Coral Material Research Articles

Structural and hydrodynamic modelling of the probability of breakage of branching and plate coral colonies

Climate change is amplifying the intensity of severe weather events, with coastal regions such as coral reefs facing heightened vulnerability to cyclonic wave forces. Structural models to predict bending stress and breakage of corals have been developed for coral colonies to enhance comprehension and prediction of the effects of hydrodynamic disturbances on coral reefs. However, there is scope for improving these predictions by evolving the methodology for quantifying complicated and variable coral morphologies. This study aims to predict breakage thresholds for two of the most prevalent coral morphologies: branching and plate corals (using Acropora muricata and Acropora hyacinthus as study species). Laboratory and field measurements were taken to assess coral morphologies and material characteristics. Morphological features of 47 branching colonies and 100 plate colonies were surveyed at the study site (Heron Reef, southern GBR) and the tensile strength of 80 coral samples was obtained by in situ and laboratory testing. Three-dimensional structural models of branching and plate coral colonies were developed, encompassing multiple coral colonies with varying morphological patterns from relatively shallow (5-7 m) to deep (9-12 m) zones. Model results were calibrated and verified with existing data, revealing that velocity thresholds of 1.7 m/s and 5.0 m/s would destroy 90% of the simulated branching coral structures growing in the deep and shallow parts of the forereef zone, respectively. In contrast, the plate corals have sufficient margins of safety even in extreme flow conditions (7 m/s). Additionally, skeletal strength and structural performance were adjusted based on varying degrees of bioerosion inside the coral skeleton. A higher probability of breakage was observed as the extent of bioerosion increased. The laboratory experiments of hydrodynamic loads on coral colony show that the sheltering effect due to one or two neighbouring colonies in the upwave direction is negligible. These models can be easily adjusted to provide predictions for other coral species, shapes, levels of bioerosion, and locations (e.g., sheltered or exposed areas). Comprehensive predictions about the level of expected damage and rubble generation in different areas can be used in reef management planning and restoration prioritization.

Cross-cultural approach to biobanking of living coral cells on Woppaburra sea Country in the southern inshore Great Barrier Reef

ABSTRACT Biobanking of cryopreserved, living cells is a conservation tool being increasingly integrated into management and recovery efforts for at-risk wildlife. Together with reproductive technologies like in-vitro fertilisation, biobanking can secure biodiversity for decades and beyond to support species’ health and ability to survive and recover in a changing world. An inaugural on-Country coral biobanking project occurred in 2022 on Konomie (North Keppel Island) involving partners from Taronga Conservation Society, the Australian Institute of Marine Science and Woppaburra Traditional Custodians. Biobanking activities were undertaken with free prior and informed consent for the collection, cryopreservation and transfer of living coral material for secure and specialised storage at Taronga’s CryoDiversity Banks on Cammeraygal and Wiradjuri Countries. During this project and a subsequent Biobanking Cultural Safety event in September 2023, we discussed cultural matters related to biobanking and measures that could be taken to ensure that the enduring link to Country of these samples is maintained in perpetuity. These outcomes will form the basis of a best-practice approach to biobanking activities in other regions of the Great Barrier Reef, in partnership with the Traditional Custodians of those sea Countries.

