Multi‐dimensional effects on Cladoceran (Crustacea, Anomopoda) assemblages in two cascade reservoirs in Southeast Brazil

Abstract

The Cladocera assemblages in two cascade reservoirs located in the Paranapanema River in Brazil were studied during two consecutive years. Upstream Chavantes Reservoir is an accumulation system, with a long water retention time, high depth and oligo-mesotrophic status. The downstream Salto Grande Reservoir is a small, run-of-river reservoir, with a short water retention time, shallow depth and meso-eutrophic status. The goal of this study was to determine the interand intra-reservoir limnological differences with emphasis on the Cladocerans assemblages. The following questions were posed: (i) what are the seasonal dynamics of the reservoir spatial structures; (ii) how dynamics, seasonally, is the reservoirs spatial structure; and (iii) are the reservoir independent systems? A total of 43 Cladoceran species were identified in this study. Ceriodaphnia silvestrii was the most abundant and frequent species found in Chavantes Reservoir, while C. cornuta was most abundant and frequent in Salto Grande Reservoir. The Cladoceran species richness differed significantly among sampling sites for both reservoirs. In terms of abundance, there was a significant variation among sampling sites and periods for both reservoirs. A cluster analysis indicated a higher similarity among the deeper compartments, and the intermediate river-reservoir zones was grouped with the riverine sampling sites. For the smaller Salto Grande Reservoir, the entrance of a middle size tributary causes major changes in the system. A distinct environment was observed in the river mouth zone of another small tributary, representing a shallow environment with aquatic macrophyte stands. A canonical correlation analysis between environmental variables and Cladoceran abundance explained 75% of the data variability, and a complementary factorial analysis explained 65% of the variability. The spatial compartmentalization of the reservoirs, as well as the particular characteristics of the two study reservoirs, directly influenced the structure of the Cladoceran assemblages. The conditions of the lacustrine (dam) zone of the larger Chavantes Reservoir were reflected in the upstream zone of the smaller downstream Salto Grande Reservoir, highlighting the importance of plankton exportation in reservoir cascade systems. The comparative spatial-temporal analysis indicated conspicuous differences between the two reservoirs, reinforcing the necessity of considering tropical ⁄ subtropical reservoirs as complex, multi-compartmental water systems.

Phytoplankton structure in two contrasting cascade reservoirs (Paranapanema River, Southeast Brazil)

“…In Chavantes, the use of the adjacent soil is less intensive. Additional limnological information for both reservoirs can be found in Nogueira et al (2006) and Perbiche-Neves & Nogueira (2010).…”

Copépodes (Crustacea, Calanoida, Cyclopoida) planctônicos em reservatórios profundos e dendríticos: efeitos do tempo de residência e da idade de formação

“…compartimentalização espacial, como observado para os cladóceros (Perbiche-Neves & Nogueira, 2010) e fitoplâncton (Perbiche-Neves et al, 2011). Zonas lacustres, intermediárias e lóticas costumam ser identificadas em reservatórios, e a mistura de águas intermediárias ou lacustres com desembocadura de tributários (ponto MSC, por exemplo) podem ocasionar elevados valores de diversidade (H').…”

Continuity effects on rotifers and microcrustaceans caused by the construction of a downstream reservoir in a cascade series (Iguaçu River, Brazil)

“…Similar results of fast colonisation were found by Garrido and Bozelli (2000) during the filling of another large reservoir in Brazil. The higher species richness in the Iguaçu River compared to tributaries in both phases is probably due to the drift of species downstream from upstream reservoirs and the large size of the river, as occurs in most rivers connected to permanent or temporary bodies of water, from where individuals are exported (Pourriot et al, 1997;Lopes et al, 1997;Viroux, 2002;Perbiche-Neves and Nogueira, 2010;Perbiche-Neves et al, 2012).…”

“…Bosmina hagmanni, Ceriodaphnia cornuta, C. cornuta rigaudi, Daphnia gessneri and Moina minuta were the most frequent species in the pre-and post-filling phases. These species are frequent in the Neotropical region (Dodson and Silva-Briano, 1996;Pinto-Coelho, 1998;Nogueira, 2001;Sendacz et al, 2006;Perbiche-Neves and Nogueira, 2010). Moina reticulata, which only occurred in the pre-filling phase, is endemic to the Neotropical region (Paggi, 1993).…”

“…For plankton communities, changes occur in several ecological attributes such as species richness, diversity and abundance of phytoplankton and zooplankton, when lotic species are replaced by lentic species after stabilisation of the system (Pedrozo et al, 2012). The interactions occurring between the river basin and the impounded water lead to the establishment of spatial gradients (longitudinal and lateral gradients) of biotic and abiotic variables in the reservoir main channel (Perbiche-Neves and Nogueira, 2010;Perbiche-Neves et al, 2011). The formation of many side-arms generally associated with tributary rivers is common in dendritic reservoirs, which can also contribute to the formation of lateral gradients (Ward, 1989;Van Den Brink et al, 1994;Bonecker et al, 2001).…”