Impact of Intermittent Discharges on the Microbiological Quality of Shellfish

Reference: 07/WW/18/1
ISBN: 1 84057 438 0
Published Date: 09/05/2007

Laboratory and field investigations examined sewage effluent impact on microbiological shellfish hygiene parameters (faecal indicator organisms). Shellfish types examined were: wild mussels (Mytilus edulis) (all investigations) and Pacific oysters (Crassostrea gigas) (laboratory only).
The investigations demonstrated rapid uptake of organisms following contamination, producing flesh concentrations exceeding those recommended for human consumption (>46,000 Escherichia coli/100 g). Decay functions were fitted to subsequent depuration patterns.
In microcosms, mussels showed: (i) higher concentrations following contamination and (ii) more rapid depuration than oysters. Concentrations in flesh were correlated with those in overlying water (r>0.87). In the field, response was similar irrespective of overflow spill magnitude. Depuration was slower and statistical relationships between concentrations in shellfish and overlying water were weaker (r<0.66).

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