Reef benthos of Seychelles - A field guide

Abstract

During the 2019 First Descent: Seychelles Expedition, shallow and deep reef ecosystems of the Seychelles Outer Islands were studied by deploying a variety of underwater technologies to survey their benthic flora and fauna. Submersibles, remotely operated vehicles (ROVs) and SCUBA diving teams used stereo-video camera systems to record benthic communities during transect surveys conducted at 10 m, 30 m, 60 m, 120 m, 250 m and 350 m depths. In total, ~ 45 h of video footage was collected during benthic transect surveys, which was subsequently processed using annotation software in order to assess reef biodiversity and community composition. Here, we present a photographic guide for the visual identification of the marine macrophytes, corals, sponges and other common invertebrates that inhabit Seychelles’ reefs. It is hoped that the resulting guide will aid marine biologists, conservationists, managers, divers and naturalists with the coarse identification of organisms as seen in underwater footage or live in the field. A total of 184 morphotypes (= morphologically similar individuals) were identified belonging to Octocorallia (47), Porifera (35), Scleractinia (32), Asteroidea (19), Echinoidea (10), Actiniaria (9), Chlorophyta (8), Antipatharia (6), Hydrozoa (6), Holothuroidea (5), Mollusca (2), Rhodophyta (2), Tracheophyta (2), Annelida (1), Crinoidea (1), Ctenophora (1), Ochrophyta (1) and Zoantharia (1). Out of these, we identified one to phylum level, eight to class, 14 to order, 27 to family, 110 to genus and 24 to species. This represents the first attempt to catalogue the benthic diversity from shallow reefs and up to 350 m depth in Seychelles.

Light and temperature drive the distribution of mesophotic benthic communities in the Central Indian Ocean

“…and Oxypora sp. individuals were also observed at shallow and mesophotic depths, as reported in several studies worldwide (Fassbender & Stefanoudis, 2021;Pérez-Rosales et al, 2021;Sinniger et al, 2022).…”

Stakeholder‐derived recommendations and actions to support deep‐reef conservation in the Western Indian Ocean

“…This leads to limited deep‐reef awareness and appreciation among stakeholders and the public (Appendix S4), resulting in very few deep reefs being included in MPAs (UNEP‐Nairobi Convention & WIOMSA, 2021). Consequently, there is a need for basic deep‐reef research throughout the WIO to establish baseline information (e.g., species lists, Fassbender et al., 2021; habitat classifications, Osuka et al., 2021) (Recommendation 4; Action 7). More applied research avenues, such as focusing on deep‐reef ecosystems functioning and their links to shallow reefs (Stefanoudis et al., 2020), or defining ecosystem services provided (Holstein et al., 2019) and their monetary value (e.g., Armstrong et al., 2012), will help reach a broader audience outside academia.…”

An underwater imagery identification guide for shallow, mesophotic and deep-sea benthos in Maldives

“…As such, it will be of great assistance to marine professionals observing these organisms in their natural habitat during fieldwork and to researchers annotating imagery-based datasets. Similar efforts for the Indian Ocean include field identification guides for Seychelles ( Fassbender et al 2021 ), Chagos ( Diaz et al 2023b ) and Comoros (in prep.).…”

“…Given that some morphological features required for positive taxonomic identification are not visible through imagery alone and often require further ex-situ examination, assigning observed organisms to species level is not always possible. In fact, it is common practice to place observed organisms into ‘morphotypes’ or ‘morphospecies’ that are morphologically similar organisms that could represent a species, genus or higher-level classification ( Howell et al 2019 , Fassbender et al 2021 ).…”

“…To allow for inter-comparability of Indian Ocean benthic communities between locations, we use the same morphotype names for shared morphotypes found in the Seychelles ( Fassbender et al 2021 ) and Maldives.…”