Effect of depth and canopy height on the nursery value of Cystoseira balearica forests for Mediterranean rocky reef fishes

We studied effects of depth and Cystoseira balearica forests canopy height on coastal juvenile fish assemblages of Minorca Island. Results showed a clear differentiation of juvenile fish assemblages due to depth: assemblage in the shallowest range (3-4m) was characterized by higher densities of Thalassoma pavo, deeper ones (6-8, 10-12 m) by higher densities of Coris julis. Smallest juveniles of both species were more abundant within forests displaying the highest canopy height; meanwhile largest juveniles were more abundant within low Cystoseira forests. Also, both species showed predominantly a cryptic behavior on forest of higher canopy height, and a temporal one when canopy was lower. This study supports the importance of preserving healthy Cystoseira forests in order to preserve their nursery value for these two Labrid species0,000

Photogrammetric surveys and geometric processes to analyse and monitor red coral colonies

This article describes the set of photogrammetric tools developed for the monitoring of Mediterranean red coral Corallium rubrum populations. The description encompasses the full processing chain: from the image acquisition to the information extraction and data interpretation. The methods applied take advantage of existing tools and new, innovative and specific developments in order to acquire data on relevant ecological information concerning the structure and functioning of a red coral population. The tools presented here are based on: (i) automatic orientation using coded quadrats; (ii) use of non-photorealistic rendering (NPR) and 3D skeletonization techniques; (iii) computation of distances between colonies from a same site; and (iv) the use of a plenoptic approach in an underwater environment. © 2018 by the authors.This work is partially done in the framework of the PERfECT project, funded by the Foundation TOTAL, project 2014/257. The plenoptic camera was bought in the frame of the DGA RAPID LORI project (LOcalisation et Reconnaissance d’objets Immergés

Marine Protected Areas and the conservation of long-lived marine invertebrates: the Mediterranean red coral

11 pages, 4 figures, 2 tablesIntensive harvesting has caused important shifts in the size structure of the Mediterranean red coral Corallium rubrum, and continues to hinder the total recovery of exploited populations. Marine Protected Areas (MPAs) offer an excellent opportunity to observe their recovery in the absence of fishing pressures. In this study, we analysed the demographic structure of red coral populations from 3 of the oldest Mediterranean MPAs. The population structures at the beginning of each reserve and after 30 yr of similar management efforts were also forecasted. The 3 MPAs displayed higher size values than those reported for most of the shallow populations and deep-dwelling populations. Differences in the observed size distributions were more closely related to the structure at the beginning of the reserve than to the number of years of protection. The estimated future size distributions showed a significant increase in large colonies; however, the maximum values predicted are far from those measured in pristine populations. Comparisons of harvested and protected populations using different parameters allowed us to identify the percentages of colonies with basal diameter greater than 7 mm or colony height greater than 100 mm as the most useful descriptors for evaluating the conservation status of each population. The vulnerability of long-lived marine invertebrates to disturbances is due to their slow population dynamics, hence the importance of active management within MPAs to promote delayed but long-term positive effects on these species. This study provides helpful information for the evaluation of the effectiveness of management measures for coral populationsC.L. was funded by a postdoctoral fellowship from the ‘Ministerio de Ciencia e Innovación’ of Spain. This study was funded by the Agence Nationale de la Recherche (Medchange project)Peer Reviewe

Fine-scale genetic structure and inferences on population biology in the threatened Mediterranean red coral, Corallium rubrum

13 pages, 3 figures, 3 tablesIdentifying microevolutionary processes acting in populations of marine species with larval dispersal is a challenging but crucial task because of its conservation implications. In this context, recent improvements in the study of spatial genetic structure (SGS) are particularly promising because they allow accurate insights into the demographic and evolutionary processes at stake. Using an exhaustive sampling and a combination of image processing and population genetics, we highlighted significant SGS between colonies of Corallium rubrum over an area of half a square metre, which sheds light on a number of aspects of its population biology. Based on this SGS, we found the mean dispersal range within sites to be between 22.6 and 32.1 cm, suggesting that the surveyed area approximately corresponded to a breeding unit. We then conducted a kinship analysis, which revealed a complex half-sib family structure and allowed us to quantify the level of self-recruitment and to characterize aspects of the mating system of this species. Furthermore, significant temporal variations in allele frequencies were observed, suggesting low genetic drift. These results have important conservation implications for the red coral and further our understanding of the microevolutionary processes acting within populations of sessile marine species with a larval phaseThis study was funded by the ‘‘Provence–Alpes–Coˆ te d’Azur’’ region (J-B. Ledoux Doctoral Fellowship) and by the IFB Foundation (Institut Franc¸ais de la Biodiversite´), the environmental department of TOTAL-FINA-ELF group, an ‘Action Concerte´e Initiative’ (ACI) program ‘Jeunes chercheurs 2003¢ (number JC5360) from the French Research Ministry and the MEDCHANGE project funded by the Agence Nationale pour la Recherche (ANR)Peer Reviewe

