Differential apicomplexan presence predicts thermal stress mortality in the Mediterranean coral Paramuricea clavata

Abstract

Paramuricea clavata is an ecosystem architect of the Mediterranean temperate reefs that is currently threatened by episodic mass mortality events related to global warming. The microbiome may play an active role in the thermal stress susceptibility of corals, potentially holding the answer as to why corals show differential sensitivity to heat stress. To investigate this, the prokaryotic and eukaryotic microbiome of P. clavata collected from around the Mediterranean was characterised before experimental heat stress to determine if its microbial composition influences the thermal response of the holobiont. We found that members of P. clavata's microeukaryotic community were significantly correlated with thermal stress sensitivity. Syndiniales from the Dino‐Group I Clade 1 were significantly enriched in thermally resistant corals, while the apicomplexan corallicolids were significantly enriched in thermally susceptible corals. We hypothesise that P. clavata mortality following heat stress may be caused by a shift from apparent commensalism to parasitism in the corallicolid‐coral host relationship driven by the added stress. Our results show the potential importance of corallicolids and the rest of the microeukaryotic community of corals to understanding thermal stress response in corals and provide a useful tool to guide conservation efforts and future research into coral‐associated microeukaryotes.

Recurrent extreme climatic events are driving gorgonian populations to local extinction: low adaptive potential to marine heatwaves

“…Here, we found relatively similar and high levels of necrosis among populations with a prevailing impact of the environmental component. These findings contrast to our previous studies based on “single event” experiments at larger spatial scales where differential ecological responses (distinct necrosis levels) were observed among populations in some cases (Arizmendi-Mejía, et al, 2015a; Arizmendi-Mejía et al, 2015b; Bonacolta et al, 2024; Crisci et al, 2017; Gómez-Gras et al, 2022). Two non-exclusive hypotheses relying on the spatial and temporal features of the experiments might explain this apparent discrepancy.…”

“…The copyright holder for this preprint this version posted May 14, 2024. ; https://doi.org/10. 1101.05.13.593802 doi: bioRxiv preprint et al, 2015aArizmendi-Mejía et al, 2015b;Bonacolta et al, 2024;Crisci et al, 2017;Gómez-Gras et al, 2022). Two non-exclusive hypotheses relying on the spatial and temporal features of the experiments might explain this apparent discrepancy.…”

“…Two non-exclusive hypotheses relying on the spatial and temporal features of the experiments might explain this apparent discrepancy. The experiments conducted to date in P. clavata have considered a wide range of geographic distances, from local to regional (Arizmendi-Mejía et al, 2015b;Crisci et al, 2017) and interregional (Bonacolta et al, 2024;Gómez-Gras et al, 2022) scales. These experiments demonstrated population heterogeneity in ecological responses to thermal stress triggered by different drivers (e.g.…”

“…We then plotted each individual phenotype (PCA score) against the environmental value for each year and we computed the regression slope, which is considered as an estimator of the environmental sensitivity of the genotype (Falconer & Mackay, 1996). We used this plot to classify the sensitivity of the genotypes in three categories adapted from Bonacolta et al (2024). Resistant genotypes were expected to show low intercepts in the first year and approximated null slopes ( i.e.…”