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对造礁石珊瑚与其共生藻共生研究现状及其在全球变化下的适应能力进行较全面的综述.造礁石珊瑚与遗传和生理功能独特的共生藻组成内共生关系是成功演化的范例.近年来对珊瑚共生体的分子系统学研究表明共生藻遗传多样性极为丰富,当前认为共生藻属至少包括8个(A-H)各自包含亚系群的世系或系群.珊瑚-共生藻共生功能体对诸如全球变化引起的海水温度上升等环境变化十分敏感.由于珊瑚以及珊瑚礁面临气候变化的严峻挑战,对珊瑚与其共生藻共生关系和共生功体适应能力的研究将是未来重要的研究领域之一. 相似文献
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The ultrastructure of symbiotic dinoflagellates (Symbiodinium sp., zooxanthellae) in the sea anemone Aiptasia pallida Verrill was examined in well-fed or starved (up to 120 days) anemones maintained under two light levels (5 and 50 μmol · m?2· s?1). Cell size of zooxanthellae was not affected by feeding history; however, both light and feeding history affected the relative cell volume of chloroplasts, lipids, and vacuoles. Stereological analysis of transmission electron micrographs showed that algae in low-light starved anemones had 10 times as much lipid (17.4% of cell volume) as those in well-fed anemones under the same light conditions (1.8%). The lipid content of algae from anemones in high light increased from 15.4% in well-fed anemones to 30.1% in starved anemones. The starch content of zooxanthellae in low-light anemones was law (4.1%) and not affected by feeding history, while the starch content of zooxanthellae in high-light anemones was greater (10.7%), with some differences among groups. Algal photoacclimation to low light included an increase in chloroplast relative volume from 17% (in well-fed high-light anemones) to 33% in well-fed low-light anemones. Starvation of the host resulted in a significant decrease in chloroplast volume in zooxanthellae in anemones at both light levels. Morphometry provides quantitative confirmation of biochemical and physiological data on zooxanthellae, because the changes in zooxanthellae with starvation of the host are consistent with other indicators of nutrient limitation of zooxanthellae of A. pallida held without food for long periods of time. 相似文献
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The majority of reef-building corals acquire their obligate algal symbionts ( Symbiodinium ) from the environment. However, factors shaping the initial establishment of coral–algal symbioses, including parental effects, local environmental conditions and local availability of symbionts, are not well understood. This study monitored the uptake and maintenance of Symbiodinium in juveniles of two common corals, Acropora tenuis and Acropora millepora , that were reciprocally explanted between sites where adult colonies host different types of Symbiodinium . We found that coral juveniles were rapidly dominated by type D Symbiodinium , even though this type is not found in adult colonies (including the parental colonies) in four out of the five study populations. Furthermore, type D Symbiodinium was found in less than one-third of a wide range of coral species ( n > 50) sampled at the two main study sites, suggesting that its dominance in the acroporid juveniles is not because it is the most abundant local endosymbiotic type. Moreover, dominance by type D was observed irrespective of the light intensity to which juveniles were exposed in a field study. In summary, despite its relatively low abundance in coral assemblages at the study sites and irrespective of the surrounding light environment, type D Symbiodinium is the main symbiont type initially acquired by juveniles of A. millepora and A. tenuis . We conclude that during early ontogeny in these corals, there are few barriers to the uptake of Symbiodinium types which differ from those found in parental colonies, resulting in dominance by a highly infectious and potentially opportunistic symbiont. 相似文献
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The capacity for photoacclimation to light at 100 or 600 μmol photons·m?2·s?1 and the subsequent response to thermal stress was examined in four genetically distinct cultures of symbiotic dinoflagellates in the genus Symbiodinium with the ITS2 designations A1, A1.1, B1, and F2. While all algal types showed typical signs of photoacclimation to high light via a reduction in chl a, there was a differential response in cellular growth, photosystem II (PSII) activity, and the chl a‐specific absorption coefficient between cultures. When maintained at 32°C for up to 10 days, significant variation in the susceptibility to thermal stress was observed in the rate of loss in PSII activity and electron transport, PSII reaction center degradation, and cellular growth. The order of thermal tolerance did not change between the two light levels. However, as expected, loss in photosynthetic function was exacerbated in the thermally sensitive phylotypes (B1 and A1.1) when acclimated to the higher light intensity. There was no consistent relationship between thermal tolerance and changes in light energy dissipation via non‐photochemical pathways. Phylotypes F2 and A1 showed a high degree of thermal tolerance, yet the cellular responses to light and temperature were markedly different between these algae. The F2 isolate showed the greatest capacity for photoacclimation and growth at high light and temperature, while the A1 isolate appeared to adjust to thermal stress by a slight decline in PSII activity and a significant decline in growth, possibly at the expense of increased photosystem and cellular repair rates. 相似文献
