Tesis sobre el tema "Coral Physiology"

Human domination of global nutrient cycles is profoundly altering our planet. Yet on coral reefs, the effects of changing nutrient regimes have likely been over-simplified. This dissertation investigates the complexity of animal-nutrient interactions at the organismal level and explores how the outcomes of these interactions cascade through levels of biological organization. To do so, I examined the effects of nitrogen (N) and phosphorus (P) on corals and macroalgae, and how these effects in turn influenced reef communities and entire ecosystems. I show that P consistently increases coral growth rates while N has variable, often negative, effects on coral growth. The majority of this variability was explained by the contrasting responses of corals to ammonium, which had negligible effects on coral growth, versus nitrate, which consistently had negative effects on corals. Experimental manipulations of nutrient regimes revealed that these effects could be attributed, in part, to increased damage to the photosynthetic components of the corals’ endosymbionts. Nitrogen and P-enrichment also impacted macroalgae, increasing the nutrient content of algal tissue and in turn, consumption patterns of herbivorous fishes. Initial phase parrotfishes and juvenile surgeonfishes increased their feeding rates on algae rich in N and P respectively. However, adults from both species were irresponsive to algal nutrient content. At the community level, the effects of N and P on corals, algae and herbivory were linked to the development of distinct benthic communities. Algae cover was lower and coral growth rates higher around reef structures that were consistently enriched with N and P excreted by sheltering fishes. At the ecosystem level, I found that the responses of corals to N and P enrichment were similar to those of other nutrient-sharing mutualists. Across terrestrial and marine environments, I show that N and P enrichment consistently decouples mutualism performance, benefiting one partner at the expense of the other. Thus, collectively this dissertation demonstrates that the impacts of global nutrient loading resonate from single organisms through whole ecosystems.

The demise of reef-building corals potentially lies on the horizon, given ongoing climate change amid other anthropogenic environmental stressors. If corals cannot acclimatize or adapt to changing conditions, dramatic declines in the extent and health of the living reefs are expected within the next half century. The primary and proximal global threat to corals is climate change. Reef-building corals are dependent upon a nutritional symbiosis with photosynthetic dinoflagellates belonging to the group Symbiodinium. The symbiosis between the cnidarian host and algal partner is a stress-sensitive relationship; temperatures just 1°C above normal thermal maxima can result in the breakdown of the symbiosis, resulting in coral bleaching (the loss of Symbiodinium and/or associated photopigments) and ultimately, colony death. As ocean temperatures continue to rise, corals will either acclimatize or adapt to changing conditions, or will perish. By experimentally preconditioning the coral Acropora millepora via sublethal heat treatment, the coral acquired thermal tolerance, resisting bleaching during subsequent hyperthermal stress. The complex nature of the coral holobiont translates to multiple possible explanations for acclimatization: acquired thermal tolerance could potentially originate from the host itself, the Symbiodinium, or from the bacterial community associated with the coral. By examining the type of in hospite Symbiodinium and the bacterial community prior acclimation and after thermal challenge, it is shown that short-term acclimatization is not due to a distinct change in the dinoflagellate or prokaryote community. Though the microbial partnerships remain without considerable flux in preconditioned corals, the host transcriptome is dynamic. One dominant pattern was the apparent tuning of gene expression observed between preconditioned and non-preconditioned treatments, showing a modulated transcriptomic response to stress. Additionally several genes were upregulated in association with thermal tolerance, including antiapoptotic genes, lectins, and oxidative stress response genes. Upstream of two of these thermal tolerance genes, inhibitor of NFκB and mannose-binding lectin, DNA polymorphisms were identified which vary significantly between the northern and southern Great Barrier Reef. The impact of these mutations in putative promoter regions remains to be seen, but variation across thermally-disparate geography serves to generate hypotheses regarding the role of regulatory element evolution in a coral adaptation context.

Biology
Ph.D.
Cold-water corals act as critical foundation species in the deep sea by creating extensive three-dimensional habitat structures that support biodiversity hotspots. There is currently a paucity of data concerning the environmental requirements and physiology of cold-water corals, severely limiting our ability to predict how resilient they will be to future environmental change. Cold-water corals are expected to be particularly vulnerable to the effects of ocean acidification, the reduction in seawater pH and associated changes to the carbonate system caused by anthropogenic CO2 emissions. Here, the ecological niche and physiology of the cold-water coral Lophelia pertusa is explored to predict its sensitivity to ocean acidification. Species distribution models were generated in order to quantify L. pertusa’s niche in the Gulf of Mexico with regard to parameters including seafloor topography, the carbonate system, and the availability of hard substrate. A robust oceanographic assessment of the Gulf of Mexico was conducted in order to characterize the current environmental conditions at benthic sites, with a focus on establishing the baseline carbonate system in L. pertusa habitats. Finally, an experimental approach was used to test the physiological response of biogeographically separated L. pertusa populations from the Gulf of Mexico and the Norwegian coast to ocean acidification. Based on my findings, it appears that L. pertusa already persists near the edge of its viable niche space in some locations, and therefore may be highly vulnerable to environmental change. However, experimental results suggest that some populations may be surprisingly resilient to ocean acidification, yielding broad implications for the continued persistence of cold-water corals in future oceans.
Temple University--Theses

Symbiotic dinoflagellates in the genus Symbiodinium are critical to the success of scleractinian reef corals in shallow tropical seas. These symbionts are commonly isolated from hosts and cultured separately in liquid media (f/2 or ASP8a), but initial isolations can be prone to abundant contaminants that can persist long-term in culture. To help remove these contaminants, I developed a solid growth substrate composed of 1% f/2 medium in agar, supplemented with a variety of antibiotics, to help isolate individual clones and establish new ?axenic? cultures. I found that an antibiotic cocktail of kanamycin (50 µg/mL), ampicillin (100 µg/mL) and streptomycin (50 µg/mL) was the most effective at eliminating visual signs of contamination without apparent harm to a variety of Symbiodinium in culture. Photophysiological measurements of Symbiodinium grown on f/2 agar plates, taken using an Imaging Pulse Amplitude Modulated (I-PAM) fluorometer, were comparable with those grown in liquid f/2, both with and without antibiotics. Eight types of Symbiodinium in clades A-D grown on f/2 agar plates at low irradiance (19-46 µmol photons m-2 s-1) were exposed to higher irradiance conditions (50-90 µmol photons m-2s-1) for 13 days and their photosynthetic efficiencies (Fv/Fm) were compared using the I-PAM. There were significant differences among and within clades, except for two types in clade C (C2 and C3) which did not perform differently from eachother. All types showed reduced Fv/Fm after 12 days in higher light. Type D1a showed high mortality after 13 days of higher light stress. Finally, preliminary work to fluorescently label Symbiodinium determined that available vital stains were not generally practical for symbiosis studies. Attempts to transform Symbiodinium with a variety of plasmids containing fluorescent reporters and/or genes for antibiotic resistance were not successful, but did provide a baseline for future work. In summary, Symbiodinium cultures grown on solid substrates supplemented with antibiotics are useful for: (1) isolating individual cells or clones for subsequent applications and establishing and maintaining ?axenic? cultures that are free of observable contaminants; (2) directly comparing the photophysiology of different cultures using an I-PAM fluorometer; (3) quantifying cells on agar plates using the I-PAM and (4) selecting possible transgenic symbionts for symbiosis studies.

