Despite the diverse array of HAB species and the many hydrographic regimes in which they occur, one common characteristic of such phenomena is that physical oceanographic forcings play a significant role in both bloom dynamics and the patterns of toxicity or adverse impacts. Furthermore, the interplay or coupling between the physics and biological ``behavior,'' such as swimming, vertical migration, or physiological adaptation, holds the key for understanding many HAB phenomena. This physical/biological coupling can occur at both large and small scales.