Eutrophication, pollution and fragmentation: effects on parasite communities in roach (Rutilus rutilus) and perch (Perca fluviatilis) in four lakes in central Finland

Abstract

Parasite communities in four study lakes in 1986 reflected the influences of eutrophication, pollution, and habitat fragmentation. Discriminant analyses of communities at the individual host level revealed two major axes. One contrasted communities in a lake affected by chemical pollution from a pulp mill with those from two eutrophic, less polluted lakes. Changes in the density of intermediate hosts, direct effects on ectoparasites, and impaired immune systems were regarded as important mechanisms. The second contrasted communities in an oligotrophic, unpolluted lake with those from the two eutrophic lakes and was more complex, reflecting habitat fragmentation (the absence of glochidia and some digeneans) and pollution or eutrophication, probably mediated by the same mechanisms as above. Changes in some index parasites in Lake Vatia monitored in 1994, following 8 years of reduced pollutant loading, supported our conclusion that parasite faunas in Lake Vatia in 1986 involved the effects of pollution.

Environmental Parasitology. Interactions between parasites and pollutants in the aquatic environment

“…A number of studies show that there exists an intimate interaction between environmental conditions and parasitism and that this association is highly vulnerable (e.g. Valtonen et al, 1997;Williams & MacKenzie, 2003). Apart from the fact that adverse environmental conditions such as water pollution might have deleterious effects on intermediate hosts of heteroxenous parasites and thus reduce parasite abundance, these substances might also have immunosuppressive effects leading to higher infection rates.…”

Variations saisonnières des indices épidémiologiques de trois monogènes parasites de <i>Sarotherodon melanotheron</i> (pisces : Cichlidae) dans le lac d’ayamé i (Côte d’Ivoire)

“…Les paramètres suivants employés par Bush et al, 1997 Valtonen et al (1997). Pour les intensités moyennes (IM), la classification adoptée est celle de Bilong-Bilong et Njiné (1998) : -IM < 10 : intensité moyenne très faible, -10 < IM 50 : intensité moyenne faible, -50 < IM 100 : intensité moyenne moyenne, -IM > 100 : intensité moyenne élevée.…”

The influence of multiple environmental stressors on susceptibility to parasites: An experimental determination with oysters

“…Alternatively, environmental stress may have a deleterious effect on parasites causing infection rate and intensity within host populations to decrease (Lafferty 1997). It has long been hypothesized that synergism of multiple environmental stressors has a greater impact on host-parasite dynamics than do single stressors (see Myers 1995;Lafferty and Kuris 1999), but there is little empirical evidence supporting this hypothesis (but see Valtonen et al 1997…”