Patterns of spread of coral disease in the Florida Keys

Reefs in the Florida Keys are experiencing a dramatic increase in the number of localities and number of species with coral disease. In extensive surveys from Key Largo to Key West in 160 stations at 40 randomly chosen sites, there has been a dramatic increase in (1) the number of locations exhibiting disease (82% of all stations are now affected, a 404% increase over 1996 values), (2) the number of species affected (85% of all species are now affected, a 218% increase over 1996 values), and (3) the rate of coral mortality (the deep fore-reef at Carysfort experienced a 60% reduction of living coral cover during the survey). Two null hypotheses (1) that the incidence of disease has remained constant through time and (2) that the apparent increase in disease is due to a lack of comparable earlier data, are both falsified. Different diseases exhibit different patterns of spread: some diseases (e.g. black band) exhibit low incidence and jump rapidly between sites; other diseases (e.g. white pox) exhibit patchy distributions and increase in frequency at affected sites from one year to the next. The central question of why so many corals are becoming simultaneously susceptible to a host of marine pathogens remains unanswered.     

Recruitment hotspots and bottlenecks mediate the distribution of corals on a Caribbean reef

Recruitment hotspots are locations where organisms are added to populations at high rates. On tropical reefs where coral abundance has declined, recruitment hotspots are important because they have the potential to promote population recovery. Around St. John, US Virgin Islands, coral recruitment at five sites revealed a hotspot that has persistent for 14 years. Recruitment created a hotspot in density of juvenile corals that was 600 m southeast of the recruitment hotspot. Neither hotspot led to increased coral cover, thus revealing the stringency of the demographic bottleneck impeding progression of recruits to adult sizes and preventing population growth. Recruitment hotspots in low-density coral populations are valuable targets for conservation and sources of corals for restoration.     

Location‐Specific Metrics for Rapidly Estimating the Abundance and Condition of the Threatened Coral Acropora cervicornis

We developed a method for quantifying the abundance of the threatened staghorn coral (Acropora cervicornis) and evaluated the accuracy of commonly used methods to assess colony condition. For small‐ to medium‐sized colonies, we show that colony ellipsoid volume estimated from simple colony dimensions serves as a reliable and efficient proxy for the more time‐consuming, conventional measure of colony total linear extension, and that this predictive relationship varies significantly among extant populations in the Caribbean. We also determined that visual estimates of colony partial mortality closely approximate to true values for colonies with <25% mortality, with in situ estimates outperforming estimates from digital images. These results provide coral reef managers and restoration practitioners with guidance for assessing partial mortality and location‐specific regression models to estimate “amount” of staghorn coral in both extant and restored staghorn populations in Belize, the United States Virgin Islands, and the Dry Tortugas National Park, Florida, U.S.A. As staghorn coral monitoring and restoration efforts continue to expand in the Caribbean, these methods for quickly determining staghorn abundance and condition will directly aid resource managers tasked with monitoring wild populations and tracking restoration success over time.     

珊瑚礁生态修复研究进展

珊瑚礁生态系统有着很高的生物多样性和重要的生态功能。20世纪80年代以后全球范围内珊瑚礁的大面积退化引起了人们广泛的关注。简述了世界珊瑚礁资源现状,破坏原因,生态修复方法以及我国的珊瑚礁资源现状和修复策略等。国际上通用的生态修复策略主要是根据珊瑚的两种繁殖方式进行的,此外再配合人为的适度干扰,增加珊瑚的成活率。方法主要有：珊瑚移植、Gardening、人工渔礁、底质稳固、幼体附着等以及对相关利益者的宣传,海岸带的保护等。我国珊瑚礁退化严重,但是由于缺乏相关的科技资料报道和技术支持,缺乏系统的研究,使得珊瑚礁的生态修复成绩甚微,今后应在该领域开展更多的工作。     

Enhancement of Grazing Gastropod Populations as a Coral Reef Restoration Tool: Predation Effects and Related Applied Implications

We aimed to evaluate the efficacy of the gastropod grazer Trochus niloticus in controlling epilithic algae and enhancing coral recruitment on artificial substrata on coral reefs where the biomass of herbivorous fishes was low due to heavy fishing pressure. Hatchery‐reared, subadult trochus were stocked onto pallet balls (small artificial reefs composed of concrete and limestone aggregate) at a density of approximately four individuals per square meter (external surface area). This density was re‐established with releases of new trochus each month for 6 months. At the end of the experiment, there were no significant differences in algal biomass, cover and community composition, or the density of coral recruits on substrata with and without trochus. High monthly attrition of stocked trochus on the pallet balls, apparently due mainly to predation by octopus, did not allow the evaluation of the efficiency of the trochus enhancement, at the desired density, as a restoration tool. However, at the lower trochus densities (circa 1 m^?2), which occurred as a result of predation in this study, no apparent enhancement of algal grazing or coral recruitment were observed. The surprisingly high predation of stocked trochus in a heavily fished and gleaned reef site stresses the importance of understanding all the factors affecting the survival of stocked animals. To help mitigate predation of trochus, artificial habitat with refuge spaces that allow the grazers to escape predation could be provided and individuals of a larger size could be released.     

