title: Response of phytoplankton to an experimental fish culture in net cages in a subtropical reservoir.
abstract: This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.
authors.affiliation: Programa de Pós-graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná - UNIOESTE, Rua da Faculdade, 645, Jardim Santa Maria, CP 320, CEP 85903-000, Toledo, PR, Brazil.
authors.forename: E C R
authors.initials: EC
authors.lastname: Bartozek
authors.affiliation: Programa de Pós-graduação em Recursos Pesqueiros e Engenharia de Pesca, Universidade Estadual do Oeste do Paraná - UNIOESTE, Rua da Faculdade, 645, Jardim Santa Maria, CP 320, CEP 85903-000, Toledo, PR, Brazil.|Programa de Pós-graduação em Conservação e Manejo de Recursos Naturais, Universidade Estadual do Oeste do Paraná - UNIOESTE, Rua Universitária, 2069, Jardim Universitário, CEP 85819-110, Cascavel, PR, Brazil.
authors.forename: N C
authors.initials: NC
authors.lastname: Bueno
authors.affiliation: Programa de Pós-graduação em Conservação e Manejo de Recursos Naturais, Universidade Estadual do Oeste do Paraná - UNIOESTE, Rua Universitária, 2069, Jardim Universitário, CEP 85819-110, Cascavel, PR, Brazil.|Centro de Difusão de Desenvolvimento Tecnológico do Rio Iguaçu - CDT-Iguaçu, Capitão Leônidas Marques, PR, Brazil.|Grupo de Estudos de Manejo na Aquicultura - GEMAq, Universidade Estadual do Oeste do Paraná - UNIOESTE, Rua da Faculdade, 645, Jardim Santa Maria, CP 320, CEP 85903-000, Toledo, PR, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Feiden
authors.affiliation: Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá - UEM, Av. Colombo, 5790, Bl. H-90, CEP 87020-900, Maringá, PR, Brazil.
authors.forename: L C
authors.initials: LC
authors.lastname: Rodrigues
mesh_terms: D000818:Animals; D044822:Biodiversity; D001938:Brazil; D000460:Chlorophyta; D003247:Conservation of Natural Resources; D000458:Cyanobacteria / Q000737:chemistry / Q000145:classification / Q000502:physiology; D017377:Diatoms / Q000737:chemistry / Q000145:classification / Q000502:physiology; D005398:Fisheries; D005399:Fishes / Q000502:physiology*; D005502:Food; D009584:Nitrogen; D010839:Phytoplankton / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D012621:Seasons
chemical_list: D009584:Nitrogen