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1.
In April-May 1998, mass coral bleaching was observed in the lagoon of Rangiroa Atoll, Tuamotu Archipelago, French Polynesia. Six months later, the extent of bleaching-induced coral mortality was assessed at three sites. Corals in the fast-growing genus Pocillopora had experienced >99% mortality. Many large colonies of the slow-growing genus Porites (mean horizontal cross-sectional area 5.8 m2) had also died - a phenomenon not previously observed in French Polynesia and virtually unprecedented world-wide. At one site, 25% of colonies, or 44% of the pre-bleaching cover of living Porites, experienced whole-colony mortality. At the two other sites, recently dead Porites accounted for 41% and 82% of the pre-bleaching live cover. Mortality in Porites was negatively correlated with depth between 1.5 and 5 m. Using a 50-year dataset of mean monthly sea surface temperature (SST), derived from ship- and satellite-borne instruments, we show that bleaching occurred during a period of exceptionally high summer SST. 1998 was the first year in which mean monthly SSTs exceeded the 1961-1990 upper 95% confidence limit (29.4°C) for a period of three consecutive months. We suggest that the sustained 3-month anomaly in local summer SST was a major cause of coral mortality, but do not discount the synergistic effect of solar radiation. Recovery of the size-frequency distribution of Porites colonies to pre-bleaching levels may take at least 100 years.  相似文献   

2.
Considerable variability in bleaching was observed within and among soft coral taxa in the order Alcyonacea (Octocorallia: Cnidaria) on the central Great Barrier Reef (GBR, latitude 18.2°–19.0°S, longitude 146.4°–147.3°E) during the 1998 mass coral bleaching event. In April 1998, during a period of high sea surface temperatures, tissue samples were taken from bleached and unbleached colonies representative of 17 soft coral genera. The genetic identities of intracellular dinoflagellates (Symbiodinium spp.) in these samples were analyzed using PCR-denaturing gradient gel electrophoresis fingerprinting analysis of the internal transcribed spacer regions 1 and 2. Alcyonaceans from the GBR exhibited a high level of symbiont specificity for Symbiodinium types mostly in clade C. A rare clade D type (D3) was associated only with Clavularia koellikeri, while Nephthea sp. hosted symbionts in clade B (B1n and B36). Homogenous Symbiodinium clade populations were detected in all but one colony. Colonies that appeared bleached possessed symbiont types that were genetically indistinguishable from those in nonbleached conspecifics. These data suggest that parameters other than the resident endosymbionts such as host identity and colony acclimatization are important in determining bleaching susceptibility among soft corals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

3.
Peter J. Edmunds 《Marine Biology》2012,159(10):2149-2160
I tested the hypothesis that high pCO2 (76.6 Pa and 87.2 Pa vs. 42.9 Pa) has no effect on the metabolism of juvenile massive Porites spp. after 11 days at 28 °C and 545 μmol quanta m−2 s−1. The response was assessed as aerobic dark respiration, skeletal weight (i.e., calcification), biomass, and chlorophyll fluorescence. Corals were collected from the shallow (3–4 m) back reef of Moorea, French Polynesia (17°28.614′S, 149°48.917′W), and experiments conducted during April and May 2011. An increase in pCO2 to 76.6 Pa had no effect on any dependent variable, but 87.2 Pa pCO2 reduced area-normalized (but not biomass-normalized) respiration 36 %, as well as maximum photochemical efficiency (F v/F m) of open RCIIs and effective photochemical efficiency of RCIIs in actinic light (∆F/); neither biomass, calcification, nor the energy expenditure coincident with calcification (J g−1) was effected. These results do not support the hypothesis that high pCO2 reduces coral calcification through increased metabolic costs and, instead, suggest that high pCO2 causes metabolic depression and photochemical impairment similar to that associated with bleaching. Evidence of a pCO2 threshold between 76.6 and 87.2 Pa for inhibitory effects on respiration and photochemistry deserves further attention as it might signal the presence of unpredictable effects of rising pCO2.  相似文献   