Black band disease (BBD) of corals is a temperature dependent, highly virulent, polymicrobial disease affecting reef-building corals globally. The microbial consortium of BBD is primarily comprised of functional physiological groups that include photosynthetic cyanobacteria, sulfate reducers, sulfide oxidizers and a vast repertoire of heterotrophic bacteria. Quorum sensing (QS), the cell-density dependent communication phenomenon in bacteria, is known to induce expression of genes for a variety of virulence factors in diseases worldwide. Microbes capable of QS release signals such as acyl homoserine lactones (AHLs) and autoinducer-2 (AI-2), which coordinate microbial interaction. The focus of the present study was to investigate the presence and potential role of QS in BBD pathogenicity, utilizing culture dependent and independent methodologies. Isolates across coral health states including BBD, were screened for production of QS signals, and AHL and AI-2 production capabilities were analyzed via LC-MS/MS. The effect of temperature on AHLs was also examined. Additionally, antimicrobial production capabilities of isolates were tested. BBD metagenomes were utilized to screen for sequences related to QS, antimicrobial synthesis, and antimicrobial resistance genes. BBD isolates represented a significantly higher proportion of isolates capable of producing QS signals in comparison to healthy coral isolates. Several AHLs produced by coral derived bacterial cultures were identified, and three AHLs, specifically 3OHC4, 3OHC5 and 3OHC6, showed a significant increase in production at an elevated temperature of 30 °C, which correlates with increased BBD incidence on reefs with increasing water temperature. Most of the BBD cultured isolates were identified as vibrios. Several sequences related to QS, antimicrobial synthesis and resistance genes were detected in the BBD metagenomes. Based on the findings of this study, a model for potential microbial interactions amongst BBD heterotrophs, centered around QS, is proposed. Taken together, the findings from this study provide a clearer understanding of the potential role of QS in BBD, and serve as the basis for further studies aimed at elucidating the pathogenesis of an intricate coral disease.

Depuis le début de la période industrielle, les activités humaines ont généré une augmentation importante de la concentration atmosphérique en CO2. Une partie de ce CO2 s’accumule dans l’atmosphère, entraînant une augmentation de l’effet de serre naturel et de la température à la surface du globe. Ce processus est plus connu sous le terme réchauffement climatique ou global. De plus, environ 25 % du CO2 produit sont absorbés par les océans. La dissolution du CO2 dans l’eau de mer, entraîne une augmentation de la concentration en protons et en ions bicarbonates (HCO3-) et une diminution de la concentration en ions carbonates (CO32-). Il en résulte une diminution du pH et du taux de saturation de l’eau de mer vis-à-vis du carbonate de calcium. L’ensemble de ces processus est appelé acidification des océans (AO). Le pH des eaux de surface océaniques a déjà diminué de 0,1 unité depuis le début de l’ère industrielle. Ce phénomène devrait s’intensifier au cours du siècle. Selon les prévisions moyennes d’émissions futures de gaz à effet de serre de l’IPCC, la température moyenne des eaux de surface devrait augmenter de 2 à 4 °C et son pH devrait diminuer de 0,3 à 0,4 unité d’ici 2100.

Au cours des deux dernières décennies, de nombreuses études ont mis en évidence l’impact négatif de l’AO sur les organismes marins. Les premières études ont été menées principalement en milieu artificiel et ont mis en évidence des conséquences majeures sur la physiologie des organismes, principalement au niveau individuel. Cependant, les dernières études menées dans le domaine ont souligné l'importance de mettre en place des expériences à long terme, à l'échelle de l'écosystème, et dans des conditions plus proches du milieu naturel. Ce type d’étude permet de prendre en compte les interactions écosystémiques et les processus d’acclimatation afin de mieux prévoir les effets directs mais aussi indirects de la diminution du pH dans les océans.

L’existence des récifs coralliens tropicaux dépend de la vitesse de formation du socle récifal qui les façonnent (principalement via la calcification des coraux hermatypiques) qui doit rester supérieure à sa (bio)érosion. D’une part, plusieurs études ont montré que le taux de calcification des coraux hermatypiques diminue lorsque la pCO2 augmente. D’autre part, les oursins sont d’importants bioérodeurs des récifs et contribuent donc à la perte de masse calcaire récifale. Cependant, les oursins empêchent également, par leur broutage, le recouvrement des coraux par les algues favorisées par l’AO. Dès lors l’effet de l’élévation de la pCO2 sur les oursins et leur capacité bioérosive peut être déterminant pour l'avenir des récifs coralliens tropicaux au cours du siècle, particulièrement ceux où la densité de ces bioérodeurs est importante. Une telle prédiction est d’autant plus complexe si l’on prend en compte la possible acclimatation des différents acteurs à long terme.

Dès lors, le but du présent travail fut d'évaluer l'effet à long terme de l’élévation de la pCO2 prévue en 2100 sur la physiologie et l’activité érosive d’un oursin clé de certains récifs coralliens, Echinometra mathaei, dans un dispositif artificiel reproduisant l’écosystème corallien.

