Yeung, Chung Wing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 143-156). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract (English) --- p.iii / Abstract (Chinese) --- p.vi / Contents --- p.vii / List of Tables --- p.xii / List of Figures --- p.xii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Ecological and economic importance of coral reef habitats --- p.1 / Chapter 1.2 --- D egradation of coral reefs --- p.2 / Chapter 1.2.1 --- Natural recovery --- p.3 / Chapter 1.2.2 --- Restoration of disturbed reefs --- p.3 / Chapter 1.2.2.1 --- Whole colony transplantation --- p.4 / Chapter 1.2.2.2 --- Fragment transplantation --- p.4 / Chapter 1.2.2.3 --- Coral nursery --- p.5 / Chapter 1.3 --- Studies on octocorals --- p.6 / Chapter 1.3.1 --- Functional ecology of octocorals --- p.7 / Chapter 1.3.2 --- Biodiversity of octocorals in Hong Kong --- p.9 / Chapter 1.3.3 --- Threats on octocorals in Hong Kong --- p.10 / Chapter 1.4 --- The focus and significance of the present study --- p.12 / Chapter 1.4.1 --- "Lobophytum sarcophytoides, the study organism" --- p.14 / Chapter 1.4.2 --- Objectives --- p.15 / Chapter 1.5 --- Thesis Outline --- p.16 / Chapter Chapter 2 --- Seasonal Variation and Size-dependent Eco-physiological Performances of the Soft Coral Lobophytum sarcophytoides / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.1.1 --- Damage recovery --- p.20 / Chapter 2.1.2 --- Photosynthetic activity --- p.21 / Chapter 2.1.3 --- Reproductive biology --- p.22 / Chapter 2.1.4 --- Growth rate --- p.23 / Chapter 2.1.5 --- Significance and objectives --- p.23 / Chapter 2.2 --- Study Sites --- p.24 / Chapter 2.2.1 --- Lan Guo Shui (LGS) --- p.24 / Chapter 2.2.2 --- Tolo Harbour (MSL) --- p.25 / Chapter 2.3 --- Methodologies --- p.27 / Chapter 2.3.1 --- Sample collection --- p.27 / Chapter 2.3.2 --- Treatment of samples --- p.27 / Chapter 2.3.3 --- Health condition --- p.28 / Chapter 2.3.4 --- Damage recovery --- p.29 / Chapter 2.3.5 --- Growth rate --- p.29 / Chapter 2.3.6 --- Photosynthetic activity --- p.30 / Chapter 2.3.7 --- Reproductive biology --- p.30 / Chapter 2.3.8 --- Statistical Analysis --- p.31 / Chapter 2.4 --- Results --- p.32 / Chapter 2.4.1 --- Acclimation of transplanted corals --- p.32 / Chapter 2.4.2 --- Health condition --- p.33 / Chapter 2.4.3 --- Growth rate --- p.34 / Chapter 2.4.4 --- Photosynthetic activity --- p.38 / Chapter 2.4.5 --- Damage recovery --- p.39 / Chapter 2.4.6 --- Reproductive biology --- p.40 / Chapter 2.5 --- Discussion --- p.41 / Chapter 2.5.1 --- Diurnal expansion and contraction of colonies --- p.41 / Chapter 2.5.2 --- Size fluctuation of the colonies --- p.42 / Chapter 2.5.3 --- Possible factors for the high initial mortality of corals --- p.43 / Chapter 2.5.4 --- Causes of bleaching and the harmful effects --- p.44 / Chapter 2.5.5 --- Energy allocation between reproduction and growth --- p.47 / Chapter 2.5.6 --- Quick healing of cut fragments and its ecological implication --- p.48 / Chapter 2.5.7 --- Choice of suitable fragment size for nursery use --- p.49 / Chapter 2.5.8 --- Suitable season for conducting the experiment --- p.50 / Chapter 2.6 --- Summary --- p.51 / Chapter Chapter 3 --- Effects of Temperature on the Health Condition and Photosytnthetic Activity of the Soft Coral Lobophytum sarcophytoides / Chapter 3.1 --- Introduction --- p.69 / Chapter 3.2 --- Methodologies --- p.73 / Chapter 3.2.1 --- Sample collection --- p.73 / Chapter 3.2.2 --- Experimental set-up of aquaria for growing corals --- p.73 / Chapter 3.2.2.1 --- Temperature experiment I --- p.74 / Chapter 3.2.2.2 --- Temperature experiment II --- p.74 / Chapter 3.2.2.3 --- Temperature experiment III --- p.76 / Chapter 3.2.3 --- Health condition --- p.76 / Chapter 3.2.4 --- Photosynthetic activity --- p.77 / Chapter 3.2.5 --- Statistical analysis --- p.78 / Chapter 3.3 --- Results --- p.79 / Chapter 3.3.1 --- Temperature experiment I --- p.79 / Chapter 3.3.1.1 --- Health condition --- p.79 / Chapter 3.3.1.2 --- Photosynthetic activity --- p.80 / Chapter 3.3.2 --- Temperature experiment IIA --- p.81 / Chapter 3.3.2.1 --- Health condition --- p.81 / Chapter 3.3.2.2 --- Photosynthetic activity --- p.83 / Chapter 3.3.3 --- Temperature experiment IIB --- p.84 / Chapter 3.3.3.1 --- Health condition --- p.84 / Chapter 3.3.3.2 --- Photosynthetic activity --- p.85 / Chapter 3.3.4 --- Temperature experiment III --- p.85 / Chapter 3.3.4.1 --- Health condition --- p.85 / Chapter 3.3.4.2 --- Photosynthetic activity --- p.86 / Chapter 3.4 --- Discussion --- p.87 / Chapter 3.4.1 --- The effect of acclimation --- p.87 / Chapter 3.4.2 --- Temperature tolerance range of L. sarcophytoides --- p.90 / Chapter 3.4.3 --- Indicators of coral health --- p.92 / Chapter 3.4.3.1 --- Photosynthetic activity --- p.92 / Chapter 3.4.3.2 --- Colony contraction --- p.94 / Chapter 3.4.3.3 --- Bleaching --- p.95 / Chapter 3.4.3.4 --- Algal overgrowth --- p.97 / Chapter 3.4.3.5 --- Attachment of transplanted corals --- p.99 / Chapter 3.5 --- Summary --- p.100 / Chapter Chapter 4 --- Reproductive Biology of Lobophytum sarcophytoides / Chapter 4.1 --- Introduction --- p.114 / Chapter 4.2 --- Methodologies --- p.117 / Chapter 4.2.1 --- Study site --- p.117 / Chapter 4.2.2 --- Sample collection and treatments --- p.117 / Chapter 4.3 --- Results --- p.119 / Chapter 4.3.1 --- Gametogenic development: Size changes --- p.119 / Chapter 4.3.2 --- Gametogenic development: Developmental stages --- p.120 / Chapter 4.3.2.1 --- Oogenesis --- p.120 / Chapter 4.3.2.2 --- Spermatogenesis --- p.121 / Chapter 4.4 --- Discussion --- p.122 / Chapter 4.4.1 --- Unusual oogenic development pattern in L sarcophytoides --- p.122 / Chapter 4.4.2 --- Possible effect of lack of a temperature cue on gametogenic development --- p.123 / Chapter 4.4.3 --- Alternative explanation: Energy allocation --- p.126 / Chapter 4.5 --- Summary --- p.128 / Chapter Chapter 5 --- Summary and Perspectives --- p.137 / References --- p.143

In the Caribbean, Acropora cervicornis (staghorn coral) exemplifies the worldwide anthropogenic decline of reef-building corals. From the mid-Pleistocene through the mid-1900s, A. cervicornis was a dominant framework builder, providing complex habitat for reef organisms. Since the 1980s, populations of A. cervicornis have declined by as much as 98%. Despite the overall decline, scattered remnants persist, and some appear to be thriving. As in recent studies on other acroporids, if we can identify variation in traits related to resilience in the remaining A. cervicornis, and understand the genetic basis of such variation, we could better forecast the species’ future response to climate change, and inform ongoing restoration efforts. Here, I compare phenotypic and transcriptomic indicators of resilience in A. cervicornis from two nearby but environmentally-disparate habitats on Turneffe Atoll, Belize: Calabash Caye forereef and Blackbird Caye backreef. Blackbird exhibits significantly higher flow, light, average temperature, and temperature variation. Over four years, I conducted a longitudinal study of 122 tagged coral colonies. Corals from Blackbird and Calabash, which I confirmed to be genetically distinct based upon single nucleotide polymorphisms, exhibited pronounced differences in traits related to resilience including the proportion of healthy tissue, chlorophyll, growth, and wound-healing. By most measures, Blackbird corals displayed superior indicators of resilience. Through a two-year reciprocal transplant study involving 120 corals, I identified substantial environmental plasticity in these traits, e.g., Blackbird corals transplanted to Calabash exhibited higher chlorophyll levels and more rapid wound healing than when grown in Blackbird, exceeding the native Calabash corals. RNA sequencing and assembly of site-specific transcriptomes revealed greater diversity of transcripts and genes from photosynthetic symbionts at Blackbird but greater diversity of bacterial associates at Calabash. Single nucleotide polymorphism (SNP) analyses using RNAseq data determined that corals from the two sites were separate putative populations. Principal components analysis of gene expression in natives and transplants revealed a clear distinction based on site of origin, but also a clear effect of environment. Thousands of differentially expressed genes distinguished the sites, including many genes implicated in heat stress, oxidative stress and UV-light stress. This genetic and phenotypic diversity of remnant staghorn populations on Turneffe represents a potential basis for future re-expansion of this important framework builder through natural or assisted shifts toward resilient populations. / 2023-02-03T00:00:00Z

