The deposition of excess fine sediment and clogging of benthic substrates is recognised as a global threat to ecosystem functioning and community dynamics. Legacy effects of previous sedimentation create a habitat template on which subsequent ecological responses occur, and therefore, may have a long-lasting influence on community structure. Our experimental study examined the effects of streambed colmation (representing a legacy effect of fine sediment deposition) and a suspended fine sediment pulse on macroinvertebrate drift and community dynamics. We used 12 outdoor stream mesocosms that were split into two sections of 6.2 m in length (24 mesocosm sections in total). Each mesocosm section contained a coarse bed substrate with clear bed interstices or a fine bed substrate representing a colmated streambed. After 69 days, a fine sediment pulse with three differing fine sediment treatments was applied to the stream mesocosms. Added fine sediment influenced macroinvertebrate movements by lowering benthic density and taxonomic richness and increasing drift density, taxonomic richness, and altering drift assemblages. Our study found the highest dose of sediment addition (an estimated suspended sediment concentration of 1112 mg l⁻¹) caused significant differences in benthic and drift community metrics and drift assemblages compared with the control treatment (30 l of water, no added sediment). Our results indicate a rapid response in drifting macroinvertebrates after stressor application, where ecological impairment varies with the concentration of suspended sediment. Contrary to expectations, bed substrate characteristics had no effect on macroinvertebrate behavioural responses to the fine sediment pulse.

过量细粒沉积物的沉积和底栖基质的堵塞被认为是对生态系统功能和群落动态的全球威胁。先前沉积的遗留影响创造了随后发生生态反应的栖息地模板，因此，可能对群落结构产生长期影响。我们的实验研究检查了河床整理（代表细粒沉积物沉积的遗留效应）和悬浮细粒沉积物脉冲对大型无脊椎动物漂移和群落动态的影响。我们使用了 12 个室外河流中观，它们被分成两个长度为 6.2 m 的部分（总共 24 个中观部分）。每个中观部分都包含一个带有清晰床间隙的粗床基质或一个代表平行河床的细床基质。69天后，将具有三种不同细粒沉积物处理的细粒沉积物脉冲应用于河流中观。添加的细粒沉积物通过降低底栖密度和分类丰富度以及增加漂流密度、分类丰富度和改变漂流组合来影响大型无脊椎动物的运动。我们的研究发现最高剂量的沉积物添加（估计悬浮沉积物浓度为 1112 mg l^-1 ) 与对照处理（30 升水，不添加沉积物）相比，导致底栖和漂流群落指标和漂流组合的显着差异。我们的结果表明，在施加压力后，漂流的大型无脊椎动物会出现快速反应，其中生态损害随悬浮沉积物的浓度而变化。与预期相反，床底特性对大型无脊椎动物对细沉积物脉冲的行为反应没有影响。