The impact of how the early life cycle is physically represented on the modelled transport and retention of Antarctic krill

To examine the movement of Antarctic krill (Euphausia superba), between and within key regions of the Southern Ocean including within Area 48, we are modeling Lagrangian drifters to simulate transport pathways during early life stages. The simulated drifters are embedded within a 5-km horizontal resolution ocean/sea ice/ice shelf Regional Ocean Modeling System circulation model of the Southern Ocean. The drifters include simplistic behavior of the early life stages of krill including the initial descent/ascent cycle, diel vertical migration (DVM), and advection with simulated sea ice velocity, instead of ocean velocity, under certain conditions. It has been previously shown that advective pathways of simulated drifters can change significantly when sea ice advection or DVM is added. Here, we explore differences in the pathways to Marguerite Bay on the Western Antarctic Peninsula, a suspected larval winter nursery ground, in response to changes in the vertical movement rates in the initial descent/ascent cycle based on embryo size, the timing and depth of DVM, and when and if sea ice advection occurs. We show how varying embryo sizes can significantly change potential source regions for krill along the Western Antarctic Peninsula as larger embryos allow for survival over shallower bathymetry. Our study contributes to our understanding of habitat connectivity, krill population dynamics, and their potential responses to environmental changes in the Southern Ocean ecosystem.