05) at the same number of sampling stations (6 of 7) ( Figs. 5 and 6). For E. coli, cross-shore variable mortality models also had similar skill ( Fig. 5). That said, the ADGI model (including both cross-shore variable and solar-induced mortality)
performed slightly better than the other three, reproducing E. coli decay rates accurately (p < 0.05) at the greatest number of sampling stations (6 of 7) ( Fig. 6). The superior performance of cross-shore variable mortality models for both FIB groups at Huntington Beach highlights the need for further research regarding the spatial variability of FIB mortality in nearshore systems. Our data were insufficient to distinguish among the various cross-shore variable FIB mortality hypotheses www.selleckchem.com/products/azd9291.html we explored, and thus the mechanisms DAPT underlying this variability remain unknown. Given the superior performance of the ADGI model for E. coli, however, special attention should be paid to processes that cause cross-shore gradients of insolation,
such as turbidity. Field-based microcosm experiments could be useful in this regard. Based on the exponential FIB decay observed during our study our models focused on extra-enteric FIB mortality. FIB, however, have been reported to grow and/or undergo inactivation/repair cycles in aquatic systems (Boehm et al., 2009 and Surbeck et al., 2010). For this reason our estimated mortality rates are better interpreted as net rates, including some unknown combination of
mortality, inactivation, and growth. E. coli, for example, has been shown to exhibit elevated growth rates in highly turbulent flows ( Al-Homoud and Hondzo, 2008). Thus one interpretation of our cross-shore variable net mortality rates for E. coli (low in the surfzone and higher offshore) could be a relatively constant baseline mortality rate with some level of additional growth (lower net mortality) in the surfzone. Similarly, it is possible that some portion of the FIB loss we attribute to mortality (surfzone or offshore) is instead inactivation due to photodamage, and that some of these damaged FIB could undergo repair and recover. Fenbendazole This would make actual FIB mortality rates lower than those estimated from our models ( Boehm et al., 2009). More extensive experiments, monitoring a broader range of biological parameters, are required to piece together the processes contributing to the patterns in net FIB mortality revealed by our Huntington Beach FIB models. Although observed FIB decay has often been attributed to mortality alone, and can likewise be attributed to physical processes alone (e.g., the AD model), we have shown the importance of including both mortality and advection/diffusion in models predicting nearshore FIB concentrations.