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

Abstract

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.

Marine parasites as pollution indicators: an update

“…He then explored the potential response of parasites of aquatic animals to climate change. Kesting & Zander (2000) and Landsberg et al (1998) are good examples of interesting results obtained from community ecology studies and of investigations of the different effects of various pollutants.…”

“…From 1992 to 1994 Kesting & Zander (2000) examined 1245 fish of five species, 2850 gammarids of four species, 18 980 copepods of four species, and 1610 snails of three species in the Schlei Fjord of the Baltic Sea. Their main aims were to gain knowledge of the metazoan parasite communities of brackish water with varying degrees of salinity and to compare the results with other studies in the same area from 1977 to 1994, since it was known that a considerable increase in eutrophication had taken place during this 17 year period.…”

The biogeography of parasitism in sticklebacks: distance, habitat differences and the similarity in parasite occurrence and abundance

“…Another potential source of noise comes from the fact that the data were collected over a period spanning several decades, from the late 1950s to the present. Temporal changes in both the occurrences and particularly in the abundances of parasites from various localities might have resulted from environmental or climatic changes in aquatic habitats (Kesting and Zander 2000, Morley and Lewis 2007), potentially obscuring spatial patterns. Temporal turnover of species affects similarity among communities in many cases (Korhonen et al 2010), but not in the present study.…”

Beyond troubled waters: the influence of eutrophication on host–parasite interactions

“…Consequently, parasite species that are more tolerant to the disturbance are predicted to be favoured in the community. A number of studies along the German coast of the Baltic Sea hence reported eutrophication to favour generalist parasite species, parasites with direct development as well as parasites of planktonic hosts because of bottom hypoxia (Palm & Dobberstein ; Kesting & Zander ; Zander ; Zander & Reimer ). However, the theoretical foundation for the effects of eutrophication on parasites should be interpreted with caution as the definition of the different levels of eutrophication is very vague, which reduces our ability to build a general theoretical ground on this research, as previously pointed out by Johnson & Carpenter ().…”