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With five currently recognized species that form several secondary contact zones, slow worms (Anguidae: Anguis) offer a valuable model to study the fate of evolutionary lineages in the face of hybridization and genetic introgression. The relationships between the Western Slow Worm Anguis fragilis and the Italian Slow Worm Anguis veronensis are particularly puzzling. Their respective distributions remain poorly known on the edges of their parapatric ranges, as both species lack external differentiation. Contra earlier mitochondrial phylogenies, new phylogenomic inferences have shown that A. fragilis and A. veronensis are sister taxa, thus casting doubts on their specific status. In this study, we analyze the A. fragilis/veronensis transition in southeastern France, based on one mitochondrial (ND2) and two nuclear (PRLR and HA1) genetic markers in 81 specimens from 61 localities. The ranges of A. fragilis and A. veronensis roughly extends northwest and southeast of the Rhône-Durance valleys, respectively, with clear signs of introgressive hybridization in the areas of contact (notably the eastern parts of the lower Rhône valley). Based on the three molecular markers analyzed, gene flow does not seem to reach outside the narrow hybrid zone, which likely indicates (incomplete) intrinsic reproductive isolation. Hence, we provisionally suggest maintaining A. veronensis as a separate species from A. fragilis. More generally, patterns of genetic divergence, external differentiation, and hybridization (both historical and contemporary) in Anguis ssp. supports a speciation continuum spanning from cryptic, genetically compatible alloparapatric lineages to phenotypically distinct, deeply diverged and fully reproductively isolated taxa able to coexist in sympatry.

Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.

The processes underlying macroecological gradients in body size are widely debated, in part because their intraspecific variability remains poorly described even in well-studied taxa such as vertebrates. In this study, we investigated how climate, habitat, genetic lineage and sex explain body size variations in French populations of the European pond turtle (Emys orbicularis). We measured 7016 adult individuals captured in 41 populations, covering most of the species’ distribution in metropolitan France, including Corsica. Body size variation in our sample was wide and comparable to that found across the species’ worldwide range. Variation was similar in magnitude at regional and local levels, suggesting that body size is influenced by local factors as much as by regional factors such as climate or genetic lineage. Smaller sizes were associated with Mediterranean or altered oceanic climates, and with two lineages (E. o. galloitalica and E. o. galloitalica/E. o. orbicularis), while larger sizes were associated with northern environments and the orbicularis lineage. Body size variations recorded at local level reflect an adaptive response to environmental constraints, suggesting that habitat is also an important factor in understanding size variation.

Periphytic diatoms growing on aquatic turtle carapaces provide an interesting example of biofouling on an animal substrate. This study dealt with the question of the specificity of epizoic diatom communities for the case of the European pond turtle (Emys orbicularis) and across five water bodies in South-Eastern France. 375 diatom taxa have been identified on the European pond turtle carapace. The results showed that the epizoic communities of the five sites were significantly different from each other. The epizoic diatom communities could be clearly distinguished from epilithic and epiphytic communities only in two out of five sites. The differences in composition at the two sites resulted from the greater abundance of some species and life forms. However, the characteristic pattern of diatom communities on the carapaces was not the same at the two sites. It therefore appeared that the European pond turtle’s carapace did not harbour specific diatom communities and can rather be considered a neutral substrate.

Many banned persistent organic pollutants (POPs) remain for decades in the aquatic environment and can have harmful effects on long-lived predators because of their high bioaccumulation and biomagnification potentials. We investigated the occurrence and levels of 18 polychlorinated biphenyls (PCBs) and 16 organochlorine pesticides in European pond turtles (n = 174) from April to July 2018 in the Camargue wetland, France. Although the Camargue was highly contaminated in previous decades, plasma occurrence and levels of POPs were very low: we were able to quantify only 3 of the 34 compounds we analyzed in >10% of the turtles. The burdens from POPs did not differ between males and females and were uncorrelated with sampling date and body mass. We observed differences in POP burdens between turtles from the 2 sampling sites. One possible explanation is that the sampling sites were in different agricultural hydraulic systems: plasma occurrence and levels were higher for PCB-52 and hexachlorobenzene in turtles captured in drainage channels and for PCB-153 at the site that receives irrigation. Finally, the occurrence and levels of PCB-153 in turtles increased with age, likely because of bioaccumulation and much higher exposure 20 to 30 yr ago than now. Environ Toxicol Chem 2021;40:2261-2268. © 2021 SETAC.