In Situ Coral Nurseries Serve as Genetic Repositories for Coral Reef Restoration after an Extreme Cold‐Water Event

During an unusual cold‐water event in January 2010, reefs along the Florida Reef Tract suffered extensive coral mortality, especially in shallow reef habitats in close proximity to shore and with connections to coastal bays. The threatened staghorn coral, Acropora cervicornis, is the focus of propagation and restoration activities in Florida and one of the species that exhibited high susceptibility to low temperatures. Complete mortality of wild staghorn colonies was documented at 42.9% of donor sites surveyed after the cold event. Remarkably, 72.7% of sites with complete A. cervicornis mortality had fragments surviving within in situ coral nurseries. Thus, coral nurseries served as repositories for genetic material that would have otherwise been completely lost from donor sites. The location of the coral nurseries at deeper habitats and distanced from shallow nearshore habitats that experienced extreme temperature conditions buffered the impacts of the cold‐water event and preserved essential local genotypes for future Acropora restoration activities.     

Rapid Coral Decay Is Associated with Marine Heatwave Mortality Events on Reefs

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Strategies for Gardening Denuded Coral Reef Areas: The Applicability of Using Different Types of Coral Material for Reef Restoration

Recreational and other human activities degrade coral reefs worldwide to a point where efficient restoration techniques are needed. Here we tested several strategies for gardening denuded reefs. The gardening concept consists of in situ or ex situ mariculture of coral recruits, followed by their transplantation into degraded reef sites. In situ nurseries were established in Eilat's (Northern Red Sea) shallow waters, sheltering three types of coral materials taken from the branching species Stylophora pistillata (small colonies, branch fragments, and spat) that were monitored for up to two years. Pruning more than 10% of donor colonies' branches increased mortality, and surviving colonies displayed reduced reproductive activity. Maricultured isolated branches, however, exceeded donor colony life span and reproductive activity and added 0.5–45% skeletal mass per year. Forty‐four percent of the small colonies survived after 1.5‐year mariculture, revealing average yearly growth of 75 ± 32%. Three months ex situ maintenance of coral spat (sexual recruits) prior to the in situ nursery phase increased survivorship. Within the next 1.5 years, they developed into colonies of 3–4 cm diameter. Nursery periods of 2 years, 4–5 years, and more than> 5 years have been estimated for small colonies, spat, and isolated branches, respectively. These and other results, including the possible use of nubbins (minute fragments the size of a single or few polyps), are discussed, revealing benefits and drawbacks for each material. In situ coral mariculture is an improved practice to the common but potentially harmful protocol of direct coral transplantation. It is suggested that reef gardening may be used as a key management tool in conservation and restoration of denuded reef areas. The gardening concept may be applicable for coral reefs worldwide through site‐specific considerations and the use of different local coral species.     

Catastrophic mortality on inshore coral reefs of the Florida Keys due to severe low‐temperature stress

Coral reefs of the Florida Keys typically experience seasonal temperatures of 20–31 °C. Deviation outside this range causes physiological impairment of reef‐building corals, potentially leading to coral colony death. In January and February 2010, two closely spaced cold fronts, possibly driven by an unusually extreme Arctic Oscillation, caused sudden and severe seawater temperature declines in the Florida Keys. Inshore coral reefs [e.g., Admiral Reef (ADM)] experienced lower sustained temperatures (i.e., < 12 °C) than those further offshore [e.g., Little Grecian Reef (LG), minimum temperature = 17.2 °C]. During February and March 2010, we surveyed ADM and observed a mass die‐off of reef‐building corals, whereas 12 km away LG did not exhibit coral mortality. We subsequently measured the physiological effects of low‐temperature stress on three common reef‐building corals (i.e., Montastraea faveolata, Porites astreoides, and Siderastrea siderea) over a range of temperatures that replicated the inshore cold‐water anomaly (i.e., from 20 to 16 to 12 °C and back to 20 °C). Throughout the temperature modulations, coral respiration as well as endosymbiont gross photosynthesis and maximum quantum efficiency of photosystem II were measured. In addition, Symbiodinium genotypic identity, cell densities, and chlorophyll a content were determined at the beginning and conclusion of the experiment. All corals were significantly affected at 12 °C, but species‐specific physiological responses were found indicating different coral and/or Symbiodinium cold tolerances. Montastraea faveolata and P. astreoides appeared to be most negatively impacted because, upon return to 20 °C, significant reductions in gross photosynthesis and dark respiration persisted. Siderastrea siderea, however, readily recovered to pre‐treatment rates of dark respiration and gross photosynthesis. Visual surveys of inshore reefs corroborated these results, with S. siderea being minimally affected by the cold‐water anomaly, whereas M. faveolata and P. astreoides exhibited nearly 100% mortality. This study highlights the importance of understanding the physiological attributes of genotypically distinct coral‐Symbiodinium symbioses that contribute to tolerance, recovery, and consequences to an environmental perturbation. These data also document effects of a rarely studied environmental stressor, possibly initiated by remote global climate events, on coral‐Symbiodinium symbioses and coral reef communities.     