Photogrammetric Surveys and Geometric Processes to Analyse and Monitor Red Coral Colonies

25 pages, 18 figures, 1 tableThis article describes the set of photogrammetric tools developed for the monitoring of Mediterranean red coral Corallium rubrum populations. The description encompasses the full processing chain: from the image acquisition to the information extraction and data interpretation. The methods applied take advantage of existing tools and new, innovative and specific developments in order to acquire data on relevant ecological information concerning the structure and functioning of a red coral population. The tools presented here are based on: (i) automatic orientation using coded quadrats; (ii) use of non-photorealistic rendering (NPR) and 3D skeletonization techniques; (iii) computation of distances between colonies from a same site; and (iv) the use of a plenoptic approach in an underwater environment.This work is partially done in the framework of the PERfECT project, funded by the Foundation TOTAL, project 2014/257. The plenoptic camera was bought in the frame of the DGA RAPID LORI project (LOcalisation et Reconnaissance d’objets Immergés

Characterizing Corallium rubrum populations of two Mediterranean MPAS: structuring factors and dynamics

2nd Mediterranean Symposium on the Conservation of Coralligenous and other Calcareous Bio-Concretions, 29-30 October 2014, Portorož, Slovenia.-- 2 pages, 2 figuresPeer Reviewe

AUTOMATING THE MEASUREMENT OF RED CORAL IN SITU USING UNDERWATER PHOTOGRAMMETRY AND CODED TARGETS

A photogrammetry tool dedicated to the monitoring of red coral populations in situ has been developed by LSIS in Marseille (France). This tool is used to collect in an efficient and precise manner key data for the study of the population dynamics of red coral. In selected red coral populations, scuba-divers obtain a series of photographs from the permanent plots (about 2 m2) on an annual basis. To facilitate the photographic sampling and measurements, the scuba-divers use a 20 x 20 cm quadrat to cover the permanent plots. The analysis of the photographs provides reliable measurements on colony sizes (basal diameter and maximum height), occurrence of breakage of colonies and the occurrence of necrosis. To minimize the divers' tasks during the acquisition phase, we opted for stereoscopic acquisition using a single device to easily adapt the measurement procedure to the scene configuration. The material is quite light, one camera and two electronic strobes and a simple procedure with two photographs taken for each site. To facilitate the measurement phase of colony sizes; the exploitation of photographs consists of four key steps: orientation, scaling, measurement of the characteristic points of coral colonies and result validation (checking measurement consistency to detect possible errors in measurement or interpretation). Since the context of the shooting can vary widely, dominant colors, contrast, etc. may often change. In order to have a stable and common reference in all photographs independently of the site, we decided to always include a quadrat in the scene which then will be used for the orientation and scaling phases. The automation of orientation and the lack of constraints to adapt the analytical technique to the features of each site offer the possibility to multiply field surveys and to measure hundreds of quadrats from several different populations in a very efficient manner. The measurement results are exported into a spreadsheet application and integrated into the biologists' workflow. The results obtained from different red coral populations displaying contrasting characteristics (small versus large colony sizes) are presented and discussed at the end of this article

Challenging issues for the study of the mesophotic ecosystems by environmental DNA metabarcoding (talk)

European Conference on Scientific Diving, Roscoff, FRA, 14-/05/2023 - 18/05/202

Population collapse of habitat-forming species in the Mediterranean: a long-term study of gorgonian populations affected by recurrent marine heatwaves

Understanding the resilience of temperate reefs to climate change requires exploring the recovery capacity of their habitat-forming species from recurrent marine heatwaves (MHWs). Here, we show that, in a Mediterranean highly enforced marine protected area established more than 40 years ago, habitat-forming octocoral populations that were first affected by a severe MHW in 2003 have not recovered after 15 years. Contrarily, they have followed collapse trajectories that have brought them to the brink of local ecological extinction. Since 2003, impacted populations of the red gorgonian Paramuricea clavata (Risso, 1826) and the red coral Corallium rubrum (Linnaeus, 1758) have followed different trends in terms of size structure, but a similar progressive reduction in density and biomass. Concurrently, recurrent MHWs were observed in the area during the 2003–2018 study period, which may have hindered populations recovery. The studied octocorals play a unique habitat-forming role in the coralligenous assemblages (i.e. reefs endemic to the Mediterranean Sea home to approximately 10% of its species). Therefore, our results underpin the great risk that recurrent MHWs pose for the long-term integrity and functioning of these emblematic temperate reefs