Physiology and ecology of Stylophora pistillata and Echinopora gemmacea from the Red Sea

1. Some aspects of the biology and nutritional physiology of the corals Stylophora pistillata and Echinopora gemmacea from the Red Sea are described in this thesis. The two species were selected on the basis of their differing growth form and nutritional strategies. The main objective was to compare their nutritional energy budgets and to examine the effects upon these of environmental factors associated with differing depths on the reef and with different seasons. 2 . S. pistillata is a branching coral, with small polyps. In shallow water (1m) the coral has compact club-shaped branches, whereas at 10m it has an open growth form with slender branches. E. gemmacea has large polyps, and both encrusting and lightly branching growth forms. It was not found at depths of less than 3m. 4 . Histological examination showed that the coenosarc of S. pistillata is characterised by holotrich nematocysts and mucus-gland cells containing neutral mucopolysaccharides. By contrast, the epidermis of E. gemmacea contains spirocysts and large numbers of mucus-gland cells secreting an acid mucopolysaccharide. The gastrodermis of the tentacles of S. pistillata, which are expanded during the day time are packed with zooxanthellae. In E. gemmacea the tentacles are withdrawn during the day and are devoid of zooxanthellae. In both species, lipid stores are concentrated in the gastrodermal layers only, mainly in the lower half of the polyps. 4 . Four types of nematocyst are present in both species : spirocysts, microbasic P-mastigophores, microbasic B-mastigophores and holotrichs. Spirocysts are most common on the oral discs and mainly at the tentacle tips. Microbasic P-mastigophores are more common in the tentacles of E. gemmacea suggesting a more important role for prey capture in this species. In both species the mesenterial filaments are armed with microbasic P-mastigophores and holotrichs, indicating that they are important for aggression and defence. 5 . S. pistillata displays a weak ability to deal with particulate food when presented as Artemia nauplii or eggs. There is an extensive development of ciliary currents on the outers epidermis, but these appear to be used only for cleansing of the outer surface. E. gemmacea expands its tentacles at night and feeds on particulate organic matters trapped on the surface mucus net. Large particles, including fish faecal pellets, may be ingested. The expansion of the tentacles of S. pistillata during the day time suggests a nutritional economy which is more dependent upon the symbiotic zooxanthellae. 6 . Both species are hermaphrodite with protogynous gametogenesis. S. pistillata has an extended breeding cycle. Oogenesis began in May, whilst spermatogenesis was first detected in August. Fertilisation takes place in the coelenteron and the first planulae were observed in December. E. gemmacea has a short annual cycle of gametogenesis. Oogenesis was first observed in June and spermatogenesis in August. Broadcast-spawning occurred in November. 7 . The distribution of the two species on a shallow fringing reef in Sharm Ubhur, a small creek to the north of Jeddah, is described from a transect survey. At the study site, the lowest mean water temperature of 25.

Spatio-Temporal Analyses of Symbiodinium Physiology of the Coral Pocillopora verrucosa along Large-Scale Nutrient and Temperature Gradients in the Red Sea

Algal symbionts (zooxanthellae, genus Symbiodinium) of scleractinian corals respond strongly to temperature, nutrient and light changes. These factors vary greatly along the north-south gradient in the Red Sea and include conditions, which are outside of those typically considered optimal for coral growth. Nevertheless, coral communities thrive throughout the Red Sea, suggesting that zooxanthellae have successfully acclimatized or adapted to the harsh conditions they experience particularly in the south (high temperatures and high nutrient supply). As such, the Red Sea is a region, which may help to better understand how zooxanthellae and their coral hosts successfully acclimatize or adapt to environmental change (e.g. increased temperatures and localized eutrophication). To gain further insight into the physiology of coral symbionts in the Red Sea, we examined the abundance of dominant Symbiodinium types associated with the coral Pocillopora verrucosa, and measured Symbiodinium physiological characteristics (i.e. photosynthetic processes, cell density, pigmentation, and protein composition) along the latitudinal gradient of the Red Sea in summer and winter. Despite the strong environmental gradients from north to south, our results demonstrate that Symbiodinium microadriaticum (type A1) was the predominant species in P. verrucosa along the latitudinal gradient. Furthermore, measured physiological characteristics were found to vary more with prevailing seasonal environmental conditions than with region-specific differences, although the measured environmental parameters displayed much higher spatial than temporal variability. We conclude that our findings might present the result of long-term acclimatization or adaptation of S. microadriaticum to regionally specific conditions within the Red Sea. Of additional note, high nutrients in the South correlated with high zooxanthellae density indicating a compensation for a temperature-driven loss of photosynthetic performance, which may prove promising for the resilience of these corals under increase of temperature increase and eutrophication