La première étape a été la mise en place un outil expérimental permettant de maintenir à long terme un écosystème de récifs coralliens simplifié en condition contrôle et au pH prévu en 2100 tout en maintenant les autres paramètres physico-chimiques identiques et proches du milieu naturel (y compris dans leurs variations journalières). Le système mis en place est composé de scléractiniaires hermatypiques comme constructeurs de récif, d’oursins (E. mathaei) comme bioérodeurs et brouteurs et un substrat calcaire de récif avec ses communautés d’algues, bactéries, archae, champignons et méiofaune. Les variations journalières de pH et de température reproduisent celles mesurées in situ dans le site de La Saline, Ile de La Réunion, d’où proviennent une partie des organismes. Le pH moyen des aquariums contrôles a été maintenu avec succès à une moyenne de 8,09 ± 0,04, celui des aquariums à pCO2 élevée à 7,63 ± 0,02. L’alcalinité totale du système a pu être maintenue entre 2350 et 2450 µmol.kg-1.

L’impact de l’AO prévue en 2100 (pH 7,7) sur la physiologie d’E. mathaei été étudié à court terme (sept semaines). La principale source de nourriture des oursins fut la communauté algale se développant sur le substrat, comme en conditions naturelles. Cette étude a permis de mettre en évidence, à court terme, la capacité de résistance de cet oursin à une AO modérée. En effet, la croissance et le métabolisme ne furent pas affectés significativement. Ces observations ont été associées au maintien de la balance acide-base du fluide extracellulaire, le liquide cœlomique, par accumulation de bicarbonates dans celui-ci.

Une même expérience a ensuite été réalisée à long terme. La diminution du pH a été induite progressivement durant six mois jusqu'à atteindre un pH moyen de 7,65 qui fut ensuite maintenu à cette valeur pendant sept mois supplémentaires. La capacité de régulation de la balance acide-base du liquide cœlomique et la résistance d’E. mathaei à l’AO a été confirmée à long terme. Tant la croissance que le métabolisme et les propriétés mécaniques du squelette ne furent pas affectés. Cette résistance apparaît liée aux capacités de régulation acide-base d’E. mathaei, un trait apparemment d’origine génétique. Cette résistance pourrait également dépendre de la quantité et de la qualité de la nourriture disponible (calcaire ou non). Il est suggéré que les ions bicarbonates impliqués dans la régulation acide-base proviendraient en partie de la nourriture.

Parallèlement à ces mesures physiologiques, l’activité érosive d’E. mathaei a été mesurée. Les résultats indiquent que le taux de bioérosion triple en conditions acidifiées (pH 7,65). Cette augmentation serait liée à l’augmentation de l'activité de broutage des oursins et à la dissolution biologique du substrat, les propriétés mécaniques des dents des oursins et du squelette des coraux ne semblant pas affectés significativement. Nous suggérons que cette activité érosive accrue pourrait avoir un impact sur l'équilibre dynamique entre bioerosion et bioaccrétion des coraux et pourrait déterminer l'avenir des récifs coralliens où E. mathaei est le principal bioérodeur. Il faut toutefois noter que l’activité érosive de cet oursin est liée à une consommation accrue des macro-algues en compétition avec les coraux et algues corallines, favorisant ainsi ces derniers.

Les résultats obtenus, associés à ceux provenant de la littérature, indiquent que les changements globaux pourraient provoquer un changement profond des écosystèmes coralliens tropicaux. En effet, l’ensemble des bioérodeurs principaux étudiés jusqu’à présent semblent résistants aux changements climatiques globaux et montrent une augmentation de leur activité érosive. Dans le cas des récifs ayant déjà à l’heure actuelle une faible calcification nette, l’augmentation de la bioérosion pourrait mener à l’érosion nette et à la réduction puis à la disparition du récif. La prédiction du devenir des récifs coralliens tropicaux à l’échelle planétaire doit toutefois prendre en compte de nombreux paramètres :acclimatation, résistance/sensibilité et interactions des différents acteurs des récifs. D’autres études comparables à celles menées dans le présent travail devraient être mises en place afin de tester ces différents facteurs. Les données obtenues pourraient dès lors être utilisées dans la construction d’un modèle mécanistique permettant de mettre en place localement des mesures de conservation du récif, en complément de l’indispensable réduction massive de l’émission de CO2 atmosphérique à l’échelle mondiale.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

This study examined the effect of a growing environmental stressor, sedimentation, on the physiology and oxidative stress throughout the different life stages of two common scleractinian corals Montastraea cavernosa and Porites astreoides. Physiology, oxidative stress, and settlement success of newly released P. astreoides larvae were measured after exposure to various turbidity treatments. No significant effects were seen on larval settlement and photosynthetic efficiency, however carbonyl content and catalase activity were significantly higher in 2015 compared to 2014; highlighting a possible inter-annual variability in susceptibility. Larval settlement deterrence in the presence of a layer of accumulated fine- or coarse-grained sediment was examined and showed significant differences between treatments but not between sediment grain sizes. Ultimately showing that any sediment can deter settlement. The deleterious effects of sediment accumulation on the survival of newly settled spat was examined by smothering with varying layers of fine- or coarse- grained sediment. Survival was significantly different by treatment with coarse-grained sediment showing decreased survival with increasing accumulation. In adult P. astreoides fragments photosynthetic efficiency significantly decreased after being exposed to layers of accumulated sediment, with recovery monitoring after exposure revealing that over time photosynthetic efficiency did not recover to pre-exposure levels. However, in M. cavernosa the photosynthetic efficiency of fragments exposed to high sedimentation saw significant recovery after exposure. Significant differences among oxidative stress biomarkers (catalase activity and carbonyl content) were seen among exposed P. astreoides fragments, however no significance was seen in M. cavernosa. Tissue mortality was also assessed with P. astreoides fragments having significantly higher mortality compared to M. cavernosa. These results highlight the negative effects of sedimentation on scleractinian corals throughout their life history stages, increasing our need for a more thorough understanding of this growing environmental stressor.