Coral mariculture using abandoned abalone farming ponds in northeastern Taiwan

Stony corals are ecologically and economically important marine organisms. Coral aquaculture is essential to provide live coral materials for the marine ornamental trade, reef restoration programs, and environmental education. This study sought to establish coral farms in Taiwan. To culture corals, we adopted an abandoned abalone farming pond built along the northeastern coast of Taiwan, and investigated whether it is possible to propagate corals in this artificial environment. Stainless steel underwater tables were anchored to the pond floor, and fragments of Acropora tumida, Pocillopora damicornis, Stylophora pistillata, Favites pentagona, and Porites lobata were cultured on the tables for one year. Environmental factors in the pond were also monitored. The mean surface temperature was 23.07 °C, ranging from >30 °C in summer to 18 °C in winter. The mean salinity and pH were about 35 ppt and 8.14, respectively. Survivorship of these five species after one year ranged from 100% to 67%, with a 1.37–1.51-fold increase in weight and a 3.22–3.38-fold increase in area, demonstrating that although environmental factors fluctuate depending on the season and weather, long-term and stable asexual propagation of corals is feasible in the pond. For further optimization of culture conditions, the effects of initial fragment size for culture on subsequent survival and growth were investigated. Fragments of 3 sizes (1.5, 3.0, and 4.5 cm) were prepared from parental colonies of A. tumida, P. damicornis, and S. pistillata and cultured for 6 months by hanging them under the table. There were no significant differences in survivorship among these sizes. Differences were observed in biomass (weight) increase. In A. tumida, 3-cm fragments showed significantly more weight gain than other lengths, while 1.5-cm fragments showed a significant weight increase in P. damicornis. In S. pistillata, no significant difference in weight increase was observed among size groups, suggesting the necessity to optimize the initial fragment size for culture for each species before mass culture. Histological analysis showed that mature gametes were formed in some cultured corals, suggesting that sexual propagation may also be possible in the future. The established coral farm, which is culturing >4000 coral fragments now, will be able to support not only basic and applied coral research, but also sustainable reef development and marine ornamental trade.

Propagating the stony coral Echinopora horrida: evaluating the effects of rearing environment and transplant orientation

The “coral gardening” approach has been effective in facilitating the recovery of degraded reefs but methodological variations can influence survivorship and growth of the coral material. In addition, the disproportionate use of certain corals, such as acroporids and pocilloporids, has contributed to a general lack of information on growth patterns and restoration strategies for species that are less common. To investigate how the yield of other species may be increased to support reef restoration efforts in Singapore, we assessed the effects of (1) environment (nursery, reef, and seawall) and (2) transplant orientation (horizontal and vertical) on the performance of Echinopora horrida (Dana, 1846) fragments. Fragments secured in the coral nursery grew significantly faster and survived better than those transplanted on the reef and seawall, highlighting the importance of a nursery‐rearing phase in optimizing the yield of this species. Additionally, survivorship and growth rates were not significantly different between vertically and horizontally transplanted corals, suggesting that modifying transplant orientation was less crucial toward enhancing coral yield. Our findings highlighted the need to optimize the propagation techniques of a wider range of understudied coral species in order to preserve their genetic diversity in the face of anthropogenic and climatic impacts.

Impacts of plastic-free materials on coral-associated bacterial communities during reef restoration.

Coral propagation and out-planting based restoration approaches are increasingly being applied to assist natural recovery of coral reefs. However, many restoration methods rely on plastic zip-ties to secure coral material which is potentially problematic for the marine environment. Plastic-free biodegradable alternatives may however pose unique risks to coral-associated bacterial communities integral to coral health. Therefore, to identify whether biodegradable materials differentially impact coral-associated bacterial communities we examined Acropora millepora coral-associated bacterial communities during propagation in two experiments on the Great Barrier Reef. Coral fragments were secured to coral nurseries with conventional plastic, metal, or biodegradable (polyester and polycaprolactone) ties. Tie failure and coral-associated bacterial communities were then characterized over six months. Minimal coral mortality was observed (3.6%-8%) and all ties had low failure rates (0%-4.2%) except for biodegradable polyester ties (29.2% failure). No differences were observed between coral-associated bacterial communities of fragments secured with different ties, and no proliferation of putatively pathogenic bacteria was recorded. Overall, our findings suggest that reducing reliance on conventional plastic is feasible through transitions to biodegradable materials, without any notable impacts on coral-associated bacterial communities. However, we caution the need to examine more coral taxa of different morphologies and new plastic-free materials prior to application.

Properties and Microcosmic Mechanism of Coral Powder Modified Asphalt in Offshore Islands and Reefs Construction

The application of waste coral fragments from natural weathering, harbor construction and channel excavation to infrastructure construction on offshore islands can help alleviate the problems of shortage of traditional materials, land use of waste materials, and long-distances transport. In order to promote the comprehensive application of coral materials in road engineering construction on offshore islands, and to develop road pavement materials with good service performances and economic and environmental benefits, this paper studies the base properties, high-temperature rheological properties, and microstructure of coral powder (CP) modified asphalt through indoor experiments. The base properties tests (penetration, softening point and ductility) showed that the incorporation of CP increased the stiffness and high-temperature stability of the asphalt, but decreased the ductility of the asphalt. The optimal dosing of CP in virgin asphalt (VA) and styrene-butadiene-styrene-modified asphalt (SA) is 12% and 15%, respectively. The results of viscosity and high-temperature rheology tests showed that the right amount of CP could improve the high-temperature rheological properties and resistance to permanent deformation of asphalt, but superfluous CP tends to have a negative effect. Microscopic test results show that in the recommended dosage, the combination effect of CP and asphalt is better. CP-modified asphalt is mainly based on physical modification.

