Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2016-10-18T18:36:37Z No. of bitstreams: 1 2015 - Ivan Pierozzi Junior.pdf: 92591526 bytes, checksum: b6f151111ef71de5cd89f7d46f910fff (MD5) / Made available in DSpace on 2016-10-18T18:36:37Z (GMT). No. of bitstreams: 1 2015 - Ivan Pierozzi Junior.pdf: 92591526 bytes, checksum: b6f151111ef71de5cd89f7d46f910fff (MD5) Previous issue date: 2015-11-27 / CAPES / Rhodolith bed has aroused growing interest of the scientific community, not being different to the Fernando de Noronha Archipelago (FNA). FNA rhodolith banks occur at depths of 10 to 100m and are peculiar habitat that increases structural complexity, providing increased associated diversity compared to unconsolidated substrates. The interaction between rhodoliths and sponges is the focus of this study. On the banks of AFN sponges play an important role in the stabilization mechanism of rhodoliths, accounting for coalescing neighbour nodules, which may point to an early stage of an on going process of stabilization in the form of a consolidated reef. The presence of reef-building corals in the adjacent rocky shore can also be related to the rhodolith banks as polyp?s skeletons were found nucleating rhodoliths. This study identified which organisms were agglutinating rhodolith nodules at Cabe?o da Sapata (45m deep) and if is there any relationship between physical characteristics of the bank and the occurrence of agglutinated complex. It was also described the physical structure and the frequency of occurrence of agglutinated rhodolith. Sponges was the main group of sessile fauna found coalescing rhodoliths and this process points to a relationship between size of the nodules and the variation in size between the nodes. The importance of sponges to the rhodoliths beds and potentially to the process of consolidated reefs formation is reinforced by this study. / Os bancos de rodolitos tem despertado interesse cada vez maior da comunidade cient?fica, n?o sendo diferente para o Arquip?lago de Fernando de Noronha (AFN). No AFN os bancos de rodolitos ocorrem em profundidades de 10 a 100m e s?o habitat peculiares que aumentam a complexidade estrutural, propiciando um aumento da diversidade associada quando comparados com substratos n?o consolidados. A intera??o entre os rodolitos e por?feros ? o foco desse estudo. Nos bancos do AFN as esponjas desempenham um importante papel no mecanismo de estabiliza??o dos rodolitos, sendo respons?veis por aglutinar n?dulos pr?ximos, o que pode apontar para um estagio inicial de um processo permanente de estabiliza??o, na forma de um recife consolidado. A presen?a de recifes coral?neos no cost?o rochoso adjacente tamb?m podem ter rela??o com os bancos de rodolitos j? que esqueletos de p?lipos foram encontrados nucleando rodolitos. Neste estudo foram identificados quais organismos foram respons?veis pela aglutina??o de n?dulos do banco de rodolitos do Cabe?o da Sapata (45m de profundidade) e se existe rela??o entre caracter?sticas f?sicas do banco e a ocorr?ncia de aglutinados. Tamb?m foi descrita a estrutura f?sica e a frequ?ncia de ocorr?ncia de aglutinados de rodolitos. Por?fero foi o principal grupo da fauna s?ssil encontrado aglutinando rodolitos e esse processo aponta para uma rela??o entre tamanho dos n?dulos e a varia??o de tamanho entre os n?dulos. A import?ncia das esponjas nos bancos de rodolitos, e potencialmente no processo de forma??o de recifes consolidados, ? refor?ada pelo presente estudo,

