AIM: The main objective of the study was to evaluate the limnological characteristics of rivers flowing through urban and rural areas in the upper Uruguay River basin in western Santa Catarina (SC), Brazil. METHODS: Sampling sites in the tributaries were selected along the longitudinal gradient and the different use of the soil in adjacent areas. Samples were collected bimonthly from March 2005 to August 2006. The following were analysed: depth, pH, electrical conductivity, dissolved oxygen concentration (DO), water temperature, chemical oxygen demand (COD), total alkalinity, ammonia, nitrite, nitrate and phosphorus were analysed. RESULTS: In most of the rivers analysed, we found a continuum from the spring to the river mouth that was characterised by a gradual increase in electrical conductivity, COD, phosphorus, alkalinity, nitrite and nitrate. However, an alteration from this pattern was found in rivers passing through urban areas. This deviation was due to high organic matter input poured into the rivers from these areas. CONCLUSIONS: Degraded riparian forest was observed along most of the bodies of water, which facilitates the entry of pollutants. Although the studied area suffers from intense farming activity (agriculture and livestock) and has the highest concentration of swine livestock in the country, the rivers that were most altered from their natural state were those that were influenced by sewage and industrial effluents from urban development.
The discontinuity in rivers caused by the construction of reservoirs disrupts the longitudinal gradient and decreases the natural connectivity of lotic systems. We evaluated the dynamics of Reynolds functional groups (RFGs) in response to the formation of a subtropical reservoir, in relation to the environmental changes between the pre-and post-impoundment periods. We hypothesized that the disruption of longitudinal connectivity and the changes in the light and mixing regime after the impoundment would directly influence the phytoplankton functional structure. Significant changes in the light and mixing regimes were observed after the impoundment, with the formation of a lacustrine zone, influencing the dynamics of RFGs. Fourteen RFGs were recorded. RFG C (diatoms) dominated in the pre-impoundment period. In the post-impoundment period, RFGs C, P (diatoms), and J (chlorophyceans) codominated with the highest mean values of biovolume. RFGs MP, N, H1, W2, F, E, A, W1, B, X1, and S1 contributed relatively little to the biovolume, although with higher values in the post-impoundment period. RFGs F and S1 were recorded only after the impoundment. This study revealed the important roles of physical processes and nutrients in the spatial and seasonal gradient, and in the selection of phytoplankton functional groups in a subtropical reservoir.
This paper reports the alpha and beta diversity of phytoplankton communities of two streams differing in land use. We analyzed which environmental conditions affect diversity of the phytoplankton communities and tested the hypothesis that stream stretches protected by forests will have lower species richness, whereas higher beta-diversity would occur among the non-protected stretches. Samples were taken quarterly, from February to November 2012, in nine stretches, including four non-protected stretches, two partially protected stretches and three totally forest-protected stretches. Eleven abiotic variables and their coefficients of variation were analyzed. Phytoplankton was analyzed for species richness (alpha diversity), frequency of occurrence and beta-diversity. Species richness was calculated by first and second order jackknife indexes. Biotic data were submitted to Sørensen similarity analysis. A total of 429 infrageneric taxa were reported, representing 88% of the estimated expected species richness. The phytoplankton composition was typical for lotic environments with high richness values of Bacillariophyceae (66.0%). High phytoplankton richness values occurred in all the sampled stretches, even though beta-diversity was moderate and indicated similarity between the sampled stretches, therefore only a part of the original hypothesis was corroborated.