Quantitative assessment of coral diseases in the Florida Keys: strategy and methodology

Natural incidences of disease among scleractinian corals are unknown, since most studies have been initiated in response to specific disease outbreaks. Our ability to distinguish elevated disease incidences influenced by anthropogenic and climatic factors is limited since current estimates are probably inflated for extrapolation to larger areas. In our study, we used quantitative assessment methods to characterize the distribution and frequency of scleractinian and gorgonian coral diseases in the south Florida region. This paper is the first in a series that will detail different aspects of our studies. In this paper, we examined the strategy and methodology developed over 2 years to optimize the experimental design of our study. Pilot surveys were conducted in 1997 to develop and test methods, select and determine suitability of sites, and obtain preliminary data to assess the variance and efficiency of the sampling design. Survey periods targeted late spring, the time when coral diseases are believed to emerge, and late summer, the time when coral diseases are believed to be most prevalent. Two strata were chosen to evaluate patterns of coral disease: the first, geographic area, consisted of reefs in the vicinity of Key West, New Grounds and the Dry Tortugas; and the second, reef type, consisted of back, fore and transitional reefs. Random radial arc transects (10 m diameter) were used to quantify 10 diseases affecting 18 species of stony corals and gorgonian sea fans over a large geographical region. During the pilot survey, we demonstrated that the outer 8–10 m segment (113 m²) was an adequate sampling area. The survey implemented important quality assurance measures for data quality control. Power analysis determined that future studies should adopt =0.10, =0.0383, and 1-=0.9617 in our experimental design. The highest prevalence of disease in our study was during the 1997 summer survey, with a mean percent coral disease (MPCD) of 28% occurring at Key West area reefs, or 55% of all back reef stations. Our results do not show a clear pattern of seasonality in coral diseases within either stratum, although differences in disease distribution between reef types and geographic areas were apparent in some of the spring and summer surveys.     

珊瑚礁生态系的一般特点

随着工业化和城市化的不断发展 ,陆地上的资源在飞速地被消耗掉 ,生态环境也受到了严重的破坏 ,人们迫切地需要寻找新的资源和更好的环境 ,海洋因此成为首选。珊瑚礁生态系是海洋中生产力水平极高的生态系之一 ,被称为是“热带海洋沙漠中的绿洲” ,“海洋中的热带雨林”。由于其在全球海洋的过程与资源方面具有重要地位 ,而目前正受到生态退化的威胁 ,因而得到更多的关注。国际上将 1997年定为“珊瑚礁年”以普及人们的珊瑚礁保护与恢复意识和责任。本文介绍了珊瑚礁生态系的一些特点 ,分析了影响珊瑚礁生态系的自然和人为因素 ,并提出了保…     

