Shifting ecological baselines and the demise of Acropora cervicornis in the western North Atlantic and Caribbean Province: a Pleistocene perspective

 In recent years, marine scientists have become increasingly alarmed over the decline of live coral cover throughout the Caribbean and tropical western Atlantic region. The Holocene and Pleistocene fossil record of coral reefs from this region potentially provides a wealth of long-term ecologic information with which to assess the historical record of changes in shallow water coral reef communities. Before fossil data can be applied to the modern reef system, critical problems involving fossil preservation must be addressed. Moreover, it must be demonstrated that the classic reef coral zonation patterns described in the early days of coral reef ecology, and upon which “healthy” versus “unhealthy” reefs are determined, are themselves representative of reefs that existed prior to any human influence. To address these issues, we have conducted systematic censuses of life and death assemblages on modern “healthy” patch reefs in the Florida reef tract that conform to the classic Caribbean model of reef coral zonation, and a patch reef in the Bahamas that is currently undergoing a transition in coral dominance that is part of a greater Caribbean-wide phenomenon. Results were compared to censuses of ancient reef assemblages preserved in Pleistocene limestones in close proximity to each modern reef. We have determined that the Pleistocene fossil record of coral reefs may be used to calibrate an ecological baseline with which to compare modern reef assemblages, and suggest that the current and rapid decline of Acropora cervicornis observed on a Bahamian patch reef may be a unique event that contrasts with the long-term persistence of this taxon during Pleistocene and Holocene time. Accepted: 19 May 1998     

Microbioerosion in Tahitian reefs: a record of environmental change during the last deglacial sea-level rise (IODP 310)

The main motivation for Integrated Ocean Drilling Program Expedition 310 to the Tahitian Archipelago was the assumption that the last deglacial sea‐level rise is precisely recorded in the coral reefs of this far‐field site. The Tahitian deglacial succession typically consists of coral framework subsequently encrusted by coralline algae and microbialites. The high abundance of microbialites is uncommon for shallow‐water coral reefs, and the environmental conditions favouring their development are still poorly understood. Microbioerosion patterns in the three principal framework components (corals, coralline algae, microbialites) are studied with respect to relative light availability during coral growth and subsequent encrustation, in order to constrain the palaeobathymetry and the relative timing of the encrustation. Unexpectedly for a tropical, light‐flooded setting, ichnotaxa typical for the deep‐euphotic to dysphotic zone dominate. The key ichnotaxa for the shallow euphotic zone are scarce in the analysed sample set, and are restricted to the base of the deglacial succession, thus reflecting the deglacial sea‐level rise. At the base of the deglacial reef succession, the ichnocoenoses present in the corals indicate shallower bathymetries than those in the encrusting microbialites. This is in agreement with radiocarbon data that indicate a time gap of more than 600 years between coral death and microbialite formation. At the top of the deglacial reef succession, in contrast, the microbioerosion patterns in the three framework components indicate a uniform palaeobathymetry, and radiocarbon ages imply that encrustation took place shortly after coral demise. An enigma arises from the fact that the ichnocoenoses imply photic conditions that appear very deep for zooxanthellate coral growth. During the deglacial sea‐level rise increased nutrients and fluvial influx may have led to (seasonal?) eutrophication, condensing the photic zonation. This would have exerted stress on the coral ecosystem and played a significant role in initiating microbialite development.     