The sacred stone from the sea. Archaeological and ethnographic perspectives on the ritual value of coral across the Pacific

ABSTRACTThe Pacific Islands offer a variety of marine environments providing peoples in the present and past with abundant coral materials, a “stone from the sea”. Archaeologists have long recognised the importance of coral in ancient contexts, whether as gravel, natural branches, squared blocks or cut‐and‐dress slabs. Coral was also used to manufacture tools such as files or pounders and incorporated in monumental ceremonial architecture as a favoured construction material and foundation offerings. However, Pacific Islanders also employed coral material for other ritual applications that remain overlooked in the literature. In this article, we consider the multiple uses of coral in the archaeological and ethnographic records of three Pacific regions: Central‐East Polynesia (CEP), New Caledonia and the Torres Strait Islands. This includes offering of coral branches, sometimes associated with cairns, paraphernalia and magic stones, also production of coral lime for body ornamentation. Using these case studies, we consider material selection, modes of deposition, archaeological and ethnographic contexts, associations with other features and artefacts, before interrogating the potential significance of these unrealised datasets. By doing so, we shed new light on the ritual value of coral and reflect on the symbolic nature and function of this material.

Evaluasi Sisa Material Pada Pembangunan Gedung Kantor Kejaksaan Tinggi Jambi

In the Jambi High Prosecutor's Office Building Construction Project, remnants of project materials were found. Waste material is one of the serious problems in the implementation of construction projects. Therefore, it is necessary to do a careful and precise calculation in determining the amount of material needed to be used in the project as well as an evaluation of the use of these materials. The aim of this research is; calculate the largest percentage of material waste costs during project implementation, identify the causes of material waste, and find ways to minimize material waste after conducting analysis and evaluation. The method used is a sociological juridical type, which is a type or type of research that emphasizes field research. To obtain data in the field by conducting interviews with the project supervisory consultant and data on images and photos of the project. The result of the observation of processed data is that the largest percentage of residual material costs is obtained from the concrete coral material with the highest percentage of 26.553% of the total cost of the remaining material. As for the causes of material remnants on the job, the first is coming from the factor of throwing or throwing material, workers in the field often throw material such as when casting columns and beams where a lot of concrete is wasted out of the formwork, another cause occurs in the skill factor Based on the skills of workers, there are some remnants of boards from making formwork on columns and beams. And also when cutting iron, a lot of iron can't be reused because the rest of the iron that is cut is too small. The conclusion is that there is residual material in this project from the factor of throwing or throwing material carried out by workers and on the skill factor of the worker.

Coral Hydrate, a Novel Antioxidant, Improves Alcohol Intoxication in Mice.

Alcohol-drinking culture may cause individuals to periodically experience unpleasant hangovers. In addition, ethanol catabolism stimulates the production of free radicals that may cause liver injury and further lead to the development of chronic alcoholic fatty liver disease. Although a number of studies have suggested that hydrogenated water may be consumed to act as free radical scavenger, its instability limits its application. In this study, we used coral hydrate (i.e., hydrogenated coral materials) as a more stable hydrogen source and evaluated its effects in a murine model of alcohol intoxication. In solution, coral hydrate exhibited much more stable redox potential than did hydrogenated water. Furthermore, administration of coral hydrate by oral gavage significantly prolonged the time to fall asleep and decreased the total sleep time in mice that received intraperitoneal injection of ethanol. The mice receiving coral hydrate also had lower plasma ethanol and acetaldehyde levels than controls. In line with this observation, hepatic expression of alcohol dehydrogenase, acetaldehyde dehydrogenase, catalase and glutathione peroxidase were all significantly increased by the treatment. Meanwhile, alcohol-induced upregulation of pro-inflammatory factors was attenuated by the administration of coral hydrate. Taken together, our data suggest that coral hydrate might be an effective novel treatment for alcohol intoxication.

