Marine parasites as pollution indicators: an update

Abstract

Eight major reviews are cited to indicate a recent knowledge explosion on the use of marine parasites as potential indicators of pollution. A literature update is given for the period 1995-2001. An analysis of the publications cited is used to provide 10 refined criteria for selecting parasites as indicator/monitor species. Previously unpublished data on Diclidophora merlangi and Dictyocotyle coeliaca confirm their value as potential indicators of hydrocarbon pollution in the North Sea. An extensive knowledge of D. merlangi is summarised to emphasize its potential value as an indicator species and also to encourage studies on the health status and immune responses of its host when subjected to pollutant stressors and infection with this monogenean. A discussion focuses on publications which have reported significant recent advances in this area of research and also on accompanying issues, problems and controversies. These selected publications are used to suggest species, stages in the development of species and assemblages of species worthy of further more detailed investigations into their value as indicators/monitors of pollution. It is predicted that further good progress will be made when contaminants can be accurately identified, their precise effects on both host and parasite can be measured by histochemical and biological methods and the roles of contaminants and parasites in causing disease can be assessed separately. About 100 references are cited.

Prevalence and Intensity of Helminth Parasites of African Catfish <i>Clarias gariepinus</i> in Lake Manzala, Egypt

“…However, parasitic infections are known to cause massive mortality in the fry and fingerling stages, especially in high-density aquaculture systems [23] [24]. In the present study, the high infection rate (65%) of C. gariepinus from Lake Manzala could therefore, be attributed to the contamination of the Lake by various pollutants and numerous tributaries coming from the River Nile.…”

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.…”

Diversity of metazoan parasites of the African catfish Clarias gariepinus (Burchell, 1822) as indicators of pollution in a subtropical African river system

“…The species composition of parasite communities is clearly impacted by environmental stress, and species richness tends to decrease under degraded conditions. Numerous investigators have examined the effects of environmental stress on single species of parasites in temperate aquatic systems (Khan & Thulin, 1991;Overstreet, 1993;MacKenzie et al, 1995;Williams & Mackenzie, 2003;Marcogliese, 2004;Sures, 2004), despite the fact that it is difficult to predict the direction of effects of pollution impacts on parasite communities. Most studies document changes in some aspect of the parasite fauna, and it is clear that pollution has effects on parasite populations and communities and is, however, often associated with a reduction in species richness of parasites (Marcogliese, 2004).…”