Stimulation of fat-body production in the polyps of the coralPocillopora damicornis by the presence of mutualistic crabs of the genusTrapezia

A mutualism exists between the xanthid crabs of the genusTrapezia and their host corals,Pocillopora damicornis. It has previously been established that these obligate coral residents benefit the coral hosts by defending them against echinoderm predators and by increasing the survival of polyps located deep between the coral branches. In turn, the corals apparently benefit the crabs by producing lipid-filled structures on which the trapezid crabs feed; these fat bodies may contain some of the lipid which in previous studies of coral metabolism has been termed excess. It was determined by experiments conducted at the Hawaii Institute of Marine Biology that the presence of crabs in colonies ofP. damicornis stimulates the polyps to produce the lipid-filled fat bodies; removal of crabs causes corals to cease producing fat bodies. A structure very similar to the fat bodies ofP. damicornis has been reported inAcropora durvillei. Both of these coral genera ordinarily possess xanthid-crab mutualists. This association between branching corals and crustaceans may have evolved because corals of these genera provide shelter among their branches and because these shallow-water corals are evidently capable of releasing lipid which is excess to the corals' metabolic needs, but which can be utilized by the crabs.     

Effects of light of altered spectral composition on coral zooxanthellae associations and on zooxanthellae in vitro

Pocillopora damicornis (Linnaeus) and Montipora verrucosa (Lamarck) were collected from Hawaiian reefs. In two experiments (September 1979-January 1980: ca. 4 mo; August-October 1980; ca. 2 mo), these reef corals were grown under sunlight passed through filters producing light fields of similar quantum flux but different spectral composition. In vitro cultures of symbiotic zooxanthellae (Symbiodinium microadriaticum Freudenthal) from M. verrucosa were cultured under similar conditions for 15 d. Blue or white light promoted more coral skeletal growth than green or red light. In both coral species, blue light increased the total amount of chlorophyll a of the coral-zooxanthellae association. In the perforate species, M. verrucosa, the pigment concentration was elevated by an increase in the density of zooxanthellae, but the pigment concentrations per algal cell remained unchanged; in the non-perforate species, P. damicornis, it appears that pigment concentration was elevated by an increase in pigment per algal cell, and not by an increase in density of zooxanthellae. The sunloving reef-flat coral P. damicornis did not grow as rapidly as the shade-species M. verrucosa at the low quantum flux (about 10% sunlight) provided by the experimental treatments. The in vitro cultures of zooxanthellae from M. verrucosa exhibited growth rates in light of altered spectral quality that correlated with the responses of the host coral species: blue and white light supported significantly greater growth than green light, and red light resulted in the lowest growth rate.Contribution No. 678 of the Hawaii Institute of Marine Biology     

Spatial heterogeneity of photosynthesis and the effect of temperature-induced bleaching conditions in three species of corals

Heterogeneity in photosynthetic performance between polyp and coenosarc tissue in corals was shown using a new variable fluorescence imaging system (Imaging-PAM) with three species of coral, Acropora nobilis, Cyphastrea serailia and Pocillopora damicornis. In comparison to earlier studies with fibre-optic microprobes for fluorescence analysis, the Imaging-PAM enables greater accuracy by allowing different tissues to be better defined and by providing many more data points within a given time. Spatial variability of photosynthetic performance from the tip to the distal parts was revealed in one species of branching coral, A. nobilis. The effect of bleaching conditions (33°C vs. 27°C) was studied over a period of 8 h. Marked changes in fluorescence parameters were observed for all three species. Although a decline in _PSII (effective quantum yield) and Yi (the first effective quantum yield obtained from a rapid light curve) were observed, P. damicornis showed no visual signs of bleaching on the Imaging-PAM after this time. In A. nobilis and C. serailia, visual signs of bleaching over the 8 h period were accompanied by marked changes in F (light-adapted fluorescence yield), NPQ (non-photochemical quenching) and E _k (minimum saturating irradiance), as well as _PSII and Yi. These changes were most marked over the first 5 h. The most sensitive species was A. nobilis, which after 8 h at 33°C had reached a _PSII value of almost zero across its whole surface. Differential bleaching responses between polyps and coenosarc tissue were found in P. damicornis, but not in A. nobilis and C. serailia. NPQ increased with exposure time to 33°C in both the latter species, accompanied by a decreasing E _k, suggesting that the xanthophyll cycle is entrained as a mechanism for reducing the effects of the bleaching conditions.Communicated by L. Hagerman, Helsingør     

