Benthic foraminifera as bio-indicators of environmental quality ; Development of foraminiferal indices

Date du colloque : 06/2011International audienc

A non-destructive method to assess the status of Posidonia oceanica meadows

peer reviewedThis paper presents a new non-destructive sampling technique that consists of cutting all of the leaves of a Posidonia oceanica shoot (with scissors) just above the ligula of the external leaves. Developed in an undisturbed meadow in Corsica (France) at depths of 12–15 m, this sampling technique is called the Non-Destructive Shoot sampling Method (NDSM). The results of using this method indicate that most biometric parameters and relevant water quality indices can be measured and calculated from seagrasses sampled using the NDSM. It was determined that sampling shoots using the NDSM ensured a 100% survival rate. Notably, the NDSM allowed sampled shoots to grow back to lengths similar to those of an adjacent control meadow within three months. Biochemical analyses indicated that meadow portions and seagrass leaves regrown after NDSM sampling differed little in chemical composition (C, N and P and essential metal micronutrients Fe, Cu, Zn, Mn, Ni and Mo) to control seagrasses. Thus, the NDSM limits the negative effects of the sampling. Although not lethal to the plant, sampling seagrasses according to the NDSM requires exemption from the competent authority according to local, regional or national regulations for each protected species. © 2020 Elsevier LtdSTARECAPME

Valuation and sensitivity of socio-economic activities along the French mediterranean coast

The valuation of services linked to the coastal environment can provide useful information for decision-makers and, therefore, contribute to costal management strategies. By focussing on services in terms of uses, this case study particularly aims at evaluating the socio-economic activities along the French Mediterranean coast and the corresponding sensitivity to a major pollution event. The assessment comprises a large spectrum of coastal activities (market and non market) that are directly or indirectly linked to seawater quality. To estimate their values (monetary and nonmonetary), quantitative and semi-quantitative measures were used. These values, translated into indexes and presented in their geographical context, allow a socio-economic sensitivity mapping of the French Mediterranean coastal zones as a tool for spatial planning for decision-makers. The resulting maps help to identify and characterize coastal zones that are particularly sensitive to anthropogenic impacts such as marine pollution

Experimental transplantation of Posidonia oceanica

peer reviewedThe project of extension at sea of Monaco required the realization of important environmental measures to protect the marine environment. Among differents actions was included a significant experimental measure of transplantation of nearly 500 m2 of Posidonia oceanica located in the project area. To reach this objective we have developed and implemented the SafeBent protocol. The SafeBent protocol allows to sample clods of seagrasses (0.8 m2/60 cm thick) with a marinized transplanter (Model Optimal 880) operated with a very long arm shovel (27 m) from a jackup. The main advantages of this method are:-high transplantation rate (up to 32 m2/jour);-conservation of the structure of the seagrasses in meadows;- conservation of the sediment;-easy transport of clods in specially manufactured metal baskets The transplantation was carried out between 20 March and 15 May 2017. Seagrasses were reimplanted in the ground of the AMP of Larvotto (384 m2) and on the berm of the dam along the port of Fontvieille in specially constructed concrete planters (116 m2). The present communication aims to present the Safebent method and the results obtained to date

Fine-scale automatic mapping of living Posidonia oceanica seagrass beds with underwater photogrammetry

International audienceThe Mediterranean seagrass Posidonia oceanica, which provides highly valuable ecosystem services, is subject to increasing anthropogenic pressures, causing habitat loss or fragmentation. Whilst airborne images and acoustic data can be used for monitoring seagrass coverage at a macro-scale and over long time periods, monitoring its health in the short term requires precision mapping in order to assess current regression/progression of individual meadows. However, current fine-scale underwater techniques in the field are imprecise and time-demanding. We propose an automatic classification approach based on underwater photogrammetry for an operational, cost- and time-effective fine-scale monitoring method. The method uses a property of the sparse cloud generated during bundle adjustment-the reconstruction uncertainty-to map seagrass patches. The mean precision, recall and Fl score of the method over 21 study sites with different morphologies were 0.79, 0.91 and 0.84, respectively. However, the fragmentation level of the meadows had a significant negative effect on classification performances. The temporal monitoring of 3 sites using this method proved its operability and showed a positive evolution index of the corresponding meadows over a period of 3 yr. This method is generalizable for most encountered configurations and can be integrated in a large monitoring system, as it enables the production of numerous seagrass maps over a short period of time. Moreover, our methodology could be generalized and applied in the study of other submerged aquatic vegetation by adjusting the method's parameters

The impact of 85 years of coastal development on shallow seagrass beds (Posidonia oceanica L. (Delile)) in South Eastern France: A slow but steady loss without recovery