The Spur-thighed tortoise (Testudo graeca) is listed as vulnerable on the IUCN Red List, with small and fragmented populations located around the Mediterranean basin. In Turkey, this species has remained poorly studied which hampers solid assessment of threats and conservation measures. We studied the spatial distribution, habitat use, and demography of the species in the Gediz Delta (Aegean coast of Turkey) between 2015 and 2017 with a specific capture-mark-recapture survey made in the Sazligol marshes. A total of 114 individuals (20 juveniles, 62 males and 32 females) were captured and released in that period. Carapace length of adult females was on average higher (205.2 +/- 3.2 mm) than in adult males (190.9 +/- 2.3 mm). Sex ratio was biased with 1.94 males per female. Based on the capture-recapture histories of 65 individuals (3 juveniles, 37 males and 25 females) marked in 2015, we estimated the population size of the Sazligol marsh population to be 137 +/- 23 individuals, which corresponds to a density of 5.7 individuals per ha. The main threats detected were agricultural activities, urbanisation and captures for the pet trade., Doga Dernegi; Tour du Valat, Ege University Scientific Research Fund (Ege Universitesi Bilimsel Arastirmalar Fonu) [2017/FEN/041]; PACA Regional Council; MAVA Foundation, This study is part of a project supported by Doga Dernegi and the Tour du Valat, Ege University Scientific Research Fund (Ege Universitesi Bilimsel Arastirmalar Fonu) [Grant No: 2017/FEN/041]. Legal authorization for the study was provided by the Turkish National Parks Authority (Research permit No: 72784983-488.04-41632) and ethical permission was provided from Ege University. We are grateful to these organizations, the PACA Regional Council and the MAVA Foundation for their generous financial support.

International audience; Benthic diatoms are widely used as bio-indicators in water quality monitoring of rivers and streams, but less commonly in lentic waterbodies such as pools and lakes. Currently, a new method for assessing the ecological status of lakes is being tested in France to meet the requirements of the European Water Framework Directive (WFD) 2000/60/EC. This new method uses epilithic and epiphytic diatoms growing on stones and aquatic plants. Alternatively, freshwater turtles and the epizoic algae found on their carapaces may provide an excellent substrate for estimating water quality. Our study proposes an original diatom-based method for assessing the quality of water bodies in which turtles live. The main objective was to compare the Biological Diatom Index (BDI) values measured from epizoic diatom samples taken on the carapace of turtles with classical epilithic or epiphytic samples. Epizoic samples were taken from the carapaces of the turtle Emys orbicularis in two shallow French Mediterranean wetlands. Our results indicate that diatom assemblages differ slightly within the three substrates studied with limited variations in index value. However, some variability among epizoic samples from the same site suggests that several turtle individuals should be sampled for water quality biomonitoring.

International audience; Proper delineation of flyways is a prerequisite for adequate management of migratory birds. The implementation of coordinated international management for greylag goose (Anser anser) is currently underway in Europe for the north-west/south-west (NW/ SW) population. Some uncertainty remained as to whether greylags wintering in Camargue, Southern France, belonged to this population and bred in Norway, Sweden and Finland,or rather originated from the Central European population, especially since most neck collar observations were of birds ringed in the Czech Republic. Stable hydrogen isotope (δ 2 H) analyses of feathers from 147 individuals hunted or trapped during winter in Camargue provide some insight into this question and suggest north-central Europe as a more likely area of origin. This indicates that greylags wintering along the Mediterranean coast maybe largely separate from the birds of the NW/SW European population breeding in Fennoscandia, although some individuals may also come from the Polish or German regions of the NW/SW flyway, since the combined ringing and stable isotope analyses suggest these birds are mostly breeding and moulting in an isotopic area consistent with the Czech Republic, Poland and northern Germany. Earlier studies show birds wintering in other French regions rather originate from Sweden and Norway. These results should be considered for the management plan currently being developed for greylag goose in Europe. More generally, they question whether birds from two distinct populations /flyways should be applied similar or potentially different management plans within a given country.

