Systematic review and meta-analysis of ocean acidification effects in Halimeda: Implications for algal carbonate production

Ocean acidification (OA) has been identified as one of the major climate-change related threats, mainly due to its significant impacts on marine calcifiers. Among those are the calcareous green algae of the genus Halimeda that are known to be major carbonate producers in shallow tropical and subtropical seas. Hence, any negative OA impacts on these organisms may translate into significant declines in regional and global carbonate production. In this study, we compiled the available information regarding Halimeda spp. responses to OA (experimental, in situ), with special focus on the calcification responses, one of the most studied response parameters in this group. Furthermore, among the compiled studies (n = 31), we selected those reporting quantitative data of OA effects on algal net calcification in an attempt to identify potential general patterns of species- and/or regional-specific OA responses and hence, impacts on carbonate production. While obtaining general patterns was largely hampered by the often scarce number of studies on individual species and/or regions, the currently available information indicates species-specific susceptibility to OA, seemingly unrelated to evolutionary lineages (and associated differences in morphology), that is often accompanied by differences in a species� response across different regions. Thus, for projections of future declines in Halimeda-associated carbonate production, we used available regional reports of species-specific carbonate production in conjunction with experimental OA responses for the respective species and regions. Based on the available information, declines can be expected worldwide, though some regions harbouring more sensitive species might be more impacted than others

Simplification of Caribbean Reef-Fish Assemblages over Decades of Coral Reef Degradation

Caribbean coral reefs are becoming structurally simpler, largely due to human impacts. The consequences of this trend for reef-associated communities are currently unclear, but expected to be profound. Here, we assess whether changes in fish assemblages have been non-random over several decades of declining reef structure. More specifically, we predicted that species that depend exclusively on coral reef habitat (i.e., habitat specialists) should be at a disadvantage compared to those that use a broader array of habitats (i.e., habitat generalists). Analysing 3727 abundance trends of 161 Caribbean reef-fishes, surveyed between 1980 and 2006, we found that the trends of habitat-generalists and habitat-specialists differed markedly. The abundance of specialists started to decline in the mid-1980s, reaching a low of ~60% of the 1980 baseline by the mid-1990s. Both the average and the variation in abundance of specialists have increased since the early 2000s, although the average is still well below the baseline level of 1980. This modest recovery occurred despite no clear evidence of a regional recovery in coral reef habitat quality in the Caribbean during the 2000s. In contrast, the abundance of generalist fishes remained relatively stable over the same three decades. Few specialist species are fished, thus their population declines are most likely linked to habitat degradation. These results mirror the observed trends of replacement of specialists by generalists, observed in terrestrial taxa across the globe. A significant challenge that arises from our findings is now to investigate if, and how, such community-level changes in fish populations affect ecosystem function

Differences in the progression rate of SCTLD in Pseudodiploria strigosa are related to colony size and morphology

Stony Coral Tissue Loss Disease (SCTLD) impacts are unprecedented concerning the level of devastation they have imposed on Caribbean coral assemblages. Although SCTLD affects nearly 30 different coral species, it has been particularly lethal for Pseudodiploria strigosa. Mortality rates for this species are estimated to be between 60 and 100% in the Caribbean; however, tissue-loss rates have been shown to differ among colonies, which suggests that colony health, environmental conditions, and concurrent transmission events are crucial to the development of the disease at reef scale. To gain insight into the colony-level dynamics of SCTLD, we used a simplified photogrammetry and 3D modeling approach to quantify and compare SCTLD-related tissue-loss rates among 20 colonies of P. strigosa on a shallow back-reef in the Mexican Caribbean. Over a six-month period, SCTLD resulted in the full mortality of 70% of the colonies that were tagged shortly after infection. Although disease progression followed a multifocal-type infection in most cases, tissue-loss rates significantly differed among colonies. Some colonies died within the first 20 days of observation, while others died towards the end of the study period. We found a significant positive effect of colony size on rates of tissue loss disease, as well as evidence suggesting that elongated and vertically compressed colonies have a greater probability of experiencing higher tissue-loss rates than colonies with more spherical shapes. The observed relationship between colony morphology and tissue-loss rates is likely a result of elongated colonies having more flat surface area at the top of the colonies which facilitates accumulation of sediments, which have been shown to be a source of SCTLD transmission

Macrobioerosión de corales constructores de arrecifes y su impacto en la dinámica de carbonatos en los arrecifes de Huatulco, México

