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![]() Volume 21 (2002) |
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Abstract |
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Langzeituntersuchungen (1969–2002) zur Verbreitung
der Cladoceren auf den Niedersächsischen Sandinseln der
südlichen Nordsee, Deutschland Long-term studies (1969–2002) of the cladoceran
distribution on the sandy islands of the sourthern North Sea in Lower
Saxony, Germany Werner
Hollwedel From
1969 to 2002 the distribution of cladoceran species on ten islands in
the southern North Sea was investigated. A total of 50 species was
found. The small water bodies in the salt marsh have to be resettled
after salt water floods; Macrothrix hirsuticornis and Moina brachiata are two of the pioneer species in the
brackish water bodies. Most cladoceran species were found in permanent
and temporary dune waters. Some of them were caught only occasionally
and in low abundance. A characteristic species of dune waters is Scapholeberis rammneri, which was detected on eight
islands. A small group of cladoceran species inhabited concrete basins
containing drinking water for cattle and horses. The Hammersee on Juist
island, a shallow freshwater lake since a dyke had been built in 1928,
was inhabited by 35 species. Within the last decade the species number
decreased because of eutrophication and biotopes being filled up by
sedimentation. On islands with newly dug water bodies species numbers
increased.
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Editors |
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