Detection and dynamics of fecal indicator bacteria in two Tyrrhenian lagoons (Sabaudia and Orbetello, central Italy)

Abstract

1 - Coastal lagoons are particularly vulnerable to strong anthropogenic pressure. These environments can act as sink for allochthonous material, including harmful bacteria, with the ability to reduce their impact to adjacent coastal waters. 2 - This study investigates fecal pollution impairment in two Italian coastal lagoons and adjacent coastal waters. We utilised methodological approaches to gain fast and more precise information on the contamination and viability of fecal indicator bacteria. 3 - The analyses of total coliforms (TC) and Escherichia coli (E. coli) were performed in situ by enzyme assays. E. coli live/dead cells were enumerated by immunofluorescence technique (combined with propidium iodide) for the specific detection of enteropathogenic serotypes (12 EPEC and 2 EIEC). 4 - Overall TC enzyme activity showed a high degree of temporal variation whereas E. coli enzyme activity peaked in summer in both lagoons (beta-glucuronidase, 84 and 47 nmol MUFL-1h-1, Sabaudia and Orbetello respectively). Beta-glucuronidase activity showed a high correlation with viable cells counts of E. coli enteropathogenic strains (p<0.01). Significantly lower degree of contamination was observed in the adjacent coastal waters. 5 - Our findings describe these lagoons as very fragile systems which hydro-morphological features allow a long time preservation of microbial contaminants, including pathogenic serotypes. These findings imply potential consequences for the human health as well as the need for protective measures of these environments.