International audience; Delayed maturity and high survival rates of immatures and adults characterize long‐lived species’ life histories. Understanding how these traits interact in stochastic environments is essential to understand early life in long‐lived species and to assist conservation planning. Unfortunately, available information of demographic traits in immatures are often fragmentary and the logistical difficulties of capturing and recapturing this cohort leave little room for improvement. Published immature chelonian survival estimates vary broadly, are often not age‐specific, and lack precision. In an attempt to overcome this issue, we developed a novel modelling approach based on Capture‐Recapture data to obtain robust age‐specific survival probabilities in two chelonian species (the freshwater European pond turtle, Emys orbicularis, and the terrestrial Hermann's tortoise, Testudo hermanni). More specifically, we show that implementing a linear relationship between survival probabilities and age does not distort survival estimates and improves precision. Both species display a progressive increase in survival with age, reaching a plateau at the ages of four to five. As maturity occurs later in both species (8–12 years‐old), the survival plateau might be governed by the final hardening of the carapace, which brings obvious survival benefits. Taking advantage of the flexibility of multievent models we encourage a systematic field approach even when very large samples from immatures cannot be amassed. Only so can demographic traits in chelonians, and more generally in long‐lived species, be properly explored. The elusive nature of immature animals with delayed maturity has hindered the estimation of age‐specific survival. Early life capture‐recapture datasets are often sparse and incomplete precluding precision. In order to ameliorate this circumstance, we present here a novel statistical approach that can help streamline results of age‐specific early life survival of two chelonian species. Such endeavors are crucial for proper construction of projection matrices, indispensable to ecological and evolutionary studies and efficient conservation planning.

International audience; The effects of Hg contamination are presumably widespread across the components of aquatic ecosystems, but investigations have been mainly focused on freshwater fish, because this biota represents a major source of Hg for human populations. Yet, the possible bioaccumulation of Hg on other freshwater meso- and apex-predators (e.g., amphibians, reptiles) has been largely overlooked, especially in Western Europe. In this study, the determinants of Hg concentrations were assessed for the viperine snake (Natrix maura) across 6 populations (>130 individuals sampled in 2016 and 2017) in France and Spain. Specifically, body size, sex, and diet were compared with Hg concentrations measured in ventral scales. Overall, N. maura accumulated Hg in their scales. Sex did not seem to influence Hg concentrations in this species. Significant differences in Hg concentrations were observed between study sites, and these differences were likely to be mediated by site-specific diet. Frog-eating individuals were characterized not only by lower mean values of Hg (0.194 ± 0.018 μg·g−1 versus 0.386 ± 0.032 μg·g−1 for piscivorous individuals), but also by weaker slopes of the body size-Hg relationship as compared to fish-eating snakes, suggesting strong differences in accumulation rates due to food resources. Importantly, the highest slope of the body size-Hg relationship and the highest values of Hg were found in individuals foraging on trout raised by a fish farm, suggesting that fish farming may contribute to Hg contamination in inland freshwater systems. Finally, our results are compared with data on Hg concentrations in other species of aquatic snakes, in order to provide a comparative point for future studies.

The use of lead shot for wildfowling is a severe threat to waterbirds through ingestion of toxic lead pellets. Consequently, lead shot has been banned in many countries since the late 1990s and on Tour du Valat estate since 1994 (Camargue, France). An experimental study was undertaken to check if hunters would habituate to this new type of cartridge and consequently improve their effectiveness (average number of shots per bagged animal), assess the factors influencing effectiveness, and assess the trend of contamination in shot waterbirds and the estate sediment. From 1995 to 2005, we monitored hunting bags, spent cartridges, and the gizzards of shot ducks. Using generalized mixed effect models, we assessed the factors influencing hunter effectiveness. Instances of non-toxic pellets in duck gizzards increased, probably as a result of rapid accumulation in the sediments. We estimated that between 1995 and 2005, the lead shot ban spared 456 kg of lead from entering 403 ha of temporary marshes and avoided the contamination of 8 % of the ducks foraging on Tour du Valat. After 11 years of hunting with non-toxic shot, there was unexpectedly no clear pattern in trends of individual effectiveness among hunters. Hunter effectiveness was instead positively influenced by game abundance and hunter assiduity and negatively influenced by wind and number of shots, suggesting a lassitude effect. Our results suggest crippling loss can be reduced through regular practice, self-limitation of shooting intensity to below 20 shots to avoid lassitude effects, and self-limitation of shooting distance under strong wind conditions.

