Analysis of a parasite supra community from the Flensburg fjord.

Parasites from Flensburg fjord, northern German Baltic coast, were investigated under regard of the component, guild, and supra community level. At least, 28 host species of the guilds snails, planktonic and benthic crustaceans, and fish (exclusively small-sized species) were infected by 53 parasite species (28 autogenic and 19 allogenic ones, six of uncertain status). The sampling location was a shallow water with muddy sand bottom and rich vegetation, which is influenced by brackish conditions and strong eutrophication. The density of hosts was high but corresponds to values from other locations in the western Baltic. Prevalence and parasite density was low in snails and planktonic copepods but moderate in benthic crustaceans and often high in the fish guild due to the peculiarities of the single parasite species. Diversity of parasites was high in snails and most crustaceans on the component level, but mostly low in fish. In contrast, only snails attained high diversity on the guild level. Species identity of parasites in mud snail hosts (three Hydrobia spp.) was high, and therefore, they can substitute each other, whereas fish hosts present predominantly their own parasite fauna. At least, 17 developmental cycles of helminths were pursued in the guilds. The supra community is decisively influenced by the host species richness which render possible the diversity of guild communities. The characteristics of the parasite supra community from Flensburg fjord are marked by a random agglomeration of helminth species and their larval stages and some species of other parasite groups.