Integrating tools and disciplines to understand the future of Southwestern Atlantic shallow-water corals in a changing planet

Abstract

Covering less than 0.1% of the ocean flor, warm, shallow-water coral reefs are recognized for supporting over a quarter of the worlds' marine biodiversity and also for the critical ecosystem services they provide to human kind. Nonetheless, due to the ongoing climate change and other anthropogenic challenges, about 75% of the coral reefs are considered threatened, with several already severely degraded or under phase-shift to algal dominated habitats. Even though some hope has been put forward - the extinction risk of most coral species is lower than previously thought and, as a lineage, scleractinian corals have persisted to at least four of the five great mass extinction events -, it is a common sense that coral reefs are not going to be the same for the future generations. In the Southwestern Atlantic (SWA) the panorama is not different, with stronger and more frequent ocean thermal anomalies taking its toll on coral cover. Nevertheless, although displaying low diversity (but high endemicity), corals from this region have been purported to be more resistant and even more resilient to the warming ocean effects. Such "shielding" being the result of the more nutrient rich, turbid waters that our corals are adapted. However, we know virtually nothing on the genetic structure and genetic diversity of the SWA coral populations. Overall, genetic diversity is an essential source for biodiversity, providing the raw material for evolution. When interconnected, populations tend to preserve greater genetic diversity compared to more isolated populations, which in turn are more susceptible to genetic drift effects. Thus, endeavoring to fill such gaps and, consequently, improve our understanding in how climate change has and is shaping SWA coral evolution as a lineage and as a system, the present proposal consists of consolidating an interdisciplinary research line cored on RNA/DNA deep sequencing and its usefulness at the Department of Marine Science of the Federal University of São Paulo (DCMar-UNIFESP). Overall, advances in high-throughput sequencing and SNP genotyping technologies have greatly expanded our ability to identify signatures of positive selection. Such signatures help us to delimit regions of the genome that are, or have been, functionally important, poiting towards the identification of genetic variation that contributes to phenotypic diversity and genotype selection. Examining such diversity in the light of phylogeny / phylogeography / holobiont will open horizons to explore where, when and how traits - of any nature - have changed over different time scales. Retrieved biological patterns at population and specific levels will also enable the proposition of evolutionary processes and subsequent transformations of corals in light of environment variables. Therefore, at the onset of the Decade of the Ocean, and understanding that such knowledge is essential to define efficient management and conservation strategies, the present proposal will persue long lasting questions regarding the major architects of shallow-water coral reefs in times not just of major scientific interest, but also intense public and media concern because of the uncertain fate of these ecosystems in the face of ever increasing anthropogenic challenges. (AU)