Review of coral reef ecosystem remote sensing

Coral reef communities face unprecedented pressures at local, regional and global scales as a consequence of climate change and anthropogenic disturbance. Remote sensing, from satellites or aircraft, is possibly the only means to measure the effects of such stresses at appropriately large spatial scales. In the past 30 years, remote sensing of coral reefs has made rapid progress. However, the current technology is still not mature enough to monitor complicated coral reef ecosystems. Compared with foreign research in this field, our work lags far behind. There are still deficiencies in many aspects, such as basic data collection, theoretical research and platform construction. In our nation, it is even unclear how coral reefs disperse and where they may be unhealthy. In this paper, general characteristics of coral reef ecosystems and spectral features of different reef benthos have been summarized, based initially on a review of relevant literature in recent years. Based on the spectral separability of different reef types or benthos, remote sensing can be used to monitor two aspects of coral reefs: (1) Measurement of the ecological properties of reefs. (2) Health assessment of the coral reef ecosystem. In the first part, optical remote sensing methods are widely used to map reef geomorphology and habitats or biotopes. The investigation of geomorphologic zonation has proven to be one of the most successful applications, as different geomorphologic zones are associated with characteristic benthic community structures and occur at spatial scales of tens to hundreds of meters, they are amenable to remote detection by moderate to high resolution sensors. With more and more attention on the ecological problems of coral reefs, a number of studies have used high resolution sensors to map reef communities. The number of classes distinguishable depends on many factors, including the platforms, resolution (spectral, spatial and temporal resolution) and environmental conditions (water depth, water clarity, surface roughness, etc.). Compared with deep water color remote sensing, or terrestrial remote sensing, three techniques for the measurement of reef ecological properties are examined in this paper: (1) Coral reef classification system using remote sensing. (2) Techniques of sea surface correction and water column correction. (3) Techniques of coral reef information extraction from images. In terms of the complexity of coral reef ecosystems, the current techniques still need further improvement or optimization. In the health assessment of coral reef ecosystems, there are two ways to carry out the monitoring using remote sensing: (1) Monitoring the pigment or symbiotic zooxanthellae contents in corals. (2) Measuring the environmental properties of reefs. The first way is theoretically feasible, but difficult to achieve in practice. Currently, most reef health assessments are carried out by measuring environmental parameters, including sea surface temperature, solar radiation, ultraviolet radiation, water color, wind speed and direction, rainfall, ocean acidification, sea level, etc., of which sea surface temperature has been routinely measured by NOAA to monitor coral bleaching. In addition to the contents above, this article puts forward five main prospects for development in the future: (1) Establishment of a coral reef classification system using remote sensing. (2) Satellite launch for monitoring coral reefs. (3) Theoretical and methodological development. (4) Establishment of a spectral database for different reef benthos. (5) Integrated application of multi-source remote sensing data. It is hoped that the information provided here will be a reference for subsequent similar studies.     

Coral assemblages, biofacies, and ecological zones in the mid-Holocene reef deDosits of the Enriquillo Valley, Dominican Republic

Stemann, T. A. & Johnson, K. G. 1992 07 15: Coral assemblages, biofacies. and ecological zones in the mid-Holocene reef deposits of the Enriquillo Valley, Dominican Republic. A large, subaerially exposed mid-Holocene reef in the Enriquillo Valley (southwest Dominican Republic) provides an excellent opportunity to examine the relationship between reefal ecology and reefal deposits. Coral species richness and diversity in the Enriquillo reef are comparable to that found in the recent of the Caribbean, and ecological zonation comprised of a shallow-water branching coral zone and a deeper water mixed-coral zone is apparent. Similar zonation and diversity patterns have been recognized on living Caribbcan reefs with moderate wave exposure. Three statistically discrete biopdcies can be discriminated in the Enriquillo deposits using quadrat point-counting techniques commonly used to census modern reefs. They include a facies dominated by Acropora cervicornis, a low diversity assemblage with abundant, large colonies of Siderastrea siderea and Stephanocoenia intersepta, and a higher diversity assembbdge composed of various taxa including Montastraea spp., Colpophyllia spp., and Agaricia spp. Each facies can be recognized at scales of 1–3 m², though in some cases they extend for more than 20 m². In general, the A. cervicornis facies is spatially segregated from the other two biofacies. although neither the shallow nor the deep-water ecological zone is comprised of a single reef biofacies. Rather, the biofacies described here appear to represent distinct micro-environments resulting from ecological variation at a subzonal scale. Micro-environments of similar scale are most likely preserved in other reef deposits. Recognition of these subzonal biofacies may have important consequences for the stratigraphical and paleoccological interpretation of fossil reefs. Corals, biofacies, reef zonation, coral communities, fossil reefs.     