4.
I. B. Kuffner 《Marine Biology》2001,138(3):467-476
The effects of water flow and ultraviolet radiation (UVR, 280–400 nm) on the reef coral Porites compressa Dana were explored in a manipulative flume experiment. The aim of this study was to determine whether this coral responds to changes in the UVR environment by adjusting the tissue concentration of UV-absorbing compounds (mycosporine-like amino acids, MAAs), and to see whether such an acclimation is affected by water flow. Also, calcification rate and chlorophyll-a concentration were measured during the experiment to estimate the potential costs (in the form of slowed growth and/or reduced photosynthetic capacity) to the coral–alga symbiosis of being exposed to UVR and producing MAAs. Branches of P. compressa from a single male colony were exposed to high or low flow (15 cm s−1 and 3 cm s−1, respectively) and ambient or no UVR in an outdoor, continuous-flow seawater system. Chlorophyll-a and MAA concentrations were determined after zero, 3 and 6 weeks of exposure to the experimental conditions. Increase in buoyant weight during the two 3-week periods was used to calculate calcification rate. The presence of UVR had a significant positive effect on total MAA concentration in the P. compressa colonies; however, there were significant interactions present. In colonies exposed to UVR, MAA concentration increased and then decreased to initial levels in high water flow, and increased steadily in low water flow. In colonies receiving no UVR, MAA concentration decreased steadily, declining 23% in 6 weeks. The absence of UVR did not result in higher chlorophyll-a concentrations, but the calcification rate was slightly affected by UVR. This study supports the putative photoprotective role of MAAs in P. compressa, and suggests that the costs of mitigating the effects of ambient UVR are detectable, but they are very small. Received: 29 February 2000 / Accepted: 20 September 2000  相似文献   

5.
Rising dissolved pCO2 is a mounting threat to coral reef ecosystems. While the biological and physiological impacts of increased pCO2 are well documented for many hermatypic corals, the potential effects on bioerosion processes remain largely unknown. Increases in pCO2 are likely to modify the direct interactions between corals and bioeroders, such as excavating sponges, with broad implications for the balance between biologically mediated deposition and erosion of carbonate in reef communities. This study investigated the effects of three levels of CO2 (present-day, mid-century and end-of-century projections) on the direct interaction between a bioeroding sponge, Cliona varians, and a Caribbean coral, Porites furcata. Increased pCO2 concentrations had no effect on the attachment rates of C. varians to the corals, and we observed no significant impact of pCO2 on the survival of either the coral or sponges. However, exposure to end-of-century levels of CO2-dosing (~750 μatm) reduced calcification in P. furcata and led to a significant increase in sponge-mediated erosion of P. furcata. These findings demonstrate that pCO2 can enhance erosional efficiency without impacting survival or competitive vigor in these two species. While few studies have considered the influence of pCO2 on the competitive outcomes of interactions between corals and other reef organisms, our study suggests that assessing the impacts of changing pCO2 on species interactions is crucial to adequately predict ecosystem-level responses in the future.  相似文献   

6.
Established hypotheses state that the rate of predation on coral reef fish should be highest during crepuscular periods (dawn and dusk) intermediate diurnally, and lowest nocturnally. We examined the relative risk of predation on juvenile French grunts (Haemulon flavolineatum Desmarest) during diurnal, dusk, and nocturnal periods on the fore- and back-reef at Teague Bay, U.S. Virgin Islands in July and August 1996. Tethering-devices recorded the exact amount of time between attaching a prey fish to its tether and subsequent predation on the prey fish. As tethering of prey usually inflates the actual rate of predation, times from our tethering devices were used to establish only the relative predation risk among treatments. During 3-h diurnal and nocturnal tethering experiments, relative predation was significantly higher during the nocturnal period, and differences between side of reef were not significant. In 30-min tethering experiments, which included all three time periods, the relative predation risk was significantly higher during dusk and nocturnal periods than during the diurnal period. Relative predation was not significantly different between the dusk and nocturnal periods, or between side of reef during any time period. The unexpected finding that the diurnal period had the lowest relative risk of predation indicates that the timing of predation events on reefs, as well as the adaptive reasons for nocturnal larval settlement, may need to be re-examined. Received: 11 February 1997 / Accepted: 21 October 1998  相似文献   

