Function and stability of mesophotic coral reefs.

The function and stability of mesophotic coral ecosystems (MCEs) have been extensively studied in recent years. These deep reefs are characterized by local physical processes, particularly the steep gradient in irradiance with increasing depth, and their impact on trophic resources. Mesophotic reefs exhibit distinct zonation patterns that segregate shallow reef biodiversity from ecologically unique deeper communities of endemic species. While mesophotic reefs are hypothesized as relatively stable refuges from anthropogenic stressors and a potential seed bank for degraded shallow reefs, these are site-specific features, if they occur at all. Mesophotic reefs are now known to be susceptible to many of the same stressors that are degrading shallow reefs, suggesting that they require their own specific conservation and management strategies.

Gambierdiscus species diversity and community structure in St. Thomas, USVI and the Florida Keys, USA.

Ciguatera Poisoning (CP) is a widespread and complex poisoning syndrome caused by the consumption of fish or invertebrates contaminated with a suite of potent neurotoxins collectively known as ciguatoxins (CTXs), which are produced by certain benthic dinoflagellates species in the genera Gambierdiscus and Fukuyoa. Due to the complex nature of this HAB problem, along with a poor understanding of toxin production and entry in the coral reef food web, the development of monitoring, management, and forecasting approaches for CP has lagged behind those available for other HAB syndromes. Over the past two decades, renewed research on the taxonomy, physiology, and toxicology of CP-causing dinoflagellates has advanced our understanding of the species diversity that exists within these genera, including identification of highly toxic species (so called "superbugs") that likely contribute disproportionately to ciguatoxins entering coral reef food webs. The recent development of approaches for molecular analysis of field samples now provide the means to investigate in situ community composition, enabling characterization of spatio-temporal species dynamics, linkages between toxic species abundance and toxin flux, and the risk of ciguatoxin prevalence in fish. In this study we used species-specific fluorescent in situ hybridization (FISH) probes to investigate Gambierdiscus species composition and dynamics in St. Thomas (USVI) and the Florida Keys (USA) over multiple years (2018-2020). Within each location, samples were collected seasonally from several sites comprising varying depths, habitats, and algal substrates to characterize community structure over small spatial scales and across different host macrophytes. This approach enabled the quantitative determination of communities over spatiotemporal gradients, as well as the selective enumeration of species known to exhibit high toxicity, such as Gambierdiscus silvae. The investigation found differing community structure between St. Thomas and Florida Keys sites, driven in part by differences in the distribution of toxin-producing species G. silvae and G. belizeanus, which were present throughout sampling sites in St. Thomas but scarce or absent in the Florida Keys. This finding is significant given the high toxicity of G. silvae, and may help explain differences in fish toxicity and CP incidence between St. Thomas and Florida. Intrasite comparisons along a depth gradient found higher concentrations of Gambierdiscus spp. at deeper locations. Among the macrophytes sampled, Dictyota may be a likely vector for toxin transfer based on their widespread distribution, apparent colonization by G. silvae, and palatability to at least some herbivore grazers. Given its ubiquity throughout both study regions and sites, this taxa may also serve as a refuge, accumulating high concentrations of Gambierdiscus and other benthic dinoflagellates, which in turn can serve as source populations for highly palatable and ephemeral habitats nearby, such as turf algae. These studies further demonstrate the successful application of FISH probes in examining biogeographic structuring of Gambierdiscus communities, targeting individual toxin-producing species, and characterizing species-level dynamics that are needed to describe and model ecological drivers of species abundance and toxicity.

CiguaMOD I: A conceptual model of ciguatoxin loading in the Greater Caribbean Region.