Determination of Land Characteristics for Tongka Langit Banana Plant (Musa troglodytarum L.) in Ambon Island

The research was conducted in the villages of Eri, Soya, Kusu-kusu, Waai, Hatu, and Allang of Ambon Island. The aim of this study was to determine the external and internal characteristics of the location for growing Tongka Langit banana (M.roglodytarum L). The method used was a survey method with a free survey observation distance. The results showed that the characteristics of the external land where the Tongka Langit banana plant grows are scattered on the slopes of the foothills with the geology of alluvium, limestone, coral, granite, and loose material. Banana cultivation was associated with mixed garden land use with dominant slopes ranging from flat to gentle (2 - 9%). The research location has a dew point of 24.5 oC - 26.5 oC, humidity 75% - 91%. The internal soil characteristics are as follows: Soil textured slightly coarse to slightly fine, soil reaction was between 6.15 – 7.49, C-organic content was 0.69 - 10.08%, total N content was 0.10 - 0.59 %, C/N ranged from 5-59, P2O5 content was 11-18 ppm, K2O content ranged from 212-295 ppm, and cation exchange capacity was 6.52-24.48 me/100gr.

Coral-ID: A forensically validated genetic test to identify precious coral material and its application to objects seized from illegal traffic

The production and trade of objects manufactured from the skeletal axis of coralid precious corals is a historically, culturally and economically important global industry. Coralids are members of the diverse Coralliidae family, which contains several species complexes and morphospecies. For most precious coral found in the jewelry trade, the color remains the sole clue and link to the taxonomic identity of the individual. Different coralid species have however similar or overlapping colors resulting in difficulty to taxonomically identify jewelry objects, including four species listed by the Convention on the International Trade of Endangered Species (CITES) whose international transport and trade requires species-specific and country of origin documentation. We aimed at developing a reliable method to taxonomically identify coralid material with the objective of distinguishing CITES protected species from their non-protected counterparts. We present Coral-ID, a genetic assay to taxonomically classify coralid objects using quasi non-destructive sampling. The assay classifies the analyzed sample in one of six taxonomic categories and performs at least presumptive separation of CITES-listed and non-listed species in all cases. Developmental validation experiments prove that Coral-ID is a specific, accurate and very sensitive method. As the first attempt to randomly sample corals in the trade to identify them, we applied Coral-ID on 20 precious coral objects seized by custom authorities upon import to in Switzerland. Thirteen (65%) of these samples could be analyzed; three of these were found to be presumptively CITES-listed, and 10 of them have proven to originate from non-CITES-listed species.

Effects of Mineral Admixtures on Chloride Diffusion in Environment-Friendly Coral Aggregate Concrete

Coral materials can replace concrete aggregates and achieve material self-sufficiency for reducing the construction costs of island projects. This paper studies the effects of different mineral admixtures on the properties of coral aggregate concrete (CAC). The chloride concentration of CAC after different erosion times is measured using the potentiometric method, and the porosity of the CAC is calculated using thermogravimetric and drying methods. The chloride concentration of the CAC presents a two-phases distribution. The peak chloride concentration followed a power function, increasing with the erosion time. The chloride diffusion coefficient of CAC is 7.9%– 37.5% larger than that of ordinary aggregate concrete, and the addition of 15% fly ash and 5% silica fume can significantly reduce the chloride diffusion coefficient, with a maximum reduction of 45.0%. The porosity obtained via the thermogravimetric and drying methods is well correlated. The porosity has a strong negative correlation with the compressive strength and a strong positive correlation with the chloride diffusion coefficient.

