Experimental evaluation of microplastic consumption by using a size-fractionation approach in the planktonic communities.

The increasing amount of plastic particles introduced into continental aquatic environments has drawn the attention of researchers around the globe. These particles can be assimilated by a wide range of aquatic organisms, from microorganisms to fish, causing detrimental effects on trophic webs. Using an experimental approach, we investigated the effect of microplastic particles of different sizes on the planktonic trophic chain by sampling natural plankton communities from a lake located in the Upper Paraná River floodplain, Brazil. Zooplankton samples were collected at the beginning of the experiment and after 36 h of incubation. Microplastic particles (MP) samples were taken every 12 h. The effect of MP particle consumption from the control and treatment groups indicates significant effects by all plankton size fractions (p < 0.05). We demonstrated that the presence of MP particles can significantly affect the trophic web, furthermore, we detected the effect of higher consumption effect of smaller size MP particles. This study suggest that the largest MP consumption effects come from the lower trophic levels of the trophic chain, such as protists. The competitive effect of large predators is a crucial factor in controlling the abundance of populations, and although they did not directly consume MP particles, they ingest them indirectly through prey capable of absorbing these compounds in the environment. Our findings warn that MP particles enter the food webs of tropical regions when exposed to these pollutants, and that the presence of these particles should not be neglected when studying freshwater ecosystems.

Non-native fishes homogenize native fish communities and reduce ecosystem multifunctionality in tropical lakes over 16 years.

Non-native species are considered a major global threat to biodiversity, and their expansion to new ecosystems has recently increased. However, the effect of non-native species on ecosystem functioning is poorly understood, especially in hyperdiverse tropical ecosystems of which long-term studies are scarce. We analyzed the relationship between richness, biomass, and ß-diversity of non-native and native fishes during 16 years in five hyperdiverse tropical shallow lakes. We further elucidated how an observed increase in the proportion of richness, biomass, and ß-diversity of non-native over native fishes affect crucial multifunctional processes of lakes (decomposition, productivity). We found a general positive relationship between the richness and biomass of non-native and native fishes. However, the slope of this relationship decreased continuously with time, displaying an increase in non-native species richness and a decrease in native species richness over time. We also detected a negative relationship between the ß-diversity of non-native and native fishes over time. Moreover, the increase in the non-native:native ratio of species richness, biomass, and ß-diversity over time decreased ecosystem multifunctionality. Our results suggest that non-native fishes caused a homogenization of the native fish species over time, resulting in impoverishment of ecosystem multifunctionality; in part because non-native fishes are less productive than native ones. Therefore, focus on long-term effects and use of multiple biodiversity facets (α- and ß-diversity) are crucial to make reliable predictions of the effects of non-native fish species on native fishes and ecosystem functioning.

Main predictors of periphyton species richness depend on adherence strategy and cell size.

Periphytic algae are important components of aquatic ecosystems. However, the factors driving periphyton species richness variation remain largely unexplored. Here, we used data from a subtropical floodplain (Upper Paraná River floodplain, Brazil) to quantify the influence of environmental variables (total suspended matter, temperature, conductivity, nutrient concentrations, hydrology, phytoplankton biomass, phytoplankton species richness, aquatic macrophyte species richness and zooplankton density) on overall periphytic algal species richness and on the richness of different algal groups defined by morphological traits (cell size and adherence strategy). We expected that the coefficients of determination of the models estimated for different trait-based groups would be higher than the model coefficient of determination of the entire algal community. We also expected that the relative importance of explanatory variables in predicting species richness would differ among algal groups. The coefficient of determination for the model used to predict overall periphytic algal species richness was higher than the ones obtained for models used to predict the species richness of the different groups. Thus, our first prediction was not supported. Species richness of aquatic macrophytes was the main predictor of periphyton species richness of the entire community and a significant predictor of the species richness of small mobile, large mobile and small-loosely attached algae. Abiotic variables, phytoplankton species richness, chlorophyll-a concentration, and hydrology were also significant predictors, depending on the group. These results suggest that habitat heterogeneity (as proxied by aquatic macrophytes richness) is important for maintaining periphyton species richness in floodplain environments. However, other factors played a role, suggesting that the analysis of species richness of different trait-based groups unveils relationships that were not detectable when the entire community was analysed together.

Cytotoxicity and genotoxicity of Guaribas river water (Piauí, Brazil), influenced by anthropogenic action.