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Symbiotic algae (Symbiodinium sp.) in scleractinian corals are important in understanding how coral reefs will respond to global climate change. The present paper reports on the diversity of Symbiodinium sp. in 48 scleractinian coral species from 25 genera and 10 families sampled from the Xisha Islands in the South China Sea, which were identified with the use of restriction fragment length polymorphism (RFLP) of the nuclear ribosomal DNA large subunit gene (rDNA). The results showed that: (i) Symbiodinium Clade C was the dominant zooxanthellae in scleractinian corals in the Xisha Islands; (ii) Symbiodinium Clade D was found in the corals Montipora aequituberculata, Galaxea fascicularis, and Plerogyra sinuosa; and (iii) both Symbiodinium Clades C and D were found simultaneously in Montipora digitata, Psammocora contigua, and Galaxeafascicularis. A poor capacity for symbiosis polymorphism, as uncovered by RFLP, in the Xisha Islands indicates that the scleractinian corals have low adaptability to environmental changes. Further studies are needed to investigate zooxanthellae diversity using other molecular markers. 相似文献
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This study compared the effect of heat stress on coral‐associated bacterial communities among juveniles of the coral, Acropora tenuis, hosting different Symbiodinium types. In comparison to a control temperature treatment (28 °C), we documented dramatic changes in bacterial associates on juvenile corals harbouring ITS 1 type D Symbiodinium when placed in a high (32 °C) temperature treatment. In particular, there was a marked increase in the number of retrieved Vibrio affiliated sequences, which coincided with a 44% decline in the photochemical efficiency of the D‐juveniles. Interestingly, these Vibrio sequences affiliated most closely with the coral pathogen, Vibrio coralliilyticus, which has been implicated in some coral disease outbreaks. In contrast, A. tenuis hosting ITS 1 type C1 Symbiodinium did not exhibit major bacterial shifts in the elevated temperature treatment, indicating a more stable bacterial community during thermal stress; concomitantly a decline (10%) in photochemical efficiency was minimal for this group. D juveniles that had been exposed to moderately elevated sea temperatures (30 °C) in the field before being placed in the control temperature treatment displayed a decrease in the number of Vibrio affiliated sequences and bacterial profiles shifted to become more similar to profiles of corals harbouring type C1 Symbiodinium. In combination, these results demonstrate that thermal stress can result in shifts in coral‐associated bacterial communities, which may lead to deteriorating coral health. The lower resilience of A. tenuis to thermal stress when harbouring Symbiodinium D highlights the importance of inter‐kingdom interactions among the coral host, dinoflagellate endosymbiont and bacterial associates for coral health and resilience. 相似文献
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The underwater light field of lakes, estuaries, and oceans may vary greatly in spectral composition. Phytoplankton in these environments must contain pigments that absorb the available colors of light. If spectral quality changes, acclimation to the new spectral environment would confer an ecological advantage in terms of photosynthesis and growth. Here, we explored the capacity of eight marine cryptophytes to adjust pigmentation in response to changes in spectral irradiance and related effects on light absorption, photosynthetically useable radiation (PUR), and growth rate. The pigment composition of all species changed in some way in response to shifts in spectral irradiance, but not all pigment changes could be considered advantageous in the context of chromatic acclimation. For most species, absorption by chl-a and chl-c2 resulted in highest absorption in the blue region, highest PUR values for blue-light grown cells, and highest growth rates in blue light. The exception was Chroomonas mesostigmatica (CCMP 1168), which contains a high percentage of Cryptophyte-Phycocyanin (Cr-PC) 645, absorbs strongly in the orange-to-red region of the spectrum, and grew fastest under red light. The position and magnitude of the maximum and secondary absorption peak of Cr-PC 569, the phycobiliprotein pigment of Hemiselmis cryptochromatica, varied with spectral irradiance. The underlying cause remains unknown, but may represent a mechanism by which cryptophytes optimize photon capture. 相似文献
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Daisuke Taira Tai Chong Toh Chin Soon Lionel Ng Hai Xin Loke Lutfi Afiq-Rosli Patrick C. Cabaitan 《Marine and Freshwater Behaviour and Physiology》2017,50(5-6):375-385