Succession of crustose coralline red algae (Rhodophyta) on coralgal reefs exposed to physical disturbance in the southwest Atlantic

Biological and physical disturbances create the conditions for species succession in any biological ecosystem. In particular, coral reefs are susceptible to this process because of the complexity of their ecological relationships. In the southwest Atlantic, nearshore reefs are mostly coated by a thin layer of coralline crusts rather than stony corals. However, little is known about the succession of crustose coralline algae. We studied this process by means of a series of experimental and control discs exposed to physical disturbance. Our results showed that the dominant species in natural conditions, Pneophyllum conicum, had early recruits and later became dominant on the discs, replicating the community structure of the actual reef. This species had mature reproductive structures and available spores from the beginning of the colonization experiments. Thicker crusts of Porolithon pachydermum and Peyssonnelia sp. were found on the discs after 112 days, and significantly increased their cover over the succeeding months; and after 1 year, P. conicum was less abundant. Physical disturbance increased crust recruitment and the low-light environment created by sediments. The data demonstrated coexistence among crustose coralline species and a tolerance to physical disturbance, which seemed to favor the thinner crusts of P. conicum over thick-crust species during succession. The succession pattern observed in this subtropical Brazilian coral reef differs from that described for shallow tropical reef communities.     

Coral-microbialite reefs in pure carbonate versus mixed carbonate-siliciclastic depositional environments: the example of the Pagny-sur-Meuse section (Upper Jurassic,northeastern France)

Middle to Upper Oxfordian reefs of a shallow marine carbonate platform located in northeastern France show important facies changes in conjunction with terrigeneous contents. The Pagny-sur-Meuse section shows coral-microbialite reefs that developed both in pure carbonate limestones and in mixed carbonate-siliciclastic deposits. Phototrophic coral associations dominated in pure carbonate environments, whereas a mixed phototrophic/heterotrophic coral fauna occurred in more siliciclastic settings. Microbialites occur in pure carbonate facies but are more abundant in mixed carbonate-siliciclastic settings. Reefs seem to have lived through periods favourable for intense coral growth that was contemporaneous with a first microbialitic layer and periods more favourable for large microbialitic development (second microbialitic layer). The first microbialitic crust probably developed within the reef body and thus appears to be controlled by autogenic factors. The second generation of microbialites tended to develop over the entire reef surface and was probably mainly controlled by allogenic factors. Variations in terrigeneous input and nutrient content, rather related to climatic conditions than to water depth and accumulation rate, were major factors controlling development of reefs and their taxonomic composition.     

Coral frameworks revisited–reefs and coral carpets in the northern Red Sea

 Coral communities were investigated in the northern Red Sea, in the Gulfs of Suez and Aqaba, for their framework building potential. Five types of coral frameworks were differentiated: Acropora reef framework, Porites reef framework, Porites carpet, faviid carpet, and Stylophora carpet. Two non-framework community types were found: the Stylophora-Acropora community, and soft coral communities. Reef frameworks show a clear ecological zonation along depth and hydrodynamic exposure gradients, with clear indicator communities for each zone. By definition, coral carpets build a framework but lack distinct zonation patterns since they grow only in areas without pronounced gradients. In the northern Red Sea they show a gradual change with depth from Porites to faviid dominance. A Stylophora carpet is restricted to shallow water in the northern Gulf of Suez. Although growth rates of carpets may be somewhat less than those of reefs, the carbonate accumulation is considered to be higher in carpet areas due to their significantly higher areal extension. In addition, reefs and carpets have different sediment retention characteristics – the carpet retains, the reef exports. The in situ fossilization potential of coral carpets is expected to be higher than that of reef frameworks. Accepted: 25 May 1999     

珊瑚礁生态脆弱性评价--以泰国思仓岛为例

珊瑚礁生态系统受到环境变化、人类活动等各种因素的严重威胁,保护珊瑚礁生态系统是目前全球海洋生态保护的热点,对珊瑚礁开展定量的生态脆弱性评估能够为保护管理对策的制定提供重要科学依据。本研究选取泰国思仓岛作为研究区域,结合空间分析技术建立了具有通用性的珊瑚礁生态脆弱性评估方法。基于ESA模型构建了珊瑚礁生态脆弱性综合指数和评价指标体系,系统分析了思仓岛珊瑚礁脆弱性的来源、构成,并直观展现了脆弱性的区域空间分布。结果表明:思仓岛研究区东北侧的珊瑚礁生态脆弱性大于西南侧,当地珊瑚礁的关键影响因子分别为驳船排污、港口码头、水体透明度等。根据脆弱性评价的结果,提出了当地珊瑚礁保护与修复的空间分区管理对策。本研究为印度-太平洋区系珊瑚礁生态脆弱性评价提供了可行的示例,也为中国的珊瑚礁可持续管理研究提供了借鉴和参照。     