In general, tropical rivers have a great impact on human activities. Bioaccumulation of toxins is a worldwide problem nowadays and has been, historically, overlooked by the supervisory authorities. This study evaluated cytogenotoxic effects of Guaribas river (a Brazilian river) water during dry and rainy seasons of 2014 by using the Allium cepa test system. The toxicogenetic variables, including root growth, mitotic index, and chromosomal aberrations, were analyzed in meristematic cells of A. cepa exposed to water samples taken from the up-, within, and downstream of the city Picos (state: Piauí). The physical-chemical parameters were also analyzed to explain water quality and possible anthropogenic action. Additionally, the presence of heavy metals was also analyzed to explain water quality and possible damaging effects on eukaryotic cells. The results suggest that the river water exerted cytotoxic, mutagenic, and genotoxic effects, regardless of the seasons. In addition, Guaribas river presented physico-chemical values outside the Brazilian laws, which can be a characteristic of human pollution (domestic sewage, industrial, and local agriculture). The genetic damage was positively correlated with higher levels of heavy metals. The pollution of the Guaribas river water may link to the chemical contamination, including the action of heavy metals and their impacts on genetic instability in the aquatic ecosystem. In conclusion, necessary steps should be taken into account for further toxicogenetic studies of the Guaribas river water, as it has an influence in human health of the same region of Brazil.

Physico-chemical and genotoxicity analysis of Guaribas river water in the Northeast Brazil.

River pollution in Brazil is significant. This study aimed to evaluate the physico-chemical and genotoxic profiles of the Guaribas river water, located in Northeast Brazil (State of Piauí, Brazil). The study conducted during the dry and wet seasons to understand the frequency of pollution throughout the year. Genotoxicity analysis was done with the blood of Oreochromis niloticus by using the comet assay. Water samples were collected from upstream, within and downstream the city Picos. The results suggest a significant (p < 0.05) genotoxic effect of the Guaribas river water when compared to the control group. In comparison to the control group, in the river water we found a significant increase in metals such as - Fe, Zn, Cr, Cu and Al. In conclusion, Guaribas river carries polluted water, especially a large quantity of toxic metals, which may impart the genotoxic effect.

Rotifer community structure along a stretch under the influence of dams in the Upper Paraná River floodplain / Estrutura da comunidade de rotíferos ao longo de um trecho sob a influência de barragens na planície de inundação do alto rio Paraná

The construction of reservoirs imposes substantial impact on freshwater ecosystems and changes the ecological aspects of the lotic system downstream of dams. We hypothesized an increasing dissimilarity between communities in the sampling sites according to increasing distance from the Porto Primavera Dam. In addition, we expect that the rotifer community in the last sampling site will be influenced more by environmental variables related to trophic status. Samplings were conducted under the water surface of ten sites on the Paraná River in August 2013. Environmental variables were also determined. The highest number of taxa belonged to families Brachionidae, Lecanidae and Trichocercidae. The most abundant species was observed to Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. The species dissimilarity between sampling sites, tested using the Sorensen index, showed high dissimilarity between sampling sites. Redundancy analysis indicated a significant relationship between environmental variables (total phosphorus and ammonia) and abundance of Brachionus calyciflorus and Keratella cochlearis, in the last sampling site. Our results suggest a greater dissimilarity between the rotifer communities according to increasing distance from the Porto Primavera Dam. In addition, a higher influence of the environmental variables related to trophic conditions was observed in the last sampling site, and influenced indirectly the occurrence and abundance of some rotifer species, due to increased availability of food resources, confirming the predicted hypothesis.

A construção de reservatórios impõe considerável impacto sobre os ecossistemas de água doce e altera os aspectos ecológicos do sistema lótico a jusante das barragens. A hipótese foi que ocorrerá maior dissimilaridade entre as comunidades nos pontos amostrados à medida que se afastam da barragem de Porto Primavera. Espera-se, ainda, que a comunidade de rotíferos do último ponto de amostragem seja mais influenciada pelas variáveis ambientais relacionadas à trofia. As amostragens foram realizadas à subsuperfície da região pelágica em dez pontos no rio Paraná no mês de agosto de 2013. As espécies mais abundantes foram Synchaeta oblonga, Keratella cochlearis, Brachionus calyciflorus. As variáveis ambientais também foram determinadas. O maior número de táxons registrados pertenceu às famílias Brachionidae, Lecanidae e Trichocercidae. A similaridade da composição de espécies calculada de acordo com o índice de Sorensen registrou elevada dissimilaridade entre os pontos amostrados. A análise de redundância constatou a relação significativa entre as variáveis ambientais (fósforo total e amônia) e a abundância de Brachionus calyciflorus e Keratella cochlearis, no último ponto de amostragem. Nossos resultados sugerem que ocorreu maior dissimilaridade entre as comunidades de rotíferos à medida que se afastam da barragem de Porto Primavera. Além disso, foi observada maior influência das variáveis ambientais relacionadas às condições tróficas no último ponto de amostragem, e influenciou indiretamente a ocorrência e abundância das espécies de rotíferos, por causa do aumento da disponibilidade de recursos alimentares, corroborando com a hipótese predita.