大型海藻在珊瑚礁退化过程中的作用

随着全球范围珊瑚礁的退化,大型海藻在珊瑚礁区的覆盖度呈增多的趋势。大型海藻的大量生长,妨碍了珊瑚的生长、繁殖、恢复等过程。概括起来,大型海藻对珊瑚生长、繁殖及恢复过程所产生的不利影响主要包括:(1)大型海藻通过与珊瑚竞争空间和光照而影响珊瑚生长;(2)大型海藻与珊瑚直接接触时,通过摩擦作用及释放化感物质而影响珊瑚生长;(3)大型海藻的大量生长打破了珊瑚与海藻的竞争平衡,珊瑚为应对大型海藻的入侵而把用于生长和繁殖的能量转移到组织修复与防御上,进而造成珊瑚繁殖能量的减少;(4)大型海藻通过影响珊瑚幼虫的附着及附着后的存活率,而阻碍珊瑚群落的发展;(5)海藻还能通过富集沉积物、释放病原体及扰乱珊瑚共生微生物的生长等而间接影响珊瑚生长。明确的竞争机制有利于研究海藻与珊瑚的相互作用过程。在总结前人对海藻与珊瑚的竞争机制研究的基础上,把两者的竞争机制划分成物理机制、化学机制、微生物机制三大类,物理机制是研究得比较透彻的竞争机制,而化学机制与微生物机制则需要更深入的研究,是当前研究的热点。目前,我国对珊瑚礁中底栖海藻与珊瑚的相互作用研究甚少;鉴于此,对底栖海藻功能群的划分类型以及三大类型底栖海藻对珊瑚的作用特点做了简要介绍,并对珊瑚礁退化的现状和退化珊瑚礁区内海藻的表现做了概述。在此基础上,再综述国外关于大型海藻对珊瑚的影响研究进展,指出我国应该加强对南海珊瑚礁区大型海藻的种类分布及丰富度等的调查,评价大型海藻对南海珊瑚礁的影响现状;并结合生理学、分子生物学技术和生态学研究手段,在细胞与分子水平上探索海藻对珊瑚的影响机制,以期为珊瑚礁生态系统的保护提供参考。     

Pelagic Subsidies Underpin Fish Productivity on a Degraded Coral Reef

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Effects of substrata, resident conspecifics and damselfish on the settlement and recruitment of the stoplight parrotfish, Sparisoma viride

Recruitment plays an important role in the population dynamics of marine organisms and is often quantified as a surrogate for settlement. When quantified, recruitment includes settlement plus a period of time in the benthic habitat. Therefore, it is essential to determine whether post-settlement processes alter patterns established at settlement. I conducted a series of experiments on 2.0 m² patch reefs to examine the importance of pre- and post-settlement processes to the distribution and abundance of recruits of the stoplight parrotfish, Sparisoma viride, on the Tague Bay reef, St. Croix, USVI. Recruitment was higher to the coral Porites porites than to another common coral Montastrea annularis, but there was no evidence of microhabitat choice at settlement. This result, in conjunction with the examination of the size classes of recruits present on P. porites and M. annularis patch reefs in a separate experiment suggested that differences in recruitment were established after settlement. Stoplights settled in higher numbers to patch reefs that contained conspecific residents, and persistence was higher at higher recruit density. Although resident damselfish directed significant amounts of agonistic behavior towards newly stoplight recruits, damselfish presence had no effect on settlement. However, damselfish presence did reduce stoplight recruitment. These results demonstrate that both pre- and post-settlement processes influence the recruitment of stoplight parrotfish. More importantly, these results indicate that benthic processes can alter recruitment patterns from initial settlement patterns, and indicate that workers should be careful in using recruitment as a proxy for settlement.     

CO2 enrichment and reduced seawater pH had no effect on the embryonic development of Acropora palmata (Anthozoa,Scleractinia).

The effects of decreased pH, caused by carbon dioxide (CO₂) dissolution in seawater (known as ocean acidification (OA)), on the development of newly fertilized eggs of the Caribbean reef-building coral, Acropora palmata, was tested in three experiments conducted during the summers of 2008 and 2009 (two repeats). Three levels of CO₂ enrichment were used: present day conditions (400?µatm, pH 8.1) and two CO₂-enriched conditions (700?µatm, pH 7.9, and 1000?µatm, pH 7.7). No effects on the progression or timing of development, or embryo and larval size, were detected in any of the three experimental runs. The results show that the embryos and larvae of A. palmata are able to develop normally under seawater pH of at least 0.4 pH units lower than the present levels. Acropora palmata larvae do not usually begin to calcify after settlement, so this study only examined the non-calcifying part of the life cycle of this species. Most of the concern about the effects of OA on marine organisms centers on its effect on calcification. Negative effects of OA on the embryonic development of this species were not found and they may not manifest until the newly settled polyps begin to calcify.     

Caribbean reefs of the Anthropocene: Variance in ecosystem metrics indicates bright spots on coral depauperate reefs

Dramatic coral loss has significantly altered many Caribbean reefs, with potentially important consequences for the ecological functions and ecosystem services provided by reef systems. Many studies examine coral loss and its causes—and often presume a universal decline of ecosystem services with coral loss—rather than evaluating the range of possible outcomes for a diversity of ecosystem functions and services at reefs varying in coral cover. We evaluate 10 key ecosystem metrics, relating to a variety of different reef ecosystem functions and services, on 328 Caribbean reefs varying in coral cover. We focus on the range and variability of these metrics rather than on mean responses. In contrast to a prevailing paradigm, we document high variability for a variety of metrics, and for many the range of outcomes is not related to coral cover. We find numerous “bright spots,” where herbivorous fish biomass, density of large fishes, fishery value, and/or fish species richness are high, despite low coral cover. Although it remains critical to protect and restore corals, understanding variability in ecosystem metrics among low‐coral reefs can facilitate the maintenance of reefs with sustained functions and services as we work to restore degraded systems. This framework can be applied to other ecosystems in the Anthropocene to better understand variance in ecosystem service outcomes and identify where and why bright spots exist.     

