Fisheries and Oceans Canada, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, B2Y 4A2, Canada.
Ann Bot. 2024 Mar 8;133(1):73-92. doi: 10.1093/aob/mcad170.
Changes in kelp abundances on regional scales have been highly variable over the past half-century owing to strong effects of local and regional drivers. Here, we assess patterns and dominant environmental variables causing spatial and interspecific variability in kelp persistence and resilience to change in Nova Scotia over the past 40 years.
We conducted a survey of macrophyte abundance at 251 sites spanning the Atlantic coast of Nova Scotia from 2019 to 2022. We use this dataset to describe spatial variability in kelp species abundances, compare species occurrences to surveys conducted in 1982 and assess changes in kelp abundance over the past 22 years. We then relate spatial and temporal patterns in abundance and resilience to environmental metrics.
Our results show losses of sea urchins and the cold-tolerant kelp species Alaria esculenta, Saccorhiza dermatodea and Agarum clathratum in Nova Scotia since 1982 in favour of the more warm-tolerant kelps Saccharina latissima and Laminaria digitata. Kelp abundances have increased slightly since 2000, and Saccharina latissima and L. digitata are widely abundant in the region today. The highest kelp cover occurs on wave-exposed shores and at sites where temperatures have remained below thresholds for growth (21 °C) and mortality (23 °C). Moreover, kelp has recovered from turf dominance following losses at some sites during a warm period from 2010 to 2012.
Our results indicate that dramatic changes in kelp community composition and a loss of sea urchin herbivory as a dominant driver of change in the system have occurred in Nova Scotia over the past 40 years. However, a broad-scale shift to turf-dominance has not occurred, as predicted, and our results suggest that resilience and persistence are still a feature of kelp forests in the region despite rapid warming over the past several decades.
在过去的半个世纪中，由于局部和区域驱动因素的强烈影响，海带的丰度在区域尺度上发生了高度变化。在这里，我们评估了过去 40 年来导致新斯科舍省海带持久性和对变化的恢复力的空间和种间变异性的模式和主要环境变量。
我们对 2019 年至 2022 年在新斯科舍省大西洋沿岸的 251 个地点进行了大型藻类丰度调查。我们使用该数据集描述海带物种丰度的空间变异性，将物种出现情况与 1982 年的调查进行比较，并评估过去 22 年海带丰度的变化。然后，我们将丰度和恢复力的空间和时间模式与环境指标联系起来。
我们的研究结果表明，自 1982 年以来，新斯科舍省的海胆和耐寒海带物种 Alaria esculenta、Saccorhiza dermatodea 和 Agarum clathratum 减少，而更耐热的海带 Saccharina latissima 和 Laminaria digitata 增加。自 2000 年以来，海带丰度略有增加，目前 Saccharina latissima 和 L. digitata 在该地区广泛存在。海带覆盖率最高的地方是海浪暴露的海岸和温度低于生长（21°C）和死亡（23°C）阈值的地方。此外，在 2010 年至 2012 年的一个温暖时期，一些地点的海草大量繁殖后，海带已经从海草的优势地位中恢复过来。
我们的研究结果表明，在过去的 40 年中，新斯科舍省的海带群落组成发生了巨大变化，海胆食草动物作为系统变化的主要驱动因素的作用已经消失。然而，正如预测的那样，大范围的向海草优势的转变并没有发生，我们的研究结果表明，尽管过去几十年迅速变暖，该地区的海带林仍然具有恢复力和持久性。
