SETTLEMENT OF MARINE ORGANISMS IN FLOW

A feature common to many benthic marine plants and animals is the rele ase of propagules that serve as the organism's only mechanism of dispe rsal. Successful dispersal depends to a large extent on the process of settlement-the transient phase between the pelagic life of the propag ule and the benthic existence of the adult. The how of water may affec t 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 behavio r of motile propagules. 3. Flow may act to mediate various settlement cues (e.g. sediment load and the concentration of attractants). We dis cuss these three levels of flow effects as a means of examining the po tential importance of flow in the settlement process, and then we expl ore the ecological consequences of settlement in different flow-regime s in light of the direct effects of how and flow-derived factors.