Ciguatera poisoning (CP) is the most common form of phycotoxin-borne seafood poisoning globally, affecting thousands of people on an annual basis. It most commonly occurs in residential fish of coral reefs, which consume toxin-laden algae, detritus, and reef animals. The class of toxins that cause CP, ciguatoxins (CTXs), originate in benthic, epiphytic dinoflagellates of the genera, Gambierdiscus and Fukuyoa, which are consumed by herbivores and detritivores that facilitate food web transfer. A number of factors have hindered adequate environmental monitoring and seafood surveillance for ciguatera including the low concentrations in which the toxins are found in seafood causing illness (sub-ppb), a lack of knowledge on the toxicity equivalence of other CTXs and contribution of other benthic algal toxins to the disease, and the limited availability of quantified toxin standards and reference materials. While progress has been made on the identification of the dinoflagellate taxa and toxins responsible for CP, more effort is needed to better understand the dynamics of toxin transfer into reef food webs in order to implement a practical monitoring program for CP. Here, we present a conceptual model that utilizes empirical field data (temperature, Gambierdiscus cell densities, macrophyte cover) in concert with other published studies (grazing rates and preference) to produce modeling outputs that suggest approaches that may be beneficial to developing monitoring programs: 1) targeting specific macrophytes for Gambierdiscus and toxin measurements to monitor toxin levels at the base of the food web (i.e., toxin loading); and 2) adjusting these targets across sites and over seasons. Coupling this approach with other methodologies being incorporated into monitoring programs (artificial substrates; FISH probes; toxin screening) may provide an "early warning" system to develop strategic responses to potential CP flare ups in the future.

Ex vivo comparison of V.A.C.® Granufoam Silver™ and V.A.C.® Granufoam™ loaded with a first-in-class bis-dialkylnorspermidine-terphenyl antibiofilm agent.

Implementation of negative pressure wound therapy (NPWT) as a standard of care has proven efficacious in reducing both the healing time and likelihood of nosocomial infection among pressure ulcers and traumatic, combat-related injuries. However, current formulations may not target or dramatically reduce bacterial biofilm burden following therapy. The purpose of this study was to determine the antibiofilm efficacy of an open-cell polyurethane (PU) foam (V.A.C.® Granufoam™) loaded with a first-in-class compound (CZ-01179) as the active release agent integrated via lyophilized hydrogel scaffolding. An ex vivo porcine excision wound model was designed to perform antibiofilm efficacy testing in the presence of NPWT. PU foam samples loaded with a 10.0% w/w formulation of CZ-01179 and 0.5% hyaluronic acid were prepared and tested against current standards of care: V.A.C.® Granufoam Silver™ and V.A.C.® Granufoam™. We observed statistically significant reduction of methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii biofilms with the CZ-01179 antibiofilm foam in comparison to current standard of care foams. These findings motivate further development of an antibiofilm PU foam loaded with CZ-01179.

Marine debris provide long-distance pathways for spreading invasive corals.

Anthropogenic marine debris and invasive species are pervasive in the ocean. However, research on the mechanisms and dynamics controlling their distribution in marine systems (e.g.; by floating debris acting as vectors for invasive species) is limited. Applying a numerical modeling approach, we demonstrate that rafting invasive corals (Tubastraea spp.) can be transported over long distances and reach important tropical receptor regions. In <180 days, buoyant debris can cover distances between 264 and 7170 km moving from the Brazilian semiarid coast to the Amazon coast and reaching eight regions in the Wider Caribbean (mainly the Eastern Caribbean and Greater Antilles). Analyzing 48 simulated scenarios (4 years × 3 depths × 4 months), we demonstrate that in ~86 % of the scenarios the particles are stranded in the Caribbean and in ~71 % they end up in the Amazon coast. Our results showed litter floating trajectories at 0-10 m water depth, transported every year to the Caribbean province. However, in August this transport is frequently blocked by the retroflection of the North Brazil Current adjacent to the Amazon River estuarine plume. Our results indicate routes for fast and long-distance transport of litter-rafting invasive species. We hypothesized a high risk of bioinvasion on important marine ecosystems (e.g., coral reefs) likely becoming increasingly threatened by these invasive species and debris. This highlights the imperative need for an ocean governance shift in prevention, control, and eradication, not only focused on local actions to prevent the spread of invasive species but also a broad international action to decrease and mitigate marine debris pollution globally.

Stony coral tissue loss disease induces transcriptional signatures of in situ degradation of dysfunctional Symbiodiniaceae.

Stony coral tissue loss disease (SCTLD), one of the most pervasive and virulent coral diseases on record, affects over 22 species of reef-building coral and is decimating reefs throughout the Caribbean. To understand how different coral species and their algal symbionts (family Symbiodiniaceae) respond to this disease, we examine the gene expression profiles of colonies of five species of coral from a SCTLD transmission experiment. The included species vary in their purported susceptibilities to SCTLD, and we use this to inform gene expression analyses of both the coral animal and their Symbiodiniaceae. We identify orthologous coral genes exhibiting lineage-specific differences in expression that correlate to disease susceptibility, as well as genes that are differentially expressed in all coral species in response to SCTLD infection. We find that SCTLD infection induces increased expression of rab7, an established marker of in situ degradation of dysfunctional Symbiodiniaceae, in all coral species accompanied by genus-level shifts in Symbiodiniaceae photosystem and metabolism gene expression. Overall, our results indicate that SCTLD infection induces symbiophagy across coral species and that the severity of disease is influenced by Symbiodiniaceae identity.