The Palaeo-Kambaniru river mouth, Sumba, East Nusa Tenggara, Indonesia: A record of strongly seasonal catastrophic flow in a monsoon-controlled deltaic complex

The Kambaniru River valley near the city of Waingapu preserves a thick succession of coarse-grained fluvial-deltaic sediment deposited during the Late Pleistocene. This succession incises through a thick uplifted coral reef terrace succession and records intervals of highly episodic flow events during the last glacial interval. The occurrence of intraclastic, coarse sand/gravel matrix olistostromes in several areas attests to the occasionally catastrophic nature of flow in the ancestral Kambaniru River. Small to moderate-sized coral-rich reefs and laterally restricted reef terraces occur on delta-front conglomerate successions at multiple horizons through the study interval. These reefs record both intervals of low flow as well as periodic river-mouth avulsion episodes. Comparison of radiometric dates obtained from pelecypod and coral material from both deltaic successions and laterally adjacent coral reef terrace intervals indicates that uplift/subsidence history of the terraces differs from that of the valley and that correlation between the two should be taken with care.

Effects of Ice Freeze-Thaw Processes on U Isotope Compositions in Saline Lakes and Their Potential Environmental Implications

The dissolved uranium (U) content in the water column of saline lakes varies little between ice-free seasons throughout the whole water column. Such uniformity allows for the potential absolute dating and/or paleohydrologic interpretations of lake sediments and biogenic shell materials using U isotopes. Before using these methods in cold regions, however, it is necessary to evaluate the effects that ice freeze-thaw processes have on the distribution of U isotopes in saline lake waters, and to determine the amount of variation in U isotopic values when such processes occur. In this paper, we collected ice and dissolved water samples from six lakes with variable salinity in February 2021. Five groundwater and three water samples from rivers into Qinghai Lake were sampled in November 2020. The sampled water was analyzed for dissolved concentrations of 238U and the activity ratio of 234U/238U ([234U/238U]AR). The results show that the 238U concentration of ice samples was less than that of the underlying water. The [234U/238U]AR of ice in the five saline lakes was similar to that of the underlying water with less than a 10‰ variation, suggesting no observable fractionation between ice and dissolved water. Thus, the ice freeze-thaw processes have almost no effect on the uranium content and [234U/238U]AR of the sampled saline lakes, which were characterized by a limited recharge volume from surface runoff, groundwater, and ice volume, namely the close saline lake in arid alpine background. The results from the indoor freeze-thaw experiments also showed that the U isotopic composition of Qinghai Lake waters and ice were similar with the 238U concentration of the ice was about 40% of that of the dissolved lake water, supporting the data obtained from natural saline lakes. The above results provide important insights into whether it is feasible to use U isotopes for absolute dating and/or paleohydrologic analysis of lake sediments or biogenic shell materials. In addition, the results are important for evaluating the [234U/238U]AR and uranium concentrations in seawater when there exists a process of melting polar ice, and for determining the initial delta 234U variations needed for dating of coral and other fossil materials.

Scleractinian corals of the Albian (uppermost Lower Cretaceous)—overview, revision, evaluation

In the current study, scleractinian corals from the Albian (uppermost Lower Cretaceous; 112.6–99.7 Ma) including 337 species (280 taxa assigned to species; 57 taxa kept in open nomenclature) from 147 genera (six of which include subgenera) belonging to 42 families (two of which include subfamilies; and incertae sedis) are evaluated and revised. Two new species (Apoplacophyllia asiatica, new species and Trigerastraea sikharulidzeae, new species) are described and two lectotypes are designated. Some specimens are illustrated for the first time, and new material (from Austria) is presented. The coral material includes records from 30 regions in Africa, the Americas, the Arctic, Asia, Australasia, and Europe. The most extensive records of Albian corals are from tropical/subtropical and arid areas, including the U.S.A., Mexico, Greece, France, and Spain. Over three-quarters of the Albian taxa belong to morphological forms having little to no hermatypic character (sensu Coates & Oliver), including species of the cerioid-plocoid group (genera: 36.7%; species: 38.5%), solitary taxa (genera: 26.5%; species: 28%), and branching forms (genera: 26.5%; 39 species = 11.5%). The coral faunas of the Albian are dominated by corals of “modern” microstructural groups sensu Roniewicz & Morycowa (76 genera = 51.7%; 169 species = 50.1%). Compared to the lowermost Cretaceous (Berriasian), which showed that 91% of the species and 83% of the genera belonged to previously established microstructural groups, the Lower Cretaceous ends with “modern” groups having become dominant. During the lower and middle Albian, the vast majority of taxa belonged to colonial forms (both 74%). A shift took place during the upper Albian, significantly increasing the number of solitary species to over 40% of the Albian fauna (42.9%). Throughout the Albian, the most diverse coral assemblages include non-reefal faunas, suggesting that, in contrast to, e.g., the Barremian–Aptian time period, reefal developments were less crucial for coral recruitment during this time. This study of the Albian fauna was used as the basis for synthesizing classical taxonomic works with modern microstructural data and recent DNA analyses in order to propose both a modified taxonomic framework and a working hypothetical phylogenetic tree for 41 scleractinian families occurring in the fossil record.

