Migratory Crossroads: predicting the dynamics of a great vertical migration in a changing habitat

The daily and seasonal vertical migrations of zooplankton collectively form the greatest synchronized animal movement on our planet. In ‘Migratory Crossroads’, we will study how climate change may affect the vertical migrations of the keystone copepod Calanus finmarchicus along the northern Norwegian coast and adjacent areas of the Norwegian and Barents Seas. Calanus finmarchicus is an important feed for many species in the Norwegian and Barents Sea ecosystems and plays a crucial ecological and economic role. Although this marine ecosystem is expected to change significantly due to climate change, its impacts on the daily and seasonal vertical migrations of C. finmarchicus is not fully understood. While most studies focus on only one or few environmental variables, our project "Migratory Crossroads" may fill some important knowledge gaps by studying the potential changes in the vertical migration of C. finmarchicus under the cumulative impact of expected climate-change-related shifts in light, temperature, food, and predation environments. "Migratory Crossroads" will apply a computer model that simulates the vertical-migration behaviour of C. finmarchicus individuals in virtual habitats representing different environmental conditions. This model will first be run for present-day conditions. The model-predicted daily and seasonal vertical migratory patterns will be validated based on field data collected from both research vessels and autonomous surface and underwater vehicles. The improved model will then be run in virtual environments representing the above-mentioned climate-change-driven shifts in the Norwegian and Barents Seas expected towards the end of this century. These predictive model runs will allow us to check how vertical migrations of C. finmarchicus change with cumulative climate-change impacts. We will also be able to observe the impacts of such behavioural changes on the ecological and economic benefits connected to these migrations.

Vertical migration of zooplankton is known as the greatest synchronized animal movement of our planet. In the coastal and offshore waters of northern Norway, a tiny herbivorous copepod named Calanus finmarchicus performs two different vertical migrations. These include daily vertical movements of tens-to-hundreds of meters (diel vertical migration) and seasonal movements of hundreds-to-thousands of meters (seasonal vertical migration) in response to corresponding variations of irradiance, temperature, food availability and visual predation risk. These migrations play a paramount ecological and economic roles because vertical behaviour, abundance and phenology of many commercially harvested fish species are linked to these and vertical migrations contribute to the export of atmospheric carbon into the ocean's deep interior – a key process in the buffering of climate change. However, due to rapid rate of climate change, routine diel & seasonal environmental variability under which these migrations occur keep shifting unprecedentedly, and little is known about how vertical migrations of C. finmarchicus would respond to these environmental shifts. While the current understanding of the subject matter is rooted in studying the impacts of single environmental variables on vertical migrations, in the proposed project, Migratory Crossroads, we aim to study the cumulative impacts of irradiance, temperature, food and predation environmental shifts expected in future high-latitude marine habitats on C. finmarchicus diel and seasonal vertical migrations. This will be done using a hybrid meahanistic-empirical approach, where predictions of a simulation model with an unconstrained representation of vertical migrations will be validated with cutting-edge high-resolution field data. Through Migratory Crossroads, we aim to accurately predict future dynamics of C. finmarchicus verical migrations and their impacts on the ecological and economic benefits reaped from these migrations.