Coral Carpets Research Articles

Marine animal forests in turbid environments are overlooked seascapes in urban areas

Marginal reefs can provide meaningful information about the structure and dynamics of ecosystems under suboptimal environmental conditions. In addition to their different characteristics, these environments can also occur in urbanized areas. In this note, we characterize marine animal forests (MAFs) on turbid-zone reefs on an urban coast in the equatorial southwestern Atlantic. Overall, the sandstone ferruginous reefs (6-10 m depth) exhibited a flat topography and gentle slope (1-2 m above the seabed). Benthic cover is composed mainly of sponge gardens and ascidians. In addition, we found a low-relief coral carpet with only one massive reef-building coral (Siderastrea stellata) and Zoantharia. The ascidians and sponges had a higher diversity (at least 15 species) than the cnidarians (two species) in these forests. The main animals forming this seascape are weedy and stress-tolerant species adapted to challenging environmental conditions, such as swell waves, mesotidal regimes, moderate turbidity waters, and periodic burial. In this regard, these conditions and human impacts have shaped a unique MAF. Remarkably, the studied formations seem similar to high-latitude marginal reefs or low-latitude reefs under the influence of upwelling, which sustains soft corals and non-framework building coral communities along with sponges and ascidians. In particular, the shallow MAFs along the semi-arid coast of Brazil seem to lack some of the characteristics of low-latitude reefs under high sedimentation, whose structure was described as coral rubble within sedimentary matrices. This suggests that factors other than periodic burials and low light availability affected these MAFs. These overlooked forests are widespread in this area and have been neglected in studies, despite their richness (> 31 taxa) and valuable ecosystem goods and services. In the context of urbanized areas subject to climate change and pollution impacts, jetties, and dredging activities, it is necessary to consider these lush forests in impact assessments and conservation policies.

Kilometre-scale coral carpets on mixed carbonate-siliciclastic platforms; a sedimentological study from the Lower Cretaceous of northwestern Africa

Coral carpets are biostromes that form laterally continuous but low-relief (typically less than 1-metre-high) coral communities with a lack of clear internal zonation. There are few locations that allow analysis of such systems on a regional (tens of kilometre) scale in the rock record. This study describes extensive, well-exposed, coral-rich bodies (coral carpets), deposited on the Moroccan northwest Atlantic shallow-marine margin during the Cretaceous (early Hauterivian). The coral-rich sequence reaches 50 m in thickness, with individual carpets between 10 and 100 cm thick, extending over an area of more than 150 km 2 . Logging and regional correlation, integrated with thin-section analysis, has allowed the evaluation of facies distribution, geometries and temporal evolution. The results provide information on allogenic and/or autogenic driving processes for coral development, and allows the generation of conceptual models for their growth. The Tamanar Fm. corals reflects a shallowing up sequence and the recovery of carbonate productivity following stressed environmental conditions in the late Valanginian. Temporally, coral morphological response relates to high-frequency relative sea level changes that affected water energy and turbidity; thick-branching and massive forms grew in shallow high energy environments whilst platy/flat forms grew in poorly lit and turbid environments. However, local-scale (over hundreds of metres) lateral changes in morphology and facies can be explained by autogenic factors independent of sea level change; varying sedimentation, hydrodynamism and turbidity across the extensive open marine platform. The termination of coral deposition is marked by a hardground surface, indicating slow rates of sedimentation and a transgression, which is followed by an influx of clastic sediments onto the platform, resulting in the deterioration of carbonate platform health, as conditions became intolerable for coral growth. These coral-rich outcrops contribute to the relatively sparse documentation of Hauterivian corals globally and suggest niche palaeoecological and palaeoclimatic relationships that allowed corals to develop despite stressed platform conditions. The low diversity, low-relief coral carpets may provide a proxy for the recovery and demise of corals in response to environmental stress on modern carbonate platforms and future climate change projections. • Kilometre-scale coral-rich outcrops onshore the Moroccan Atlantic Margin. • Non-framework coral carpets show no internal zonation. • Coral morphology and abundance controlled chiefly by water energy and turbidity. • Establishment and demise of corals linked to sea level and climatic change. • Low diversity corals possible proxy for recovery/loss in response to environmental stress.

