Reproductive biology, population genetics and ecology of three sea anemone species in U. K. populations were described by examination of fresh and histological preparations, starch gel electrophoresis, and mapping techniques. Sagartia troglodytes is shown to consist of two distinct species, corresponding to the recognised varieties decorata (now S. troglodytes) and ornata (renamed Sagartia ornata - Holdsworth 1855). S. troglodytes employs obligately out-crossinoviparous gonochoric reproduction. Populations have maximal genotypic diversity, good fits to single-locus Hardy-Weinberg (H-W) predictions and high levels of gene flow between populations. S. ornata broods asexually produced actinulae. Populations are highly clonal. Extreme deviations from out-crossing predictions and extensive differentiation between populations suggest no gene flow occurs. S. ornata has a chromosome number double that of the other three species. S. ornata is concluded to be a parthenogenetic polyploid "morphospecies". Sagartia elegans employs a mixed reproductive strategy, combining local asexual propagation by pedal laceration with out-crossing oviparous gonochoric sexual reproduction. Local, short term recruitment is mainly by asexual expansion of established clones. Genotypic diversity in most populations is high despite the occurrence of large localised clones. Most populations exhibit deviations from H-W predictions, and significant differentiation between populations at all variable loci confirms the lack of short term success of sexual reproduction and gene flow. Cereus pedunculatus displays genetic differentiation between colour pattern "morphs", but this may result from a predominance of asexual propagation and sub-habitat differentiation between clones. Populations consist of females and simultaneous hermaphrodites, both of which brood parthenogenetically produced actinulae. Sexually produced young may also be brooded. All populations display deviations from H-W predictions, and extensive inter-population differentiation. The populations studied are concluded to be marginal in the species range, a move away from sexual reproduction resulting in genetic isolation of populations and consequent drift and founder effects. All four species display high levels of genetic variability. No association of genetic variability with clonal success, degree of habitat heterogeneity, environmental conditions or life-history characteristics is apparent.

No description available.

Light is often the most abundant resource within the nutrient poor waters surrounding coral reefs. Consequently, both photoacclimation and photoadaptation of the host and Symbiodinium play a crucial role in ensuring coral success. This thesis systematically examined responses (phenotypic and genotypic) of hermatypic corals across environmental gradients by 1) characterising variability between different isolated Symbiodinhim types under different light regimes, 2) examining the role of the host in photoacclimation using laboratory and in situ transplant experiments, and 3) assessing photoacclimation and photoadaptation strategies in four key coral species across habitats to determine key drivers of coral distribution.

No description available.

No description available.

<i>Lophelia pertusa</i> is the world’s most common and widespread framework-forming cold-water coral. It forms deep-water coral reefs and carbonate mounts supporting diverse animal communities on the continental shelf and on seamounts. Cold-water corals are found throughout most of the world’s oceans at depths of around 200 to 1000 meters. Unlike their tropical counterparts, cold-water corals do not contain symbiotic algae. These recently discovered ecosystems have been damaged by deep-sea fishing and are threatened by climate change. Despite this, very little is known about the ecophysiology of <i>L. pertusa</i> and its likely response to environmental changes. The aims of this research were to investigate the physiology of <i>L. pertusa</i> and relate this to its environment. In particular, this research focused on the respiratory physiology, growth and lipid signature of <i>L. pertusa</i>. This is the first study to investigate the physiology of <i>L. pertusa</i> and relate it to aspects of its natural environment, including temperature and oxygen availability. Results suggest that <i>L. pertusa</i> has slow physiological rates that vary geographically and may be dependent on food sources. Lipid analysis suggested a strong link to surface production and preferential feeding on copepods. It appears that <i>L. pertusa</i> is sensitive to small temperature changes and is at least partially limited in distribution by oxygen levels. This environment is likely to be threatened by changes in seawater temperature, ocean acidification, alteration of food webs and water masses as well as destructive fishing impacts. The results of this research provide vital information that will underpin future research and allow us to predict the effects of anthropogenic impacts on <i>L. pertusa.</i>

