Diversity, structure and demography of coral assemblages on underwater lava flows of different ages at Reunion Island and implications for ecological succession hypotheses

Abstract

Understanding colonization of new habitats and ecological successions is key to ecosystem conservation. However, studies on primary successions are scarce for reef-building corals, due to the rarity of newly formed substratum and the long-term monitoring efforts required for their long life cycle and slow growth rate. We analysed data describing the diversity, structure and demography of coral assemblages on lava flows of different ages and coral reefs at Reunion Island, to evaluate the strength and mechanisms of succession, and its agreement to the theoretical models. No significant differences were observed between the two habitats for most structure and demographic descriptors. In contrast, species richness and composition differentiated coral reefs from lava flows, but were not related to the age of the lava flow. We observed a strong dominance of Pocillopora colonies, which underline the opportunistic nature of this taxa, with life-history traits advantageous to dominance on primary and secondary successional stages. Although some results argue in favor of the tolerance model of succession, the sequences of primary successions as theorized in other ecosystems were difficult to observe, which is likely due to the high frequency and intensity of disturbances at Reunion, that likely distort or set back the expected successional sequences.

Reef‐building corals act as long‐term sink for microplastic

“…Particle ingestion and following deposition rates might be even higher in other species, as previous studies indicate that some species ingest microplastics in similar amounts as natural food (e.g., Dipsastraea pallida; Hall et al, 2015) or even prefer microplastics over natural food (e.g., A. poculata; Allen et al, 2017)-contrary to the here tested species, which differentiate between microplastics and natural food (Martin et al, 2019). Given that the coral families studied on average represent ~70% of worldwide coral communities (Aeby et al, 2021;Jouval et al, 2020;Pandolfi & Minchin, 1996;Pratchett et al, 2011;Rodríguez-Zaragoza & Arias-González, 2015;Schmidt et al, 2012), we suspect that the remaining ~30% of the coral communities might have even higher particle deposition rates, rendering the presented estimates conservative. However, with progressing global change, ocean acidification and elevated temperatures will compromise coral calcification and increase bioerosion (Perry et al, 2018).…”

Unexplored Refugia with High Cover of Scleractinian Leptoseris spp. and Hydrocorals Stylaster flabelliformis at Lower Mesophotic Depths (75–100 m) on Lava Flows at Reunion Island (Southwestern Indian Ocean)

“…In addition, studies on some complex mesophotic habitats occurring on lava flows (e.g., structure, environmental conditions) are still missing for a complete understanding of MCEs' biodiversity [6]. In Reunion Island where a frequent volcanic activity is recorded at the southeastern part of the island, both species diversity and composition of coral assemblages on lava flows at shallow depths (0-30 m depth) are distinct from typical coral reef sites located on the western and southern coast of Reunion Island [7].…”

Artificial reef structures and coral transplantation as potential tools for enhancing locally-managed inshore reefs: a case study from Wasini Island, Kenya

“…The cover of Acropora corals increased over time from deployment, perhaps due to the high survival of transplanted corals and also the artificial reef substratum being rapidly colonized by coral recruits (Rinkevich, 2000, pers obs.). One explanation for this is that Acropora corals have been identified as an opportunistic genus with life history traits that allow for the quick colonization of newer substrates ( Jouval et al, 2020). In this study, coral cover and habitat complexity may have improved to attract more reef fish within a relatively short time period as the project used mainly fast-growing Acropora coral species (Rinkevich, 2000).…”