Ecological persistence interrupted in Caribbean coral reefs

The recent mass mortality of Caribbean reef corals dramatically altered reef community structure and begs the question of the past stability and persistence of coral assemblages before human disturbance began. We report within habitat stability in coral community composition in the Pleistocene fossil record of Barbados for at least 95 000 years despite marked variability in global sea level and climate. Results were consistent for surveys of both common and rare taxa. Comparison of Pleistocene and modern community structure shows that Recent human impacts have changed coral community structure in ways not observed in the preceding 220 000 years.     

Structure of Caribbean coral reef communities across a large gradient of fish biomass

The collapse of Caribbean coral reefs has been attributed in part to historic overfishing, but whether fish assemblages can recover and how such recovery might affect the benthic reef community has not been tested across appropriate scales. We surveyed the biomass of reef communities across a range in fish abundance from 14 to 593 g m⁻², a gradient exceeding that of any previously reported for coral reefs. Increased fish biomass was correlated with an increased proportion of apex predators, which were abundant only inside large marine reserves. Increased herbivorous fish biomass was correlated with a decrease in fleshy algal biomass but corals have not yet recovered.     

《生物多样性公约》下我国珊瑚礁养护履约进程与改善建议

珊瑚礁生态系统是《生物多样性公约》(下称《公约》)的重点保护对象。自1998年珊瑚礁出现大规模白化现象以来, 珊瑚礁养护议题一直受到《公约》缔约方大会的关注。本文通过梳理我国珊瑚礁养护管理的法律法规和相关履约措施, 结合海南、广西、广东三省的珊瑚礁资源变化状况, 评价我国在履约方面的表现并识别存在的主要差距。研究发现, 总体上我国积极采取了多种措施进行珊瑚礁的养护和管理, 活珊瑚覆盖度和种类数量有一定程度的恢复, 但仍存在相关立法分散、综合性治理方案缺乏、气候变化适应不足、跨部门协调机制不完善、海洋保护区管理有效性不足、资金缺乏且当地社区参与度低、珊瑚礁监测标准和规范简单且不统一、监测数据不足以进行有效评估、国际合作程度低、公众参与度不高等问题。建议我国结合履约要求, 与《公约》的目标和精神基本保持一致, 并考虑正在讨论的《2020后全球生物多样性保护框架》, 进一步完善珊瑚礁养护立法、行动计划和气候变化适应方案, 加强综合管理和协调机制建设, 提升海洋保护区的管理实效性, 改进珊瑚礁监测和数据采集, 提升国际合作, 进一步提高公众参与度, 从而不断提升履约能力, 构建更加完善的珊瑚礁养护体系。     

A coral reef refuge in the Red Sea

The stability and persistence of coral reefs in the decades to come is uncertain due to global warming and repeated bleaching events that will lead to reduced resilience of these ecological and socio‐economically important ecosystems. Identifying key refugia is potentially important for future conservation actions. We suggest that the Gulf of Aqaba (GoA) (Red Sea) may serve as a reef refugium due to a unique suite of environmental conditions. Our hypothesis is based on experimental detection of an exceptionally high bleaching threshold of northern Red Sea corals and on the potential dispersal of coral planulae larvae through a selective thermal barrier estimated using an ocean model. We propose that millennia of natural selection in the form of a thermal barrier at the southernmost end of the Red Sea have selected coral genotypes that are less susceptible to thermal stress in the northern Red Sea, delaying bleaching events in the GoA by at least a century.     

Specialist corallivores dominate butterflyfish assemblages in coral‐dominated reef habitats

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.     

Multiple modes in a coral species abundance distribution

Species abundance distributions are an important measure of biodiversity and community structure. These distributions are affected by sampling, and alternative species-abundance models often make similar predictions for small sample sizes. Very large samples reveal the relative abundances of rare species, and thus provide information about species relative abundances that small samples cannot. Here, we present the species-abundance distribution for a sample of > 40,000 coral colonies at a single site, exceeding existing samples of coral local assemblages by over an order of magnitude. This abundance distribution is multimodal when examined on a logarithmic scale. Four different model selection procedures all indicate that the underlying community abundance distribution has at least three modes. We show that the multiple modes are not caused by mixtures of species with different habitat preferences. However, spatial aggregation partially explains our results. We inspect published work on species abundance distributions, and suggest that multimodality may be a common feature of large samples.     