Coral reefs on Florida’s Reef Tract (FRT) are susceptible to many anthropogenic influences including controlled freshwater discharges and agricultural runoff as well as high natural environmental variability from seasonal rainfall, runoff and upwelling. To better understand coral population structure and responses to sublethal stressors, populations of the scleractinian coral Montastraea cavernosa in the northern FRT were examined using a combination of genomic and transcriptomic techniques. Microsatellite genetic markers identified high local retention among sites and a slight southward gene flow. An in-situ temporal gene expression analysis utilizing a tag-based sequencing transcriptomic approach was used to analyze baseline coral health at St. Lucie Reef (SLR), off Stuart, FL. Temporal variation had the greatest influence of differential gene expression among M. cavernosa at SLR. Results will be shared with local resource managers and coupled with a complementary ex-situ experimental trial. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Les coraux Scléractiniaires se développent généralement dans la zone photique peu profonde, exposée au rayonnement ultraviolet (UVs), la composante la plus dangereuse du rayonnement solaire. Le rayonnement UVs augmente avec le réchauffement climatique et s’ajoute à l’ensemble des pressions auxquelles sont soumis les coraux. Les enjeux de cette thèse ont été 1) de mieux comprendre les effets des UVs sur la réponse physiologique des coraux, les flux de matière organique et les bactéries associées au mucus et au corail; et 2) de caractériser l’effet combiné des UVs et d’une augmentation de température, et/ou d’un changement de disponibilité en sels nutritifs. Les résultats obtenus montrent tout d’abord que l’exposition des coraux aux UVs amplifie l’effet négatif de la température sur leur physiologie. Il en est de même pour l’absence en sels nutritifs, essentiels pour la physiologie corallienne. Nos résultats indiquent également que la sensibilité des coraux à un stress UV dépend de l’espèce étudiée et de la densité de symbiontes présents dans les tissus. L’effet négatif des UVs augmente avec la densité de symbiontes, vraisemblablement dû à la formation d’espèces réactives de l’oxygène (ROS) qui provoquent des dommages à l’organisme. Dans cette thèse, nous avons montré que la voie de signalisation JNK (c-Jun N-terminal kinase), hautement conservée au sein des êtres vivants, est impliquée dans la gestion de ces espèces réactives et que son inhibition entraine un blanchissement très rapide des coraux sous UVs et forte température. Finalement, l’excrétion de matière organique ainsi que les bactéries associées sont également impactés par les UVs ce qui pourrait contribuer à d’importants changements biochimiques dans l’eau des récifs coralliens. Les travaux de cette thèse apportent de nouvelles connaissances sur les effets des UVs sur les coraux et soulignent l’importance de les prendre en considération lors de nos prédictions sur le devenir des récifs coralliens face au réchauffement climatique. / Scleractinian corals mainly grow in the shallow euphotic zone, exposed to ultraviolet radiation (UVR), the most harmful part of the solar radiation. UVR increases with climate change and adds to the different environmental pressures that corals are facing. The aims of this thesis were to 1) better understand the effects of UVR on coral physiology, organic matter fluxes and associated bacteria; 2) assess the combined effects of UVR and thermal stress and/or nutrient level. Results show that UVR worsens the negative effect of temperature on coral physiology, similarly to nutrient depletion. Our results also indicate that the sensitivity to UVR stress (i.e. an increase in UVR) is species dependent and function of the symbiont density. The negative effects of UVR increase with the number of symbionts, likely due to the formation of reactive oxygen species (ROS) which cause cellular damages. In the thesis, we showed that the JNK signalling pathway (c-Jun N-terminal kinase), highly conserved in living organisms, is involved in the early response of corals to UVR and its activation is required to repress stress-induced ROS accumulation. Finally, organic matter release and mucus and coral-associated bacteria are also significantly impacted by UVR, which could contribute to important biochemical changes in reef waters. The work conducted in this thesis brings new insights into the effects of UVR on corals and highlights the importance of taking this environmental factor into account when predicting the future of coral reefs under climate change.