Axial compression performance of coral concrete-filled aluminium tube (CCFAT) square stub columns

Coral materials have been used as concrete aggregate for decades to achieve self-sufficiency of materials and reduce costs of island construction. Considering the aggressive environment of islands, filling concrete into steel tube to produce coral concrete-filled steel tube (CCFST) columns is impractical. The combination of concrete and aluminium tube is proposed to avoid steel corrosion and optimize concrete performance in island construction. This study experimentally investigated the axial compression performance of nine coral concrete-filled aluminium tube (CCFAT) square stub columns. The failure mode, load-carrying capacity, and load-deformation relations were obtained, and the effects of concrete strength (fc), aluminium ratio (α), and confinement factor (ξ) on the strength, stiffness, and ductility performance were discussed. Moreover, the adaptability of concrete-filled steel tube (CFST) design codes in the load-carrying capacity prediction of CCFAT square stub columns was assessed. The results show that the increase in α mostly improves the strength index (SI) and stiffness index (KI) while the effects of fc is less significant. The ductility index (DI) and composite action are closely correlated to ξ. Using the design equation in AIJ code to predict the load-carrying capacity of CCFAT square stub columns is acceptable.

A review of coral bleaching specimen collection, preservation, and laboratory processing methods.

Under current climate warming predictions, the future of coral reefs is dire. With projected coral reef decline, it is likely that coral specimens for bleaching research will increasingly become a more limited resource in the future. By adopting a holistic approach through increased collaborations, coral bleaching scientists can maximize a specimen’s investigative yield, thus reducing the need to remove more coral material from the reef. Yet to expand a specimen’s utility for additional analytic methods, information on how corals are collected is essential as many methods are variably sensitive to upstream handling and processing. In an effort to identify common practices for coral collection, sacrifice, preservation, and processing in coral bleaching research, we surveyed the literature from the last 6.5 years and created and analyzed the resulting dataset of 171 publications. Since January 2014, at least 21,890 coral specimens were collected for bleaching surveys or bleaching experiments. These specimens spanned 122 species of scleractinian corals where the most frequently sampled were Acropora millepora, Pocillopora damicornis, and Stylophora pistillata. Almost 90% of studies removed fragments from the reef, 6% collected skeletal cores, and 3% collected mucus specimens. The most common methods for sacrificing specimens were snap freezing with liquid nitrogen, chemical preservation (e.g., with ethanol or nucleic acid stabilizing buffer), or airbrushing live fragments. We also characterized 37 distinct methodological pathways from collection to processing of specimens in preparation for a variety of physiological, -omic, microscopy, and imaging analyses. Interestingly, almost half of all studies used only one of six different pathways. These similarities in collection, preservation, and processing methods illustrate that archived coral specimens could be readily shared among researchers for additional analyses. In addition, our review provides a reference for future researchers who are considering which methodological pathway to select to maximize the utility of coral bleaching specimens that they collect.

The Effect of the Use of Local Papua Coard Aggregate on AC-WC Laston Stability Value

