Acropora palmata

Abstract

The plastic ability for a range of phenotypes to be exhibited by the same genotype allows organisms to respond to environmental variation and may modulate fitness in novel environments. Differing capacities for phenotypic plasticity within a population, apparent as genotype by environment interactions (GxE), can therefore have both ecological and evolutionary implications. Epigenetic gene regulation alters gene function in response to environmental cues without changes to the underlying genetic sequence and likely mediates phenotypic variation. DNA methylation is currently the most well described epigenetic mechanism and is related to transcriptional homeostasis in invertebrates. However, evidence quantitatively linking variation in DNA methylation with that of phenotype is lacking in some taxa, including reef-building corals. In this study, spatial and seasonal environmental variation in Bonaire, Caribbean Netherlands was utilized to assess relationships between physiology and DNA methylation profiles within genetic clones across different genotypes of Acropora cervicornis and A. palmata corals. The physiology of both species was highly influenced by environmental variation compared to the effect of genotype. GxE effects on phenotype were only apparent in A. cervicornis. DNA methylation in both species differed between genotypes and seasons and epigenetic variation was significantly related to coral physiological metrics. Furthermore, plastic shifts in physiology across seasons were significantly positively correlated with shifts in DNA methylation profiles in both species. These results highlight the dynamic influence of environmental conditions and genetic constraints on the physiology of two important Caribbean coral species. Additionally, this study provides quantitative support for the role of epigenetic DNA methylation in mediating phenotypic plasticity in invertebrates.

Contact details:

Francesca Virdis (Reef Renewal Bonaire) ->  francesca@reefrenewalbonaire.org

Serena Hackerott (FIU) -> shack013@fiu.edu

Full text available here: https://pubmed.ncbi.nlm.nih.gov/37454286/

Abstract

The plastic ability for a range of phenotypes to be exhibited by the same genotype allows organisms to respond to environmental variation and may modulate fitness in novel environments. Differing capacities for phenotypic plasticity within a population, apparent as genotype by environment interactions (GxE), can therefore have both ecological and evolutionary implications. Epigenetic gene regulation alters gene function in response to environmental cues without changes to the underlying genetic sequence and likely mediates phenotypic variation. DNA methylation is currently the most well described epigenetic mechanism and is related to transcriptional homeostasis in invertebrates. However, evidence quantitatively linking variation in DNA methylation with that of phenotype is lacking in some taxa, including reef-building corals. In this study, spatial and seasonal environmental variation in Bonaire, Caribbean Netherlands was utilized to assess relationships between physiology and DNA methylation profiles within genetic clones across different genotypes of Acropora cervicornis and A. palmata corals. The physiology of both species was highly influenced by environmental variation compared to the effect of genotype. GxE effects on phenotype were only apparent in A. cervicornis. DNA methylation in both species differed between genotypes and seasons and epigenetic variation was significantly related to coral physiological metrics. Furthermore, plastic shifts in physiology across seasons were significantly positively correlated with shifts in DNA methylation profiles in both species. These results highlight the dynamic influence of environmental conditions and genetic constraints on the physiology of two important Caribbean coral species. Additionally, this study provides quantitative support for the role of epigenetic DNA methylation in mediating phenotypic plasticity in invertebrates.

Abstract
Since the severe decline of the Acropora populations in Bonaire in the 1980s, no assessment has characterized the distribution of remnant colonies. Because of their patchy distribution, a large sampling effort is necessary to adequately describe their occurrence. However, the spatial scale at which this assessment needs to be carried out makes this prohibitive with approaches such as transects using SCUBA gear and photogrammetry. This internship project aimed to optimize and apply a simple methodology trialed by relevant stakeholders on the island to obtain coarse but spatially explicit data with relatively low time-investment. Snorkelers utilizing a waterproof GPS and a slate to record coarse categorical data outlined patches of Acropora cervicornis and Acropora palmata in-situ. These were processed with an ArcGIS workflow to create shapefiles of coral patches as polygons joined to their corresponding data. The resulting polygons were used to describe the distribution of Acropora spp. along the leeward coast of Bonaire. Furthermore, these were used as ground-truthing data to test whether remote sensing imagery can be used to detect A. cervicornis remotely. 466 polygons along 14.5km of the coast were created, showing a patchy distribution of both species, more frequent occurrence of A. palmata in the northern leeward coast compared to the southern, and vice-versa for A. cervicornis. A multinomial logistic regression, maximum likelihood classification, and forest-based classification all showed a high accuracy in labelling A. cervicornis correctly in remote sensing data, but all showed frequent misclassification of other reef structures as A. cervicornis. The mapping approach presented in this internship could be applied to investigate fragmentation effects in Acropora populations and to gather in-situ ground-truthing data for other benthic habitats.