Le passage entre les étages géologiques du Pliensbachien et du Toarcien au Jurassique inférieur est suivi au Toarcien inférieur par un évènement anoxique d’importance planétaire (TOAE pour Toarcian Oceanic Anoxic Event). Dans les archives de l’histoire de la terre, ce moment correspond en bien des endroits à un temps de fossilisation massive de matière organique donnant ici où là des roches mères d’intérêt pétrolier. Si, en termes de fluctuation du niveau eustatique, ces évènements sont souvent situés dans une zone d’inondation maximale de 2ème ordre, ils sont aussi interprétés comme une perturbation globale du cycle du carbone avec acidification des océans, liée à la mise en place des provinces ignées du Karroo-Ferrar en Afrique du Sud et en Amérique du Sud, contrées jointives à ce moment-là. Il s’agit d’une période de réchauffement global faisant suite à une période particulièrement froide au Pliensbachien. Cette perturbation écologique globale a certainement affecté la biosphère dans une mesure qui reste aujourd’hui très mal connue. Nous connaissons des études par exemple sur des ammonites ou des bivalves dont la définition stratigraphique permet rarement de distinguer l’impact du passage de la limite entre les deux étages du passage au Toarcien inférieur de la TOAE et la seule étude disponible sur les coraux est une étude purement bibliographique (Lathuilière et Marchal 2009) qui laisse supposer une extinction significative sur la même période. Les coraux sont très généralement des marqueurs particulièrement précieux des perturbations écologiques majeures comme on peut le voir pour les cinq grandes extinctions et même pour la sixième extinction en cours. Cette extinction au Pliensbachien-Toarcien pour l’instant considérée de second ordre mérite donc d’être analysée de ce point de vue. Dans le cadre de cette thèse, des collectes de coraux ont été effectuées sur le terrain au Maroc et en Italie dans un contexte sédimentologique défini de part et d’autre de la limite Pliensbachien - Toarcien. Les prélèvements ont été réalisés de façon à pouvoir évaluer la diversité ainsi que, dans la mesure du possible, la variabilité intraspécifique. Le traitement statistique des données a été réalisé dans le souci d’assurer une bonne connaissance de la variabilité pour fournir une taxinomie fiable dans l’optique de comparer des populations comparables en termes d’analyse de la diversité, des extinctions et des apparitions de taxons. Au total, 107 espèces ont été décrites (dont au moins 19 nouvelles espèces) réparties parmi 60 genres (dont 5 nouveaux) dans au moins 22 familles (dont 1 nouvelle). Cette étude nous révèle pour les eaux froides et chargées en matière organique du Pliensbachien des assemblages de coraux présentant une grande part d’affinité avec les faunes du Trias (en termes de genres et familles). Ils partagent une partie de leurs niches écologiques sur les plateformes internes de l’ouest téthysien avec des bivalves constructeurs de récifs connaissant alors un succès évolutif fulgurant : les lithiotidés. Les données récoltées témoignent de conditions ayant contraint les coraux à s’adapter et à se diversifier pour se maintenir lors de cette période peu propice, au profit des formes solitaires et phacéloïdes et au détriment des formes de plus hauts niveaux d’intégration. Au Toarcien inférieur, le réchauffement global des eaux couplé à la disparition quasi-totale des concurrents des coraux a permis une explosion de diversité déterminante pour l’avenir de ce groupe avec la mise en place de faunes d’assemblages très similaires à celles du Jurassique moyen et supérieur (en terme de genres, familles et morphologies coloniales). Il s’agit d’un évènement d’extinction biphasé dont la première phase se produit au passage entre Pliensbachien et Toarcien, la seconde phase correspondant au passage du TOAE. L’évènement pris dans son ensemble amène à l’extinction de près de 97% des espèces de coraux présentes au Pliensbachien / The transition from the Pliensbachian to the Toarcian geological stages in Lower Jurassic is followed by a global oceanic anoxic event during the lower Toarcian (TOAE for Toarcian Oceanic Anoxic Event). This moment corresponds to a massive fossilization time for organic matter in the worldwide geological record that produced here and there source rocks of petroleum interest. Concerning the eustatic fluctuations, these events are associated to a second-order maximal flooding zone. They are also interpreted as the remains of a global carbon-cycle perturbation case associated with oceanic acidification and correlated with the setup of Karoo-Ferrar igneous provinces in the southern Pangea territories corresponding to present-day Southern Africa and Southern America. It corresponds to a period of global warming that directly follow a global cooling at the Pliensbachian. This worldwide ecological perturbation probably disturbed the biosphere in a degree that is still poorly quantified. For example, studies about ammonites and bivalvs are known but the stratigraphic definition generally do not allow to distinguish the Pliensbachian-Toarcian boundary itself to the TOAE effect on these fauna. One single available study about corals is purely bibliographic (Lathuiliere and Marchal 2009) and suggests a significant extinction event for this group at the