Cinquante-huit espèces appartenant au genre Mastogloia ont été répertoriées dans des prélèvements effectués dans la zone infralittorale (-1,5 à - 7 mètres sous le zéro des cartes) sur la côte d'une île située au Nord-Est de l'Océan Atlantique (Île de Groix). La majorité de ces espèces est présente dans les régions tropicales et subtropicales. Cette étude apporte de nouvelles informations sur la distribution géographique de ces espèces. En outre, la morphologie de quatre espèces non identifiées est décrite en microscopie photonique.

Two commonly reported Frustulia morphospecies from oligotrophic habitats, F. crassinervia and F. saxonica, showed overlapping morphological variation within natural populations and between clonal strains representing different genetic entities. Therefore, morphologies of natural populations of the F. crassinervia-saxonica complex were analyzed using geometric morphometric techniques regardless of species or genetic identity. It has been examined whether shape, centroid size, morphological diversity, and globularity of valves from three types of peatland habitats representing ombro-minerotrophic gradient reflected ecological differentiation within the Frustulia crassinervia-saxonica species complex. Morphometric analyses showed that valve differences within the species complex were significantly correlated with environmental conditions. In particular, allometric shape changes and size of valves showed strong relationships with different types of peatland habitats. It has been suggested that allometry probably acts as a constraint on morphological plasticity and is canalizing microevolutionary morphological differentiation within the F. crassinervia-saxonica complex.

The history of the marine station of the Muséum national d'Histoire naturelle, from its creation on the island of Tatihou, off Saint-Vaast-la-Hougue, to its present existence as the Research and Education Center on coastal systems in Dinard, through the facilities in Saint-Servan, sheds a new light on the constitution of the algae herbarium of Dinard. The content of this herbarium reveals a representation of the history of people and concepts in over 200 years of phycological researches in this area of Normano Breton Gulf. Such an understanding now makes possible to consider interpreting data in the frame of temporal changes in algal communities.

Recent changes in seaweed communities due to rapid shifts of their environment have been largely documented in temperate waters; however, long-term studies are much scarcer. In this study, we investigated the potential of Dinard Herbarium to inform us on temporal changes in seaweed communities of Brittany since the second half of the 19^th century. From nearly 3000 specimens collected in France, we identified and, when possible, corrected taxonomic and localisation errors usually encountered in unchecked natural history collections therefore minimising data inaccuracies. This original study aimed to describe the temporal dynamics of this collection and discuss the relevance of Dinard Herbarium in assessing temporal changes in seaweed communities of Brittany. The use of herbaria to assess spatio-temporal changes of seaweed biodiversity is limited, and to our knowledge, this is the first study trying to investigate this potential in the European Atlantic. This work presents new perspectives for inferring temporal changes of seaweed biodiversity.

Fucales (Phaeophyceae, kingdom Stramenopiles) are ecosystem engineers and canopy forming seaweeds that are dramatically declining worldwide. In the Mediterranean Sea, Cystoseira spp. and Sargassum spp. have been shown to be locally extinct or locally functionally extinct, i.e. no longer forest forming, even in some Marine Protected Areas (MPAs).

The patterns of change in the diversity and abundance of Fucales taxa within the Port-Cros Archipelago (Port-Cros National Park; PCNP) was studied by comparison of recent data (2005 to 2007) with previous data in order to measure the effects of protection since the creation of the park in 1963. Three taxa were reported before 1963, 10 between 1963 and 2005 and 17 between 2005 and 2007. Considering the biology of the species listed and the distance from the coast of the Port-Cros Archipelago, it is unlikely that this increase in species richness has resulted from colonisation events through the implementation and enforcement of effective protection of the area but is rather due to an increase in sampling effort. In contrast to other Mediterranean areas, the populations of Fucales are still highly diversified and stable. Only one species, C. brachycarpa var. brachycarpa, has declined in the 1-10-m depth zone in relation to the proliferation of herbivorous species, possibly enhanced by the PNPC conservation strategy. The overall good conservation of Fucales populations of the PCNP is probably the result of the absence of habitat destruction, high seawater quality and the regulation of human activities (fishing, tourism, diving).