For full report or more information,  please contact erik.meesters@wur.nl or gulsah.dogruer@wur.nl

Here we report on damage caused by tropical storm Bret, passing south of the island of Curacao at a distance of 110-145 km in August 1993. Damage on marine life was surveyed 2 weeks after the storm at five localities along the leeward coast of the island. Severe damage was recorded for the scleractinian corals Acropora palmata and Millepora complanata. Dendrogyra cylindrus was incidentally damaged in shallow water, <5 m.

Abstract:

Coral reefs are in severe decline. Infections by the human pathogen Serratia marcescens have contributed to precipitous losses in the common Caribbean elkhorn coral, Acropora palmata, culminating in its listing under the United States Endangered Species Act. During a 2003 outbreak of this coral disease, called acroporid serratiosis (APS), a unique strain of the pathogen, Serratia marcescens strain PDR60, was identified from diseased A. palmata, human wastewater, the non-host coral Siderastrea siderea and the corallivorous snail Coralliophila abbreviata. In order to examine humans as a source and other marine invertebrates as vectors and/or reservoirs of the APS pathogen, challenge experiments were conducted with A. palmata maintained in closed aquaria to determine infectivity of strain PDR60 from reef and wastewater sources. Strain PDR60 from wastewater and diseased A. palmata caused disease signs in elkhorn coral in as little as four and five days, respectively, demonstrating that wastewater is a definitive source of APS and identifying human strain PDR60 as a coral pathogen through fulfillment of Koch’s postulates. A. palmata inoculated with strain PDR60 from C. abbreviata showed limited virulence, with one of three inoculated fragments developing APS signs within 13 days. Strain PDR60 from non-host coral S. siderea showed a delayed pathogenic effect, with disease signs developing within an average of 20 days. These results suggest that C. abbreviata and non-host corals may function as reservoirs or vectors of the APS pathogen. Our results provide the first example of a marine ‘‘reverse zoonosis’’ involving the transmission of a human pathogen (S. marcescens) to a marine invertebrate (A. palmata). These findings underscore the interaction between public health practices and environmental health indices such as coral reef survival. 

Linear extension of branches in the same Acropora palmata (Lamarck, 1816) population in Curaçao was measured, employing exactly the same methods, in 1971–1973 and in 2002–2004, and the resulting coral growth rates are compared. Linear growth shows the same pattern over seasons in both periods with growth being significantly higher in summer than in winter. Growth in the 2002–2004 time interval was significantly slower than in 1971–1973. Mean monthly growth ranged from 0.69 cm (winter) to 0.81 cm (summer) in 1971–1973 and from 0.62 cm (winter) to 0.75 cm (summer) in 2002–2004. This means that linear growth rates in 2002–2004 were 7.2% lower in summer and 10.7% lower in winter compared with 1971–1973. Considering possible causative environmental factors relating to these decreases in growth rate, we cannot preclude the possibility that a change in ocean pH could be responsible for the drop in extension rate.

Ocean acidification (OA) refers to the ongoing decline in oceanic pH resulting from the uptake of atmospheric CO2. Mounting experimental evidence suggests that OA will have negative consequences for a variety of marine organisms. Whereas the effect of OA on the calcification of adult reef corals is increasingly well documented, effects on early life history stages are largely unknown. Coral recruitment, which necessitates successful fertilization, larval settlement, and postsettlement growth and survivorship, is critical to the persistence and resilience of coral reefs. To determine whether OA threatens successful sexual recruitment of reef-building corals, we tested fertilization, settlement, and postsettlement growth of Acropora palmata at pCO2 levels that represent average ambient conditions during coral spawning (∼400 μatm) and the range of pCO2 increases that are expected to occur in this century [∼560 μatm (mid-CO2) and ∼800 μatm (high-CO2)]. Fertilization, settlement, and growth were all negatively impacted by increasing pCO2, and impairment of fertilization was exacerbated at lower sperm concentrations. The cumulative impact of OA on fertilization and settlement success is an estimated 52% and 73% reduction in the number of larval settlers on the reef under pCO2 conditions projected for the middle and the end of this century, respectively. Additional declines of 39% (mid-CO2) and 50% (high-CO2) were observed in postsettlement linear extension rates relative to controls. These results suggest that OA has the potential to impact multiple, sequential early life history stages, thereby severely compromising sexual recruitment and the ability of coral reefs to recover from disturbance