Advances in studies on testate amoebae (Arcellinida and Euglyphida): a scientometric approach / Avanços nos estudos sobre amebas testáceas (Arcellinida e Euglyphida): uma abordagem cienciométrica

Testate amoebae have a great potential for use in scientific researches due to their ecological characteristics such as abundance, wealth, and generation time. In this way, this study aimed to present a scientometric analysis to describe the evolution of the different advances in researches on testate amoebae and identify a temporal pattern in this evolution. The literature review was based on papers indexed by Thomson Reuters (www.isiwebofknowledge.com) and SciVerse Scopus (www.scopus.com). In total 562 papers were examined. Results showed a pattern of evolution in scientific studies, most with ecological approach with descriptive and predictive designs. At the global level, researches on testate amoebae progressed in both the number of articles published as well as in the areas studied, especially in Europe and North America. The low number of experimental studies and review articles can characterize the lack of more knowledge to be acquired, both from particular observations (descriptive studies) as well as the observations noted sufficiently predictive of work. In Brazil, studies with testate amoebae are still developing, concentrated in only some regions, but the increased number of studies in recent years allows the prediction of the same overall patterns of advance for Brazilian researches. Thus, we conclude that these organisms are being increasingly used as a tool response in ecological studies.

Amebas testáceas possuem grande potencial de utilização em pesquisas de caráter científico pelas suas características ecológicas como abundância, riqueza, e tempo de geração. Nesse sentido, o objetivo do presente estudo foi apresentar uma análise cienciométrica, a fim de descrever a evolução das diferentes abordagens nas pesquisas de tecamebas e identificar um padrão temporal nessa evolução. A revisão dos artigos científicos foi realizada com base nos artigos indexados pela base Thomson Reuters (www.isiwebofknowledge.com) e pela base SciVerse Scopus (www.scopus.com). Foram analisados 562 artigos científicos. Os resultados demonstraram um padrão de evolução nos trabalhos científicos, sendo a maioria de cunho ecológico com delineamentos descritivos e preditivos. Em âmbito global, as pesquisas com tecamebas apresentaram evolução tanto no número de artigos publicados bem como nas áreas estudadas, principalmente na Europa e América do Norte. O baixo número de trabalhos experimentais e de revisão pode caracterizar a falta de maiores conhecimentos a serem ainda adquiridos, tanto a partir das observações particulares (trabalhos descritivos) bem como das observações suficientemente constatadas dos trabalhos preditivos. No Brasil, as pesquisas com amebas testáceas ainda estão em processo de desenvolvimento, concentradas em apenas algumas regiões. Entretanto, o aumento no número de publicações nos últimos anos possibilita a previsão dos mesmos padrões de evolução globais para as pesquisas brasileiras. Assim, é possível concluir que esses organismos estão sendo cada vez mais utilizados como ferramenta resposta nos estudos ecológicos.

Passive zooplankton community in different environments of a neotropical floodplain / Comunidade zooplanctônica passiva em diferentes ambientes de uma planície de inundação neotropical

Zooplankton is able to respond promptly to environmental changes, producing resting forms in order to maintain populations when the conditions become unfavorable. The hatchling of the resting eggs was assessed in environments from the upper Paraná river floodplain, during the limnophase of 2008. We predicted that a higher production of these eggs and individuals' hatchling are observed at isolated lakes, during dried period. Sediment samples were obtained with a corer sampler. The resting eggs were sorted and kept in filtered water from the same environment, in the laboratory. We recorded the occurrence of 378 resting eggs, of which 122 individuals hatched (70 cladocerans and 52 rotifers). The highest number of hatchlings was verified for the isolated lakes (84 individuals), as well the shorter time for hatchling (2 days). The hatchlings occurred mainly in September, when we registered the lowest hydrologic level of Paraná river (2.40 m). Grimaldina brazzai presented the longest time for hatchling, 44 days; and Brachionus dolabratus and B. falcatus, the shortest time, 2 days. This result suggests that the longer residence time of the water, which did not allow a renewal of food resources and limnological conditions of the environment, caused a higher stress in the zooplankton.