Coarse aggregates derived from rock are commonly used as road pavement materials that meet the applicable specifications. This study uses rock aggregates originating from the polymeric area of Jayapura City, and this type is widely found in various areas of northern Papua. The study was conducted to determine the effect of local Papuan coral aggregates on the AC-WC Laston value. According to the 2018 General Specifications of Highways; namely, the added filler material must be dry and free from clumps and when tested by sieving according to SNI ASTM C136: 2012. The test results obtained characteristic values on the use of coral as follows: The highest density value at 4.5% asphalt content and the lowest 5.5% and 6.5%. The VMA value obtained is unstable, but all asphalt content meets Bina Marga Specifications 2010 Revision III, namely with a minimum VMA value of 15%, the highest VIM value of 3-5%, VFA values tend to increase but experience a decrease in asphalt content of 5.5% and 6.5%. The results of the Marshall test on coral material in the AC-WC layer are the high strength value 5495.89 kg, density: 1.74 gr/cm3, VMA: 24.42%, VIM: 15.83 %, VFA: 0.01%, flow: 10.00 mm, and MQ of 348.03 mm/kg. The value of Optimum Asphalt Content (KAO) used as AC-WC layer is 5.5%.

Commentary: Early Diagenetic Imprint on Temperature Proxies in Holocene Corals: A Case Study From French Polynesia

Coral-based reconstructions of sea surface temperatures (SSTs) using Sr/Ca, U/Ca and δ 18 O are important tools for quantitative analysis of past climate variabilities. However, post-depositional alteration of coral aragonite, particularly early diagenesis, restrict the accuracy of calibrated proxies even on young corals. Considering the diagenetic effects, we present new Mid to Late Holocene SST reconstructions on well-dated (U/Th: ∼70 yr to 5.4 ka) fossil Porites sp. collected from the Society Islands, French Polynesia. For few corals, quality pre-screening routines revealed the presence of secondary aragonite needles inside primary pore space, resulting in a mean increase in Sr/Ca ratios between 5-30%, in contrast to the massive skeletal parts. Characterized by a Sr/Ca above 10 mmol/mol, we interpret this value as the threshold between diagenetically altered and unaltered coral material. At a high-resolution, observed intra-skeletal variability of 5.4 to 9.9 mmol/mol probably reflects the physiological control of corals over their trace metal uptake, and individual variations controlled by CaCO 3 − precipitation rates. Overall, the Sr/Ca, U/Ca and δ 18 O trends are well correlated, but we observed a significant offset up to ± 7 • C among the proxies on derived palaeo-SST estimates. It appears that the related alteration process tends to amplify temperature extremes, resulting in increased SST-U/Ca and SST-Sr/Ca gradients, and consequently their apparent temperature sensitivities. A relative SST reconstruction is still feasible by normalizing our records to their individual mean value defined as SST. This approach shows that SST records derived from different proxies agree with an amplitudinal variability of up to ± 2 • C with respect to their Holocene mean value. Higher SST values than the mean SSTs (Holocene warm periods) were recorded from ∼1.8 to ∼2.8 ka (Interval I), ∼3.7 to 4.0 ka (Interval III) and before ∼5 ka, while lower SST values (Holocene cold periods, Interval II and IV) were recorded in between. The ensuing SST periodicity of ∼1.5 ka in the Society Islands record is in line with the solar activity reconstructed from 10 Be and 14 C production (Vonmoos et al., 2006), emphasizing the role of solar activity on climate variability during the Late Holocene.

Upper Barremian-lower Aptian scleractinian corals of central Europe(Schrattenkalk Fm., Helvetic Zone, Austria, Germany, Switzerland).