Wave Energy Dissipation in a Shallow Coral Reef Lagoon Using Marine X‐Band Radar Data

AbstractA novel approach for estimating wave energy dissipation on a coral reef barrier is studied using X‐Band radar technology. The prominent features of coral reefs, including the delineation of reef morphological structure, wave energy dissipation and wave transformation processes are obtained in a reef lagoon in San Andres Island, Colombia. Results show that reef attenuates incident waves by approximately 75% due to both frictional processes and wave breaking, with an equivalent bottom roughness of 0.20 m and a wave friction factor of 0.18. These parameters are comparable with estimates reported in other shallow coral reef lagoons as well as at seagrass meadows obtained using in‐situ measurements. Also, the mean height of the reef elements Hbed and its standard deviation σb are also estimated in the entire radar coverage area. Hbed and σb (0.5 and 7.66 cm respectively) are in the same order of magnitude of measured data reported by previous studies and in good agreement with the geometric parameters proposed by in‐canopy flow models for branched species, such as Stylophora and Pocillopora, which are also common in the coral carpets of San Andres Island. This work proposes a completely novel use for X‐Band radars by describing prominent features in barrier‐reef systems including the delineation of the reef structure and wave energy dissipation.

Miocene paleoceanographic evolution of the Mediterranean area and carbonate production changes: A review

Miocene is a key interval in the global climate evolution as well as in the geodynamic evolution of the Mediterranean basin. Therefore, global and regional factors controlled Miocene Mediterranean oceanography, which, in turn, affected carbonate production. In this work, we review the Miocene paleocenographic evolution of the Mediterranean starting from its Sr and Nd isotope records. Secondly, we discuss Mediterranean shallow-water carbonate production changes to identify the role of oceanographic conditions in controlling carbonate systems' evolution. During Aquitanian, Sr and Nd isotope records attest an open Mediterranean, mainly fed by the Indian Ocean. From the late Burdigalian, the intermittent connection with the Indian Ocean changed the overall circulation in the basin, leading to higher residence time of waters and smaller water exchanges with the adjacent oceans. In this newly established paleoceanographic framework, regional factors such as volcanism, significantly affected Mediterranean seawater chemistry. Local tectonics led to the development of small sub-basins in the Eastern Mediterranean, characterized by restricted water exchanges from the Tortonian in the easternmost part, to the early Messinian, as attested by the deviation of the Sr isotope record of the proto-Adriatic basin. Larger Benthic Foraminifera (LBF) assemblages dominated carbonate production in the Aquitanian, while they were the most affected by the Indo-Pacific closure, showing a demise after the Burdigalian. With the LBF demise, red algae and bryozoans dominated carbonate ramps from the middle Miocene to the Tortonian. Bryozoans in particular spread during the Monterey Event, favoured by global and regional factors. During early to middle Miocene, corals formed mounds in the oligophotic zone or coral carpets controlled by local conditions. Conversely, in the late Tortonian-early Messinian, they developed as huge reef complexes in the Western and Central Mediterranean, with the exception of small restricted sub-basins, such as the proto-Adriatic basin, where red algae and small benthic foraminifera persisted.

Les faunes coralliennes de l’Oligocène de Malte : biodiversité et paléoenvironnement

The study of the coral biodiversity of the Upper Oligocene sedimentary series (Lower Coralline Limestone, Chattian) of Malta permitted the identification of 25 scleractinian genera represented by 41 species. Three new species are proposed: Miophoranaxxarensis n. sp., Nerthastraeamaltensis n. sp. and Gyrosmiliamaltensis n. sp. Observations made in various Oligocene sites in Malta, especially around Naxxar and Tal Bajjada, allow to establish a suite of coral associations which may vary spatially and vertically. The identified scleractinian associations can be represented by different types of coral assemblages and bioconstructions: isolated colonies, coral beds of varying density but of large spatial extent, more cohesive coral banks (coral carpets) or patch reefs forming morphologies with gentle lateral slopes. The colonial morphologies are closely linked to these different types of bioconstructions. These coral constructions have been established and developed in shallow marine areas. The coral biodiversity of the Oligocene of Malta fits well in the evolution of the Cenozoic reef phenomenon whose development reached its peak in the Oligocene with great coral richness in the Chattian in the Mediterranean area.