北部湾近海珊瑚礁区系沉积物抗菌活性放线菌类群

通过对大肠埃希菌和枯草芽胞杆菌抗菌活性初步筛选,从北部湾近海珊瑚礁区5个沉积物样品中成功分离得到51株具有不同抗菌活性的放线菌,其中9株具有较强抗菌能力。根据这9株放线菌的菌落和孢子形态,可确定它们都属于链霉菌属。 RAPD-PCR分析表明这9株放线菌为6种不同类型,16S rDNA序列和系统发生树分析表明,9株放线菌可划分到4个大的类群6种不同类型,且结果显示RAPD-PCR聚类分析与16S rDNA序列聚类分析的结果具有较大的一致性。生理生化鉴定结果表明,分离株与亲缘关系最近的放线菌模式菌株的生理生化特征均存在差异,这说明分离株为放线菌新种的可能性比较大。这6种放线菌具有较为广谱的抑菌活性,并且抑菌活性均存在一定的差异,说明其可能分泌出多种结构功能不同的活性次生代谢产物。研究结果表明,广西北部湾近海珊瑚礁区系沉积物蕴藏着丰富的可供药物开发的放线菌资源。     

Geographic differences in species boundaries among members of the Montastraea annularis complex based on molecular and morphological markers

The three members of the Montastraea annularis complex (M. annularis, M. franksi, and M. faveolata) are dominant reef builders in the western Atlantic whose species status has been controversial for over a decade. Although differences in colony morphology and reproductive characteristics exist, interspecific fertilizations are possible in the laboratory and genetic differentiation is slight. Here we compare the three taxa genetically and morphologically in Panama and the Bahamas, widely separated locations spanning most of their geographic ranges. In Panama, analyses of three AFLP loci, a noncoding region of the mitochondrial genome, and ITS sequences reveal that M. faveolata is strongly differentiated genetically. Discriminant function analysis also indicates no overlap with the other two species in the fine structure of the corallites that comprise the colony. Genetic analyses of larvae from interspecific crosses between M. faveolata and the other two taxa confirmed the hybrid status of the larvae, but no examples of the most probable F1 genotype were observed in the field. Although M. annularis and M. franksi were more similar, they also exhibited strong frequency differences at two AFLP loci and in the mitochondrial noncoding region, as well as distinct corallite structure. In the Bahamas, in contrast, the three taxa exhibited overlapping morphologies. Montastraeafranksi and M. annularis were indistinguishable genetically, and M. faveolata was distinct at fewer genetic loci. Once again, however, the most probable F1 genotype involving M. faveolata was not observed. Geographic differences between Panama and the Bahamas explain why past studies have come to different conclusions concerning the status of the three species. In general, the genetic and morphological data suggest a north to south hybridization gradient, with evidence for introgression strongest in the north. However, reproductive data show no such trend, with intrinsic barriers to gene flow comparable or stronger in the north.     

Rehabilitation of coral reefs through removal of macroalgae: state of knowledge and considerations for management and implementation

Coral reef ecosystems are under increasing pressure by multiple stressors that degrade reef condition and function. Although improved management systems have yielded benefits in many regions, broad‐scale declines continue and additional practical and effective solutions for reef conservation and management are urgently needed. Ecological interventions to assist or enhance ecosystem recovery are standard practice in many terrestrial management regimes, and they are now increasingly being implemented in the marine environment. Intervention activities in coral reef systems include the control of coral predators (e.g. crown‐of‐thorns starfish), substrate modification, the creation of artificial habitats and the cultivation, transplantation, and assisted recruitment of corals. On many coastal reefs, corals face competition and overgrowth by fleshy macroalgae whose abundance may be elevated due to acute disturbance events, chronic nutrient enrichment, and reduced herbivory. Active macroalgae removal has been proposed and trialed as a management tool to reduce competition between algae and corals and provide space for coral recruitment, in the hope of restoring the spatial dominance of habitat‐forming corals. However, macroalgae removal has received little formal attention as a method of reef restoration. This review synthesizes available knowledge of the ecological role of macroalgae on coral reefs and the potential benefits and risks associated with their active removal.