Physiological development of brooded larvae from two pocilloporid corals in Taiwan

In southern Taiwan, brooded larvae of Pocillopora damicornis and Seriatopora caliendrum are released year-round in synchrony with new moons, and each larval release occurs over multiple days. Using P. damicornis and S. caliendrum as a model system, we describe within-brood variation in larval phenotypes and test for release-day effects that influence larval performance in the pelagic phase. Research was conducted in 2010 using larvae from corals collected in June and July from Nanwan Bay (21°56.179??N, 120°44.85??E). In June, larval phenotypes of both species were characterized immediately following release, and their competency to settle assessed. In July, larvae of P. damicornis were collected on 3?days over the peak release period and incubated for 7?C11?days at 28.0?°C and 320???mol?quanta?m^?2?s^?1; their phenotypes and settlement competency were measured every 2?days. P. damicornis larvae released close to peak release were 1.6 times larger in size, contained twice the number of Symbiodinium larva^?1, and were 44?% more likely to settle in the first 24?h than larvae released early in the brood. In addition, peak-release larvae respired at a lower rate than larvae released late in the brood. Similarly, S. caliendrum larvae released close to peak release were 1.4 times larger in size and were 33?% more likely to settle in the first 5?h than larvae released early in the brood. In July, P. damicornis larvae differed between early (2?days prior to peak), peak, and late (2?days after peak) release. Protein content of early-release larvae was lower than peak- and late-release larvae, and this difference persisted throughout the development. Further, release day affected the way larval respiration varied throughout development. By showing that brooded coral larvae differ between release days and display maternal effects influencing performance in the swimming phase, our results suggest that pocilloporid corals utilize bet-hedging to increase reproductive success.     

The relative contribution of dinoflagellate photosynthesis and stored lipids to the survivorship of symbiotic larvae of the reef-building corals

The long-distance dispersal of larvae provides important linkages between populations of reef-building corals and is a critical part of coral biology. Some coral planulae have symbiotic dinoflagellates (Symbiodinium spp.) that probably provide energy in addition to the lipids provisioned within the egg. However, our understanding of the influence of symbionts on the energy metabolism and survivorship of planulae remains limited. This study examines the relative roles of symbiotic dinoflagellate photosynthesis and stored lipid content in the survivorship of the developing stages of the corals Pocillopora damicornis and Montipora digitata. We found that survivorship decreased under dark conditions (i.e. no photosynthetic activity) for P. damicornis and M. digitata at 31 and 22 days after release/spawning, respectively. The lipid content of P. damicornis and M. digitata planulae showed a significant decrease, at a higher rate, under dark conditions, when compared with light conditions. When converted to energy equivalents, the available energy provided by the depletion of lipids could account for 41.9 and 84.7% of larval metabolism for P. damicornis (by day 31) and 38.4 and 90.1% for M. digitata (by day 21) under light and dark conditions, respectively. This finding indicates that not all energy requirements of the larvae are met by lipids: energy is also sourced from the photosynthetic activities of the symbiotic dinoflagellates within these larvae, especially under light conditions. In addition, the amounts of three main lipid classes (wax esters, triglycerides, and phospholipids) decreased throughout the experiment in the planulae of both species, with the wax ester content decreasing more rapidly under dark conditions than under light conditions. The observations that the planulae of both species derive considerable amounts of energy from wax esters, and that symbiotic dinoflagellates enable larvae to use their stores at lower rates, suggested that symbiotic dinoflagellates have the potential to extend larval life under light conditions.     

