A threefold perspective on the role of a pockmark in benthic faunal communities and biodiversity patterns

Pockmarks are circular-shaped depressions that increase seabed heterogeneity and are characterized by discontinuous fluid emissions. To understand how environmental conditions of pockmarks affect the structure of macroand meiofauna, we investigated two sites in a pockmark field in the northwestern Madagascar margin. In a comparative approach, we explored the community structure of the dominant taxa (Polychaeta, Nematoda and hyaline foraminifera) in each component (macro-, metazoan meiofauna and foraminifera, respectively). The investigated active pockmark showed approximately two times higher meiofauna abundance compared to in a site away from another pockmark field, but macrofauna showed the opposite trend, with almost half density at the pockmark site. However, at both sites, macroand meiofauna showed higher richness and abundance values in the top well-oxygenated layers of the sediment than in the underlaying ones. Polychaeta and Nematoda showed lower richness in the pockmark, opposed to hyaline foraminiferans, but lower evenness in the pockmark was found for the three groups. The detection of gas flares in the water column attests of the recent activity within the pockmark. High amount of sulfur-bearing minerals (mainly pyrite) evidences a production of dissolved free sulfides (not detected at the time of sampling) by sulfate reduction process driven by organic matter degradation and anaerobic oxidation of methane. Furthermore, recent increase in sedimentation rates in the past 70 years and organic matter inputs could have led to higher organic matter degradation rates resulting in reduced conditions and a high oxygen consumption. All this together seem to act as key factors in the determination of variation in richness, abundance and community composition of macrofauna and meiofauna. Additionally, some taxa seem to be more tolerant to these extreme conditions, such as species belonging to the Nematoda genus Desmodora and the phylum Kinorhyncha, which are highly abundant in the pockmark, and hence, may be considered as potential bioindicators of pockmark activity in this area. Further studies are required for a better assessment

Coral recruitment in the Toliara region of southwest Madagascar: Spatio‐temporal variability and implications for reef conservation

Investigating coral recruitment is critical to better understand replenishment and resilience capacities of coral reef ecosystems and to improve their conservation. Here, we examined the spatio‐temporal patterns of coral recruitment and the influence of confamilial adult coral cover in the region of Toliara, southwest Madagascar. Terracotta tiles were immersed from October to late January over a 3‐year period (2018–2021) at 10 stations located on major reef habitats. Overall recruitment rates were relatively high compared to those of other reefs in the Southwestern Indian Ocean, ranging from 219.20 recruits.m−2 in 2018–2019 to 156.30 recruits.m−2 in 2020–2021. Recruit assemblages were dominated by Acroporidae (45.5%) and Pocilloporidae (45.0%), whereas Poritidae (1.9%) and “other” recruits (3.6%) were rarely recorded. Recruitment patterns varied among stations and habitats, with higher rates in patch reef (187.06 recruits.m−2) and outer slope stations (156.99 recruits.m−2) compared to inner slope stations (108.04 recruits.m−2). With the exception of “other” recruits, recruitment rates decreased between 2018 and 2019 and 2019 and 2020, followed by an increase in 2020–2021 that reached or even exceeded initial values at some stations. The abundance of Pocilloporidae recruits was positively correlated with the cover of confamilial adult corals, highlighting potential stock–recruitment or recruitment–limitation relationships, or an aggregative settlement of young stages near the established adult colonies, whereas no such relationships were recorded for other coral family categories. This study identified sites on the outer slope and patch reefs to consider prioritizing for protection as recruitment hotspots, as well as degraded inner slope sites that could benefit from restoration, with the important caveat that any measures should be accompanied by alternative income‐generating activities through local involvement that suits the Malagasy context, such as locally marine managed areas

Coral recruitment in the Toliara region of southwest Madagascar: Spatio‐temporal variability and implications for reef conservation

