An error frequently made in the evaluation of advective transport in two-dimensional Lagrangian models of advection-diffusion in coral reef waters

The flushing time of reef lagoons estimated over recent years by 2-dimensional Lagrangian algorithms may have been significantly overestimated. This is due to a numerical artefact, leading to spurious accumulation of particles in regions where the water depth or the diffusivity is smallest. The nature of this numerical problem has remained largely unknown in the coral reef modelling community, although it was described, along with an efficient remedy, in several studies which are about a decade old. The numerical problem under consideration and its consequences on the modelled transport of coral eggs at Bowden Reef, Great Barrier Reef, are briefly assessed in the present article.