Larval transport and dispersal in the coastal ocean and consequences for population connectivity

Abstract

Many marine species have small, pelagic early life stages. For those species, knowledge of population connectivity requires understanding the origin and trajectories of dispersing eggs and larvae among subpopulations. Researchers have used various terms to describe the movement of eggs and larvae in the marine environment, including larval dispersal, dispersion, drift, export, retention, and larval transport. Though these terms are intuitive and relevant for understanding the spatial dynamics of populations, some may be nonoperational (i.e., not measurable), and the variety of descriptors and approaches used makes studies difficult to compare. Furthermore, the assumptions that underlie some of these concepts are rarely identified and tested. Here, we describe two phenomenologically relevant concepts, larval transport and larval dispersal. These concepts have corresponding operational definitions, are relevant to understanding population connectivity, and have a long history in the literature, although they are sometimes confused and used interchangeably. After defining and discussing larval transport and dispersal, we consider the relative importance of planktonic processes to the overall understanding and measurement of population connectivity. The ideas considered in this contribution are applicable to most benthic and pelagic species that undergo transformations among life stages. In this review, however, we focus on coastal and nearshore benthic invertebrates and fishes.