Lagrangian descriptions of marine larval dispersion

Abstract

Many marine organisms are sedentary as adults and are redistributed between genera- tions by the oceanic transport of planktonic larvae. In order to assess interactions among oceano- graphic 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 esti- mates 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 esti- mates, 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 dis- persal 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.