Combining individual-based models and advection models to assess climate change impact on Antarctic krill

南大洋特别容易受到气候变暖的影响，是全球变暖最快的地区之一。这导致自1925年以来南格鲁吉亚岛周围的海洋表面温度在夏季增加了0.9 ℃，南极半岛西部从1951年至1998年增加了1 ℃。此外，全球变暖影响海冰的扩展和海冰形成的时间。这些环境变化加上海洋酸化将以一种未知的方式影响南极磷虾（Euphausia superba）的种群动态。由于磷虾是生态上的关键物种，在南极食物网中发挥着核心作用，而且具有很高的经济价值，因此迫切需要对南极磷虾种群对气候变化的反应趋势进行更可靠的环极预测，以改善管理和养护措施。原则上，人口模型可以提供这样的见解，但不同的威胁，和行为，幼磷虾相比，成年磷虾意味着，需要机械模型，而不是相关的经验模型。在评估磷虾对全球变化的适应潜力的模型中考虑磷虾的行为和个体变异性至关重要。因此，基于个体的，基于过程的模型将被设计和实现，包括不同生命阶段的磷虾的生理子模型。对磷虾的整个生命周期进行建模尤为重要，因为随着年龄的增长，磷虾会逆转其每日的垂直迁移行为，而成年磷虾在冬季能够减少其代谢活动，而幼磷虾则必须全年保持活跃。除了生理和行为方面，了解磷虾所处的环境条件至关重要。特别是海冰覆盖应该发挥至关重要的作用，因为它为磷虾幼虫提供了躲避捕食者和洋流的庇护所，但也是一个低食物环境，资源稀缺且分布不均。为了有意义地调查空间和时间变化的海冰动态和食物供应对磷虾种群动态的影响，基于个体的模型需要与平流模型相结合。这一点特别重要，因为磷虾幼虫不主动游泳，它们与海冰的相互作用可能对它们的目的地和到达时间产生重大影响。平流模型和基于个人的模型的耦合是非常创新的，需要适当处理不同的空间和时间分辨率相关的两个建模组件，即磷虾及其运输的水流和海冰漂移。因此，拟议的项目将有助于综合现有知识，从而能够更好地预测环境变化可能对南极磷虾在环极尺度上的影响。

The Southern Ocean is particularly susceptible to climate warming and comprises some of the most rapidly warming regions worldwide. This has resulted in an increase in sea surface temperatures of 0.9ºC in summer around the island of South Georgia since 1925 and 1ºC at the western Antarctic Peninsula from 1951 to 1998. Furthermore, global warming affects the extension of sea ice and the timing of sea ice formation. These environmental changes together with ocean acidification will impact the population dynamics of Antarctic krill (Euphausia superba) in an unknown way. Since krill is both an ecologically key species with its central role in the Antarctic food web and of high economic value, more reliable circumpolar projections of the trends of Antarctic krill populations in response to climate change are urgently needed for better management and conservation measures. In principle population models can provide such insights, but differing threats to, and behaviour of, larval krill compared with adult krill means that mechanistic models are needed instead of correlative empirical models. It will be crucial to consider the behaviour and individual variability of krill in the model to assess the adaptation potential of krill to global change. Therefore, individual-based, process-based models will be designed and implemented including physiological submodels for different life stages of krill. Modelling the whole life cycle of krill is particularly important since krill reverses its daily vertical migration behaviour as it gets older and while adult krill is able to reduce its metabolic activity in winter larval krill has to remain active throughout the year. Apart from physiological and behavioural aspects it is crucial to understand to which environmental conditions krill is exposed to. Especially sea ice cover is supposed to play a crucial role since it provides krill larvae shelter from predators and currents, but is also a low food environment where resources are scarce and patchily distributed. To meaningfully investigate the impact of changing spatial and temporal sea ice dynamics and food availability on the krill population dynamics the individual based model needs to be coupled with advection models. This is especially important as krill larvae do not actively swim and their interaction with sea ice can have a significant impact on their transport in terms of destination and timing of arrival. The coupling of advection models and individual-based models is highly innovative requiring appropriate handling of the different spatial and temporal resolutions relevant for the two modelling components, namely the krill and its transport by water currents and sea ice drift. The proposed project will thus help to integrate existing knowledge, allowing for an improved projection of the likely impact of environmental change on Antarctic krill at circumpolar scales.