Long-chain aliphatic wax esters isolated from the sponge Chalinula saudensis (Demospongia) along the Jeddah coast of the Red Sea

A esponja Chalinula saudensis ocorre ao longo da costa de Jeddah, Arabia Saudita, mas apenas recentemente foi isolada e identificada. No presente estudo a matéria orgânica total da esponja foi extraída por solventes e o extrato foi separado por partição sucessiva através do emprego de hexano e água, clorofórmio e água e finalmente t-butanol e água. A camada contendo clorofórmio foi então separada por cromatografia em sílica. Os resultados mostraram a presença de ésteres de quatro ácidos graxos de cadeira longa (C28H56O2, C30H60O2, C32H62O2 e C36H70O2), sendo que o segundo deles foi também identificado nos corais Millepora dichotoma e Millepora platyphylla. Não se tem evidência da presença dos demais compostos em outros organismos marinhos, embora haja relatos para ésteres semelhantes de cadeia longa, mas contendo diferentes cadeias alifáticas e diferentes pesos moleculares. Os compostos isolados em C. saudensis são geralmente ceras e sua presença na esponja tem importância não só nas rotas de biosíntese, mas servem como isolantes nas variações sazonais adversas.The sponge Chalinula saudensis, which occurs along the Jeddah coast, has only recently been isolated and identified. In this study, the total crude organic matter of the sponge was extracted by solvents. The total crude extract was further separated by partitioning it with hexane and water, then with water and chloroform, and finally with water and t-butanol. The chloroform layer was subjected to separation by preparative layer chromatography on silica. One fraction contained four long-chain fatty acid esters, C28H56O2, C30H60O2, C32H62O2 and C36H70 O2. The second ester, C30H60O2, has been identified in the fire corals Millepora dichotoma and Millepora platyphylla. The others have not previously been reported from marine organisms; however similar long-chain esters with different long aliphatic chains and with different molecular weights have been identified from other marine organisms. These compounds are normally waxy and their presence in Chalinula saudensis plays a vital role in the biosynthetic pathways. They also act as insulators against seasonal variations

Biology of Red Sea Corals: Metabolism, Reproduction, Acclimatization, and Adaptation

Coral reefs are the most abundant shallow water ecosystems in the Red Sea, harboring a high species diversity and habitat complexity over large environmental gradients. At the same time the semi-enclosed ocean basin and its partly extreme environmental conditions may promote species evolution being distinct from Indo-Pacific coral reefs. Extreme conditions are found in the southern Red Sea, where temperatures reach up to 33 °C in summer and where nutrient input is high. Mechanisms of organism adjustment to these conditions are of particular interest in the light of climate change research. Towards the north, conditions become more ‘coral-promoting’ finally reaching temperatures between 21–27 °C (winter-summer) and clear waters at the northern end of the Red Sea (Gulf of Aqaba). In this chapter, we summarize the current knowledge about the biology of shallow water, symbiotic, reef-building corals of the Red Sea. We start with an overview on the environmental conditions of the Red Sea, the history of coral reef research in this region and a general introduction into coral biology, before we describe the ecophysiology of Red Sea corals. Coral ecophysiology is presented in the context of varying environmental conditions over depth (e.g., light), between seasons, and over latitudes (e.g., light, temperature, nutrients). Mechanisms and patterns of coral reproduction are discussed in the context of seasonal and latitudinal environmental changes. Finally, we briefly describe anthropogenic influences on Red Sea coral reefs. Acclimatization mechanisms of corals to changing conditions over a depth gradient (mainly light reduction) have been well studied in the Gulf of Aqaba and include the following metabolic adjustments with depth: (i) an upregulation of light-harvesting pigments (chlorophyll a) and a downregulation of photo-protective pigments (xanthophyll), (ii) an increase of heterotrophy, and (iii) a decrease of metabolic activity (e.g., calcification and growth). In addition, a change in the symbiont composition (Symbiodinium clade and/or type) over depth was observed in some coral species. Seasonal environmental changes (mainly light availability, temperature, nutrients) lead to various metabolic responses of the corals, including (i) changes in zooxanthellae pigmentation and density and (ii) changes in the metabolic activity. In particular, changes in calcification and growth rates can be observed with lowest rates during low temperatures in winter. Interestingly, however, this reverses in the southern Red Sea, where calcification rates are higher in winter than in summer. This kind of latitudinal shift is also evident in the timing of reproduction, which occurs earlier in the year (January–March) in the south compared to the north (March–August). This indicates that growth and reproduction are strongly linked to temperature, following a single temperature optimum, which occurs at different times throughout the year from north to south. Furthermore, this hints towards a high phenotypic plasticity (acclimatization) rather than local genetic adaptation of the investigated coral species. A clear shift in the genetic population structure from north to south in another coral species, however, indicates local adaption. Adjusting mechanisms need to be further understood in order to provide indication for predicted climate change effects