Les coraux tropicaux constructeurs de récifs sont à l’origine d’écosystèmes extrêmement riches dont dépendent de nombreuses espèces, y compris l’Homme. Aujourd’hui, les changements climatiques représentent toutefois une menace pour la survie des coraux. Afin de comprendre la réponse de ces espèces aux modifications environnementales, il est essentiel d’avoir des informations sur la physiologie de ces espèces-clé. Les travaux conduits au cours de ma thèse ont ainsi permis de caractériser, au niveau mécanistique, les processus affectés par des changements de température chez l’espèce Stylophora pistillata. Pour cela, j’ai employé des approches multiples en partant de l’animal jusqu’au gène. Mes résultats ont montré : 1) que les taux de calcification, de photosynthèse et de respiration sont drastiquement réduits aux extrémités de la fenêtre thermique, 2) l’existence d’un phénomène de « light-enhanced calcification », excepté à basse température, 3) la sous-expression d’un groupe de gènes impliqué dans le transport du carbone inorganique lorsque les taux de calcification sont réduits (stress thermiques et la nuit), 4) la stabilité du pH dans le milieu extracellulaire calcifiant dans tous les traitements, et 5) l’augmentation de la perméabilité paracellulaire conjointement à l’augmentation de la calcification (25°C et le jour). En plus de leur intérêt en recherche fondamentale, ces informations peuvent constituer des outils utiles pour de futures recherches sur le terrain dans le but d’évaluer l’état de santé des coraux et prédire leur devenir dans un monde qui change
Tropical reef-building corals are at the basis of extremely biodiverse ecosystems on which many species depend, including human beings. Today, climate change represents a threat for the future survival of corals, and it is becoming crucial to better understand the physiology of these key species and the mechanisms underlying their responses to environmental change. The work conducted during my PhD focused on the characterization of the processes affected by temperature changes in Stylophora pistillata. For this purpose, I used multiple approaches from the animal to the gene. My results showed that: 1) calcification, photosynthesis and respiration declined drastically at the extremes of the thermal performance window, 2) light-enhanced calcification occurs across the thermal performance window except at low temperature, 3) a group of genes involved in inorganic carbon transport is under-expressed when calcification is reduced (thermal stress and during night), 4) pH in the extracellular calcifying medium remains stable at low and high temperatures, 5) paracellular permeability is highest when calcification increases (25°C and during the day). Information gained from this lab-based study will be useful in guiding further research in the field in order to evaluate coral health and predict the future of coral reefs in a changing world

Shallow-dwelling scleractinian corals live in high irradiance environments where they are exposed to large fluxes of ultraviolet radiation (UVR, 280 - 400 nm). A suite of UV-aborbing compounds, know as mycosporine-like amino acids, is found within the tissues of coral-algal symbioses and may perform a sun-screening role. The seasonal variation in MAA concentration was investigated for two corals in Kaneohe Bay, Hawai'i, Porites compressa and Montipora verrucosa. Regressions of MAA concentration and the amount of UVR measured prior to collection date were not significant for total MAA concentration of either species. However, individual MAAs, shinorine in P. compressa and palythene in M. verrucosa, did show significant correlation with UVR. The effects of UVR and water motion on Porites compressa were investigated in a flume and in the field. Exposure to ambient UVR was the most important factor tested in determining the concentration of MAAs in the tissues of P. compressa. Water motion also positively affected the concentration of MAAs, but only in the presence of UVR. When UVR was screened from the corals' environment, the tissue concentration of MAAs slowly decreased over time (approximately 2.5 to 5% per week) regardless of water motion. The effect of UVR on coral planulae was investigated in field experiments with Pocillopora damicornis. Larvae were taken from four different source adults: those from <0.5 m, those from 3 m, those incubated in the absence of UVR for two months, and those incubated in ambient UVR for two months. Deep larvae and larvae from adults incubated in the absence of UVR had roughly half the amount ofMAAs found in the shallow larvae and the larvae from adults in ambient UVR. Origin of larvae was not a significant factor in determining larval survival or recruitment success. UVR, however, was important in determining recruitment rate. Larvae were less likely to recruit to the settlement tile in the presence of ambient UVR than in treatments where the UVR was screened out.
Thesis (Ph. D.)--University of Hawaii at Manoa, 1999. Includes bibliographical references (leaves 151-164).

Human activities have substantially increased the atmospheric concentrations of greenhouse gases, resulting in warmer ocean temperatures that are having a negative impact on reef corals, which are highly susceptible to changes in temperature. Understanding the degree to which species vary in their tolerance to elevated temperatures and whether this variation is heritable is important in determining their ability to adapt to climate change. In order to address this, Acropora cervicornis fragments from 20 genetically distinct colonies were kept at either ambient or elevated temperatures, and mortality was monitored for 26 days. Heritability of thermal tolerance was estimated using a clonal method comparing the difference in lifespan within and among clones in a one-way ANOVA, as well as a marker based method using the program MARK (Ritland 1996) to estimate relatedness between colonies. To understand the physiological basis of thermal tolerance, tissue samples from both treatments were taken after 12 hours to investigate gene expression associated with sub-lethal temperature stress at both the mRNA and the protein level. The results revealed that this population of A. cervicornis has a relatively high amount of total genetic variation in thermal tolerance (H2 = 0.528), but low additive genetic variation for this trait (h2 = 0.032). In addition, both gene expression and protein expression among colonies were highly variable and did not show consistent patterns related to differences in thermal tolerance among colonies. These results reveal that this population of A. cervicornis may have a limited capacity to respond to projected increases in ocean temperatures. In addition, the results suggest that the molecular basis of thermal tolerance in this species is complex and that there are potentially many genotypic combinations that can result in a heat-tolerant phenotype.

L'association symbiotique entre les coraux scleractiniaires et les dinoflagelles (zooxanthelles) est a la base meme de l'existence des recifs coralliens, cependant les mecanismes physiologiques permettant la vie en symbiose de ces organismes sont mal connus. Le present travail a donc ete entrepris afin d'elucider certains de ces mecanismes. Pour cela, les zooxanthelles du scleractiniaire galaxea fascicularis ont ete etudiees hors de l'association symbiotique. Les zooxanthelles ont ete preparees de deux manieres differentes. La premiere, qui est l'isolation a partir des tissus de l'hote, produit des zooxanthelles fraichement isolees ou fiz, la seconde, qui consiste en la culture des dinoflagelles in vitro produit des zooxanthelles de culture ou cz. Lorsque les zooxanthelles sont isolees a partir des tissus de l'hote et transferees en eau de mer, la composition ionique du milieu exterieur change brutalement. En reponse a ce choc ionique, la concentration de sodium intracellulaire des fiz double durant la premiere demi-heure. Rapidement, des mecanismes de regulation se mettent en place, et la concentration de sodium revient a la valeur initiale. Les mecanismes grace auxquels les zooxanthelles absorbent le carbone inorganique utilise pour la photosynthese ont ete etudies. Les resultats semblent montrer que les cz absorbent le bicarbonate. Les fiz, en revanche, utiliseraient le gaz carbonique. Ces resultats mettent en evidence l'adaptation des deux types de zooxanthelles a leur environnement habituel: eau de mer ou cellule animale

