Antarctic krill connectivity: a Lagrangian modeling framework to understand Southern Ocean population dynamics

Antarctic krill populations exhibit substantial interannual fluctuations with highly variable success in the survival of larvae to the juvenile stage. Understanding connectivity between spawning hotspots and the areas where larvae successfully develop into juvenile populations is essential for predicting population dynamics and informing fishery management, yet the drivers of krill connectivity variability across the Southern Ocean remain poorly quantified.

This project uses Lagrangian particle tracking simulations to investigate krill larval connectivity patterns over 30 years (1993-present) based on high-resolution ocean circulation model outputs. We release over a billion virtual larvae throughout the spawning season across known spawning grounds and track their drift to quantify: (1) the variability of natural connectivity  among populations, (2) how spawning timing influences dispersal success, and (3) which large-scale climate patterns (SAM, ENSO, ACC variability) drive strong versus weak connectivity years.

Network analysis identifies critical source populations that supply multiple recruitment areas and vulnerable sink populations dependent on external larval input. This connectivity baseline is essential for distinguishing natural fluctuations from climate-driven changes in future projections.

Results will inform the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) by revealing which populations require protection and identifying critical hubs that sustain networks of connected krill populations. The Lagrangian model framework and open-source outputs will provide a foundation for subsequent climate change projections examining how changes in Southern Ocean circulation may alter connectivity patterns by 2050-2100.