Temporal consistency of ontogenetic shifts in habitat use by coral reef fishes in the northernmost coral ecosystem in the world (Kudaka Island, Japan)

The prevalence of major habitat shifts in tropical fishes between juvenile and adult stages (ontogenetic shifts) in one of the northernmost coral reefs in the world (Kudaka Island, Japan) is given. The comparative analysis of spatial distribution of juveniles v . adults highlighted four ontogenetic patterns: no change in habitat use between juveniles and adults (five species), a decrease in the number of habitats used by adults compared to juveniles (three species), an increase in the number of habitats used during the adult stage (four species) and use of nursery areas by juveniles followed by extensive movements to different adult habitats (three species). The comparative analysis of fish distribution over time ( i.e. during three consecutive settlement months) showed that 84% of species had temporal consistency in ontogenetic patterns of habitat use.     

Declines in the abundance of Chaetodon butterflyfishes following extensive coral depletion

This study documented temporal variation in the abundance of butterflyfishes (Chaetodontidae) at Trunk Reef, on the central Great Barrier Reef, Australia, from May 2000 to March 2005. During this period, live coral cover declined by >90%, mostly due to severe coral bleaching. There were no short-term changes (within 4 months) in the abundance of butterflyfishes following initial declines in live coral cover. Surveys conducted in 2005, however, revealed significant declines in the abundance of Chaetodon baronessa , Chaetodon lunulatus , Chaetodon trifascialis, Chaetodon plebeius and Chaetodon rainfordi , all of which are obligate hard-coral feeders. In contrast, there was no significant change in the abundance of Chaetodon auriga , Chaetodon aureofasciatus , Chaetodon citrinellus , Chaetodon melannotus or Chaetodon vagabundus , which are much less reliant on scleractinian coral for food. Clearly, extensive coral depletion, such as that caused by severe coral bleaching, can have a major effect on the abundance of butterflyfishes. Specific responses of butterflyfishes varied according to their reliance on hard corals for food and their ability to utilize alternate prey types.     

Phase shifts in coral reef communities and their ecological significance

Many coral reefs around the world have degraded to a degree that their present intrinsic value and utility are greatly reduced: (mass coral mortality followed by algal invasions; local depletions of reef fisheries; deficit of reef accretion compared to physical and biological erosion). Though we can sometimes identify proximal causes (outbreaks of coral predators and eroders; over-fishing; habitat destruction), we do not have a good understanding of how population, community and ecosystem structure and function differ in degraded from un-degraded reefs. The deficiencies in our understanding limit our ability to interpret the long-term significance of reef degradation, and therefore to develop scientifically based plans for conservation and management of reefs.A particular course of action, or lack of action, based on uncritical acceptance of any of the various views of temporal variability can lead to further deterioration of specific reefs. None of these views — that reefs are either inherently robust, inherently fragile, or inherently resilient — is true over all time-space scales. This presentation reviews various models and case studies which suggest that reefs can be knocked precipitously or move slowly from one phase (coral-dominated) to another (coral-depleted and/or algal dominated). Transitions in the other direction (recovery) involve changes (e.g. succession) in populations and communities (of all reef-associated biota, not just sessile benthos), and in reef function (e.g. community metabolism, trophodynamics) which are of great intrinsic interest but only poorly understood.     

Species-specific habitat distribution of coral reef fish assemblages in relation to habitat characteristics in an Okinawan coral reef

We determined the species-specific habitat associations of coral reef fishes and environmental characteristics in an Okinawan coral reef in Japan. We focused on three families (Pomacentridae, Gobiidae and Labridae) and attempted to determine differences in habitat utilization. We selected six sites along the coast of Amitori Bay, from the entrance to the innermost part, in order to cover a wide range of habitat characteristics (exposed habitat, semi-exposed habitat and sheltered habitat). The species diversity of coral assemblages was greater at the exposed and semi-exposed habitats, whereas branching coral mostly covered the sheltered habitat. The environmental factors that determine the species-specific spatial association in fishes differed among families. Both biological characteristics (coral morphology and coral species diversity) and physical characteristics (water depth and wave exposure) affected the spatial association of pomacentrids and gobiids. In contrast, physical characteristics such as substrate complexity and water depth affected the species-specific spatial association of labrid species. Further study is needed to determine the ecological factors that regulate the species-specific habitat preference in Okinawan coral reefs.     

