Persistence of Fecal Source Tracking Markers Human Fecal-Associated Bacteroidales (HF183), Cross-Assembly Phage-like Marker (crAssphage), Pepper Mild Mottle Virus (PMMoV), and Tomato Brown Rugose Fruit Virus (ToBRFV) in Coastal Waters

Microbial source tracking (MST) methods can be used to identify human-associated fecal pollution and associated health risks in the environment. The choice of the MST marker can impact the interpretation of the presence of fecal pollution. In this study, we measured decay rate constants of fecal indicator Enterococcus and four genetic (HF183, crAssphage, pepper mild mottle virus (PMMoV), and tomato brown rugose fruit virus (ToBRFV)) human-associated MST markers in the coastal waters of Half Moon Bay, California. Dialysis bags containing ocean water were spiked with raw sewage and deployed at two depths (5 and 90 cm), which represented different solar irradiances for 14 days. Decay was modeled using Chick’s law. PMMoV had the smallest decay rate constants, whereas cultured Enterococcus had the highest decay rate constants. Decay rate constants for crAssphage and Enterococcus displayed significant differences between depths, suggesting sunlight-mediated photoinactivation is an important mechanism of inactivation for them. This is the first study to provide decay rate constants for ToBRFV in environmental waters (kobs = 0.15 day–1 at 5 cm, 0.17 day–1 at 90 cm). The results of this study can help inform the interpretation of human-associated markers for future MST work in coastal waters.