Two new diatom species of the genus Aneumastus are described, A. laosica sp. nov. and A. genkalii sp. nov., based on light and scanning electron microscope observations. These species were found in Laos, and this is first finding of this genus from Southeast Asia. Almost all species from this genus were described and exist in Holarctic. Many species have restricted distributions and are known from fossil deposits, North America, Mongolia or local endemics of ancient lakes such as Baikal, Prespa and Ohrid. Diversity of Aneumastus species from these ancient lakes is higher than from waterbodies of the Holarctic region taken together. A few reports of this genus are from the southern Hemisphere (e.g. New Caledonia, Australia, Lake Tanganyika in Africa), but these taxon records are represented by a single valve only from every region and they require additional taxonomical investigation and verification to understand the full extent of the distribution of the genus.

Characeae are macroscopic green algae present in the Maghreb (Morocco, Algeria, Tunisia) that are known since the 19^th century works of Desfontaines (1800) and Braun (1868). Feldmann (1946) published the first regional synthesis, and this study provides a new Maghreb-wide synthesis of all collections made since 1784 (570 observations distributed over 464 sites). Each of the 31 reported species is described in detail with its diagnostic features, ecology and distribution in the three Maghrebian countries. Distribution maps distinguish between the three collection periods: 1780–1939, 1940–1979, and 1980–2016. An illustrated key is provided to help botanists working in the Maghreb to identify the taxa. From a biogeographical perspective, the Characean flora of the Maghreb is dominated by elements originating from northern (European) countries (61.3%) that include regionally very rare species such as Chara strigosa and C. tomentosa. The Mediterranean-Atlantic element is also well represented (32.3%), with some Mediterranean endemics (Chara imperfecta, C. oedophylla, C. vulgaris var. gymnophylla). Finally, two taxa that have an affinity for tropical conditions (Chara zeylanica and Lamprothamnium succinctum) extend to the southern Sahara. In North Africa, 14 species (7 Chara, 2 Lamprothamnium, 4 Nitella and 1 Sphaerochara) are threatened and raise issues about their conservation; three of these are particularly endangered: Chara imperfecta, C. oedophylla and Lamprothamnium papulosum.

This study was conducted to simultaneously investigate the spatial and temporal dynamics of diatom communities inhabiting two microhabitat types (Sphagnum periphyton and epipelon) in a peatland area of the Czech Republic. The changes in diatom community structure and corresponding diversity indices at both large (i.e., variation between sites) and small (i.e., variation between two microhabitats) scales were assessed through time. The results indicated clear spatial patterns at large, but not at small scale, and only limited seasonal dynamics in the diatom community. At the large scale, significant differences in diatom communities among sites were associated with both geographic position and environmental conditions (pH and conductivity). A significant effect of microhabitat type was detectable within sampling sites; the relationship between other factors and species data was not important on a small scale. The results of this study showed that both diatom diversity and community structure are good indicators of ecological heterogeneity associated with relatively high spatial and/or environmental variability. However, subtle differences in environmental conditions are hardly detectable or hidden using traditional diatom species.

The Indo-Pacific species Avrainvillea amadelpha (Montagne) A. Gepp & E.S. Gepp is reported for the first time from the Mediterranean Sea (Kerkennah Islands, Tunisia). The species is considered as introduced and invasive in the Hawaiian Archipelago. The Mediterranean specimens are studied and the reproductive structures are described and illustrated here for the first time. The possible origins and vectors of this introduction and the risk of propagation of the species in the Mediterranean Sea are discussed.