstand future environmental changes. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Looking at the metabolite profile of an organism provides insights into the metabolomic state of a cell and hence also into pathways employed. Little is known about the metabolites produced by corals and their algal symbionts. In particular, corals from the central Red Sea are understudied, but interesting study objects, as they live in one of the warmest and most saline environments and can provide clues as to the adjustment of corals to environmental change. In this study, we applied gas chromatography – mass spectrometry (GC–MS) metabolite profiling to analyze the metabolic profile of four coral species and their associated symbionts: Fungia granulosa, Acropora hemprichii, Porites lutea, and Pocillopora verrucosa. We identified and quantified 102 compounds among primary and secondary metabolites across all samples. F. granulosa and its symbiont showed a total of 59 metabolites which were similar to the 51 displayed by P. verrucosa. P. lutea and A. hemprichii both harbored 40 compounds in conjunction with their respective isolated algae. Comparing across species, 28 metabolites were exclusively present in algae, while 38 were exclusive to corals. A principal component and cluster analyses revealed that metabolite profiles clustered between corals and algae, but each species harbored a distinct catalog of metabolites. The major classes of compounds were carbohydrates and amino acids. Taken together, this study provides a first description of metabolites of Red Sea corals and their associated symbionts. As expected, the metabolites of coral hosts differ from their algal symbionts, but each host and algal species harbor a unique set of metabolites. This corroborates that host-symbiont species pairs display a fine-tuned complementary metabolism that provide insights into the specific nature of the symbiosis. Our analysis also revealed aquatic pollutants, which suggests that metabolite profiling might be used for monitoring pollution levels and assessing environmental impact.