The upper Paraná river floodplain is a strategic area for the Brazilian biological and environmental patrimony and contains several conservation units. We aimed to record the occurrence and the geographic distribution of microalgae in this floodplain during 30 years of research carried out by the Center for Research in Limnology, Ichthyology and Aquaculture - State University of Maringá. We consulted 80 publications (national and international journals and books published from 1986 to 2016). We considered only published works that referenced algae at the generic and infrageneric levels. The results indicated 938 species of algae (562 periphytic, 482 planktonic), which 103 co-occur in the two habitats. Cosmarium was the richest genera for periphyton and Traquelomonas for phytoplankton. This study increased the knowledge of microalgae biodiversity in Brazil and provided data for future ecological and biogeographic studies.
Aim A taxonomic study of the species of the genus Cosmarium Corda ex Ralfs (Desmidiaceae) was conducted in two lentic environments of the Upper Paraná River Floodplain (Garças and Patos lakes). Methods The samples were collected in November 2016. Two petioles of Eichhornia azurea (Sw) Kunth were sampled and analyzed qualitatively. Results Six species, nine varieties, and three forms were identified, with five taxa being common to both lakes, nine in Garças Lake, and four in Patos Lake. Of this, thirteen species represent the first records for the floodplain environment. Conclusion This study contributes to the knowledge of the biodiversity of this region, providing support for future ecological studies and biomonitoring.
Habitat type and grazing are key factors controlling benthic diatom communities. Nonetheless, the strength of grazing may depend on the habitat complexity at fine (substratum roughness) and meso scales (mesohabitat type). The interaction between grazers and physical conditions may thus be an important factor shaping benthic diatom communities. Several investigations have evaluated how habitat type, grazing and substratum roughness separately affect the biomass, species richness and community structure of algal communities. However, how these factors act together remains poorly understood, particularly for sets of common and rare species. The latter is important for understanding whether common and rare species are affected differently by environmental filters at the local scale. We investigated the effects of mesohabitat type, grazer occurrence and substratum roughness as well as their interactions on benthic diatom communities in a split‐split‐plot field experiment consisting of hierarchical treatments: (i) mesohabitat (pools and riffles); (ii) grazer occurrence (presence or absence of grazers >1 cm in size); and (iii) substratum roughness (smooth and rough substrata). We analysed the entire community and also datasets of common and rare species. Here, we define common and rare species based on their abundance–occupancy relationships, with rare species presenting low mean abundance per experimental unit (between 0.025 and 8.2) and low occupancy (between 2.5% and 25%). Substratum roughness was the main factor explaining differences in species richness, with higher species richness found on rough than on smooth substrata for both the complete dataset and for common and rare species. There was evidence that the interactions between mesohabitat and grazer occurrence and between mesohabitat and substratum roughness affected community structure (relative abundances) for the complete dataset and for common species, whereas the three‐way interaction between mesohabitat, grazer and substratum roughness affected community structure of rare species. Our findings emphasise that crevices are important microhabitats that allow the establishment of both common and rare species. Furthermore, our results suggest that physical differences between mesohabitats influenced the effect of grazers on the community structure of common and rare species. For common species, the effects of this interaction were difficult to depict, but we found a change in the second‐most‐common species between mesohabitats and depending on the occurrence of grazers. For rare species, grazers more clearly affected community structure on smooth substrata in riffles than in pools. Our results demonstrate that local patterns of common and rare diatom species resulted from distinct combinations of the evaluated environmental filters. Together, our results highlight how multifactorial field experiments are key to understanding the main environmental filters driving the species richness and community structure of benthic diatom communities.
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