The aquatic microbiota is known to be an important factor in the sustainability of the natural water ecosystems. However, the microbial community also might include pathogens, which result in very serious waterborne diseases in humans and animals. Faecal pollution is the major cause of these diseases. Therefore, it is of immense importance to assess the potential impact of faecal pollution, originating from both anthropogenic and zoogenic sources, on the profile of microbial communities in natural water environments. To this end, the microbial taxonomic diversity of lotic ecosystems in different regions of Norway, representing urban and rural areas, exposed to various levels of faecal pollution, was investigated over the course of a 1-year period. The highest microbial diversity was found in rural water that was the least faecally polluted, while the lowest was found in urban water with the highest faecal contamination. The overall diversity of the aquatic microbial community was significantly reduced in severely polluted water. In addition, the community compositions diverged between waters where the dominant pollution sources were of anthropogenic or zoogenic origin. The results provide new insight into the understanding of how faecal water contamination, specifically that of different origins, influences the microbial diversity of natural waters.

Fecal contamination of water constitutes a serious health risk to humans and environmental ecosystems. This is mainly due to the fact that fecal material carries a variety of enteropathogens, which can enter and circulate in water bodies through fecal pollution. In this respect, the prompt identification of the polluting source(s) is pivotal to guiding appropriate target-specific remediation actions. Notably, microbial source tracking (MST) is widely applied to determine the host origin(s) contributing to fecal water pollution through the identification of zoogenic and/or anthropogenic sources of fecal environmental DNA (eDNA). A wide array of host-associated molecular markers have been developed and exploited for polluting source attribution in various aquatic ecosystems. This review is intended to provide the most up-to-date overview of genetic marker-based MST studies carried out in different water types, such as freshwaters (including surface and groundwaters) and seawaters (from coasts, beaches, lagoons, and estuaries), as well as drinking water systems. Focusing on the latest scientific progress/achievements, this work aims to gain updated knowledge on the applicability and robustness of using MST for water quality surveillance. Moreover, it also provides a future perspective on advancing MST applications for environmental research.

During June 2019, an outbreak of campylobacteriosis occurred in Askøy, an island northwest of Bergen, Norway. According to the publicly available records, over 2000 residents fell ill and 76 were hospitalised, and two deaths were suspected to be associated with Campylobacter infection. By investigating the epidemic pattern and scope, an old caved drinking water holding pool was identified that had been faecally contaminated as indicated by the presence of Escherichia coli (E. coli). Furthermore, Campylobacter bacteria were found at several points in the water distribution system. In the escalated water health crisis, tracking down the infectious source became pivotal for the local municipality in order to take prompt and appropriate action to control the epidemic. A major task was to identify the primary faecal pollution source, which could further assist in tracking down the epidemic origin. Water from the affected pool was analysed using quantitative microbial source tracking (QMST) applying host-specific Bacteroidales 16S rRNA genetic markers. In addition, Campylobacter jejuni, Enterococcus faecalis, Clostridium perfringens and Shiga toxin-producing E. coli were detected. The QMST outcomes revealed that non-human (zoogenic) sources accounted predominantly for faecal pollution. More precisely, 69% of the faecal water contamination originated from horses.