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Sponge bioerosion is an important process on many carbonate reef ecosystems. Eutrophication has been linked with an increase in boring sponge abundance and biomass in coral reefs, yet the impacts on sponge bioerosion rates remain largely unexplored within oyster reef communities. The present study evaluated the impacts of nitrate and phosphate addition on the bioerosion of Cliona celata inhabiting carbonate substrates in the subtropical southeastern U.S. Using in situ and aquarium manipulations, sponge bioerosion rates were compared among control and nutrient addition treatments in three experiments. Overall, there were no differences in loss of calcium carbonate substrate among treatments in any of the experiments, though very high rates of bioerosion (up to 0.11 g CaCO3 day-1) were observed in the field experiments. Future research should consider the impacts of both inorganic and organic nutrient loading to fully understand the impacts of eutrophication on boring sponge ecology in subtropical oyster reefs.

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As the balance between erosional and constructive processes on coral reefs tilts in favor of framework loss under human-induced local and global change, many reef habitats worldwide degrade and flatten. The resultant generation of coral rubble and the beds they form can have lasting effects on reef communities and structural complexity, threatening the continuity of reef ecological functions and the services they provide. To comprehensively capture changing framework processes and predict their evolution in the context of climate change, heavily colonized rubble fragments were exposed to ocean acidification (OA) conditions for 55 days. Controlled diurnal pH oscillations were incorporated in the treatments to account for the known impact of diel carbonate chemistry fluctuations on calcification and dissolution response to OA. Scenarios included contemporary pH (8.05 ± 0.025 diel fluctuation), elevated OA (7.90 ± 0.025), and high OA (7.70 ± 0.025). We used a multifaceted approach, combining chemical flux analyses, mass alteration measurements, and computed tomography scanning images to measure total and chemical bioerosion, as well as chemically driven secondary calcification. Rates of net carbonate loss measured in the contemporary conditions (1.36 kg m-2 year-1) were high compared to literature and increased in OA scenarios (elevated: 1.84 kg m-2 year-1 and high: 1.59 kg m-2 year-1). The acceleration of these rates was driven by enhanced chemical dissolution and reduced secondary calcification. Further analysis revealed that the extent of these changes was contingent on the density of the coral skeleton, in which the micro- and macroborer communities reside. Findings indicated that increased mechanical bioerosion rates occurred in rubble with lower skeletal density, which is of note considering that corals form lower-density skeletons under OA. These direct and indirect effects of OA on chemical and mechanical framework-altering processes will influence the permanence of this crucial habitat, carrying implications for biodiversity and reef ecosystem function.

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As in most colonial and sessile marine invertebrates, bryozoan life history is characterized by asexual propagation of zooids for colonial growth and by sexual production of larvae for dispersal. However, comprehensive life histories, particularly in cryptic species such as endolithic (boring) bryozoans, remain poorly understood. The ctenostome family Penetrantiidae is widespread from temperate to tropical waters and often found in molluscan shells, offering an opportunity to study the boring lifestyle and its potential impact on bioerosion through growth and settlement experiments. Our research focused on Penetrantia clionoides from Guam in the Pacific Ocean, Penetrantia japonica from Japan, and a Penetrantia species from France in the Atlantic Ocean. We found distinct life histories and reproductive patterns potentially influenced by environmental factors such as temperature and food availability. The tropical P. clionoides displayed higher rates of larval production and growth compared to its temperate counterpart. For instance, the mean stolon extension was 335.2 µm/week in P. clionoides versus 232.1 µm/week in Penetrantia sp. Autozooid development took 13 days in P. clionoides and 31 days in Penetrantia sp. Anatomical features like apertural rims aided in species identification and in understanding larval settlement preferences, suggesting a tendency for philopatric settlement behavior. The bioerosional impact of penetrantiids remains little understood, but we generated first projections of bioerosion rates and a protocol for keeping Penetrantia under laboratory conditions, laying a foundation for further research in this field.

