The number of citations that papers receive has become significant in measuring researchers' scientific productivity, and such measurements are important when one seeks career opportunities and research funding. Skewed citation practices can thus have profound effects on academic careers. We investigated (i) how frequently authors misinterpret original information and (ii) how frequently authors inappropriately cite reviews instead of the articles upon which the reviews are based. To reach this aim, we carried a survey of ecology journals indexed in the Web of Science and assessed the appropriateness of citations of review papers. Reviews were significantly more often cited than regular articles. In addition, 22% of citations were inaccurate, and another 15% unfairly gave credit to the review authors for other scientists' ideas. These practices should be stopped, mainly through more open discussion among mentors, researchers and students.

Diversity and biomass of native macrophytes are negatively related to dominance of an invasive Poaceae in Brazilian sub-tropical streamsA diversidade e a biomassa de macrófitas nativas são negativamente relacionadas com a dominância de uma Poaceae invasora em riachos sub-tropicais Abstract: Besides exacerbated exploitation, pollution, flow alteration and habitats degradation, freshwater biodiversity is also threatened by biological invasions. This paper addresses how native aquatic macrophyte communities are affected by the non-native species Urochloa arrecta, a current successful invader in Brazilian freshwater systems. We compared the native macrophytes colonizing patches dominated and non-dominated by this invader species. We surveyed eight streams in Northwest Paraná State (Brazil). In each stream, we recorded native macrophytes' richness and biomass in sites where U. arrecta was dominant and in sites where it was not dominant or absent. No native species were found in seven, out of the eight investigated sites where U. arrecta was dominant. Thus, we found higher native species richness, Shannon index and native biomass values in sites without dominance of U. arrecta than in sites dominated by this invader. Although difficult to conclude about causes of such differences, we infer that the elevated biomass production by this grass might be the primary reason for alterations in invaded environments and for the consequent impacts on macrophytes' native communities. However, biotic resistance offered by native richer sites could be an alternative explanation for our results. To mitigate potential impacts and to prevent future environmental perturbations, we propose mechanical removal of the invasive species and maintenance or restoration of riparian vegetation, for freshwater ecosystems have vital importance for the maintenance of ecological services and biodiversity and should be preserved.Keywords: signal grass, nvasive macrophytes, freshwater, biodiversity.Resumo: Juntamente com a exploração exacerbada, poluição, alteração de regime hidrológico e degradação de habitas as invasões biológicas são consideradas uma ameaça à biodiversidade dos ecossistemas aquáticos continentais. Nesse sentido, a Poaceae Urochloa arrecta é reconhecida como uma invasora bem sucedida em ambientes aquáticos brasileiros. Nós comparamos bancos de macrófitas dominados e não-dominados por esta invasora. Foram amostrados oito córregos no noroeste do Estado do Paraná (Brasil). Em cada córrego registramos a riqueza e a biomassa de macrófitas nativas em locais onde U. arrecta era dominante e em locais onde ela não dominava ou era ausente. Em sete dos oito locais onde U. arrecta dominava, não haviam macrófitas nativas. Assim, encontramos maiores riqueza de espécies nativas, índice de Shannon e biomassa nativa nos locais não dominados por U. arrecta com relação aos locais dominados. Apesar da dificuldade em se extrair conclusões sobre as causas dessas diferenças, inferimos que a elevada biomassa da invasora pode ser a principal fonte de altera...

Summary Biotic resistance theory predicts that the presence of a species‐rich native community is able to inhibit the establishment of invasive species. On the other hand, disturbed environments, for example, through eutrophication, tend to be more easily invaded. We investigated the effect of biotic resistance on the establishment success of the aquatic grass Urochloa arrecta in nutrient‐enriched and non‐enriched mesocosms so as to test the hypothesis that the effects of biotic resistance on invader success depend on ecosystem trophic state. Invader success, measured as plant biomass and length, increased with nutrient enrichment in treatments without biotic resistance, whereas there was no difference between the success of the invader in enriched or non‐enriched mesocosms in the presence of biotic resistance. Our results suggest that eutrophication enhanced the resistance offered by the native community and thereby reduced the establishment of invaders. The results underscore the importance of native communities as biotic filters to invasion, especially in environments that are subjected to anthropogenic impacts such as nutrient enrichment.

This study investigated the structure of the Oligochaeta and Chironomidae assemblages associated with monospecific stands of two submerged macrophyte species: Egeria najas and Hydrilla verticillata. Samplings were carried out in Leopoldo Backwater and Paraná river, in August 2008. To assess the structure of Oligochaeta and Chironomidae assemblage in each macrophyte we calculated: species density, richness, diversity, and evenness. A detrended correspondence analysis (DCA) was used to summarize Oligochaeta and Chironomidae assemblages composition. The highest values of species density and richness for the two groups were recorded in H. verticillata. Although there were no significant differences in density, richness and Shannon diversity, the assemblage composition of these groups was significantly different between plant species. These results suggest that despite being a recent colonizer in the upper Paraná river habitats, the non-native species H. verticillata seems to provide favorable conditions for the establishment of native assemblages of Chironomidae and Oligochaeta. Moreover, differences in the species composition of Oligochaeta and Chironomidae arose from peculiar characteristics of each plant, as attached microorganisms and organic matter, so that other factors, rather than plant architecture can also influence the assemblage of these groups.

