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a b s t r a c tDuring the high water season, the flooding reduces environmental heterogeneity in aquatic ecosystems of the Pantanal wetland. When the water level recedes, lakes and channels are formed as individual systems. Therefore, we expected the spatial heterogeneity during the low water phase resulting in changes on biological communities leading to high phytoplankton abundance, biomass and diversity within and between habitats. To test this hypothesis, we analyzed eight freshwater systems (five oxbow lakes, two channels, and the river) during the low water period. Phytoplankton biomass, abundance, diversity (alpha, beta, gamma) and diversity metrics as richness (species per sample), Shannon diversity (H ) and evenness were measured in all systems along with nutrient concentrations, zooplankton and bacteria abundances. We found 97 species as gamma diversity. The alpha diversity was unexpectedly low in comparison to most other South American floodplain systems (38 species in river, 24 in channels and 29 in lakes). Also, the systems are relatively similar in composition (beta diversity, 28%). Connectivity differences between systems highlighted differences in phytoplankton abundance and biomass (fresh weight) ranging from 1428 ind mL −1 (river) to 3710 ind mL −1 (lakes) and from 0.71 mg L −1 (river) to 2.9 mg L −1 (lakes), respectively. However, our results did not indicate significant differences in phytoplankton species richness between the systems during the low water. Our main conclusions are that local factors may be responsible for changes on phytoplankton community and the time of isolation during the low water phase was not sufficient to promote changes in phytoplankton diversity between the habitats.

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Abstract:The fish fauna of urban streams is still poorly known, it difficult to assess the effects of urbanization expansion on fish species composition, for this reason the aim of this study was to provide a checklist of species that compose the ichthyofauna of six urban streams, tributaries to the Vermelho River, upper Paraguay River Basin, Rondonópolis, Mato Grosso State, Brazil. The samples were performed with seine nets on a spatial gradient of 75 m, and with sieves for a period of 15 minutes in each site. A total of 56 species belonging to five orders, Characiformes, Siluriformes, Gymnotiformes, Cyprinodontiformes, and Perciformes, 21 families and 44 genera were sampled. The most common species were Astyanax asuncionensis Géry, 1972, Astyanax abramis (Jenyns, 1842), Odontostilbe pequira (Steindachner, 1882), Odontostilbe paraguayensis Eigenmann & Kennedy, 1903, Characidium zebra Eigenmann, 1909 and Hypostomus sp. This checklist brings additional knowledge on fish that inhabit tributaries to the major rivers of northern Pantanal.

RESUMO. O presente trabalho tem como objetivo descrever as características morfométricas de sete lagoas do Pantanal Norte e discutir suas implicações na limnologia deste ambientes. Os parâmetros utilizados foram: área, volume, profundidades máxima, média e relativa, perímetro, índices de desenvolvimento de volume e perímetro, comprimento e largura máxima. De modo geral, as maiorias das lagoas são rasas com pequenas profundidades relativas, assim menos propensas a estratificações térmicas e mais susceptíveis a ação dos ventos que atua como agente na resuspensão de matéria e mistura da coluna de água. Apresentam margens pouco irregulares e forma da bacia côncava que são menos influenciadas pelos processos de a erosão e sedimentação. Variações temporais na morfometria das lagoas conseqüentemente afetam os padrões hidrodinâmicos e limnológicos destes sistemas.Palavras-chave: morfometria, lagoas, limnologia, planície de inundação, Pantanal Norte. ABSTRACT. Morphometric characterization and its limnological implications inNorthern Pantanal lakes. The objective of this work is to describe the morphological characteristics of seven Northern Pantanal lakes and discuss their implications on the limnology of these environments. The following morphological parameters were used: area; volume; maximum, mean and relative depths; perimeter; volume and perimeter development indices; maximum length and width. Generally, most lakes are shallow, with low relative depths, suggesting little thermal stratification, as they are more susceptible to mixing of the water column and suspended sediments by wind action. Most lakes have regular banks (few irregularities) and have a concave shape, and thus are less subject to erosion processes. Temporal variations in the morphometry of these lakes are related to the hydrodynamic and limnological patterns of these systems.Key words: morphometry, lakes, limnology, floodplain, Northern Pantanal. Introdução Introdução Introdução IntroduçãoA morfometria dos corpos d'água tem relação direta com o balanço de nutrientes, a estabilidade térmica da coluna d'água, a produtividade biológica e os processos de circulação e dispersão de organismos (Panosso et al., 1995). A análise dos dados morfométricos, também possibilita a avaliação da capacidade de assimilação de impactos decorrentes da entrada de efluentes, taxas de acumulação e padrões de dispersão de poluentes (Sperling, 1999).A maioria dos lagos do Pantanal é conectada a rios e influenciada pelo pulso de inundação. Tal fato representa um equilíbrio dinâmico na estrutura destes sistemas (Junk et al., 1989;Neiff, 1990). Em escala regional, os fatores hidrográficos e a sazonalidade climática interferem na organização e funcionamento das zonas de transição aquático-terrestre. As lagoas estão submetidas ao pulso, porém em escala local, é a morfometria de cada sistema que atua como eficaz modelador e tradutor dos efeitos da inundação, uma vez que os reflete através das variações limnológicas.O estudo da morfometria de lagoas de inundação possibilita a melho...