O zooplâncton é capaz de responder prontamente às mudanças das condições ambientais produzindo formas de resistência, a fim de manter as populações quando essas condições se tornam desfavoráveis. A eclosão dos ovos resistência foi avaliada em diferentes ambientes da planície de inundação do alto rio Paraná, no período de limnofase em 2008. Foi pressuposto que ocorre uma maior produção desses ovos e de eclosões dos indivíduos nas lagoas fechadas, no período mais seco. As amostras do sedimento foram obtidas com um amostrador do tipo "corer". Os ovos de resistência foram triados e mantidos na própria água do ambiente filtrada, em temperatura ambiente. Foram triados 378 ovos de resistência, dos quais eclodiram 122 indivíduos (70 cladóceros e 52 rotíferos). Uma maior eclosão (91 indivíduos), e em um menor tempo (2 dias), foram observados nas lagoas fechadas. As eclosões ocorreram principalmente em setembro, quando o nível hidrológico do rio Paraná foi menor (2,40 m). Grimaldina brazzai apresentou o maior tempo de eclosão, 44 dias; e Brachionus dolabratus e B. falcatus, o menor tempo, 2 dias. Esse resultado sugere que o elevado tempo de residência da água, que não propiciou uma renovação dos recursos alimentares e das condições limnológicas no ambiente, foi o fator de estresse para o zooplâncton.

Effects of natural banks of free-floating plants on zooplankton community in a shallow subtropical lake in Southern Brazil

The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankton biomass and zooplankton community was tested. Second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. Three microhabitats were selected: free-floating plants, littoral area and open water. Results demonstrated that the effects of different microhabitats on phytoplankton biomass and physico-chemicals were not significant, indicating a weak influence of the plants. Zooplankton densities were higher in free-floating plants and littoral area, although the effect of microhabitats was weak for most of the predominant genera. The absence of free-floating plant effects on phytoplankton and physico-chemicals showed that it was not a factor influencing the microcrustacean distribution in the microhabitats. Low differences in densities of zooplankton among microhabitats and low abundance of large-bodied cladocerans led to reject the hypothesis that free-floating plants act as a refuge for zooplankton.

Relationship between the structure of zooplankton community and the water level in a floodplain lake from the Pantanal, Mato Grosso State, Brazil / Relação entre a estrutura da comunidade zooplanctônica e o nível da água em uma lagoa de inundação do Pantanal de Mato Grosso, Brasil

The hydrological condition of floodplain systems alters the structure and dynamic of aquatic communities. We suggest that the structure of zooplankton community changes according to the flood phases and connectivity. This study was carried out in a floodplain lake located in the Northern Pantanal (Brazil). Zooplankton density varied considerably over time, although the sampling stations presented similar densities. The densities ranged from 2,000 ind. m-3 in the high water phase to more than 2,300,000 ind. m-3 during the low water phase when the lake remains isolated. The densities of the groups also presented a temporal variation. Rotifers described the community mainly in the low water phase and microcrustaceans during the high water phase. Variations in the total zooplankton and groups densities were significantly correlated to the PCA 1 axis (negatively composed by water depth and positively by turbidity) and to the food availability (phytoplankton).

A condição hidrológica de sistemas inundáveis altera a estrutura e a dinâmica das comunidades aquáticas. Com isso, sugerimos que a estrutura da comunidade zooplanctônica se altera de acordo com as fases da inundação e conectividade. Este estudo foi realizado em uma lagoa de inundação da parte norte do Pantanal (Brasil). A densidade zooplanctônica variou consideravelmente ao longo do tempo, embora as estações amostrais apresentarem densidades similares. As densidades variaram de 2.000 ind. m-3 na fase de águas altas para mais de 2.300.000 ind. m-3 durante a fase de águas baixas quando a lagoa esteve isolada. As densidades dos grupos também apresentaram variação temporal. Os rotíferos foram relativamente mais importantes durante as águas baixas e os microcrustáceos durante a fase de águas altas. Variações na densidade do zooplâncton e grupos foram significativamente correlacionados com o eixo 1 da PCA (composta negativamente pela profundidade da água e positivamente com a turbidez) e a disponibilidade alimentar (fitoplâncton).