Notre objectif est d’étudier les modalités d’accouchement au sein de la lignée humaine. Pour cela, nous utilisons deux approches complémentaires : la simulation numérique de l’accouchement et l’analyse discriminante des modalités d’accouchement au sein d’un échantillon obstétrical. Dans un premier temps, nous construisons des maillages de bassins et de crânes de foetus fossiles grâce à une méthode d’interpolation : le krigeage. Les groupes fossiles considérés sont les Australopithèques, les premiers représentants du genre Homo (PRGH) et les représentants du genre Homo au Pléistocène moyen et supérieur (RPMS). Les dimensions des crânes juvéniles sont utilisées pour estimer « à rebours » les dimensions néonatales à l’aide de courbes de croissance humaine et de chimpanzé. Nous réalisons une simulation numérique de l’accouchement à partir des maillages de ces dyades « virtuelles ». Puis nous réalisons des analyses discriminantes avec un jeu de données issu de mesures réalisées sur le pelviscanner de femmes et sur les mesures du crâne de leur nouveau-né afin de séparer les modalités d’accouchement grâce aux variables foeto-pelviennes. Ces mêmes variables foeto-pelviennes sont mesurées chez les dyades fossiles afin d’identifier, par les analyses discriminantes, leurs modalités d’accouchement les plus probables. Nos résultats suggèrent un accouchement eutocique sans rotation intra-pelvienne chez les Australopithèques, eutocique avec rotation intrapelvienne chez les PRGH, dystocique ou eutocique chez les RPMS, l’accouchement eutocique est caractérisé par une rotation et une incurvation de la trajectoire de descente
The purpose of this thesis is to estimate delivery outcomes for extinct hominids. We therefore use two complementary methods : numerical simulation of childbirth and discriminant analysis of delivery outcomes from an obstetrical sample. First, we use kriging to construct meshes of pelves and neonatal skulls. Fossil hominid specimens included in the study are Australopithecines, early Homo (EH) and middle to early Pleistocene Homo (MEPH). We estimate fetal cranial dimensions with chimpanzee or human cranial growth curve that we reversly use and apply on juveniles skull measurements. “Virtual” dyads are formed from pelves and neonatal skulls. Then, we simulate childbirth of these « virtual » dyads. Different levels of laxity of the sacro-iliac junction and different positions of the fetal head are considered. Finally, we use an obstetrical sample: delivery outcome is noted, CT-scans are used to obtain maternal pelvic measurements and diameters of the fetal head were also measured after delivery. A discriminant analysis is performed using this obstetrical sample to separate delivery outcomes thanks to fetal-pelvic measurements. Fossil dyads were subsequently added in the discriminant analysis to assess delivery outcomes to which they belong. Results suggest small fetal-pelvic constraint for Austalopithecines. This constraint is moderate for EH. Fetal-pelvic constraint is more important for MEPH. We suggest that rotational birth appears with EH. The curved trajectory of the fetal head appears with MEPH. Emergence of rotational birth and curved trajectory of fetal head are probably explained by two major increases in brain size during late and middle Pleistocene