Foram empregadas técnicas de espectroscopia de fl uorescência e UV-VIS para investigar a principal fonte de matéria orgânica dissolvida (MOD) em diferentes ambientes da planície de inundação do alto rio Paraná. As relações de absorvância/carbono orgânico dissolvido (A/COD), intensidade de fl uorescência/carbono orgânico dissolvido (IF/COD), as intensidades de fl uorescência emitidas (FR) e o comprimento de onda de máxima intensidade (PW) foram utilizadas para distinguir a principal fonte da MOD. Os valores de FR, PW e A 285 / COD indicam que a predominância da fonte está relacionada com a infl uência do rio principal. Os espectros das amostras de água dos rios Baía, Ivinheima, lagoa dos Patos e lagoa Carão foram semelhantes aos do ácido fúlvico extraído do solo do entorno desses ambientes, indicando que a principal fonte de MO é pedogênica. Já nos ambientes com infl uência do rio Paraná, ocorre a predominância de MO autóctone. Palavras-chave: Fluorescência, UV-VIS, matéria orgânica dissolvida, planície de inundação. ABSTRACT SPECTROSCOPIC CHARACTERIZATION OF DISSOLVED ORGANIC MATTER IN THE UPPER PARANÁ RIVER FLOODPLAIN. In the present study fl uorescence and UV-VIS techniques were employed to determine the main source of dissolved organic matter (DOM) in different environments of the Upper Paraná River fl oodplain. The following relationships were analyzed: absorbance/dissolved organic carbon (A/DOC), fl uorescence intensity/dissolved organic carbon (FI/DOC), fl uorescence ratio (FR), and peak wavelength with the highest intensity (PW). The obtained FR, PW and A 285 /DOC values indicate that most DOM comes from the main river. The obtained spectra of water samples from the different analyzed sites were similar to that of fulvic acid (FA) extracted from soil from the surroundings of these same areas, thus indicating the source of DOM is chiefl y pedogenic. Regarding environments infl uenced by the Paraná River, most DOM proved to be autochthonous.

A matéria orgânica nos ambientes aquáticos exerce papel fundamental em diversos processos ecológicos sendo a decomposição uma das principais rotas de ciclagem da matéria. A contribuição das macrófi tas aquáticas se dá principalmente pela produção de detritos, já que seu carbono é de difícil assimilação direta pela maioria dos organismos. As análises espectroscópicas tem se constituído numa ferramenta importante no estudo da matéria orgânica, pois permitem uma distinção razoável entre materiais lábeis e refratários. A partir da comparação dos espectros de fl uorescência da matéria orgânica resultante de um experimento de decomposição de macrófi tas aquáticas e da matéria orgânica da água, do sedimento e do solo de ambientes da planície de inundação do alto rio Paraná, estimou-se a contribuição das macrófi tas para o reservatório de carbono nesses ambientes. Foi possível verifi car maior contribuição da decomposição nos ambientes oligotrófi cos conectados ao rio Paraná, enquanto que nos ambientes conectados aos rios Ivinheima e Baia predominam matéria orgânica alóctone, principalmente substâncias húmicas pedogênicas. Palavras-chave: Macrófi tas aquáticas, fl uorescência, decomposição, planície do rio Paraná ABSTRACT CONTRIBUTION TO DISSOLVED ORGANIC MATTER BY DECOMPOSITION OF AQUATIC MACROPHYTES, Eichhornia azurea. Organic matter plays a fundamental role in many ecological processes and decomposition is among the main cycling routes of organic matter. The decomposition of aquatic macrophytes generates much debris, since the carbon of these algae is not easily assimilated by other organisms. Spectroscopic analyses are important in organic matter studies, because it enables satisfactory distinction between labile and refractory materials can be obtained. Through comparing the fl uorescence spectrum of the organic debris generated by a decomposing macrophyte with those of water, sediment, and soil samples from the Upper Paraná River fl oodplain water bodies, we were able to estimate the contribution of decomposition to local carbon cycles. The results revealed a higher contribution of decomposition to the oligotrophic environments connected with the Paraná River, while some water bodies connected with the rivers Ivinheima and Baia showed a greater participation of allochthonous organic matter, mainly derived from humus.

AIM: Our aim was to identify dissolved organic matter (DOM) main sources in environments of the Upper Paraná River floodplain and their seasonal and spatial variation. METHODS: Ultraviolet-visible and fluorescence spectroscopy were utilized. The samples were obtained from November 2007 to September 2008 in six lakes of the floodplain. RESULTS: DOM quality differs among environments and also between rainy and dry season. The environments connected with Paraná River showed a high variation on the allochthonous/autochthonous proportion. Aquatic macrophytes might represent an important contribution to DOM in Garças and Osmar lakes. CONCLUSIONS: In general, environments connected to Paraná River have a greater influence of autochthonous DOC, while the others are most influenced by allochthonous inputs.

Since the introduction of the Microbial Loop concept, many studies aimed to explain the role of bacterioplankton and dissolved organic carbon (DOC) in aquatic ecosystems. Paraná River floodplain system is a very complex environment where these subjects were little explored. The aim of this work was to characterize bacterial community in terms of density, biomass and biovolume in some water bodies of this floodplain and to verify its temporal variation and its relation with some limnological variables, including some indicators of DOC quality, obtained through Ultraviolet-visible (UV-VIS) and fluorescence spectroscopic analysis. Bacterial density, biomass and biovolume are similar to those from other freshwater environments and both density and biomass were higher in the period with less rain. The limnological and spectroscopic features that showed any relation with bacterioplankton were the concentrations of N-NH4 and P-PO4, water transparency, and some indicators of DOC quality and origin. The analysis of these relations showed a possible competition between bacterioplankton and phytoplankton for inorganic nutrients and that the DOC used by bacterioplankton is labile and probably from aquatic macrophytes.