This study examined the occurrence of Lophelia pertusa on North Sea oil infrastructure and its environmental sensitivity to oil and gas activities. Underwater videos from industry platform surveys were examined to identify L. pertusa, detail its occurrence at two sites (Heather and North Alwyn A (NAA)), and to look for evidence of exposure to drilling muds and cuttings (discharges). In addition, live corals were exposed to 4-h sedimentation events of increasing rates and polyp behaviour analysed. Sediment removal mechanisms were also examined. Finally, skeletal characteristics and trace metal concentrations were measured in skeletons sampled from platform sites exposed to drilling discharges and control sites. The results showed a newly established sub-population of L. pertusa in the northern North Sea. L. pertusa was identified on 14 platforms and 947 colonies were recorded on Heather and NAA between 59 to 132 m depth coinciding with the presence of year round Atlantic water. Original recruits were likely from the northeast Atlantic and are now annually self-recruiting to the platforms. Additional video from Tern in 1993, 1994, 1998, and 2002 provided the first in situ colony growth rate (26 ± 5 mm yr-1) for L. pertusa. Visual evidence of contamination from drilling discharges was limited to colonies close to drilling discharge points where partial and complete colonies were dead. Polyp behaviour was negatively affected only at the highest sedimentation rates (12-19 mg cm-2 min-1), which are likely to be significantly higher than in situ rates, and polyps cleared sediment with ciliary currents and ingestion, which may be an indiscriminate feeding response. Corals exposed to discharges had shorter and narrower corallites compared to controls but other causal factors merit consideration such as genetics and hydrography. Further results showed that polyps bud annually and reach their maximum height in their first year, while the theca thickens at a constant rate, thus implying that the innermost growth band likely represents the first year of growth. Relatively depleted δ13C and δ18O along the inner growth band, which indicates fast calcification, supported this result. Copper and barium in coral skeletons including visible detrital inclusions were significantly higher in exposed versus control colonies. Chromium and barium along the growth axis, avoiding detrital inclusions, showed one exposed polyp from a colony living two meters above the cuttings pile on North West Hutton (NWH) with higher barium compared to control colonies. Short-lived barium spikes were observed in two polyps from a control colony sampled from North Cormorant. It is hypothesised that the NWH coral may have been exposed to dissolved barium released during cuttings resuspension, while barium spikes in the control colony may result from natural fluctuations in seawater barium, thus advocating that L. pertusa can act as an archive of the marine environment.

Coral reefs are immensely vulnerable to climate change and particularly the effects of ocean warming; in efforts to understand whether and how reef systems will survive into the future, research is increasingly focusing on present day populations acclimatized to thrive under relatively extreme conditions. Whilst corals thrive along a range of environmental conditions, including relative extremes, within the Red Sea, these coral populations are still considered not well explored of the genetic and physiological signatures throughout this system. Corals microbiota communities (the “microbiome”) are recognized as a major component as to how corals “acclimatize” to different environmental conditions; therefore, this work aimed to investigate the historical thermal variability along the Red Sea and subsequently identify the relative role of coral microbiome associated with differences in coral thermal tolerance. Remotely sensed data (1982-2012) demonstrated migration of Sea Surface Temperature anomalies (i.e. DHW) from the south to the north during this time frame. Analysis of historical bleaching records indicated that coral populations were more tolerant to bleaching in the northern compared to the central/southern Red Sea. Symbiodinium clade type (ITS2) and microbial community (16S rRNA metagenomics) associated with six key coral species persisting across five sites of the northern Red Sea (29°-20°N) were then examined. Symbiodinium clade identity associated with each coral species generally remained highly conserved throughout the sites sampled. In contrast, microbial communities were variable within and between species across the Red Sea sites. Corals from two sites (central-Jeddah and northern-Hurghada) were exposed to a thermal stress experiment which confirmed that corals were more heat resistant at Hurghada (summer SST mean is 3.3 °C less) than Jeddah; however, symbiont ITS2 clade types were the same at both sites. Conversely, microbial community changed in heat stressed samples at Jeddah compared to the control group, while it remained stable at Hurghada. This work provides for the first time genetic analysis on corals’ microbiome inhabiting extreme thermal resistant region (i.e. the northern Red Sea) that contradict the global bleaching pattern. Our findings suggest that plasticity of microbial community may play the key role in acclimation of corals experience thermal anomalies in the Red Sea suggesting presence certain microbial phylotypes fill specific thermal niche. Finally, the higher latitudes of the Red Sea will broadly serve as a potential corals refugia which highlights the importance to conserve and implement a regional management policy to improve corals thermal tolerance of this region to be used as a genetic reservoir.