Understanding the drivers of microbiome variation in corals is crucial to better predict the effects of environmental pressures on coral holobionts and coral reef ecosystems. However, much remains to be understood about corals and the interactions they establish with microorganisms. My hypothesis is that the microbiome of the surface mucus layer (SML) is mainly influenced by environmental parameters due to its direct contact with the environment, whereas the tissue microbiome is more driven by the physiology of the coral host. Therefore, the aim of the present work is to distinguish the effect of the host’s intrinsic and environmental factors on the microbiome composition in different coral compartments (SML and tissue), and to identify possible overarching trends in the environmental sensitivity of distinct microbiomes within a coral holobiont. Using next-generation amplicon-sequencing of the 16S rRNA gene, the analyses showed that microbiomes of Acropora spp. differed significantly between compartments (SML versus tissue) and species (A. tenuis versus A. millepora), but also among sampling location and season. Seawater samples were characterized by dominance of members of the Synechococcaceae and Pelagibacteraceae. In Acropora spp., mucus microbiome was dominated by members of Flavobacteriaceae, Synechococcaceae, Rhodobacteraceae and Pelagibacteraceae families, while the tissue microbiome was dominated by the Endozoicimonaceae family. SML microbiomes of both coral hosts correlated best with environmental parameters as ammonium, total suspended solids, particulate organic carbon, number of raindays and nitrate/nitrite. However, the amount of influence from environmental parameters on the mucus (explaining 12-15% of variation) is relatively low as compared with the influence of those parameters on the seawater microbiome (explaining 49% of variation). In contrast, the tissue microbiomes of the two Acropora species showed distinct and species-specific responses to environmental and physiological parameters, suggesting host-specific modulation of the environmental drivers of the tissue microbiome.
Os corais são considerados organismos holobiontes, uma unidade viva composta pelo hospedeiro e seu microbioma associado. Os corais, por exemplo, podem estar associados a eucariontes dinoflagelados (família Symbiodiniaceae), procariontes (Bacteria e Archaea) e/ou fungos. Os microrganismos associados aos corais estão envolvidos em diversas funções para o bom funcionamento dos processos fisiológicos do hospedeiro. Por exemplo, podem atuar como mediadores nos ciclos biogeoquímicos e na nutrição do hospedeiro, como também na defesa do mesmo contra agentes patogénicos. Portanto, são essenciais para a manutenção do estado saudável dos corais. Além disso, o microbioma dos corais está sob constante influência de flutuações dos fatores ambientais e fisiológicos dos seus hospedeiros. Compreender os fatores que influenciam a composição e funcionamento do microbioma é crucial para criar estratégias de conservação dos corais e, consequentemente, protegê-los dos efeitos das alterações globais, por exemplo. No entanto, ainda há muito a descobrir sobre a interação simbiótica em corais. O foco da presente tese é a comunidade de procariontes associados, que podem ser referenciados também como comunidades microbianas ou microbiomas ao longo da tese (conforme encontrado na literatura). As comunidades microbianas podem estar associadas a diferentes partes ou “compartimentos” do pólipo do coral. Os compartimentos incluem o muco superficial, tecido, esqueleto e a cavidade gástrovascular. Cada compartimento possui características únicas e, devido a isto, abriga microbiomas específicos, podendo variar tanto em abundância como em diversidade taxonómica. Por exemplo, estudos revelam que o microbioma do muco superficial de pólipos de corais é mais abundante e mais diverso que o tecido interno dos corais. A camada do muco apresenta-se como uma interface entre o epitélio dos pólipos e a coluna de água. Por isso põe-se a hipótese que a sua comunidade microbiana inclui não só os membros já residentes do muco, como também transientes originários de outras fontes (tais como a coluna de água, sedimentos em suspensão e/ou organismos bentónicos). Pelo contrário, as camada de tecido (epiderme e gastroderme) dos corais são dominadas principalmente por bactérias do género Endozoicomonas e também por microalgas fotossintéticas (da família Symbiodinaceae), extremamente importantes para a sobrevivência dos corais. Portanto, o estudo específico do microhabitat que o microbioma habita é crucial para o estudo geral de microbiomas de corais. No entanto, atualmente, estudos que englobam fatores que podem influenciar os microbiomas não se focam em diferentes compartimentos, mas apenas num só compartimento (geralmente o tecido). As primeiras descobertas neste tema mostraram que as comunidades microbianas específicas de corais são relativamente estáveis numa escala espacio-temporal. Estudos mais recentes propõem inúmeros fatores, para além da especificidade, que podem afetar a estrutura e a abundância relativa de membros dos microbiomas de corais. Por exemplo, diferenças geográficas, mudanças sazonais, poluição ou o estado fisiológico do hospedeiro. Porém, este tópico ainda é considerado bastante limitado e controverso, e mais estudos são necessários neste contexto.. O principal objetivo deste estudo é distinguir os efeitos de fatores ambientais e fisiológicos do hospedeiros na variação da composição das comunidades microbianas de diferentes compartimentos nos pólipos de corais (muco e tecido), e também, identificar possíveis tendências da sensibilidade ambiental dos microbiomas identificados. A minha hipótese é que o microbioma do muco é principalmente influenciado por parametros ambientais, devido ao seu contato mais direto com o ambiente, enquanto que o microbioma do tecido responde mais às mudanças fisiológicas do hospedeiro. Para testar esta hipótese, dados de Sequenciamento de Nova Geração (NGS) do gene 16S do RNA ribossomal dos microbiomas de diferentes compartimentos (muco e tecido) e espécies de coral (A. tenuis e A. millepora) foram usados em conjunto com dados de fatores ambientais e fisiológicos dos hospedeiros. O microbioma da coluna de água foi usado como referência no estudo. Em geral, os resultados mostraram que os microbiomas da Acropora diferiram significativamente entre os compartimentos e espécies, e também foram influenciados temporalmente e espacialmente. A riqueza de zOTU (“zero-radius OTU” ou unidade taxonómica operacional, a qual é designada como a menor entidade taxonómica existente) entre os microbiomas analisados diferiu significativamente entre o microbioma do muco, tecido e coluna de água, e também entre as espécies de Acropora. A riqueza de zOTU não diferiu entre estações ou local de coleta. O microbioma da coluna de água abrigou a comunidade mais rica, seguido da do muco e da comunidade do tecido. A diversidade alfa baseada no índex de Shannon também diferiu significativamente entre os microbiomas do muco, tecido e coluna de água, porém não diferiu entre espécies de corais, estação e local de coleta. A diversidade de zOTU foi significativamente maior no microbioma do muco em relação ao microbioma da coluna de água, enquanto que o microbioma do tecido foi o menos diverso entre todos. As amostras da coluna de água foram caracterizadas pela dominância de membros de Synechococcaceae e Pelagibacteraceae. Membros pertencentes às famílias Flavobacteriaceae, Synechococcaceae, Rhodobacteraceae e Pelagibacteraceae foram dominantes no microbioma do muco das espécies de Acropora, e membros da família Endozoicimonaceae foram dominantes no microbioma do tecidos de ambas as espécies. Os microbiomas do muco de ambas espécies de Acropora apresentaram maior influência de parâmetros ambientais como amónia, sólidos suspensos totais, carbono orgânico particulado, número de dias chuvosos e nitritos/nitratos. No entanto, a quantidade de influência dos parâmetros ambientais no muco (explicando 12-15% da variação) é relativamente baixa em comparação com a influência desses parametros no microbioma da água do mar (explicando 49% da variação). Por outro lado, os microbiomas do tecido apresentaram respostas distintas entre as espécies de Acropora nos parâmetros ambientais e fisiológicos, sugerindo modulação específica do hospedeiro aos fatores ambientais do microbioma do tecido. Em conclusão, o presente estudo revela que microbiomas presentes em compartimentos fisicamente distintos respondem diferentemente a fatores ambientais e fisiológicos, o que é uma novidade para os estudos de microbiomas de corais e sua dinâmica. Portanto, este estudo esclarece parte do conhecimento limitado e controverso neste contexto, e também estimula o uso de abordagens metodológicas mais holísticas sobre o tema. Sugestões para estudos futuros podem incluir o uso de outras espécies, diferentes das usadas no presente trabalho, e também testes experimentais (não só baseado em correlações) para o fornecimento de uma compreensão mais ampla da variação de microbiomas em corais.

碩士
國立中山大學
海洋科學系研究所
102
The price and demand on corals in ornamental industry are rising in recent years. Among various factors, color and growth rate are the most important two to determine the business profit. This study was aimed to investigate the effects of additional fed on the physiology and color of the stony coral, Acropora muricata. The experiments were conducted in the Marine Life Propagation Station, Penghu. Treatments were divided into 5 groups, i.e. control (starved), fed with Isochrysis galbana, Artemia salina, Isochrysis galbana + Artemia salina and Briachionus rotundiformis. Coral growth was measured by buoyant weighting method and morphology change was analyzed by photograph and Image J every other week. Camera settings were ISO-200, 1/30 second exposure time, exposure bias +1, iris aperture f/3.3, no flash and AWS white balance mode. Physiological parameters were only determined at week 0 and 8. Phosphate concentration (7.84 ± 1.10 μM PO43-) was significantly higher than normal seawater during the experimental period. Coral weight increased in the range of 80 - 100% and no difference among treatments. In contrast, the RGB values decreased with lighter color in the group of fed with B. rotundiformis. All other groups had darker colors when compared with week 0. In addition, measurements on physiological parameters, i.e. zooxanthellae density, total protein and chlorophyll a content showed no significant difference among treatments. The result of lighter color when fed with B. rotundiformis may have application potential in ornamental industry of corals.