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。     

Coral successions in Upper Tortonian reefs in SE Spain

Martin, Jose M., Braga, Juan C. & Rivas, Pascual 1989 07 15: Coral successions in Upper Tortonian reefs in SE Spain. Lethaia , Vol. 22, pp. 271–286. oslo. ISSN 0024–1164,
During the Upper Tortonian (Upper Miocene), the Almanzora river corridor, a small Neogene basin in SE Spain, harboured coral reefs growing in three different environments: in fan deltas, beyond the influence of coarse terrigenous sedimentation; in the abandoned lobes of a delta complex; and on coastal margins. All of these reefs are composed of several successive beds, each of which may be made up mainly of Porites embedded in silt or of an initial Porites level followed by a silt-free Tarbellastraea level on top. Porites may be associated with corallines. This structure is interpreted as being the result of an ecological succession repeated over and over again. A pioneer association consisting mainly of Porites . by colonizing the substrate and continuing to grow through relatively adverse silt-deposition conditions, prepares the ground for Tarbellastraea to take over. A return to the previous conditions halts the growth of the Tarbellastraea colonies and the Porites association once more establishes itself in the silt, or else the renewed rate of deposition is sufficiently heavy to suffocate the whole bioconstruction.* Ecological succession. coral reefs, Tortonian, southeast Spain .     

Computer simultion of the reef zonation at Discovery Bay,Jamaica: Hurricane disruption and long-term physical oceanographic controls

A computer model (COREEF) designed to simulate the growth of Caribbean coral reefs has been tested for its ability to reconstruct the storm-induced and the established zonation patterns on the West Reef at Discovery Bay, Jamaica. Hindcast waves for nine positions of Hurricane Allen were routed across the reef, and the disruptions to the coralgal and sediment zones were calculated for each position. The predicted maximum and intermediate stage damages closely matched the actual destruction produced by this and other smaller storms. Despite their severity, hurricanes probably have minimal long-term effect on the established zonation of this reef, because their return period is generally less than the recovery period of the reef. Additional simulation experiments indicate that a composite of the wave conditions at Discovery Bay maintain the established reef zonation and that winter storm conditions produce the maximum bottom velocities that the coralgal framework can withstand without disruption.     

Diversity, composition and structure of Late Eocene shelf-edge coral associations (Nago Limestone, Northern Italy)

Summary During the Late Eocene, shelf-edge patch reefs developed on the western margin of the Lessini Shelf. The coral fauna, studied in the Nago Limestone type locality, is described and interpreted for the first time, and provides further data for better understanding of the generally poorly known Eocene reef communities. Facies analysis was carried out across the shallowing upward succession that characterizes the well exposed type-section of the Nago Limestone. Four distinct facies are identified and a detailed qualitative-quantitative investigation has been applied to the coral-bearing facies in particular, in order to describe and quantify the distribution and palaeoecological zonation of corals. By a comparison of sedimentological and palaeoecological data, it is possible to reconstruct a depositional model of the Nago Limestone at its type locality. In particular, the palaeoecological study clearly reveals that corals change with depth in taxonomic composition, in percentage and proportion within the framework and in growth form, allowing the definition of a relative depth coral zonation. Three coral associations are recognized from the base to the top of the shallowing upward sequence. These differ from each other in the relative abundance of main reefbuilders, in the growth form exhibited by corals in growth position and in the density of the reef framework. These variations are interpreted as responses to major environmental controls which prevailed during the deposition of the different facies (mainly light intensity and hydrodynamic energy). The coral speciesActinacis rollei Reuss is the most abundant and ubiquitous coral of the Nago Limestone. Its adaptation to low-light levels is described here for the first time, confirming the high plasticity of this important Paleogene reef-builder. The results of the present study are finally compared with data from other Middle-Late Eocene European reef sites and some common features are inferred.     

