Response of Functional Traits of Benthic Macroinvertebrates to Multiple Environmental Stressors During Different Hydrological Periods in Mountain Rivers

Abstract

Increased of human activities has led to the deterioration of hydrological conditions in mountain rivers, which affects the community of the macroinvertebrate directly. However, the response of the functions to these stressors remains unknown. Therefore, this study aimed to understand the selection and filtration of environmental stressors on benthic macroinvertebrates functional traits during two hydrological periods in typical mountain rivers, by analyzing the threshold of their function. The study revealed a total of 167 species of benthic macroinvertebrates were identified. The proportion of R-strategy associated traits dominated in both hydrological periods, with further increasing during the wet season. It was discovered that in the dry season, the response patterns of traits to environmental stressors gradients followed a hypothesized bell-shaped relationship. However, during the wet season, due to the increased environmental stress the response pattern showed a declining trend, accompany by significant decreased in functional diversity. Furthermore, these functional traits show varying in their threshold responses to stressors, and identified as effective environmental bioindicator metrics. Clinger was recognized as a good indicator trait for low-flow environments, while streamlined body shape and tegument respiration for low ammonia nitrogen concentrations. Overall, with the increase of environmental stressors, composition of functional traits tended to favor traits with high resistance, exhibiting high trait convergence and functional homogenization, which may impair ecosystem function. The evidence presented by this study provides a baseline for how community functions might be affected by changes in environmental conditions and offers insights for ecological management in mountain rivers.

Keywords: mountainous rivers, benthic macroinvertebrates, functional traits, bioindicators, environmental stressors