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.

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Given the extreme importance of understanding biodiversity in the contemporary context, this study performed a taxonomic survey of planktonic green algae from a subtropical river in Paraná state, broadening knowledge of the group’s geographic distribution and the environmental conditions related to its occurrence. Monthly samplings of phytoplanktonic material were carried out from February 2015 to January 2016, resulting in the identification of 26 taxa belonging to the classes Chlorophyceae and Trebouxiophyceae, distributed among 16 genera and six taxonomic families. Among the taxa identified, seven are new citations for Paraná.

Lotic environments are subjected to the impacts of human activities in an intense way in urban regions and one of the ways to assist in the environmental diagnosis is through the knowledge of the composition of bioindicator organisms, including microalgae. The objective of this work was to qualitatively characterize the Chlorophyceae Class Wille, providing descriptions and meristic data of the specimens as well as the environmental conditions in which the taxa were recorded. Water and phytoplankton samplings were carried out quarterly in 2020, in nine supply rivers, distributed in three river basins in the western region of Paraná (Paraná III basin, Piquiri basin and Baixo Iguaçu basin). The studied rivers were classified as oligotrophic or mesotrophic and the taxa were mostly rare. Thirty-six taxa belonging to the Chlorophyceae class were recorded, distributed in five families: Hydrodictyaceae Dumortier, Neochloridaceae Ettl & Komárek, Radiococcaceae Fott ex P.C.Silva, Scenedesmaceae Oltmanns, Selenastraceae Blackman & Tansley. These taxa have mainly cenobial representatives, with about 70% of the individuals in this thallus configuration, followed by 22% colonies and 8% unicellular thallus. Among the identified species, five occurred only in mesotrophic sites, warning for environments with tendencies to elevate their trophic, since they are genera previously associated with these conditions. Ten new citations were recorded for the State of Paraná, namely: Pseudopediastrum boryanum var. longicorne (Reinsch) P.M.Tsarenko, Radiococcus skujae I.Kostikov, T.Darienko, A.Lukesová & L.Hoffmann, Desmodesmus perforatus (Lemmermann) E.Hegewald, Desmodesmus subspicatus (Chodat) E.Hegewald & A.W.F.Schmidt, Scenedesmus indicus Philipose ex Hegewald, Engelberg & Paschma, Ankistrodesmus bernardii Komárek, Monoraphidium capricornutum (Printz) Nygaard, Monoraphidium caribeum Hindák, Raphidocelis danubiana var. elegans (Playfair) Taşkin & Alp, Selenastrum rinoi Komárek & Comas. Taxonomic studies, such as this one, are an important tool for understanding the flora, and in addition to contributing to the registration of species in aquatic ecosystems, they serve as a basis for ecological studies and other approaches used to preserve biodiversity in these places.

Applying environmental fragility in studies evaluating watershed can guide policy decisions on monitoring and management regarding soil use planning, improving water quality for public supply. The objective of this study is to characterize the environmental fragility as well as to relate it to water quality factors of catchment rivers for public supply in western Paraná, Brazil, in order to evaluate the in uence of anthropic actions on catchment sources. Water quality data such as temperature (Temp; C), electrical conductivity (Ec; mS/cm −1 ), dissolved oxygen (DO; mg L −1 ), turbidity (Turb; NTU) and pH were measured on site by the multi-parameter probe HORIBA brand, model U-5000. Slope data were obtained from the site of the National Institute of Space Research (INPE). Soil use and occupation was performed in the QGis software, with image obtained from the Sentinel 2A Satelite. Köppen-Geiger classi cation was used for the climate type. For the environmental fragility maps, the variables slope, climate, soil use and occupation were analyzed using the QGis raster software calculator. The intermediate fragility class predominates in the nine municipalities studied, making it necessary to manage them aimed at restoration and conservation, and the municipalities that are the largest areas of high fragility class are: Guaraniaçu, Catanduvas and Cascavel, demanding greater attention. The variation in fragility mainly responded to the pH, E. coli and DQO temperature values, which can be strongly associated with the difference in soil use and slope of the areas evaluated.

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.

During a survey on freshwater epilithic diatoms from subtropical lotic environments belonging to the Cascavel River microbasin, Paraná State, Brazil, we observed populations of a new Nupela Vyverman et Compère species. Morphological and meristic analyses were performed using light and scanning electron microscopy, resulting in the description of Nupela semifasciata sp. nov. This species is characterized by elliptic-lanceolate valves containing subcapitate apices in larger individuals and broadly rostrate-rounded apices in smaller ones, while the length/width ratio gradually decreases as the individuals become smaller. The central area unilaterally reaches the margin and always interrupts the row of areolae on the valve mantle. The valve mantle is externally composed of a second row of areolae near the apices. We cross-checked information with similar Nupela taxa, highlighting the main features that separate them. Nupela semifasciata was found in streams with acidic-neutral pH, low conductivity and low to high nutrient concentrations.

Aim Urbanization, agriculture, and deforestation are the main anthropogenic factors that modify the soil, altering the quality of water, and influencing limnological aspects and the aquatic biota in rivers. We investigated the morphology-based taxonomic and functional response (MBFG) of the phytoplankton community among different public supply rivers in distinct hydrographic basins with ultraoligotrophic, oligotrophic, and mesotrophic characteristics. Methods We sampled the phytoplankton community and environmental variables in nine rivers along three hydrographic basins in western Paraná. In order to evaluate the taxonomic and functional relationship of the community with the environmental variables, we applied both variance and redundancy analyses. Results Differences in temperature, pH, turbidity, total phosphorus, chemical oxygen demand, and total dissolved solids were identified among river basins and/or trophic states. The highest taxonomic contributions to richness and biovolume were from green algae and diatoms, while the highest functional contributions were from MBFG IV (algae without specialized traits), MBFG V (unicellular flagellated algae), MBFG VI (algae with a siliceous exoskeleton) and MBFG (large colonial algae). The taxonomic approach was sensitive to environmental variability in the rivers, while for the functional approach no relationship to environmental variability was identified. Conclusions The taxonomic approach of the phytoplankton community was more sensitive to the environmental variability of the studied rivers than the functional approach based on morphology. Therefore, we reinforce the importance of biological indicators for understanding the dynamics in aquatic ecosystems, providing crucial information for the management of water resources used for public supply.