Dietary overlap among coral-feeding butterflyfishes (Chaetodontidae) at Lizard Island,northern Great Barrier Reef

This study documented the range of corals, and other prey types, consumed by 20 species of butterflyfishes, which co-occur at Lizard Island, northern Great Barrier Reef, Australia. Six species (Chaetodon aureofasciatus, C. baronessa, C. lunulatus, C. plebius, C. rainfordi and C. trifascialis) fed almost exclusively on scleractinian corals, and a further eight species (C. citrinellus, C. kleinii, C. lunula, C. melannotus, C. rafflesi, C. speculum, C. ulietensis, and C. unimaculatus) took a significant proportion of their bites from corals. The other six species (C. auriga, C. ephippium, C. lineolatus, C. semeion, C. vagabundus, and Chelmon rostratus) rarely consumed coral, but fed on small discrete prey items from non-coral substrates. Coral-feeding butterflyfishes consumed a wide range of corals. Chaetodon lunulatus, for example, consumed 51 coral species from 24 different genera. However, there was up to 72% dietary overlap between coral-feeding butterflyfishes, with 11/14 species feeding predominantly on Acropora hyacinthus or Pocillopora damicornis. The most specialised corallivore, C. trifascialis, took 88% of bites from A. hyacinthus. Chaetodon trifascialis defend territories encompassing one or more colonies of A. hyacinthus, and may have prevented other species such as C. lunulatus from feeding even more extensively on this coral. This study has shown that coexistence of coral-feeding butterflyfishes occurs despite an apparent lack of partitioning of prey resources. While different coral-feeding butterflyfishes were more or less selective in their use of different coral prey, virtually all species fed predominantly on A. hyacinthus or P. damicornis.Electronic Supplementary Material Supplementary material is available for this article at     

A novel Vibrio sp. pathogen of the coral Pocillopora damicornis

A coral pathogen was isolated from the diseased tissue of Pocillopora damicornis in Zanzibar. The pathogenic bacterium, referred to as Vibrio coralyticus YB, was classified as a member of the genus Vibrio. Based on its 16S rDNA sequence, V. coralyticus is probably a new species. In controlled aquaria experiments at 26-29°C, inoculation of pure cultures of V. coralyticus YB either into the seawater or by direct contact onto the coral caused tissue lysis of P. damicornis fragments. At 29°C, lysis began as small white spots after 3-5 days, rapidly spreading so that by 2 weeks the entire tissue was destroyed, leaving only the intact bare skeleton. When an infected diseased coral was placed in direct contact with a healthy one, the healthy coral lysed in 2-4 days, further indicating that the disease was contagious. Inoculation with as few as 30 bacteria ml^-1 was sufficient to infect and lyse corals. Seawater temperature was a critical variable for the infectious process: infection and lysis occurred rapidly at 27-29°C, slowly at 26°C and was not observed at 25°C. The data suggest that the presence of V. coralyticus YB, even in low numbers, in seawater surrounding a coral reef will lead to tissue destruction of P. damicornis, when seawater temperatures rise.     

Night irradiance and synchronization of lunar release of planula larvae in the reef coral Pocillopora damicornis

Pocillopora damicornis (Linnaeus), which is known to release planula larvae on a monthly cycle, was grown in full daytime solar irradiance, but with four treatments of night irradiance: (1) natural night irradiance, (2) shifted-phase (total darkness during nights of full moon with artificial irradiance at lunar intensity on nights of new moon), (3) constant full moon (full lunar irradiance every night), and (4) constant new moon (total darkness every night). The reproductive cycle of the corals held in the shifted-phase treatment moved out of synchrony with the cycle of corals exposed to a natural lunar cycle of night irradiance. Two previously described types of P. damicornis were tested. The Type Y normally start releasing larvae at full moon, with peak production at third quarter. In the shifted-phase treatment they began releasing planulae at new moon (artificial full moon), with peak production at first quarter. The Type B corals, that normally start releasing planulae at new moon with peak production at first quarter, began to release planulae at full moon (artificial new moon), with peak production at third quarter. Populations of corals grown either in the constant full moon or constant new moon treatment quickly lost synchronization of monthly larva production, although production of planulae continued. Thus spawning is synchronized by night irradiance.Contribution No. 702 of the Hawaii Institute of Marine Biology     