same period. Corals are generally precious indicators for major ecological disruptions as it is testified in the case of the big-five major crisis and the current sixth one. The Pliensbachian-Toarcian extinction has been considered up-to-now as a second-order crisis event and require to be studied as such. In the context of this thesis, fossilized corals have been collected in the field in Morocco and Italy in a well-defined sedimentological context before and after the Pliensbachian-Toarcian boundary. Sampling has been in view to quantify the diversity and as far as possible, the intraspecific variability. The statistical treatment of the data has been realized in view to provide a satisfying quantification of the variability in order to supply a strong taxonomy and be able to compare comparable populations in analyses of diversity, extinctions and apparitions of taxons. In total, 107 species have been describes (including at least 19 new species) as part of 60 genera (including 5 new ones) among 22 families (including a new one). According to this study, the cold and highly concentrated in organic matter oceanic waters of the Pliensbachian contained corals faunas with an important affinity with Triassic faunas (in terms of genera and families). They shared the ecological niches of the western tethysian inner platforms with the lithiotids, a group of aberrants reefal bivalvs that demonstrated a stupendous evolutive success during the same period. Collected data attest of conditions that constrained corals to adapt and diversify in view to maintain during these unfavourable times, for the benefit of the solitary and phaceloid form but at the expense of the highly integrated forms. During the Lower Toarcian, global warming of oceanic waters associated with the almost total disparition of the competitors premised an explosion of diversity that is determinant for the future of the corals, with the apparition of faunal assemblages very similar to the typical Middle and Upper Jurassic ones (in terms of genera, families and colonial morphologies). It is a two-folded extinction event with a first phase during the Pliensbachian –Toarcian transition and a second phase at the onset of the TOAE. In the end, this pulsed event led to the extinction of approximately 97% of the Pliensbachian coral species

Modern anthropogenic forcing of atmospheric chemistry poses the question of how the Earth System will respond as thousands of gigatons of greenhouse gas are rapidly added to the atmosphere. A similar, albeit nonanthropogenic, situation occurred during the early Paleogene, when catastrophic release of carbon to the atmosphere triggered abrupt increase in global temperatures. The best documented of these events is the Paleocene-Eocene Thermal Maximum (PETM, ~55 Ma) when the magnitude of carbon addition to the oceans and atmosphere was similar to those expected for the future. This event initiated global warming, changes in hydrological cycles, biotic extinction and migrations. A recently proposed hypothesis concerning changes in marine ecosystems suggests that this global warming strongly influenced the shallow-water biosphere, triggering extinctions and turnover in the Larger Foraminifera (LF) community and the demise of corals. The successions from the Adriatic Carbonate Platform (SW Slovenia) represent an ideal location to test the hypothesis of a possible causal link between the PETM and evolution of shallow-water organisms because they record continuous sedimentation from the Late Paleocene to the Early Eocene and are characterized by a rich biota, especially LF, fundamental for detailed biostratigraphic studies. In order to reconstruct paleoenvironmental conditions during deposition, I focused on sedimentological analysis and paleoecological study of benthic assemblages. During the Late Paleocene-earliest Eocene, sedimentation occurred on a shallow-water carbonate ramp system characterized by enhanced nutrient levels. LF represent the common constituent of the benthic assemblages that thrived in this setting throughout the Late Paleocene to the Early Eocene. With detailed biostratigraphic and chemostratigraphic analyses documenting the most complete record to date available for the PETM event in a shallow-water marine environment, I correlated chemostratigraphically for the first time the evolution of LF with the δ¹³C curves. This correlation demonstrated that no major turnover in the LF communities occurred synchronous with the PETM; thus the evolution of LF was mainly controlled by endogenous biotic forces. The study of Late Thanetian metric-sized microbialite-coral mounds which developed in the middle part of the ramp, documented the first Cenozoic occurrence of microbially-cemented mounds. The development of these mounds, with temporary dominance of microbial communities over corals, suggest environmentally-triggered “phase shifts” related to frequent fluctuations of nutrient/turbidity levels during recurrent wet phases which preceding the extreme greenhouse conditions of the PETM. The paleoecological study of the coral community in the microbialites-coral mounds, the study of corals from Early Eocene platform from SW France, and a critical, extensive literature research of Late Paleocene – Early Eocene coral occurrences from the Tethys, the Atlantic, the