7.
The number and maximum body size of the gobioid fish, Paragobiodon echinocephalus, increase with the size of its obligate host coral, Stylophora. Only the largest two individuals breed monogamously in each coral head, and the reproductive success of each spawning is positively correlated with body size. In this study, the plasticity in size and age at maturity in P. echinocephalus was examined. We analyzed life history data from gobies 15–20 mm TL (total length) at their initial marking. Gobies found in larger corals were of lower rank in size order and began to breed later at a larger size, usually upon moving to other corals. The size at maturity ranged widely from 17.2 to 36.0 mm TL. After maturation, growth rates decreased. Mortality, however, was not affected by the timing of maturation. The host coral size did not affect the growth and mortality of marked fish, but the mortality rate of juveniles prior to marking appeared to be higher in smaller corals. The estimated lifetime reproductive success did not differ between the gobies inhabiting corals of different size. Thus the plasticity in size and age at maturity in this species may be maintained by frequency-dependent selection in choosing a host coral size that affects an individual’s social status. Received: 5 April 1995/Accepted after revision: 18 February 1996  相似文献   

8.
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  相似文献   

9.
We used microscopy, reflectance spectroscopy, pigment analysis, and photosynthesis-irradiance curves measured with variable fluorescence techniques to characterise the endolithic communities of phototrophic microorganisms in the skeleton of three massive corals from a shallow reef flat. Microscopic observations and reflectance spectra showed the presence of up to four distinct bands of photosynthetic microorganisms at different depths within the coral skeleton. Endolithic communities closer to the coral surface exhibited higher photosynthetic electron transport rates and a green zone dominated by Ostreobium quekettii nearest the surface had the greatest chlorophyll pigment concentration. However, Ostreobium was also present and photosynthetically active in the colourless band between the coral tissue and the green band. The spectral properties and pigment density of the endolithic bands were also found to closely correlate to photosynthetic rates as assessed by fluorometry. All endolithic communities were extremely shade-adapted, and photosynthesis was saturated at irradiances <7 μmol photons m−2s−1.  相似文献   

10.
Clonality and genetic structure of the coral Pocillopora damicornis sensu lato were assessed using five microsatellites in 12 populations from four islands of the Society Archipelago (French Polynesia) sampled in June 2008. The 427 analysed specimens fell into 132 multilocus genotypes (MLGs), suggesting that asexual reproduction plays an important role in the maintenance of these populations. A haploweb analysis of ITS2 sequences of each MLG was consistent with all of them being conspecific. Genetic differentiation was detected both between and within islands, but when a single sample per MLG was included in the analyses, the populations turned out to be nearly panmictic. These observations provide further evidence of the marked variability in reproductive strategies and genetic structure of P. damicornis throughout its geographic range; comparison with results previously obtained for the congeneric species Pocillopora meandrina underlines the importance of life history traits in shaping the genetic structure of coral populations.  相似文献   

11.
The blue mussel, Mytilus edulis, is the most conspicuous animal species in the northern Baltic rocky sublittoral. In the studied area the species lives at the margin of its salinity tolerance. Although dwarfed by the low-salinity conditions, blue mussels in the northern Baltic are very abundant and have a decisive role in the benthic and pelagic ecosystems. We studied abundance, size distribution, biomass and growth rate of blue mussels along a 270 km salinity gradient in the northern Baltic Sea. Samples (n=317, 1998-1999) from moderately exposed and exposed rocky shores at seven study areas were collected in the southern Archipelago Sea in the west and into the central Gulf of Finland in the east, where the species is becoming increasingly rare. The results show a marked decline in mean mussel size and biomass from the saline west to the less saline east. The growth rate also decreased with lower ambient salinity. However, abundance of small mussels was considerably higher in the central and eastern parts of the study area. Vertically, the highest biomass was recorded at intermediate depths (5 and 8 m), being lower at both shallower (3 m) and deeper bottoms (12 m). It is concluded that salinity is the foremost factor determining size structure and growth rate among populations within the area. The results suggest that predation further influences the population structure of blue mussels living at the edge of their range in the central Gulf of Finland ultimately set by their salinity tolerance.  相似文献   

