Species at the forefront concerndue to changes in environmental conditions in the anthropocene are coral reefs,whose keystone species are sensitive to environmental perturbations at a localand global scale (Putnam et al., 2017). Particularly, the intricate anddelicate mutualistic relationship between the cnidarian host, with focus on scleractiniancorals, and its single cell endosymbiont dinoflagellate resident, Symbiodinium sp.
, is responsible forreef accretion of over 10,000 g CaCO3 m-2 a year (Cohenet al., 2009). The Symbiodinium sp. provides the coral with itspigmentation and organic compounds necessary for survival such as glucose,glycerol, and amino acids as products of photosynthesis, serving as the maindriver for coral growth. In exchange, the coral provides the symbiont with anutrient rich environment from organic waste products necessary forphotosynthesis. The recent increase in ocean sea surfacetemperature (SST) threatens to permanently disrupt this relationship (Glynn, 1996).
These changes in climate during the anthropocene have already been observed asthere has been a rapid decrease of coral cover due mass mortality andbleaching, the physical manifestation of the end of the mutualisticrelationship between the coral host and its symbiont (Ainsworth et al., 2016). Thecurrent status of coral reefs is of primary concern, as they support ecosystemsvalued at over 100’s of billions of dollars (Costanza et al., 2014) and provideprotection from high-energy waves to islands and shorelines, preventing erosion(Carpenter et al.
, 2008). Therefore, the identification of a mechanism throughwhich the coral holobiont, the assemblage of the coral host and its symbiont,may be capable of rapid acclimatization to these changes in both local andglobal conditions is of primary concern in order to implement measures that mayprevent the collapse of the marine ecosystems and include climate change modelsto predict the future of marine populations.Research that concerns coralreproduction, fecundity and recruitment is of great importance, as it shedslight on the relationship between species and local climate, and speciespersistence in future generations in an area undergoing rapid changes in bioticand abiotic factors. Porites astreoides isa well-know, stony, reef building coral common in the Caribbean Sea andAtlantic Ocean. As a brooder, Porites astreoides relies on internalfertilization to achieve reproduction. Around the new moon, the internallybrooded larvae are released as planulae larvae which then drift in the watercolumn until they settle onto the seabed and each metamorphose into aflower-like shape, known as a primary polyp. Each planula grows into a colonyby initiating the production of a CO3 skeleton and budding, a typeof asexual reproduction in which a new bulb-like organism is developed throughcell division.
Previously in Bermuda, research onthis coral has shown that differences in fitness, i.e. survival andreproduction, may be attributed to differences in reef zones, e.g. patch andrim. Corals located in patch reef areas exist in water conditions that are notbuffered by the cold deep ocean waters and are therefore exposed to moreextreme changes in temperature while corals located in rim areas are moresheltered to these extreme conditions due to the incoming currents carrying thecold, deep waters which allow for a stabilization in temperature.
Areproductive time shift table describing differences in spawning of Porites astreoides has shown that thesedifferences in abiotic factors between the patch and the rim reefs may be theunderlying cues responsible for spawning (de Putron et al. 2014). These abioticfactors may also lead to larval phenotypic differences which can lead todifferences in settlement success and changes in population dynamics (de Putronet al. 2017). Variation in fitness amongconspecifics that exist under different abiotic factors may be explainedthrough differences at the molecular level. Specifically, a comparison of epigeneticpatterns due to mechanisms such as DNA methylation may provide insight as towhat creates these differences among conspecifics (Feil and Fraga 2012). DNAmethylation is an epigenetic mechanism that is capable of providing multipleoutcomes out of the same genetic material by regulating gene expression throughthe addition of a methyl group (CH3) to DNA nucleotides (reviewed inVerhoeven et al.
2016). These changes through DNA methylation areenvironmentally induced and may have potential transgenerational inheritance.Through this mechanism, organisms are shaped by the environment in which theycurrently exist allowing for phenotypic plasticity. The ability of corals to rapidlyacclimatize to local changes in their environment through epigenetic mechanismsis a new area. Previous research on Pocilloporadamicornis is the first one to show rapid environmentally-induced changesin total percent of DNA methylation with possible implication of changes in theperformance of the organism both in metabolism functions and growth (Putnam etal., 2016). Furthermore, these changes in gene expression of the parentalgenome through methylation due to environmental stress can be inherited by theoffspring (Bonduriansky and Day, 2009). Transgenerational epigenetic changescan either promote an adaptive response, allowing for rapid acclimatizationwithin a single generation or exacerbate the negative response to the presentstressor (Putnam et al.
, 2015). Acclimatization, through phenotypic variation,therefore may provide a compensatory response for these rapid anthropogenicenvironmental changes which can alleviate the severity of the abiotic stressorson coral population survival. In order to address thesequestions, the study of the coral Poritesastreoides in conjunction to an area such as Bermuda provides the idealplatform for such an experiment. Geographically, Bermuda provides multipletypes of reef zones within close proximity of one another. This allows for anenvironment of high genetic connectivity among conspecifics separated by areasof different abiotic factors and thus phenotypic differences across reef-zones(de Putron et al., 2017). Furthermore, as an internal brooder, Porites astreoides provides to be anideal model organism to study transgenerational acclimatization responses asthe environment may alter larval development during the internal broodingprocess of the parent (Bonduriansky and Day 2009). The goal of this study is toinvestigate the mechanisms underlying phenotypic variance, thus differences inreproductive output between conspecifics, and how this may affect thesurvivorship of their offspring.