Over the last 40 years, the Caribbean has lost half of its live coral cover, mostly in the form of Acropora cervicornis and A. palmata, due to disease, bleaching from rising water temperatures, and other stressors. To help restore these corals to reefs in Florida, the Coral Restoration Foundation (CRF) created nearshore nurseries and transplanted over 30,000 acroporid colonies across the Florida Keys. The objective of this thesis was to evaluate the growth, survivorship, and condition of nursery-raised A. cervicornis colonies that were part of two transplant projects: 1) photographic analyses of 17 past CRF transplant projects over the last seven years; and 2) a transplant experiment at Little Conch Reef to additionally assess the effects of depth, colony density, and the genetic composition of transplants. The photographic analyses included 2,428 individual colonies, 38 genotypes, and six reefs from 2007 to 2013. Results from the photographs were combined with one in situ monitoring effort that used SCUBA in 2014. In the Little Conch Reef experiment, 1,288 colonies from 14 genotypes were transplanted in October and November, 2013 at two depths (5m and 12m) in either cluster or thicket configurations. At each depth, clusters comprised 14 colonies, each placed within in 1m diameter radius, with ten monogenetic and six multigenetic structures. Thickets were 3.5m by 1.5m in size, with 10 colonies from each genotype forming its own subunit within the larger configuration. In June 2014, 963 additional colonies were added to the shallow site by stacking them on top of six existing clusters and one thicket to evaluate whether larger three-dimensional structures affected growth or survival. The Little Conch Reef experiment was monitored through January 2015. Results from the photographic analyses were: 1) maximum size of A. cervicornis transplants was approximately 40cm in diameter; 2) mortality increased after approximately two years; 3) despite high mortality, some colonies survived the duration of each project; and 4) frequent and long-term monitoring is required to assess factors that affect survival and condition. Results from the Little Conch Reef experiment suggest: 1) maximum skeletal diameter was unaffected by any of the treatments; 2) percent survival and percent live tissue were higher at the shallow site compared to the deep site, and similarly, the clusters outperformed the thickets, and multigenetic clusters outperformed their monogenetic counterparts; 3) location within the shallow site had an impact on survival and condition, with clusters doing better on the south side than on the north; and 4) stacking did not positively impact growth, survival, or condition. In general, the sizes and condition of natural populations of A. cervicornis throughout the Florida Keys are similar to results from both experiments and with other transplant projects conducted in the Caribbean. Remarkably, despite high mortality in nearly all of the projects, small numbers of colonies transplanted for most projects, a few colonies survived to 2014/2015. These colonies have the potential to act as a “seed population” that might produce sexually dispersed larvae better adapted at surviving mortality events and asexual fragments that may be better acclimated to the stressors related to their location. Evidence of persistence in this species and expansion northward in Florida suggest that it is too early to consider coral reefs a lost cause, and that coral restoration holds promise for enhancing recovery of A. cervicornis.