[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 BeachAlexandria
B. Boehm Kevan M. Yamahara<http://pubs.acs.org/doi/abs/10.1021/es9015124#afn2>,
David C. Love, Britt M.
Peterson<http://pubs.acs.org/doi/abs/10.1021/es9015124#afn4>,
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.
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