Productive and ecologically highly valuable ecosystems, macrotidal estuaries are also characterised by complex habitat and connectivity dynamics driven by tidal and freshwater influence. Organisms living in these constantly changing systems have to match their movement patterns to the shifting habitat mosaic using available windows of connectivity to access habitat patches of interest. This appears particularly important for the juvenile stages of many fish species colonising shallow and intertidal areas of the estuaries as summer nurseries. We apply tools from landscape ecology to investigate the estuarine habitat and connectivity dynamics on the example of juvenile seabass (Dicentrarchus labrax). We test under which conditions spatio-temporal bottlenecks to estuarine nursery colonisation may emerge for this species in a human-modified estuary. Combining a hydrodynamic model of the Seine estuary with remote sensing data allows us to capture structural changes in habitat availability and connectivity at the estuarine scale and at a fine spatio-temporal resolution. With chronological least-cost modelling of successive tidal steps, we assess patterns of nursery accessibility and estimate tidal colonisation fronts for different mobility scenarios. We show that, at certain hydrological conditions, tidal water level variation causes local disruptions of habitat availability and connectivity, creating temporary bottlenecks for seabass juveniles’ movement. Fish mobility appears determinant for their vulnerability to these connectivity disruptions. Our approach allows for quantitative assessment and visualisation of riverscape complexity related to tidal dynamics. It is applicable to other highly dynamic ecosystems, where the mobile nature of connectivity and habitats needs to be integrated into conservation and management planning.

潮汐河口还具有生产力和生态价值很高的生态系统，其特征还在于潮汐和淡水的影响驱动着复杂的栖息地和连通性。生活在这些不断变化的系统中的生物必须使用可用的连通性窗口将其运动方式与不断变化的栖息地马赛克相匹配，以访问感兴趣的栖息地斑块。这对于在夏季育苗场中定居在河口浅滩和潮间带的许多鱼类的幼年期显得尤为重要。我们使用景观生态学的工具，以幼年鲈鱼（Dicentrarchus labrax）为例，研究河口栖息地和连通性动态）。我们测试了在哪种条件下人类修饰的河口中该物种可能出现河口苗圃定植的时空瓶颈。将塞纳河河口的水动力模型与遥感数据结合起来，使我们能够在河口尺度上以良好的时空分辨率捕获栖息地可用性和连通性的结构变化。通过连续潮汐步骤的时间成本最小的建模，我们评估了托儿所的可及性模式，并估计了不同机动性情况下的潮汐殖民化前沿。我们表明，在某些水文条件下，潮汐水位变化会导致栖息地可用性和连通性的局部破坏，从而给海鲈幼鱼的运动造成临时瓶颈。鱼的流动性似乎决定了它们是否容易受到这些连通性破坏的影响。我们的方法可以定量评估和可视化与潮汐动力学有关的河景复杂性。它适用于其他高度动态的生态系统，在这些生态系统中，需要将连通性和栖息地的移动性整合到保护和管理规划中。