A persistent green macroalgal mat shifts ecological functioning and composition of associated species on an Eastern Tropical Pacific coral reef.

Global evidence of phase shifts to alternate community types is of particular concern because these new communities can provide fundamentally different and often novel ecosystem functions and services compared to the original community. Shifts of a diverse range of marine communities to dominance by green macroalgal mats have occurred worldwide, making it critical to understand their emerging functions and roles. We observed a green algal mat on two reefs in the Eastern Tropical Pacific, with one persisting for >10 years on a reef with stable herbivore populations and no known sources of anthropogenic nutrients. These mats supported a more speciose macroalgal community with fewer taxa present in the adjacent coral community and facilitated growth of an associated understory macroalgal species by reducing herbivory pressure and possibly enhancing nutrient supplies within the mat community state. These results demonstrate a weakening in the processes controlling reef community structure as a result of the shift in composition associated with the macroalgal mat, creating a positive feedback supporting mat persistence. These novel ecosystem functions generated by this alternate community state illustrate the importance of further research on community shifts, which will become increasingly common in the Anthropocene.

Increased dominance of heat-tolerant symbionts creates resilient coral reefs in near-term ocean warming.

Climate change is radically altering coral reef ecosystems, mainly through increasingly frequent and severe bleaching events. Yet, some reefs have exhibited higher thermal tolerance after bleaching severely the first time. To understand changes in thermal tolerance in the eastern tropical Pacific (ETP), we compiled four decades of temperature, coral cover, coral bleaching, and mortality data, including three mass bleaching events during the 1982 to 1983, 1997 to 1998 and 2015 to 2016 El Niño heatwaves. Higher heat resistance in later bleaching events was detected in the dominant framework-building genus, Pocillopora, while other coral taxa exhibited similar susceptibility across events. Genetic analyses of Pocillopora spp. colonies and their algal symbionts (2014 to 2016) revealed that one of two Pocillopora lineages present in the region (Pocillopora "type 1") increased its association with thermotolerant algal symbionts (Durusdinium glynnii) during the 2015 to 2016 heat stress event. This lineage experienced lower bleaching and mortality compared with Pocillopora "type 3", which did not acquire D. glynnii. Under projected thermal stress, ETP reefs may be able to preserve high coral cover through the 2060s or later, mainly composed of Pocillopora colonies that associate with D. glynnii. However, although the low-diversity, high-cover reefs of the ETP could illustrate a potential functional state for some future reefs, this state may only be temporary unless global greenhouse gas emissions and resultant global warming are curtailed.

Isolation by distance in populations with power-law dispersal.

Limited dispersal of individuals between generations results in isolation by distance, in which individuals further apart in space tend to be less related. Classic models of isolation by distance assume that dispersal distances are drawn from a thin-tailed distribution and predict that the proportion of the genome that is identical by descent between a pair of individuals should decrease exponentially with the spatial separation between them. However, in many natural populations, individuals occasionally disperse over very long distances. In this work, we use mathematical analysis and coalescent simulations to study the effect of long-range (power-law) dispersal on patterns of isolation by distance. We find that it leads to power-law decay of identity-by-descent at large distances with the same exponent as dispersal. We also find that broad power-law dispersal produces another, shallow power-law decay of identity-by-descent at short distances. These results suggest that the distribution of long-range dispersal events could be estimated from sequencing large population samples taken from a wide range of spatial scales.

Interconnected marine habitats form a single continental-scale reef system in South America.

Large gaps in reef distribution may hinder the dispersal of marine organisms, interrupting processes vital to the maintenance of biodiversity. Here we show the presence and location of extensive reef habitats on the continental shelf between the Amazon Reef System (ARS) and the Eastern Brazilian Reef System (ERS), two reef complexes off eastern South America. Formations located 20-50 m deep include both biogenic and geogenic structures. The presence of diverse reef assemblages suggests the widespread occurrence of rocky substrates below 50 m. These habitats represent an expansion of both the ARS and ERS and the closure of the only remaining large-scale gap (~ 1000 km) among West Atlantic reef environments. This indicates that the SW Atlantic harbors a single, yet heterogeneous, reef system that stretches for about 4000 km, and thus, represents one of the largest semi-continuous tropical marine ecosystems in the world.

