We analysed the spatial patterns in macroinvertebrate taxon richness and abundance at two scales: sampling unit and basin. We sampled 12 stream sites in three zones of Portugal, differing in climate geomorphology and water chemistry. At a sampling unit scale, substratum organic matter content, depth and the dominant size of substratum particles were correlated with numbers of taxa and individuals. We propose that the number of taxa at a small scale depends on the number of individuals, which in turn is the result of organic matter accumulation, hydrologic and substratum characteristics. The environmental parameters better explaining the large-scale biological data were temperature, minimum size of substratum particles and pH. Regardless of the relative importance of variable types and mechanisms regulating stream invertebrates along the climatic gradient, rivers from the North and Centre appeared to be richer in taxa than the typically Mediterranean streams in the South. IntroductionOne important attribute of communities is their species richness and diversity. Various mechanisms have been indicated as controlling species diversity, including productivity, habitat heterogeneity and biotic interactions (TOWNSEND, 1989;TOWNSEND et al., 2002). Rivers and their adjacent riparian zones are considered to be dynamic, complex and diverse systems (RISSER, 1990;NAIMAN et al., 1993). Benthic macroinvertebrates are an important component of the river biota. At a large scale, diversity of invertebrates along and among rivers is affected by factors such as longitudinal zonation of river abiotic conditions (VANNOTE et al., 1980;CLENAGHAN et al., 1998), channel width and catchment size (MALMQVIST and HOFFSTEN, 2000), discharge (CORTES et al., 2002), temperature and pH (TOWNSEND et al., 1983;CLARKE and SCRUTON, 1997).At a stream reach scale, invertebrates have, in general, a clumped distribution, which is assumed to be related to the mosaic of interchanging conditions in substratum, flow conditions, depth and many others (TOWNSEND, 1989;CORTES et al., 2002). These conditions are likely to change at a scale of only a few metres or centimetres. At this small scale, factors indicated as regulating macroinvertebrate distribution and richness are current velocity, substratum particle size (MARCHANT et al., 1985;WILLIAMS and MOORE, 1986;ARUNACHALAM et al., 1991), substratum stability (MALMQVIST and OTTO, 1987), organic matter in the Internat. Rev. Hydrobiol.

A navegação consulta e descarregamento dos títulos inseridos nas Bibliotecas Digitais UC Digitalis, UC Pombalina e UC Impactum, pressupõem a aceitação plena e sem reservas dos Termos e Condições de Uso destas Bibliotecas Digitais, disponíveis em https://digitalis.uc.pt/pt-pt/termos.Conforme exposto nos referidos Termos e Condições de Uso, o descarregamento de títulos de acesso restrito requer uma licença válida de autorização devendo o utilizador aceder ao(s) documento(s) a partir de um endereço de IP da instituição detentora da supramencionada licença.Ao utilizador é apenas permitido o descarregamento para uso pessoal, pelo que o emprego do(s) título(s) descarregado(s) para outro fim, designadamente comercial, carece de autorização do respetivo autor ou editor da obra. Na medida em que todas as obras da UC Digitalis se encontram protegidas pelo Código do Direito de Autor e Direitos Conexos e demais legislação aplicável, toda a cópia, parcial ou total, deste documento, nos casos em que é legalmente admitida, deverá conter ou fazer-se acompanhar por este aviso. Freshwater macroinvertebrates in the Mondego river basin Autor(es):Graça, Manuel Augusto; Coimbra, Nuno; Carvalho, Maria João; Oliveira, Ricardo; Abelho, Manuela FRESHWATER MACROINVERTEBRATES lN THE MONDEGO RIVER BASINInvertebrates in streams and rivers are diverse. abundant and perform important ecological functions. recycling organic matter, feeding upon algae and transferring energy for larger animais. including fish. birds. amphibians and others.The macroinvertebrate communities of 34 stream sites in the Mondego River basin were analysed to assess changes in taxa richness and percentage of shredders along river order / size gradient and to assess water quality by means of biotic indices. Taxa richness was higher in low arder streams when compared with larger rivers. ln some rivers. shredder abundance was higher in autumn. but in other rivers we did not observe changes in shredder abundance along the year. Water quality. measured by the application of the biotic index BMWP·. revealed that many small low order streams can be considered as unpolluted. However, water quality decreased in larger rivers.