title: Continuity effects on rotifers and microcrustaceans caused by the construction of a downstream reservoir in a cascade series (Iguaçu River, Brazil).
abstract: This study evaluated changes in the community of rotifers and microcrustaceans associated with the construction of a large and dendritic reservoir in Iguaçu River (Brazil), as the last reservoir of a sequence of five cascading systems. Differences were clear between pre-filling and post-filling phases for organisms and some of environmental variables. In the pre-filling phase, the community was more homogeneous along the downstream river gradient, and spatial compartmentalization in the new reservoir was common during the post-filling phase. From 140 identified taxa, 10 species occurred exclusively in the pre-filling phase and 32 in the post-filling phase. After completion of the fifth reservoir filling-up, opportunistic, pioneer and fast-developing species quickly dominated, and downstream of the fourth reservoir the pre-filling decreasing gradient of richness, diversity and evenness disappeared. Richness of rotifers and cladocerans, cladocerans diversity, and evenness of rotifers, cladocerans and copepods were generally higher in the post-filling phase. A non-metric multidimensional analysis based on a presence/absence matrix depicted a homogeneous and dense group of species associated to the pre-filling phase and a second, dispersed group related to the post-filling phase. Spearman correlations pointed out significant positive effects of transparency on rotifer species richness in the post-filling phase, and negative effects on the microcrustacean richness in the pre-filling phase. Dam construction caused disruption of the downstream lotic gradient along the series of dams, leading to the development of distinct species in lentic spatial compartments.
authors.affiliation: Curso de Engenharia de Pesca, Laboratório de Aquicultura, Universidade Federal do Recôncavo da Bahia, Cruz das Almas, BA, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Serafim-Júnior
authors.affiliation: Núcleo de Estudos em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá, Maringá, PR, Brazil.
authors.forename: F A
authors.initials: FA
authors.lastname: Lansac-Tôha
authors.affiliation: Instituto Oceanográfico, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: R M
authors.initials: RM
authors.lastname: Lopes
authors.affiliation: Centro de Ciências da Natureza, Universidade Federal de São Carlos, Buri, SP, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Perbiche-Neves
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods; D001938:Brazil; D033342:Copepoda / Q000502:physiology*; D055669:Ecological and Environmental Phenomena; D056127:Hydrobiology; D011156:Population Density; D011157:Population Dynamics; D045483:Rivers; D012403:Rotifera / Q000502:physiology*; D012621:Seasons; D015048:Zooplankton / Q000502:physiology*