Caribbean realms suggested that these corals types, even if not forming extensive reefs, are common in the biofacies as small isolated colonies, piles of rubble or small patch-reefs. These corals might have developed ‘alternative’ life strategies to cope with harsh conditions (high/fluctuating nutrients/turbidity, extreme temperatures, perturbation of aragonite saturation state) during the greenhouse times of the early Paleogene, representing a good fossil analogue to modern corals thriving close to their thresholds for survival. These results demonstrate the complexity of the biological responses to extreme conditions, not only in terms of temperature but also nutrient supply, physical disturbance and their temporal variability and oscillating character. / Die anthropogene Beeinflussung der Chemie der Atmosphäre in der modernen Zeit wirft die Frage nach dem Schicksal des Systems Erde auf, wenn tausende von Tonnen an Treibhausgasen in kurzer Zeit in die Atmosphäre einströmen. Im Känozoikum trat bereits eine ähnliche Situation während des frühen Paläogens auf, als eine katastrophale Freisetzung von Kohlenstoff in die Atmosphäre einen plötzlichen Anstieg der globalen Temperatur hervorrief. Das am besten dokumentierte dieser Ereignisse stellt das Paläozän-Eozäne Temperatur Maximum (PETM, ~55 Ma) dar, bei welchem die Größenordnung der Kohlenstoffzufuhr in Ozeanen und Atmosphäre jener ähnelte, die in der Zukunft zu erwarten ist. Das damalige Ereignis initiierte eine globale Erwärmung, Veränderungen hydrologischer Kreisläufe, biotische Auslöschung und Abwanderungen. Eine kürzlich veröffentlichte Hypothese zu Veränderungen in marinen Ökosystemen postuliert, dass diese globale Erwärmung die Biosphäre der Flachwässer stark beeinflusste, indem sie Aussterben und Fluktuation innerhalb der Gemeinschaft der Großforaminiferen (GF) sowie den Niedergang einiger Korallen bewirkte. Die Abfolgen der Adriatischen Karbonatplattform (SW-Slovenien) stellen einen idealen Ort dar, um die Hypothese des kausalen Zusammenhangs zwischen dem PETM und der Evolution der Flachwasserorganismen zu überprüfen, da sie aufgrund ihrer kontinuierlichen Sedimentation vom Spätpaläozän bis zum Früheozän und ihres Reichtums an Biota, insbesondere an GF, fundamentale Voraussetzungen für eine detaillierte biostratigraphische Studie erfüllen. Um die Paläoumweltbedingungen während der Sedimentablagerung zu rekonstruieren, wurde der Schwerpunkt dieser Arbeit auf eine sedimentologische Analyse und eine paäoökologische Studie benthischer Vergesellschaftungen gesetzt. Während dem Spätpaläozan bis zum frühesten Eozän fand die Sedimentation auf einem Flachwasser-Rampensystem statt, welches durch ein erhöhtes Nährstoffangebot gekennzeichnet war. GF stellen jenen häufigen und verbreiteten Bestandteil der benthischen Vergesellschaftungen dar, welcher in dieser Umgebung durch das Spätpaläozän hindurch bis ins Früheozän gedeihen konnte. Mit den in dieser Arbeit vorgestellten detaillierten bio- und chemostratigraphischen Analysen, deren Dokumentation den zur Zeit vollständigsten Datensatz für das PETM-Ereignis in einem flachmarinen Milieu repräsentieren, wurde die Evolution der GF zum ersten Mal mit δ¹³C -Kurven chemostratigraphisch korreliert. Diese Korrelation zeigte, dass in den GF-Gemeinschaften keine großmaßstäbliche Fluktuation zeitgleich mit dem PETM auftrat, und dass daher die Evolution der GF hauptsächlich durch endogene biotische Einflüsse kontrolliert worden sein muss. Die Studie mikrobiell-überkrustete Korallenhügel im Größenbereich zwischen einigen Metern und einigen Zehnermetern, die sich im Spätthanetium im mittleren Teil der Rampe entwickelten, dokumentiert das erste Auftreten mikrobiell-zementierter Erhebungen während des Känozoikums. Die Entwicklung dieser Erhebungen, mit einer zeitweiligen Dominanz der mikrobiellen Gemeinschaften gegenüber den Korallen, spricht für ein Auftreten Umwelt-gesteuerter "Phasenverschiebungen" im Zusammenhang mit häufigen Wechseln von Nahrungsangebot und Trübung während wiederkehrender nasser Phasen, welche dem extremen Treibhaus der PETM vorausgingen. Die paläoökologische Studie der Korallen-Gemeinschaften in den mikrobiell-überkrusteten Korallenhügeln, die Studie der Korallen der früheozänen Plattform in SW-Frankreich sowie eine kritische, ausgedehnte Literaturrecherche zum Auftreten spätpaläozäner bis früheozäner Korallen in der Tethys, im Atlantik und in der Karibik sprechen dafür, dass diese Korallentypen – selbst wenn sie nicht ausgedehnte Riffe formen – in der Biofazies häufig als kleine isolierte Kolonien, Berge von Geröll oder kleine Kuppelriffe auftreten. Diese Korallen könnten 'alternative' Überlebensstrategien entwickelt haben, um mit den rauen Bedingungen (hohes/wechselndes Nahrungsangebot, schwache/starke Trübung, schwankende Temperaturen, häufige physikalische Störungen) fertig zu werden, die während den Zeiten des paläogenen Treibhauses vorherrschten, und stellen damit ein gutes fossiles Analog zu modernen Korallen dar, welche nahe an ihrer Überlebensgrenze gedeihen. Diese Ergebnisse zeigen die Komplexität der biologischen Reaktionen auf extreme Bedingungen, nicht nur im Hinblick auf Temperaturen, sondern auch hinsichtlich Nahrungsangebot, physikalische Beeinträchtigungen sowie deren zeitliche Schwankungen und deren oszillierenden Charakter.