Coral carpets- a novel ecological engineering tool aimed at constructing coral communities on soft sand bottoms

Hard bottom substrates that are the hallmark property of the coral reefs can be expanded by transforming sedimentary areas into engineered reefs. Testing this rationale, we developed here two preset coral-carpet prototypes (‘coral sods’; 6 units, each 7.5 m2), one containing branching species and one with both coral forms (mixed-units) that were transplanted on a soft bottom area, containing 10 coral species (five branching, five massive; 354 ramets from 30 genotypes and 181 whole-colonies). Ramets from branching genotypes were distributed in central and peripheral coral-sod locations, whereas all massive colonies were put in central locations. The ‘coral sod’ carpets were set-up at the Eilat, Red Sea nursery, held in place for 2–8 months, then transplanted into a highly hostile soft-bottom area (15 m depth) and monitored for up to 17 months. Results revealed high survival rates for corals in the peripheral/center positions (80–100%; most combinations). A fast increase in ecological volume (EV) was recorded during 447 residency days, up to 112% in EV for Acropora variabilis mixed-units in the peripheral position. There was no statistically significant difference between treatments and sod's locations, except for the Pocillopora. damicornis branching/mixed treatment. At day 514, corals' aerial coverage has increased from 50% at onset to 67.3% for the branching units and to 61.5% in the mixed-units. Larvae released from transplanted Stylophora pistillata corals outperformed those of natal colonies in the two following reproductive seasons, significantly higher in the first reproductive season when compared to the second. Coral recruitment (day 485) was up to 4 times higher in the centers compared to the peripheries, in both coral-sod types. Using gypsum sticks dissipation, we recorded reduced water velocities at lateral and uppermost colonial architectures and in the coral sod centers as compared to peripheries. These results reveal the first steps for improved ‘coral sod’ units aiming to shape sandy tropical areas into flourishing coral reef sites.

Plants with Horticultural and Ecological Attributes for Green Roofs in a Cool, Dry Climate

Green roofs are building surface treatments where plants are grown in medium on a rooftop to cool or insulate buildings and/or to ameliorate negative environmental impacts of buildings. We initiated a 2-year study to characterize medium and weather conditions on a rooftop in a cool-dry climate and to identify plant species with horticultural and ecological attributes that survive and thrive on an unirrigated semi-intensive green roof in a cool-dry climate. Eighty-eight cold-hardy, drought-tolerant species with horticultural or ecological attributes were identified and planted into 12.7-cm-deep medium in trays that were placed on a rooftop. Medium temperatures and moistures were recorded, and plant survival and vigor were quantified. Hourly medium temperatures varied from –22.3 to 43 °C. Monthly medium water moistures varied from –2.5 to –73.3 kPa from May to September, and from –7.6 to –195 kPa from October to April. Monthly air temperature, relative humidity and irradiance varied from –9.4 to 21.7 °C, 44% to 80%, and from 206 to 1222 μmol·m−2·s−1. Mean survival scores decreased (4 = 100% survival) from 2.6 with grasses, to 2.3 with succulents, to 1.8 with temperate perennials, to 0 for geophytes (all died). Among grasses, Festuca ovina VNS, Koeleria macrantha 07-901 ND, Panicum virgatum, and Sporobolus heterolepis performed well. Among succulents, Sedum acre, S. album ‘Coral Carpet’, S. cauticola ‘Sunset Cloud’, S. ‘Czar’s Gold’, S. ellecombianum, S. hybridum ‘Immergruchen’, S. requieni, S. sexangulare, S. spurium ‘Dragon’s Blood’, ‘John Creech’, ‘Pearly Pink’, ‘Ruby Mantle’, and ‘Tricolor’ performed well. Among temperature nonsucculent perennials, Allium ceranum and senescens ‘Glaucum’, Geum triflorum, Talinum calycinum, and Thymus praecox ‘Red Creeping’ performed well. Data on Sedum suggested that medium-low temperature was more limiting to survival than moisture level. The differences in species that performed well here, compared with other studies, underscores the importance of regionally specific green roof plant species studies.

An assemblage of mollusks associated with the high latitude scleractinian coral Alveopora japonica (Eguchi 1968) in Jeju Island, off the south coast of Korea