Mode and timing of reproduction in some common hermatypic corals of Hawaii and Enewetak

Common Hawaiian and Enewetak corals were examined to determine the method and mining of reproduction. Of the 7 Hawaiian species examined for the release of planulae, only 2 have planulated in captivity, Pocillopora damicornis and Cyphastrea ocellina. Both planulate year-round and both are characteristic of reef flats. Four of the 5 species which did not planulate were found to contain eggs, but not planulate, when polyps were examined microscopically. These 5 species do not usually occur on reef flats. Seven of the 12 Enewetak species examined in June, July, August and January planulated; 4 of these were pocilloporids, all of which are common in shallow water. Only 3 of the 8 species of Acropora planulated, and these 3 occur solely in shallow water. A greater proportion of the Pocillopora spp. colonies than Acropora spp. colonies planulated and they released more planulae per head. In previous studies and in this one, coral species which have released planulae are characteristic of shallow-water environments such as reef flats. Most of the 10 species reported on here which failed to planulate in captivity are not commonly found on reef flats. The failure to detect planulation in so many species, particularly those of deeper water, suggests that common hermatypic corals may not all reproduce in the same way, and that mode of reproduction may be related to habitat.     

Microbial consortia increase thermal tolerance of corals

This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated α and γ-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 °C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in F _V /F _M , typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in F _V /F _M . This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community.     

Light responses of a scleractinian coral (Plerogyra sinuosa)

During daytime Plerogyra sinuosa Dana displays globular expandable tentacles (bubbles) which foster the photosynthetic ability of the coral. Adaptational responses of this coral to different depths (5–25 m) and light conditions were investigated by photosynthetic pigment analysis, insitu measurements of oxygen production, transplantation and shading experiments. Pigment concentrations per unit tissue dry weight were variable, but unrelated to depth. Pigment concentrations per zooxanthellae cell remained constant and bubble size increased with depth. Light intensity at 25 m was 20 to 25% of the 5-m value, but daily integrated rates of photosynthesis were 65% of the 5-m rates, indicating a higher light utilization efficiency in deeper corals. Coral heads transplanted from 25 to 5 m died within 20 d if not protected against UV-radiation, but corals transplanted from 5 to 25 m acclimatized to the new light condition. Photosynthetic oxygen production and bubble size increased in shaded, sun-adapted corals within 60 min and decreased in sun-exposed, shade-adapted corals. The variable bubble size is interpreted as an adaptational mechanism to optimize light exposure of zooxanthellae.     

Lipids and stable carbon isotopes in two species of Hawaiian corals,<Emphasis Type="Italic"> Porites compressa</Emphasis> and<Emphasis Type="Italic"> Montipora verrucosa</Emphasis>, following a bleaching event

