Ecological vs. climate uncertainty in future marine ecosystems: lessons learned from krill in a major upwelling region

Krill is a central organism in the food web of many marine ecosystems and eastern boundary current upwelling regions specifically. Here, a superensemble of climate and ecological models is used to determine drivers of future change, variability, and uncertainty in krill abundance for the California Current. While krill is projected to slowly decrease throughout the 21st century, the long-term trend consistently exceeds natural variability only under extreme warming. Similarly, unprecedented low krill years are expected to progressively increase, but their frequency of occurrence will depend on background abundances tied to low-frequency climate variability. The relative contributions of warming rate and model formulation to projected uncertainty are comparable and reflect latitudinal changes in the magnitude of climate forcing and availability of empirical data to parameterize krill models, thereby warranting a more pragmatic incorporation of anthropogenic and ecological uncertainty sources when projecting the fate of marine ecosystems in a changing climate.

磷虾（Krill）是众多海洋食物网中的核心物种，尤其在东部边界流上升流区域发挥着核心生态作用。本研究借助气候与生态模型超级集合（superensemble）方法，旨在厘清加利福尼亚流（California Current）海域磷虾丰度未来变化、波动及不确定性的驱动因子。尽管预计整个21世纪磷虾种群将缓慢衰减，但仅在极端增温情景下，其长期下降趋势才会始终超出自然波动幅度。与之相仿，磷虾丰度异常偏低的年份预计将逐步增多，但此类事件的发生频率将取决于与低频气候波动相关的背景种群丰度水平。增温速率与模型构建方式对预测不确定性的相对贡献不相上下，二者均反映了气候强迫（climate forcing）强度的纬度梯度变化，以及用于参数化磷虾模型的经验数据可得性差异。因此，在预估气候变化背景下海洋生态系统的演变走向时，应更务实地纳入人为活动与生态相关的不确定性来源。