Decomposition of organic matter as a functional indicator for assessing the impact of multiple stressors on low-order neotropical streams
This research investigates organic matter (OM) decomposition in Neotropical low-order streams as a functional indicator to evaluate the impact of different stressors, with a particular focus on nutrient enrichment, temperature shifts, and land use conversion at different spatial scales. The research...
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | Brasil |
| Institución: | Universidade de São Paulo (USP) |
| Repositorio: | Biblioteca Digital de Teses e Dissertações da USP |
| Idioma: | inglés |
| OAI Identifier: | oai:teses.usp.br:tde-09062025-142139 |
| Acceso en línea: | https://www.teses.usp.br/teses/disponiveis/18/18138/tde-09062025-142139/ |
| Access Level: | acceso abierto |
| Palabra clave: | anthropogenic pressures córregos tropicais córregos urbanos cotton strips assays ecosystem functioning enriquecimento de nutrientes ensaios de tiras de algodão funcionamento do ecossistema functional indicators indicadores funcionais nutrient enrichment pressões antropogênicas tropical streams urban streams |
| Sumario: | This research investigates organic matter (OM) decomposition in Neotropical low-order streams as a functional indicator to evaluate the impact of different stressors, with a particular focus on nutrient enrichment, temperature shifts, and land use conversion at different spatial scales. The research is based on two independent studies that address complementary aspects of stream ecosystem functioning in neotropical regions. The first study evaluated the combined effects of nutrient enrichment and increased temperature on OM decomposition in two paired sub-catchments with differing levels of anthropogenic impact. Despite similar geological, climatic, and vegetation characteristics, the impacted stream exhibited significantly higher nutrient concentrations and temperatures compared to the reference stream. Using the cotton strip assay, microbial activity associated with OM decomposition was measured over a 41-day period. The results showed that the impacted stream had faster OM decomposition rates, particularly during the initial phase, likely driven by nutrient enrichment and elevated temperatures. However, decomposition rates declined in the second half of the experimental period, suggesting that extreme environmental conditions may surpass optimal thresholds for microbial activity. In contrast, the reference stream exhibited a more linear decomposition pattern, highlighting the role of riparian vegetation in buffering temperature fluctuations and supporting ecosystem stability. The second study examined land use effects across an urbanization gradient, revealing that watershed-scale urbanization above 50% triggered nonlinear increases in nutrient concentrations and decomposition rates. Restored streams showed intermediate functional responses, demonstrating both the potential and limitations of reach-scale rehabilitation. Together, these studies provide valuable insights into the interactive effects of stressors in neotropical streams. The findings emphasize the importance of considering multiple spatial scales in conservation strategies and highlight the role of riparian vegetation in mitigating the negative impacts of human activities on aquatic ecosystems. This work contributes to the broader understanding of stream ecosystem functioning in human-modified landscapes and underscores the relevance of functional indicators in assessing the ecological health of neotropical freshwater ecosystems. |
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