title: Abundance and Distribution of Enteric Bacteria and Viruses in Coastal and Estuarine Sediments-a Review.
abstract: The long term survival of fecal indicator organisms (FIOs) and human pathogenic microorganisms in sediments is important from a water quality, human health and ecological perspective. Typically, both bacteria and viruses strongly associate with particulate matter present in freshwater, estuarine and marine environments. This association tends to be stronger in finer textured sediments and is strongly influenced by the type and quantity of clay minerals and organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the environment by offering physical and chemical protection from biotic and abiotic stresses. How bacterial and viral viability and pathogenicity is influenced by surface attachment requires further study. Typically, long-term association with surfaces including sediments induces bacteria to enter a viable-but-non-culturable (VBNC) state. Inherent methodological challenges of quantifying VBNC bacteria may lead to the frequent under-reporting of their abundance in sediments. The implications of this in a quantitative risk assessment context remain unclear. Similarly, sediments can harbor significant amounts of enteric viruses, however, the factors regulating their persistence remains poorly understood. Quantification of viruses in sediment remains problematic due to our poor ability to recover intact viral particles from sediment surfaces (typically <10%), our inability to distinguish between infective and damaged (non-infective) viral particles, aggregation of viral particles, and inhibition during qPCR. This suggests that the true viral titre in sediments may be being vastly underestimated. In turn, this is limiting our ability to understand the fate and transport of viruses in sediments. Model systems (e.g., human cell culture) are also lacking for some key viruses, preventing our ability to evaluate the infectivity of viruses recovered from sediments (e.g., norovirus). The release of particle-bound bacteria and viruses into the water column during sediment resuspension also represents a risk to water quality. In conclusion, our poor process level understanding of viral/bacterial-sediment interactions combined with methodological challenges is limiting the accurate source apportionment and quantitative microbial risk assessment for pathogenic organisms associated with sediments in aquatic environments.
authors.affiliation: School of Ocean Sciences, Bangor University Bangor, UK.
authors.forename: Francis
authors.initials: F
authors.lastname: Hassard
authors.affiliation: Department of Engineering and Innovation, Open University Milton Keynes, UK.
authors.forename: Ceri L
authors.initials: CL
authors.lastname: Gwyther
authors.affiliation: School of Environment, Natural Resources and Geography, Bangor University Bangor, UK.
authors.forename: Kata
authors.initials: K
authors.lastname: Farkas
authors.affiliation: UK Water Industry Research Limited London, UK.
authors.forename: Anthony
authors.initials: A
authors.lastname: Andrews
authors.affiliation: Atkins Limited Bristol, UK.
authors.forename: Vera
authors.initials: V
authors.lastname: Jones
authors.affiliation: Atkins Limited Warrington, UK.
authors.forename: Brian
authors.initials: B
authors.lastname: Cox
authors.affiliation: Thames Water Utilities Reading, UK.
authors.forename: Howard
authors.initials: H
authors.lastname: Brett
authors.affiliation: School of Environment, Natural Resources and Geography, Bangor University Bangor, UK.
authors.forename: Davey L
authors.initials: DL
authors.lastname: Jones
authors.affiliation: School of Biological Sciences, Bangor University Bangor, UK.
authors.forename: James E
authors.initials: JE
authors.lastname: McDonald
authors.affiliation: School of Ocean Sciences, Bangor University Bangor, UK.
authors.forename: Shelagh K
authors.initials: SK
authors.lastname: Malham
keywords: biofilm; fecal indicator organisms; resuspension; sediment; survival; viable but non-culturable bacteria; virus