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The bone-eating worm Osedax is a speciose and globally distributed clade, primarily found on whale carcasses in marine environments. The earliest fossil evidence for Osedax borings was previously described in plesiosaur and sea turtle bones from the mid-Cretaceous of the United Kingdom, representing the only unequivocal pre-Oligocene occurrences. Confirming through CT scanning, we present new evidence of Osedax borings in three plesiosaur specimens and, for the first time, identify borings in two mosasaur specimens. All specimens are from the Late Cretaceous: one from the Cenomanian of the United Kingdom, two from the Campanian of the southeastern United States, and two from the Maastrichtian of Belgium. This extends the geographic range of Osedax in the Cretaceous to both sides of the northern Atlantic Ocean. The bones contain five borehole morphotypes, potentially created by different species of Osedax, with the Cenomanian specimen containing three morphotypes within a single tooth. This combined evidence of heightened species diversity by the Cenomanian and broad geographic range by the Campanian potentially indicates an earlier origin and diversification for this clade than previously hypothesized. Preservational biases indicate that Osedax was probably even more widely distributed and speciose in the Cretaceous than apparent in the fossil record.

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Abstract Introduction: The sea urchin Diadema mexicanum, due to its bioerosion activity, is considered of ecological importance. This phenomenon could negatively or positively affect coral reef ecosystems. The bioerosion process varies according to the abundance and size of the sea urchin. Objective: Juvenile organisms possess different metabolic needs compared to adults, so knowing their stomach content according to size allows us to quantify the selection of substrate bioeroded. Methods: To determine this, D. mexicanum individuals were collected in 12 sites from January 2009 to September 2010 along the Eastern Tropical Pacific coast. The stomach content was categorized in Carbonated Fraction (CF), Non-Carbonated Fraction (NCF), and Organic Matter (OM). Stomach content was analyzed according to a) juvenile (< 2.5 cm) or adult (> 2.5 cm) stage and b) locality. Results: Juveniles presented the following stomach content average percentages: 20.7 % OM, 12 % NCF and 67.9 % CF; and adults: 11.4 % OM, 14.8 % NCF and 73.8 % CF. Based on a Wilcoxon test and a Kendall linear regression, the following results were obtained. The carbonated fraction in the stomach increased by 0.47 units on average for every cm of growth (p < 0.05). OM consumed by D. mexicanum increases only 0.05 units for every cm of growth (p < 0.05). We found a difference of stomach content depending on the site (p < 0.05) and life stage (p < 0.05). Localities like Huatulco and Coco presented significant differences that could be related to local oceanographic conditions. Conclusions: We relate these changes of the stomach fractions to the necessity of the juvenile sea urchins for nutrients to maintain their growth. The amount of OM is crucial for the development of early stages, meaning that there is a difference in substrate selection associated with growth.

Resumen Introducción: El erizo de mar Diadema mexicanum, por su actividad de bioerosión, es considerado de importancia ecológica. Este fenómeno podría afectar negativa o positivamente a los ecosistemas de arrecifes de coral. El proceso de bioerosión varía según la abundancia y el tamaño del erizo de mar. Objetivo: Los organismos juveniles poseen diferentes necesidades metabólicas en comparación con los adultos, por lo que conocer el contenido estomacal según el tamaño, nos permite cuantificar la selección de sustrato bioerosionado. Métodos: Para determinar esto, se recolectaron individuos de D. mexicanum en 12 sitios desde enero de 2009 hasta septiembre de 2010 a lo largo de la costa del Pacífico Tropical Oriental. El contenido estomacal se clasificó en Fracción Carbonatada (FC), Fracción No Carbonatada (NCF) y Materia Orgánica (MO). El contenido estomacal se analizó según a) estadio juvenil (< 3 cm) o adulto (> 3 cm) y b) localidad. Resultados: Los juveniles presentaron los siguientes porcentajes promedio del contenido estomacal: 20.7 % OM, 12 % NCF y 67.9 % CF; y adultos: 11.4 % OM, 14.8 % NCF y 73.8 % CF. Con base en una prueba de Wilcoxon y una regresión lineal de Kendall, se obtuvieron los siguientes resultados. La fracción carbonatada en el estómago aumentó en promedio 0.47 unidades por cada cm de crecimiento (p < 0.05). La MO consumida por D. mexicanum aumenta solo 0.05 unidades por cada cm de crecimiento (p < 0.05). Encontramos una diferencia en el contenido estomacal según el sitio (p < 0.05) y el estadio de vida (P < 0.05). Localidades como Huatulco y Coco presentaron diferencias significativas que podrían estar relacionadas con las condiciones oceanográficas locales. Conclusiones: Relacionamos estos cambios de la composición porcentual del contenido estomacal con la necesidad de los erizos de mar juveniles de nutrientes para mantener su crecimiento. La cantidad de MO es crucial para el desarrollo de las primeras etapas, lo que significa que existe una diferencia en la selección de sustrato asociada con el crecimiento.