碩士
國立中山大學
海洋生物研究所
93
The present study was undertaken to determine the effects of varying light intensities on the morphology and physiology of the soft coral Pachyclavularia violacea. The soft corals P. violacea were treated by LED light and the illumination ranged from 50 to 200 μmol photon m-2 s-1, i.e. high light (200 μmol photon m-2 s-1), medium light (140 μmol photon m-2 s-1), medium-low light (100 μmol photon m-2 s-1 and low light (50 μmol photon m-2 s-1). The theca length, the density of zooxanthellae and the concentrations of chlorophyll a and proteins were measured to evaluate the response of P. violacea to different light intensities. A significant longer theca length was found in the group of medium-low light (5– 9mm) than the groups of high and low light intensities (1-2mm) (p<0.001). And, the theca length in the groups of medium and medium-low was more close to their source population. Over the 6-month experimental periods, the densities of zooxanthellae in the groups of medium and medium-low were in the range of 1.5 ~3.8 x 105 (N/mg) which were significantly higher than other groups (p<0.01). The concentrations of chlorophyll a in the low light group were 0.5~ 2.0 (ng/mg) during the experimental periods which were significantly higher than other groups (p<0.05). In the fifth and sixth months, the concentrations of chlorophyll a per zooxanthellae in the group of medium-low were in the range of 0.4~5.8 Chl. a × 10-5 (ng/zoox.) which were significantly higher than other groups (p<0.01). The protein content in the group of low light was significantly lower than other groups in the fifth month. And, the protein contents were decreased significantly in all groups in the sixth month. Based on the results, it is concluded that theca length and the density of zooxanthellae were sensitive responses to light adaptation. The light intensity about 100 μmol photon m-2 s-1 might be an appropriate range to culture the soft coral P. violacea because the theca length in the group was close to its source population.

碩士
國立東華大學
海洋生物研究所
107
As the oceans were continuously threatened by anthropogenic pollutions and climate change, coral breeding has become the preferred conservation method to prevent exposure to suboptimal environment conditions which could be detrimental to their rehabilitation. However, it is also a concern that sexual reproduction capability of the ex-situ coral would be affected in the artificial environment. The aim of the study was to observe and compare the ultrastructure of the wild Oxypora lacera and E. gemmacea oocytes and their respective in-vivo cultured counterpart using transmission electron microscope (TEM). TEM analyses of O. lacera showed oocytes collected from the wild were larger (389.32 ± 21.32 µM) than the cultured oocytes (302 ± 13.75) but the microvilli of the wild O. lacera oocytes were shorter (2.21 ± 0.21 µM) than those found on cultured oocytes (3.02 ± 0.68 µM). Similar differences were also found observed in the E. gemmacea whereby oocyte from the wild were larger (268.91 ± 10.02 µM) than the cultured (207.25 ± 16.72 µM) but the microvilli in the wild is shorter (1.18 ± 0.22 µM) than the cultured oocytes (1.93 ± 0.14 µM). Internally, yolk body and lipid granules in the wild oocytes of O. lacera (31.87 ± 6.92 and 16.64 ± 3.81 µM respectively) and E. gemmacea (1.16 ± 0.31 and 7.21 ± 0.89 µM respectively) were smaller than the yolk body and lipid granules of cultured oocytes O. lacera (33.99 ± 3.10 µM and 23.05 ± 3.02 µM respectively) and E. gemmacea (1.28 ± 0.61 and 8.88 ± 0.51 µM respectively). In addition, yolk materials abundance in the both species oocyte were also lower in the wild (O. lacera - 55.4 %; E. gemmacea - 50.1%) compared to the cultured oocytes (O. lacera - 81.2 %; E. gemmacea - 74.5%). Although it is evident that culture environment is the main factor for these differences, the actual reason for these changes were still unknown. However, it was suggested that nutrient availability played a significant role in determining formation of lipid body and yolk granules. The present ultrastructure study would facilitate future works on coral breeding for conservation purpose.

As simbioses entre espécies representam adaptações face a mudanças ambientais no meio marinho. Uma das simbioses mais carismáticas é o mutualismo entre peixes limpadores e os seus clientes. Estes ocupam territórios específicos conhecidos como “estações de limpeza” e prestam um serviço aos seus clientes, comendo ectoparasitas e tecidos mortos. Para interagir com os seus clientes os bodiões limpadores (Labroides dimidiatus) desenvolveram um conjunto de ferramentas cognitivas e comportamentais. No entanto, as condições em que estas simbioses evoluíram estão a mudar devido ao aquecimento e à acidificação dos oceanos. Esta dissertação tem como objetivo compreender como as simbioses de limpeza respondem ao aquecimento e à acidificação dos oceanos (AAO), utilizando uma abordagem integrativa. Mais especificamente, esta dissertação centrou-se em duas questões principais: 1) “O comportamento cooperativo de limpeza é afetado por AAO? Quais são os mecanismos neurobiológicos e há potencial para adaptação? ” e 2)“ Os parasitas são resistentes a AAO? Como estes afetam os peixes e como a sua abundância pode ser controlada? ”. Nos capítulos 2 e 3, é revelado que AAO pode afetar o comportamento de limpeza através de disrupção dos sistemas neurobiológicos. Por outro lado, o Capítulo 4 demonstra que o desempenho cognitivo do peixe limpador, embora afetado pela acidificação, ainda apresenta potencial de adaptação. Em relação à segunda questão, o capítulo 5 revela que os ectoparasitas são tolerantes à acidificação. No capítulo 6, apenas clientes sem acesso a serviços de limpeza foram fisiologicamente afetados pela acidificação. Por fim, o capítulo 7 mostra que os corais controlam a abundância de parasitas e a perda de corais devido a eventos extremos pode diminuir a predação de parasitas. Em conclusão, esta dissertação mostra que o AAO podem perturbar as simbioses da limpeza através de alterações comportamentais causadas por perturbações neurobiológicas. Embora exista algum potencial de adaptação, a combinação destes stressores climáticos e a imprevisibilidade de eventos extremos tornam a probabilidade de adaptação menor. Por último, é importante frisar que esta disrupção de simbioses da limpeza pode levar a efeitos de cascata nos ecossistemas dos recifes de coral, uma vez que a necessidade de peixes nos serviços de limpeza pode aumentar com uma maior abundância de ectoparasitas gnatídeos tolerantes a CO2 (devido à diminuição no controlo da abundância).
Symbiotic relationships reveal interesting adaptations to deal with challenging marine environments. One of the most charismatic symbiosis is the mutualism between cleaner fishes and their clients. In this case, small fishes occupy specific territories, known as “cleaning stations” and provide a service to their clients, eating ectoparasites and dead tissue. To engage in cleaning interactions, cleaner wrasses (Labroides dimidiatus) evolved a set of cognitive and behavioural tools. Yet, the ecological conditions where cleaning symbiosis evolved are changing due to humaninduced environmental stressors, such as ocean warming and ocean acidification. The present dissertation aimed to understand, within a multidisciplinary and integrative approach, how cleaning symbiosis respond to ocean warming and acidification (OWA). More specifically, this dissertation centred around two major research questions: 1) “Is cooperative cleaning behavior affected by OWA? If so, what are the neurobiological mechanisms and is there potential for adaptation?” 2) “Are parasites resilient to OWA? If so, how they impact client fishes and how their abundance can be controlled?”. In Chapter 2 and 3, I show that both OWA can affect cleaning behaviour through the disruption of dopaminergic, serotoninergic and GABAergic systems. Yet, in Chapter 4, cleaner wrasse cognitive performance, although impacted by OA, presented a certain potential for adaptation through directional selection. Regarding the second question, Chapter 5 reveals that ectoparasites are tolerant to OA, while Chapter 6 shows that only clients without access to cleaning services were physiologically affected by OA. Lastly, Chapter 7 shows that corals control gnathiids abundance and loss of coral cover from extreme events, such as mass bleaching, can decrease by 80% the predation on gnathiids. In conclusion, this dissertation shows that OWA can disturb cleaning symbiosis through behavioural changes mediated by neurobiological changes. Although there is some potential for adaptation, the combination of these climatic stressors and the unpredictability of extreme events renders the probability of adaptation. Finally, it is important to note that this disruption can lead to cascade effects on coral reef ecosystems, since the need for cleaning services can increase with a greater abundance of CO2-tolerant gnathiid ectoparasites (due to decreased abundance control).
Company of Biologists (JEB 170212 - 2017)
The Lizard Island Reef Research Foundation

