Temperate shelf water dispersal by Australian boundary currents: Implications for population connectivity

Abstract

Boundary currents have been recognized as potential causes of spatial variation in the ocean because of their role in physical transport. In this study we used particle tracking methods in an ocean circulation model to determine the effect of multiple boundary currents on connectivity around temperate Australia during the austral winter. Our results demonstrated that oceanographic connectivity was asymmetric around Australia, having greater eastward connectivity due to more favorable ocean boundary currents during this season. We compared connectivity patterns with genetic data from an important marine species, the kelp, Ecklonia radiata , which have more genetic similarity between the west and south coasts of Australia, with the east coast, likely due to predominantly eastward dispersal in currents. Boundary current connectivity was linked to genetic connectivity of kelp on multigeneration time scales and the nature of these relationships varied among the three boundary current systems according to current strength. Boundary currents have been recognized as potential drivers of spatial heterogeneity in the ocean because of their role in physical transport and influence on large‐scale coastal processes. In this study, we used particle tracking methods in a data‐assimilating eddy‐resolving ocean circulation model to determine the effect of multiple boundary currents on connectivity around temperate Australia during the austral winter. Results demonstrated that oceanographic connectivity was asymmetric around Australia, having greater eastward trajectories due to more favorable ocean boundary currents during this season. We validated connectivity patterns with genetic data from an ecologically important species, the kelp, Ecklonia radiata , which has greater genetic similarity between the west and south coasts of Australia, compared with the east coast, likely due to predominantly eastward propagule dispersal. Boundary current circulation was a coarse predictor of kelp genetic connectivity on multigeneration time scales, and the nature of these relationships varied among the three boundary current systems according to mean current strength.