Mass coral bleaching events have occurred on a global scale throughout the worlds tropical oceans and can result in large-scale coral mortality and degradation of coral reef communities. Coral bleaching has often been attributed to periods of above normal seawater temperatures and/or calm conditions with high levels of ultraviolet radiation. Unusually high shallow-water temperature (>29°C) in Kaneohe Bay, Hawaii, USA, in late summer (20 August–9 September) and fall (1–7 October) of 1996 produced visible bleaching of two dominant corals, Porites compressa Dana, 1864 and Montipora verrucosa Dana, 1864. The present study examined chlorophyll a (chl a), total lipid concentrations, and lipid class composition in corals of both species in which the entire colony was non-bleached, moderately bleached, or bleached. Skeletal, host tissue, and algal symbiont ¹³C values were also measured in non-bleached and bleached colonies. In additional unevenly bleached colonies, paired samples were collected from bleached upper surfaces and non-bleached sides. Samples were collected on 20 November 1996 during the coral recovery phase, a time when seawater temperatures had been back to normal for over a month. Chl a levels were significantly lower in bleached colonies of both species compared with non-bleached specimens, and in bleached areas of unevenly bleached single colonies. Total lipid concentrations were significantly lower in bleached P. compressa compared with non-bleached colonies, whereas total lipid concentrations were the same in bleached and non-bleached M. verrucosa colonies. The proportion of triacylglycerols and wax esters was lower in bleached colonies of both species. Both bleached and non-bleached M. verrucosa had from ~17% to 35% of their lipids in the form of diacylglycerol, while this class was absent in P. compressa. ¹³C was not significantly different in the host tissue and algal symbiont fractions in non-bleached and bleached samples of either species. This suggests that the ratio of carbon acquired heterotrophically versus photosynthetically was the same regardless of condition. Skeletal ¹³C was significantly lower in bleached than in non-bleached corals. This is consistent with previous findings that lower rates of photosynthesis during bleaching results in lower skeletal ¹³C values. The two species in this study displayed different lipid class compositions and total lipid depletions following bleaching, suggesting that there is a difference in their metabolism of lipid reserves and/or in their temporal responses to bleaching and recovery.Communicated by J.P. Grassle, New Brunswick     

Diel fluctuations of mycosporine-like amino acids in shallow-water scleractinian corals

Reports of bathymetric decrease in the total mycosporine-like amino acid (MAA) concentration of benthic invertebrates suggest that light gradients may be important determinants of MAA content. With the pronounced diel light changes, distinct temporal variations in MAA concentrations might also be expected. We examined the changes in the abundance of MAA in three shallow-water scleractinian corals, Pavona divaricata, Galaxea fascicularis and Montipora digitata from Okinawa, Japan, in relation to daily cycles in solar radiation and tested whether the species have different capabilities for protection against UVR depending on their MAA composition. The results show that symbiotic algae freshly isolated from the investigated coral species do not contain MAAs and that distribution of these compounds resided only within the animal tissue. Total MAA content in the tissue of P. divaricata, G. fascicularis and M. digitata rose rapidly at midday and significantly dropped at night. The observed variations were by a factor of two and, thus, very dramatic. For all the investigated coral species, total MAA concentrations were significantly correlated with the diurnal cycle in solar radiation, during both winter and summer seasons. Seawater temperature was significantly correlated with MAA levels only in the June experiment, but represented no more than 20% of the MAA variation in all three coral species, whereas solar radiation explained 60–70% of the MAA fluctuations. This suggests that MAAs are an integral component of the hard corals biochemical defense system against high solar irradiance stress. The diurnal increase in total MAA concentrations was due to an increase in the concentration of imino-MAA species of up to 2–2.5-fold of their pre-dawn values. In contrast, the oxocarbonyl-MAA mycosporine-glycine (Myc-Gly) showed the lowest (Tukey–Kramer HSD test: P<0.05) values at midday, compared to afternoon and night hours. Analysis of diel changes in chlorophyll fluorescence and chlorophyll a content of the investigated species revealed that P. divaricata and G. fascicularis were less sensitive to the high levels of ambient irradiance compared to M. digitata. In P. divaricata and G. fascicularis, Myc-Gly, an MAA with an antioxidant function, is the most abundant MAA, contributing about 70% to the total MAA pool, whereas the major MAA factions in M. digitata were represented by oxidatively robust imino-MAAs. We speculate that MAAs furnish scleractinian corals with protection from biologically damaging ultraviolet radiation through both the direct sunscreening activity of imino-MAAs and the antioxidant properties of oxocarbonyl-MAAs and suggest that the predominance, in the host tissue, of MAA species with an antioxidant ability may render corals more tolerant to high photosynthetically active and ultraviolet radiation.Communicated by T. Ikeda, Hakodate     