Experimental transmission of Stony Coral Tissue Loss Disease results in differential microbial responses within coral mucus and tissue.

Stony coral tissue loss disease (SCTLD) is a widespread and deadly disease that affects nearly half of Caribbean coral species. To understand the microbial community response to this disease, we performed a disease transmission experiment on US Virgin Island (USVI) corals, exposing six species of coral with varying susceptibility to SCTLD. The microbial community of the surface mucus and tissue layers were examined separately using a small subunit ribosomal RNA gene-based sequencing approach, and data were analyzed to identify microbial community shifts following disease acquisition, potential causative pathogens, as well as compare microbiota composition to field-based corals from the USVI and Florida outbreaks. While all species displayed similar microbiome composition with disease acquisition, microbiome similarity patterns differed by both species and mucus or tissue microhabitat. Further, disease exposed but not lesioned corals harbored a mucus microbial community similar to those showing disease signs, suggesting that mucus may serve as an early warning detection for the onset of SCTLD. Like other SCTLD studies in Florida, Rhodobacteraceae, Arcobacteraceae, Desulfovibrionaceae, Peptostreptococcaceae, Fusibacter, Marinifilaceae, and Vibrionaceae dominated diseased corals. This study demonstrates the differential response of the mucus and tissue microorganisms to SCTLD and suggests that mucus microorganisms may be diagnostic for early disease exposure.

Asynchrony of Gambierdiscus spp. Abundance and Toxicity in the U.S. Virgin Islands: Implications for Monitoring and Management of Ciguatera.

Ciguatera poisoning (CP) poses a significant threat to ecosystem services and fishery resources in coastal communities. The CP-causative ciguatoxins (CTXs) are produced by benthic dinoflagellates including Gambierdiscus and Fukuyoa spp., and enter reef food webs via grazing on macroalgal substrates. In this study, we report on a 3-year monthly time series in St. Thomas, US Virgin Islands where Gambierdiscus spp. abundance and Caribbean-CTX toxicity in benthic samples were compared to key environmental factors, including temperature, salinity, nutrients, benthic cover, and physical data. We found that peak Gambierdiscus abundance occurred in summer while CTX-specific toxicity peaked in cooler months (February-May) when the mean water temperatures were approximately 26-28 °C. These trends were most evident at deeper offshore sites where macroalgal cover was highest year-round. Other environmental parameters were not correlated with the CTX variability observed over time. The asynchrony between Gambierdiscus spp. abundance and toxicity reflects potential differences in toxin cell quotas among Gambierdiscus species with concomitant variability in their abundances throughout the year. These results have significant implications for monitoring and management of benthic harmful algal blooms and highlights potential seasonal and highly-localized pulses in reef toxin loads that may be transferred to higher trophic levels.

Evaluation of 24-h screen deployments as a standardized platform to monitor Gambierdiscus populations in the Florida Keys and U.S. Virgin Islands.

Anchored mesh screens have been suggested as a standardized approach to monitor the cell abundances of epiphytic dinoflagellates in benthic habitats, including toxigenic members of the Gambierdiscus genus responsible for ciguatera poisoning (CP). Here we deployed screens for 24h at eight sites in the Florida Keys and St. Thomas (US Virgin Islands) to evaluate their performance relative to the traditional method of assessing Gambierdiscus abundance in which cell counts are normalized to wet weight of host algae. The 30-month study (April 2013 - August 2015) involved monthly sampling at sites where screens were suspended at near-bottom locations for a 24h period and retrieved, with concurrent collections of macrophytes; including Halimeda, Laurencia, and Thalassia in the Florida Keys, and Dictyota in both regions. Gambierdiscus cells were identified and enumerated in the screen and macrophyte samples, and several regression techniques were evaluated (linear regression using untransformed and log-transformed data; negative binomial distribution (NBD) regression) to determine how well the screen-derived data could estimate algal cell concentrations on the host algae. In all cases, the NBD models performed the best based on Akaike Information Criteria values, although 38% of the regressions were not statistically-significant, including all of the St. Thomas sites. The r2 values were all < 0.75 and averaged 0.36, indicating relatively poor fit of the screen data. False negative results (regression models underestimating actual cell abundances) were common occurrences, ranging from 5 to 74% of the scenarios tested. In summary, these results indicate that 24h screen deployments do not appear to be consistent in all situations. Caution is therefore needed when considering 24h screens as a standardized monitoring approach for quantifying Gambierdiscus population dynamics across geography and ecosystems. Furthermore, neutral (artificial) substrates may not adequately capture either the host preference or palatability that likely influence the initial vector of toxin incorporation in the food web via herbivory on these macrophytes.