The non-indigenous red swamp crayfish (Procambarus clarkii) has been shown to be a threat for amphibian conservation. Many amphibian species breed in temporary ponds to diminish predation risk as such ecosystems are free of large predators. However P. clarkii, occurring as an invasive species in the Camargue delta, can readily disperse on the ground and thus colonize isolated ponds. We studied the current impact of the exotic crayfish on the reproductive success of the Mediterranean tree frog (Hyla meridionalis). In a mesocosm experiment, we tested the effect of two crayfish densities (1 and 3 crayfish/m2) on tadpole abundance. We also tested in a field experiment, within a temporary pond, the crayfish’s predation on the tree frog’s eggs. Finally, we developed site occupancy models using data from 20 ponds to assess the effect of crayfish abundance on tadpole abundance. Neither the experiments, nor the site occupancy models showed a negative impact of the current crayfish abundance on the tree frog populations breeding in ponds. We found that recorded crayfish densities were lower than in other areas where crayfish has impacted amphibian populations, but we hypothesize that current crayfish abundance in the area may increase in the future, thus impacting tree frog populations.

SUMMARY 1. Although the influence of water availability and precipitation regimes on amphibians has been studied at large scales, whether and how interannual rainfall and hydrological variations affect amphibians dynamics at a local scale have rarely been addressed. In this respect, accounting for variations in species detectability in space and time has also been overlooked. 2. We assessed the effects of rainfall and hydrological variations on the breeding dynamics of three amphibian taxa: Pelodytes punctatus, Hyla meridionalis and Pelophylax spp. in 20 ponds of the Camargue region (southern France) over a 7-year study period. 3. We used multiple season occupancy models to test the effect of winter‐spring rainfall and interannual variations in hydroperiod, mean water depth and drought events on tadpole presence in spring (March‐June), a proxy for breeding dynamics. 4. We used an independent survey with spatial replicates (dipnet sweeps) to disentangle the relative contributions of phenology and detectability to the absence of records in a given month. For the three taxa considered, the probability of missing a species when that species was actually present in a pond was most often negligible. Hence, we could consider that multiseason models properly tracked changes in species phenology. 5. Pelodytes punctatus was first detected in March, while the two other taxa appeared later in April. Hyla meridionalis appeared as a mid-season species with much more synchronous pond occupancy than Pelodytes punctatus. The detection peak of Pelophylax spp. was short and unexpectedly early for this taxon. 6. Seasonal winter‐spring rainfall was associated with a decrease in extinction rates and even more strongly with an increase in colonisation rates at individual ponds. 7. Colonisation rate increased following an annual drought and was best modelled as a negative quadratic effect of the variance of pond hydroperiod. Extinction probability was best modelled by a negative quadratic effect of mean water level. Hence, breeding was more stochastic (i) in unpredictable and shallow ponds because of yearly drying up and (ii) in highly predictable and deep ponds, possibly due to the presence of predators such as fish and crayfish. 8. Overall, we show that ponds with intermediate rather than extreme variations in environmental conditions currently correspond to optimal breeding sites. Our study demonstrates that amphibian monitoring coupled with fine-scale analysis of environmental conditions is necessary to understand species dynamics in the long run and to inform conservation efforts for these species.