International audienceInvestigating coral recruitment is critical to better understand replenishment and resilience capacities of coral reef ecosystems and to improve their conservation. Here, we examined the spatio‐temporal patterns of coral recruitment and the influence of confamilial adult coral cover in the region of Toliara, southwest Madagascar. Terracotta tiles were immersed from October to late January over a 3‐year period (2018–2021) at 10 stations located on major reef habitats. Overall recruitment rates were relatively high compared to those of other reefs in the Southwestern Indian Ocean, ranging from 219.20 recruits.m −2 in 2018–2019 to 156.30 recruits.m −2 in 2020–2021. Recruit assemblages were dominated by Acroporidae (45.5%) and Pocilloporidae (45.0%), whereas Poritidae (1.9%) and “other” recruits (3.6%) were rarely recorded. Recruitment patterns varied among stations and habitats, with higher rates in patch reef (187.06 recruits.m −2 ) and outer slope stations (156.99 recruits.m −2 ) compared to inner slope stations (108.04 recruits.m −2 ). With the exception of “other” recruits, recruitment rates decreased between 2018 and 2019 and 2019 and 2020, followed by an increase in 2020–2021 that reached or even exceeded initial values at some stations. The abundance of Pocilloporidae recruits was positively correlated with the cover of confamilial adult corals, highlighting potential stock–recruitment or recruitment–limitation relationships, or an aggregative settlement of young stages near the established adult colonies, whereas no such relationships were recorded for other coral family categories. This study identified sites on the outer slope and patch reefs to consider prioritizing for protection as recruitment hotspots, as well as degraded inner slope sites that could benefit from restoration, with the important caveat that any measures should be accompanied by alternative income‐generating activities through local involvement that suits the Malagasy context, such as locally marine managed areas

L’interdisciplinarité en pratique : retour d’expérience de la deuxième école d’été australe sur la vulnérabilité du patrimoine récifal (EEA VulPaRe 2016)

International audienceIn November 2016, the Second Austral Summer School “Vulnerability of coral reefs heritage” (EEA VulPaRe 2016) took place at Toliara (Madagascar). The school was funded and organised by IRD (French Research Institute for Development) and IHSM (Institute of Halieutics and Marine Science, University of Toliara), and proposed an interdisciplinary approach to the study of coral reefs. Environmental issues, different types of knowledge and valorisation of coral reefs were addressed by means of lectures, seminars, discussions and fieldwork. In this paper, the participants of EEA VulPaRe 2016 provide a critical feedback on this original interdisciplinary research training.En novembre 2016, s’est tenue à Toliara, dans le sud-ouest de Madagascar, la deuxième école d’été australe sur la vulnérabilité du patrimoine récifal (EEA VulPaRe). Coorganisée par l’IRD (Institut de recherche pour le développement, France) et l’IHSM (Institut halieutique et des sciences marines de l’Université de Toliara, Madagascar), cette formation a proposé une approche interdisciplinaire de la thématique des récifs coralliens. Elle a été dispensée sous la forme de cours magistraux, de pratiques de terrain et de débats portant sur les questions environnementales, de connaissance, de valorisation et de conservation de ces milieux. Les participants de l’EEA VulPaRe 2016 souhaitent, à travers le présent article, donner à la communauté scientifique un retour d’expérience critique sur une démarche originale de formation à la recherche interdisciplinaire

Practicing interdisciplinarity: a review of the Second Austral Summer School on vulnerability of coral reefs heritage (EEA VulPaRe 2016)

In November 2016, the Second Austral Summer School “Vulnerability of coral reefs heritage” (EEA VulPaRe 2016) took place at Toliara (Madagascar). The school was funded and organised by IRD (French Research Institute for Development) and IHSM (Institute of Halieutics and Marine Science, University of Toliara), and proposed an interdisciplinary approach to the study of coral reefs. Environmental issues, different types of knowledge and valorisation of coral reefs were addressed by means of lectures, seminars, discussions and fieldwork. In this paper, the participants of EEA VulPaRe 2016 provide a critical feedback on this original interdisciplinary research training.En novembre 2016, s’est tenue à Toliara, dans le sud-ouest de Madagascar, la deuxième école d’été australe sur la vulnérabilité du patrimoine récifal (EEA VulPaRe). Coorganisée par l’IRD (Institut de recherche pour le développement, France) et l’IHSM (Institut halieutique et des sciences marines de l’Université de Toliara, Madagascar), cette formation a proposé une approche interdisciplinaire de la thématique des récifs coralliens. Elle a été dispensée sous la forme de cours magistraux, de pratiques de terrain et de débats portant sur les questions environnementales, de connaissance, de valorisation et de conservation de ces milieux. Les participants de l’EEA VulPaRe 2016 souhaitent, à travers le présent article, donner à la communauté scientifique un retour d’expérience critique sur une démarche originale de formation à la recherche interdisciplinaire