Microbial impact of small tributaries on water and shellfish quality in shallow coastal areas

Abstract

This study aimed to investigate the impact of small tributaries on seawater and shellfish quality in coastal area subjected to brief episodes leading to fecal contamination. Escherichia coli and F-RNA-specific bacteriophages were selected as fecal indicators and astroviruses were chosen as being representative of pathogens in the human population during winter viral epidemics. A two-dimensional hydrodynamic model was built to simulate the current and dispersion in the model domain, which includes areas uncovered at low tide. The model also includes decay rates to simulate microorganism behavior and assess the influence of fecal input on shellfish quality. The originality lies in the fact that specific features of the study area were considered. Modeling results indicate limited particle movements and long flushing times at the back of the bay, where shellfish are farmed. Computational results showed that under normal conditions, i.e. 94% of the time, when rainfall was less than 10 mm per day, the sector shows acceptable water quality. These results are in agreement with shellfish concentration measured in the field. Under high flow conditions, high concentrations of fecal indicators and astrovirus were measured in the river and tributaries. The corresponding fluxes were over 50 times higher than under normal weather conditions. The location of the shellfish beds near the coast makes them vulnerable and fecal indicators and viruses were detected in shellfish after short rainfall events. Our modeling approach makes a contribution to shellfish management and consumer protection, by indicating the "risk period" as defined by EU regulations. Molecular development such as viral quantification in conjunction with model developments will help to prevent shellfish contamination and thus provide safer products to consumers and an effective tool for shellfish producers.

Using Remote Sensing to Identify Changes in Land Use and Sources of Fecal Bacteria to Support a Watershed Transport Model

“…The EFDC was used to model the bay and major tributaries, while the HSPF was used to model the watersheds. Similar to Riou et al [7], the study highlighted the influence of high flow conditions on fecal bacteria contamination. Two flow conditions-a dry weather and wet weather scenario-were modelled, with the latter exerting a greater stress on fecal coliform levels.…”

“…Riou et al [7] investigated the contributions of fecal bacteria from small tributaries of a coastal area and their impact on shellfish quality. Their findings stressed the importance of the relationship between fecal pollution and high rainfall events.…”

“…Their findings stressed the importance of the relationship between fecal pollution and high rainfall events. Following rainfall events and subsequent high flow conditions, fluxes in E. coli were 50 times higher than under normal weather conditions [7]. Kelsey et al [8] developed a predictive model of bacterial contamination of shellfish using remote sensing precipitation data along with additional environmental and climatic data.…”

Water quality, pollutant loads, and multivariate analysis of the effects of sewage discharges into urban streams of Southeast Brazil

“…Other researchers have reported increases of E.coli concentrations in small tributaries after rainfall events (Riou et al 2007;Galfi et al 2016), demonstrating the importance of studying the phenomena of pollutant transport from micro-basins, within the context of water resources. The mean E.coli load in the Recanto stream was 586 and 237% higher than in the Santa Angélica and Pylles streams, respectively.…”

A Three-Dimensional Hydro-Environmental Model of Dublin Bay

“…Depth-averaged hydro-environmental model have a wide range of applications (e.g. Kashefipour et al 2002Kashefipour et al , 2006Schnauder et al, 2007;Riou et al, 2007) due to their reasonable computational cost and the relative ease with which they can be set-up. However, in waters that exhibit considerable stratification in the vertical, as in Dublin Bay, a three-dimensional model is required and this study tests this hypothesis.…”