One of the main focus of coral reef ecology has been to shed light on the importance of all microbial members of coral holobiont and how their interactions contribute to the coral’s resilience. However, knowledge is lacking about the composition of microbial communities inhabiting the surface mucus layer of corals including Fungia fungites, a species that lives under stressful conditions close to fish farms in Vietnam. I investigated the prokaryotic communities that are thriving in Fungia fungites surface mucus layer (SML) in the wild and how they were affected upon antibiotics and nitrogen stress using 16S rRNA gene-based techniques. Firstly, I observed a significant alteration in the composition of microbial communities due to antibiotics effect, with exposed communities featuring lower richness and α-diversity in contrast to the controls. Further, mucosal microbial communities were found to be mostly dominated by Proteobacteria (especially of the classes of Alphaproteobacteria and Gammaproteobacteria) and less by Bacteroidetes (Flavobacteriia). Results from this study suggest a developed antibiotic resistance of Alteromonadales and Campylobacterales indicated by their increased abundance upon antibiotics effect. Moving forward, future studies should focus on exploring also the contribution of non-prokaryotic microbial members of Fungia fungites holobiont and how antibiotic resistance can potentially influence coral’s health. The results support that Fungia fungites SML microbial communities are strongly affected by antibiotics exposure and call for future research to focus on the function of these microbial communities and how they can contribute to the coral’s resilience.

No description available.

No description available.

This thesis addresses the utility of deep-water coral geochemistry and its potential to reconstruct oceanographic conditions in the Straits of Florida. Through stable isotope and elemental analyses of the carbonate skeletons and use of available geochemical proxy calibration equations, present and past environmental parameters were determined. Over the last several years, scientific expeditions to the bottom of the Straits of Florida have revealed hundreds of deep-water coral mounds and led to the collection of extensive oceanographic data, sediment samples, and deep-water coral specimens. In 2005-2006, an Autonomous Underwater Vehicle (AUV) was used to map the coral mound fields at five sites with the use of geophysical imaging technology, and the manned Johnson-Sea-Link II submersible was deployed for further exploration and sample collection. The AUV and the submersible CTD also measured numerous environmental parameters, including temperature and salinity. With the goal of reconstructing environmental parameters across the Straits of Florida, Scleractinian and gorgonian deep-water coral specimens were selected from three sites spanning the Straits. Each coral was sampled at the highest resolution possible and analyzed for stable isotopes and elemental concentrations. Resulting geochemical data, specifically d18O, d13C, Sr/Ca, and Mg/Ca, was then used with previously published and newly developed calibration equations to calculate temperature, salinity, and seawater density. Kinetic and vital effects were also examined and taken into account while reconstructing environmental parameters using the coral geochemistry. Additional reconstructions using stable isotopic values from benthic foraminifera corroborated the geochemical reconstructions, and analyses of pteropods and surface sediment samples provided further insight into the oceanographic conditions at the bottom of the Straits of Florida. Results from geochemical reconstructions agreed with in situ data, indicating that slightly warmer bottom temperatures exist on the eastern side of the Straits and salinity variability among the three sites is minimal. This suggests that the deep-water coral skeletons are sensitive recorders of the environmental conditions in which they lived. Ultimately, in situ measurements and reconstructed parameters showed that there is little variability across the bottom of the Straits and that Antarctic Intermediate Water (AAIW) is the only apparent water mass in the area at that depth. Moreover, comparison of the coral habitat from this study with others from around the world demonstrated that certain conditions are required for deep-water coral growth, and that these same parameters are common to deep-water reef systems throughout the globe. Further sampling and geochemical analyses of deep-water corals in the region may be used to gain additional insight into the oceanographic conditions surrounding the coral mounds both presently and in the past. As with other previously studied deep-water coral systems, this highlights the potential for the reconstruction of paleo environmental records from deep-water corals in the Straits of Florida.