The recovery of bleached corals is crucial in ensuring the persistence of the coral reef ecosystem function. This study investigated whether relocating bleached Platygyra sinensis colonies was a viable measure to accelerate their recovery. During a mild bleaching event in 2014, eight bleached colonies of P. sinensis were relocated from an affected reef at Sultan Shoal, Singapore, to a reef at Kusu that was less impacted. Another eight colonies at Sultan Shoal were tagged as controls. After five months, 88% of relocated bleached colonies at Kusu showed full recovery whereas only 25% of the control bleached colonies at Sultan Shoal had recovered. The differential coral recovery among the two sites was most likely due to lower seawater temperatures and faster water flow at Kusu, which helped to mitigate the effects of thermal stress on the bleached corals. This relocation study demonstrated that relocating bleached P. sinensis to sites with more favourable environmental conditions is a viable approach to reduce bleaching impacts for this species. 相似文献
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DAVID J. SMITH 《Global Change Biology》2011,17(1):45-55
Coral bleaching is a major concern to researchers, conservationists and the general public worldwide. To date, much of the high profile attention for bleaching has coincided with major environmental impacts and for many the term coral bleaching is synonymously associated with coral mortality (so‐called ‘lethal’ bleaching episodes). While this synonymous association has undoubtedly been key in raising public support, it carries unfair representation: nonlethal bleaching is, and always has been, a phenomenon that effectively occurs regularly in nature as corals acclimatize to regular periodic changes in growth environment (days, seasons etc). In addition, corals can exhibit sublethal bleaching during extreme environmental conditions whereby mortality does not occur and corals can potentially subsequently recover once ambient environmental conditions return. Perhaps not surprisingly it is the frequency and extent of these non and sublethal processes that yield key evidence as to how coral species and reef systems will likely withstand environmental and thus climatic change. Observations of non and sublethal bleaching (and subsequent recovery) are arguably not as readily reported as those of lethal bleaching since (1) the convenient tools used to quantify bleaching yield major ambiguity (and hence high potential for misidentification) as to the severity of bleaching; and (2) lethal bleaching events inevitably receive higher profile (media) attention and so are more readily reported. Under‐representation of non and sublethal bleaching signs may over‐classify the severity of bleaching, under‐estimate the potential resilience of reefs against environmental change, and thus ultimately limit (if not depreciate) the validity and effectiveness of reef management policies and practices. While bleaching induced coral mortality must remain our key concern it must be better placed within the context of bleaching signs that do not result in a long‐term loss of reef viability. 相似文献
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This study examined the dietary habits and functional composition of butterflyfishes in the Chagos Archipelago, central Indian Ocean. Eighteen species of butterflyfishes were recorded in Chagos, including six obligate corallivores (Chaetodon bennetti, Chaetodon guttatissimus, Chaetodon meyeri, Chaetodon trifascialis, Chaetodon trifasciatus and Chaetodon zanzibarensis), five facultative corallivores (Chaetodon auriga, Chaetodon falcula, Chaetodon interruptus, Chaetodon kleinii and Chaetodon madagaskariensis), two non‐corallivores (Chaetodon lunula and Chaetodon xanthocephalus) and a further five species (Chaetodon citrinellus, Chaetodon lineolatus, Heimitaurichthys zoster, Heniochus monoceros and Forcipiger flavissimus), for which local dietary habits were not studied. There were marked differences in the abundance of butterflyfishes among sites and between reef zones, mostly associated with variation in abundance of scleractinian corals. Obligate coral‐feeding species (mostly C. trifascialis) dominated across all sites. This study suggests that coral feeding and high levels of dietary specialization contribute to high population‐level fitness among coral reef butterflyfishes. Despite being more vulnerable to habitat disturbances and coral loss, it appears likely that specialist coral‐feeding butterflyfishes are also much more resilient to occasional disturbances, and therefore dominate in a wide range of coral reef habitats. 相似文献
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An investigation of the physiology of a number of blue-green algae isolated from peat sites in Glenamoy, Co. Mayo, is reported. Physical and nutritional parameters were studied and correlated to the conditions prevailing in the natural environment of the algae. The occurrence of blue-green algae in peat was found to be controlled by the pH level and the presence of phosphorus in the environment. 相似文献