Retrospective analysis of trends in surgery volumes between 2016 and 2019 and impact of the insurance deductible: Cross-sectional study.

BACKGROUND: Understanding trends in surgical volumes can help Ambulatory Surgery Centers (ASCs) prevent clinician burnout and provide adequate staffing while maintaining the quality of patient care throughout the year. Health insurance deductibles reset in January each year and may contribute to an annual rhythm where the levee of year-end deductibles is breached in the last few months of every year, resulting in a flood of cases and several accompanying challenges. This study aims to identify and analyze monthly and yearly surgical volume patterns in ASCs and explore a relationship with the deductible reset. METHODS: De-identified, aggregate visit data for 2016-2019 were obtained retrospectively from 14 ambulatory surgery centers within the same benchmarking consortium in the Southeast. The ASCs subspecialty types consisted of orthopedics, urology, otolaryngology, and multispecialty. Kaiser Family Foundation survey data from 2016 to 2019 was used to inform deductible trends. Augmented Dickey-Fuller tests, linear regressions, and two-sample T-tests were conducted to explore and establish patterns in surgical volume between 2016 and 2019. RESULTS: Overall, average orthopedic surgical volume increased 38.04% from January to December in 2016-2019 with an average difference of 64 cases (95% CI: 47-80), while that of all ASCs combined increased 19.24% within the same timeframe with an average difference of 37 cases (95% CI: 21-52). Average health insurance deductibles rose 12% from $1476 to $1655 within the same timeframe. Regression analysis showed a stronger association between year and volume for orthopedic ASCs (R (Claxton et al., 2019) [2] = 0.796) than for all ASCs combined (R (Claxton et al., 2019) [2] = 0.645). Regression analysis also showed a stronger association between month and volume for orthopedic ASCs (R (Claxton et al., 2019) [2] = 0.488-0.805) than for all ASCs combined (R (Claxton et al., 2019) [2] = 0.115-0.493). CONCLUSION: This study is first to identify regular and predictable yearly and monthly increases in orthopedic ASCs surgical volume. The study also identifies yearly increases in surgical volume for all ASCs. The combination of increasing yearly demand for orthopedic surgery and growing association between month and volume leads to an unnecessary year-end rush. The study aims to inform future policy decisions as well as help ASCs better manage resources throughout the year.

Development of fluorescence in situ hybridization (FISH) probes to detect and enumerate Gambierdiscus species.

Ciguatera poisoning (CP) is a syndrome caused by the bioaccumulation of lipophilic ciguatoxins in coral reef fish and invertebrates, and their subsequent consumption by humans. These phycotoxins are produced by Gambierdiscus spp., tropical epiphytic dinoflagellates that live on a variety of macrophytes, as well as on dead corals and sand. Recent taxonomic studies have identified novel diversity within the Gambierdiscus genus, with at least 18 species and several sub-groups now identified, many of which co-occur and differ significantly in toxicity. The ability to accurately and quickly distinguish Gambierdiscus species in field samples and determine community composition and abundance is central to assessing CP risk, yet most Gambierdiscus species are indistinguishable using light microscopy, and other enumeration methods are semi-quantitative. In order to investigate the spatial and temporal dynamics of Gambierdiscus species and community toxicity, new tools for species identification and enumeration in field samples are needed. Here, fluorescence in situ hybridization (FISH) probes were designed for seven species commonly found in the Caribbean Sea and Pacific Ocean, permitting their enumeration in field samples using epifluorescence microscopy. This technique enables the assessment of community composition and accurate determination of cell abundances of individual species. Molecular probes detecting G. australes, G. belizeanus, G. caribaeus, G. carolinianus, G. carpenteri, and the G. silvae/G. polynesiensis clade were designed using alignments of large subunit ribosomal RNA (rRNA) sequences. These probes were tested for specificity and cross-reactivity through experiments in which field samples were spiked with known concentrations of Gambierdiscus cultures, and analyzed to confirm that Gambierdiscus can be successfully detected and enumerated by FISH in the presence of detritus and other organisms. These probes were then used to characterize Gambierdiscus community structure in field samples collected from the Florida Keys and Hawai'i, USA. The probes revealed the co-occurrence of multiple species at each location. Time-series FISH analyses of samples collected from the Florida Keys quantified seasonal shifts in community composition as well as fluctuations in overall Gambierdiscus cell abundance. Application of species-specific FISH probes provides a powerful new tool to those seeking to target individual Gambierdiscus species, including significant toxin-producers, in field populations. Moving forward, analysis of Gambierdiscus community composition across multiple environments and over time will also allow species dynamics to be linked to environmental parameters, improving our ability to understand and manage the current and changing risks of CP worldwide.

