Publicação
Effects of plant-litter quality on litter decomposition by benthic invertebrates along a gradient of eutrophication
| Resumo: | Human impacts on freshwater ecosystems, such as nutrient enrichment and changes in riparian vegetation, are increasing, and policy makers are making efforts to identify management priorities. A critical point is the assessment of the ecological integrity of ecosystems. Benthic invertebrate communities have been widely used to assess the structural condition of streams, because they integrate the effects of stressors through time. However, structural measures do not provide information on ecosystem function making it difficult to actually assess the ecological condition of a stream. In streams, leaf-litter decomposition is a key ecosystem process that links riparian vegetation, physico-chemical environment and decomposer communities. In this study, we assessed the effects of litter quality and eutrophication on plant-litter decomposition and benthic invertebrates in streams. Leaves of five plant species with different chemical composition, namely Alnus glutinosa (alder), Castanea sativa (chestnut), Eucalyptus globulus (eucalyptus), Platanus sp. (plane tree) and Quercus robur (oak), were enclosed in coarse-mesh bags and immersed during 37 days in 7 streams of Northwest Portugal, along a gradient of eutrophication. Overall, the structure of benthic macroinvertebrate communities was sensitive to the water quality degradation and was able to discriminate the less eutrophic from the most eutrophic streams. Leaf-litter decomposition was stimulated until intermediate levels of eutrophication and decreased in the most eutrophic streams, where the high concentration of nutrients and the possible occurrence of pollutants could have inhibited decomposition. Leaf mass loss of alder leaves was significantly faster when compared to other leaf species, and macroinvertebrate community showed evidence of preferential colonization of high quality leaves. In conclusion, leaf decomposition showed to be a promising tool to assess changes in stream water quality. In addition, comparing to macroinvertebrate community analysis, estimation of leaf mass loss has advantages associated with costs, time of operation and simplicity of application. Overall, results from this study showed that both structural and functional measures were good predictors of eutrophication in streams. Therefore, these measures complemented each other and make an integrative assessment of the ecological condition of streams possible. |
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| Autores principais: | Pereira, Ana Maria Novais |
| Ano: | 2011 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Human impacts on freshwater ecosystems, such as nutrient enrichment and changes in riparian vegetation, are increasing, and policy makers are making efforts to identify management priorities. A critical point is the assessment of the ecological integrity of ecosystems. Benthic invertebrate communities have been widely used to assess the structural condition of streams, because they integrate the effects of stressors through time. However, structural measures do not provide information on ecosystem function making it difficult to actually assess the ecological condition of a stream. In streams, leaf-litter decomposition is a key ecosystem process that links riparian vegetation, physico-chemical environment and decomposer communities. In this study, we assessed the effects of litter quality and eutrophication on plant-litter decomposition and benthic invertebrates in streams. Leaves of five plant species with different chemical composition, namely Alnus glutinosa (alder), Castanea sativa (chestnut), Eucalyptus globulus (eucalyptus), Platanus sp. (plane tree) and Quercus robur (oak), were enclosed in coarse-mesh bags and immersed during 37 days in 7 streams of Northwest Portugal, along a gradient of eutrophication. Overall, the structure of benthic macroinvertebrate communities was sensitive to the water quality degradation and was able to discriminate the less eutrophic from the most eutrophic streams. Leaf-litter decomposition was stimulated until intermediate levels of eutrophication and decreased in the most eutrophic streams, where the high concentration of nutrients and the possible occurrence of pollutants could have inhibited decomposition. Leaf mass loss of alder leaves was significantly faster when compared to other leaf species, and macroinvertebrate community showed evidence of preferential colonization of high quality leaves. In conclusion, leaf decomposition showed to be a promising tool to assess changes in stream water quality. In addition, comparing to macroinvertebrate community analysis, estimation of leaf mass loss has advantages associated with costs, time of operation and simplicity of application. Overall, results from this study showed that both structural and functional measures were good predictors of eutrophication in streams. Therefore, these measures complemented each other and make an integrative assessment of the ecological condition of streams possible. |
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