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，并由世界上变暖最快的一些地区组成。这导致南乔治亚岛周围夏季海面温度自1925年以来上升了0.9摄氏度，从1951年至1998年南极半岛西部上升了1摄氏度。此外，全球变暖影响了海冰的延伸和海冰形成的时间。这些环境变化和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。由于磷虾既是生态关键物种，在南极食物网中发挥核心作用，又具有很高的经济价值，迫切需要对南极磷虾种群趋势作出更可靠的环极预测，以应对气候变化，以便更好地管理和养护措施。原则上，种群模型可以提供这样的见解，但与成体磷虾相比，对幼体磷虾的威胁和行为的不同意味着需要机械模型而不是相关的经验模型。在模型中考虑磷虾的行为和个体变异性，以评估磷虾对全球变化的适应潜力将是至关重要的。因此，将设计和实现基于个体、基于过程的模型，包括针对不同生活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特别重要，因为随着磷虾年龄的增长，它的每日垂直迁徙行为会发生逆转，尽管成年磷虾能够减少其在冬季的代谢活动，但幼体磷虾必须全年保持活跃。除了生理和行为方面，了解磷虾暴露在哪些环境条件下是至关重要的。特别是海冰覆盖被认为发挥了关键作用，因为它为磷虾幼体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，分布参差不齐。为了有意义地研究变化的时空海冰动态和食物供应对磷虾种群动态的影响，需要将基于个体的模型与平流模型相结合。这一点尤其重要，因为磷虾幼体不活跃地游泳，它们与海冰的相互作用可能对它们的运输产生重大影响，无论是目的地还是到达的时间。平流模式和基于个人的模式的结合具有很高的创新性，需要适当处理与两个模式组成部分有关的不同空间和时间分辨率，即磷虾及其通过水流和海冰漂移的输送。因此，拟议的项目将有助于整合现有的知识，从而能够更好地预测环境变化对环极地尺度的南极磷虾可能产生的影响。

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.