Development of a reef fish biological condition gradient model with quantitative decision rules for the protection and restoration of coral reef ecosystems.

Coral reef ecosystems are declining due to multiple interacting stressors. A bioassessment framework focused on stressor-response associations was developed to help organize and communicate complex ecological information to support coral reef conservation. This study applied the Biological Condition Gradient (BCG), initially developed for freshwater ecosystems, to fish assemblages of U.S. Caribbean coral reef ecosystems. The reef fish BCG describes how biological conditions changed incrementally along a gradient of increasing anthropogenic stress. Coupled with physical and chemical water quality data, the BGC forms a scientifically defensible basis to prioritize, protect and restore water bodies containing coral reefs. Through an iterative process, scientists from across the U.S. Caribbean used fishery-independent survey data and expert knowledge to develop quantitative decision rules to describe six levels of coral reef ecosystem condition. The resultant reef fish BCG provides an effective tool for identifying healthy and degraded coral reef ecosystems and has potential for global application.

Suture Button Suspensionplasty in the Treatment of Carpometacarpal Arthritis: A Retrospective Analysis of One Surgeon's Experience Over 9 Years.

Purpose: Trapeziectomy with suture button suspensionplasty (SBS) to treat thumb carpometacarpal (CMC) arthritis has been proposed as an alternative to ligament reconstruction tendon interposition. There have been limited large-scale or long-term reports regarding SBS outcomes. Single-surgeon intermediate follow-up is reported. Methods: We conducted a retrospective review of patients undergoing SBS procedures by a single surgeon. Implant manufacturer and postoperative immobilization protocol were recorded. Surgical outcomes, complications, and revision procedures were identified. Postoperative Disabilities of the Arm, Shoulder, and Hand scores were collected. Results: A total of 242 SBS surgeries were included, involving 215 patients, average age 64.82 years (range, 42-86 years). Average follow-up was 35 ± 25 months. In all, 183 Arthrex and 59 Stryker systems were used, 42 of which were immobilized for 6 weeks after surgery and 200 of which were mobilized at 2 weeks afterward. Postoperative Disabilities of the Arm, Shoulder, and Hand surveys were completed by 122 patients (57%), with an average score of 12. No scaphometacarpal abutment was reported. Thirteen complications were reported (5%), 7 of which were implant-associated (3%) and 6 of which were not (2%). Implant-associated complications consisted of 3 suture button pull-outs, 2 thumb-index metacarpal abutments, one suture tail irritation, and one index metacarpal fracture. Operative revision was required in 4 of 7 implant-associated cases and 5 of 6 non-implant associated cases. No suture button pull-outs required revision surgery. Conclusions: Results for a large series of SBS for CMC arthroplasty with intermediate follow-up revealed excellent clinical outcomes and low complication rates. Clinical relevance: Suture button suspensionplasty as an alternative to ligament reconstruction tendon interposition may be a viable option for treating thumb CMC arthritis. In addition, a technique to manage thumb-index metacarpal abutment is described.

State of corals and coral reefs of the Galápagos Islands (Ecuador): Past, present and future.