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Bioeroded carbonate clasts from a Pliocene shallow-marine succession of Almería (SE Spain, Betic Cordillera) were analysed with computed tomography (CT). This revealed the detailed 3D architecture of bioerosion structures hidden within and allowed for their ichnotaxonomic identification (14 ichnospecies of 5 ichnogenera) and quantification. Borings are produced by worms, mostly polychaetes and sipunculids dominated, followed by bivalves and lastly by sponges. The crosscutting relationship between the borings and their preservation characteristics points to a complex colonization history of the clasts with repeated bioerosive episodes interrupted by physical disturbances, including overturning and abrasion of the clasts followed by their recolonization. Our findings facilitated paleoenvironmental interpretation and can be compared to analogous modern-day ecological succession. The sharp dominance of worm borings - early successional species - may be related to frequent, periodic, physical disturbance that possibly prevented the cobble-dwelling macroboring community from being overtaken by sponges - late successional taxa. CT, hand sample and petrographic observations detected, aside from borings, other irregularly shaped pores which are interpreted to be generated by diagenetic processes including dolomitization, silicification and dissolution, representing an intraparticle moldic and moldic enlarged porosity. Boring porosity crosscutting the diagenetically altered grains suggests the later occurrence of bioerosion processes. Irregular shapes ranging from roughly spherical, elongate sub-polyhedral to amoeboid resemble morphologies produced by modern sponges. Moldic pores possibly acted as primary domiciles for boring sponges, which infested, altered and enlarged pre-existing pores as they grew (as happens in the modern), providing an example of how biological and non-biological processes interacted and together influenced endolithic palaeocommunity development.

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The identification of marine post-mortem microstructural change in human bone tissue is valuable in forensic casework as evidence of an individual's burial history. This study examined micro-tunneling in pig-bone tissue microstructure that had been submerged in a marine environment. The objective of the experiment was to assess total distribution of post-mortem microstructural change and degree of preservation within and between individual submerged pig skeletons. 14 juvenile pig carcasses were submerged in British Columbia at 92-300 m depths, between four to eight months. Seven pigs were individually submerged within caged platforms, seven were tied to open platforms. Six bones were selected from each carcass: first rib, radius, ulna, middle-rib, tibia, and femur. Two transverse thin sections were sampled at each bone mid-shaft (n = 148) and examined using circularly polarized transmitted light. The distribution of tunnels was assessed by measuring tunnel maximum ingress and diameter at 40 locations of the peripheral cortex. All element types were impacted by peripheral tunneling from the periosteum to the central cortex. Tunnels were observed as radiating, bifurcating with no remineralization boundary, isolated and in clusters. Tunnel diameters ranged between 2.00 µm and 12.8 µm, with a 3.7 µm mean. Ingress measurements ranged between 7.5 µm and 435.8 µm with a 93.0 µm mean. Distribution of post-mortem microstructural change across skeletal elements showed the averaged maximum ingress was deeper in the uncaged (99.6 µm), when compared to caged material (78.5 µm). The averaged tunnel ingress had statistically significant differences between uncaged and caged carcasses overall (p-value=0.02). Results of the study indicate microboring is present in marine submersed mammalian bone microstructure in as little as 134 days. This informs forensic investigators of the rate of skeletal destruction and of the narrow window for forensic recoveries, particularly in an enclosed environment. Furthermore, the presence of marine microboring in bone can assist forensic practitioners to histologically interpret the environmental history of a corpse.

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Ostreobium is a siphonous green alga in the Bryopsidales (Chlorophyta) that burrows into calcium carbonate (CaCO3) substrates. In this habitat, it lives under environmental conditions unusual for an alga (i.e., low light and low oxygen) and it is a major agent of carbonate reef bioerosion. In coral skeletons, Ostreobium can form conspicuous green bands recognizable by the naked eye and it is thought to contribute to the coral's nutritional needs. With coral reefs in global decline, there is a renewed focus on understanding Ostreobium biology and its roles in the coral holobiont. This review summarizes knowledge on Ostreobium's morphological structure, biodiversity and evolution, photosynthesis, mechanism of bioerosion and its role as a member of the coral holobiont. We discuss the resources available to study Ostreobium biology, lay out some of the uncharted territories in Ostreobium biology and offer perspectives for future research.