Larval survivorship, competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis

Larval dispersal and recruitment are important in determining adult coral distribution; however, few studies have been made of coral larval dispersal. This study examined the larval behavior, survivorship competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis, in relation to different potential larval dispersal patterns. We also examined the lipid content of H. coerulea as a means of flotation and a source of energy. Planulae of H. coerulea were on average 3.7 mm in length, lacked zooxanthellae, and were mostly benthic, probably because of restricted movement and low lipid content (54% by dry weight). Planulae of P. damicornis were on average 1.0 mm in length, had zooxanthellae and swam actively. The competency period of H. coerulea was shorter (30 days) than that of P. damicornis (100 days). Forty percent of H. coerulea planulae crawled onto the substrata within 1 h of release, and 47% settled within 6 h. By contrast, fewer than 10% of P. damicornis planulae crawled onto the substrata within the first hour and 25% settled within 6 h of release. The planulae of H. coerulea may have a narrower dispersal range than those of P. damicornis, settling and recruiting near parent colonies. Thus, brooding corals exhibit variations in larval dispersal patterns, which are characterized by their position in the water column and competency periods.     

Association of <Emphasis Type="Italic">Waminoa</Emphasis> sp. (Acoela) with corals in the Wakatobi Marine Park,South-East Sulawesi,Indonesia

This is the first quantitative study on the prevalence of epizoic Waminoa sp. acoel worms and their association with corals in the Wakatobi Marine National Park (WMNP), South-East Sulawesi, Indonesia. Three replicate transects were laid on the reef crest, flat and slope at six sites in 2006 and eight sites in 2007. Four of the sites were common in both years. In total 69 transects were surveyed in 2006, and 87 transects in 2007. A total of 4.8% of all observed hard corals were associated with acoel worms in 2006 and 2.6% of hard and soft corals in 2007. Acoels were present on 16 and 21 of the coral taxa studied in 2006 and 2007 respectively. The worms were strongly associated with the azooxanthellate coral Tubastrea spp. and were rare or absent on the most abundant coral genera Montipora and Porites. The mean number of corals having acoels was highest on reef slopes, whereas acoels were virtually absent on reef flats. Corals that had a high and a medium cover of worms were more common in 2007 than in 2006. No significant trend in the adaptation of the zooxanthellae of Waminoa sp. to different depths at different sites was revealed. The impact of the worm on the coral is unknown, but high numbers may have a shading effect and a negative impact on the coral’s photophysiology. This acoel merits more study of its life cycle, its photophysiology, and its impact on its host corals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Do corals select zooxanthellae by alternative discharge?

Loss of zooxanthellae (dinoflagellate Symbiodinium) from corals will sometimes lead to mass mortality of corals. To detect and quantify Symbiodinium released from corals, we developed a zooxanthellae “trap” and a quantitative PCR (qPCR) system with Symbiodinium clades A–F-specific primer sets. The trap was attached to a branch or the surface of several wild stony corals, and the water samples within the traps, including released Symbiodinium, were subjected to qPCR. All tested corals released clade C Symbiodinium at estimates of ~5,900 cells h⁻¹ cm⁻² of coral surface. Although all tested Pocillopora eydouxi harboured both clades C and D, some of these colonies released only clade C or released a lesser amount of clade D than that in the tissues. Our Symbiodinium quantification system revealed that wild hermatypic corals constantly release Symbiodinium to the environment. Our result suggests that some corals may discharge certain clades of Symbiodinium alternatively.     

