Publicação
Effects of eutrophication on stream-dwelling decomposers of plant-litter
| Resumo: | Plant-litter decomposition is the major source of nutrients and energy in low-order forested streams. Microorganisms, in particular aquatic fungi, play an important role in this process by mineralizing plant-litter and transforming it into a more palatable food source for macroinvertebrates. However, anthropogenic stressors, in particularly eutrophication, can strongly affect aquatic biota with consequences to plant-litter decomposition in freshwater ecosystems. In this study, we assessed the effects of eutrophication on leaf-litter decomposition and associated biota by analyzing fungal diversity, reproduction and biomass, benthic macroinvertebrate diversity and biomass and decomposition rates of oak leaves in five streams in Northwest Portugal, differing in their trophic status: Agra, oligotrophic; Oliveira and Andorinhas, moderately eutrophic; Selho, highly eutrophic and Couros, hypertrophic streams. In addition, since fungal sporulation is often severally reduced in hypertrophic streams, we employed both traditional (fungal spores identification) and molecular techniques (denaturing gradient gel electrophoresis - DGGE) to assess fungal diversity more accurately. Eutrophication affected fungal (biomass and sporulation) as well as macroinvertebrate biomass in the 5 streams. Higher leaf decomposition rates and fungal biomasses were found in the moderately eutrophic streams (Oliveira and Andorinhas) than in highly eutrophic streams (Selho and Couros). Higher fungal reproduction was also found in Selho, Andorinhas and Oliveira streams, than in Agra and Couros streams. On the other hand, higher biomasses of invertebrates, particularly Oligochaeta and Chironomidae, were found in the most eutrophic streams. Fungal diversity, assessed as spore identification and counts, was severally reduced in Couros than in the other streams, but DGGE fingerprints of fungal communities revealed in high diversity in all streams. Shredder taxa were dominant in decomposing oak leaves in the less eutrophic streams (Agra, Oliveira and Andorinhas), but these invertebrates were almost or completely absent in the most eutrophic streams (Selho and Couros). The community structure of both fungi (from fungal spores or DGGE fingerprints) and macroinvertebrates discriminated streams according to the level of eutrophication. Overall results suggested that the combination of structural measures of fungal and invertebrate communities with functional measures, such as leaf-litter decomposition, may help to better assess the impacts of eutrophication in freshwater ecosystems. |
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| Autores principais: | Trabulo, José |
| Ano: | 2013 |
| 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: | Plant-litter decomposition is the major source of nutrients and energy in low-order forested streams. Microorganisms, in particular aquatic fungi, play an important role in this process by mineralizing plant-litter and transforming it into a more palatable food source for macroinvertebrates. However, anthropogenic stressors, in particularly eutrophication, can strongly affect aquatic biota with consequences to plant-litter decomposition in freshwater ecosystems. In this study, we assessed the effects of eutrophication on leaf-litter decomposition and associated biota by analyzing fungal diversity, reproduction and biomass, benthic macroinvertebrate diversity and biomass and decomposition rates of oak leaves in five streams in Northwest Portugal, differing in their trophic status: Agra, oligotrophic; Oliveira and Andorinhas, moderately eutrophic; Selho, highly eutrophic and Couros, hypertrophic streams. In addition, since fungal sporulation is often severally reduced in hypertrophic streams, we employed both traditional (fungal spores identification) and molecular techniques (denaturing gradient gel electrophoresis - DGGE) to assess fungal diversity more accurately. Eutrophication affected fungal (biomass and sporulation) as well as macroinvertebrate biomass in the 5 streams. Higher leaf decomposition rates and fungal biomasses were found in the moderately eutrophic streams (Oliveira and Andorinhas) than in highly eutrophic streams (Selho and Couros). Higher fungal reproduction was also found in Selho, Andorinhas and Oliveira streams, than in Agra and Couros streams. On the other hand, higher biomasses of invertebrates, particularly Oligochaeta and Chironomidae, were found in the most eutrophic streams. Fungal diversity, assessed as spore identification and counts, was severally reduced in Couros than in the other streams, but DGGE fingerprints of fungal communities revealed in high diversity in all streams. Shredder taxa were dominant in decomposing oak leaves in the less eutrophic streams (Agra, Oliveira and Andorinhas), but these invertebrates were almost or completely absent in the most eutrophic streams (Selho and Couros). The community structure of both fungi (from fungal spores or DGGE fingerprints) and macroinvertebrates discriminated streams according to the level of eutrophication. Overall results suggested that the combination of structural measures of fungal and invertebrate communities with functional measures, such as leaf-litter decomposition, may help to better assess the impacts of eutrophication in freshwater ecosystems. |
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