Settlement of marine organisms in flow

A feature common to many benthic marine plants and animals is the release of propagules that serve as the organism's only mechanism of dispersal. Successful dispersal depends to a large extent on the process of settlement-the transient phase between the pelagic life of the propagule and the benthic existence of the adult. The how of water may affect settlement on three levels: 1. Flow can act by exerting hydrodynamic forces on settling propagules. These forces may affect the propagule's encounter with the substratum, its behavior following encounter, or both. 2. Flow may provide a settlement cue that induces active behavior of motile propagules. 3. Flow may act to mediate various settlement cues (e.g. sediment load and the concentration of attractants). We discuss these three levels of flow effects as a means of examining the potential importance of flow in the settlement process, and then we explore the ecological consequences of settlement in different flow-regimes in light of the direct effects of how and flow-derived factors.