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Euendolithic, or true-boring, cyanobacteria actively erode carbonate-containing substrata in a wide range of environments and pose significant risks to calcareous marine fauna. Their boring activities cause structural damage and increase susceptibility to disease and are projected to only intensify with global climate change. Most research has, however, focused on tropical coral systems, and limited information exists on the global distribution, diversity, and substratum specificity of euendoliths. This metastudy aimed to collate existing 16S rRNA gene surveys along with novel data from the south coast of South Africa to investigate the global distribution and genetic diversity of endoliths to identify a "core endolithic cyanobacterial microbiome" and assess global diversification of euendolithic cyanobacteria. The cyanobacterial families Phormidesmiaceae, Nodosilineaceae, Nostocaceae, and Xenococcaceae were the most prevalent, found in >92% of categories surveyed. All four known euendolith clusters were detected in both intertidal and subtidal habitats, in the North Atlantic, Mediterranean, and South Pacific oceans, across temperate latitudes, and within rock, travertine tiles, coral, shell, and coralline algae substrata. Analysis of the genetic variation within clusters revealed many organisms to be unique to substratum type and location, suggesting high diversity and niche specificity. Euendoliths are known to have important effects on their hosts. This is particularly important when hosts are globally significant ecological engineers or habitat-forming species. The findings of this study indicate high ubiquity and diversity of euendolithic cyanobacteria, suggesting high adaptability, which may lead to increased community and ecosystem-level effects with changing climatic conditions favoring the biochemical mechanisms of cyanobacterial bioerosion.

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Ocean acidification (OA) is expected to modify the structure and function of coral reef ecosystems by reducing calcification, increasing bioerosion, and altering the physiology of many marine organisms. Much of our understanding of these relationships is based on experiments with static OA treatments, although evidence suggests that the magnitude of diurnal fluctuations in carbonate chemistry may modulate the calcification response to OA. These light-mediated swings in seawater pH are projected to become more extreme with OA, yet their impact on bioerosion remains unknown. We evaluated the influence of diurnal carbonate chemistry variability on the bioerosion rates of two Caribbean sponges: the zooxanthellate Cliona varians and azooxanthellate Cliothosa delitrix. Replicate fragments from multiple colonies of each species were exposed to four precisely controlled pH treatments: contemporary static (8.05 ± 0.00; mean pH ± diurnal pH oscillation), contemporary variable (8.05 ± 0.10), future OA static (7.80 ± 0.00), and future OA variable (7.80 ± 0.10). Significantly enhanced bioerosion rates, determined using buoyant weight measurements, were observed under more variable conditions in both the contemporary and future OA scenarios for C. varians, whereas the same effect was only apparent under contemporary pH conditions for C. delitrix. These results indicate that variable carbonate chemistry has a stimulating influence on sponge bioerosion, and we hypothesize that bioerosion rates evolve non-linearly as a function of pCO2 resulting in different magnitudes and directions of rate enhancement/reduction between day and night, even with an equal fluctuation around the mean. This response appeared to be intensified by photosymbionts, evident by the consistently higher percent increase in bioerosion rates for photosynthetic C. varians across all treatments. These findings further suggest that more variable natural ecosystems may presently experience elevated sponge bioerosion rates and that the heightened impact of OA enhanced bioerosion on reef habitat could occur sooner than prior predictions.

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Shellfish, mussels, snails, and other aquatic animals, which assimilate limestone (calcium carbonate, CaCO3) to build shells and skeletons, are effective carbon sinks that help mitigate the greenhouse effect. However, bioerosion, the dissolution of calcium carbonate and the release of carbon dioxide, hinders carbon sequestration process. The bioerosion of aquatic environments remains to be elucidated. In this study, the bioerosion of Bellamya spp. shells from the aquatic environment was taken as the research object. In situ microbial community structure analysis of the bioerosion shell from different geographical locations, laboratory-level infected culture, and validated experiments were conducted by coupling traditional observation and 16S rRNA sequencing analysis method. Results showed that bioeroders can implant into the CaCO3 layer of the snail shell, resulting in the formation of many small holes in the shell, which reduced the shell's density and made the shell fragile. Results also showed that bioeroders were distributed in two major phyla, namely, Cyanobacteria and Proteobacteria. Cluster analysis showed that Cyanobacteria sp. and two unidentified genera (Burkholderiaceae and Raistonia) were the key bioeroders. Moreover, results suggested that the interaction of Cyanobacteria and other bacteria promoted the biological function of "shell bioerosion." This study identified the causes of "shell bioerosion" in aquatic environments and provided some theoretical basis for preventing and controlling it in the aquatic industry. Results also provided new insights of cyanobacterial bioerosion of shells and microalgae carbon sequestration.