Soft corals of the genus Sinularia have been proved to yield a wide variety of secondary metabolites. In order to search for novel bioactive substances from marine organisms, we have investigated the secondary metabolites of the soft corals Sinularia leptoclados and Sinularia sandensis. Chromatographic separation of the organic extracts of the Formosan soft coral Sinularia leptoclados, collected at Dongsha Atoll of the South China Sea, led to the isolation of four new steroids (1-3 and 11), along with an unexpected artificial sterol (5) and six known 9,11-secosteroids (4 and 6-10). In addition, the acetone extract of the soft coral, Sinularia sandensis, collected at the Tsau-Lou-Cho Island off the southwestern coast of Taiwan, yielded three novel sesquiterpenoids (12-14). The structures of the isolated metabolites were elucidated by extensive spectroscopic analyses (IR, UV, mass, optical rotations, CD, 1D and 2D NMR) and by comparison of the spectral data with those of the related known compounds. Moreover, the absolute configuration of 12 was established by application of modified Mosher¡¦s method. The cytotoxicity against of P-388 (mouse lymphocytic leukemia), HT-29 (human colon adenocarcinoma), and A-549 (human lung epithelial carcinoma) cells of metabolites 1-4 and 6-14 as well as the anti-HCMV (human cytomegalovirus) activities of metabolites 4, 10, 11, and 13 were evaluated. Metabolites 2, 4 and 6-10 exhibited significant activity against P-388 cell in vitro (IC50¡Ø4 mg/mL).

Corals are marine animals from the class Anthozoa and are widely distributed in tropical and subtropical seawaters. They are considered as an important source of lead compounds for drug discovery. For evaluating the medicinal activities of briarane-type diterpenoids (BrDs) from marine coral Briareum excavatum, the regulation of a group of briarane-type diterpenoids (BrDs) on dendritic cell (DC) function, TPA-induced dermatitis and type 1 diabetes was investigated. The results show that the BrD excavatolide K (BrD2) remarkably suppressed the activation of human DCs, especially the expression of IL-12 p40. This inhibitory effect was mediated apparently by interference with the rictor-mTOR/Akt-mediated signaling network, resulting in persistent-phase activation of NF-kB and Erk1/2 signalings. In addition, the 8,17-epoxide of BrDs was observed to play a crucial role in inhibition of IL-12 p40 expression. Replacement of the C-12 hydroxyl group with longer esters in BrDs gradually decreased this inhibitory activity in human DCs. BrD excavatolide B (BrD1) effectively suppressed the capacity of mouse bone marrow-derived DCs to induce an antigen-specific Th1, response via the inhibition of IL-12 expression. Moreover, excavatolide B prevented the onset of autoreactive T cell-mediated diabetes in NOD/SCID mice. Furthermore, excavatolide B remarkably suppressed TPA-induced vascular permeability and edema in test skin tissues. At the biochemical level, excavatolide B inhibited TPA-induced expression of cyclooxygenase-2, inducible nitric oxide synthase and matrix metalloproteinase-9, the key indicators of cutaneous inflammation. This inhibition is apparently mediated by interference with the Akt/NF-kB-mediated signaling network. Together, these studies demonstrate that BrDs from specific marine corals can effectively regulate defined molecular and cellular functions of dendritic cells, suppress TPA-induced dermatitis, and prevent type 1 diabetes in murine models suggesting that BrDs may warrant further investigation as natural immunomodulatory agents or therapeutics.

The coral-inhabiting snail Coralliophila violacea is a common species in the Indo-Pacific coral reefs and it usually lives on the surface of its host, Porites spp. In this study, field survey on the distribution of C. violacea on poritid corals, Porites spp. among sites were conducted. And the influence of flow rate on the distribution of snails was also examined through a simulation model. The sampling sites were northeastern of Taiwan, Taitung, Penghu, Lutao, Hsiao-liu-chiu and Lanyu. The presence of spatial variability in the relative abundance of C. violacea on porited corals has been observed. The highest percentage of corals with snails was in northeastern Taiwan, i.e. 45% and the lowest ones were in Lutao and Lanyu, i.e. 12%. The distribution of snails among sites were heterogeneous (X2-test of independence; p<0.001). Significant differences of shell length in snails among sites were also found. Among them, the distribution pattern of shell length in snails from Lutao and Lanyu was not normal. Difference in the age-distribution of snails among sites was present. In general, five and six years old snails were most abundant. A lack of snails under two years old had been found in Lutao, Lanyu and Penghu. Based on the simulated downward trajectory of snail larvae, it was indicated that a minimum substratum for larval settlement varied with flow rates and depth of water.