12.
Summary Males of the primitive orthopteran, Cyphoderris strepitans, provide their mates with two types of nuptial food gift during mating: 1) females feed while coupled on the fleshy metathoracic wings of the male and the resultant flow of haemolymph and 2) the spermatophore transferred by the male includes a gelatinous spermatophylax which the female eats after mating. During the peak breeding interval, virgin males secure significantly more matings than their numbers relative to non-virgin males would predict. We tested the hypothesis that non-virgin males, having lost a substantial portion of available energy through previous investment in females, call significantly less than virgin males. Reduced calling should result in the attraction of fewer females and/or a greater risk of intrusion from competing males and consequently, a lowered mating success. Calling activity of male C. strepitans of varying mating status was monitored with a sound activated relay apparatus for two consecutive nights following their capture. Males were of three experimental groups, virgin, freshly wounded males (mated on the same night of capture), and old-wound males (mated at least one night prior to capture). Our cata showed a significant short-term reduction in signalling activity as a consequence of mating. Whereas there was no difference in the time spent calling by virgins on the first and second nights following capture, freshly wounded and oldwound males called significantly less on the first night than on the second. Furthermore, the proportion of males calling on both nights was significantly greater for the virgin and old-wound groups than for freshly wounded males. When the duration over which males called on the first night was compared with that of the second, virgin males showed no difference whereas old-wound males called for significantly shorter intervals on the first night. These results indicate that the cost of a large nutrient investment in females lowers the energy level in males below the threshold required for a prolonged signalling period. After a refractory interval during which males feed and replenish their energy reserves, calling levels equivalent to those which occur prior to mating are regained. Active female choice may also contribute to the reduced mating success of non-virgins, but this possibility remains untested.  相似文献   

13.
14.
Oxyhemocyanin (OxyHc), blood protein, glucose, acylglycerol (AG), and lactate of Litopenaeus vannamei juveniles were investigated. Statistical analyses were done on baseline values for each metabolite and on OxyHc from shrimp cultured in outdoor (20-m2 ponds) and indoor (90-l tanks). The values obtained were compared with blood metabolites reported in the literature for L. vannamei maintained under similar conditions. Normal distribution was only found for samples from indoor shrimp. The distribution values for blood metabolites from shrimp cultured in outdoor ponds and indoor tanks were right or left skewed. OxyHc, blood proteins, and glucose levels were higher in shrimp cultured in outdoor ponds than those observed in shrimp maintained in indoor tanks. These differences were attributed to availability of live food in outdoor culture ponds. The OxyHc/protein ratio showed that 60% of blood protein is OxyHc in outdoor-cultured shrimp and was lower than in indoor-cultured shrimp, and this ratio was lower than that found (97%) in indoor-cultured shrimp. The type of food was identified as a dominant factor affecting blood metabolites. AG in outdoor-cultured shrimp was significantly lower than that observed in indoor-maintained shrimp. Blood lactate concentration of shrimp was not affected by the culture conditions. The blood levels for protein, glucose, and lactate reported here are similar to those reported previously for other crustacean species, indicating that these can be used as a reference for evaluating the physiological status of L. vannamei. When we compared the OxyHc, blood protein, glucose, and lactate levels of L. vannamei juveniles with other crustacean species, we observed that crabs, lobsters (low-activity species), and closed-thelycum shrimp species (mean-activity species) had lower values in comparison to those observed in open-thelycum shrimp species, including L. vannamei juveniles. Possibly the blood metabolites and OxyHc could be reflecting the morphological and physiological adaptation of crustaceans, because these metabolites will depend on energetic demands.  相似文献   

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