Modeling the remote and local connectivity of Antarctic krill populations along the western Antarctic Peninsula

The abundance and distribution of Antarctic krill Euphausia superba over the western Antarctic Peninsula (wAP) continental shelf suggest that these populations are maintained by inputs from upstream sources via advection of individuals that originated in the Bellingshausen Sea, in addition to local spawning and retention. The objective of our study was to evaluate these 2 mechanisms (remote and local inputs) and the consequences for wAP Antarctic krill populations. The relative effect of local versus remote connectivity was investigated using Lagrangian particle tracking experiments. Particles released in the Bellingshausen Sea were transported to the wAP shelf in 120 d, which is consistent with the time required for Antarctic krill eggs to develop into late-stage larvae. An estimated 23% of the particles released along the shelf break crossed the outer shelf and were transported to the mid and inner regions of the wAP shelf via 3 pathways that provide conduits for onshore intrusions of Circumpolar Deep Water (CDW). Of the particles that moved onto the wAP shelf, 54% were transported to inner shelf regions that are associated with areas of enhanced biological production. Of the particles at the outer shelf similar to 33% continued transport northeastward with the Antarctic Circumpolar Current. Particles released in the mid and inner shelf showed limited connectivity and low export from the shelf (<20%). The Lagrangian experiments indicate that Antarctic krill populations in the Marguerite Bay region of the wAP continental shelf are maintained by local and remote inputs of larvae. Regions influenced by intrusions of CDW are more dependent on remote inputs of Antarctic krill larvae.