Marine protected areas increase resilience among coral reef communities

With marine biodiversity declining globally at accelerating rates, maximising the effectiveness of conservation has become a key goal for local, national and international regulators. Marine protected areas (MPAs) have been widely advocated for conserving and managing marine biodiversity yet, despite extensive research, their benefits for conserving non‐target species and wider ecosystem functions remain unclear. Here, we demonstrate that MPAs can increase the resilience of coral reef communities to natural disturbances, including coral bleaching, coral diseases, Acanthaster planci outbreaks and storms. Using a 20‐year time series from Australia's Great Barrier Reef, we show that within MPAs, (1) reef community composition was 21–38% more stable; (2) the magnitude of disturbance impacts was 30% lower and (3) subsequent recovery was 20% faster that in adjacent unprotected habitats. Our results demonstrate that MPAs can increase the resilience of marine communities to natural disturbance possibly through herbivory, trophic cascades and portfolio effects.     

Vulnerability of global coral reef habitat suitability to ocean warming,acidification and eutrophication

Coral reefs are threatened by global and local stressors. Yet, reefs appear to respond differently to different environmental stressors. Using a global dataset of coral reef occurrence as a proxy for the long‐term adaptation of corals to environmental conditions in combination with global environmental data, we show here how global (warming: sea surface temperature; acidification: aragonite saturation state, Ω_arag) and local (eutrophication: nitrate concentration, and phosphate concentration) stressors influence coral reef habitat suitability. We analyse the relative distance of coral communities to their regional environmental optima. In addition, we calculate the expected change of coral reef habitat suitability across the tropics in relation to an increase of 0.1°C in temperature, an increase of 0.02 μmol/L in nitrate, an increase of 0.01 μmol/L in phosphate and a decrease of 0.04 in Ω_arag. Our findings reveal that only 6% of the reefs worldwide will be unaffected by local and global stressors and can thus act as temporary refugia. Local stressors, driven by nutrient increase, will affect 22% of the reefs worldwide, whereas global stressors will affect 11% of these reefs. The remaining 61% of the reefs will be simultaneously affected by local and global stressors. Appropriate wastewater treatments can mitigate local eutrophication and could increase areas of temporary refugia to 28%, allowing us to ‘buy time’, while international agreements are found to abate global stressors.     

Coral reef mesopredators switch prey,shortening food chains,in response to habitat degradation

Diet specificity is likely to be the key predictor of a predator's vulnerability to changing habitat and prey conditions. Understanding the degree to which predatory coral reef fishes adjust or maintain prey choice, in response to declines in coral cover and changes in prey availability, is critical for predicting how they may respond to reef habitat degradation. Here, we use stable isotope analyses to characterize the trophic structure of predator–prey interactions on coral reefs of the Keppel Island Group on the southern Great Barrier Reef, Australia. These reefs, previously typified by exceptionally high coral cover, have recently lost much of their coral cover due to coral bleaching and frequent inundation by sediment‐laden, freshwater flood plumes associated with increased rainfall patterns. Long‐term monitoring of these reefs demonstrates that, as coral cover declined, there has been a decrease in prey biomass, and a shift in dominant prey species from pelagic plankton‐feeding damselfishes to territorial benthic algal‐feeding damselfishes, resulting in differences in the principal carbon pathways in the food web. Using isotopes, we tested whether this changing prey availability could be detected in the diet of a mesopredator (coral grouper, Plectropomus maculatus). The δ¹³C signature in grouper tissue in the Keppel Islands shifted from a more pelagic to a more benthic signal, demonstrating a change in carbon sources aligning with the change in prey availability due to habitat degradation. Grouper with a more benthic carbon signature were also feeding at a lower trophic level, indicating a shortening in food chains. Further, we found a decline in the coral grouper population accompanying a decrease in total available prey biomass. Thus, while the ability to adapt diets could ameliorate the short‐term impacts of habitat degradation on mesopredators, long‐term effects may negatively impact mesopredator populations and alter the trophic structure of coral reef food webs.     