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Coral-reef degradation is driving global-scale reductions in reef-building capacity and the ecological, geological, and socioeconomic functions it supports. The persistence of those essential functions will depend on whether coral-reef management is able to rebalance the competing processes of reef accretion and erosion. Here, we reconstructed census-based carbonate budgets of 46 reefs throughout the Florida Keys from 1996 to 2019. We evaluated the environmental and ecological drivers of changing budget states and compared historical trends in reef-accretion potential to millennial-scale baselines of accretion from reef cores and future projections with coral restoration. We found that historically, most reefs had positive carbonate budgets, and many had reef-accretion potential comparable to the ~3 mm year-1 average accretion rate during the peak of regional reef building ~7000 years ago; however, declines in reef-building Acropora palmata and Orbicella spp. corals following a series of thermal stress events and coral disease outbreaks resulted in a shift from positive to negative budgets for most reefs in the region. By 2019, only ~15% of reefs had positive net carbonate production. Most of those reefs were in inshore, Lower Keys patch-reef habitats with low water clarity, supporting the hypothesis that environments with naturally low irradiance may provide a refugia from thermal stress. We caution that our estimated carbonate budgets are likely overly optimistic; comparison of reef-accretion potential to measured accretion from reef cores suggests that, by not accounting for the role of nonbiological physical and chemical erosion, census-based carbonate budgets may underestimate total erosion by ~1 mm year-1 (-1.15 kg CaCO3 m-2 year-1 ). Although the present state of Florida's reefs is dire, we demonstrate that the restoration of reef-building corals has the potential to help mitigate declines in reef accretion in some locations, which could allow some key ecosystem functions to be maintained until the threat of global climate change is addressed.

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Postcranial elements (cervical, sacral and caudal vertebrae, as well as ilium, rib and limb bone fragments) belonging to a gigantic tetanuran theropod were recovered from the basal unit (the White Rock Sandstone equivalent) of the Vectis Formation near Compton Chine, on the southwest coast of the Isle of Wight. These remains appear to pertain to the same individual, with enormous dimensions similar to those of the Spinosaurus holotype and exceeding those of the largest European theropods previously reported. A combination of features-including the presence of spinodiapophyseal webbing on an anterior caudal vertebra-suggest that this is a member of Spinosauridae, though a lack of convincing autapomorphies precludes the identification of a new taxon. Phylogenetic analysis supports spinosaurid affinities but we were unable to determine a more precise position within the clade weak support for a position within Spinosaurinae or an early-diverging position within Spinosauridae were found in some data runs. Bioerosion in the form of curved tubes is evident on several pieces, potentially related to harvesting behaviour by coleopteran bioeroders. This is the first spinosaurid reported from the Vectis Formation and the youngest British material referred to the clade. This Vectis Formation spinosaurid is unusual in that the majority of dinosaurs from the Lower Cretaceous units of the Wealden Supergroup are from the fluviolacustrine deposits of the underlying Barremian Wessex Formation. In contrast, the lagoonal facies of the upper Barremian-lower Aptian Vectis Formation only rarely yield dinosaur material. Our conclusions are in keeping with previous studies that emphasise western Europe as a pivotal region within spinosaurid origination and diversification.

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Stone buildings exposed to natural environment inevitably subject to various factors. Among which, biodeterioration caused by bacteria, fungi, algae, lichen, and moss is widespread. The long-term cumulative effect of biodeterioration will lead to irreversible changes in the aesthetic characteristics, physical and chemical properties of stone buildings. Therefore, it is necessary to control the biodeterioration of stone buildings. Here, we summarized four traditional methods including heat shock treatments, laser and ultraviolet radiation, application of biocides, and presented typical examples. We analyzed several emerging techniques, such as synergistic effect of physical and chemical methods, plant extracts and nanomaterials biocides, and reviewed their advantages, disadvantages as well as applicability. Aiming to provide a reference for the research of biodeterioration prevention and conservation of stone buildings, we discussed the preventive methods for biodeterioration of stone building and the assessment methods to test the effects of such methods, and prospected the future research direction.