Corals reefs and communities support a wide range of flora and fauna. The complete richness and abundance of faunal communities in either coral reefs or communities is not fully understood. This is especially true for high-latitude coral communities. In this work, we carried out an analysis of an Alveopora japonica associated mollusk assemblage, in Jeju Island, Korea. A. japonica is one of the major coral species present in high abundance (88–155 colonies m-2), with a high recruitment rate (7.8 juvenile corals m-2 yr-1) in Jeju Island, and may serve as a habitat for other benthic organisms. In 2012, a total number of 579 A. japonica colonies with sizes ranging between 15.1-346.7 cm2 in the surface area were collected from a 1m× 10m quadrat installed at a depth of 10 m at Keumneung, on the northwest coast of Jeju Island. Numerous benthic invertebrates were found to be associated with A. japonica colonies. Twenty-seven bivalves and gastropods were identified, including a boring mytilid, Lithophaga curta, and an arcid, Barbatia stearnsi. A zonalgeographical examination of the distribution ranges of these mollusks revealed a majority of warmer water species. Our observations also showed that A. japonica may be providing a habitat to grazing gastropod, Turbo cornutus, and encrusting Spondylidae and Chamidae bivalves. A. japonica forms a coral carpet with a distinct assemblage of bivalves. It is thought that the presence of these mollusks species in the coral indicates its use as a nursery for juvenile species, a ready food supply of organic detritus, and a refuge from predators.

BIOTIC AND ENVIRONMENTAL ORIGINS OF THE SOUTHEAST ASIAN MARINE BIODIVERSITY HOTSPOT: THE THROUGHFLOW PROJECT

The present-day global maximum for marine biodiversity has been located in Southeast Asia since at least the earliest Miocene. The history of biota in the region has been inferred from the present-day biogeography and phylogeny of extant organisms, but these analyses do not provide adequate tests of the various hypotheses proposed for the origins of the diversity hotspot. The papers in this special issue present the results of an interdisciplinary research project designed to reconstruct the history of shallow marine biota and habitats within the hotspot and help understand the ecological context responsible for the maintenance of the diverse regional biota. A series of remarkably complete and fresh exposures were studied from the Kutai Basin (East Kalimantan, Indonesia) that included thick lower to upper Miocene sections of deltaic and marine sediments including abundant and extremely well preserved fossils. New stratigraphic and environmental frameworks allowed comparison of biota from habitats ranging from shelf-edge reefs to nearshore shallow seagrass meadows and coral carpets. Diversity was overall high throughout the interval, especially when compared to diversity in similar modern turbid mixed carbonate-siliciclastic settings. This points to the previously unrecognized importance of these mesophotic habitats for the development of the diverse reef-associated communities in the modern-day hotspot.

DIVERSITY AND PALEOECOLOGY OF MIOCENE CORAL-ASSOCIATED MOLLUSKS FROM EAST KALIMANTAN (INDONESIA)

ABSTRACT This study is a preliminary assessment of an extremely diverse Tortonian (late Miocene) mollusk assemblage from a coral carpet environment preserved at Bontang (East Kalimantan, Indonesia). Even though coral-associated aragonitic faunas are rarely well preserved, the composition of the assemblage described here can be used to address the following questions: (1) How do the mollusk assemblages in coral habitats differ from other habitats, and (2) What is the effect of sampling on estimates of taxon richness? The mollusk assemblage is dominated by predatory snails and includes typical modern coral-associated taxa such as the gastropod Coralliophila and the bivalve Tridacna. Our investigation implies that adequate documentation of Cenozoic mollusk diversity in the Indo-Pacific is even more challenging than previously expected as very large samples are required to capture species richness. Further assessments of fossil faunas from coral-dominated habitats will be required to provide insight to develo...

Palaeoecology of well-preserved coral communities in a siliciclastic environment from the Late Pleistocene (MIS 7), Kish Island, Persian Gulf (Iran): the development of low-relief reef frameworks (biostromes) in increasingly restricted environments

Major changes in community structure and depositional relief of high-latitude coral communities in the southern Persian Gulf between marine isotope stage (MIS) 7 and the present day suggest that the area has become increasingly restricted. Corals and bivalves from outcrops on Kish Island, Iran, were identified in order to interpret the Late Pleistocene palaeoenvironmental setting. U/Th disequilibrium dating was used to constrain the ages of the stratigraphic units. During MIS 7, two coral-bearing sequences were deposited on what is now Kish Island. The lower sequence is dated as MIS 7.5 and changes laterally from an assemblage dominated by Cyphastrea sp. and Platygyra daedalea in the west to one characterized by branching Montipora in the east. By contrast, the upper sequence, dated as MIS 7.1, transitions from an assemblage dominated by platy Montipora in the west to a diverse assemblage of Platygyra and other faviids in the east. The assemblages of both sequences are within a marl matrix and bounded by thin lithified mollusc-rich layers. Corals and bivalves indicate that the sequences were deposited on gentle slopes in sheltered environments less than 20 m deep. The MIS 7 deposits may be classified as coral carpets or biostromes that developed a low-relief framework. During MIS 5, coral communities were no longer framework building and are now limited to an Acropora-rich layer of coral rubble that covers large parts of the island, and two small incipient reefs with sparse faviids. Similarities between the MIS 5 and modern nearshore coral communities suggest that the environmental conditions during MIS 5 were comparable to those of today. The late Pleistocene coral carpets and non-framework coral communities of the southern Persian Gulf may serve as models for coral biostromes in the fossil record, which formed under restricted environmental conditions such as elevated terrigenous input, high turbidity, and strong seasonal changes in temperature and/or salinity.