Effects of ambient levels of solar ultraviolet radiation on zooxanthellae and photosynthesis of the reef coral Montipora verrucosa

Paired flat plates of the hermatypic coral Montipora verrucosa from Kaneohe Bay, Oahu, Hawaii, were acclimated to photosynthetically active radiation (PAR) only and to full sunlight (PAR+UV) for several weeks in the summer of 1990. After the acclimation period, photosynthesis, both in PAR-only and PAR+UV as well as dark respiration were measured. Levels of the UV-absorbing compounds, S320, density of zooxanthellae, and chlorophyll a concentration were determined. Corals acclimated in PAR+UV had higher levels of the UV-protective compounds and lower areal zooxanthellae densities than corals acclimated in PAR-only. Chlorophyll a per unit volume of coral host and per algal cell did not differ between corals from the two acclimation treatments. Corals acclimated to PAR+UV displayed higher photosynthesis in full sunlight than corals acclimated to PAR-only, but when photosynthesis was measured in the light regime to which the corals had been acclimated, there were no differences in photosynthesis. Dark respiration was the same for corals from the two acclimation treatments regardless of the light quality immediately preceding the dark period.Contribution No. 902 HIMB     

Microheterotrophic utilization of mucus released by the Mediterranean coral Cladocora cespitosa

The amount of mucus released by the Mediterranean coral Cladocora cespitosa (L.) was determined in laboratory experiments and the incorporation of mucus into bacterial biomass was investigated by means of incubation experiments in 1984. Mean mucus release was 8.5 g (mucus dry wt) pclyp^-1 h^-1 and amounted to 44% of the respiratory carbon losses of the coral since mean organic carbon content of freshly collected mucus was 102.2g C mg (mucus dry wt)^-1. Due to the abundance of C. cespitosa in the shallow littoral of the Bight of Piran, the energy content of mucus released is estimated to correspond to about 20% of the phytoplankton primary production in this area. Furthermore, the carbon conversion efficiency of 20% obtained from the bacterial population during decomposition of mucus indicates the high nutritional value of C. cespitosa mucus, although bacterial carbon onto mucus particles contributes less than 0.1% to the total organic carbon pool of the mucus.     

Using three-dimensional surface area to compare the growth of two Pocilloporid coral species

Many facets of coral research require coral colony surface area estimates. This study developed a relationship between the two-dimensional (2D) projected area and the three-dimensional (3D) whole colony surface area for two commonly studied Indo-Pacific coral species: Pocillopora damicornis and Stylophora pistillata. The surface index function was used to measure the growth of colonies in situ around Heron reef on the southern Great Barrier Reef. The results show that while growth between the two species was not significantly different when measured in two dimensions, the 3D area showed significantly different growth rates with S. pistillata growing at almost double the rate of P. damicornis. The study demonstrates that it is possible to make reliable estimates of the 3D surface area of entire colonies of these complex branching coral species, using the plan view of the coral and a pre-determined surface index function. In addition, this study shows that the 3D surface area provides a more useful measure of colony growth than the traditional methods of either 2D area or longest dimension.     

Assessing stress response of Stylophora pistillata towards oil and phosphate pollution in the Gulf of Aqaba,using molecular and biochemical markers

Crude oil (from oil terminal) and raw phosphate (from phosphate port) pollution are responsible for the lowered health conditions of coral reefs at their vicinity in the Jordanian coast of the Gulf of Aqaba. Both in situ incubations and ex situ laboratory exposure experiments were used to study the effects of those pollutants on corals, by using molecular and biochemical biomarkers in the coral Stylophora pistillata. For ex situ part of the experiment, crude oil and raw phosphate were added to a final concentration of 500?ppm for both pollutants. The DNA damage was assessed by Comet assay, while biochemical stress markers were reassessed by lipid peroxidation (LPO) test. Although the corals looked healthy from outside, the use of stress biomarkers indicated that they are under high pressure at the cellular level. The corals incubated with oil and phosphate had more DNA damage and LPO in comparison with the control samples. The results obtained suggest that the use of stress biomarkers can be used as important prognostic tools for examining the sub-lethal stress on corals before their death.