Dissertação de Mestrado em Ecologia, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.
Coral reefs are some of the most sensitive ecosystems to environmental change. With massive declines reported since the 1980s, there are many concerns that they could disappear due to human activities. The most common stress response in corals is bleaching, the breakdown of the symbiosis, which leaves the coral without their main energy source: their symbiotic algae. Without enough energy, corals cannot afford to invest in reef accretion, which creates the basic habitat for reef ecosystems. Differential bleaching severity and mortality has been largely documented, with high temperatures being the main stress. During bleaching, some corals switch symbiont types to a more thermo-tolerant clade, although this might present a metabolic cost. Thermo-tolerant symbionts have been reported as opportunistic generalists, suboptimal to most coral species. A way to assess coral fitness is through the monitoring of physiological parameters such as the lipid content. In this study, lipid content was analyzed in coral tissue samples from Montastrea annularis and Montastrea faveolata collected seasonally in the years 2000-2002 following the 1997-98 El Niño catastrophic bleaching in the Florida Keys. Seasonal variation was observed in most samples. Recovery was visible but slowed down after 2001, and the probable causes for that are discussed. Lipid content was significantly correlated to physiological parameters related to the symbiotic algae, confirming zooxanthellae’s role in the supply of lipids to the coral. M. annularis presented about half the lipids per unit surface, and we suggest that this is due to the many different types of Symbiodinium it contained in contrast to M. faveolata which presented only one type.

碩士
國立臺灣大學
海洋研究所
94
The purpose of this study is to understand the effect of culturing environment on physiology of reef corals. The experiment cultured separately three kinds of corals which included Acropora intermedia, Stylophora pistillata and Seriatopora hystrix in mesocosms (with sand, rocks, corals, invertebrates and fish inside) and tanks(only seawater inside). After a period of culturing, the photosynthesis and growth rate of coral nubbins could be measured and compared to emerge the difference of the two culturing environments. The result shows that the data of Acropora intermedia cultured in mesocosms which include the maximum quantum yield of photosystem II (Fv/Fm), chlorophyll a concentration, zooxanthellae density and chlorophyll a concentration per zooxanthellae were higher than the data which were measured in the culturing environment of tanks. For Stylophora pistillata, the data of Fv/Fm, chlorophyll a concentration and zooxanthellae density were higher in mesocosms as well. In addition, the growth rates of three coral nubbins were varied in the same culturing environment but the growth rates of corals in the culturing environment of mesocosms were still higher or equal to the date in tanks. The difference between each of the physical parameter in two culturing environments emerged by time. Finally, using mesocosm to culture reef corals is effective in maintaining the growth rate, and the photosynthetic parameters are higher in the culturing environment of mesocosms. Therefore, the conclusion could be inferred that mesocosm is much suitable for the long period experiment, and tank is just applicable to short period experiment.

The dinoflagellate genus Symbiodinium is a popular research topic in the coral reef molecular biology field. Primarily because these organisms serve as the coral holobiont’s primary source of energy, carrying out photosynthesis, and providing hydrocarbons to the coral host. Previous studies have shown the difficulty of isolating Symbiodinium as well as the inherent problems in trying to quantify the diversity of this genus and to qualify the distinct reactions of different Symbiodinium sp. to changing environmental conditions. The main goals of this study are: (1) to detail the relationship between the genetic classification of the organism and its physiology in regard to photosynthesis with a number of established Symbiodinium cultures; and (2) to isolate Symbiodinium from coral of the central Red Sea. To evaluate the photosynthetic physiology of Symbiodinium, a microsensor was used to measure oxygen concentrations along with a phytoplankton analyzer system that used pulse-amplitude-modulation (Phyto-PAM) to measure fluorescence. In order to identify the particular clade that the isolates belonged to, denaturing gradient gel electrophoresis (PCR-DGGE) was used to identify Symbiodinium based on their internal transcribed spacer 2 (ITS2) region. These techniques helped us to achieve our goals in the following ways: Symbiodinium sp. from a culture collection were classified to the subclade level; species-specific and clade-specific photosynthetic profiles were generated; and a Symbiodinium sp. was isolated from the central Red Sea. This study provided preliminary correlation between the photosynthetic difference and Symbiodinium genetic classification; showed the probable existence of a self-protection system inside the Symbiodinium cells by comparing the difference between the initial oxygen production at the beginning of each light step and the oxygen production after light adaptation; and confirmed the possibility of the isolation of Symbiodinium.