Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 4 2 2007 10.5194/bg-4-173-2007 http://www.biogeosciences.net/4/173/2007/ http://www.biogeosciences.net/4/173/2007/bg-4-173-2007.html http://www.biogeosciences.net/4/173/2007/bg-4-173-2007.pdf 173 179 2007-03-02 Small-scale spatial structure in plankton distributions A. Tzella a.tzella@damtp.cam.ac.uk P. H. Haynes Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK The observed filamental nature of plankton populations suggests that stirring plays an important role in determining their spatial structure. If diffusive mixing is neglected, the various interacting biological species within a fluid parcel are determined by the parcel time history. The induced spatial structure has been shown to be a result of competition between the time evolution of the biological processes involved and the stirring induced by the flow as measured, for example, by the rate of divergence of the distance of neighbouring fluid parcels. In the work presented here we examine a simple biological model based on delay-differential equations, previously seen in Abraham (1998), including nutrients, phytoplankton and zooplankton, coupled to a strain flow. Previous theoretical investigations made on a differential equation model (Hernández-Garcia et al., 2002) imply that the latter two should share the same small-scale structure. The generalisation from differential equations to delay-differential equations, associated with the addition of a maturation time to the zooplankton growth, should not make a difference, provided sufficiently small spatial scales are considered. 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