Juliana Déo Dias

Biodiversity of zooplankton communities in the Upper Paraná River floodplain: interannual variation from long-term studies

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.

Floods control the influence of environmental gradients on the diversity of zooplankton communities in a neotropical floodplain

Floodplains show a high biodiversity due to their spatial heterogeneity and temporal variability, which are governed by environmental dynamics resulting from the flood pulse. We evaluated the importance of this driving force, the flood pulse, in the structuring of environmental gradients that influence species diversity in a neotropical floodplain. Gamma (γ) and alpha (α) zooplankton diversities were higher in the year with a typical flood pulse (2010), indicating that flood dynamics contributed to high diversity component values. We found significant relationships between α- and β-diversity and local environmental gradients, indicating that in years with a flood pulse, environmental filters might be the dominant mechanisms that structure the zooplankton community. Additive partitioning of γ-diversity showed that even in 2000 with atypical flood conditions, zooplankton diversities showed non-random patterns of spatial distribution and temporal variation in the floodplain. Our results indicate that the driving force of a floodplain can determine the spatial distribution of α- and β-diversity of aquatic communities owing to its primary effect on environmental filters. Therefore, if human activities that influence this driving force, such as water regulation, affect those environmental filters, floodplain biodiversity may decline.

Temporal nestedness in Chironomidae and the importance of environmental and spatial factors in species rarity

Biological communities are composed of a few common and many rare species. An understanding of the mechanisms that govern the distribution of these species is fundamental to knowledge regarding community ecology. Our hypothesis is that chironomid larvae follow a nested distribution in relation to hydrological periods in Neotropical floodplain lakes, whereby the flood period composition is a subset of the drought periods with a predominance of common species. We collected samples from 18 lakes in 2011 in a flood month and three drought months. The community followed a nested distribution where the spatial factors were more important for rare and common species during the flood and for the common species during all months. Thus, with the increasing connectivity and similarity of environments during the flood, neutral processes, as the dispersal, would govern the community. Conversely, environmental factors were more important for rare species in the drought, which suggest that these species are more specialists, largely influenced by niche-related processes. Thus, our study emphasizes the complexity of biological communities specifically concerning how environmental, spatial, and temporal factors influence community dynamics among species groups.

Impact of reservoirs on zooplankton diversity and implications for the conservation of natural aquatic environments

Reservoirs are intermediate ecosystems between rivers and lakes. These ecosystems break up the landscape by forming artificial lakes connected by rivers and change important ecological processes of lotic ecosystems (e.g. organic matter production and nutrient cycling) and thus have direct effects on aquatic biodiversity. We test the hypothesis that damming water courses exerts a negative effect on the zooplankton community by decreasing the alpha diversity. Samplings were conducted in 30 reservoirs and 29 natural lakes in the Neotropics, during two hydrological periods (dry and rainy) in 2001. The study analysed differences in alpha diversity, the number of rare, accessory and constant species, and species composition between the types of lakes. Alpha diversity was significantly higher in natural lakes and species composition differed between natural lakes and reservoirs. Zooplankton alpha diversity was positively related to total phosphorus (best model), indicating that productive environments (natural lakes) gather more species. Our results suggest that reservoirs have negative effect on community structure, whereas natural lakes have an important ecological function for biodiversity conservation because they are refuges for biodiversity.

Impact of fish cage-culture on the community structure of zooplankton in a tropical reservoir

O objetivo deste estudo foi investigar o impacto da piscicultura em tanques-rede sobre a estrutura da comunidade zooplanctonica em um reservatorio tropical. Acredita-se que a abundância do zooplâncton e maior perto dos tanques-rede e aumenta ao longo do tempo devido ao aumento da disponibilidade de alimento. As coletas foram realizadas proximo aos tanques-rede, bem como a montante e a jusante dos mesmos, antes e apos a instalacao dos tanques. A abundância do zooplâncton aumentou 15 dias depois da instalacao dos tanques, seguida por uma reducao e posterior aumento no fim do experimento. A abundância dos rotiferos apresentou diferencas significativas entre os pontos (p<0,05) e periodos de amostragem (p<0,001). Diferencas significativas tambem foram observadas para a abundância do zooplâncton total e de cladoceros (p<0,001). A variacao espacial e temporal das variaveis fisicas e quimicas apresentou uma relacao indireta com a estrutura e dinâmica da comunidade zooplanctonica, pois essa variacao indicou a producao primaria no ambiente. A hipotese foi rejeitada, pois o zooplâncton foi mais abundante no ponto de controle. Apenas os rotiferos apresentaram maior abundância perto dos tanques, devido a influencia da disponibilidade de alimento. No entanto, a dinâmica da comunidade durante o experimento tambem foi relacionada com a disponibilidade de alimento. Os resultados sugerem o impacto da piscicultura em tanques-rede na comunidade zooplanctonica.

