Sink or swim, accumulation of biomass at fronts

Abstract

The dense concentrat~ons of blomass colnmonly seen at fronts are often explalned by a phys~olog~cal response of the oiganlsms to the frontal environment However, some fractlon of the enhanced b ~o m a s s may be explalned through purely phys~cal processes the interaction of floating sinking or swlmmlng w ~t h the flows at a front To explore this hypothesis, I present a model of steady, 2-dlmenslonal cross-frontal circulat~ons, whlch I combine ~1 1 t h a vanety of swlrnming behaviors The models show how patchmess may arise at fronts through retention and accumulat~on zones, and the patterns which evolve glven vanous flow and swimmlng characterlst~cs The ecological slgnlficance of the results 1s discussed up and W,,, can be found: C Biological concentration field CO Initial concentration field h Vertlcal scale of flow k Parameter controlling strength and direction of flow R Horizontal scale of flow t Time to Initial time u b Biological horizontal velocity U, Physical horizontal velocity us Horizontal swimming velocity (=O) wb Biological vertical velocity W, Max~mal swimming speed W , Physical vertical velocity W, Swimming velocity X Horizontal coordinate z Vertical coordinate zo Depth at which swimming speed is min~murn or zero z, Vertical length scale of swimming function 0 Angle of front to surface $b Biological stream function q!r, Physical stream function