Archetypal ‘elkhorn’ coral discovered in the Pacific Ocean

The discovery of a population of elkhorn corals in the Central Pacific Ocean has important taxonomic implications, as this distinctive colony morphology was previously known only from the endemic and critically endangered Atlantic species Acropora palmata. Phylogenetic analyses confirmed that the Pacific elkhorn coral is genetically distant from A. palmata, and most likely represents a species previously synonymized with Acropora abrotanoides. The Pacific elkhorn coral is rare, and is of particular scientific interest because it represents one morphological extreme in the dominant genus of reef-building corals. The discovery of the Pacific elkhorn coral raises a number of important general issues in relation to biodiversity conservation, as this coral would not qualify for threatened species listing under current IUCN categories and criteria despite being demonstrably rare.     

珊瑚及共生藻在白化过程中的适应机制研究进展

珊瑚礁生态系统具有非常重要的生态学功能。但是随着全球气候变暖和CO2浓度的升高,珊瑚白化事件越来越频繁,珊瑚礁生态系统面临严重的危机。影响珊瑚白化的重要因子主要有海水温度的异常（过高或过低）,太阳辐射与紫外线辐射,海水盐度的偏离,珊瑚疾病,海洋污染,长棘海星的爆发,人类的过度捕鱼和全球CO2浓度升高等。其中,海洋表面水体温度（SST）的异常升高为珊瑚白化的主要因素。珊瑚主要是通过珊瑚与共生藻的生理适应机制以及更换共生藻基因型机制两种方式来适应环境胁迫的。生理适应机制主要通过叶黄素循环、珊瑚色素荧光（热）、活性氧清除系统（自由基）、分泌紫外线吸收物质MAAs（紫外光）、产生热休克蛋白HspS（热）来实现的。珊瑚共生藻基因型更换适应机制是指珊瑚的适应性白化假说。珊瑚的适应性白化假说还有很多争议,还需要更多的实验证据提供支持。未来的研究重点将在珊瑚白化过程中共生藻-珊瑚共生功能体作为整体性的研究,尤其是珊瑚宿主在白化过程中对共生功能体作出贡献的研究。     

Spatial patterns of self‐recruitment of a coral reef fish in relation to island‐scale retention mechanisms

Oceanographic features influence the transport and delivery of marine larvae, and physical retention mechanisms, such as eddies, can enhance self‐recruitment (i.e. the return of larvae to their natal population). Knowledge of exact locations of hatching (origin) and settlement (arrival) of larvae of reef animals provides a means to compare observed patterns of self‐recruitment ‘connectivity’ with those expected from water circulation patterns. Using parentage inference based on multiple sampling years in Moorea, French Polynesia, we describe spatial and temporal variation in self‐recruitment of the anemonefish Amphiprion chrysopterus, evaluate the consistency of net dispersal distances of self‐recruits against the null expectation of passive particle dispersal and test the hypothesis that larvae originating in certain reef habitats (lagoons and passes) would be retained and thus more likely to self‐recruit than those originating on the outer (fore) reef. Estimates of known self‐recruitment were consistent across the sampling years (~25–27% of sampled recruits). For most (88%) of these self‐recruits, the net distance between hatching and settlement locations was within the maximum dispersal distance expected for a neutrally buoyant passive particle based on the longest duration of the larval dispersive phase and the average direction and speed of current flow around Moorea. Furthermore, a parent of a given body size on the outer (fore) reef of Moorea was less likely to produce self‐recruits than those in passes. Our findings show that even a simple dispersal model based on net average flow and direction of alongshore currents can provide insight into landscape‐scale retention patterns of reef fishes.     

Composition of lipids, fatty acids and sterols in Okinawan corals

A survey of lipid composition was made for 15 cnidarians from Okinawa, Japan. Eleven zooxanthellate scleractinian corals, an azooxanthellate scleractinian coral Tubastrea sp., a soft coral Lobophytum crassum, a hydroid coral Millepora murrayi and a sea anemone Boloceroides sp. were examined to elucidate the total lipid content, fatty acid composition for each lipid class and sterol composition. All specimens contained monoalkyldiacylglycerol which migrated between the triacylglycerols and esters on thin layer chromatography (TLC). Analysis by high performance thin layer chromatography (HPTLC) and Gas chromatography-mass spectrometry (GC-MS) revealed that these cnidarians were rich in wax ester and triacylglycerol, and that palmitic acid (16:0) was the most abundant fatty acid component of these lipid classes, followed by stearic (18:0) and oleic (18:1, n-9) acid in order of concentration. Of 11 sterols separated, four sterols were identified. It is suggested that sterol composition may be more useful for the biochemical classification of these cnidarians than fatty acid composition.     

