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<p>The River Continuum Concept (RCC) provides a foundational template for predicting longitudinal changes in riverine communities. However, how hydraulic engineering modifies these natural gradients in subtropical regulated rivers remains mechanistically poorly understood. In particular, the construction of cascade dams creates serial discontinuity that fundamentally alters environmental filtering processes, yet empirical evidence from Asian monsoon regions—characterized by mountainous terrain and strong anthropogenic pressures—remains scarce. In the study reported here, we investigated how environmental filtering and serial discontinuity interactively shape macrobenthic metacommunity assembly along the main stem of the Oujiang River, a heavily regulated river in southeastern China punctuated by nine cascade dams. Using data from surveys at 24 sites across three seasons, we analyzed taxonomic composition, functional feeding groups, and diversity indices, and their relationships with environmental factors using spatial autocorrelation analysis, non-metric multidimensional scaling (NMDS), and Mantel tests. Our results revealed three key findings. First, macrobenthic community composition differed significantly among reaches (permutational multivariate analysis of variance [PERMANOVA], <i>p</i> = 0.037); however, this longitudinal variation was not a smooth continuum but rather formed distinct compartments shaped by dam-induced discontinuities. Second, environmental filtering dominated metacommunity assembly over dispersal limitation, as evidenced by non-significant spatial autocorrelation (Moran’s<i> I</i>, <i>p</i> &gt; 0.05) and strong species–environment correlations. Flow velocity and substrate composition acted as primary filters, with water quality parameters (5-day biochemical oxygen demand, ammonia nitrogen, electrical conductivity) serving as secondary filters that intensified in mid-to-lower reaches. Third, the interplay between environmental filtering and serial discontinuity produced three metacommunity compartments: upstream reaches dominated by rheophilic aquatic insects; midstream transitional communities shaped by dam-induced flow attenuation and fine sediment accumulation; and downstream estuarine assemblages dominated by pollution-tolerant Mollusca and euryhaline Polychaeta under conditions of organic enrichment and salinity stress. Notably, functional feeding group structure remained relatively stable across reaches despite taxonomic turnover. Our findings advance the mechanistic understanding of regulated river metacommunities by demonstrating that serial discontinuity modifies the type, intensity, and spatial configuration of environmental filters, thereby reorganizing community assembly patterns.</p>

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Environmental filtering and serial discontinuity interactively shape macrobenthic metacommunity assembly along the regulated Oujiang River, China

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Genting Yu,
  • Jihong Xia,
  • Xinyan Zhou,
  • Qiaoxi Zheng,
  • Weijie Cao,
  • Aiju You,
  • Hui Wu,
  • Lei Fu,
  • Jingwen Hu,
  • Lei Hua,
  • Hongqing Zhang,
  • Yongshu Zhu

摘要

The River Continuum Concept (RCC) provides a foundational template for predicting longitudinal changes in riverine communities. However, how hydraulic engineering modifies these natural gradients in subtropical regulated rivers remains mechanistically poorly understood. In particular, the construction of cascade dams creates serial discontinuity that fundamentally alters environmental filtering processes, yet empirical evidence from Asian monsoon regions—characterized by mountainous terrain and strong anthropogenic pressures—remains scarce. In the study reported here, we investigated how environmental filtering and serial discontinuity interactively shape macrobenthic metacommunity assembly along the main stem of the Oujiang River, a heavily regulated river in southeastern China punctuated by nine cascade dams. Using data from surveys at 24 sites across three seasons, we analyzed taxonomic composition, functional feeding groups, and diversity indices, and their relationships with environmental factors using spatial autocorrelation analysis, non-metric multidimensional scaling (NMDS), and Mantel tests. Our results revealed three key findings. First, macrobenthic community composition differed significantly among reaches (permutational multivariate analysis of variance [PERMANOVA], p = 0.037); however, this longitudinal variation was not a smooth continuum but rather formed distinct compartments shaped by dam-induced discontinuities. Second, environmental filtering dominated metacommunity assembly over dispersal limitation, as evidenced by non-significant spatial autocorrelation (Moran’s I, p > 0.05) and strong species–environment correlations. Flow velocity and substrate composition acted as primary filters, with water quality parameters (5-day biochemical oxygen demand, ammonia nitrogen, electrical conductivity) serving as secondary filters that intensified in mid-to-lower reaches. Third, the interplay between environmental filtering and serial discontinuity produced three metacommunity compartments: upstream reaches dominated by rheophilic aquatic insects; midstream transitional communities shaped by dam-induced flow attenuation and fine sediment accumulation; and downstream estuarine assemblages dominated by pollution-tolerant Mollusca and euryhaline Polychaeta under conditions of organic enrichment and salinity stress. Notably, functional feeding group structure remained relatively stable across reaches despite taxonomic turnover. Our findings advance the mechanistic understanding of regulated river metacommunities by demonstrating that serial discontinuity modifies the type, intensity, and spatial configuration of environmental filters, thereby reorganizing community assembly patterns.