The first studies of Leptophlebiidae in the Santa Catarina State, Southern Brazil, dated from 1920. Since then, not much is known about the family (even to the Order Ephemeroptera) to the State. The main goal of this study was to survey fauna of Leptophlebiidae in the Santa Catarina State based on nymphs. The material was obtained from the collection deposited at the Laboratório de Pesquisa em Ecologia e Química of the Universidade Comunitária da Região de Chapecó, besides additional specimens collected between 2008 and 2009. Occurrences were plotted in the hydrograph map of Santa Catarina State, with one map for each genus. The Leptophlebiidae nymphs were recorded in 26 aquatic environments that included small streams and rivers. We identified 24 morphotypes distributed in 12 genera. Number of genera in the Western of Santa Catarina increased from eight to 15. Thraulodes, Ulmeritoides and Homothraulus presented higher frequency of occurrence in the region. Leentvaaria and Hermanella were associated to regions well conserved such as in the Araucaria forest. Needhamella and Segesta were related mainly to Irani River.
In regions where there is intense polluting activity, a greater availability of metals in water impounded by dams increases the availability and contamination of the fauna and flora. Thus, we assessed the accumulation of metals in muscle and gills of fish of different trophic levels in the area of influence of Foz do Chapecó hydroelectric plant on the Uruguai river. We analyzed the metals Pb, Cd, Cu, Cr, Mn, Zn, and Fe in Hypostomus isbrueckeri (cascudo), Pimelodus maculatus (mandi), and Salminus brasiliensis (dourado). We collected specimens from both upstream and downstream of the reservoir in February and March 2014. We also measured the allometric condition factor of the fish to determine their physiological status. Physical and chemical variables of the water were measured to determine the influence of these abiotic variables on the bioavailability of metals and on the condition factor of the fish. Gills had a higher concentration of metals than muscle. Hypostomus isbrueckeri and Pimelodus maculatus possessed high concentrations of metals, indicating greater bioaccumulation in benthic species. Only chromium in muscle varied significantly between upstream and downstream, with higher concentrations in H. isbrueckeri and P. maculatus upstream. Chromium contamination, however, did not change the condition factor, which did not vary between upstream and downstream for any of the studied species. We found no influence of abiotic variables of the water on the bioavailability of the metals in the environment. Although the data do not indicate trophic magnification, the different species react differently to environmental changes and their trophic plasticity makes it difficult to assign them to specific guilds.
In the present work based on material from several areas in Brazil, the species of Americabaetis represented in the country are revised. A new species, A. mecistognathus, sp. nov., is described based on nymphs from Santa Catarina, the male adult of A. labiosus Lugo-Ortiz & McCafferty is described, a key to the nymphs of the South American species is provided, whereas comments regarding the taxonomy and habitat distribution of the Brazilian species are presented.
O tamanho dos corpos d’água pode ser considerado o principal controlador das características físicas e químicas dos ambientes lóticos. Portanto, o tipo de substrato, a vazão, a composição orgânica e inorgânica e heterogeneidade de habitat possuem relação direta com a dimensão do ambiente lótico. Por sua vez essas características são determinantes na distribuição e diversidade da fauna de imaturos de Odonata. Neste contexto, testamos a hipótese de que diferentes dimensões de ambientes lóticos sustentam diversidade similar de imaturos de Odonata, entretanto, diferem quanto a sua composição. Assim, avaliamos a influência do tamanho do corpo d’água sobre fatores abióticos e estrutura da taxocenose de imaturos de Odonata. Realizamos cinco amostragens sazonais entre 2011 e 2012, no Parque Nacional das Araucárias, Santa Catarina, em oito ambientes, através de métodos quantitativos e qualitativos. Foram registrados 520 indivíduos de Odonata, distribuídas em oito famílias e 41 gêneros. Os ambientes foram evidentemente separados pela classificação dos rios. Os maiores valores de diversidade, riqueza e equitabilidade foram registrados nos córregos pequenos, ambientes com maior heterogeneidade de habitat, maior porcentagem de matéria orgânica e protegidos pela mata ciliar. Confirmou-se com esse estudo que a alta heterogeneidade de habitat em ambientes lóticos de baixas ordens influencia na diversidade, abundância e riqueza da fauna de Odonata. Outro fator determinante para os altos índices foi à integridade do local de estudo, favorecendo a proteção e ciclagem de nutrientes nos corpos d’água.
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