Analyse de recrutement benthique sur les plaques d’ARMS calcaires via CPCe dans la baie de Ranobe, Sud-Ouest de Madagascar.

Abstract

ARMS (Autonomous Reef Monitoring Structures), colonized by a multitude of
marine organisms, constitute valuable tools for assessing the health and biodiversity of coral
reefs as well as for restoring these ecosystems. The ARMS Restore project, in collaboration
with Harvard University, the NGO Reef Doctor, and IH.SM, aims to develop these new devices
for Madagascar to improve the nutritional health of the inhabitants while conserving the
currently degraded coral reefs. As part of this project, a study focusing on benthic colonization
at five geomorphologically different stations in Ranobe Bay was conducted in September 2023,
allowing for a comparison of benthic colonization considering environmental parameters
(temperature and sedimentation rate). Each site comprises 3 ARMS, and deployment was
carried out for 13 days after 17 months of immersion. The surfaces of the plates constituting
the ARMS were photographed and analyzed using CPCe software to allow for a comparison
of benthic colonization between the study stations. The organisms recorded include 64 genera
grouped into 45 families and belong to the following groups: encrusting calcareous algae,
macroalgae, bryozoans, annelids, ascidians, bivalves, sponges, scleractinian corals, soft corals,
hydrozoans, gastropods, and echinoderms. The results show that benthic colonization varies
according to the stations and the surfaces of the plates. Some species are dominant on the upper
surfaces of the plates, others on the lower faces, and others on the edges. Environmental
parameters influence the distribution of benthic organisms.