Animal Waste, Water Quality and Human Health

Indicators, sanitary surveys and source attribution techniques 337the only significant relationship being a weak correlation between human-specificBacteroidales marker by conventional PCR and E. coli counts.A study in a large Oregon coastal watershed used presence/absence data onhuman and ruminant Bacteroidales (HF183, HF134, CF128, CF193) along withE. coli counts, water quality measurements and climatic data in order toelucidate temporal and spatial dynamics of the markers and locate specificsources of contamination (Shanks et al. 2006). This study demonstrated a strongstatistical linkage between ruminant host-specific markers, FIOs and associatedFIO loading to specific point and non-point sources of contamination on a persampling site basis (Bernhard & Field 2000b). A similar study in New Zealandutilized human and ruminant-specific markers to assess pollution sources in amixed urban and rural watershed (Kirs et al. 2008). Although some incompletespecificity of the Bacteroidales ruminant marker was noted in the New Zealandstudy, for example, cross-reactivity with marsupial and horse faeces, the PCRmethods proved useful to discriminate human from livestock pollution. Animportant observation made in several field studies is that source tracking dataare more reliable on high-flow samples, and/or when faecal contamination ishigh (Gourmelon et al. 2007, Stapleton et al. 2009). In addition, correlation ofsource tracking markers with FIO density is much stronger under theseconditions. This conclusion was supported by a modelling study which foundthat conditions of lower contamination “generated significantly greater variance(17 per cent versus 1.7 per cent for qualitative analyses) and resulted inunderestimates for contributions from each host” (Leach et al. 2008).9.6 STUDY DESIGN – INCORPORATING A HOLISTICAPPROACHAdvantages and limitations to various FIOs, alternative or secondary indicatorsand source attribution techniques have been discussed in this Chapter. The useof site assessment methods in the form of sanitary surveys (USA), beach profiles(EU) or environmental health and safety surveys (Canada) as a means to targetmonitoring and remediation have also been introduced. An approach not solelybased on FIO levels would be able to take into account the source of thecontamination which may be identified through the use of sanitary inspections.Another consideration, other than the source of the contamination, is theinherent variability of bacterial density in water environments. Bacterialconcentrations may change abruptly both spatially and temporally makingmicrobial assessments based on a single grab sample invariably a snapshot ofwater quality captured at a single moment in time (Whitman et al. 2004b). The