We investigated the effect of interannual variation of hydrosedimentological regime and connectivity on the zooplankton biodiversity in the Upper Paraná River floodplain. Zooplankton samplings were undertaken between 2000 and 2007, in different environments of the floodplain, including connected and isolated floodplain lakes, backwaters, rivers and channels. The zooplankton included 541 species. Rotifers showed the highest species richness and abundance. Among the zooplankton species, 71 represent new occurrence records for the floodplain. The species accumulation curve showed a continuous increase in gamma diversity, demonstrating the importance of long-term research for accurate knowledge of biodiversity in heterogeneous and dynamic ecosystems, such as the floodplains. Interannual beta diversity among studied years indicated a lesser alteration in community composition in 2001, when a long limnophase period was observed. In most of the environments, the highest species richness values were related to the greatest flooding amplitudes. Flooding amplitude, which is associated with connectivity, favors faunal exchange amongst the environments and between the pelagic and littoral zones. This explains the occurrence of both planktonic and non-planktonic species within the community. On the other hand, mean zooplankton abundance values were higher when a long isolation period occurred. Differences between the potamophase and limnophase amplitude associated with connectivity among the environments were the most important factors for the structure and dynamics of the zooplankton community in the Upper Paraná River floodplain.

competition and habitat alteration (Mack et al., 2000). Thus, there is a growing need to understand the invasion process and to predict the success and effects of invading species (Moyle and Light, 1996) in order to AbstractThe integrity of aquatic ecosystems is being challenged worldwide by invading species, which has been one of the frequent causes of biodiversity loss. The invader may cause extinctions of vulnerable native species through predation, grazing, competition and habitat alteration. Keywords: Daphnia lumholtzi, exotic species, neotropical, zooplankton. Espécie exótica de zooplâncton na planície de inundação do

Population densities in different sites are frequently observed to fluctuate synchronously, a phenomenon termed temporal coherence. The two main causes of temporal coherence are dispersal and the effects of a regional factor (Moran effect) that influence each of the populations similarly. If synchronous patterns are observed, it is possible to infer that there is a regional process (e.g., climate) exerting a uniform influence over the entire region. Here, we evaluate patterns of temporal coherence in total densities of zooplankton groups. Data were gathered at 11 sites in the Corumbá Reservoir (Central Brazil) between 1996 and 2000 (n = 27 months). These sites were distributed in the main channel, arms, and tributaries of the reservoir. Reservoir-wide correlations (as estimated by the average Spearman rank correlation between temporal trajectories of abundances) were low (-0.01, 0.06, 0.23, and 0.14 for cladocerans, copepods, rotifers, and testate amoebae, respectively). In general, high temporal coherence was detected only between geographically adjacent sites and/or between sites with similar limnological characteristics. Contrary to many recent studies, these results illustrate that, in a small geographic area (i.e., a single reservoir of approximately 65 km 2 ), local processes may override the effects of regional processes or dispersal. Moreover, they demonstrate that the lack of regional trajectories (i.e., time series of population densities with asynchronous patterns of fluctuation) should be considered in interpreting results obtained in longterm studies or monitoring programs based on a single site per ecosystem.

Iheringia, Série Zoologia, Porto Alegre, 101(1-2):75-84, 30 de junho de 2011 Impact of fish cage-culture on the community structure of zooplankton... ABSTRACT. We investigated the impact of fish cage culture on the zooplankton community structure in a tropical reservoir. We hypothesized that community abundance is greater near cages and increases over time due to the increase in food availability. Samplings were performed near, upstream and downstream from net cages, and before and after net cage installation. The abundance of zooplankton increased 15 days after the experiment was set up, followed by a reduction and finally increased. Rotifer abundance showed significant differences among sites (p<0.05) and sampling periods (p<0.001). Significant differences were also observed in total zooplankton and cladoceran abundance (p<0.001). The spatial and temporal variation of the physical and chemical variables were indirectly correlated with the structure and dynamic of the zooplankton community, as they indicated the primary production in the environment. Our hypothesis was rejected, since the zooplankton was abundant at the reference site. Only rotifers showed higher abundance near cages, due to the influence of food availability. Community dynamics during the experiment was also correlated to food availability. Our results suggest an impact of fish farming on the zooplankton community. Impact of fish cage-culture on the community structure of zooplankton in a tropical reservoirKEYWORDS. Aquaculture, tilapia, environmental impact.RESUMO. Impacto da piscicultura em tanques-rede na comunidade zooplanctônica em um reservatório tropical. O objetivo deste estudo foi investigar o impacto da piscicultura em tanques-rede sobre a estrutura da comunidade zooplanctônica em um reservatório tropical. Acredita-se que a abundância do zooplâncton é maior perto dos tanques-rede e aumenta ao longo do tempo devido ao aumento da disponibilidade de alimento. As coletas foram realizadas próximo aos tanques-rede, bem como a montante e a jusante dos mesmos, antes e após a instalação dos tanques. A abundância do zooplâncton aumentou 15 dias depois da instalação dos tanques, seguida por uma redução e posterior aumento no fim do experimento. A abundância dos rotíferos apresentou diferenças significativas entre os pontos (p<0,05) e períodos de amostragem (p<0,001). Diferenças significativas também foram observadas para a abundância do zooplâncton total e de cladóceros (p<0,001). A variação espacial e temporal das variáveis físicas e químicas apresentou uma relação indireta com a estrutura e dinâmica da comunidade zooplanctônica, pois essa variação indicou a produção primária no ambiente. A hipótese foi rejeitada, pois o zooplâncton foi mais abundante no ponto de controle. Apenas os rotíferos apresentaram maior abundância perto dos tanques, devido à influência da disponibilidade de alimento. No entanto, a dinâmica da comunidade durante o experimento também foi relacionada com a disponibilidade de alimento. Os resultados sugerem o impacto da pi...

