Influence of benthic organisms on coral recruitment
Creators: name: Zerambay, Sarah
name: Botosoamananto, Lebely Radonirina
name: Adjeroud, Mehdi
name: Todinanahary, Gildas
Publisher: name: Zenodo
Year: 2022
Subjects: coral reefs
scleractinian corals
recruitment
benthic organisms
Madagascar

description: Threats to the health of coral reef ecosystems by climate change and human activitiesnecessitate their management and conservation. However, the recovery of reefs depends on thereconstitution of coral populations, either by the regrowth of fragments of surviving corals, orby the recruitment of new individuals. In this context, the major aim of this study is to improveour knowledge on the mechanisms of coral recruitment and provide a rigorous database for thedevelopment of effective management and conservation measures. The data collection wascarried out in the region of Toliara, Southwestern Madagascar, between February 2020 andJanuary 2021, with a sampling frequency of once every four months. A total of 10 stations weresampled on the major reef habitats, with four stations on the outer slope, two on the inner slopeand four on patch reefs. At each station, 20 unglazed terracotta tiles (11 ´ 11 ´ 1 cm) weredisposed. Coral recruits were identified and recorded using a dissecting microscope. At thisstage of development, only three families (Acroporidae, Pocilloporidae, Poritidae) of coralrecruits can be reliably distinguished, and all other coral families were compiled into a categorynamed “other” recruits. We also used a category “broken” that comprised of all spats that weretoo damaged to be identified with certainty. The plates were photographed on all surfaces(lower, upper, and edges), analyzed with CPCe software for percentage coverage of benthicorganisms. Results showed a significant spatial variability in recruitment rates at the habitatlevels, with the highest mean annual recruitment at patch reefs (3.10 recruits per plate)compared to the outer slope (1.84 recruits per plate) and to the inner slope (1.17 recruits perplate). A peak in recruitment for all families was recorded in the period from October toJanuary. Over the duration of the study period, recruit assemblages were dominated byPocilloporidae (55.87%), followed by Acroporidae (29.02%), with much less abundance ofPoritidae (1.96%) and "other" recruits (10.65%). The remaining 2.50% is represented byunidentifiable broken recruits. The highest density of recruits was observed on the edges of theplates (1.87 recruits.plate-1) followed by the upper (1.81 recruits.plate-1) and lower (1.46recruits.plate-1) surfaces. Plates were mainly covered by encrusting calcareous algae (54%),encrusting organisms (22%), and macroalgae (4%), whereas 20% of the plates were notcolonized by living organisms. The density of coral recruits was positively correlated to thecover of encrusting organisms, such as Foraminifera, Bryozoa, and Annelids. In contrast, recruitdensity was negatively correlated to cover of encrusting calcareous algae and of macroalgae.This result may indicate a strong competition for space or an inhibition of coral settlement bysome algae. However, further studies are necessary to explore the mechanisms behind thesecorrelations.