In contrast, the term “mortality” will be used to denote the portion of decay that is due to FIB senescence alone, and is not caused by the measured physical processes. At stations where FIB concentrations dropped below minimum sensitivity standards for our bacterial assays (<10 MPN/100 ml for E. coli or <2 CFU/100 ml for Enterococcus) prior to the end of the study period, decay rates

were calculated using only data up until these standards were reached ( SI Fig. 1). Decay rates were compared across sampling stations to look for spatial patterns in bacterial loss. Decay rates were also compared across FIB groups (E. coli vs. Enterococcus) selleck chemicals llc to identify group-specific patterns. Statistical analyses were performed using MATLAB (Mathworks, Natick, MA). Pressure sensors and Acoustic Doppler velocimeters (ADV’s) (Sontek, 2004), both

sampling at 8 Hz, were placed in the nearshore to monitor the wave and current field during our study. All instruments were mounted on tripod frames fixed on the seafloor at seven locations (F1–F7) along the shoreward-most 150 m of the cross-shore transect shown in (Fig 1.). Cross-shore resolved estimates of the alongshore current field were determined using 20 min averaged alongshore water velocities from each ADV. The contribution see more of physical processes in structuring FIB concentrations during HB06 was quantified using a 2D (x = alongshore, y = cross-shore) individual-based for advection–diffusion

or “AD” model for FIB (informed by the model of Tanaka and Franks, 2008). Only alongshore advection, assumed to be uniform alongshore, was included in the model. Both cross-shore and alongshore diffusivities were also included. These were assumed to be equal at any point in space, and alongshore uniform. The cross-shore variation of diffusivity was modeled as: equation(1) κh=κ0+(κ1-κ0)21-tanh(y-y0)yscaleHere κ0 is the background (offshore) diffusivity, κ1 is the elevated surfzone diffusivity ( Reniers et al., 2009 and Spydell et al., 2007), y0 is the observed cross-shore midpoint of the transition between κ0 and κ1 (i.e., the offshore edge of the surfzone) and yscale determines the cross-shore transition width. Representative values of κ1 (0.5 m2 s−1) and κ0 0.05 m2 s−1) were chosen based on incident wave height and alongshore current measurements ( Clark et al., 2010 and Spydell et al., 2009). The observed width of the surfzone (i.e., the region of breaking waves) was used to determine y0. Significant wave height was maximum at F4 and low at F1 and F2, suggesting that the offshore edge of the surfzone was between F2 and F4 ( Fig. 2a); thus y0 = 50 m, near F3. To give a rapid cross-shore transition between surfzone (F2) and offshore (F4) diffusivity, yscale was set to 5 m ( SI Fig. 2). The AD model was only weakly sensitive to the parameterization of yscale, κ0 and κ1, with sensitivity varying by station ( SI Fig. 3).