Les habitats de coraux d’eau froide formés par des scléractiniaires coloniaux, des gorgones, des antipathaires et des pennatules sont des hotspots de biodiversité et de biomasse. Ils fournissent des fonctions importantes, comme des refuges et des zones d’alimentation, pour d’autres organismes. Mais, ils sont également vulnérables aux activités humaines, parce qu’ils sont fragiles, croissent lentement et atteignent des records de longévité. Dans les canyons sous-marins, le relief tourmenté, l’hydrodynamisme et l’hétérogénéité des substrats offrent des conditions environnementales propices au développement des habitats coralliens. Dans le Golfe de Gascogne, les coraux d’eau froide sont connus depuis la fin du 19e siècle, mais leur distribution, leur densité et leur rôle fonctionnel avaient été très peu étudiés.Pour augmenter cette connaissance, 24 canyons sous-marins et 3 sites sur l’interfluve/haut de pente contiguë aux canyons adjacents ont été visités par un ROV et une caméra tractée pendant 46 plongées au cours de 7 campagnes océanographiques. Les habitats coralliens définis par le système de classification CoralFISH ont été cartographiés à partir des images prises par les engins sous-marins puis la faune associée, les types de substrat et les déchets ont été annotés.Onze habitats coralliens et 62 morphotypes de coraux ont été observés dans les canyons sous-marins du Golfe de Gascogne hébergeant 191 morphotypes de faune associée, dont 160 morphotypes uniques. Les patrons de distribution à l’échelle locale et à l’échelle régionale pourraient être liés aux régimes hydrodynamiques et sédimentaires. Le type de substrat était important pour les assemblages de coraux et leurs faunes associées, distinguant les habitats biogéniques, sur substrat dur et sur substrat meuble. Les assemblages de coraux étaient similaires entre habitats biogéniques et habitats sur substrat dur, mais la faune associées était plus abondante et diversifiée sur les habitats biogéniques. La diversité-alpha, -beta et –gamma étaient étonnement élevée sur les habitats coralliens sur substrat meuble, égalant ou dépassant la diversité des habitats biogéniques.Les déchets marins étaient abondants et principalement composés de plastiques et de matériels de pêche. Ces déchets pourraient impacter les habitats coralliens : ils ont été trouvés à des profondeurs similaires et les déchets étaient piégés par des reliefs créés par des structures biologiques et géologiques. L’ocurrence des récifs de coraux préférentiellement sur les pentes plus abruptes des canyons sous-marins tandis que les débris de coraux sont plus fréquents sur des aires plus plates de l’interfluve ou du haut de pente, pourraient indiquer un impact de la pêche.Cette étude a contribué à l’initiative en cours de création d’un réseau Natura 2000 qui protégera à terme l’habitat « récif » dont les habitats coralliens biogéniques et sur substrat dur, mais pas les habitats coralliens sur substrat meuble. Pour ces derniers, un complément d’étude et d’autres stratégies de préservation seront nécessaires. / Cold-water coral (CWC) habitats formed by colonial scleractinians, gorgonians, antipatharians and sea pens are biodiversity and biomass hotspots that provide important functions, such as shelter and feeding grounds, to other organisms. But, they are also vulnerable to human activities, because they are long-lived, grow slowly and have a low resistance. Submarine canyons may offer the environmental conditions needed for CWC habitat development, due to their steep topography, complex hydrodynamics and substrate heterogeneity. In the Bay of Biscay, which margin is incised by hundreds of canyons, CWCs are known to exist since the late 19th century, but their distribution, density and functional role remained largely unknown, which impaired their preservation.To increase this knowledge, 24 canyons and three locations between adjacent canyons were visited with an ROV and a towed camera system during 46 dives on 7 cruises. Images were analysed for CWC habitats using the CoralFISH classification system. Within these habitats, corals, associated fauna were identified and substrate cover measured. Litter was identified in 15 out of 24 canyons.Eleven coral habitats constructed by 62 coral morphotypes were observed in the canyons of the Bay of Biscay hosting 191 associated megafaunal morphotypes, including 160 unique morphotypes. The distribution patterns at regional and local scales could be linked to hydrodynamics and sedimentary regimes. Substrate type was an important driver for coral and associated faunal assemblages, distinguishing biogenic, hard substrate and soft substrate habitats. Coral assemblages were similar between biogenic and hard substrate habitats, but the associated fauna was more abundant and diverse on biogenic habitats. The alpha, beta and gamma diversity was surprisingly high on soft substrate habitats, equalling or exceeding that of biogenic habitats.Marine litter was abundant and was mainly composed of plastic items and fishing gear. Litter could co-occur with CWCs and impact them: litter and most CWC habitats were observed at similar water depths and litter was more abundant in areas with a seafloor relief created by biological or geological features. Observations of coral reefs on steeper areas in the canyons and coral debris on flatter areas on the interfluve/upper slope may indicate a potential impact of the fishing industry. This study supports the ongoing effort to create a Natura 2000 network that will protect biogenic and hard substrate habitats, but also points out the need to develop a framework for the preservation of coral habitats on soft substrate.