Mass coral bleaching causes biotic homogenization of reef fish assemblages

Global climate change is altering community composition across many ecosystems due to nonrandom species turnover, typically characterized by the loss of specialist species and increasing similarity of biological communities across spatial scales. As anthropogenic disturbances continue to alter species composition globally, there is a growing need to identify how species responses influence the establishment of distinct assemblages, such that management actions may be appropriately assigned. Here, we use trait‐based analyses to compare temporal changes in five complementary indices of reef fish assemblage structure among six taxonomically distinct coral reef habitats exposed to a system‐wide thermal stress event. Our results revealed increased taxonomic and functional similarity of previously distinct reef fish assemblages following mass coral bleaching, with changes characterized by subtle, but significant, shifts toward predominance of small‐bodied, algal‐farming habitat generalists. Furthermore, while the taxonomic or functional richness of fish assemblages did not change across all habitats, an increase in functional originality indicated an overall loss of functional redundancy. We also found that prebleaching coral composition better predicted changes in fish assemblage structure than the magnitude of coral loss. These results emphasize how measures of alpha diversity can mask important changes in the structure and functioning of ecosystems as assemblages reorganize. Our findings also highlight the role of coral species composition in structuring communities and influencing the diversity of responses of reef fishes to disturbance. As new coral species configurations emerge, their desirability will hinge upon the composition of associated species and their capacity to maintain key ecological processes in spite of ongoing disturbances.     

Sustainable dive ecotourism on a South African coral reef

SCUBA ecotourism provides economic support for local human communities and for conservation. Such support should be sustainable and as ecologically non-destructive as possible to its coral reef foundation. In recent years, the major increase in SCUBA activity has become a significant consideration at some locations. Among these are the South African coral reefs at Sodwana Bay, which receive 80 000 dives per year. Between May 1998 and January 1999, assessments using line-intercept and belt transects showed that 5.9% of hard corals and 4.0% of soft corals were damaged from various causes, while only 0.02% of the hard corals were dead. Of the 222 diver contacts observed, only 1.63% produced instant and visually-clear damage, with no measurable decline in overall coral reef health. Direct observations on 89 recreational divers showed that photographers made damaging contacts on nine out of ten dives, while novice divers made one such contact per six dives, moderately experienced divers about once every 14 dives, and very experienced divers about once every 123 dives. Increased time lapsed since the last dive increased diver damage by novices. We calculated that the 80 000 dives were equivalent to 1 m² of reef receiving 2.3 diver contacts per year. Acropora austera was by far the most significantly damaged coral, with one out of four branches broken per year. But as this species accounted for only 0.2% of reef benthos cover, this impact was not representative of overall reef health. This heavy species-specific impact makes A. austera a good bio-monitor.     

Vertical zonation of coral reef fishes in the Sudanese Red Sea

The vertical zonation of 38 species of fish inhabiting coral reefs in the Sudanese Red Sea is described. A marked degree of vertical zonation of the fishes is shown to exist. The usefulness of a depth oriented survey method for studying reef fish is discussed in relation to these results.General relationships between vertical zonation and species diversity are noted.     

三亚珊瑚礁水域纤毛虫种类组成和数量分布及与环境因子的关系

2004年8月通过对三亚珊瑚礁水域纤毛虫进行表、底层采集分析,共鉴定6纲14目33属58种浮游纤毛虫,其中旋毛纲41种,叶口纲6种,寡膜纲5种,叶咽纲4种,前口纲和伪纤毛纲各1种。在14个目中,以旋毛纲环毛亚纲砂壳目纤毛虫种类最多,达到31种。主要优势种为布氏拟铃虫 Tintinnopsis bütschlii、小拟铃虫 Tintinnopsis minuta、丁丁急游虫Strombidium tintinnodes和具沟急游虫Strombidium sulcatum等,底层纤毛虫数量和种类都较表层高,底、表层平均丰度分别为375个/L和346 个/L,表、底层纤毛虫种类差异明显,表层主要由浮游纤毛虫组成,以旋毛纲环毛亚纲砂壳目纤毛虫为主,急游目纤毛虫次之;而底层主要由缘毛目组成,如长圆靴纤虫 Cothurnia oblonga、透明鞘居虫Vaginicola crystalline、钟虫Vorticella sp.以及吸管目的壳吸管虫 Acineta sp. 等。结果显示,在活珊瑚覆盖率高的站位（S4,S7和S9）纤毛虫数量明显低于珊瑚覆盖率低或没有珊瑚覆盖的站位,这暗示了珊瑚对纤毛虫的摄食作用。典型对应分析结果表明,影响三亚湾海域纤毛虫分布的主要因素有Chla、颗粒悬浮物SS和活性磷,以及水体溶解有机碳含量。通过对纤毛虫数量与环境因子关系的分析表明,三亚湾珊瑚礁水域纤毛虫的数量与叶绿素呈明显的正相关性。     

