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Spatio-temporal dynamics of undisturbed macroinvertebrate communities in the Mondego River basin : contribution to the ecological assessment of streams
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Resumo(s)
Macroinvertebrates have become the most commonly used and widely known biological indicators for assessing and monitoring human impacts in streams because they respond predictably to many kinds/intensities of anthropogenic pressures. Hence, they were included in the indicators group of ecological status required by the Water Framework Directive (WFD). However, the lack of understanding about natural spatio-temporal variations of macroinvertebrate communities and the lack of taxa lists for many undisturbed lotic systems most certainly hinder streams condition bioassessment, the successful restoration of the natural structural and functional integrity of an ecosystem, and the prediction of climate change impact on freshwater biodiversity. Spatio-temporal dynamics of undisturbed macroinvertebrate communities of the Mondego River basin (MRb) were analysed showing a strong variation both spatially and temporally. These variations were regulated through a multiplicity of factors operating at local [substrate type and hydraulic conditions (current speed, dissolved oxygen)] and larger spatial scales [streambed geology (inferred by conductivity), altitude and channel width]. Seasonal variation of these communities was more similar to that in other Mediterranean streams rather than that in northern temperate Portuguese streams, where seasonality is not as evident. Physical stream types of the MRb (based on the WFD system-B national typology) were tested for biological meaning and showed significant relevance for macroinvertebrates. However, spatial and temporal heterogeneity of abiotic conditions might hinder bioassessment since temporal variations and intermittency do not seem to be incorporated in typology results. Particular emphasis was given to high altitude intermittent streams (above 1400 m a.s.l.), where new chironomid species records were found for continental Portugal and the Iberian Peninsula and the loss of macroinvertebrate biodiversity is expected to occur based on climate change predictions. Also, a protocol to help selecting near-natural stream sites was developed and tested. Finally, the present work raised the need for long term studies, for more information concerning intermittent streams, for molecular studies to solve and complement the lack of taxonomical knowledge and for cross-linking reference conditions and climate change.
Descrição
Tese de doutoramento em Biologia (Ecologia), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008
Palavras-chave
Ecologia Teses de doutoramento - 2008