A Middle Miocene carbonate platform under silici-volcaniclastic sedimentation stress (Leitha Limestone, Styrian Basin, Austria) — Depositional environments, sedimentary evolution and palaeoecology

Siliciclastic influx is a major control for neritic carbonates. Herein, we present a shallow-marine mixed silici-volcaniclastic carbonate system from the Middle Miocene coralline algal-dominated Leitha Limestone in the Styrian Basin (Austria). The analyses of facies and stratal geometries reveal a succession of four depositional units and six facies types (reef facies, inter-reef facies, coralline algal debris facies, rhodolith-Porites facies, quartz sand-Planostegina facies, coral carpet facies). Depositional unit 1 comprises patch reefs (reef facies) and surrounding carbonate sands (inter-reef facies), which show a characteristic lateral succession of biotic associations (reef corals–rhodoliths–nodular celleporiform bryozoans–Planostegina). A similar modern analogue occurs in the Red Sea at the transition from patch reefs to seagrass meadows. In contrast, the coralline algal debris facies of depositional unit 2 represents a high-energetic submarine dune environment. A deepening–shallowing trend is suggested by the gradual shift from the muddy rhodolith-Porites facies to the detritic quartz sand-Planostegina facies in depositional unit 3, while the vertical transition of coral carpet facies to rhodolith-Porites facies in depositional unit 4 suggests again a deepening.Despite an isolated inner basin setting on the Middle Styrian High the coralline algal- and coral-dominated benthic carbonate communities in all depositional units and facies were strongly influenced by terrigenous sedimentation. Coarser siliciclastic sedimentation was linked to low-stands of relative sea level while fine clay fraction was deposited at any time due to the submarine alteration and reworking of volcanic ashes. Despite a high sedimentation stress the variety of coral communities (patch reefs, coral carpets, non-framework coral communities) and coral diversity is unique for the entire Central Paratethys. Leptoseris and two not identified coral species, one with thin-platy plocoid, the other with phaceloid branching growth form, are new coral records for the Central Paratethys. This is of particular importance for paleobiogeographic reconstructions since the Styrian Basin was located close to the northern margin of the global coral reef belt. It is assumed that the relatively high total coral diversity reflects dynamic habitat and population structures in an unstable coral ecosystem at the edge of coral reef distribution which was highly vulnerable to tectonically controlled changes affecting nature and distribution of clastic sediments. In general, increasing siltation stress reduced coral diversity, coral cover and colony sizes and led to the replacement of massive by platy growth forms and of suprastratal by constratal growth fabrics.

The evolution of mid Paleocene-early Eocene coral communities: How to survive during rapid global warming

Today, diverse communities of zooxanthellate corals thrive, but do not build reef, under a wide range of environmental conditions. In these settings they inhabit natural bottom communities, sometimes forming patch-reefs, coral carpets and knobs. Episodes in the fossil record, characterized by limited coral-reef development but widespread occurrence of coral-bearing carbonates, may represent the fossil analogs of these non-reef building, zooxanthellate coral communities. If so, the study of these corals could have valuable implications for paleoenvironmental reconstructions. Here we focus on the evolution of early Paleogene corals as a fossil example of coral communities mainly composed by zooxanthellate corals (or likely zooxanthellate), commonly occurring within carbonate biofacies and with relatively high diversity but with a limited bioconstructional potential as testified by the reduced record of coral reefs. We correlate changes of bioconstructional potential and community compositions of these fossil corals with the main ecological/environmental conditions at that time. The early Paleogene greenhouse climate was characterized by relatively short pulses of warming with the most prominent occurring at the Paleocene-Eocene boundary (PETM event), associated with high weathering rates, nutrient fluxes, and pCO2 levels. A synthesis of coral occurrences integrated with our data from the Adriatic Carbonate Platform (SW Slovenia) and the Minervois region (SW France), provides evidence for temporal changes in the reef-building capacity of corals associated with a shift in community composition toward forms adapted to tolerate deteriorating sea-water conditions. During the middle Paleocene coral–algal patch reefs and barrier reefs occurred from shallow-water settings, locally with reef-crest structures. A first shift can be traced from middle Paleocene to late Paleocene, with small coral–algal patch reefs and coral-bearing mounds development in shallow to intermediate water depths. In these mounds corals were highly subordinated as bioconstructors to other groups tolerant to higher levels of trophic resources (calcareous red algae, encrusting foraminifera, microbes, and sponges). A second shift occurred at the onset of the early Eocene with a further reduction of coral framework-building capacity. These coral communities mainly formed knobs in shallow-water, turbid settings associated with abundant foraminiferal deposits. We suggest that environmental conditions other than high temperature determined a combination of interrelated stressors that limited the coral-reef construction. A continuous enhancement of sediment load/nutrients combined with geochemical changes of ocean waters likely displaced corals as the main bioconstructors during the late Paleocene-early Eocene times. Nonetheless, these conditions did not affect the capacity of some corals to colonize the substrate, maintain biodiversity, and act as locally important carbonate-sediment producers, suggesting broad environmental tolerance limits of various species of corals. The implications of this study include clues as to how both ancient and modern zooxanthellate corals could respond to changing climate.