Positive indirect effects in a coral reef fish community

Indirect effects occur when two species interact through one or more intermediate species. Theoretical studies indicate that indirect interactions between two prey types that share common predators can be positive, neutral or negative. We document a positive indirect interaction between different types of prey fish on coral reefs in Australia. A high abundance of one type of prey fish (cardinalfishes: Apogonidae) resulted in higher recruitment, abundance and species richness of other prey fish. Our evidence indicates that these effects were not due to differential settlement but were instead due to differential post-settlement predation. We hypothesize that resident piscivores altered their foraging behaviour by concentrating on highly abundant cardinal-fish when they were present, leaving recruits of other species relatively unmolested. Indirect effects were evident within 48 h of settlement and persisted throughout the 42-day experiment, highlighting the importance of early post-settlement processes in these communities.     

Habitat utilization by coral reef fish: implications for specialists vs. generalists in a changing environment

1. The impact of environmental disturbance and habitat loss on associated species is expected to be dependent on a species' level of specialization. We examined habitat use and specialization of coral reef fish from the diverse and ecologically important family Pomacentridae, and determined which species are susceptible to declines in coral cover due to disturbance induced by crown-of-thorns seastar (COTS, Acanthaster planci L.). 2. A high proportion of pomacentrid species live in association with live coral as adults (40%) or juveniles (53%). Adults of many species had strong affiliations with branching corals, while juveniles favoured plating growth forms, reflecting the sizes of refuge provided by coral types. 3. Juveniles of species that associated with coral had narrower niche breadths than adult conspecifics, due to associations with specific coral types. The especially high coral association and narrower niche breadth of juveniles suggest that the presence of live coral is crucial for many species during early life history, and that disturbance-induced coral loss may have serious flow-on effects on adult abundance. 4. Microhabitat availability was a poor predictor of fish species abundance. Significant correlations between coverage of coral types and abundance of five adults and two juvenile species were detected; however, these relationships explained <35% and <10% of the variation in abundance of adult and juvenile species, respectively. 5. Niche breadth explained 74% of the variation in species' mean response to coral decline and it is clear that disturbance has a greater impact on resource specialists, suggesting that increasing frequency and intensity of coral loss will cause reef fish communities to become dominated by habitat generalists at the expense of coral-dwelling specialists.     

珊瑚礁生态系统病毒研究进展

病毒对珊瑚礁生态系统中的生物进化、生物地球化学循环、珊瑚疾病等方面具有重要的生态影响。随着珊瑚礁的全球性退化,病毒在珊瑚礁生态系统中的功能与危害日益显现。综述了珊瑚礁生态系统中病毒的研究现状与进展,包括：（1）珊瑚礁病毒的多样性与分布特征（水体、宿主、核心病毒组）;（2）珊瑚礁病毒的生态功能（感染方式、促进生物进化、生物地球化学循环）;（3）珊瑚礁病毒对全球气候变化的响应（热压力、珊瑚疾病）。总体而言,珊瑚礁生态系统具有极高的病毒多样性,所发现的60个科占已知所有病毒科数量的58%。珊瑚的核心病毒组主要由双链DNA病毒、单链DNA病毒、单链逆转录病毒所组成,珊瑚黏液层对病毒具有富集作用。"Piggyback-the-Winner"（依附-胜利）是病毒在珊瑚礁中主要的生物动力学模式,其可通过水平基因迁移的方式促进礁区生物进化。病毒可通过裂解细菌与浮游藻类的途径参与珊瑚礁的生物地球化学循环,尤其是碳循环与氮循环过程。此外,病毒还具有介导珊瑚热白化与直接引发珊瑚疾病的能力,这会影响珊瑚礁生态系统应对气候变化的适应性与恢复力。基于国际上的研究进展综述,结合南海珊瑚礁生态现状提出以下研究方向,以期促进我国珊瑚礁病毒学的发展：（1）开展南海珊瑚礁中病毒多样性的识别及其时-空分布特征研究;（2）探索病毒对南海珊瑚热白化、珊瑚疾病的介导作用及其与气候变化的关系;（3）揭示病毒对南海珊瑚礁生物地球化学循环的贡献。     

