title: Fine-Scale Spatial Heterogeneity in the Distribution of Waterborne Protozoa in a Drinking Water Reservoir.
abstract: BACKGROUND
  The occurrence of faecal pathogens in drinking water resources constitutes a threat to the supply of safe drinking water, even in industrialized nations. To efficiently assess and monitor the risk posed by these pathogens, sampling deserves careful design, based on preliminary knowledge on their distribution dynamics in water. For the protozoan pathogens Cryptosporidium and Giardia, only little is known about their spatial distribution within drinking water supplies, especially at fine scale.
  
  
  METHODS
  Two-dimensional distribution maps were generated by sampling cross-sections at meter resolution in two different zones of a drinking water reservoir. Samples were analysed for protozoan pathogens as well as for E. coli, turbidity and physico-chemical parameters.
  
  
  RESULTS
  Parasites displayed heterogeneous distribution patterns, as reflected by significant (oo)cyst density gradients along reservoir depth. Spatial correlations between parasites and E. coli were observed near the reservoir inlet but were absent in the downstream lacustrine zone. Measurements of surface and subsurface flow velocities suggest a role of local hydrodynamics on these spatial patterns.
  
  
  CONCLUSIONS
  This fine-scale spatial study emphasizes the importance of sampling design (site, depth and position on the reservoir) for the acquisition of representative parasite data and for optimization of microbial risk assessment and monitoring. Such spatial information should prove useful to the modelling of pathogen transport dynamics in drinking water supplies.
authors.affiliation: Department of Environmental Research and Innovation (ERIN), Luxembourg Institute of Science and Technology, 41, rue du Brill, Belvaux L-4422, Luxembourg. jeanbaptiste.burnet@gmail.com.|Department of Environmental Sciences and Management, Université de Liège (ULg), 165 avenue de Longwy, Arlon B-6700, Belgium. jeanbaptiste.burnet@gmail.com.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Burnet
authors.affiliation: Department of Environmental Research and Innovation (ERIN), Luxembourg Institute of Science and Technology, 41, rue du Brill, Belvaux L-4422, Luxembourg. leslie.ogorzaly@list.lu.
authors.forename: Leslie
authors.initials: L
authors.lastname: Ogorzaly
authors.affiliation: Department of Environmental Research and Innovation (ERIN), Luxembourg Institute of Science and Technology, 41, rue du Brill, Belvaux L-4422, Luxembourg. christian.penny@list.lu.
authors.forename: Christian
authors.initials: C
authors.lastname: Penny
authors.affiliation: Department of Environmental Research and Innovation (ERIN), Luxembourg Institute of Science and Technology, 41, rue du Brill, Belvaux L-4422, Luxembourg. henry-michel.cauchie@list.lu.
authors.forename: Henry-Michel
authors.initials: HM
authors.lastname: Cauchie
mesh_terms: D003458:Cryptosporidium / Q000302:isolation & purification*; D060766:Drinking Water / Q000469:parasitology*; D004926:Escherichia coli / Q000302:isolation & purification*; D005872:Giardia / Q000302:isolation & purification*; D008189:Luxembourg; D018570:Risk Assessment; D060753:Water Quality; D062066:Water Resources
chemical_list: D060766:Drinking Water
keywords: Cryptosporidium; Giardia; microbial risk monitoring; reservoir; spatial distribution