Coral populations and structural coral reefs have undergone severe reductions and losses respectively over large parts of the Galápagos Islands during and following the 1982-83 El Niño event. Coral tissue loss amounted to 95% across the Archipelago. Also at that time, all coral reefs in the central and southern islands disappeared following severe degradation and eventual collapse due primarily to intense bioerosion and low recruitment. Six sites in the southern islands have demonstrated low to moderate coral community (scattered colonies, but no carbonate framework) recovery. The iconic pocilloporid reef at Devil's Crown (Floreana Island) experienced recovery to 2007, then severe mortality during a La Niña cooling event, and is again (as of 2017) undergoing rapid recovery. Notable recovery has occurred at the central (Marchena) and northern islands (Darwin and Wolf). Of the 17 structural reefs first observed in the mid-1970s, the single surviving reef (Wellington Reef) at Darwin Island remains in a positive growth mode. The remainder either degraded to a coral community or was lost. Retrospective analyses of the age structure of corals killed in 1983, and isotopic signatures of the skeletal growth record of massive corals suggest the occurrence of robust coral populations during at least a 500-year period before 1983. The greatest potential threats to the recovery and persistence of coral reefs include: ocean warming and acidification, bioerosion, coral diseases, human population growth (increasing numbers of residents and tourists), overfishing, invasive species, pollution, and habitat destruction. Such a diverse spectrum of disturbances, acting alone or in combination, are expected to continue to cause local and archipelago-wide mortality and degradation of the coral reef ecosystem.

Depth and coral cover drive the distribution of a coral macroborer across two reef systems.

Bioerosion, the removal of calcium carbonate from coral frameworks by living organisms, influences a variety of reef features, from their topographic complexity to the net balance of carbonate budgets. Little is known, however, about how macroborers, which bore into reef substrates leaving traces greater than 0.1 mm diameter, are distributed across coral reefs, particularly reef systems with high (>50%) stony coral cover or at mesophotic depths (≥30 m). Here, we present an accurate and efficient method for quantifying macroborer densities from stony coral hosts via image analysis, using the bioeroding barnacle, Lithotrya dorsalis, and its host coral, Orbicella franksi, as a case study. We found that in 2014, L. dorsalis densities varied consistently with depth and host percent cover in two Atlantic reef systems: the Flower Garden Banks (FGB, northwest Gulf of Mexico) and the U.S. Virgin Islands (USVI). Although average barnacle density was nearly 4.5 times greater overall in the FGB than in the USVI, barnacle density decreased with depth in both reef regions. Barnacle density also scaled negatively with increasing coral cover in the study areas, suggesting that barnacle populations are not strictly space-limited in their distribution and settlement opportunities. Our findings suggest that depth and host coral cover, and potentially, local factors may strongly influence the abundance of macroborers, and thus the rate of CaCO3 loss, in a given reef system. Our image analysis method for quantifying macroborers can be standardized across historical and modern reef records to better understand how borers impact host growth and reef health.

Ciguatoxin prevalence in 4 commercial fish species along an oceanic exposure gradient in the US Virgin Islands.

Ciguatera fish poisoning is a seafood-toxin illness resulting from consumption of fish contaminated with ciguatoxins. Managing ciguatera fish poisoning is complex. It is made easier, however, by local fishers from endemic areas reporting regional predictability for local fish species' ciguatera fish poisoning risk, which the present study then tested. We investigated the prevalence of ciguatoxins in 4 commonly marketed and consumed species (Balistes vetula, Haemulon plumierii, Ocyurus chrysurus, and Epinephelus guttatus) across an oceanic gradient (north, south, east, and west) from the US Virgin Islands. Fish muscle extracts were analyzed for Caribbean ciguatoxins using an in vitro mouse neuroblastoma (N2a) cytotoxicity assay and confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Fish collected from the north location had 0 fish with detectable ciguatoxins; this site also had the greatest wave energy. Caribbean ciguatoxins in fish ranged from 0.01 to 0.11, 0.004 to 0.10, and 0.005 to 0.18 ng Caribbean ciguatoxin-1 eq/g, from the west, east, and south respectively. Ciguatoxin-like activity was detectable by the N2a assay in 40, 41, 50, and 70% of H. plumierii, O. chrysurus, B. vetula, and E. guttatus, respectively. Of the fish collected, 4% had Caribbean ciguatoxin levels exceeding the US Food and Drug Administration guidance of 0.1 ng Caribbean ciguatoxin-1 eq/g fish. These findings concurred with spatial ciguatera fish poisoning prevalence information provided by local fishers in the US Virgin Islands and demonstrate how partnerships between researchers and fishers can aid the improvement of science-based ciguatera fish poisoning management. Environ Toxicol Chem 2018;39:1852-1863. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.