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.     

Coral zonation of an Oxfordian reef tract in the northern French Jura

During the Middle Oxfordian, numerous coral reefs flourished on the northern margin of the Tethys Ocean. The outcrop of Bonnevaux-le-Prieuré (northern French Jura mountains) provides a rare opportunity to observe a nearly complete section allowing the installation, evolution and demise of this global carbonate reef rich event to be studied. Quantitative data on coral assemblages together with sedimentological and palaeoecological observations lead to the reconstruction of a reef tract coral zonation. Starting from the outer slope, Dimorpharaea, Microsolena, Dendraraea, Comoseris, and Stylina ecozones are recognized. This new facies model implies a central position for an oolitic shoal in the highest energy zone, within the Comoseris ecozone. Applying this facies model to the sequence stratigraphic interpretation of the vertical succession results in recognising a third-order relative sea-level fluctuation, which can be correlated at least with Lorraine (France) and Switzerland.     

Operationalizing resilience for adaptive coral reef management under global environmental change

Cumulative pressures from global climate and ocean change combined with multiple regional and local‐scale stressors pose fundamental challenges to coral reef managers worldwide. Understanding how cumulative stressors affect coral reef vulnerability is critical for successful reef conservation now and in the future. In this review, we present the case that strategically managing for increased ecological resilience (capacity for stress resistance and recovery) can reduce coral reef vulnerability (risk of net decline) up to a point. Specifically, we propose an operational framework for identifying effective management levers to enhance resilience and support management decisions that reduce reef vulnerability. Building on a system understanding of biological and ecological processes that drive resilience of coral reefs in different environmental and socio‐economic settings, we present an Adaptive Resilience‐Based management (ARBM) framework and suggest a set of guidelines for how and where resilience can be enhanced via management interventions. We argue that press‐type stressors (pollution, sedimentation, overfishing, ocean warming and acidification) are key threats to coral reef resilience by affecting processes underpinning resistance and recovery, while pulse‐type (acute) stressors (e.g. storms, bleaching events, crown‐of‐thorns starfish outbreaks) increase the demand for resilience. We apply the framework to a set of example problems for Caribbean and Indo‐Pacific reefs. A combined strategy of active risk reduction and resilience support is needed, informed by key management objectives, knowledge of reef ecosystem processes and consideration of environmental and social drivers. As climate change and ocean acidification erode the resilience and increase the vulnerability of coral reefs globally, successful adaptive management of coral reefs will become increasingly difficult. Given limited resources, on‐the‐ground solutions are likely to focus increasingly on actions that support resilience at finer spatial scales, and that are tightly linked to ecosystem goods and services.     

The zonation patterns of Caribbean coral reefs as controlled by wave and light energy input,bathymetric setting and reef morphology: computer simulation experiments

The computer model COREEF was used to simulate variations in the zonation patterns of Caribbean reefs in relation to parameters that affect the magnitude and distribution of wave and light energy. We first developed a simulated standard reef by exposing a simplified profile of the reef at Discovery Bay, Jamaica, to the known wave and light energy conditions to establish a reference coralgal and sedimentological zonation pattern. We then varied 13 parameters related to the wave and light energy input, bathymetric setting, and gross morphology of this reef to determine the effects of each parameter on the zonation pattern. Analysis of the simulation results indicates that submerging the reef or altering the wave or light energy input to the reef produces the greatest modifications of the zonation pattern. Morphological structures that alter a reef's horizontal dimensions only minimally affect the zonation pattern, but those structures that alter a reef's vertical dimensions-particularly steep-sided, wave reflecting structures-can significantly modify the zonation of the structure itself and that of more leeward areas. The more seaward the location of a morphological structure, the more profoundly it can affect the overall reef zonation. If waves break at the reef crest, wave energy conditions in the back reef are greatly reduced and the bottom consists of lower wave energy zones than those found at the same depths in the fore reef. If waves do not break at the crest, the back reef is subjected to almost the same wave conditions that exist in the fore reef, and the zones tend to be similar. The zonation patterns of some existing reefs resemble those of our simulated reefs, but other zonation patterns cannot be reproduced accurately because our simulation experiments do not consider the interactions between multiple parameters found on many existing reefs.     

