First recorded presence of anthropogenic fly-ash particles in coral skeletons

Fly-ash particles formed during industrial fossil-fuel combustion show a globally observed rapid increase in concentration within natural archives post-1950 and have been proposed as a marker for the Anthropocene Epoch. Here, we present the first record of fly-ash particles incorporated into coral skeletons. Particles are present in Mediterranean corals between CE 1957 and 1992 at concentrations of 8-30 g-1 coral, mirroring the period of increased industrial activity in the area, and corroborating with spheroidal carbonaceous particle (SCP) records globally. The findings have important implications for the use of SCPs as markers in natural archives. With the exception of microplastics, this is the first evidence of particulate contamination in corals collected from natural environments. Further research is needed to understand incorporation pathways into coral skeletons, any subsequent ecotoxicological impact of contaminants, and the influence on overall coral health globally.

Species-Area Relationship (SAR) models as tools for estimating faunal biodiversity associated with habitat builder species in sensitive areas: the case of the Mediterranean stony coral (Cladocora caespitosa)

Biodiversity associated with the Mediterranean stony coral Cladocora caespitosa (Linnaeus, 1767) was investigated at three levels: "microscale", focused on macrobenthic invertebrates within colonies; "mesoscale", focused on epibenthic megafauna among colonies; "macroscale", focused on associated ichthyofauna. The aim was to quantify associated diversity in terms of species richness, testing the efficiency of colony size (surface covered by a single colony) for the "microscale", and colony density or total coral coverage for "meso-" and "macroscale" as predictors and the consistency of models based on Species-Area Relationship (SAR) for those estimations. At level of "microscale", colony size was a good predictor, with richness of invertebrates increasing with the increasing of surface covered by each colony of C. caespitosa, following Arrhenius model. At levels of "mesoscale" and "macroscale", richness of epibenthic megafauna and fish were not related neither to colony density nor total coral coverage, but to sampled area, and frequency-based estimates of richness were used. The importance of C. caespitosa varied according to the investigation level, with most of taxa richness detected at the level of "microscale".

Biogeographic Differences in the Microbiome and Pathobiome of the Coral Cladocora caespitosa in the Western Mediterranean Sea

The endemic Mediterranean zooxanthellate scleractinian reef-builder Cladocora caespitosa is among the organisms most affected by warming-related mass mortality events in the Mediterranean Sea. Corals are known to contain a diverse microbiota that plays a key role in their physiology and health. Here we report the first study that examines the microbiome and pathobiome associated with C. caespitosa in three different Mediterranean locations (i.e., Genova, Columbretes Islands, and Tabarca Island). The microbial communities associated with this species showed biogeographical differences, but shared a common core microbiome that probably plays a key role in the coral holobiont. The putatively pathogenic microbial assemblage (i.e., pathobiome) of C. caespitosa also seemed to depend on geographic location and the human footprint. In locations near the coast and with higher human influence, the pathobiome was entirely constituted by Vibrio species, including the well-known coral pathogens Vibrio coralliilyticus and V. mediterranei. However, in the Columbretes Islands, located off the coast and the most pristine of the analyzed locations, no changes among microbial communities associated to healthy and necrosed samples were detected. Hence, our results provide new insights into the microbiome of the temperate corals and its role in coral health status, highlighting its dependence on the local environmental conditions and the human footprint.