Francesca Virdis

Abstract Coral reefs are some of the most diverse and valuable ecosystems worldwide. Since the 1970’s the coral populations of Acropora spp. around Bonaire Island have been declining due to White Band Disease (WBD) and due to heavy storms and hurricanes (i.e., hurricane Lenny in 1999). Acropora cervicornis is one of the species selected as restoration target because its critically endangered status according to the IUCN red list and its ecological value as reef builder. Promoting genetic diversity is key to aid the recovery of degraded populations and give this species higher chance to survive in the long-term. In this study, we measure growth and healing, as phenotypic traits of propagated corals to assess the different genotype performance in the nursery phase. Linear length and tissue regeneration have been monitored for 8 weeks for 10 different genotypes (n=5), respectively with in situ measurement and image analysis. The preliminary results suggest that some individual fragments can grow up to one centimeter per week and achieve complete tissue regeneration from cutting and handling damage in 15 days. Being able to determinate the differences in performance from various coral genotypes can help nursery based coral restoration to be more performant. Indeed, selecting coral genotypes that can grow and regenerate faster is a considerable advantage for coral restoration practitioners that could therefore optimize their outplanting efforts.

Abstract

Coral reefs are known to be among the most biodiverse marine ecosystems and one of the richest in terms of associations and species interactions, especially those involving invertebrates such as corals and sponges. Despite that, our knowledge about cryptic fauna and their ecological role remains remarkably scarce. This study aimed to address this gap by defining for the first time the spatial ecology of the association between the epibiont hydrozoan Nemalecium lighti and the Porifera community of shallow coral reef systems at Bonaire. In particular, the host range, prevalence, and distribution of the association were examined in relation to different sites, depths, and dimensions of the sponge hosts. We report Nemalecium lighti to be in association with 9 out of 16 genera of sponges encountered and 15 out of 16 of the dive sites examined. The prevalence of the hydroid–sponge association in Bonaire reef was 6.55%, with a maximum value of over 30%. This hydrozoan has been found to be a generalist symbiont, displaying a strong preference for sponges of the genus Aplysina, with no significant preference in relation to depth. On the contrary, the size of the host appeared to influence the prevalence of association, with large tubular sponges found to be the preferred host. Although further studies are needed to better understand the biological and ecological reason for these results, this study improved our knowledge of Bonaire’s coral reef cryptofauna diversity and its interspecific associations. View Full-Text