Proactive assisted gene flow for Caribbean corals in an era of rapid coral reef decline.

Regulatory action could facilitate cross-border efforts to retain ecosystem function.

Cell type-specific immune regulation under symbiosis in a facultatively symbiotic coral.

Many cnidarians host single-celled algae within gastrodermal cells, yielding a mutually beneficial exchange of nutrients between host and symbiont, and dysbiosis can lead to host mortality. Previous research has uncovered symbiosis tradeoffs, including suppression of immune pathways in hosts, and correlations between symbiotic state and pathogen susceptibility. Here, we used a multiomic approach to characterize symbiotic states of the facultatively symbiotic coral Oculina arbuscula by generating genotype-controlled fragments of symbiotic and aposymbiotic tissue.

Microbial Depletion Is Associated with Slower Cnidarian Regeneration.

Microbiomes play an important role in physiology and development in cnidarians, but how these communities influence tissue regeneration is poorly understood. Here, we examined the effects of antibiotic exposure on regeneration and microbial communities in two cnidarian models, the sea anemones Nematostella vectensis (non-symbiotic, hereafter, Nematostella) and Exaiptasia diaphana (symbiotic, hereafter, Aiptasia). Bisected animals were incubated in either sterile or antibiotic-treated artificial seawater for 7 days and regeneration was monitored daily.

Genomic comparison of the temperate coral Astrangia poculata with tropical corals yields insights into winter quiescence, innate immunity, and sexual reproduction.

Facultatively symbiotic corals provide important experimental models to explore the establishment, maintenance, and breakdown of the mutualism between corals and members of the algal family Symbiodiniaceae. Here, we report the de novo chromosome-scale genome assembly and annotation of the facultatively symbiotic, temperate coral Astrangia poculata. Though widespread segmental/tandem duplications of genomic regions were detected, we did not find strong evidence of a whole-genome duplication event.

Cryptic coral diversity is associated with symbioses, physiology, and response to thermal challenge.

Coral persistence in the Anthropocene depends on interactions among holobiont partners (coral animals and microbial symbionts) and their environment. Cryptic coral lineages-genetically distinct yet morphologically similar groups-are critically important as they often exhibit functional diversity relevant to thermal tolerance. In addition, environmental parameters such as thermal variability may promote tolerance, but how variability interacts with holobiont partners to shape responses to thermal challenge remains unclear.

Ocean weather, biological rates, and unexplained global ecological patterns.

As on land, oceans exhibit high temporal and spatial temperature variation. This "ocean weather" contributes to the physiological and ecological processes that ultimately determine the patterns of species distribution and abundance, yet is often unrecognized, especially in tropical oceans. Here, we tested the paradigm of temperature stability in shallow waters (<12.

Intersection of coral molecular responses to a localized mortality event and ex situ deoxygenation.

In July 2016, East Bank of Flower Garden Banks (FGB) National Marine Sanctuary experienced a localized mortality event (LME) of multiple invertebrate species that ultimately led to reductions in coral cover. Abiotic data taken directly after the event suggested that acute deoxygenation contributed to the mortality. Despite the large impact of this event on the coral community, there was no direct evidence that this LME was driven by acute deoxygenation, and thus we explored whether gene expression responses of corals to the LME would indicate what abiotic factors may have contributed to the LME.

Gene expression plasticity facilitates acclimatization of a long-lived Caribbean coral across divergent reef environments.

Local adaptation can increase fitness under stable environmental conditions. However, in rapidly changing environments, compensatory mechanisms enabled through plasticity may better promote fitness. Climate change is causing devastating impacts on coral reefs globally and understanding the potential for adaptive and plastic responses is critical for reef management.

Symbiosis modulates gene expression of symbionts, but not coral hosts, under thermal challenge.

Increasing ocean temperatures are causing dysbiosis between coral hosts and their symbionts. Previous work suggests that coral host gene expression responds more strongly to environmental stress compared to their intracellular symbionts; however, the causes and consequences of this phenomenon remain untested. We hypothesized that symbionts are less responsive because hosts modulate symbiont environments to buffer stress.

Starvation differentially affects gene expression, immunity and pathogen susceptibility across symbiotic states in a model cnidarian.

Mutualistic symbioses between cnidarians and photosynthetic algae are modulated by complex interactions between host immunity and environmental conditions. Here, we investigate how symbiosis interacts with food limitation to influence gene expression and stress response programming in the sea anemone (Aiptasia). Transcriptomic responses to starvation were similar between symbiotic and aposymbiotic Aiptasia; however, aposymbiotic anemone responses were stronger.

Integrating cryptic diversity into coral evolution, symbiosis and conservation.

Understanding how diversity evolves and is maintained is critical to predicting the future trajectories of ecosystems under climate change; however, our understanding of these processes is limited in marine systems. Corals, which engineer reef ecosystems, are critically threatened by climate change, and global efforts are underway to conserve and restore populations as attempts to mitigate ocean warming continue. Recently, sequencing efforts have uncovered widespread undescribed coral diversity, including 'cryptic lineages'-genetically distinct but morphologically similar coral taxa.

Marine heatwaves threaten cryptic coral diversity and erode associations among coevolving partners.

