Among various approaches that have been employed to determine the transport pathways of plankton in the ocean, the use of drifters is particularly appealing. Miller [1976] designed a programmable vertically-migrating parachute drogue to mimic the vertical migration of the pteropod, Limacina inflata, in order to evaluate the effects of vertical migration on community structure in the presence of sheared current flow. This approach has some drawbacks--since mechanical devices cannot accurately reproduce either the behavior of individuals of a species (which may not be known well) or the effect of ocean currents--but such studies do provide useful insights into dispersal processes of different species in a flow regime. ``Patch following'' studies are growing increasingly appealing with the appearance of sophisticated new instruments, such as biologically-instrumented RAFOS floats [ Hitchcock et al., 1993].
A number of studies have modelled the dispersal of zooplankton. In general, these have modified models of the physical dynamics of the ocean in order to allow the seeding of particles that behave like the planktonic species of interest. This approach has considerable appeal, since it makes use of fundamental knowledge of physical processes in the ocean as well as any available information on the plankters' swimming behavior and vertical distribution. These studies may be particularly useful in generating testable hypotheses about patterns of dispersal of zooplankton. These studies may be particularly useful in complex flow fields. Examples of this approach include: a study of zooplankton transport in meanders of the Gulf Stream [ Flierl and Davis, 1993]; zooplankton transport in coastal filaments off the U.S. West Coast [ Hofmann et al., 1991]; physical and behavioral mechanisms of ichthyoplankton retention on Georges Bank [ Werner et al., 1993]; and a small-scale study of zooplankton behavior in turbulent flow [ Yamazaki and Haury, 1993]. One integrated biological/physical model of marine biogeographic processes has already considered population genetic data [ Olson and Hood, 1994]. Further incorporation of genetic data into coupled biological/physical oceanographic models may provide new insights into fundamental ocean processes.
Another effective method of studying zooplankton dispersal is to make extensive synoptic observations of as many oceanographic phenomena as possible. Such a ``shopping list'' approach has resulted in major advances in several regions. Notable among these is BioSynOP (Biological Synoptic Ocean Prediction), a focussed program on the movement of organisms in the meanders of the Gulf Stream. The field program involved intensive sampling and assessment of the biota by nets and acoustic devices [ Ashjian et al., 1994] and bio-optical instrumentation [ Hitchcock et al., 1993; Lohrenz et al., 1993] and was matched by an intensive study of the physical dynamics of the region, called SynOP. Another multidisciplinary program, the Coastal Transition Zone (CTZ) Program, effectively matched field observation to modelling of bio-physical processes in coastal filaments of the California Current [ Strub et al., 1991]. The filaments are intermittent, recurrent physical transport events that result in massive cross-shelf transport of coastal waters. Movement of zooplankton was followed by net samples [ Mackas et al., 1991], acoustic backscatter [ Pieper et al., 1990], and genetic tracers [ Bucklin et al., 1989].