Gomphonema Ehrenberg is a genus well represented in periphytic algal flora of epicontinental environments. The substrate colonization is facilitated by the secretion of mucilage by the pore field, allowing cell adhesion. Samples were scraped off and analyzed from vegetative portions of the macrophyte Eichhornia azurea Kunth, collected in São Francisco Falso River, located in Santa Helena City, Paraná State. The sampling occurred in four different sites, in four different periods, totaling 16 samples. The quantitative material analysis resulted in 28 identified taxa, in which Gomphonema brasiliense ssp. pacificum, Gomphonema neoapiculatum Lange-Bertalot, Reichardt & Metzeltin Gomphonema pantropicum Reichardt and Gomphonema perapicatum Metzeltin & Lange-Bertalot represented pioneer citations for Paraná diatomflorula. The ultrastructure observations of some species were crucial to distinguish a few taxa, as Gomphonema brasiliense and Gomphonema brasiliensoide D. Metzeltin, Lange-Bertalot & F. García-Rodríguez. We suggest future studies in this environment, once it has propitious characteristics to the development of epilithic diatoms. Moreover, phylogenetic studies are also recommended for a better distinction of taxa with a wide morphologic variation.

A world checklist of Diatoms, compiled by taxonomic experts and based on peer-reviewed literature.

Examination of samples from different aquatic environments from Brazil revealed the presence of a new Aulacoseira species. Aulacoseira veraluciae Tremarin, Torgan & T. Ludwig is described and illustrated with light and scanning electron microscopy, and its morphology compared with that of similar species, such as A. muzzanensis (Meister) Krammer, A. granulata (Ehrenberg) Simonsen and A. agassizii (Ostenfeld) Simonsen. The new species is characterized mainly by the straight pervalvar rows of areolae, morphology of the linking spines, shape and position of the rimoportulae on the valve mantle, deepness and thickness of the ringleiste.

Knowledge of biodiversity in oligotrophic aquatic ecosystems is fundamental to plan conservation strategies for protected areas. This study assessed the diatom diversity from an urban reservoir with oligotrophic conditions. The Piraquara I reservoir is located in an Environmental Protection Area and is responsible for the public supply of Curitiba city and the metropolitan region. Samples were collected seasonally between October 2007 and August 2008. Periphytic samples were obtained by removing the biofilm attached to Polygonum hydropiperoides stems and to glass slides. The taxonomic study resulted in the identification of 87 diatom taxa. The most representative genera regarding the species richness were Pinnularia (15 species) and Eunotia (14 species). Five species were registered for the first time in Brazil and seven in the State of Paraná. Taxonomic and ecological comments of the species registered are provided.

Associating anthropogenic effects with variations in biodiversity is key to understanding how anthropogenic impacts are extrapolated in public supply micro-watersheds. The structure and dynamics of metacommunities in aquatic environments depend not only on the river network itself, but on a multitude of factors. Therefore, we associate the density and species richness of diatoms, assessed in a micro-watershed, with the following driver factors: local environmental variables, spatial variables, landscape characteristics, and the historical community, comparing their possible dispersal routes. Variance partitioning was performed using partial RDA models, with prior selection of predictor variables, to estimate the relative role of each predictor in the diatom community. The small scale of the micro-watershed resulted in a small spatial gradient, reflecting in the low variation in community richness across sampling stations. However, temporal heterogeneity associated with fluctuating precipitation throughout the year may cause temporal variation in the relative abundance of species. This pattern is a result of the supply of resources that increases biodiversity over time, as it allows the coexistence of species that alternate between dominance and persistence. Thus, even on a small scale and during one year of sampling, we demonstrated that predictors of different natures act together to explain diatom communities in micro-watersheds.