Background. Coral reefs exist thanks to the delicate balance between calcification and erosion processes. However, due to anthropogenic pressures, bioerosive processes have become the main forcing factors in reef growth patterns. Nevertheless, due to the morphology of the reefs located in the Mexican South Pacific (extensive plates of pociloporids), estimating internal macrobioerosion is a challenge, resulting in a critical gap in bioerosion processes, particularly those occurring inside corals. Objectives. To measure the internal macrobioerosion of the main coral species and to know its impact on carbonate production in reefs. Methods. We used a computed tomography (CT) based approach to measure the volume of CaCO3 removed by different groups of macrobioeroders. Results. We estimated percentages of internal macrobioerosion between 16.80 % and 26.67 % of the total volume of the colonies. We observed that sponges and mollusks are the guilds that most bioerode species of branching and massive morphology, respectively. We found macrobioerosion rates of 1.51 ± 0.11 kg CaCO3 m-2 yr-1 for branched species and 0.53 ± 0.03 kg CaCO3 m-2 yr-1 for massive species. The measured bioerosion processes accounted for 39.02 % and 43.86 % of CaCO3 production. Conclusions. Although CT scanning represents higher costs than other approaches (i.e., X-rays), it is the only approach capable of measuring the internal macrobioerosion that occurs within the entire coral skeleton. This approach will allow us to produce more accurate carbonate balances than those that do not consider internal macrobioerosion, improving our estimates of the state of health of the reefs.Antecedentes. Los arrecifes de coral subsisten gracias al delicado balance entre procesos de acreción y de erosión. No obstante, debido a presiones antropogénicas, los procesos bioerosivos se han convertido en los principales factores que condicionan los patrones de crecimiento de los arrecifes. Debido a la morfología de los arrecifes ubicados en el Pacífico sur mexicano (placas extensas de pocilopóridos), estimar la macrobioerosión interna se convierte en un reto, lo que resulta en una importante brecha sobre los procesos de bioerosión, particularmente los que ocurren al interior de los corales. Objetivo. Medir la macrobioerosión interna de las principales especies de coral y conocer el impacto que ejerce sobre la producción de carbonatos en los arrecifes. Métodos. Empleamos un enfoque basado en tomografía computarizada (TC) que permite medir el volumen de CaCO3 removido por diferentes grupos de macrobioerosionadores. Resultados. Estimamos porcentajes de macrobioerosión interna entre el 16.80 % y el 26.67 % del volumen total de las colonias de coral. Observamos que las esponjas y moluscos son los grupos que más bioerosionan las especies de coral con morfología ramificada y masiva, respectivamente. Encontramos tasas de macrobioerosión de 1.51 ± 0.11 kg CaCO3 m-2 año-1 para las especies ramificadas y de 0.53 ± 0.03 de kg CaCO3 m-2año-1 para las especies masivas. Los procesos de bioerosión representaron entre el 39.02 % y 43.86 % de la producción de CaCO3, que fue calculada mediante la metodología ReefBudget. Conclusiones. A pesar que emplear TC representa costos más elevados que otros enfoques (p. ej., rayos-X), hasta ahora es el único enfoque capaz de medir la macrobioerosión interna de todo el esqueleto de coral. Este enfoque permitirá producir balances de carbonatos más certeros que aquellos que no consideran la macrobioerosión interna, mejorando nuestras estimaciones del estado de salud en que se encuentran los arrecifes

Half of Atlantic reef-building corals at elevated risk of extinction due to climate change and other threats

Atlantic reef-building corals and coral reefs continue to experience extensive decline due to increased stressors related to climate change, disease, pollution, and numerous anthropogenic threats. To understand the impact of ocean warming and reef loss on the estimated extinction risk of shallow water Atlantic reef-building scleractinians and milleporids, all 85 valid species were reassessed under the IUCN Red List Categories and Criteria, updating the previous Red List assessment of Atlantic corals published in 2008. For the present assessment, individual species declines were estimated based on the modeled coral cover loss (1989–2019) and projected onset of annual severe bleaching events (2020–2050) across the Atlantic. Species traits were used to scale species’ relative vulnerability to the modeled cover declines and forecasted bleaching events. The updated assessments place 45.88%–54.12% of Atlantic shallow water corals at an elevated extinction risk compared to the previous assessments conducted in 2008 (15.19%–40.51%). However, coral cover loss estimates indicate an improvement in reef coverage compared to the historic time-series used for the 2008 assessments. Based on this, we infer that, although remaining dangerously high, the rate of Atlantic reef coral cover decline has surprisingly slowed in recent decades. However, based on modeled projections of sea-surface temperature that predict the onset of annual severe bleaching events within the next 30 years, we listed 26 (out of 85) species as Critically Endangered in the IUCN Red List. Each of these species had previously been listed under a lower threatened category and this result alone highlights the severe threat future bleaching events pose to coral survival and the reef ecosystems they support

Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005

BACKGROUND The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. METHODOLOGY/PRINCIPAL FINDINGS Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. CONCLUSIONS/SIGNIFICANCE Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.This work was partially supported by salaries from the NOAA Coral Reef Conservation Program to the NOAA Coral Reef Conservation Program authors. NOAA provided funding to Caribbean ReefCheck investigators to undertake surveys of bleaching and mortality. Otherwise, no funding from outside authors' institutions was necessary for the undertaking of this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio