The diversity and structure of epiphytic macrofaunal assemblages on the introduced invasive brown macroalga Sargassum muticum and native fucoids (Bifurcaria bifurcata, Cystoseira humilis, Cystoseira tamariscifolia and Sargassum vulgare) were compared over a 1-year period in intertidal rockpools on the Atlantic coast of Morocco. In comparison with the epiphytic fauna associated to other macroalgae from European shores, we found that the associated epiphytic macrofauna was moderately diverse (H'<3 bit) and was mainly dominated by gastropods and crustaceans. The most abundant taxa were the isopod Dynamene bidentata and the gastropods Steromphala umbilicalis and Steromphala pennanti. The epiphytic macrofauna community structure differed slightly between the invader and the natives along the year. There was significant temporal variation in the total number of individuals of epiphytic macrofauna per thallus dry weight for the associated epifauna with the highest abundance found on C. tamariscifolia in the spring. The composition of the epiphytic macrofauna on each macroalga species was fairly constant over time. Overall, our results demonstrated that the mobile epiphytic macrofauna on this rocky area showed low macroalgal specificity. They also revealed that the invader S. muticum supports similar epiphytic macrofaunal communities as the native brown macroalgae and provides an additional appropriate habitat for a generalist associated epiphytic macrofauna.

On the basis of bibliographical, morphological and molecular studies (SSU rDNA), the reinstatement of species rank for Chaetomorpha stricta Schiffner, a poorly known Mediterranean endemic species described in the early 20th century, is proposed. Previously reduced to a posterior heterotypic synonym of C. linum (O.F. Müller) Kützing, C. stricta clearly differs from the latter by its small, light green, free-living filaments entangled in dense masses, the cells 0.5 to 1.6 (rarely 2) times as long as broad, with cell walls lamellate and broad up to 75–90 μm thick, and by molecular data. Chaetomorpha stricta was rediscovered, in May 2011, in oligotrophic clear waters of a closed fishing pond in the Valle Cavallino (northern basin of the Venice Lagoon). A critical review of Chaetomorpha taxa reported in the Mediterranean Sea and a taxonomic key to the Mediterranean taxa currently accepted are presented.

In recent years, sections of the paraphyletic genus Batrachospermum have been investigated using DNA sequence data, as well as morphology and some have been raised to genera in order to resolve this paraphylly. The species of Batrachospermum section Virescentia form a well-supported clade and we propose the raising of this section to the genus Virescentia stat. nov. In addition, we re-evaluated the characters used to circumscribe species by reexamination of type specimens and new collections in historically important areas. Of the eleven previously accepted species, we recognize five species and a new species is proposed as follows: V. crispata, V. gulbenkiana (synomyms V. azeredoi and V. ferreri), V. helminthosa (type species), V. viride-americana sp. nov., V. viride-brasiliensis and V. vogesiaca. The species are circumscribed on the basis of morphological characteristics (shape of fascicles, occurrence of secondary fascicles, disposition of carpogonial branches and size of carpogonia), geographic distribution, and DNA sequence data (rbcL and COI-5P). Descriptions, identification key and photomicrographs are presented for each recognized species. Two potential species from Japan based on DNA sequence data remained undescribed due to lack of voucher specimens for morphological observation. Other species previously assigned to the section Virescentia are referred to other genera of Batrachospermales based on morphology (disposition of carpogonial branches, shape of trichogynes, types of gonimoblast filaments and arrangement of carposporophytes).

The rare endemic Mediterranean alga Kallymenia spathulata was collected at Nice and Saint Raphael in June 2013 during a survey conducted along the French Mediterranean coast between Menton and Toulon (French Riviera). DNA barcode sequences (COI-5P) generated from the five collected specimens were identical and allied with Felicinia marginata, another Mediterranean endemic that is classified within the Halymeniaceae (Halymeniales) whereas the genus Kallymenia is representative of the Kallymeniaceae (Gigartinales). We further confirmed the alliance of K. spathulata with Felicinia marginata by conducting phylogenetic analyses inferred by combined genes including Cox1, rbcL and LSU. Unfortunately, none of the specimens were fertile, precluding emending the description of the reproductive anatomy of this species. In light of our phylogenies, we propose the novel combination Felicinia spathulata. The genus Felicinia now comprises two species, both endemic to the Mediterranean Sea.

Two new curved species and a new record of a straight species are reported; neither new species has the craticular bars seen in the generitype. C. desportesiae resembles C. guamensis and C. riddleae in size and number of plastids (2 pairs) but has much finer striae (46–50 in 10 µm). C. leandrei has multiple plastids and is very long, like C. koenigii but more slender and with rectangular rather than circular areolae. Valvocopulae of this species are described for the first time in Climaconeis spp., which otherwise show no distinction among copulae. A straight species, provisionally identified as C. scalaris, is reported for the first time from tropical waters. An updated key to the 18 known species is provided.

We describe as new to science six new species of the diatom genus Gomphonema Ehrenberg from Lake Baikal, based on light and scanning electron microscope observations. The six species are morphologically similar to G. ventricosum, a northern European taxon known mostly from Scotland, Scandinavia and other Baltic countries, though it has been recognized also from North America. The six species are similar to G. ventricosum W. Gregory in the structure of the external occlusions over the areolae. The species also have prominent septa and pseudosepta, which distinguishes them from other species of the genus. They are distinguished from one another in the shapes and sizes of the valves. This group of closely related species may correspond to a species flock, a phenomenon in freshwater diatoms that is known from ancient lakes and flowing water systems. Further research is needed to confirm the monophyly of this group, and either support or challenge the idea of them representing a species flock.