Solar radiation intensity influences extensive green roof plant communities

Two studies were conducted on a third-story rooftop to quantify the effect of solar radiation (full sun versus full shade) on several US native and non-native species for potential use on extensive green roofs. In the first study, plugs of six native and three non-native species were planted in May 2005 on substrates of two different depths (8.0 and 12.0 cm) both in sun and shade. Absolute cover (AC) was recorded using a point-frame transect during the growing season beginning in June 2005 and every 2 weeks thereafter for a period of 4 years. By week 174 (23 September 2008), most species exhibited different AC within a depth between sun and shade. However, when all species were combined, overall AC did not differ between sun and shade within a depth. This indicated that while species make-up was changing among solar radiation levels, that overall coverage was not significantly different between sun and shade. For all substrate depths and solar levels, the most abundant species were Sedum acre, Allium cernuum, Sedum album ‘Coral Carpet’, and Talinum calycinum. Less abundant species included Talinum parviflorum, Carex flacca, Sedum stenopetalum, and Sedum divergens, which all exhibited 0 or near 0 AC regardless of depth or solar radiation levels. With the exception of T. calycinum, native species were less abundant than non-native species. In the second study, six common extensive green roof species of Sedum established from seed in May 2005 on a 10.0 cm (3.9 in) substrate depth were compared in both sun and shade over four growing seasons. AC was evaluated as in the previous study. Solar radiation did not affect AC, but overall species composition differed between sun and shade levels. The most abundant species in full sun were S. acre (0.57 AC) and S. album ‘Coral Carpet’ (0.51 AC). Sedum kamtschaticum (0.57 AC) and Sedum spurium ‘Coccineum’ (0.35 AC) performed the best in the shade. For both solar levels, the least abundant species at week 174 were Sedum pulchellum (0.0 AC) and S. album ‘Coral Carpet’ (0.1 AC).

The distribution of molluscan assemblages and their postmortem fate on coral reefs in the Gulf of Aqaba (northern Red Sea)

Molluscan assemblages were studied on fringing reefs (reef flats, Millepora-fringing reefs, fringing reefs with massive corals) and fore-reef hard substrata (coral patches, coral carpets and small patch reefs) in the Gulf of Aqaba at water depths ranging from the intertidal to 26 m. A total of 1,665 molluscan individuals from 51 taxa was counted on 44 transects, which covered 220 m² at eight diving sites. The most important molluscs in the assemblage were the parasitic gastropod Coralliophila neritoidea, the encrusting gastropod Dendropoma maxima and the coral-associated bivalve Pedum spondyloideum. The dead assemblage, in contrast, was dominated by encrusting bivalves (Ostreoidea, Chamoidea, Spondylidae) and the coral-predating gastropod Drupella cornus. Distinct molluscan assemblages inhabit each of the three fringing reef-habitats and most of the important depth-related community changes occurred within the uppermost 5 m. In contrast, the three deeper fore-reef habitats are characterized by a more uniform molluscan composition. Molluscan assemblages were more dependent on substrata and their coral associations than on water depth. Comparisons with other published studies indicate that reefoidal hard substrata in the northern Red Sea are largely characterized by similar species-abundance patterns. The minor differences to other Red Sea studies probably reflect the northern, isolated position of the Gulf of Aqaba, the lack of certain molluscan habitats, and the differential impact of anthropogenic influences. Strong differences between living and dead assemblages in Aqaba are similar to those observed in other regions and are due to distinct biases in the dead assemblage. Molluscs closely associated with living corals (mostly bivalves and Dendropoma) can easily be overgrown after death and are thus undetectable in visual censuses. Some gastropod taxa are preferentially transported into surrounding soft-substrata postmortem or redistributed by hermit crabs. Such complex relationships between ecology and taphonomy are crucial in evaluating the quality of the molluscan fossil record in coral reef environments. The comparison of our results with literature data documents an increase in coral predators during the last two decades in the northern Red Sea. Due to the greater mollusc biodiversity in the shallower Aqaba reef habitats, damage to this coral reef zone would have the greatest impact on the overall mollusc community.

