Modeling the transport and fate of euphausiids in the Ross Sea

Abstract

Antarctic krill (Euphausia superba) and crystal krill (Euphausia crystallorophias), important components of the Ross Sea food web, differ in their population distribution. The objective of this study was to determine whether these differing distributions result primarily from differences in spawning locations, larval development times, and transport by the Ross Sea circulation. To address this objective, Lagrangian particle tracking experiments were used to simulate the transport of larvae of Antarctic krill and crystal krill. The particle simulations showed that regions providing inputs of Antarctic krill to the Ross Sea were along the outer shelf/slope. Crystal krill transport and retention were along the shallow banks on the outer Ross Sea shelf. Particles initialized in the inner shelf off Victoria Land showed high retention in the region south and along the Terra Nova Bay polynya, with timescales consistent with development times of crystal krill. These results suggest that the cyclonic circulation over the shelf contributes significantly to the dispersion and retention of crystal krill in parts of the inner Ross Sea continental shelf that overlaps with regions with high concentrations of krill-dependent top predators. The westward circulation along the shelf break contributes to the transport and aggregation of Antarctic krill in regions where Circumpolar Deep Water is observed on the outer continental shelf and along the shelf break. The transport pathways and connectivity obtained from this study provide a baseline for assessing the effects of projected changes in the Ross Sea circulation on the distribution of two important krill species.