Coral diseases have become more prevalent and destructive over the past 20 years, possibly due to an increase in stressful environmental factors that may weaken corals defenses against disease. Aspergillosis is a disease caused by the fungus Aspergillus sydowii, which apparently infects only two species of gorgonian corals in the Caribbean Ocean (Gorgonia ventalina and G. flabellum). We hypothesized that the differential resistance to infection is caused by differences in chemical defenses among gorgonians. Freeze-dried gorgonian powders and extracts deterred fungal growth, but potencies varied among gorgonian species and among fungi. Extracts and powders generated from G. ventalina all strongly inhibited fungal growth. Since G. ventalina was predicted to have weak antifungal chemical defenses compared to gorgonians not known to suffer from aspergillosis, we concluded that gorgonian susceptibility to fungal infection is determined by factors other than, or in addition to, chemical defenses. In order to investigate specific gorgonian antifungal strategies, we attempted to use bioassay-guided fractionation to isolate antifungal compounds from four gorgonians: Gorgonia ventalina, Briareum asbestinum, Eunicea succinea, and Pseudopterogorgia americana. We succeeded in isolating two antifungal compounds, diastereomers of 9,11-seco-24-hydroxydinosterol, from the gorgonian Pseudopterogorgia americana. This compound was previously identified by other groups, but this study is the first to establish its antifungal activity. At natural concentration, one diastereomer of 9,11-seco-24-hydroxydinosterol inhibited the growth of three different fungi, suggesting that at least this diastereomer may possess broad-spectrum antifungal activity. The results from our survey of gorgonian chemical defenses indicate that susceptibility to aspergillosis cannot be explained by chemical growth inhibition alone. Further areas of investigation include induction of gorgonian chemical defenses, examination of growth-inhibiting mechanisms of antifungal metabolites, and identification of non-chemical factors affecting gorgonians vulnerability to fungal infection.

Title from PDF of title page. / Document formatted into pages; contains 93 pages / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Coral-based climate studies commonly use elemental ratios and stable isotopes of coral skeletons to address seawater temperature and hydrologic balance issues in the tropical surface oceans. Replication, or cross-checking, a standard technique used to assess the fidelity of proxy records in paleoclimatology has not been widely applied in coral-based climate studies, primarily because of the time and cost associated with generating multiple records from a single reef site. Modern and paleoclimate reconstructions based on a single proxy-coral record from a site may contain errors if individual corals from the same reef record different geochemical signals. In this study we perform a replication test using elemental ratios and stable isotopes in three Porites corals from New Caledonia. / ABSTRACT: The reef complex offshore Amédée Island, New Caledonia is an ideal site to perform a coral replication test because instrumental sea surface temperatures (SST) and sea surface salinity measurements (SSS) have been made there for over 25 years. In this study, we compare sub-monthly resolved, geochemical variations (Sr/Ca, d18O and d13C) in three Porites lutea coral heads, located 500 m apart, with the instrumental SST and SSS records over the interval 1992-1967. The monthly coral Sr/Ca and d18O time series are well correlated to each other (r=0.86, p[.0001) and to the monthly instrumental SST record (r= -0.86, p[.0001, coral Sr/Ca to SST; r= -0.77, p[.0001, coral d18O to SST). The three, sub-monthly resolved, 30-year coral Sr/Ca-SST time series have mean SST values that agree within 0.2oC with the instrumental mean SST value. A similar comparison for the coral d18O-SST records indicate a maximum difference between predicted and observed mean SST of 0.5°C. / ABSTRACT: Analysis of the monthly climatological means also indicates that Sr/Ca-SST records closely match the instrumental SST record ±0.4°C; a similar comparison using the d18O-SST record yields an average offset of ±0.6°C between observed and predicted monthly SST. Stacking the three records to form composite Sr/Ca-SST and d18O-SST records does not appreciably improve the goodness of fit between the proxy and instrumental SST records; hence a coral-based proxy climate record from a single coral accurately reflects the observed record of climate variability at this locality. These results support the concept that high fidelity climate records can be generated using a single coral core. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Mar. 11, 2010). Includes bibliographical references.

