Simulating nursery areas for Antarctic krill along the western Antarctic Peninsula with relevance for the Domain 1 MPA Planning process

Antarctic krill (Euphausia superba) is a key species and a dominant grazer in the Antarctic marine food web. Observational and modelling studies have shown that development of the embryo and early larval stages of Antarctic krill (the descent-ascent cycle) is largely controlled by temperature that conditions a successful completion of the cycle. The objective of the present study is to estimate favorable nursery areas for Antarctic krill and assess how environmental conditions (stronger winds, enhanced transport of Circumpolar Deep Water and higher ocean temperatures) may alter their distribution along the western Antarctic Peninsula (WAP) shelf. This objective was addressed using a one-dimensional, temperature-dependent model of the descent-ascent cycle of Antarctic krill embryos and larvae that was forced with temperature and density fields from a high-resolution model scaled by projections for 2030 for the WAP. Projected ocean temperature and density fields were obtained from the Coupled Model Intercomparison Project (CMIP5), for a high emission scenario. To estimate the influence of increased winds and higher CDW onto the shelf, a high-resolution circulation model was used to simulate Lagrangian particles and determine preferred transport pathways along the continental shelf of the WAP. Projected nursery areas by 2030 occupy the mid and inner-shelf, consistent with bathymetric depressions and biological hot spots (e.g. Crystal Sound and Palmer Deep). Projected circulation pathways may enhance advection of krill larvae from nursery areas into the innershelf, to regions such as the Gerlache Strait and the area between Anvers and Renaud Island. Increased advection of CDW into the innershelf may also support a successful descend-ascend cycle and enhance krill early development.