Lagrangian descriptions of marine larval dispersion

Many marine organisms are sedentary as adults and are redistributed between generations by the oceanic transport of planktonic larvae. In order to assess interactions among oceanographic and biological processes that determine larval dispersal patterns, we introduce a Lagrangian (or water-parcel-following) description of larval transport. This formalism is used to determine larval dispersal kernels (larval settlement probability distributions) for a range of ocean flows, planktonic larval durations and settlement pre-competency/competency periods. Paths of individual planktonic larval releases are modeled statistically and, by averaging over many individuals, ensemble estimates of larval dispersal are determined. Typical dispersal scales vary from a few km to >400 km. Modeled dispersal kernels are well explained using only a few readily available biological and oceanographic parameters, and derived dispersal scales agree well with population-genetic estimates, suggesting that the model has reasonable predictive power. An index for regional-scale self-seeding is presented, and is used as a tool to evaluate the efficiency of marine conservation areas. Finally, settlement patterns resulting from larval releases made over short times (days to months) should be comprised of a small number of discrete samples taken from the long-term averaged dispersal kernel. The resulting larval dispersal patterns will be quasi-random in both space and time, which will have important implications for the interpretation of settlement time series and the prediction of recruitment of sessile organisms.