热带珊瑚礁区海参的生境选择与生态作用

珊瑚礁生态系统是一个高生产力、高生物多样性的特殊海洋生态系统,具有为生物提供栖息地、参与生物地球化学循环、防浪护岸、指示水体污染程度等生态功能。珊瑚礁生态系统的突出特点是其生境异质性很高,各种各样的生境斑块为种类繁多、习性各异的游泳和底栖生物提供栖息场所,这些礁栖生物通过参与各项生态过程而形成各种特定的功能群,共同完成重要的生态功能。在热带珊瑚礁生态系统中,海参是大型底栖动物区系的重要一员。种类繁多的海参具有各自不同的生境选择特征,通过摄食、运动等行为活动发挥着改良底质、促进有机物矿化和营养盐再生等生态作用。近几年来,全球热带海参受人类过度捕捞和珊瑚礁退化的影响而面临资源衰退、物种多样性丧失等问题,深入认识其生态学功能、加强热带海参资源保护迫在眉睫。综述了国内外热带珊瑚礁海参的基础生态学研究进展：海参对珊瑚礁生境斑块呈现显著的偏好选择特征以及种间差异和季节变动,不同生境斑块的食物质量、底质类型和水动力条件是影响海参生境偏好的重要因素;海参通过生物扰动可以改变珊瑚礁生境沉积物的含水量、渗透性、颗粒组成、再矿化率、无机营养物质释放速率以及孔隙水的化学梯度,并增加沉积物中的溶氧浓度、促进溶解...     

Increased CO2 stimulates reproduction in a coral reef fish

Ocean acidification is predicted to negatively impact the reproduction of many marine species, either by reducing fertilization success or diverting energy from reproductive effort. While recent studies have demonstrated how ocean acidification will affect larval and juvenile fishes, little is known about how increasing partial pressure of carbon dioxide (pCO₂) and decreasing pH might affect reproduction in adult fishes. We investigated the effects of near‐future levels of pCO₂ on the reproductive performance of the cinnamon anemonefish, Amphiprion melanopus, from the Great Barrier Reef, Australia. Breeding pairs were held under three CO₂ treatments [Current‐day Control (430 μatm), Moderate (584 μatm) and High (1032 μatm)] for a 9‐month period that included the summer breeding season. Unexpectedly, increased CO₂ dramatically stimulated breeding activity in this species of fish. Over twice as many pairs bred in the Moderate (67% of pairs) and High (55%) compared to the Control (27%) CO₂ treatment. Pairs in the High CO₂ group produced double the number of clutches per pair and 67% more eggs per clutch compared to the Moderate and Control groups. As a result, reproductive output in the High group was 82% higher than that in the Control group and 50% higher than that in the Moderate group. Despite the increase in reproductive activity, there was no difference in adult body condition among the three treatment groups. There was no significant difference in hatchling length between the treatment groups, but larvae from the High CO₂ group had smaller yolks than Controls. This study provides the first evidence of the potential effects of ocean acidification on key reproductive attributes of marine fishes and, contrary to expectations, demonstrates an initially stimulatory (hormetic) effect in response to increased pCO₂. However, any long‐term consequences of increased reproductive effort on individuals or populations remain to be determined.     

Body size determines eyespot size and presence in coral reef fishes

Numerous organisms display conspicuous eyespots. These eye‐like patterns have been shown to effectively reduce predation by either deflecting strikes away from nonvital organs or by intimidating potential predators. While investigated extensively in terrestrial systems, determining what factors shape eyespot form in colorful coral reef fishes remains less well known. Using a broadscale approach we ask: How does the size of the eyespot relate to the actual eye, and at what size during ontogeny are eyespots acquired or lost? We utilized publicly available images to generate a dataset of 167 eyespot‐bearing reef fish species. We measured multiple features relating to the size of the fish, its eye, and the size of its eyespot. In reef fishes, the area of the eyespot closely matches that of the real eye; however, the eyespots “pupil” is nearly four times larger than the real pupil. Eyespots appear at about 20 mm standard length. However, there is a marked decrease in the presence of eyespots in fishes above 48 mm standard length; a size which is tightly correlated with significant decreases in documented mortality rates. Above 75–85 mm, the cost of eyespots appears to outweigh their benefit. Our results identify a “size window” for eyespots in coral reef fishes, which suggests that eyespot use is strictly body size‐dependent within this group.     

