Aim Structural changes in phytoplankton was evaluated in one ultraoligotrophic and two oligotrophic cascading reservoirs during two climatic periods (austral winter and summer) of 2014. Changes in phytoplankton biomass, species composition, and codons (functional groups) were evaluated along a vertical and a longitudinal profile. Methods Four sampling sites were selected for the first reservoir in the cascade (Cachoeira do França) and three for each of the other two reservoirs (Cachoeira da Fumaça and Serraria). Samples were collected along a vertical and a longitudinal profile. Species biomass and codons ‘sensu’ Reynolds were identified and expressed in terms of biomass. Results 18 codons were identified and associated to the reservoirs’ limnological conditions. Composition and biomass of descriptor species changed among seasons. Codon B consisting mainly of Discostella stelligera was the most frequent in all reservoirs in both climatic seasons. Conclusions Our findings showed that seasonality was the key factor for the species composition and phytoplankton codons changes. However, the cascade effect on phytoplankton structure was shown by the continuous contribution of Ceratium furcoides (codon LM) during the winter, and of Discostella stelligera (codon B) in both sampling periods in all three reservoirs.

-(Cryptogams of Parque Estadual das Fontes do Ipiranga, São Paulo, São Paulo State, Brazil. Algae 40: Chlorophyceae (Hydrodictyaceae)). A floristic survey of the family Hydrodictyaceae (Sphaeropleales, Chlorophyceae) was carried out for the Parque Estadual das Fontes do Ipiranga, municipality of São Paulo, São Paulo State, southeast Brazil. Six genera (Chlorotetraedron, Lacunastrum, Monactinus, Pediastrum, Stauridium, and Tetraedron), eight species, three typical varieties, and one that is not the typical from its respective species were identified. Identification of L. gracillimum and M. simplex var. echinulatum is pioneer for the park. Stauridium tetras is the best represented species in the area, being collected from three different localities (reservoirs). Keywords: coccoid green algae, periphyton, phytoplankton, taxonomy, urban reservoir RESUMO -(Criptógamos do Parque Estadual das Fontes do Ipiranga, São Paulo, SP, Brasil. Algas 40: Chlorophyceae (Hydrodictyaceae)). O levantamento florístico da família Hydrodictyaceae (Sphaeropleales, Chlorophyceae) foi realizado para a área do Parque Estadual das Fontes do Ipiranga, Município e Estado de São Paulo, Brasil sudeste. Foram identificados seis gêneros (Chlorotetraedron, Lacunastrum, Monactinus, Pediastrum, Stauridium e Tetraedron), oito espécies, três variedades taxonômicas típicas e uma que não é a típica de sua respectiva espécie. Lacunastrum gracillimum e Monactinus simplex var. echinulatum tiveram sua ocorrência citada pela primeira vez no Parque. Stauridium tetras foi a espécie melhor representada na área de estudo, tendo sido coletada em três localidades (reservatórios).