At high latitudes, the suitable window for timing reproductive events is particularly narrow, promoting tight synchrony between trophic levels. Climate change may disrupt this synchrony due to diverging responses to temperature between, for example, the early life stages of higher trophic levels and their food resources. Evidence for this is equivocal, and the role of compensatory mechanisms is poorly understood. Here, we show how a combination of ocean warming and coastal water darkening drive long‐term changes in phytoplankton spring bloom timing in Lofoten Norway, and how spawning time of Northeast Arctic cod responds in synchrony. Spring bloom timing was derived from hydrographical observations dating back to 1936, while cod spawning time was estimated from weekly fisheries catch and roe landing data since 1877. Our results suggest that land use change and freshwater run‐off causing coastal water darkening has gradually delayed the spring bloom up to the late 1980s after which ocean warming has caused it to advance. The cod appear to track phytoplankton dynamics by timing gonadal development and spawning to maximize overlap between offspring hatch date and predicted resource availability. This finding emphasises the importance of land–ocean coupling for coastal ecosystem functioning, and the potential for fish to adapt through phenotypic plasticity.

中文翻译：

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土地利用变化和沿海水域变暗驱动浮游植物和鱼类物候在百年时间尺度上的同步动态

在高纬度地区，繁殖事件的适宜时间窗口特别窄，促进了营养级之间的紧密同步。气候变化可能会破坏这种同步性，因为例如较高营养级的生命早期阶段及其食物资源之间对温度的反应不同。这方面的证据是模棱两可的，而且人们对补偿机制的作用知之甚少。在这里，我们展示了海洋变暖和沿海水体变暗的结合如何驱动挪威罗弗敦群岛浮游植物春季开花时间的长期变化，以及东北北极鳕鱼的产卵时间如何同步响应。春季水华时间是根据可追溯至 1936 年的水文观测得出的，而鳕鱼产卵时间是根据自 1877 年以来每周的渔业捕捞量和鱼子上岸数据估算的。我们的结果表明，土地利用变化和淡水径流导致沿海水域变暗，逐渐推迟了鳕鱼的产卵时间。春季开花期一直持续到 20 世纪 80 年代末，此后海洋变暖导致其提前。鳕鱼似乎通过定时性腺发育和产卵来跟踪浮游植物动态，以最大限度地提高后代孵化日期和预测资源可用性之间的重叠。这一发现强调了陆地-海洋耦合对于沿海生态系统功能的重要性，以及鱼类通过表型可塑性适应的潜力。