珊瑚礁白化研究进展

珊瑚礁白化是由于珊瑚失去体内共生的虫黄藻和（或）共生的虫黄藻失去体内色素而导致五彩缤纷的珊瑚礁变白的生态现象。近年来,频繁发生的珊瑚礁白化导致了珊瑚礁生态系统严重退化,并已经影响到全球珊瑚礁生态系统的平衡,受到了人们的高度重视。研究认为：（1）大范围珊瑚礁白化主要是全球环境变化引起的,尤其是全球变暖和紫外辐射增强;（2）导致珊瑚礁白化的机制主要在于细胞机制和光抑制机制;（3）珊瑚礁白化后的恢复与白化程度有关,大范围白化的珊瑚礁完全恢复需要几年到几十年;（4）珊瑚礁白化的后果在于降低珊瑚繁殖能力、减缓珊瑚礁生长、改变礁栖生物的群落结构,导致大面积珊瑚死亡和改变珊瑚礁生态类型,如变为海藻型等;（5）与珊瑚共生的D系群虫黄藻更适应高温环境,珊瑚礁有可能通过D系群逐渐取代C系群的方式适应全球环境变化。     

The ecological significance of the combtoothed blenny in a coral reef ecosystem

At Heron Island reef, Great Barrier Reef Australia, biomass densities and mean wet mass of Ward's damselfish Pomacentrus wardi and the jewelled blenny Salarias fasciatus were not significantly different at 2·37 v . 2·95 g m⁻² and 8·7 v . 7·9 g, respectively. Whereas S. fasciatus significantly exceeded P. wardi in (1) total number of bites per day (3427 v . 1155), (2) the mass of epilithic algal community consumed per bite (2·19 v . 0·14 mg) and (3) total organic carbon consumed per day (487·31 v . 35·46 mg C m⁻² day⁻¹). Territorial behaviour differed also between the two species. Pomacentrus wardi chased from their territories a smaller proportion of blennies than roving grazers ( i.e . scarids, acanthurids, siganids and pomacentrids) relative to S. fasciatus . Salarias fasciatus chased c . 90% of other blennies from their territories, while chasing only c . 20% of all damsels that entered. Both P. wardi and S. fasciatus rarely chased non‐grazers. The chasing behaviour of S. fasciatus was size dependent, with resident fish chasing only individuals of its own family ( i.e . Blenniidae) that were the same or smaller size. Pomacentrus wardi may have tolerated S. fasciatus grazing within its territory, as it contributes to territory defence from other blennies. The possibility that the interaction between the two species is facilitative, rather than competitive, is discussed. It was concluded that salariine blennies play an important, and previously underestimated role in coral reef trophodynamics.     

The impact of CO2 emission scenarios and nutrient enrichment on a common coral reef macroalga is modified by temporal effects

Future coral reefs are expected to be subject to higher pCO₂ and temperature due to anthropogenic greenhouse gas emissions. Such global stressors are often paired with local stressors thereby potentially modifying the response of organisms. Benthic macroalgae are strong competitors to corals and are assumed to do well under future conditions. The present study aimed to assess the impact of past and future CO₂ emission scenarios as well as nutrient enrichment on the growth, productivity, pigment, and tissue nutrient content of the common tropical brown alga Chnoospora implexa. Two experiments were conducted to assess the differential impacts of the manipulated conditions in winter and spring. Chnoospora implexa's growth rate averaged over winter and spring declined with increasing pCO₂ and temperature. Furthermore, nutrient enrichment did not affect growth. Highest growth was observed under spring pre‐industrial (PI) conditions, while slightly reduced growth was observed under winter A1FI (“business‐as‐usual”) scenarios. Productivity was not a good proxy for growth, as net O₂ flux increased under A1FI conditions. Nutrient enrichment, whilst not affecting growth, led to luxury nutrient uptake that was greater in winter than in spring. The findings suggest that in contrast with previous work, C. implexa is not likely to show enhanced growth under future conditions in isolation or in conjunction with nutrient enrichment. Instead, the results suggest that greatest growth rates for this species appear to be a feature of the PI past, with A1FI winter conditions leading to potential decreases in the abundance of this species from present day levels.     