A comparative study of the components of the hard coral Seriatopora hystrix and the soft coral Xenia umbellata along the Jeddah coast, Saudi Arabia

In this study, the structure of the polyps and the cell types of the hard coral Seriatopora hystrix and the soft coral Xenia umbellata were compared, together with the composition of the fatty acids in their tissues. S. hystrix displayed an apparent lack of specialized feeding cells, notably the relatively small number of mucous gland cells and the low percentage of venom containing nematocysts. P-mastigophores accounted for 1.52-5.7% and, Bmastigophores for 1.28% of the nematocysts. Conversely there was a high percentage of holotrichs nematocysts (24.86 - 55.5%) in the tentacles and mesenterial filaments respectively. Zooxanthellae were abundant in the gastrodermis. These charateristics suggest that S. hystrix relies essentially upon autotrophic nutrition. The polyps of X. umbellata were devoid of cnidae, and mucous glands were in abundance, particularly in the lower part of the polyp. The presence of particulate matter in the coelenteron, and low number of zooxanthellae indicate that X. umbellata is a suspension feeder, using mucus to trap the particles on the pinnate tentacles. Differences were also revealed by a comparative study of their chemical composition. X. umbellata had a high protein and lipid content, whilst S. hystrix was characterized by high calcium carbonate content. In S. hystrix, the fatty acids were found to be predominantly saturated fatty acids (87.3%), the most abundant being 16:0 and 18:0. X. umbellata showed a predominance of unsaturated fatty acids (77.7%), the most abundant being 16:1 and 18:1. The differences in morphology and in biochemical composition suggest that S. hystrix has a greater reliance on autotrophic feeding whilst X. umbellata is a more heterotrophic suspension feeder.En este estudio se compararon la estructura de los pólipos y los tipos celulares del coral duro Seriatopora hystrix y del coral blando Xenia umbellata, además de la composición de los ácidos grasos en sus tejidos. S. hystrix mostró una aparente carencia de células alimenticias especializadas, particularmente, un pequeño número de células glandulares mucosas y un bajo porcentaje de nematocistos conteniendo veneno. Los P-mastigóforos estuvieron presentes en el 1,52-5,7% de los nematocistos y los B-mastigóforos en el 1,28%. Por el contrario, hubo un alto porcentaje de nematocistos holotricos (24,86 - 55,5%) en los tentáculos y filamentos mesentéricos, respectivamente. Las zooxantelas fueron abundantes en la gastrodermis. Estas características sugieren que S. hystrix depende esencialmente de una nutrición autótrofa. Los pólipos de X. umbellata no presentaron cnidae, y las glándulas mucosas fueron abundantes, especialmente en la parte más basal del pólipo. La presencia de materia particulada en el celenteron y el bajo número de zooxantelas indican que X. umbellata es un suspensívoro, que utiliza mucus para atrapar las partículas en los tentáculos pinados. Un estudio comparativo de su composición química también reveló diferencias entre ambas especies. X. umbellata presentó un alto contenido proteico y lipídico mientras que S. hystrix se caracterizó por un alto contenido de carbonato de calcio. En S. hystrix, los ácidos grasos fueron predominantemente saturados (87,3%), siendo 16:0 y 18:0 los más abundantes. X. umbellata mostró predominancia de ácidos grasos insaturados (77,7%), siendo 16:1 y 18:1 los más abundantes. Las diferencias morfológicas y en composición bioquímica sugieren que S. hystrix tiene mayor dependencia de una alimentación autótrofa mientras que X. umbellata es mas bien un suspensívoro heterótrofo

Effect of temperature on two reef-building corals Pocillopora damicornis and P. verrucosa in the Red Sea