西沙珊瑚礁生态系统完整性评价与动态仿真模拟研究

以中国西沙珊瑚礁生态监控区为例,从生态系统完整性视角出发,结合珊瑚礁功能群组与环境变化的多重反馈效应,运用系统动力学方法构建了西沙珊瑚礁生态系统动态诊断模型,并通过基础情景和典型干扰情景（捕捞活动、陆源沉积、长棘海星（Acanthaster planci）暴发）的模拟过程,分析该生态监控区2010-2050年生态系统完整性的发展趋势及演变机理。结果显示：（1）系统动力学与生态系统完整性评价方法的整合,为珊瑚礁生态系统完整性的定量研究提供了一种可行性的方法;（2）珊瑚礁生态系统各效应指数中累积效应的变化最为明显,2010-2050年指数最大增长17.2,年均增长率约为1.2%,综合完整性指数在波动变化中稳步上升,珊瑚礁受损程度由中受损向中、低受损转变;（3）不同状态的珊瑚礁生态系统完整性,在其演化的不同阶段各有差异性,并且这种差异通常随时间推移才逐渐放大;（4）无论何种情景下,珊瑚礁生态系统都具有一定的恢复能力,尤其处于系统演化的释放重组阶段（2035-2040年）,生态系统的不稳定将创造了一定的可恢复性。研究结果对于分析西沙珊瑚礁生态系统的整体演化过程提供了理论借鉴,也为我国后续的珊瑚礁生态系统适应性修复理论模式研究提供了重要的基础。     

Corals escape bleaching in regions that recently and historically experienced frequent thermal stress

The response of coral-reef ecosystems to contemporary thermal stress may be in part a consequence of recent or historical sea-surface temperature (SST) variability. To test this hypothesis, we examined whether: (i) there was a relationship between the historical frequency of SST variability and stress experienced during the most recent thermal-stress events (in 1998 and 2005–2006) and (ii) coral reefs that historically experienced frequent thermal anomalies were less likely to experience coral bleaching during these recent thermal-stress events. Examination of nine detrended coral δ¹⁸O and Sr/Ca anomaly records revealed a high- (5.7-year) and low-frequency (>54-year) mode of SST variability. There was a positive relationship between the historical frequency of SST anomalies and recent thermal stress; sites historically dominated by the high-frequency mode experienced greater thermal stress than other sites during both events, and showed extensive coral bleaching in 1998. Nonetheless, in 2005–2006, corals at sites dominated by high-frequency variability showed reduced bleaching, despite experiencing high thermal stress. This bleaching resistance was most likely a consequence of rapid directional selection that followed the extreme thermal event of 1998. However, the benefits of regional resistance could come at the considerable cost of shifts in coral species composition.     

Postsettlement movement patterns and homing in a coral-associated fish

Coral-associated gobies are highly specialized reef fishes withhigh host-coral fidelity. Flexibility in habitat choice, however,is important to compensate for potential habitat alterationor loss, but detailed information about the postsettlement movementbehavior of such gobies is lacking. We examined movement patternsin Gobiodon histrio, both under natural conditions and duringsubsequent field experiments, involving breeding pair or partnerremoval from 3 of the 4 investigation plots. Additionally, weinvestigated homing behavior, and 2 aquaria experiments weredesigned to assess home coral and partner recognition of adultfish taken from breeding pairs. Under natural conditions, themovement rate was high for single adults, whereas breeding pairsshowed high home-coral fidelity. Manipulations revealed littlechange of natural patterns except in single adults, which slightlydecreased their movement rate in the breeding pair removal plot.In the homing experiment, 17% of tested fish returned to theirhome coral even after displacement of 4 m, and homing successwas much higher at shorter distances (100% at 0.5 m, 53% at2.25 m). In the aquarium, G. histrio exhibited higher recognitionof its home-coral colony (75%) than of its breeding pair partner(60%). Our study shows that G. histrio frequently moves betweencorals, although this depends on the social status (juvenile,single adult, breeding pair) of the individuals. The high proportionand movement rate of single adults indicate low sensitivityto habitat alteration but also limited high-quality habitatsin which breeding pairs could be established. Hence, vulnerabilityto habitat loss increases when individuals breed.     

Hosts of the Plio-Pleistocene past reflect modern-day coral vulnerability

The risk of global extinction of reef-building coral species is increasing. We evaluated extinction risk using a biological trait-based resiliency index that was compared with Caribbean extinction during the Plio-Pleistocene, and with extinction risk determined by the International Union for Conservation of Nature (IUCN). Through the Plio-Pleistocene, the Caribbean supported more diverse coral assemblages than today and shared considerable overlap with contemporary Indo-Pacific reefs. A clear association was found between extant Plio-Pleistocene coral genera and our positive resilience scores. Regional extinction in the past and vulnerability in the present suggests that Pocillopora, Stylophora and foliose Pavona are among the most susceptible taxa to local and regional isolation. These same taxa were among the most abundant corals in the Caribbean Pliocene. Therefore, a widespread distribution did not equate with immunity to regional extinction. The strong relationship between past and present vulnerability suggests that regional extinction events are trait-based and not merely random episodes. We found several inconsistencies between our data and the IUCN scores, which suggest a need to critically re-examine what constitutes coral vulnerability.