Cyclopid copepods from samples of fauna associated with aquatic macrophytes and plancton obtained in lotic and lentic environments were obtained from the upper Paraná River floodplain (in the states of Paraná and Mato Grosso do Sul, Brazil). Macrophytes were collected in homogeneous stands and washed. Plankton samples, taken from the water column surface and bottom, were obtained using a motor pump, with a 70 µm mesh plankton net for filtration. Twelve taxa of Cyclopidae were identified. Among them, Macrocyclops albidus albidus, Paracyclops chiltoni, Ectocyclops rubescens, Homocyclops ater, Eucyclops solitarius, Mesocyclops longisetus curvatus, Mesocyclops ogunnus, and Microcyclops finitimus were new finds for this floodplain. Eight species were recorded exclusively in aquatic macrophyte samples. Among these species, M. albidus albidus and M. finitimus presented greatest abundances. Only four species were recorded in plankton samples, and Thermocyclops minutus and Thermocyclops decipiens are limited to this type of habitat. Among these four species, T. minutus is the most abundant, especially in lentic habitats.Key words: Cyclopidae, taxonomy, phytophyle fauna, zooplankton, Paraná River. RESUMO Cyclopidae (Crustacea, Copepoda) da planície de inundação do alto rio Paraná, BrasilForam obtidos copépodes cyclopídeos de amostras de fauna associadas a macrófitas aquáticas e plâncton de ambientes lóticos e lênticos da planície de inundação do alto rio Paraná (nos Estados do Paraná e Mato Grosso do Sul). As amostras foram coletadas em bancos homogêneos e lavadas. As amostras de plâncton, tomadas à superfície e fundo da coluna de água, foram obtidas com o auxílio de uma motobomba, utilizando-se uma rede de plâncton de abertura de malha de 70 µm para filtração.

Fluctuations in temporal and spatial abundance are remarkable features of all animal populations. Regional synchrony of local population dynamics has been verified in several studies. This study investigated the existence of coherent patterns in temporal fluctuations of the principal testate amoebae population abundance in plankton from the upper Paraná river floodplain in Brazil. Testate amoebae sampling was carried out every three months, from February 2000 to November 2002, and twice in 2003. Sampling occurred in 12 environments associated with three different rivers. Samples were obtained at the subsurface of the pelagic region, using a motorized pump and a 68 µm mesh plankton net. Ninety-three testate amoebae species from eight families were identified. The families Difflugiidae, Arcellidae, and Centropyxidae had the greatest number of species. Arcella conica, A. discoides, A. vulgaris, Centropyxis aculeata, C. ecornis, Difflugia gramen, D. pseudogramen and Cucurbitella dentata were the most abundant species, and they were chosen for spatial synchrony analysis. No coherent pattern of abundance fluctuation was found, in any of the floodplain environments studied. Nevertheless, when analyzing only the channels, spatial synchrony was observed to Centropyxis ecornis. Mantel tests showed that the synchrony level, as identified by Spearman and Pearson correlations, was not correlated to geographic distance between environments. We conclude that regional factors in the Upper Paraná River floodplain are not the main determinants of the population dynamics of testate amoebae. The high floodplain heterogeneity seems determine a great relevance of local factors.

The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents.

ABSTRACT. The zooplankton community presents stochastic temporal fluctuation and heterogeneous spatial variation determined by the relationships among the organisms and environmental conditions. We predicted that the temporal and spatial zooplankton distribution is heterogeneous and discrete, respectively, and that the daily variation of most abundant species is related to environmental conditions, specifically the availability of resources. Zooplankton samples were collected daily at three sampling stations in a lateral arm of the Rosana Reservoir (SP/PR). The zooplankton did not present significant differences in abundance and evenness among sampling stations, but the temporal variation of these attributes was significant. Abiotic variables and algal resource availability have significantly explained the daily variation of the most abundant species (p<0.001), however, the species distribution makes inferences on biotic relationships between them. Thus, not only the food resource availability is influential on the abundance of principal zooplankton species, but rather a set of factors (abiotic variables and biotic relationships). KEYWORDS.Temporal variation, rotifers, microcrustaceans, coexistence, competition. RESUMO. Variação diária da abundância e equitabilidade do zooplâncton no reservatório de Rosana, Brasil: inferências bióticas e abióticas.A comunidade zooplanctônica apresenta flutuação temporal estocástica e variação espacial heterogênea que são determinadas pelas relações entre os organismos e condições ambientais. Acredita-se que a distribuição temporal e espacial do zooplâncton seja heterogênea e discreta, respectivamente; e que a variação diária das espécies mais abundantes está relacionada às condições ambientais, principalmente, disponibilidade de recursos. As amostras de zooplâncton foram coletadas diariamente em três estações de amostragem em um braço lateral do reservatório de Rosana (SP/PR). O zooplâncton não apresentou diferenças significativas na abundância e equitabilidade entre as estações de amostragem, no entanto, a variação temporal desses atributos foi significativa. As variáveis abióticas e a disponibilidade de recurso algal explicou significativamente a variação diária das espécies mais abundantes (p<0,001), entretanto, a distribuição das espécies faz inferências sobre relações bióticas entre elas. Assim, não só a disponibilidade de recurso alimentar é influente na abundância das principais espécies zooplanctônicas, mas sim um conjunto de fatores (variáveis abióticas e relações bióticas).