Drivers of resistance to stony coral tissue loss disease (SCTLD), infrastructural improvements, and 2023 bleaching response

This project supported three different projects at the University of Miami. The first project undertook genetic analyses of samples that were collected from an experiment run with DEP support in FY23, which assessed how early-stage recruits of three different coral species responded to exposure to stony coral tissue loss disease (SCLTD). With FY24 funding, we initiated genetic analyses to determine the parentage of different recruits to assess whether certain parents contributed disproportionately to the recruits that died from SCTLD compared to those that survived. We also undertook microbiome (16S) analyses of the bacterial communities in these recruits to determine whether components of the microbiome were heritable from parents to offspring, and whether there are correlations between certain microbes and susceptibility/resistance of recruits.

To genotype our recruits and parents, we collaborated with FWRI to apply new genetic assays they had developed for the Florida Coral Rescue project. However, recently FWRI, using these new assays, found evidence for a cryptic species of Colpophyllia in Florida. This has complicated the analysis of our samples and led to a delay obtaining final data in the project timeframe (although the samples are still in the pipeline). However, our microbiome analyses are complete and although we need the genetic data to fully interpret them, we have already found that recruit microbiomes vary by coral species and SCTLD exposure, and that SCTLD induces microbiome changes in favor of particular bacterial taxa that are associated with diseased adult corals, even when lesions have not yet been observed. Once the genetic data become available from FWRI, we will be able to relate microbiome composition to parentage and assess whether maternal transmission of the microbiome might help explain patterns of susceptibility in
our experimental trials. In the second project, we converted flow-through coral systems in our indoor labs into recirculating systems to improve water quality and decrease the impacts of variation
in the local seawater supply on coral health. This involved a complete tear-down and reconfiguration of the lab, refinishing of tanks, addition of sumps, and multi-purpose plumbing to allow different systems to operate either together or independently.

In the third project, we improved indoor and outdoor coral propagation systems in order to support the 2023 bleaching response in Florida, and cared for >2,000 corals that were rescued from nurseries during that event. These corals have since been successfully returned to the nurseries with no loss of genotypes.