Palaeoenvironmental reconstruction based on non-geniculate coralline red algal assemblages in Miocene limestone of central Crete

Neogene coastal sediments of the Mediterranean provide an excellent laboratory for a quantitative study of palaeoenvironmental parameters and their response to climate change. In order to examine change in environmental parameters during deposition of Tortonian limestone of southern central Crete, we use integrated field and biofacies analysis together with a detailed study of foraminfera and non-geniculate red algae. Patterns in the relative abundance of non-geniculate coralline red algae are interpreted by comparison with data from modern non-geniculate coralline red algae and with additional information from the studied sediments. Based on these integrated datasets, four red algal associations are identified: a Lithophyllum-dominated association restricted to the upper photic zone in warm-temperate environments, a Lithothamnion-dominated association found in the lower photic zone in warm-temperate environments, a Spongites-dominated association typical for shallow warm-temperate to tropical environments and an association with dominant Mesophyllum which is characteristic for the lower photic zone in warm-temperate to tropical environments. We introduce coralline red algal indices in order to quantify changes in environmental parameters. We recognise four warm intervals within a succession of the Tortonian limestones in southern central Crete. During the most extensive interval, widespread coral carpets formed under prevalent oligotrophic conditions. Analysis of the stratigraphic architecture shows that warm intervals are related to sea-level highstands and therefore may reflect global climatic processes.

Coral communities of the northwestern Gulf of Aden (Yemen): variation in framework building related to environmental factors and biotic conditions

Coral communities were investigated in the northwestern Gulf of Aden, Yemen, for their composition, structure, and bioconstruction potential. Although no true reef was encountered, high cover coral carpets were found where hard substrate was available. Seven different types of coral communities were differentiated, and both non-framework and framework coral communities were found. Monotypy or oligotypy seem to be consistent characteristics of framework-building coral communities in the study area. Apart from substrate availability, proximity to the upwelling area and exposure were found to be the most important environmental factors influencing coral communities’ structure, composition, and bioconstruction potential.

Vertical versus horizontal growth strategies of coral frameworks (Tulamben, Bali, Indonesia)

Two different coral framework structures located in a shallow subtidal area on the east coast of Bali are described in this study. One structure is a typical coral carpet with a distinct internal succession of coral taxa and growth forms. It starts with a variety of coral species exhibiting massive, tabular, branching, and platy growth forms settling on volcanic boulders and cobbles. The main body of the coral carpet is composed almost monospecifically of Acropora cf. vaughani, which has filled all accommodating spaces up to the low-water sea level. Mostof this carpet died during the bleaching event of 1998 and the resultant dead Acropora framework is now capped by a platy Montipora assemblage. Some of the Acropora branches within the dead carpet, however, are still alive and display active growth. The Montipora cover protects the dead Acropora framework against mechanical and biological destruction. The few still growing Acropora branches may also contribute to the strength of the framework. The second coral framework is made up almost monogenerically of Montipora. One species of Montipora is of a laminar growth form and produces whorl-like colonies. Within this framework, only part of the Montipora colonies are dead; however, these are intensively fragmented. The fragments have been rapidly settled by a platy Montipora species, which has stabilized the fragments. In this case, the fragment shedding of the Montipora offers the opportunity for progradation of the framework on these fragments. Concerning the Acropora carpet, similar examples from the fossil record of the Miocene era of Spain and Austria have been reported.