Chromatographic purification of a methylene chloride extract of Formosan soft coral Sarcophyton crassocaule (collected in Green island) led to the isolation of two new (1S*, 3R*, 4R*, 7E, 11E, 14R*)-3, 4-epoxycembra-7, 11, 15-trien-1, 14-olide (1) and (1R*, 3E, 7E,11R*, 12S*, 14R*)-11, 12-epoxycembra-3, 7, 15-trien-1, 14-olide (2) isomeric diterpenoids , a known cyclic peroxide diterpenoid (1R*, 2S*, 3E, 7S*, 8R*, 11S*, 12Z)-8, 11-epidioxy-7-acetoxycembra-3, 12, 15-trien-1, 2-olide (3), as well as two known (24S)-24-methylcholestane-3b, 5a, 6b-triol (4) and 24x-methyl-cholestane -3b, 5a, 6b, 25-tetrol 25-monoacetate (5) steroids. Chromatographic fractionation of a methylene chloride extract of two Formosan soft corals Sarcophyton elegans (collected in Green island) led to the isolation of a known 24x-methylcholestane -3b, 5a, 6b, 25-tetrol 25-monoacetate (5) steroid, the methylene chloride extract of Sarcophyton trocheliophorum, on the other hand, afforded a known diterpenoid, (+)-isosarcophine (6). Purification of a methylene chloride extract of Octocorallia soft coral (unidentified) led to the isolation of two known steroids, cholesterol (7) and (22E, 24S)-24-methylcholesta-5, 22-dien-3b-ol (8). Compounds 1-7 exhibited cytotoxicity against P388 cancer cell line. Compounds 2 and 5 were active against HT-29 cancer cell line.

The organic extracts of two marine soft corals Pachyclavularia violacea and Subergorgia suberosa, collected along the coast of Kenting, Taiwan, were found to exhibit significant cytotoxicities toward several cancer cell lines (Table 1). In order to discover bioactive compounds, we have investigated the chemical constituents of these two marine organisms. Investigation on P. violacea has led to the isolation of twenty-five compounds, including twenty-one new compounds, pachyclavulariolide G (1), pachyclavulariolide H (3), pachyclavulariolide I (4), pachyclavulariolides J¡VS (6¡V15), pachyclavulariaenones A¡VG (16¡V22), secopachyclavulariaenone A (23), and four known compounds pachyclavulariolide (2), pachyclavulariolide E (5), pachyclavulariolide A (24) and pachyclavulariolide B (25). Also, we have investigated the chemical constituents of S. suberosa. This study led to the isolation of fifteen compounds, including six new compounds, 2b-acetoxysubergorgic acid (27), subergorgiol (31), suberosols A¡VD (34¡V37), and nine known compounds, subergorgic acid (26), 2b-hydroxysubergorgic acid (28), methyl ester of subergorgic acid (29), 2b-acetoxy methyl ester of subergorgic acid (30), buddledin D (32), buddledin C (33), 5b-pregnan-3,20-dione (38), £G1- 5b-pregnen-3,20-dione (39) and 3a-acetoxy -5b-pregnan-20-one (40). Compounds 39, 40 were isolated from natural sources for the first time. Structures of these compounds were determined on the basis of chemical method and spectroscopic evidences. Cytotoxicities of these compounds against P-388, KB, A-549 and HT-29 cancer cell lines also were described. Compound, 7, 32, 33, 36, 37 have been found to show moderate activity toward the above cancer cell lines.

The methylene chloride extracts of Formosan soft coral Sarcophyton crassocule Von. Marenzeller (collected at Green Island off Taiwan) were found to exhibit significant cytotoxicity against P-388, HT-29, and A-549 cancer lines. Chromatographic separation led to the isolation of three known cembrane diterpenoids, GN16-34 (1), GN16-35 (2), GN16-40 (3), and a new cembrane, GN16-62 (4). The methylene chloride and acetone extracts of Formosan soft coral Xenia puerto-galerae Roxas (collected at Green Island off Taiwan) were found to exhibit significant cytotoxicity against P-388 and A-549 cancer cell lines. Chromatographic separation resulted in the isolation of six new cadinane sesquiterpenes, GN44-28 (5), GN44-30 (6), GN44-44 (7), GN44-66 (8), GN44-173 (9), GN44-149 (10), and one known dicarbocyclic diterpenes with a bicyclic [4.3.1] ring system, GN44-199 (11). Compounds 3 and 4 exhibited significant cytotoxicity against P-388, HT-29, and A-549 cancer cell lines. Compounds 1 and 2 exhibited significant cytotoxicity against P-388 cancer cell lines. Compounds 5 and 7 exhibited significant cytotoxicity against A-549 cancer cell line. compound 10 exhibited significant cytotoxicity against P-388 and A-549 cancer cell lines.