Drivers of phytoplankton richness and diversity components in Neotropical floodplain lakes, from small to large spatial scales

Understanding the distribution patterns of species and how spatial and environmental factors drive the structure of communities is crucial to the preservation of biodiversity. We evaluate, during the low and high water periods, the phytoplankton diversity in lakes of four Brazilian floodplain systems (FPs): Amazon, Araguaia, Pantanal, and Paraná. We hypothesized that (i) species variation/replacement among floodplains (β2) is the predominant mechanism in shaping phytoplankton gamma diversity; (ii) the variation in phytoplankton taxonomic composition within each floodplain (β1) is mainly governed by local environmental conditions due to the high dispersal ability of phytoplankton at small spatial scales; and (iii) variation in the phytoplankton taxonomic composition among floodplains (β2) is mainly influenced by dispersal limitation. Variation partitioning was used to evaluate the influence of spatial and environmental factors on species richness. Higher γ diversity was found in the Araguaia and Amazon FPs. The high contribution of β2 (large scale) to γ diversity revealed the high degree of environmental heterogeneity in each floodplain. β1 (small scale) was more influenced by environmental variables, and β2 by both spatial and environmental factors. Our findings showed that γ diversity was explained by the interaction between the two factors, and that these processes influencing variation were scale dependent.

Hydrological dynamics drives zooplankton metacommunity structure in a Neotropical floodplain

The maintenance of biodiversity in dynamic landscapes can be explained through the unifying concept of the metacommunity, an ecological system with a changing structure that arises from both the biotic features of its component species and from changing temporal processes. We evaluated the relative importance of environmental factors and spatial factors on the structure of metacommunities of zooplankton in a Neotropical floodplain system, in relation to hydrological dynamics and potential connections among lakes. Zooplankton was sampled from 16 to 22 shallow lakes during droughts and floods in two hydrologically contrasting years. Copepods appeared to be more limited by their dispersal potential, while testate amoebae and rotifers seemed to be controlled mostly by environmental variables. These findings stress the importance of the species sorting metacommunity paradigm for groups with the smallest propagules and adult body sizes. The importance of environmental factors rather than spatial factors was apparent during floods, likely due to the facilitation of animal dispersal by floods. Our results demonstrate that the importance of these factors depends on both the functional traits of major zooplankton groups and the hydrological dynamics of the region.

Length-weight regressions of the microcrustacean species from a tropical floodplain

AIM: This study presents length-weight regressions adjusted for the most representative microcrustacean species and young stages of copepods from tropical lakes, together with a comparison of these results with estimates from the literature for tropical and temperate regions; METHODS: Samples were taken from six isolated lakes, in summer and winter, using a motorized pump and plankton net. The dry weight of each size class (for cladocerans) or developmental stage (for copepods) was measured using an electronic microbalance; RESULTS: Adjusted regressions were significant. We observed a trend of under-estimating the weights of smaller species and overestimating those of larger species, when using regressions obtained from temperate regions; CONCLUSION: We must be cautious about using pooled regressions from the literature, preferring models of similar species, or weighing the organisms and building new models.

Fish larvae diversity in a conservation area of a neotropical floodplain: influence of temporal and spatial scales

The diversity of fish larvae in floodplain environments exhibits spatial and temporal variations since fish have different ontogenetic requirements, and is influenced by their reproductive period. In order to evaluate how the diversity of fish larvae is structured in different temporal and spatial scales in the sub-basin of the Ivinhema River, Upper Paraná River floodplain (MS, Brazil), we performed monthly samplings in two reproductive periods (2010/2011 and 2011/2012). Variation in alpha (α) diversity was evaluated through a nested ANOVA, while beta (β) diversity was evaluated with distance-based tests for the homogeneity of multivariate dispersions (PERMDISP). Additive partitioning of diversity was used to verify the relative contribution of each scale to gamma (γ) diversity. The first reproductive period showed higher intensity and duration of flooding, which favored a higher γ diversity. Alpha and beta diversities also varied among the different habitats, each one being occupied by species with distinct reproductive strategies. Components β1 (variation among months) and β3 (variation among habitats) significantly explained γ diversity in both reproductive periods, indicating that more intense floods favor reproduction and increase diversity of fish larvae. This study reinforces the importance of temporal and spatial scales in the maintenance of fish larvae diversity in floodplains.

Erratum to: Effects of fish farming on plankton structure in a Brazilian tropical reservoir

On page 10, column 1, lines 9–10, please replace ‘‘according to the Ordinance from the the Brazilian Health Ministry 518/2004 (Brasil, 2004).’’ by ‘‘according to recommendations from the Brazilian Health Ministry (Brasil, 2003).’’ Please delete the reference: ‘‘Brasil. 2004. Ministerio da Saude. Portaria no. 518. Estabelece os procedimentos e responsabilidades relativos ao controle e vigilância da qualidade da agua para consumo humano e seus padroes de potabilidade, e da outras providencias.’’ and replace it by: ‘‘Brasil. 2003. Cianobacterias toxicas na agua para consumo humano na saude publica e processos de remocao em agua para consumo humano. Ministerio da Saude. Fundacao Nacional de Saude, Brasilia, DF.’’