Legacy effects of anthropogenic disturbances modulate dynamics in the world's coral reefs

Rapidly changing conditions alter disturbance patterns, highlighting the need to better understand how the transition from pulse disturbances to more persistent stress will impact ecosystem dynamics. We conducted a global analysis of the impacts of 11 types of disturbances on reef integrity using the rate of change of coral cover as a measure of damage. Then, we evaluated how the magnitude of the damage due to thermal stress, cyclones, and diseases varied among tropical Atlantic and Indo-Pacific reefs and whether the cumulative impact of thermal stress and cyclones was able to modulate the responses of reefs to future events. We found that reef damage largely depends on the condition of a reef before a disturbance, disturbance intensity, and biogeographic region, regardless of the type of disturbance. Changes in coral cover after thermal stress events were largely influenced by the cumulative stress of past disturbances and did not depend on disturbance intensity or initial coral cover, which suggests that an ecological memory is present within coral communities. In contrast, the effect of cyclones (and likely other physical impacts) was primarily modulated by the initial reef condition and did not appear to be influenced by previous impacts. Our findings also underscore that coral reefs can recover if stressful conditions decrease, yet the lack of action to reduce anthropogenic impacts and greenhouse gas emissions continues to trigger reef degradation. We uphold that evidence-based strategies can guide managers to make better decisions to prepare for future disturbances.     

Two decades of carbonate budget change on shifted coral reef assemblages: are these reefs being locked into low net budget states?

The ecology of coral reefs is rapidly shifting from historical baselines. One key-question is whether under these new, less favourable ecological conditions, coral reefs will be able to sustain key geo-ecological processes such as the capacity to accumulate carbonate structure. Here, we use data from 34 Caribbean reef sites to examine how the carbonate production, net erosion and net carbonate budgets, as well as the organisms underlying these processes, have changed over the past 15 years in the absence of further severe acute disturbances. We find that despite fundamental benthic ecological changes, these ecologically shifted coral assemblages have exhibited a modest but significant increase in their net carbonate budgets over the past 15 years. However, contrary to expectations this trend was driven by a decrease in erosion pressure, largely resulting from changes in the abundance and size-frequency distribution of parrotfishes, and not by an increase in rates of coral carbonate production. Although in the short term, the carbonate budgets seem to have benefitted marginally from reduced parrotfish erosion, the absence of these key substrate grazers, particularly of larger individuals, is unlikely to be conducive to reef recovery and will thus probably lock these reefs into low budget states.     

Turbulence-controlled succession in Middle Devonian reefs of eastern New York State

Wolosz. T. H. 1992 07 15: Turbulence-controlled succession in Middle Devonian reefs of eastern New York State.
The Edgecliff Member ol the Middle Devonian Onondaga Formation contains numerous reefs comprised of two distinct facies. The Phaceloid Colonial Rugosan Facies consists of thickets and mounds, while the Favositid/Crinoidal Sand facies occurs as flank beds surrounding rugosan mounds and as low shield-shaped banks interbedded with thickets of the colonial rugosan facics. Three of these reefs - the North Coxsackie. Albrights and Roberts Hill reefs - have been studied in order to determine the factors that controlled their development and their preserved paleocommunity succession. Both the Roberts Hill and Albrights reefs display well-developed rugosan mounds with an internal succession of rugosan genera. The North Coxsackie reef is a crinoidal sand bank with rugosan thickets and a back-reef satellite mound. Based on the lithology of the underlying limestone in which the reefs are rooted, the North Coxsackie reef is considered to have grown in a shallow-water environment, landwards of the two other reefs. Successional sequences or partial sequences are common to the three reefs, and are found to be reversible - a response attributed to changes in sea-level. As a result, the successions preserved in these reefs are interpreted as having been controlled by degree ol water turbulence.