MODELING INTERACTIONS OF BROWSING PREDATION, INFAUNAL ACTIVITY, AND RECRUITMENT IN MARINE SOFT-SEDIMENT HABITATS

In marine soft-sediment habitats, the sediment surface is altered by a ctivities of sediment dwellers (infauna). Such biogenic disturbance ca n influence recruitment success if settling larvae and juveniles avoid disturbed sites or if juveniles die as a result of disturbance after settling. Because infauna commonly lose exposed body parts to browsing predators and disturb less sediment as a result, we developed a simul ation model to examine the interactions between browsing predation, in faunal adult activity, and recruitment. Sediment disturbance in the mo del was based on data for the polychaete Abarenicola pacifica. We simu lated the activity of two general types of predators: prey nippers, wh ich damaged adults only, and sediment biters, which damaged adults and consumed settled juveniles. As both types of predation rates increase d, habitat rejection by settlers decreased, but juvenile mortality inc reased as settlers landing near damaged adults were killed when those adults resumed activity. When prey nippers were active, the interactio n between predation and infaunal activity determined recruitment succe ss, and juvenile mortality was highest at intermediate predation rates . When sediment biters were active, they controlled recruitment succes s by directly consuming larvae. At low adult worm densities, habitat r ejection by settlers and juvenile mortality were both low, and browsin g predation did not affect recruitment success. At higher adult densit ies, net recruitment success increased with the rate of predation by p rey nippers (the magnitude of increase depended on bite rate and the l ength of time juveniles were susceptible to mortality), but it was nev er enhanced by sediment biters.