Climate change-amplified marine heatwaves can drive extensive mortality in foundation species. However, a paucity of longitudinal genomic datasets has impeded understanding of how these rapid selection events alter cryptic genetic structure. Heatwave impacts may be exacerbated in species that engage in obligate symbioses, where the genetics of multiple coevolving taxa may be affected.

Starvation decreases immunity and immune regulatory factor NF-κB in the starlet sea anemone Nematostella vectensis.

Lack of proper nutrition has important consequences for the physiology of all organisms, and nutritional status can affect immunity, based on many studies in terrestrial animals. Here we show a positive correlation between nutrition and immunity in the sea anemone Nematostella vectensis. Gene expression profiling of adult anemones shows downregulation of genes involved in nutrient metabolism, cellular respiration, and immunity in starved animals.

Rampant asexual reproduction and limited dispersal in a mangrove population of the coral .

Corals are critical to marine biodiversity. Reproduction and dispersal are key to their resilience, but rarely quantified in nature. Exploiting a unique system-a fully censused, longitudinally characterized, semi-isolated population inhabiting mangroves-we used 2bRAD sequencing to demonstrate that rampant asexual reproduction most likely via parthenogenesis and limited dispersal enable the persistence of a natural population of thin-finger coral ().

Heat challenge elicits stronger physiological and gene expression responses than starvation in symbiotic Oculina arbuscula.

Heterotrophy has been shown to mitigate coral-algal dysbiosis (coral bleaching) under heat challenge, but the molecular mechanisms underlying this phenomenon remain largely unexplored. Here, we quantified coral physiology and gene expression of fragments from 13 genotypes of symbiotic Oculina arbuscula after a 28-d feeding experiment under (1) fed, ambient (24 °C); (2) unfed, ambient; (3) fed, heated (ramp to 33 °C); and (4) unfed, heated treatments. We monitored algal photosynthetic efficiency throughout the experiment, and after 28 d, profiled coral and algal carbohydrate and protein reserves, coral gene expression, algal cell densities, and chlorophyll-a and chlorophyll-c2 pigments.

Evidence of sweepstakes reproductive success in a broadcast-spawning coral and its implications for coral metapopulation persistence.

Processes governing genetic diversity and adaptive potential in reef-building corals are of interest both for fundamental evolutionary biology and for reef conservation. Here, we investigated the possibility of "sweepstakes reproductive success" (SRS) in a broadcast spawning coral, Acropora hyacinthus, at Yap Island, Micronesia. SRS is an extreme yearly variation in the number of surviving offspring among parents.

Help Me, Symbionts, You're My Only Hope: Approaches to Accelerate our Understanding of Coral Holobiont Interactions.

Tropical corals construct the three-dimensional framework for one of the most diverse ecosystems on the planet, providing habitat to a plethora of species across taxa. However, these ecosystem engineers are facing unprecedented challenges, such as increasing disease prevalence and marine heatwaves associated with anthropogenic global change. As a result, major declines in coral cover and health are being observed across the world's oceans, often due to the breakdown of coral-associated symbioses.

Global change differentially modulates Caribbean coral physiology.

Global change driven by anthropogenic carbon emissions is altering ecosystems at unprecedented rates, especially coral reefs, whose symbiosis with algal symbionts is particularly vulnerable to increasing ocean temperatures and altered carbonate chemistry. Here, we assess the physiological responses of three Caribbean coral (animal host + algal symbiont) species from an inshore and offshore reef environment after exposure to simulated ocean warming (28, 31°C), acidification (300-3290 μatm), and the combination of stressors for 93 days. We used multidimensional analyses to assess how a variety of coral physiological parameters respond to ocean acidification and warming.

Microbial Community Dynamics Provide Evidence for Hypoxia during a Coral Reef Mortality Event.

In July 2016, a severe coral reef invertebrate mortality event occurred approximately 200 km southeast of Galveston, Texas, at the East Flower Garden Bank, wherein ∼82% of corals in a 0.06-km area died. Based on surveys of dead corals and other invertebrates shortly after this mortality event, responders hypothesized that localized hypoxia was the most likely direct cause.

Genetic divergence and range expansion in a western North Pacific coral.

Coral poleward range expansions have recently been observed in response to warming oceans. Range expansion can lead to reduced genetic diversity and increased frequency of deleterious mutations that were rare in core populations, potentially limiting the ability for adaptation and persistence in novel environments. Successful expansions that overcome these founder effects and colonize new habitat have been attributed to multiple introductions from different sources, hybridization with native populations, or rapid adaptive evolution.

The Marine Gastropod Remains Resilient to Ocean Acidification Across Two Life History Stages.

Rising atmospheric CO reduces seawater pH causing ocean acidification (OA). Understanding how resilient marine organisms respond to OA may help predict how community dynamics will shift as CO continues rising. The common slipper shell snail is a marine gastropod native to eastern North America that has been a successful invader along the western European coastline and elsewhere.

Characterizing environmental stress responses of aposymbiotic Astrangia poculata to divergent thermal challenges.

Anthropogenic climate change threatens corals globally and both high and low temperatures are known to induce coral bleaching. However, coral stress responses across wide thermal breadths remain understudied. Disentangling the role of symbiosis on the stress response in obligately symbiotic corals is challenging because this response is inherently coupled with nutritional stress.