International audienceThe impact of 85 years of coastal development on shallow seagrass beds (Posidonia oceanica L. (Delile)) in South Eastern France: a slow but steady loss without recovery Abstract: Shallow Posidonia oceanica beds (0 to-15 m), the most common seagrass in the Mediterranean, were mapped from aerial pictures dating from the 1920's and from 2012 along 800 km of coastline in SouthEastern France (Provence-Alpes-Côte-d'Azur region). Changes in P. oceanica beds spatial distribution (limits and areal extents) during these 85 years were analyzed in terms of concordance (remaining areas), positive discordance (expanding areas) or negative discordance (lost areas). Lost areas were linked with direct or indirect impacts of coastal development (artificialized coastlines (namely harbours, ports of refuge, landfills, artificial beaches, groynes and pontoons, submarine pipelines and aquatic farms) visible on the pictures. The comparison showed that 73 % of the shallow limits have declined. Considering areal extents, remaining seagrass meadows areas accounted for the major part (85 %), while lost areas accounted for 13 % and expanding areas for 1.1%. Lost areas were mainly linked with artificialized coastlines but 44 % remained with undetermined causes (invisible pressures and/or mixed effects). The analysis of 96 coastal facilities participating to the artificialized (namely man-made) coastlines showed that the highest impact over the longest distance (5 km) was caused by harbours. Only artificial beaches had such a distant impact. Pontoons were the least surrounded by lost seagrass meadows areas. These quantitative data offer important information for marine conservation

Mapping the diversity of spectral shapes discriminates between adjacent benthic biophonies

International audienceCoastal soundscapes are dominated by broadband transient sounds primarily emitted by benthic invertebrates. These sounds are characterized by a very large dynamic of amplitude. The loudest ones propagate further and interfere with the detectability of benthic sounds by invading other more distant habitats. Acoustic diversity assessment is therefore biased when applying acoustic indices related to the signal's power. Here, we propose new acoustic indices (IDSS: indices of the diversity of spectral shape) capable of extracting the diversity of the benthic invertebrate biophony (BIB) despite interference from loud and abundant sounds. A passive acoustic ecological survey was conducted in a shallow Mediterranean bay with a small-scale mosaic of biocenosis. The sound pressure level and spectrum of the BIB revealed that the rocky fringe had the most powerful biophony, propagating up to 3680 m, thus 'invading' other habitats. However, these power-based indices failed to depict BIB diversity. The IDSS allowed us to discriminate BIB diversity despite the interfering rocky fringe biophony, including low-power sounds not depicted by traditional power-based methods. Four main categories of benthic invertebrates sounds (BIS) spectra were found. Two categories (high-power, peak frequencies ~3 to 4 kHz) were mainly linked to the rocky fringe. Their contribution to the diversity (56%) decreased with increasing distance to the fringe, where low-power BIS (peak frequencies above 15 kHz) predominantly contributed to the BIB (42%) and may be specific to coralligenous reefs. The IDSS enables a better characterization and quantification of BIB diversity and soundscape structure with a fine spatial resolution (~200 m)

Cartographie simultanée des ressources halieutiques et des habitats marins avec un sondeur multifaisceaux

International audienc

Potential use of marinas as nursery grounds by rocky fishes: insights from four Diplodus species in the Mediterranean

International audienceThe construction of marinas along the shoreline has caused substantial habitat destruction within the sheltered coastal areas previously used as nursery grounds by many fish species. However, although the negative ecological impacts of these constructions have been reported extensively, their potential roles in the functioning of the coastal zone remain largely unknown. Here, we surveyed the juveniles of 4 Diplodus species in 5 marinas located along the French Mediterranean coast to assess whether rocky fishes can successfully settle inside these artificialized coastal areas. Inter-specific differences in the spatiotemporal use of the various artificial habitats provided by marinas were investigated between April and August over 2 consecutive years. We also tested the potential benefit of pegging additional artificial habitats (Biohuts) on docks and pontoons to increase their value as fish nursery grounds. Our results suggest that although variations in marina and artificial habitat preferences exist between species, Diplodus juveniles repeatedly colonize marinas. Their average abundances on added Biohut habitats were twice as high as on nearby bare surfaces. This suggests that increasing the complexity of the vertical structures of marinas can considerably enhance their suitability for juvenile rocky fishes, especially at the youngest stages, when mortality is highest. Therefore, as long as marina water quality is well controlled, ecological engineering within these man-made habitats might reduce the ecological consequences of urban development by providing suitable alternative artificial nursery grounds for rocky fishes