International audience; Within the current context of biodiversity loss a number of biodiversity indicators have been developed to help measure the state of nature and how it is changing. However, most indicators are derived from bird populations. Reptiles and amphibians could be useful ecosystem indicators, but this requires obtaining precise and unbiased population parameters. This is a particularly challenging task for these two groups of species, because individuals are extremely difficult to detect for various reasons. We illustrate the use of a sampling and analytical method that explicitly takes into account imperfect detection to assess the population dynamics of a reptile species and its temporal and spatial variation. European pond turtles (Emys orbicularis) were sampled at two different locations during a 10-year study. The two sites differed by their water management regimes and number of livestock. At each site and for each sex, the data were modeled using a robust design capture-mark-recapture framework to obtain and compare estimates of survival, temporary emigration, time-specific abundance, density, and population growth rate, while taking into account effects of individual heterogeneity, trap-response, and time on capture probabilities. Temporary emigration was higher in males (0.344 +/- 0.046) (mean +/- SE) than in females (0.228 +/- 0.071), did not differ between sites for each sex, and was mainly Markovian. Apparent adult survival was higher in females (0.966 +/- 0.031) than in males (0.864 +/- 0.024), and was negatively related to the proportion of individuals with repaired shell fractures in the population. Average density was 63.7 +/- 6.6 turtles/km2 but was higher for females (39.2 +/- 14.0 females/km2) than for males (23.5 +/- 5.7 males/km2). The population sizes of males and females decreased where long periods of artificial drought and the highest density of livestock occurred. This research highlights differences in demographic parameters according to sex and site in a turtle species, and it provides evidence that significant human-induced disturbance represents a potential risk to European pond turtle populations. The sampling and analytical approaches illustrated in this study are applicable to many other species of reptiles and amphibians, and estimated population parameters could be combined to produce population indicators useful for conservation and management.

Reserves that are closed to hunting are important to wintering wildfowl Anatidae. Reserves can also benefit local hunters, because they are often used as day-roosts by birds prior to nocturnal feeding in surrounding wetlands. In this study, we used annual hunting bags from 45 hunting estates in the Camargue, southern France, to study the relationship between hunting success and distance to the nearest duck day-roost, which are generally located in protected areas. Five dabbling duck species Anas spp. and a diving duck species (pochard Aythya ferina) were studied. The relationship between hunting bag and distance from roost was negative in all cases except mallard Anas platyrhynchos, which is subject to specific hunting management practices (i.e. raise and release). However, a significant trend was not found for wigeon A. penelope and shoveler A. clypeata. This supports the hypothesis that hunting estates closer to protected areas are more successful. However, the decrease in hunting bags with inc...

Global biodiversity in freshwater and the oceans is declining at high rates. Reliable tools for assessing and monitoring aquatic biodiversity, especially for rare and secretive species, are important for efficient and timely management. Recent advances in DNA sequencing have provided a new tool for species detection from DNA present in the environment. In this study, we tested whether an environmental DNA (eDNA) metabarcoding approach, using water samples, can be used for addressing significant questions in ecology and conservation. Two key aquatic vertebrate groups were targeted: amphibians and bony fish. The reliability of this method was cautiously validated in silico, invitro and insitu. When compared with traditional surveys or historical data, eDNA metabarcoding showed a much better detection probability overall. For amphibians, the detection probability with eDNA metabarcoding was 0.97 (CI=0.90-0.99) vs. 0.58 (CI=0.50-0.63) for traditional surveys. For fish, in 89% of the studied sites, the number of taxa detected using the eDNA metabarcoding approach was higher or identical to the number detected using traditional methods. We argue that the proposed DNA-based approach has the potential to become the next-generation tool for ecological studies and standardized biodiversity monitoring in a wide range of aquatic ecosystems. see also the Perspective by Hoffmann, Schubert and Calvignac-Spencer.

Abstract The European pond turtle, Emys orbicularis, is a wide ranging species, distributed from Northwest Africa over a large part of Europe and Asia Minor to the Caspian and Aral Seas. For 106 pond turtles from France mtDNA sequence variation has been assessed, using a 1031 bp portion of the mitochondrial cytochrome b gene. Three of nine haploclades currently known from the entire species' range were found in France. One clade (II) is represented with four very similar haplotypes, differing by one mutation, and the two other clades (V, VI) are represented with one haplotype each. A syntopic occurrence of clades II and V is reported for the first time for the Camargue. Besides, clade II occurs in the French regions Aquitaine, Centre-Val de Loire, and Rhône-Alpes. Outside of France, it is found mainly in the catchment areas of the Danube and Oder rivers and in the Balkans. Haploclade V, which is also known from the Apennine peninsula, Sardinia, and the northern Mediterranean coast of Spain, is restricted in France to Corsica and the Provence-Alpes-Côte d'Azur region. A single individual bearing a haplotype of an Iberian and North African clade (VI) was found in Aquitaine near Pau. This could indicate gene flow between the Iberian peninsula and West France, if the specimen is native. The distribution of the distinct haploclades in France probably reflects Holocene range expansions, especially of haploclade II turtles. In the postglacial, haploclade II terrapins arrived from the east and spread over the Rhône corridor to the Mediterranean coast. In the southern Rhône area they met and hybridized with haploclade V turtles. Further research is needed to clarify whether this hybridization is a locally restricted phenomenon.

