Regime shifts in ecosystem structure and processes are typically studied from a temporal perspective. Yet, theory predicts that in large ecosystems with environmental gradients, shifts should start locally and gradually spread through space. Here we empirically document a spatially propagating shift in the trophic structure of a large aquatic ecosystem, from dominance of large predatory fish (perch, pike) to the small prey fish, the three-spined stickleback. Fish surveys in 486 shallow bays along the 1200 km western Baltic Sea coast during 1979–2017 show that the shift started in wave-exposed archipelago areas near the open sea, but gradually spread towards the wave-sheltered mainland coast. Ecosystem surveys in 32 bays in 2014 show that stickleback predation on juvenile predators (predator–prey reversal) generates a feedback mechanism that appears to reinforce the shift. In summary, managers must account for spatial heterogeneity and dispersal to better predict, detect and confront regime shifts within large ecosystems.

通常从时间角度研究生态系统结构和过程中的体制变化。然而，理论预测，在具有环境梯度的大型生态系统中，变化应该从局部开始，并逐渐通过空间传播。在这里，我们凭经验记录了大型水生生态系统营养结构的空间传播转变，从大型掠食性鱼类（鲈鱼、梭鱼）的主导地位到小型猎物鱼，即三刺棘鱼。1979 年至 2017 年期间，对波罗的海西部海岸 1200 公里的 486 个浅海湾进行的鱼类调查表明，这种转变始于靠近公海的受海浪影响的群岛地区，但逐渐向海浪遮蔽的大陆海岸蔓延。2014 年在 32 个海湾进行的生态系统调查表明，刺鱼捕食幼年掠食者（捕食者-猎物逆转）产生了一种反馈机制，似乎强化了这种转变。总之，管理人员必须考虑空间异质性和分散性，以更好地预测、检测和应对大型生态系统内的制度变化。