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Alteration of the Metazoan Parasite Faunas in the Brackish Schlei Fjord (Northern Germany, Baltic Sea)

2000; Wiley; Volume: 85; Issue: 2-3 Linguagem: Inglês

10.1002/(sici)1522-2632(200004)85

1522-2632

Verena Kesting, C. Dieter Zander,

Crustacean biology and ecology

Parasite communities of the inner and middle Schlei Fjord were investigated from 1992 to 1994. Host groups, comprising small-size or young fishes, benthic and planktonic crustaceans, and snails were taken from 4 localities (Selk, Haddeby, Borgwedel and Missunde) of differing salinities (1–8 ‰). The host and parasite fauna turned out to be very sparse, comprising 10 (Selk) to 16 (Missunde) host species of which only 7 and 9, respectively, harboured parasites. Parasites numbered 4 in Selk and 8 in Borgwedel and Missunde. Hysterothylacium sp. (Nematoda) was the only parasite present in all localities. High prevalences were attained by Proteocephalus percae (Cestoda) and Cryptocotyle concavum (Digenea) in Borgwedel and Missunde, whereas in Selk and Haddeby Caligus lacustris prevailed. With the exception of Cryptocotyle concavum intensities were mostly 1, and multiple infestations were rare. On the basis of comparisons with former investigations a faunal impoverishment can be stated during the course of 18 years in the inner Schlei Fjord. Increasing eutrophication causing deep mud layers on the bottoms as well as the ensuing high oxygen deficiencies even in the free water column during summer and autumn can be possible reasons for this phenomenon. As further consequence, the parasite spectrum was reduced to species which have simple developmental cycles and to species which prefer planktonic or suprabenthic, not benthic, hosts. The environment in Missunde with salinities of 6–8 ‰, can be designated as that described by Remane as an area of species minimum. In former times the parasite communities in Missunde were characterised by a species richness which was in contrast to the abundance of free living organisms.