In this context, numerous studies have highlighted the value of bivalves for
aquatic environment monitoring. These organisms are sedentary, have a high filtration rate and are characterised by their ability to accumulate environmental contaminants. For example, the use of bivalves revealed the contamination with pathogens,
while direct measurements on water samples were negative [56]. In addition,
oocysts of Cryptosporidium parvum have been detected in mussels (Mytilus
galloprovincialis) and cockles (Cerastoderma edule) from a shellfish-producing
region in Spain. The authors counted up to 5 Â 10
3 oocysts in the tissues of bivalves
[52]. The bioaccumulation of protozoa in bivalves is fairly well documented in
marine environments; in contrast, few studies have been conducted on continental
aquatic environments, despite their direct connections to pollutant sources
(e.g. discharge of effluents from water treatment plants, direct discharge of livestock
effluents, runoff or leaching from contaminated soil). The need for a better understanding of the protozoa ecology in freshwater ecosystems is increasingly
spotlighted. Therefore, particular interest was focused on the freshwater bivalve
Dreissena polymorpha (zebra mussel). Laboratory exposures have shown that
D. polymorpha was capable of (1) bioaccumulating cysts of G. duodenalis and
oocysts of C. parvum and T. gondii and (2) retaining T. gondii oocysts in its tissues
in amounts close to those found in tanks after 14 days of exposure [57, 58].
4.2 Occurrence of Pathogenic Parasites in the Seine River
In a previous study, Mons et al. [54] assessed the protozoan contamination in the
Seine River at sampling points located near the entry of drinking water plants (Ivry
and Orly) or farther downstream in Paris (Tolbiac, Alma, Garigliano) and its
periphery (Suresnes and Clichy). Cryptosporidium and Giardia were detected in
filtered water in 45% (67/149 samples) and 94% (140/149 samples) of samples,
respectively. Giardia was found more frequently and in larger quantities than
Cryptosporidium. Thus, downstream of Paris, maximum concentrations reached
245 Cryptosporidium oocysts 10 L
À1 and 512 Giardia cysts 10 L
À1 . These authors
suggested that protozoan contamination in the Seine River was not linked to urban
runoff but to land application of cattle manure and heavy rainfalls, which contribute
to protozoan runoff from contaminated soils. Thus, Cryptosporidium and Giardia
probably originate from rural areas, not from the Paris conurbation itself.
In this context, a field study was conducted within the PIREN-Seine programme,
to further investigate the occurrence and sources of pathogenic protozoa in the Seine
River using active biomonitoring with D. polymorpha. This field survey was carried
out on three sites along the Seine River, following an upstream–downstream gradient: Marnay-sur-Seine (rural site), Bougival and Triel-sur-Seine (urban sites) (see
[1]). Zebra mussels were collected in April 2016 at the Lac du Der-Chantecoq
(N 48
36
0 10.0728
00 E 4
44
0 57.408
00 ). Mussels measuring 2 Æ 0.2 cm were acclimated in the dark in mineral water at 12
C for 2 weeks with two water changes a
week to ensure that they were protozoan-free. Bivalves were caged in May 2016 for
368
P. Labadie et al.
aquatic environment monitoring. These organisms are sedentary, have a high filtration rate and are characterised by their ability to accumulate environmental contaminants. For example, the use of bivalves revealed the contamination with pathogens,
while direct measurements on water samples were negative [56]. In addition,
oocysts of Cryptosporidium parvum have been detected in mussels (Mytilus
galloprovincialis) and cockles (Cerastoderma edule) from a shellfish-producing
region in Spain. The authors counted up to 5 Â 10
3 oocysts in the tissues of bivalves
[52]. The bioaccumulation of protozoa in bivalves is fairly well documented in
marine environments; in contrast, few studies have been conducted on continental
aquatic environments, despite their direct connections to pollutant sources
(e.g. discharge of effluents from water treatment plants, direct discharge of livestock
effluents, runoff or leaching from contaminated soil). The need for a better understanding of the protozoa ecology in freshwater ecosystems is increasingly
spotlighted. Therefore, particular interest was focused on the freshwater bivalve
Dreissena polymorpha (zebra mussel). Laboratory exposures have shown that
D. polymorpha was capable of (1) bioaccumulating cysts of G. duodenalis and
oocysts of C. parvum and T. gondii and (2) retaining T. gondii oocysts in its tissues
in amounts close to those found in tanks after 14 days of exposure [57, 58].
4.2 Occurrence of Pathogenic Parasites in the Seine River
In a previous study, Mons et al. [54] assessed the protozoan contamination in the
Seine River at sampling points located near the entry of drinking water plants (Ivry
and Orly) or farther downstream in Paris (Tolbiac, Alma, Garigliano) and its
periphery (Suresnes and Clichy). Cryptosporidium and Giardia were detected in
filtered water in 45% (67/149 samples) and 94% (140/149 samples) of samples,
respectively. Giardia was found more frequently and in larger quantities than
Cryptosporidium. Thus, downstream of Paris, maximum concentrations reached
245 Cryptosporidium oocysts 10 L
À1 and 512 Giardia cysts 10 L
À1 . These authors
suggested that protozoan contamination in the Seine River was not linked to urban
runoff but to land application of cattle manure and heavy rainfalls, which contribute
to protozoan runoff from contaminated soils. Thus, Cryptosporidium and Giardia
probably originate from rural areas, not from the Paris conurbation itself.
In this context, a field study was conducted within the PIREN-Seine programme,
to further investigate the occurrence and sources of pathogenic protozoa in the Seine
River using active biomonitoring with D. polymorpha. This field survey was carried
out on three sites along the Seine River, following an upstream–downstream gradient: Marnay-sur-Seine (rural site), Bougival and Triel-sur-Seine (urban sites) (see
[1]). Zebra mussels were collected in April 2016 at the Lac du Der-Chantecoq
(N 48
36
0 10.0728
00 E 4
44
0 57.408
00 ). Mussels measuring 2 Æ 0.2 cm were acclimated in the dark in mineral water at 12
C for 2 weeks with two water changes a
week to ensure that they were protozoan-free. Bivalves were caged in May 2016 for
368
P. Labadie et al.