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Ichnofossils, the fossilized products of life-substrate interactions, are among the most abundant biosignatures on Earth and therefore they may provide scientific evidence of potential life that may have existed on Mars. Ichnofossils offer unique advantages in the search for extraterrestrial life, including the fact that they are resilient to processes that obliterate other evidence for past life, such as body fossils, as well as chemical and isotopic biosignatures. The goal of this paper is evaluating the suitability of the Mars 2020 Landing Site for ichnofossils. To this goal, we apply palaeontological predictive modelling, a technique used to forecast the location of fossil sites in uninvestigated areas on Earth. Accordingly, a geographic information system (GIS) of the landing site is developed. Each layer of the GIS maps the suitability for one or more ichnofossil types (bioturbation, bioerosion, biostratification structures) based on an assessment of a single attribute (suitability factor) of the Martian environment. Suitability criteria have been selected among the environmental attributes that control ichnofossil abundance and preservation in 18 reference sites on Earth. The goal of this research is delivered through three predictive maps showing which areas of the Mars 2020 Landing Site are more likely to preserve potential ichnofossils. On the basis of these maps, an ichnological strategy for the Perseverance rover is identified, indicating (1) 10 sites on Mars with high suitability for bioturbation, bioerosion and biostratification ichnofossils, (2) the ichnofossil types, if any, that are more likely to be present at each site, (3) the most efficient observation strategy for detecting eventual ichnofossils. The predictive maps and the ichnological strategy can be easily integrated in the existing plans for the exploration of the Jezero crater, realizing benefits in life-search efficiency and cost-reduction.

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The evaluation of bone diagenetic phenomena in archaeological timescales has a long history; however, little is known about the origins of the microbes driving bone diagenesis, nor about the extent of bone diagenesis in short timeframes-such as in forensic contexts. Previously, the analysis of non-collagenous proteins (NCPs) through bottom-up proteomics revealed the presence of potential biomarkers useful in estimating the post-mortem interval (PMI). However, there is still a great need for enhancing the understanding of the diagenetic processes taking place in forensic timeframes, and to clarify whether proteomic analyses can help to develop better models for estimating PMI reliably. To address these knowledge gaps, we designed an experiment based on whole rat carcasses, defleshed long rat bones, and excised but still-fleshed rat limbs, which were either buried in soil or exposed on a clean plastic surface, left to decompose for 28 weeks, and retrieved at different time intervals. This study aimed to assess differences in bone protein relative abundances for the various deposition modalities and intervals. We further evaluated the effects that extrinsic factors, autolysis, and gut and soil bacteria had on bone diagenesis via bottom-up proteomics. Results showed six proteins whose abundance was significantly different between samples subjected to either microbial decomposition (gut or soil bacteria) or to environmental factors. In particular, muscle- and calcium-binding proteins were found to be more prone to degradation by bacterial attack, whereas plasma and bone marrow proteins were more susceptible to exposure to extrinsic agents. Our results suggest that both gut and soil bacteria play key roles in bone diagenesis and protein decay in relatively short timescales, and that bone proteomics is a proficient resource with which to identify microbially-driven versus extrinsically-driven diagenesis.

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Erosion of coral substrate plays a crucial role in reef calcium carbonate budget, but little is known about erosion in subtropical corals. In a 2-year study of coral substrate erosion, we deployed Porites skeletal blocks at nine sites across subtropical Hong Kong waters. External erosion varied from 0.05 to 3.07 kg m-2 yr-1 and accounted for 23.4-99.2% of the total erosion. More than half of the study sites had substantial external erosion (> 1 kg m-2 yr-1), and the values were positively correlated with density of the sea urchin Diadema setosum. Excluding urchins from access to the skeletal blocks using cages reduced external erosion by more than 90%. Overall, our study revealed that external erosion caused by urchin grazing contributed predominantly to the total coral skeletal loss in Hong Kong waters. Control of sea urchin population is needed to reduce coral erosion in places with high urchin density. (149 words).