AbstractThe effects of temperature on two reef building corals Pocillopora damicornis and P. verrucosa inhabiting the Obhur Creek, a small embayment on the western, Red Sea coast of Saudi Arabia, was studied from December 2009 to November 2010. The overall annual range of seawater temperature in Obhur Creek was between 24.5°C and 33°C. Zooxanthellae abundance and diversity showed seasonal variations: the number of zooxanthellae in P. damicornis was slightly higher than in P. verrucosa, and the abundance of zooxanthellae of both species was low in summer and high during winter. The respiration rate of P. verrucosa did not vary between summer and winter, suggesting compensatory acclimation. In contrast, the respiratory rate in P. damicornis was lower in winter than in summer. During the winter season the metabolic rate was higher in both species owing to the optimum seawater temperature (30°C). As a result of the abundance of zooxanthellae and the optimum seawater temperature, the growth rates of the skeletons of the two coral species were higher in winter and lower in summer. In general, the results showed that P. verrucosa is more flexible with respect to temperature than P. damicornis. The difference in zooxanthellae thermal tolerances at 35°C may be due to the algal genotypes between the two species, resulting in P. damicornis becoming bleached as the rate of metabolism exceeds the rate of photosynthesis with increasing temperature

Effect of temperature on two reef-building corals Pocillopora damicornis and P. verrucosa in the Red Sea Coral bleaching Temperature Zooxanthellae Global warming Red Sea

Abstract The effects of temperature on two reef building corals Pocillopora damicornis and P. verrucosa inhabiting the Obhur Creek, a small embayment on the western, Red Sea coast of Saudi Arabia, was studied from December 2009 to November 2010. The overall annual range of seawater temperature in Obhur Creek was between 24.5 • C and 33 • C. Zooxanthellae abundance and diversity showed seasonal variations: the number of zooxanthellae in P. damicornis was slightly higher than in P. verrucosa, and the abundance of zooxanthellae of both species was low in summer and high during winter. The respiration rate of P. verrucosa did not vary between summer and winter, suggesting compensatory acclimation. In contrast, the respiratory rate in P. damicornis was lower in winter than in summer. During the winter season the metabolic rate was higher in both species owing to the optimum seawater temperature (30 • C). As a result of the abundance of zooxanthellae and the optimum seawater temperature, the growth rates of the skeletons of the two coral species were higher in winter and lower in summer. In general, the results showed that P. verrucosa is more flexible with respect to temperature than P. damicornis. The difference in zooxanthellae thermal tolerances at 35 • C may be due to the algal genotypes between the two species, resulting in P. damicornis becoming bleached as the rate of metabolism exceeds the rate of photosynthesis with increasing temperature

Chemical versus structural defense against fish predation in two dominant soft coral species (Xeniidae) in the Red Sea

Soft corals of the family Xeniidae are particularly abundant in Red Sea coral reefs. Their success may be partly due to a strong defense mechanism against fish predation. To test this, we conducted field and aquarium experiments in which we assessed the antifeeding effect of secondary metabolites of 2 common xeniid species, Ovabunda crenata and Heteroxenia ghardaqensis. In the field experiment, the metabolites of both investigated species reduced feeding on experimental food pellets in the natural population of Red Sea reef fishes by 86 and 92% for O. crenata and H. ghardaqensis, respectively. In the aquarium experiment, natural concentration of crude extract reduced feeding on experimental food pellets in the common reef fish Thalassoma lunare (moon wrasse) by 83 and 85%, respectively. Moon wrasse feeding was even reduced at extract concentrations as low as 12.5% of the natural concentration in living soft coral tissues. To assess the potential of a structural anti-feeding defence, sclerites of O. crenata were extracted and mixed into food pellets at natural, doubled and reduced concentration without and in combination with crude extract at 25% of natural concentration, and tested in an aquarium experiment. The sclerites did not show any effect on the feeding behavior of the moon wrasse indicating that sclerites provide structural support rather than antifeeding defense. H. ghardaqensis lacks sclerites. We conclude that the conspicuous abundance of xeniid soft coral species in the Red Sea is likely a consequence of a strong chemical defence, rather than physical defences, against potential predators

Natural antifouling compound production by microbes associated with marine macroorganisms — A review

In the marine environment, all hard surfaces including marine macroorganims are colonized by microorganisms mainly from the surrounding environment. The microorganisms associated with marine macroorganisms offer tremendous potential for exploitation of bioactive metabolites. Biofouling is a continuous problem in marine sectors which needs huge economy for control and cleaning processes. Biotechnological way for searching natural product antifouling compounds gained momentum in recent years because of the environmental pollution associated with the use of toxic chemicals to control biofouling. While, natural product based antifoulants from marine organisms particularly sponges and corals attained significance due to their activities in field assays, collection of larger amount of organisms from the sea is not a viable one. The microorganisms associated with sponges, corals, ascidians, seaweeds and seagrasses showed strong antimicrobial and also antifouling activities. This review highlights the advances in natural product antifoulants research from microbes associated with marine organisms