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Sainte Clotilde, France

Bollard S.,ARVAM | Pinault M.,PARETO Ecoconsult | Pinault M.,CNRS Insular Research Center and Environment Observatory | Quodi J.-P.,ARVAM | And 5 more authors.
Cahiers de Biologie Marine

Echinodernis from Reunion Island have been studied mostly from west coast reefs. A recent faunal inventory (BIOLAVE) was conducted on the underwater lava flows of Piton de La Fournaise and constitutes the first submarine survey on the south-east side of the island. The aim of the present study was to evaluate the species richness in the different echinoderm classes and assess their potential as indicator of the colonisation of lava with different ages. During 8 days, 9 sites with different habitats defined by depth and substrate homogeneity were explored using a stratified sampling. Description of echinoderms and comparison of the taxonomic composition between sites of different ages and depths were presented. 45 species of the 5 classes were identified, belonging to 23 families and 32 genera. Ophiuroid was the most diverse class (22 species), followed by echinoids (13 species), asteroids and holothuroids (6 species each), and crinoids (2 species). Species number increased with lava flow's age, except for echinoids, which showed a higher species number on recent sites, but ophiuroids only showed a significantly higher species number on the oldest sites. On the contrary, species number tended to decrease with depth, but echinoids only showed a significantly higher species number on shallow water. Some asteroid, echinoid and holothuroid species, such as Aquilonastra richmondi, Asthenosoma varium, Echinothrix spp., Echinometra mathaei and Euapta godeffroyi, were observed on the most recent sites only, while some ophiuroid species were observed in deeper sites only. These characteristic species could be seen as bioindicators of disturbed environment or have a distribution restricted to deeper areas. Source

Facon M.,Reef Check France | Facon M.,Agro ParisTech | Pinault M.,CNRS Insular Research Center and Environment Observatory | Obura D.,CORDIO East Africa | And 6 more authors.
Ecological Indicators

Coral reefs around the world are facing increasing disturbance; however, the ability to monitor them is constrained by cost and experience factors. The Line Intercept Transect (LIT) method is usually used with an expert level of identification (30 benthic categories and sometimes coral genera), but these are time-consuming, require a high level of expertise and are therefore expensive. Over the last 20 years, surveys performed by non-specialist volunteers have provided data for increasing numbers of reefs, using simplified sampling methods and more basic levels of identification. In between these extremes, new stakeholders (e.g. environmental assessment agencies, consultancy firms, marine nature reserves, etc.) requiring an intermediate level of expertise and resolution are now carrying out coral reef surveys. Across all levels, it is desirable to identify monitoring methods that optimize the data provided and the ease of implementation according to the users' needs. In this study on surveys from Réunion Island collected between 2003 and 2013, we used multivariate analyses to compare four increasing levels of identification using the LIT method. For each level, we studied the structure of the benthic community and its spatial (reef flat vs. outer slope) and temporal (before vs. after a cyclone) variation. The most basic level of identification showed differences between the reef flat and outer slope, but did not show a significant effect of the cyclone on the benthic community. The two highest levels of identification, both of which we rated 'expert', showed the highest differences in variation. The intermediate level of identification supplied the same information as the expert levels, but required less effort and was therefore less expensive. Next, we compared the LIT with the Point Intercept Transect (PIT) method. At a level of identification appropriate to the interval used, PIT supplied an almost equivalent level of information as LIT, while reducing the time spent underwater. Thus, when managing coastal areas or carrying out impact studies to monitor disturbance, it may be useful to (i) perform surveys with an intermediate level of identification, and (ii) using PIT rather LIT. © 2015 Elsevier Ltd. All rights reserved. Source

Chabanet P.,IRD Montpellier | Bigot L.,University of Reunion Island | Nicet J.-B.,PARETO Ecoconsult | Durville P.,Aquarium de la Reunion | And 5 more authors.
Acta Oecologica

Monitoring of coral reefs has become a major tool for understanding how they are changing, and for managing them in a context of increasing degradation of coastal ecosystems. The Global Coral Reef Monitoring Network (GCRMN) has near-global coverage, but there are few remote sites free of direct human impact that can serve as reference sites. This study provides baseline data for the French Iles Eparses in the Mozambique Channel, Western Indian Ocean (WIO), whose coral reefs are little known owing to their limited accessibility, and have been free from fishing pressure for over 20 years. Surveys of coral reef health and fish community structure were undertaken at four of the islands (Europa, Bassas da India, Juan de Nova and Glorieuses) in 2011-2013. Monitoring was conducted using standardized GCRMN methods for benthos and fish communities, at the highest taxonomic level. Benthic cover showed a latitudinal gradient, with higher coral cover and conversely lower algae cover (60% and 14% respectively) in the south of the Mozambique Channel. This could be due to the geomorphology of the islands, the latitudinal temperature gradient, and/or the history of chronic stress and bleaching events during the last decades. Fish also showed a latitudinal gradient with higher diversity in the north, in a center of diversity for the western Indian Ocean already recognized for corals. An exceptional biomass fish was recorded (approximately 3500 kg/ha excluding sharks, compared to a maximum of 1400 kg/ha elsewhere in the WIO). The presence of large predators and sharks in all the islands as well as the absence of fleshy benthic algae were indicators of the good health of the reef systems. Nevertheless, these islands are beginning to experience illegal fishing, particularly in the north of the Mozambique Channel, demonstrating their vulnerability to exploitation and the need to protect them as reference sites for coral reef studies, including of climate change impacts, for the region and globally. © 2015. Source

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