Abstract:

Aims: Understanding how urbanization alters the structure and function of aquatic communities is essential for assessing urban river environments and conserving biodiversity. Macroinvertebrates play a crucial role in maintaining the functions and integrity of river ecosystems, yet the ecological drivers and mechanisms through which urbanization influences their functional diversity remain poorly understood.

Methods: In 2019, macroinvertebrate samples were collected during both the wet and dry seasons from 62 sites distributed across five major watersheds in Shenzhen, covering a gradient of urbanization intensity. Taxonomic and functional diversity was quantified using species richness and the RaoQ index, respectively. The Mann-Whitney U test was used to compare these two diversity indices between urban and suburban rivers. Furthermore, multivariate stepwise regression analysis was performed to identify key environmental factors shaping macroinvertebrate taxonomic and functional diversity. Finally, variation partitioning was applied to assess the relative contributions of local physical environmental conditions, water chemistry variables, and land-use factors.

Results: Taxonomic and functional diversity were consistently higher in suburban rivers (with lower levels of urbanization) than in urban rivers (with higher levels of urbanization) during both the wet and dry seasons. This disparity was more pronounced during the wet season, suggesting that urbanization exerts stronger impacts on macroinvertebrate diversity during periods of higher water flow. In contrast, functional redundancy was higher in urban rivers than in their suburban counterparts. Stepwise regression and variance partitioning analyses revealed that land-use, local physical environmental factors, and water chemistry variables collectively accounted for 37%–57% of the variation in taxonomic and functional diversity. However, the relative influence of these ecological factors varied depending on the biodiversity dimension and the season. Among them, local physical environmental and water chemistry variables emerged as the primary drivers (explaining 5%–22% of the variation), followed by land-use variables (2%–4%). Specifically, water chemistry variables—such as permanganate index and conductivity—had the greatest influence on taxonomic and functional diversity during the dry season, whereas local physical variables—such as substrate composition and water depth—played a more significant role in shaping functional diversity during the wet season.

Key words: Keywords: Shenzhen, Rivers, Macroinvertebrate, Taxonomic and functional diversity, Environmental factors