Ludlow (Silurian) stromatoporoid biostromes from Gotland, Sweden: facies, depositional models and modern analogues

Stacked stromatoporoid‐dominated biostromes of the Ludlow‐age Hemse Group (Silurian) in eastern Gotland, Sweden, are 0·5–5 m thick and a few tens of metres to >1 km in lateral extent. They form one of the world's richest Palaeozoic stromatoporoid deposits. This study compiles published and new data to provide an overall facies model for these biostromes, which is assessed in relation to possible modern analogues. Some biostromes have predominantly in‐place fossils and are regarded as reefs, but lack rigid frameworks because of abundant low‐profile non‐framebuilding stromatoporoids; other biostromes consist of stromatoporoid‐rich rudstones interpreted here as storm deposits. Variation between these two `end‐members' occurs both between interlayered biostromes and also vertically and laterally within individual biostromes. Such variation produces problems of applying established reef classification terms and demonstrates the need for the development of terminology that recognizes taphonomic destruction of reef fabrics. An approach to such terminology is found in all four categories of a recent biostrome classification scheme that are easily recognized in the Hemse biostrome facies: autobiostromes (>60% in place); autoparabiostromes (a mixture of in‐place and overturned reef‐building organisms, 20–60% in place); parabiostromes (builders are overturned and damaged, <20% in place); and allobiostromes (transported and detrital reef material, nothing in place). These categories provide a broad taphofacies scheme for the Hemse biostromes, which are mostly autoparabiostrome to allobiostrome. The biostromes developed on crinoidal grainstone sheets and expanded laterally across relatively flat substrates in a marine setting of low siliciclastic input. Planar erosion surfaces commonly terminate biostrome tops. Three broadly similar modern analogues are identified, each of which has elements in common with the Hemse biostromes, but none of which is an exact equivalent: (a) laterally expanded and coalesced back‐barrier patch reefs behind the Belize barrier, an area influenced by limited accommodation space; (b) a hurricane‐influenced shelf, interpreted for Grand Cayman, where reef cores consist of rubble and lack substantial framework; the wide distribution of rounded pebbles and cobbles of stromatoporoids in the Hemse biostromes most probably resulted from hurricanes; (c) coral carpets in 5–15 m water depth of the northern Red Sea, where lateral expansion of low‐diversity frames dominated by Porites coral has produced low‐profile biostromes up to 8 m thick and several km long. Such carpets accumulated large amounts of carbonate, with little export, as in the Hemse biostromes, although the latter did not build frameworks because of the nature of growth of the stromatoporoids. The notable lack of algae in the Hemse biostrome facies is also a feature of Red Sea coral carpets; nevertheless, coral carpets are ecologically different. Hemse biostromes lack evidence of a barrier reef system, although this may not be exposed; the facies assemblage is consistent with either a storm/hurricane‐influenced mid‐ to upper ramp or back‐barrier system.

Book review of Littler DM. Littler MM (2000) Caribbean Reef Plants An Identification Guide to the Reef Plants of the Caribbean, Bahamas, Florida and Gulf of Mexico

Information on spatial variability and distribution patterns of organisms in coral reef environments is necessary to evaluate the increasing anthropogenic disturbance of marine environments (Richmond 1993; Wilkinson 1993; Dayton 1994). Therefore different types of subtidal, reef-associated hard substrata (reef flats, reef slopes, coral carpets, coral patches, rock grounds), each with different coral associations, were investigated to determine the distribution pattern of molluscs and their life habits (feeding strategies and substrate relations). The molluscs were strongly dominated by taxa with distinct relations to corals, and five assemblages were differentiated. The Dendropoma maxima assemblage on reef flats is a discrete entity, strongly dominated by this encrusting and suspension-feeding gastropod. All other assemblages are arranged along a substrate gradient of changing coral associations and potential molluscan habitats. The Coralliophila neritoidea–Barbatia foliata assemblage depends on the presence of Porites and shows a dominance of gastropods feeding on corals and of bivalves associated with living corals. The Chamoidea–Cerithium spp. assemblage on rock grounds is strongly dominated by encrusting bivalves. The Drupella cornus–Pteriidae assemblage occurs on Millepora–Acropora reef slopes and is strongly dominated by bivalves associated with living corals. The Barbatia setigera–Ctenoides annulata assemblage includes a broad variety of taxa, molluscan life habits and bottom types, but occurs mainly on faviid carpets and is transitional among the other three assemblages. A predicted degradation of coral coverage to rock bottoms due to increasing eutrophication and physical damage in the study area (Riegl and Piller 2000) will result in a loss of coral-associated molluscs in favor of bivalve crevice dwellers in dead coral heads and of encrusters on dead hard substrata.