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以涠洲岛造礁石珊瑚群落为研究对象,分析其群落物种组成、多样性、Raunkiaer频度和种间Spearman轶相关,探讨群落组成与水环境因子的相关性,并结合近10年来涠洲岛造礁石珊瑚变化情况,找出涠洲岛造礁石珊瑚群落的主导影响因素。结果表明:(1)近10年来涠洲岛造礁石珊瑚覆盖率显著降低,珊瑚形态组成趋于块状化,尽管珊瑚群落多样性较高,但群落分布较松散,群落结构较不稳定,部分优势种种间竞争较激烈。(2)悬浮物含量是影响石珊瑚群落最显著的环境因子。石珊瑚优势种群在不同水深中分布差异显著,泥沙覆盖率、营养盐对不同石珊瑚种群影响差异较大,大型海藻覆盖率在局部区域对优势珊瑚形成较强的竞争关系。(3)营养盐和泥沙沉积物的增加与涠洲岛近海养殖业及生活排污、海岸工程及海岸侵蚀密切相关。 相似文献
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Sexual vs. asexual reproduction in an ecosystem engineer: the massive coral Montastraea annularis 总被引:1,自引:0,他引:1
1. Long-lived sedentary organisms with a massive morphology are often assumed to utilize a storage effect whereby the persistence of a small group of adults can maintain the population when sexual recruitment fails. However, employing storage effects could prove catastrophic if, under changing climatic conditions, the time period between favourable conditions becomes so prolonged that the population cannot be sustained solely be sexual recruitment. When a species has multiple reproductive options, a rapidly changing environment may favour alternative asexual means of propagation. 2. Here, we revisit the importance of asexual dispersal in a massive coral subject to severe climate-induced disturbance. Montastraea annularis is a major framework-builder of Caribbean coral reefs but its survival is threatened by the increasing cover of macroalgae that prevents settlement of coral larvae. 3. To estimate levels of asexual recruitment within populations of M. annularis, samples from three sites in Honduras were genotyped using four, polymorphic microsatellite loci. 4. A total of 114 unique genets were identified with 8% consisting of two or more colonies and an exceptionally large genet at the third site comprising 14 colonies. 5. At least 70% of multicolony genets observed were formed by physical breakage, consistent with storm damage. 6. Our results reveal that long-lived massive corals can propagate using asexual methods even though sexual strategies predominate. 相似文献
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Endosymbiotic dinoflagellates in the genus Symbiodinium are among the most abundant and important group of photosynthetic protists found in coral reef ecosystems.In order to further characterize this diversity and compare with other regions of the Pacific,samples from 44 species of scleractinian corals representing 20 genera and 9 families,were collected from tropical reefs in southern Hainan Island,China.Denaturing gradient gel electrophoresis fingerprinting of the ribosomal internal transcribed spacer 2 identified 11 genetically distinct Symbiodinium types that have been reported previously.The majority of reef-building coral species (88.6%) harbored only one subcladal type of symbiont,dominated by host-generalist C1 and C3,and was influenced little by the host’s apparent mode of symbiont acquisition.Some species harbored more than one clade of Symbiodinium (clades C,D) concurrently.Although geographically isolated from the rest of the Pacific,the symbiont diversity in southern Hainan Island was relatively low and similar to both the Great Barrier Reef and Hawaii symbiont assemblages (dominated by clade C Symbiodinium).These results indicate that a specialist symbiont is not a prerequisite for existence in remote and isolated areas,but additional work in other geographic regions is necessary to test this idea. 相似文献
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The perennially ice-covered lakes of Antarctica have hydrodynamically stable water columns with a number of vertically distinct phytoplankton populations. We examined the photosynthesis-irradiance characteristics of phytoplankton from four depths of Lake Bonney to determine their physiological condition relative to vertical gradients in irradiance and temperature. All populations studied showed evidence of extreme shade adaptation, including low Ik values (15–45 μE · m?2· s?1) and extremely low maximal photosynthetic rates (PBm less than 0.3 μg C ·μg chl a?1· h?1). Photosynthetic rates were controlled by temperature as well as light variations with depth. Lake Bonney has an inverted temperature profile within the trophogenic zone that increased from 0° C at the ice-water interface to 6° C from 10 to 18 m. Deeper phytoplankton (10 m and 17 m) were found to have photosynthetic capacities (PBm) and efficiences (α) three to five times higher than those at the ice-water interface. However, Q10 values were only ca. 2 for PBm (no temperature dependence was evident for α), suggesting that a simple temperature response cannot explain all the differences between populations. Lake Bonney phytoplankton (primarily cryptophytes and chlorophytes) had photosynthetic characteristics similar to diatoms from other physically stable environments (e.g. sea ice, benthos) and may be ecologically analogous to multiple deep chlorophyll maxima. 相似文献
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造礁石珊瑚对低温的耐受能力及响应模式 总被引:4,自引:0,他引:4
通过实验室生态模拟,研究了低温胁迫下三亚湾5种造礁石珊瑚(十字牡丹珊瑚、佳丽鹿角珊瑚、花鹿角珊瑚、强壮鹿角珊瑚、澄黄滨珊瑚)的耐受性,分析了造礁石珊瑚对低温的响应模式.结果表明:造礁石珊瑚耐受低温能力与其骨骼类型有关,枝状珊瑚最先死亡,块状珊瑚的耐受能力明显高于枝状珊瑚;14 ℃持续3 d是三亚湾枝状造礁石珊瑚的致死低温;14 ℃持续3 d为块状澄黄滨珊瑚的致白化低温;12 ℃持续10 d为叶片状十字牡丹珊瑚的致死温度;块状澄黄滨珊瑚受到低温胁迫时表面形成粘膜,阻止了珊瑚进一步排出共生虫黄藻. 耐高温的珊瑚对低温也表现出较强的耐受能力,珊瑚对低温胁迫的响应模式与对高温的响应模式基本一致, 即珊瑚首先不伸展触手,紧接着不断释放粘液并排出共生藻,最后白化、死亡. 相似文献