, 1992), and protistan grazing (Hartke et al., 2002). What is often absent from efforts to understand nearshore FIB persistence, however, are syntheses of physical and biological dynamics. Only a handful of studies have attempted to quantify the importance of different physical or biological processes in controlling the extent and intensity of FIB pollution in the surfzone (Boehm et al., 2005, Boehm et al., 2009 and Grant et al., 2001). Even fewer use models as vehicles to test hypotheses concerning the accuracy with which different combinations of mechanisms can reproduce actual FIB data (Boehm, 2003, Boehm et al., 2005 and Sanders et al., 2005). Here, we present a study designed

specifically for this purpose. Data were acquired during a 5-h field program at Huntington Beach, CA, on October 16th, 2006, that monitored nearshore FIB concentrations, AZD6244 cost waves,

and currents. In this manuscript we explore the role of biological dynamics (in this case mortality) in controlling the spatial and temporal variability of FIB at Huntington Beach. Six different mortality functions representing different FIB mortality mechanisms are added to an individual based model of FIB that contains alongshore advection and cross-shore variable horizontal diffusion (the AD model). These new mortality models, together with additional data CHIR-99021 manufacturer (Enterococcus species distribution and time dependent solar insolation dose observations), are used to evaluate hypotheses regarding FIB mortality mechanisms in the nearshore. The mortality mechanisms explored in this paper are: spatially and temporally constant mortality

(null hypothesis), spatially constant solar-induced mortality, stationary cross-shore mortality gradients, FIB source-dependent mortality, and two combinations of the above. Solar-induced mortality was explored because insolation is often posited as a dominant source of mortality for nearshore FIB, and has been suggested to affect FIB at Huntington Beach (Boehm et al., 2002 and Sinton et al., 2002). Cross-shore mortality gradients were examined because surfzone and offshore waters often have different dynamics, which can result in cross-shore gradients of properties affecting FIB mortality, like temperature, grazers and turbidity (Omand et al., 2011, Reniers et al., 2009 and Smith and Largier, 1995). Turbidity gradients, in particular, can affect Anacetrapib the penetration of solar insolation, which, if FIB are solar sensitive, may result in cross-shore variable FIB mortality gradients that the organisms move through as they are advected and diffused across shore (Alkan et al., 1995 and Whitman et al., 2004). One of our two combination mortality functions includes both cross-shore mortality gradients and solar sensitivity to depict this particular mortality mechanism. Lastly, source-specific FIB mortality was examined because FIB from different sources can have different mortality rates (Sinton et al.