[beachnet] new article on sunlight inactivation of traditional and novel indicators in marine waters

 http://pubs.acs.org/doi/abs/10.1021/es9015124
Covariation and Photoinactivation of Traditional and Novel Indicator 
Organisms and Human Viruses at a Sewage-Impacted Marine Beach
Alexandria B. Boehm Kevan M. Yamahara, David C. Love, Britt M. Peterson, 
Kristopher McNeill and Kara L. Nelson
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es9015124

Sunlight modulates concentrations of Escherichia coli and enterococci in 
marine waters. However, the mechanism of photoinactivation is poorly 
understood. Additionally, little is known about photoinactivation of other 
fecal indicators and human viruses in recreational waters. We sampled 
nearshore waters at Avalon Beach, California hourly for 72 h for reactive 
oxygen species (ROS), traditional indicator bacteria (E. coli and 
enterococci, and QPCR-based detection of enterococci), F+ (DNA and RNA) 
and somatic coliphages, the human-specific marker in Bacteroidales (HF 
marker), human enterovirus, and human adenovirus. E. coli and enterococci 
(regardless of measurement technique) covaried with each other and the 
coliphages suggesting similar sources and fates. The occurrence of the HF 
and enterovirus markers was correlated, but their occurrence was not 
positively correlated with the other indicators. Lower concentrations or 
occurrence of all microbes, excluding the HF and enterovirus markers, were 
observed during sunlit as opposed to dark hours, pointing to the 
importance of photoinactivation. Empirical-deterministic models for a 
subset of microbial indicators were created to determine field-relevant 
sunlight inactivation rates while accounting for time dependent sources 
and sinks. Photoinactivation rates of enterococci and E. coli, enterococci 
measured by QPCR, and somatic coliphage were estimated at 7, 6, 3, and 28 
d?1 I?1, respectively, where I is UVB intensity in W/m2. Average H2O2 
was 183 nM and the maximum singlet oxygen steady state concentration was 
6.6 fM. Given the clarity of the water, direct genomic damage of bacteria 
and coliphage, as well as indirect endogenous damage of bacteria, were 
likely the most important inactivation mechanisms, but we cannot rule out 
a contribution by indirect mechanisms involving the H2O2 and singlet 
oxygen produced exogenously.








Meredith B. Nevers
Research Ecologist
USGS Lake Michigan Ecological Research Station
1100 N. Mineral Springs Rd., Porter, IN 46304
phone (219) 926-8336  ext. 425   fax (219) 929-5792
mnevers at usgs.gov
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