The El Niño-Southern Oscillation (ENSO) dominates global interannual climate variability. However, the imprint of anthropogenic climate change hinders understanding of natural ENSO variability. Model predictions of the response of future ENSO variability to anthropogenic forcing are highly uncertain. A better understanding of how ENSO operates during different mean climate states may improve predictions of its future behavior. This study develops a technique to quantify the response of tropical Pacific sea surface temperature and salinity to ENSO variations. This analysis defines expected regional relationships between ENSO forcing and the tropical Pacific climate response. For example, the western tropical Pacific records El Niño events with greater skill than La Niña events; whereas the oceans near the South Pacific Convergence Zone (SPCZ) preferentially record La Niña events. This baseline understanding of regional skill calibrates interpretations of both modern and pre-instrumental coral geochemical climate proxy records. A suite of monthly resolved 18O variations in a fossil corals (Porites spp.) from the tropical western Pacific (Papua New Guinea) and the SPCZ (Vanuatu) are used to develop case studies of ENSO variability under external forcing conditions that differ from the modern climate. A record from Misima, Papua New Guinea (1411-1644 CE) spans a period of reduced solar forcing that coincides with the initiation of the Little Ice Age. This record indicates that the surface ocean in this region experienced a small change in hydrologic balance with no change in temperature, extended periods of quiescence in El Niño activity, reduced mean El Niño event amplitudes, and fewer large amplitude El Niño events relative to signals captured in regional modern records. Several multidecadal (~30-50 year) coral records from Tasmaloum, Vanuatu during the Medieval Climate Anomaly (~900-1300 CE), a period of increased solar forcing, depict ENSO variability that is generally lower than modern times. However, these records often cannot be distinguished from 20th century ENSO variability due to ENSO variability uncertainty associated with record lengths. Neither record can be tied to concurrent changes in solar or volcanic forcing, calling into question the paradigm of ENSO variability being predominantly mediated by external forcing changes on multidecadal time scales. / text

Global warming from anthropogenic greenhouse gas emissions causes temperature increases in aquatic ecosystems. The rise in environmental temperatures places sensitive organisms under thermal stress. Reef-building corals are a critically important group of animals that provide many ecosystem services for coral reef ecology and the economy and are at a high risk of loss from thermal stress. Thermal stress causes corals to lose their colour, i.e. become bleached, resulting from the loss of symbiont zooxanthellae. This diminishes the energetic benefits that zooxanthellae provide to corals leading to a decline in coral health and high mortality rates. However, corals are also predators and can thus draw nutrients from zooplankton prey to supplement their nutritional requirements. This study investigated whether heterotrophic feeding can ameliorate the effects of thermal stress on coral physiology by providing an alternative energy source to zooxanthellar photosynthesis. Fragmented Pocillopora damicornis coral colonies were exposed to daily maximum temperatures of up to 31°C while being either starved or fed. During the experimental period coral nubbins were monitored for changes in polyp extension, oxygen consumption rate, feeding rate, colour, chlorophyll a content, zooxanthellae density, antioxidant potentials and DNA integrity during stress and after a short recovery period. It was found that, as expected, coral polyp extension, oxygen consumption rate, colour health, chlorophyll a content, zooxanthellae density and DNA integrity were all adversely affected by thermal stress. This indicted that all these measurements were viable biomarkers for assessing the negative effects of thermal stress on coral health. Coral colour, oxygen consumption rate, chlorophyll a content, lipid content, antioxidant potential and DNA integrity were all significantly improved by feeding. These results indicate that feeding does play a role in improving overall coral health and supports the physiological processes in coral tissue during and after thermal stress. The conclusions from this study also have great significance for coral reef ecology and management as predictions of reef resilience can be made from zooplankton ecology and boosting zooplankton availability to corals may be considered to mitigate the harmful effects of thermal stress and bleaching. / M.Sc. University of KwaZulu-Natal, Durban 2013.