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Introduction: The taphonomic attributes of a faunal assemblage provide information about which agents affect the distribution and preservation of ancient or newly formed biogenic materials during depositional and post-depositional processes. Actuotaphonomy thus is a valuable tool for reconstructing fossil communities because it establishes analogies between observable processes in the present and those that happened in the past. Objective: The taphonomic attributes of a marginal marine environment were analyzed to assess the origin of fragmentation, bioerosion, and encrustation processes and the role of these characteristics in the deterioration of current sediment accumulations of mollusks (gastropods and bivalves). Methods: The material studied was collected from a shell-remain accumulation called "El Conchal" in the Laguna de Mandinga, Veracruz, a lagoonal complex located in the Gulf of México. Taphonomic analysis included fragmentation, bioerosion, and encrustation features on recent gastropods and bivalve's shells. The categories of each attribute were classified in three degrees: poor, regular and good. The analysis was performed only in complete shells. Results: A bulk sample of 1 697.9 g was processed, recovering 1 165 complete specimens, of which 5 genera of bivalves and 4 genera of gastropods were identified. The fragmentation and bioerosion were classified as regular (grade 1), this may be the results of the water energy in the environment, that permits a constant rework, and exhumation of the remains at the lagoon's water-sediment interface; meanwhile, three eroders were identified to ichnogenus level: Entobia, Oichnus, and Caulostrepsis, being Caulostrepsis the least abundant. The encrustation was classified as poor (grade 2); the result can be interpreted based on the ecosystem intrinsic conditions that do not allow many encrusting organisms to develop properly. The encrusters are represented by calcareous organisms including bryozoans, serpulids tubes, and barnacles. The results yielded an actuotaphonomic model that could be applicable to analogous ecosystems in Laguna de Mandinga (Mandinga Lagoon), in Veracruz, Mexico. Conclusions: In marine marginal environments as in lagoon areas the encrustation does not have an important role in the preservation or destruction of shelly assemblages, being taphonomically more important than fragmentation and bioerosion as potentially destructive agents that can be a source of loss of fidelity in the fossil record.

Introducción: Los atributos tafonómicos de los conchales proveen información acerca de cuáles agentes afectan la distribución y preservación de la acumulación de materiales biogénicos recientes o fósiles, especialmente durante las etapas deposiconales y postdeposicionales. La actuotafonomía es una herramienta valiosa para la reconstrucción de las comunidades fósiles, para establecer analogías entre los procesos observables en el presente con los que ocurrieron en el pasado. Objetivos: Evaluar el impacto de los rasgos tafonómicos y su papel en la formación de los conchales en ambientes de lagunas costeras. Métodos: El material estudiado fue recolectado en una acumulación de restos de conchas llamado "El Conchal" en la Laguna de Mandinga, Veracruz, un complejo lagunar ubicado en el Golfo de México. El análisis tafonómico incluye las características tafonómicas de fragmentación, bioerosión e incrustación en conchas de gasterópodos y bivalvos recientes. Las categorías de cada atributo se clasificaron en tres grados: pobre, medio y alto. El análisis fue realizado solo en conchas completas. Resultados: Se procesaron 1 697.9 g de sedimentos, recuperando 1 165 ejemplares completos, de los cuales se identificaron 5 géneros de bivalvos y 4 géneros de gasterópodos. La fragmentación y bioerosión se clasificaron como un "grado regular", esto puede ser el resultado de la energía del agua en el ambiente, que permite el constante retrabajo y la exhumación de los restos en la interfase agua-sedimento en la laguna; en tanto que, se identificaron tres erosionadores a nivel de género, estos corresponden a los icnogéneros: Entobia, Oichnus y Caulostrepsis, siendo Caulostrepsis el menos abundante. La incrustación mostró un "grado pobre"; el resultado puede interpretarse basado en las condiciones intrínsecas del ecosistema que no permiten que muchos incrustantes se desarrollen de la manera adecuada. Los incrustantes están representados por organismos calcáreos incluyendo briozoarios, tubos de serpúlidos y balanos. Se analizaron los atributos tafonómicos para generar un modelo actuotafonómico que pueda ser aplicable a ecosistemas análogos en el registro fósil. Conclusiones: En ambientes marino marginales como son las áreas lagunares la incrustación no tiene un papel importante en la preservación o destrucción de los conchales, siendo tafonómicamente más importante la fragmentación y bioerosión como agentes potencialmente destructivos que pueden ser un recurso de pérdida de la fidelidad en el registro fósil.

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RESUMEN

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.

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