An analysis of fish‐habitat associations on disturbed coral reefs: chaetodontid fishes in New Caledonia

A concordance analysis was used to study the simultaneous influence of several environmental data sets on chaetodontid (butterflyfish) distributions. This multivariate and multitable method enabled the correlation of three types of benthic characteristics (mineral substratum, coverage of structural species and large echinoderms) with butterflyfish abundances in two bays of the urban centre of Nouméa (New Caledonia). The first concordance axis was related to a gradient in the coverage of branching corals. This disturbance gradient compared damaged reef areas dominated by long‐spined sea urchins to areas with an extensive coverage of branching corals. The abundance of corallivorous chaetodontids was related to this gradient, supporting the view of corals as a food and shelter source for these fishes. The second concordance axis was interpreted as a gradient of heterogeneity in the coverage of benthic life‐forms. The abundance of omnivorous chaetodontids was related to this gradient. Thus, the concordance axes defined two key components of habitat structure that were related to the entire fish community structure.     

In situ observation of settlement behaviour in larvae of coral reef fishes at night

The swimming behaviour of 534 coral reef fish larvae from 27 species was explored at Moorea Island (French Polynesia) while they searched for a suitable settlement habitat, on the first night of their lagoon life. Most larvae swam actively (74%) and avoided the bottom (77%). A significant relationship was highlighted between the vertical position of larvae in the water column and the distance they travelled from lagoon entrance to settlement habitat: larvae swimming close to the surface settled farther away on the reef than bottom-dwelling larvae.     

微生物在珊瑚礁生态系统中的作用与功能

珊瑚礁是由珊瑚、鱼类、底栖生物、藻类以及微生物等多种生命形式组成的聚集体,代表着一类典型的海洋生态系统.珊瑚礁存在于热带和亚热带的寡营养环境,拥有极高的初级生产力和生产效率,被誉为“海底热带雨林”.微生物在珊瑚礁生态系统的生物地球化学循环、物质转化以及健康维护上具有重要作用.随着分子生态学的发展,微生物在珊瑚中的作用和功能日益凸显.本文总结了微生物生态学的研究现状,包括珊瑚生态系统中微生物的定植方式,共生微生物的特性(专一性、可塑性、协同进化),共生微生物与珊瑚疾病的关系与信号调节,以及微生物应对全球变化(气温升高、海水酸化、富营养化)的响应.从“珊瑚 微生物”共生体的发生、共生微生物的特性与生态功能,以及全球环境变化下微生物的衍生效应来梳理最新理论与成果,明确珊瑚微生物生态学机制,为更好地保护珊瑚资源、维护海洋生物多样性提供理论借鉴.     

Near‐term impacts of coral restoration on target species,coral reef community structure,and ecological processes

The global decline of corals has created an urgent need for effective, science‐based methods to augment coral populations and restore important ecosystem functions. To meet this challenge, the field of coral restoration has rapidly evolved over the past decade. However, despite widespread efforts to outplant corals and monitor survivorship, there is a shortage of information on the effects of coral restoration on reef communities or important ecosystem functions. To fill this knowledge gap, we examined the effects of restoration on three major criteria: diversity, community structure, and ecological processes. We conducted surveys of four restored sites in the Florida Keys ranging in restoration effort (500–2,300 corals outplanted) paired with surveys of nearby, unmanipulated control sites. Coral restoration successfully enhanced coral populations, increasing coral cover 4‐fold, but manifested in limited differences in coral and fish communities. Some restored sites had higher abundance of herbivorous fish, rates of herbivory, or more juvenile‐sized corals, but these effects were limited to individual reefs. Damselfish were consistently more abundant at restored compared to control sites. Despite augmenting target coral populations, 3 years of coral restoration has not facilitated many of the positive feedbacks that help reinforce coral success. In a time of increasingly frequent disturbances, it is urgent we hasten the speed at which reefs recover important ecological processes, such as herbivory and nutrient cycling, that make reefs more resistant and resilient if we are to achieve long‐term restoration success.