From the Schrattenkalk Formation (upper Barremian-lower Aptian) of southern Germany, western Austria, and Switzerland, new coral material is taxonomically described, belonging to 56 species from 35 genera of 21 families: Actinastrea pseudominima (Koby); A. subornata (d'Orbigny); Paretallonia bendukidzeae Sikharulidze; Eugyra (Felixigyra) crassa (de Fromentel) (new combination); E. (F.) patruliusi (Morycowa); E. (F.) picteti (Koby) (new combination); E. rariseptata Morycowa; Myriophyllia propria Sikharulidze; Thecosmilia dichotoma Koby; Clausastrea plana (de Fromentel); Complexastrea cf. lobata Geyer; Paraclausastrea chevalieri Zlatarski; P. kaufmanni (Koby); P. vorarlbergensis Baron-Szabo; ?Montlivaltia sp.; Diplogyra subplanotabulata Sikharulidze; Hydnophora styriaca (Michelin); Dermosmilia fiagdonensis Starostina Krasnov; D. cf. laxata (Étallon); D. trichotoma Eguchi; D. tuapensis Baron-Szabo Gonzalez.-León; Placophyllia grata Bugrova; Cairnsipsammia merbeleri Baron-Szabo; Morphastrea ludovici (Michelin) (emended herein); Ahrdorffia ornata (Morycowa); Astraeofungia tirnovoriana (Toula) (new combination); Actinaraea (Camptodocis) brancai (Dietrich); A. tenuis Morycowa; Rhipidomeandra bugrovae Morycowa Masse; Comoseris aptiensis Baron-Szabo; Comoseris jireceki Toula; Polyphylloseris mammillata Eguchi; Ellipsocoenia barottei (de Fromentel) (new combination); Ellipsocoenia haimei (de Fromentel) (new combination); Dimorphastrea tenustriata de Fromentel; Latomeandra cf. plicata (Goldfuss); Microphyllia gemina Eliášová; Thalamocaeniopsis stricta (Milne Edwards Haime)(new combination); Trigerastraea haldonensis (Duncan) (new combination); Heliocoenia rozkowskae Morycowa; H. vadosa (Počta); Stylosmilia corallina Koby; Cyathophora decipiens ramosa (Hackemesser) (new combination); C. mirtschinkae Kuzmicheva; Cladophyllia clemencia de Fromentel; C. conybearei Milne Edwards Haime; C. crenata (Blanckenhorn); C. furcifera Roemer; C. rollieri (Koby); C. stutzi (Koby) (new combination); Amphiaulastrea conferta (Ogilvie); A. rarauensis (Morycowa); Heterocoenia inflexa (Eichwald); H. minima d'Orbigny; Acanthogyra aptiana Turnšek; as well as the new species Columnocoenia falkenbergensis. In addition, all the information about previously described taxa from the Schrattenkalk was evaluated with regard to their taxonomic assignment, stratigraphic and paleogeographic distribution, and paleoenvironmental relationships to faunas from other geographic areas and time periods. A total of 122 species belonging to 53 genera and 24 families are recognized from Schrattenkalk localities (western Austria, southern Germany, Switzerland). These include the taxa of both the Lower and Upper Schrattenkalk, and the intercalated Rawil Member. The Schrattenkalk coral fauna nearly exclusively consists of colonial forms of three general categories of polyp integration: cerioid-plocoid (33.6%); branching (18%); and (hydno-) meandroid-thamnasterioid (46.7%). Only two specimens were doubtfully assigned to solitary taxa. Corallite diameters range from less than 1 mm to over 20 mm and fall into three major corallite-size groups: small (up to 2.4 mm), medium (2.4-9.5 mm), and large (9.5 mm). The fauna is distinctly dominated by forms with medium-size corallites (68%), followed by forms having small-size corallites (26%). Together with the potential solitary taxa, corals with large-size corallites are of minimal importance to the total fauna. On the genus-level, the Schrattenkalk corals show closest affinities to coral assemblages of central (especially France; 55%), eastern and southern Europe (44‒49%), as well as Central America (47%). On the species-level, closest affinities are to coral assemblages of central, southeastern, and eastern Europe (16‒25.5%), as well as Central America (14%), but nearly a third of the Schrattenkalk species (30%) was restricted to the upper Barremian-lower Aptian of the Schrattenkalk Formation; this suggests that the Schrattenkalk platform sensu lato was a diversity center and a crucial reservoir for coral recruitment. The majority (86%) of the Schrattenkalk corals thrived in a shallow-water, reefal to perireefal, subtropical marine environment. In general, the Schrattenkalk coral assemblages are characteristic of moderate- to high-energy environments of the inner shelf to shore zone, having morphotype associations that typically prevail down to 10-15 m depth. In contrast, for the Upper Schrattenkalk coral fauna of central Switzerland (Hergiswil), a non-reefal paleoenvironment at a depth of several tens of meters is suggested by the morphotypes of the taxa and types of microfacies present. The corals of the Schrattenkalk Formation occurred in both photozoan (Lower and Upper Schrattenkalk members) and heterozoan (Rawil member) carbonate-producing communities. With regard to taxonomic diversity, the Schrattenkalk coral fauna is comparable to the most species-rich Upper Jurassic reef assemblages and represents the last major coral-reef development of the Mesozoic.