A total of 100 specimens of Emys orbicularis were collected and marked at Lake Tonga (northeastern of Algeria) during 3 consecutive years (2013, 2014, 2015). Most of the turtles inhabit a canal where they remain throughout the whole activity season (March to October) and where they overwinter as well. Carapace Length (CL) and body weight (BW) were measured for each individual of E. orbicularis . The size of the turtles of our population was more similar to those of northern European populations than to the Mediterranean populations; females were significantly larger than the Spanish and Italian populations. The population size was calculated as 108.50 and the density as 8.63 turtles/ha. From 6.52 to 12.77% of the population were juveniles. The adult sex ratio was slightly in favor of males (males:females = 1.12, P < 0.005).

7 pages; International audience; Among human activities, the effect of habitat management by grazing on population viability is ambiguous. Indeed, beneficial effects of grazing are expected by maintaining open meadows, but overgrazing is supposed to increase mortality by trampling. Grazing has been shown to negatively impact the survival of European pond turtle (Emys orbicularis) in the Camargue. Consequently, a new management plan was defined. We investigated the consequences of this management using capture-recapture methods to estimate variations of population sizes in this managed site and a control site over a 17 years period. Results show an increase of the number of adults and juveniles on the managed site after the management change. Our results suggest that improved water management with flooding in autumn provided better hibernation conditions, and that reduced grazing intensity in autumn/winter likely decreased the risk of trampling. Population size significantly increased in less than 4 years following the management change, probably by the relaxation of density-dependence. It is an original result for a long lived-species supposed to have an important time of resilience to perturbations.

12 pages; International audience; We investigated epizoic algal assemblages on the shell of European pond turtles (Emys orbicularis) during two years (2013–2014). A total of 60 Emys orbicularis were captured in the three shallow Mediterranean wetlands located in Camargue. Epizoic algae on the plastron (below the shell) and carapace (above the shell) were sampled, identified and counted. Seventy-seven epizoic algal species were identified on the carapace and plastron and comprised in 51 Bacillariophyta, 11 Chlorophyta, 7 Cyanophyta, 6 Euglenophyta, 1 Dinophyta and1Xanthophyta taxa. Our findings indicated a distinct distribution of epizoic algae according to taxonomical group density; Chlorophyta, and Cyanophyta were dominant on the carapace whereas the Xanthophyta (genus Vaucheria sp.) was dominant on the plastron. Turtleassociated algal assemblages did not differ among the wetlands.; Nous avons realisé une étude sur l'assemblage des algues épizoiques sur la carapace de Cistudes (Emys orbicularis) au cours de deux années (2013–2014). Soixante Emys orbicularis ont été collectés dans trois marais méditerranéens situés sn Camargue. Les algues épizoiques ont été identifiees et denombrees sur le plastron (dessous la carapace) et sur la dossière (dessus la carapace). Au total, 77 espèces d'algues epizoiques ont ete inventoriees sur la dossière et sur le plastron réparties en 51 Bacillariophyta, 11 Chlorophyta, 7 Cyanophyta, 6 Euglenophyta, 1 Dinophyta and 1 Xanthophyta. Nos recherches ont mis en évidence une distribution originale des algues épizoiques selon leur groupe taxonomique. Parmi les principaux groupes, les chlorophytes et les cyanophytes filamenteuses sont predominantes sur la dossière tandis que le groupe des xanthophytes (genus Vaucheria sp.) se développe sur l'ensemble des plastrons étudiés. Aucune différence dans les assemblages algaux n'a été observée entre les 3 marais étudiés.