Colouring coral larvae for tracking local dispersal and settlement

Quantifying patterns of dispersal and settlement in marine benthic invertebrates is challenging, largely due the complexity of life-history traits, small sizes of larvae (<1mm), and potential for large-scale dispersal (>100 kilometres) in the marine environment. Here, we develop a novel method that allows for immediate differentiation and visual tracking of large numbers of coral larvae from dispersal to settlement. Neutral red and Nile blue stains were extremely effective in colouring larvae, with minimal impacts on survival and settlement following optimisation of incubation times and stain concentrations. The method provides a simple, rapid (<60 mins), low-cost tool to colour coral larvae that facilitates a wide range of de novo laboratory and field studies of larval behaviour and ecology with potential applications for conservation planning and understanding patterns of connectivity.