Paris Agreement could prevent regional mass extinctions of coral species

Coral reef ecosystems are expected to undergo significant declines over the coming decades as oceans become warmer and more acidic. We investigate the environmental tolerances of over 650 Scleractinian coral species based on the conditions found within their present-day ranges and in areas where they are currently absent but could potentially reach via larval dispersal. These “environmental envelopes” and connectivity constraints are then used to develop global forecasts for potential coral species richness under two emission scenarios, representing the Paris Agreement target (“SSP1-2.6”) and high levels of emissions (“SSP5-8.5”). Although we do not directly predict coral mortality or adaptation, the projected changes to environmental suitability suggest considerable declines in coral species richness for the majority of the world's tropical coral reefs, with a net loss in average local richness of 73% (Paris Agreement) to 91% (High Emissions) by 2080–2090 and particularly large declines across sites in the Great Barrier Reef, Coral Sea, Western Indian Ocean, and Caribbean. However, at the regional scale, we find that environmental suitability for the majority of coral species can be largely maintained under the Paris Agreement target, with 0%–30% potential net species lost in most regions (increasing to 50% for the Great Barrier Reef) as opposed to 80%–90% losses under High Emissions. Projections for subtropical areas suggest that range expansion will give rise to coral reefs with low species richness (typically 10–20 coral species per region) and will not meaningfully offset declines in the tropics. This work represents the first global projection of coral species richness under oceanic warming and acidification. Our results highlight the critical importance of mitigating climate change to avoid potentially massive extinctions of coral species.     

An introduction to the biogeochemical cycling of calcium and substitutive strontium in living coral reef mesocosms

The coral reef mesocosms designed by the Smithsonian Institution's Dr. Walter Adey, his Marine System Laboratory personnel, and staff members of the Pittsburgh Aqua-Zoo simulate most of the physical, chemical, and biological parameters found in natural Caribbean coral reefs. After developing the mesocosm in Pittsburgh, an evaluation and comparison between natural reef seawater sources and closed mesocosm seawater conditions indicated that an additional parameter should be investigated. It was hypothesized that, given time, the aragonite- and calcite (CaCO₃ crystal forms)-producing organisms in the closed mesocosms could deplete the seawater of available Ca²⁺ and substitutive Sr²⁺. Atomic absorption spectrophotometry was utilized to determine concentrations in the seawater over time. Results showed a substantial reduction in dissolved Ca and Sr in the mesocosm after approximately two years. Dissolved aragonitic Halimeda algae parts were put into the system for replacive purposes. In terms of the biogeochemical cycling of Ca²⁺ and Sr²⁺, the coral reef mesocosm organisms behaved similarly to natural reefs, which have a constant supply of dissolved Ca²⁺ and Sr²⁺. Further research utilizing radiolabeled sources of Ca²⁺, Sr²⁺, and Mg²⁺, in conjunction with in vivo scanning electron microscopy (SEM) and growth increment studies, are recommended for determining the exact biogeochemical pathways for these elements in coral reefs, and to quantify growth parameters. © 1993 Wiley-Liss, Inc.     

Delayed coral recovery in a warming ocean

Climate change threatens coral reefs across the world. Intense bleaching has caused dramatic coral mortality in many tropical regions in recent decades, but less obvious chronic effects of temperature and other stressors can be equally threatening to the long‐term persistence of diverse coral‐dominated reef systems. Coral reefs persist if coral recovery rates equal or exceed average rates of mortality. While mortality from acute destructive events is often obvious and easy to measure, estimating recovery rates and investigating the factors that influence them requires long‐term commitment. Coastal development is increasing in many regions, and sea surface temperatures are also rising. The resulting chronic stresses have predictable, adverse effects on coral recovery, but the lack of consistent long‐term data sets has prevented measurement of how much coral recovery rates are actually changing. Using long‐term monitoring data from 47 reefs spread over 10 degrees of latitude on Australia's Great Barrier Reef (GBR), we used a modified Gompertz equation to estimate coral recovery rates following disturbance. We compared coral recovery rates in two periods: 7 years before and 7 years after an acute and widespread heat stress event on the GBR in 2002. From 2003 to 2009, there were few acute disturbances in the region, allowing us to attribute the observed shortfall in coral recovery rates to residual effects of acute heat stress plus other chronic stressors. Compared with the period before 2002, the recovery of fast‐growing Acroporidae and of “Other” slower growing hard corals slowed after 2002, doubling the time taken for modest levels of recovery. If this persists, recovery times will be increasing at a time when acute disturbances are predicted to become more frequent and intense. Our study supports the need for management actions to protect reefs from locally generated stresses, as well as urgent global action to mitigate climate change.     

Differential uses of coral reef habitats by a poorly-known cryptic fish predator

This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes ²³Na, ²⁵Mg, ⁴³Ca, ⁵⁵Mn, ⁵⁹Co, ⁶⁰Ni, ⁶³Cu, ⁶⁶Zn, ⁸⁶Sr, ¹¹¹Cd, ¹³⁸Ba and ²⁰⁸Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.